Microbiol Res, 2004, 159(4), 425 - 37 In silico analysis of nonribosomal peptide synthetases of Xanthomonas axonopodis pv . citri: identification of putative siderophore and lipopeptide biosynthetic genes; Etchegaray A et al.; The genomes of the plant pathogens Xanthomonas axonopodis (Xac) and Xanthomonas campestris (Xcc) were analysed with the aim of deducing their ability to produce nonribosomal peptides . Nonribosomal peptide synthetase (NRPS) genes were identified in two separate loci of Xac . While the genes of locus 1 are common to both strains, locus 2 was only found in Xac . Dissection and phylogenetic analysis of the condensation and thioesterase domains of the NRPSs of loci 1 and 2 of Xac revealed homology, respectively, with siderophore and lipopeptide synthetases . Further analysis of locus 1 revealed genes related to polyketide and polyamine biosynthesis that could be involved in the assembly of substrates for siderophore biosynthesis in both strains . In vitro production of siderophores by both Xac and Xcc was confirmed . Since bacterial siderophores and lipopeptides can be pathogenic and are typically produced nonribosomally, these results suggest that the identified genes could be involved in phytotoxin production. Microbiol Res, 2004, 159(4), 419 - 23 Sensitive and specific detection of Xanthomonas campestris pv campestris by PCR using species-specific primers based on hrpF gene sequences; Park YJ et al.; A sensitive and specific assay was developed to detect bacterial black rot of crucifers caused by Xanthomonas campestris pv . campestris (X . c . pv . campestris), in cabbage seed and plant . Primers XCF and XCR from hrpF homologous to nolX, host recognition protein, were used to amplify a 525 bp DNA fragment . PCR technique was applied to detect the pathogen in naturally infected seed and plant of cabbage . The PCR product was only produced from X . c . pv . campestris among 40 isolates of Xanthomonas strains, Escherichia coli (O157:H7), Pectobacterium carotovorum subsp . carotovorum, and other reference bacteria. Res Microbiol, 2005 Jan-Feb, 156(1), 30 - 4 Protection of Xanthomonas against arsenic toxicity involves the peroxide-sensing transcription regulator OxyR; Sukchawalit R et al.; Arsenic has been shown to mediate its toxicity through induced generation of reactive oxygen species . Here, we examined the role of oxidative stress-inducible genes (katA, ahpC and ohr) and their regulators (oxyR and ohrR) in the response to arsenic treatment in a plant pathogenic bacterium, Xanthomonas campestris pv . phaseoli (Xp) . Overproduction of peroxide-scavenging enzymes (KatA, AhpCF and Ohr) did not enhance arsenic tolerance in wild-type Xp . Furthermore, inactivation of katA, ahpC, ohr, and ohrR genes had no effect on the level of arsenic resistance . By contrast, an oxyR mutant (Xp oxyR) showed increased sensitivity to both pentavalent arsenate and, to a greater extent, trivalent arsenite . The resistance of cells to arsenite treatment was significantly affected by the level of iron . Cells were 10-fold more sensitive to arsenite killing in the presence of excess iron, while removal of iron by an iron chelator (2,2'-dipyridyl) protected Xanthomonas from arsenite toxicity . The arsenite-sensitive phenotype of Xp oxyR could be complemented by the expression of functional OxyR from a plasmid vector, but not by the expression of other known OxyR-regulated peroxide-scavenging enzymes such as KatA and AhpCF, Ohr and OhrR . The data suggested that as yet unidentified, OxyR-regulated gene(s) are involved in conferring arsenic resistance in Xp . To our knowledge, this is the first report showing that the peroxide-sensing regulator OxyR is involved in arsenic resistance. Protein J, 2004 Oct, 23(7), 437 - 44 Purification and characterization of a lectin from Crotalaria paulina seeds; Pando LA et al.; A lectin was purified from Crotalaria paulina seeds by ion-exchange and FPLC molecular exclusion chromatography . CrpL had an apparent molecular mass of 30 kDa, as determined by SDS-PAGE under non-reducing and reducing conditions . CrpL effectively agglutinated human and cow erythrocytes, and this activity was not affected by 20 mM EDTA, showing no dependence of divalent cations . Hemagglutination was inhibited by N-acetyl-D-galactosamine, D-galactose and was also inhibited by glycoproteins, fetuin and asialofetuin . The N-terminal amino acid sequence of CrpL was identical to those of other lectins from the genus Crotalaria, and amino acid composition showed high amounts of Asx and Glx, and was rich in Gly, Ala and Ser, as also reported for lectins from other Crotalaria species . CrpL inhibited the growth of Xanthomonas axonopodis pv . phaseoli and Xanthomonas axonopodis pv . passiflorae, suggesting a role of this lectin in the defense of seeds against bacterial infections. Plant Mol Biol, 2004 Nov, 56(4), 573 - 584 Recent progress in the characterization of molecular determinants in the Xanthomonas axonopodis pv . manihotis-cassava interaction; Verdier V et al.; Cassava bacterial blight, caused by Xanthomonas axonopodis pv . manihotis (Xam), is a widespread disease that affects cassava (Manihot esculenta Crantz) . Studies on the pathogen population structure, pathogen diagnosis, identification and expression of plant genes involved in resistance have been carried out . Different molecular techniques were developed to assess the genetic diversity among the Xampopulations . Characterization of Xam population dynamics over time had enable us to determine the different factors that are associated with resistance breakdown and those that influence the genetic structure or virulence phenotypes of the pathogen's population . Methods for detecting the pathogen in vegetative planting materials and true seeds were developed and contributed to reduce the impact of the disease . To better understand the genetics of resistance a quantitative trait loci (QTLs) approach was developed . Using a PCR-based strategy with degenerate primers we isolated two resistance gene candidates in cassava . We also characterized a region of a chromosome rich in R-gene like sequence . In this review we also report the main results obtained by transcript profiling methodologies, cDNA-AFLP and ESTs developed by the authors to characterize the genes involved in disease resistance . All together these techniques allowed the identification of molecular markers either associated to CBB resistance or that may represent putative genes involved in disease resistance . This article reviews current knowledge on the molecular cassava-Xam interactions. Plant Mol Biol, 2004 Nov, 56(4), 541 - 54 A unigene catalogue of 5700 expressed genes in cassava; Lopez C et al.; Two economically important characters, starch content and cassava bacterial blight resistance, were targeted to generate a large collection of cassava ESTs . Two libraries were constructed from cassava root tissues of varieties with high and low starch contents . Other libraries were constructed from plant tissues challenged by the pathogen Xanthomonas axonopodis pv.manihotis . We report here the single pass sequencing of 11 954 cDNA clones from the 5' ends, including 111 from the 3' ends . Cluster analysis permitted the identification of a unigene set of 5700 sequences . Sequence analyses permitted the assignment of a putative functional category for 37% of sequences whereas ~ 16% sequences did not show any significant similarity with other proteins present in the database and therefore can be considered as cassava specific genes . A group of genes belonging to a large multigene family was identified . We characterize a set of genes detected only in infected libraries putatively involved in the defense response to pathogen infection . By comparing two libraries obtained from cultivars contrasting in their starch content a group of genes associated to starch biosynthesis and differentially expressed was identified . This is the first large cassava EST resource developed today and publicly available thus making a significant contribution to genomic knowledge of cassava. J Bacteriol, 2005 Jan, 187(2), 649 - 63 The hrpK Operon of Pseudomonas syringae pv . tomato DC3000 Encodes Two Proteins Secreted by the Type III (Hrp) Protein Secretion System: HopB1 and HrpK, a Putative Type III Translocator; Petnicki-Ocwieja T et al.; Pseudomonas syringae is a gram-negative bacterial plant pathogen that is dependent on a type III protein secretion system (TTSS) and the effector proteins it translocates into plant cells for pathogenicity . The P . syringae TTSS is encoded by hrp-hrc genes that reside in a central region of a pathogenicity island (Pai) . Flanking one side of this Pai is the exchangeable effector locus (EEL) . We characterized the transcriptional expression of the open reading frames (ORFs) within the EEL of P . syringae pv . tomato DC3000 . One of these ORFs, PSPTO1406 (hopB1) is expressed in the same transcriptional unit as hrpK . Both HopB1 and HrpK were secreted in culture and translocated into plant cells via the TTSS . However, the translocation of HrpK required its C-terminal half . HrpK shares low similarity with a putative translocator, HrpF, from Xanthomonas campestris pv . vesicatoria . DC3000 mutants lacking HrpK were significantly reduced in disease symptoms and multiplication in planta, whereas DC3000 hopB1 mutants produced phenotypes similar to the wild type . Additionally, hrpK mutants were reduced in their ability to elicit the hypersensitive response (HR), a programmed cell death associated with plant defense . The reduced HR phenotype exhibited by hrpK mutants was complemented by hrpK expressed in bacteria but not by HrpK transgenically expressed in tobacco, suggesting that HrpK does not function inside plant cells . Further experiments identified a C-terminal transmembrane domain within HrpK that is required for HrpK translocation . Taken together, HopB1 is a type III effector and HrpK plays an important role in the TTSS and is a putative type III translocator. Sci China C Life Sci, 2004 Oct, 47(5), 461 - 9 Genetic diversity of harpins from Xanthomonas oryzae and their activity to induce hypersensitive response and disease resistance in tobacco; Li P et al.; Three hrfA (hypersensitive response-functioning faction A) homologues (hrfl, hrf2 and hrf3) are cloned from 12 strains of Xanthomonas oryzae using PCR based techniques . Hrf1, hrf2 and hrf3 are derived from strains belonging to X . o . pv . oryzae, X . o . pv . oryzicola and X . o . pv . oryzae respectively . Sequence analysis shows that all three genes encode glycine-rich proteins with various numbers of GGG-GG motifs . They all share a conserved cysteine residue at position 45 or 47 . Hrf1 and hrf3 encode Harpin(xoo) while hrf2 encodes Harpin(xooc) Hrf1 and hrf3 encodes two different types of Harpin(xoo) proteins . Hrf1 from X . o . pv . oryzae strains (JxoIII, JxoIV, Jxov, Pxo61, Pxo76, Pxo79, Pxo99, Pxo99 and Pxo124) encodes a 15.6 kD Harpin(xoo) with 3 GGG-GG motifs while Hrf3 from strain Pxo86 and Pxo112 encodes a 15.9 kD Harpin(xoo) with 4 GGG-GG motifs . Harpin(xooc) encoded by hrf2 from X . o . pv . oryzicola (strain RS105) has the molecular weight of 15.3 kD and contains 2 GGG-GG motifs . Cluster analysis is performed using deduced sequences of hrf1, hrf2 and hrf3 as well as previously reported Hpa1 and Xopl protein sequence . The results indicated that Harpin(xoo) and Harpin(xooc) belong to two closely related subgroups . Hrf, hrf2 and hrf3 are expressed in E . coli strain BL21 successfully . Under the same condition, hrf1, hrf2 and hrf3 are expressed at the level of 0.389, 0.530 and 0.083 mg/mL respectively . All expressed hrf1, hrf2 and hrf3 proteins (Harpins) are shown to be able to induce hypersensitive reaction and TMV resistance on tobacco . Among the three proteins, Hrf2 has the highest activity while Hrf3 has the lowest activity. Proteomics . 2004 Dec 23; {Epub ahead of print} Comprehensive analysis of the extracellular proteins from Xanthomonas campestris pv . campestris B100; Watt SA et al.; The extracellular proteome of Xanthomonas campestris pv . campestris (Xcc) cultivated in minimal medium was isolated from the cell-free culture supernatant and separated by two-dimensional gel electrophoresis . This technique resolved 97 clearly visible protein spots, which were excised, digested with trypsin and identified on the basis of their peptide mass fingerprints generated by matrix assisted laser desorption/ionisation-time of flight-mass spectrometry . Using this approach 87 different proteins could be distinguished . The Signal P software predicted putative signal peptides for 53% of the extracellular proteins . These proteins are probably transported over the inner membrane and are localized in the periplasm, the outer membrane or secreted into the extracellular space . Among the secreted proteins are 11 degradative enzymes, which are involved in pathogenesis of Xcc . The proteins without obvious secretion signals are known to serve functions in the cytosol . How the cytosolic proteins are delivered to the extracellular space remains unclear. Syst Appl Microbiol, 2004 Nov, 27(6), 755 - 62 Reclassification of the xanthomonads associated with bacterial spot disease of tomato and pepper; Jones JB et al.; Four phenotypic xanthomonad groups have been identified that are pathogenic to pepper, tomato, or both hosts . These include groups A and C which are found in Xanthomonas axonopodis pv . vesicatoria, group B found in X . vesicatoria, and group D found in 'X . gardneri' . We present DNA:DNA hybridization data in which X . axonopodis pv . vesicatoria group A and C strains have less than 70% DNA relatedness with each other, with the type strain of X . axonopodis, and with the currently classified species within Xanthomonas and, therefore, should be removed from this species and given species status . We present information that the A strains most closely resemble the strains originally isolated by Doidge in 1921 . In an attempt to avoid confusion in nomenclature as stated in Principle 1 of the Bacteriological Code, we propose that the A strains of X . axonopodis pv . vesicatoria be renamed as X . euvesicatoria (ATCC11633T= NCPPB2968T = ICMP 109T = ICMP 98T) . Use of the euvesicatoria epithet should be reserved for strains originally identified by Doidge, which she designated Bacterium vesicatorium (Ann . Appl . Biol . 7: 407-430, 1921) in the original description when she referred to those strains as being feebly amylolytic . The name X . perforans sp . nov . is proposed for the C group of strains previously designated as X . axonopodis pv . vesicatoria (ATCC BAA-983T = NCPPB 4321T) . We also propose that 'X . gardneri', which has less than 70% DNA relatedness with any of the Xanthomonas species and which has never had taxonomic status, be named X . gardneri (ATCC 19865T = NCPPB 881T) to reflect the specific epithet proposed by Sutic in 1957. Plant Mol Biol, 2004 Aug, 55(6), 883 - 904 CAZFP1, Cys2/His2-type zinc-finger transcription factor gene functions as a pathogen-induced early-defense gene in Capsicum annuum; Kim SH et al.; A pepper zinc-finger protein gene, CAZFP1 , encoding the Cys2/His2-type zinc-finger transcription factor was isolated from pepper leaves inoculated with an avirulent strain Bv5-4a of Xanthomonas campestris pv . vesicatoria . The CAZFP1 protein is a nuclear targeting protein, which functions as a transcriptional regulator . The full-length CAZFP1 had no transcriptional activation activity, whereas the C-terminal region of CAZFP1 had transactivation activity . The CAZFP1 transcripts were constitutively expressed in the pepper stem, root, flower and red fruit, but were not detectable in the leaf and green fruit . The CAZFP1 transcripts accumulated earlier than the CAZFP1 (PR-1) gene in the incompatible interaction of the pepper leaves with X . campestris pv . vesicatoria . The CAZFP1 transcripts were significantly induced in the systemic, uninoculated leaf tissues early after inoculation with bacterial pathogens, but gradually declined thereafter . The CAZFP1 transcripts were localized, and confined to the phloem cells of the vascular bundle in the pepper leaf midrib in response to Colletotrichum . coccodes infection, ethylene and abscisic acid . The CAZFP1 gene was also induced much earlier by abiotic elicitors and environmental stresses, compared with the CAZFP1 gene . Overexpression of the CAZFP1 gene in the transgenic Arabidopsis plants enhanced not only the resistance against infection by Pseudomonas syringae pv . tomato, but also the drought tolerance . These results suggest that the CAZFP1 gene functions as an early-defense gene to enhance disease resistance and drought tolerance. Zhi Wu Sheng Li Yu Fen Zi Sheng Wu Xue Xue Bao, 2004 Jun, 30(3), 331 - 8 {Physiological and genetic analysis of lesion resembling disease mutants (lrd) of Oryza sativa L.}; Wang JJ et al.; Ten indica rice and eight japonica rice mutants with lesion resembling disease (lrd27-44) were obtained by gamma-ray mutagenesis of the whole genomes . These mutants exhibited diverse lesion mimic phenotypes under different growth environments, could be accordingly classified two types, sensitive and insensitive to environments . Basing on difference in development of lesion mimics, they can be divided into three categories: whole life lesion mimics (WLLM), vegetative initiation lesion mimics (VILM), and reproductive initiation lesion mimics (RILM) . Lesion mimics resulted from the programmed cell death and were triggered by light, but not by wounding . The genetic analysis showed that four mutants, lrd32, lrd39, lrd40 and lrd42, were controlled by one or two recessive loci . Among the 18 lrd mutants, lrd37 and lrd40 conferred non-race-specific resistance to Xanthomonas oryzae pv . oryzae . Gene mapping and cloning of Lrd32 and Lrd40 are under way. Mol Plant Microbe Interact, 2004 Dec, 17(12), 1348 - 54 The rice bacterial blight resistance gene xa5 encodes a novel form of disease resistance; Lyer AS et al.; The rice xa5 gene for disease resistance to Xanthomonas oryzae pv . oryzae has been positionally cloned and encodes the gamma subunit of transcription factor IIA (TFIIAgamma) . TFIIAgamma is a general eukaryotic transcription factor with no previously known role in disease resistance . xa5 is unusual in that it is recessive and does not conform to one of the typical resistance gene structural classes . Sequencing of TFIIAgamma in resistant and susceptible isolines revealed two nucleotide substitutions resulting in an amino acid change between resistant and susceptible cultivars . This association was conserved across 27 resistant and nine susceptible rice lines in the Aus-Boro group. J Biol Chem . 2004 Dec 7; {Epub ahead of print} Associations of the major pseudopilin XpsG with XpsN (GspC) and secretin XpsD of Xanthomonas campestris pv . campestris type II secretion apparatus revealed by crossling analysis; Lee MS et al.; The major pseudopilin XpsG is an essential component of type II secretion apparatus of Xanthomonas campestris pv . campestris . Along with other ancillary pseudopilins, it forms a pilus-like structure spanning between cytoplasmic and outer membranes . Associations of pseudopilins with non-pseudopilin members of type II secretion apparatus were not well documented, probably due to their dynamic or unstable nature . In this study, by treating intact cells with a cleavable cross-linker DSP, followed by metal chelating chromatography and immunoblotting on secretion-positive strains of X . campestris pv . campestris, we discovered associations of XpsGh with XpsN (GspC), as well as XpsD . These associations were detectable in a strain missing all components, but XpsO, of the type II secretion apparatus . However, chromosomal non-polar mutation in each gene exerted different effects upon the association between the other two . The XpsGh/XpsD association is undetectable in xpsN mutant, however restored to a limited extent by overproducing XpsD protein . The XpsGh/XpsN association is unaltered by a lack of XpsD protein or an elevation of its abundance . Co-immune precipitation between XpsN and XpsD, while being independent of XpsG, was nonetheless enhanced by raising XpsG protein level . These observations agree with the proposition that the type II secretion apparatus in a cell may exist as an integrated multiprotein complex with all components working in concert . Moreover, in functional machinery, the association of the major pseudopilin XpsG with secretin XpsD appears strongly dependent on the existence of XpsN, the GspC protein. Appl Environ Microbiol, 2004 Dec, 70(12), 7388 - 95 Novel type of heme-dependent oxygenase catalyzes oxidative cleavage of rubber (poly-cis-1,4-isoprene); Braaz R et al.; An extracellular protein with strong absorption at 406 nm was purified from cell-free culture fluid of latex-grown Xanthomonas sp . strain 35Y . This protein was identical to the gene product of a recently characterized gene cloned from Xanthomonas sp., as revealed by determination of m/z values and sequencing of selected isolated peptides obtained after trypsin fingerprint analysis . The purified protein degraded both natural rubber latex and chemosynthetic poly(cis-1,4-isoprene) in vitro by oxidative cleavage of the double bonds of poly(cis-1,4-isoprene) . 12-oxo-4,8-dimethyltrideca-4,8-diene-1-al (m/z 236) was identified and unequivocally characterized as the major cleavage product, and there was a homologous series of minor metabolites that differed from the major degradation product only in the number of repetitive isoprene units between terminal functions, CHO-CH2--and--H2-COCH3 . An in vitro enzyme assay for oxidative rubber degradation was developed based on high-performance liquid chromatography analysis and spectroscopic detection of product carbonyl functions after derivatization with dinitrophenylhydrazone . Enzymatic cleavage of rubber by the purified protein was strictly dependent on the presence of oxygen; it did not require addition of any soluble cofactors or metal ions and was optimal around pH 7.0 at 40 degrees C . Carbon monoxide and cyanide inhibited the reaction; addition of catalase had no effect, and peroxidase activity could not be detected . The purified protein was specific for natural rubber latex and chemosynthetic poly(cis-1,4-isoprene) . Analysis of the amino acid sequence deduced from the cloned gene (roxA {rubber oxygenase}) revealed the presence of two heme-binding motifs (CXXCH) for covalent attachment of heme to the protein . Spectroscopic analysis confirmed the presence of heme, and approximately 2 mol of heme per mol of RoxA was found. Appl Microbiol Biotechnol . 2004 Nov 24; {Epub ahead of print} Characterisation of a secondary alcohol dehydrogenase from Xanthomonas campestris DSM 3586; Salusjarvi T et al.; The chromosomal locus NP_636946 of Xanthomonas campestris DSM 3586 (ATCC 33913) which was earlier presumed to encode a quinoprotein glucose dehydrogenase has been cloned, expressed in Escherichia coli and the recombinant enzyme has been characterised . It was found to have no glucose dehydrogenase activity but to be active on many different polyols and diols, aliphatic alcohols, certain aldonic acids and amino-sugars . The product of d-gluconic acid oxidation was 5-keto- d-gluconic acid . The enzyme differs from polyol/gluconate dehydrogenases found in Gluconobacter by its single-chain architecture, different substrate specificity and much higher (20- to 30-fold) expression level in E.coli. Plant Cell Physiol, 2004 Oct, 45(10), 1537 - 42 Ornithine decarboxylase gene (CaODC1) is specifically induced during TMV-mediated but salicylate-independent resistant response in hot pepper; Yoo TH et al.; A gene encoding putative ornithine decarboxylase (ODC) has been isolated by differential screening of a cDNA library from the resistant hot pepper (Capsicum annuum L.) inoculated with avirulent tobacco mosaic virus (TMV) pathotype P0 . In hot pepper plants, transcripts of the CaODC1 (C . annuum ODC1) gene started to accumulate at 24 h post-inoculation of TMV-P0 and the signal was spread systemically . The transcript level of CaODC1 was increased rapidly in a hot pepper resistant to Xanthomonas campestris pv . vesicatoria (Xcv) but not in a susceptible hot pepper after inoculation . These results suggest possible role(s) for CaODC1 in plant defense against a broad range of pathogens including viruses and bacteria. Mol Plant Microbe Interact, 2004 Nov, 17(11), 1212 - 22 Identification and expression profiling of tomato genes differentially regulated during a resistance response to Xanthomonas campestris pv . vesicatoria; Gibly A et al.; The gram-negative bacterium Xanthomonas campestris pv . vesicatoria is the causal agent of spot disease in tomato and pepper . Plants of the tomato line Hawaii 7981 are resistant to race T3 of X . campestris pv . vesicatoria expressing the type III effector protein AvrXv3 and develop a typical hypersensitive response upon bacterial challenge . A combination of suppression subtractive hybridization and microarray analysis identified a large set of cDNAs that are induced or repressed during the resistance response of Hawaii 7981 plants to X . campestris pv . vesicatoria T3 bacteria . Sequence analysis of the isolated cDNAs revealed that they correspond to 426 nonredundant genes, which were designated as XRE (Xanthomonas-regulated) genes and were classified into more than 20 functional classes . The largest functional groups contain genes involved in defense, stress responses, protein synthesis, signaling, and photosynthesis . Analysis of XRE expression kinetics during the tomato resistance response to X . campestris pv . vesicatoria T3 revealed six clusters of genes with coordinate expression . In addition, by using isogenic X . campestris pv . vesicatoria T2 strains differing only by the avrXv3 avirulence gene, we found that 77% of the identified XRE genes were directly modulated by expression of the AvrXv3 effector protein . Interestingly, 64% of the XRE genes were also induced in tomato during an incompatible interaction with an avirulent strain of Pseudomonas syringae pv . tomato . The identification and expression analysis of X . campestris pv . vesicatoria T3-modulated genes, which may be involved in the control or in the execution of plant defense responses, set the stage for the dissection of signaling and cellular responses activated in tomato plants during the onset of spot disease resistance. Mol Plant Microbe Interact, 2004 Nov, 17(11), 1192 - 200 Diverse members of the AvrBs3/PthA family of type III effectors are major virulence determinants in bacterial blight disease of rice; Yang B et al.; AvrXa7 is a member of the avBs3/pthA gene family and the only known type III secretion system effector gene from Xanthomonas oryzae pv . oryzae with a major contribution to bacterial growth and lesion formation in bacterial blight disease of rice . We examined the general requirement for effectors of the AvrBs3/PthA family in bacterial blight of rice by identifying effectors from diverse strains of the pathogen . Inactivation of single effector genes in representative strains from Japan, Korea, and the Philippines resulted in severely limited growth in plants . Five strains harbored one gene of the avrBs3/pthA family, while one strain had two genes with the equivalent virulence activity of avrXa7 . Sequence analysis revealed three genes with unique repeat arrangements in comparison to avrXa7 . Comparison of the repetitive regions revealed a potential motif for the group that was also present in the repetitive region of avrBs3 . However, the repetitive region of avrBs3 could not support virulence activity but, in combination with the C-terminal coding region of avrXa7, triggered a Xa7-dependent avirulence reaction . The results revealed diverse members of the avrBs3/pthA gene family with virulence activity in X . oryzae pv . oryzae and supported the hypothesis that bacterial blight disease of rice is highly dependent on a single class of type III effectors . The results also indicated that avrXa7 avirulence specificity is separable from virulence activity. Proc Natl Acad Sci U S A, 2004 Nov 23, 101(47), 16624 - 9 Epub 2004 Nov 23. A genetic screen to isolate type III effectors translocated into pepper cells during Xanthomonas infection; Roden JA et al.; The bacterial pathogen Xanthomonas campestris pv . vesicatoria (Xcv) uses a type III secretion system (TTSS) to translocate effector proteins into host plant cells . The TTSS is required for Xcv colonization, yet the identity of many proteins translocated through this apparatus is not known . We used a genetic screen to functionally identify Xcv TTSS effectors . A transposon 5 (Tn5)-based transposon construct including the coding sequence for the Xcv AvrBs2 effector devoid of its TTSS signal was randomly inserted into the Xcv genome . Insertion of the avrBs2 reporter gene into Xcv genes coding for proteins containing a functional TTSS signal peptide resulted in the creation of chimeric TTSS effector::AvrBs2 fusion proteins . Xcv strains containing these fusions translocated the AvrBs2 reporter in a TTSS-dependent manner into resistant BS2 pepper cells during infection, activating the avrBs2-dependent hypersensitive response (HR) . We isolated seven chimeric fusion proteins and designated the identified TTSS effectors as Xanthomonas outer proteins (Xops) . Translocation of each Xop was confirmed by using the calmodulin-dependent adenylate cydase reporter assay . Three xop genes are Xanthomonas spp.-specific, whereas homologs for the rest are found in other phytopathogenic bacteria . XopF1 and XopF2 define an effector gene family in Xcv . XopN contains a eukaryotic protein fold repeat and is required for full Xcv pathogenicity in pepper and tomato . The translocated effectors identified in this work expand our knowledge of the diversity of proteins that Xcv uses to manipulate its hosts. Mol Microbiol, 2004 Nov, 54(3), 755 - 68 HpaB from Xanthomonas campestris pv . vesicatoria acts as an exit control protein in type III-dependent protein secretion; Buttner D et al.; The hrp (hypersensitive response and pathogenicity) gene cluster of the plant pathogenic bacterium Xanthomonas campestris pv . vesicatoria encodes a type III secretion (TTS) system, which injects bacterial effector proteins into the plant cell . Here, we characterized hpaB (hpa, hrp-associated), which encodes a pathogenicity factor with typical features of a TTS chaperone . We show that HpaB is important for the efficient secretion of at least five effector proteins but is dispensable for the secretion of non-effectors such as XopA and the TTS translocon protein HrpF . GST pull-down assays revealed that HpaB interacts with two unrelated effector proteins, AvrBs1 and AvrBs3, but not with XopA . The HpaB-binding site is located within the first 50 amino acids of AvrBs3 . This region also contains the targeting signal for HpaB-dependent secretion, which is missing in HrpF and XopA . Intriguingly, the N-termini of HrpF and XopA target the AvrBs3Delta2 reporter for translocation in a DeltahpaB mutant but not in the wild-type strain . This indicates that HpaB plays an essential role in the exit control of the TTS system . Our data suggest that HpaB promotes the secretion of a large set of effector proteins and prevents the delivery of non-effectors into the plant cell. BMC Microbiol . 2004 Oct 09;4(1):40. Variation suggestive of horizontal gene transfer at a lipopolysaccharide (lps) biosynthetic locus in Xanthomonas oryzae pv . oryzae, the bacterial leaf blight pathogen of rice; Patil PB et al.; BACKGROUND: In animal pathogenic bacteria, horizontal gene transfer events (HGT) have been frequently observed in genomic regions that encode functions involved in biosynthesis of the outer membrane located lipopolysaccharide (LPS) . As a result, different strains of the same pathogen can have substantially different lps biosynthetic gene clusters . Since LPS is highly antigenic, the variation at lps loci is attributed to be of advantage in evading the host immune system . Although LPS has been suggested as a potentiator of plant defense responses, interstrain variation at lps biosynthetic gene clusters has not been reported for any plant pathogenic bacterium . RESULTS: We report here the complete sequence of a 12.2 kb virulence locus of Xanthomonas oryzae pv . oryzae (Xoo) encoding six genes whose products are homologous to functions involved in LPS biosynthesis and transport . All six open reading frames (ORFs) have atypical G+C content and altered codon usage, which are the hallmarks of genomic islands that are acquired by horizontal gene transfer . The lps locus is flanked by highly conserved genes, metB and etfA, respectively encoding cystathionine gamma lyase and electron transport flavoprotein . Interestingly, two different sets of lps genes are present at this locus in the plant pathogens, Xanthomonas campestris pv . campestris (Xcc) and Xanthomonas axonopodis pv . citri (Xac) . The genomic island is present in a number of Xoo strains from India and other Asian countries but is not present in two strains, one from India (BXO8) and another from Nepal (Nepal624) as well as the closely related rice pathogen, Xanthomonas oryzae pv . oryzicola (Xoor) . TAIL-PCR analysis indicates that sequences related to Xac are present at the lps locus in both BXO8 and Nepal624 . The Xoor strain has a hybrid lps gene cluster, with sequences at the metB and etfA ends, being most closely related to sequences from Xac and the tomato pathogen, Pseudomonas syringae pv . tomato respectively . CONCLUSION: This is the first report of hypervariation at an lps locus between different strains of a plant pathogenic bacterium . Our results indicate that multiple HGT events have occurred at this locus in the xanthomonad group of plant pathogens. Yi Chuan Xue Bao, 2004 Jul, 31(7), 724 - 9 {Mapping of a new resistance gene to bacterial blight in rice line introgressed from Oryza officinalis}; Tan GX et al.; Rice line 'B5', which was derived from the wild rice Oryza officinalis Wall ex Watt through introgression, has been proved to be high resistant to brown planthopper, whitebacked planthopper and bacterial blight (Xanthomonas oryzae pv . oryzae) . In this study, the resistance to bacterial blight of 187 recombinant inbred lines (RILs) from a cross between ' B5' and 'Minghui63' were evaluated and RFLP markers linked to the resistance gene were identified by bulked segregant analysis . Analysis of the molecular marker linkage map and the data of the lesion length of RILs located the resistant gene within a 1 . 3 cM region flanked by RFLP markers C904 and R596 on chromosome 1 . This locus contributed to 52.96% of the phenotypic variance of resistance in the population, and is considered to be a new locus as compared with other resistant genes to bacterial blight that have been reported . We tentatively designate this gene as Xa29(t) . This newly tagged gene introgressed from wild rice is valuable to molecular marker-assisted selection for multiple resistant materials in rice breeding programme . Furthermore, it provides information for cloning the resistant gene Xa29(t) in rice. Prikl Biokhim Mikrobiol, 2004 Jul-Aug, 40(4), 435 - 41 {Hydrolysis of peptides by immobilized bacterial peptide hydrolases}; Nekliudov AD et al.; The feasibility of hydrolysis of a mixture of peptides with an enzyme from the bacterium Xanthomonas rubrilineans, displaying a peptidase activity and immobilized on aluminum oxide, was studied . Kinetic schemes and equations allowing for approaching quantitative description of peptide hydrolysis in complex mixtures containing free amino acids and peptides were obtained . It was demonstrated that as a result of hydrolysis, the content of free amino acids in hydrolysates decreased 2.5- to 3-fold and the molecular weight of the constituent peptides, 2-fold. Plant Physiol, 2004 Sep, 136(1), 2862 - 74 Epub 2004 Sep 03. The pepper transcription factor CaPF1 confers pathogen and freezing tolerance in Arabidopsis; Yi SY et al.; An ERF/AP2-type transcription factor (CaPF1) was isolated by differential-display reverse transcription-PCR, following inoculation of the soybean pustule pathogen Xanthomonas axonopodis pv glycines 8ra, which induces hypersensitive response in pepper (Capsicum annuum) leaves . CaPF1 mRNA was induced under conditions of biotic and abiotic stress . Higher levels of CaPF1 transcripts were observed in disease-resistant tissue compared with susceptible tissue . CaPF1 expression was additionally induced using various treatment regimes, including ethephon, methyl jasmonate, and cold stress . To determine the role of CaPF1 in plants, transgenic Arabidopsis and tobacco (Nicotiana tabacum) plants expressing higher levels of CaPF1 were generated . Gene expression analyses of transgenic Arabidopsis and tobacco revealed that the CaPF1 level in transgenic plants affects expression of genes that contain either a GCC or a CRT/DRE box in their promoter regions . Furthermore, transgenic Arabidopsis plants expressing CaPF1 displayed tolerance against freezing temperatures and enhanced resistance to Pseudomonas syringae pv tomato DC3000 . Disease tolerance was additionally observed in CaPF1 transgenic tobacco plants . The results collectively indicate that CaPF1 is an ERF/AP2 transcription factor in hot pepper plants that may play dual roles in response to biotic and abiotic stress in plants. DNA Seq, 2004 Apr, 15(2), 110 - 7 Cloning and characterization of a novel avirulence gene (arp3) from Xanthomonas oryzae pv . oryzae; Liang B et al.; A novel avirulence gene was cloned from Xanthomonas oryzae pv . oryzae strain PX0339, which is the standard representative of the Philippines race 9a . The full-length gene spans 2118 bp and encodes a protein of 705 amino acids . BLAST search in NCBI indicated that the gene belongs to avrBs3 gene family, and designated arp3 (AvrBs3-related protein 3, arp3) . The central region of the arp3 contains only 5.5 copies of 102bp repeats, the smallest copy number of repeats found in avrBs3 gene family by now . Together with the repeats is heptad repeats, resembling leucine zippers . Three functional nuclear localization signals and an acidic activation domain are also found in the C-terminal region . However, the arp3 lacks of two segments in its N-terminal region, which is unique in avrBs3 gene family . Southern blotting data showed that the arp3 is present as a single-copy in genomic DNA of PX0339 and locus in plasmid clone . The arp3 could be expressed in vitro in Escherichia coli BL21 and a 128kDa fusion protein was detected by Western analysis. J Bacteriol, 2004 Sep, 186(18), 6186 - 97 New protein-protein interactions identified for the regulatory and structural components and substrates of the type III Secretion system of the phytopathogen Xanthomonas axonopodis Pathovar citri; Alegria MC et al.; We have initiated a project to identify protein-protein interactions involved in the pathogenicity of the bacterial plant pathogen Xanthomonas axonopodis pv . citri . Using a yeast two-hybrid system based on Gal4 DNA-binding and activation domains, we have focused on identifying interactions involving subunits, regulators, and substrates of the type III secretion system coded by the hrp (for hypersensitive response and pathogenicity), hrc (for hrp conserved), and hpa (for hrp associated) genes . We have identified several previously uncharacterized interactions involving (i) HrpG, a two-component system response regulator responsible for the expression of X . axonopodis pv . citri hrp operons, and XAC0095, a previously uncharacterized protein encountered only in Xanthomonas spp.; (ii) HpaA, a protein secreted by the type III secretion system, HpaB, and the C-terminal domain of HrcV; (iii) HrpB1, HrpD6, and HrpW; and (iv) HrpB2 and HrcU . Homotropic interactions were also identified for the ATPase HrcN . These newly identified protein-protein interactions increase our understanding of the functional integration of phytopathogen-specific type III secretion system components and suggest new hypotheses regarding the molecular mechanisms underlying Xanthomonas pathogenicity. BMC Evol Biol . 2004 Aug 27;4(1):29. Different patterns of evolution for duplicated DNA repair genes in bacteria of the Xanthomonadales group; Martins-Pinheiro M et al.; BACKGROUND: DNA repair genes encode proteins that protect organisms against genetic damage generated by environmental agents and by-products of cell metabolism . The importance of these genes in life maintenance is supported by their high conservation, and the presence of duplications of such genes may be easily traced, especially in prokaryotic genomes . RESULTS: The genome sequences of two Xanthomonas species were used as the basis for phylogenetic analyses of genes related to DNA repair that were found duplicated . Although 16S rRNA phylogenetic analyses confirm their classification at the basis of the gamma proteobacteria subdivision, differences were found in the origin of the various genes investigated . Except for lexA, detected as a recent duplication, most of the genes in more than one copy are represented by two highly divergent orthologs . Basically, one of such duplications is frequently positioned close to other gamma proteobacteria, but the second is often positioned close to unrelated bacteria . These orthologs may have occurred from old duplication events, followed by extensive gene loss, or were originated from lateral gene transfer (LGT), as is the case of the uvrD homolog . CONCLUSIONS: Duplications of DNA repair related genes may result in redundancy and also improve the organisms' responses to environmental challenges . Most of such duplications, in Xanthomonas, seem to have arisen from old events and possibly enlarge both functional and evolutionary genome potentiality. Appl Biochem Biotechnol, 1999 Dec, 82(3), 175 - 84 Xanthan Gum Production by Xanthomonas campestris w.t . Fermentation from Chestnut Extract; Liakopoulou-Kyriakides M et al.; Xanthomonas campestris w.t . was used for production of xanthan gum in fermentations with chestnut flour for the first time . Fermentations were carried out with either chestnut flour or its soluble sugars (33.5%) and starch (53.6%), respectively, at 28 degrees C and 200 rpm at initial pH 7.0 in flasks . The effect of agitation rate (at 200, 400, and 600 rpm) on xanthan gum production was also studied in a 2-L batch reactor . It was found that xanthan production reaches a maximum value of 3.3 g/100 mL at 600 rpm and 28 degrees C at 45 h. Appl Biochem Biotechnol, 2004 Jul-Sep, 118(1-3), 305 - 12 Xanthan gum production from cassava bagasse hydrolysate with Xanthomonas campestris using alternative sources of nitrogen; Woiciechowski AL et al.; Cassava bagasse was hydrolyzed using HCl and the hydrolysate was used for the production of xanthan gum using a bacterial culture of Xanthomonas campestris . Cassava bagasse hydrolysate with an initial concentration of approx 20 g of glucose/L proved to be the best substrate concentration for xanthan gum production . Among the organic and inorganic nitrogen sources tested to supplement the medium-urea, yeast extract, peptone, potassium nitrate, and ammonium sulfate-potassium nitrate was most suitable . Ammonium sulfate was the least effective for xanthan gum production, and it affected sugar utilization by the bacterial culture . In media with an initial sugar concentration of 48.6 and 40.4 g/L, at the end of fermentation about 30 g/L of sugars was unused . Maximum xanthan gum (about 14 g/L) was produced when fermentation was carried out with a medium containing 19.8 g/L of initial reducing sugars supplemented with potassium nitrate and fermented for 72 h, and it remained almost the same until the end of fermentation (i.e., 96 h). Appl Environ Microbiol, 2004 Aug, 70(8), 4486 - 90 Bactericidal activity of glycinecin A, a bacteriocin derived from Xanthomonas campestris pv . glycines, on phytopathogenic Xanthomonas campestris pv . vesicatoria cells; Pham HT et al.; The ability of glycinecin A, a bacteriocin derived from Xanthomonas campestris pv . glycines 8ra, to kill closely related bacteria has been demonstrated previously by our group . In the present study, we aimed at determining the glycinecin A-induced cause of death . Treatment with glycinecin A caused slow dissipation of membrane potential and rapid depletion of the pH gradient . Glycinecin A treatment also induced leakage of potassium ions from X . campestris pv . vesicatoria YK93-4 cells and killed sensitive bacterial cells in a dose-dependent manner . Sensitive cells were killed within 2 h of incubation, most likely due to the potassium ion efflux caused by glycinecin A . These results suggest that the bactericidal mechanism of action of glycinecin A is correlated with the permeability of membranes to hydroxyl and potassium ions, leading to the lethal activity of the bacteriocin on the target bacteria. Annu Rev Phytopathol, 2004, 42, 385 - 414 Type III secretion system effector proteins: double agents in bacterial disease and plant defense; Alfano JR et al.; Many phytopathogenic bacteria inject virulence effector proteins into plant cells via a Hrp type III secretion system (TTSS) . Without the TTSS, these pathogens cannot defeat basal defenses, grow in plants, produce disease lesions in hosts, or elicit the hypersensitive response (HR) in nonhosts . Pathogen genome projects employing bioinformatic methods to identify TTSS Hrp regulon promoters and TTSS pathway targeting signals suggest that phytopathogenic Pseudomonas, Xanthomonas, and Ralstonia spp . harbor large arsenals of effectors . The Hrp TTSS employs customized cytoplasmic chaperones, conserved export components in the bacterial envelope (also used by the TTSS of animal pathogens), and a more specialized set of TTSS-secreted proteins to deliver effectors across the plant cell wall and plasma membrane . Many effectors can act as molecular double agents that betray the pathogen to plant defenses in some interactions and suppress host defenses in others . Investigations of the functions of effectors within plant cells have demonstrated the plasma membrane and nucleus as subcellular sites for several effectors, revealed some effectors to possess cysteine protease or protein tyrosine phosphatase activity, and provided new clues to the coevolution of bacterium-plant interactions. Annu Rev Phytopathol, 2004, 42, 163 - 84 Comparative genomics analyses of citrus-associated bacteria; Moreira LM et al.; Xylella fastidiosa 9a5c (XF-9a5c) and Xanthomonas axonopodis pv . citri (XAC) are bacteria that infect citrus plants . Sequencing of the genomes of these strains is complete and comparative analyses are now under way with the genomes of other bacteria of the same genera . In this review, we present an overview of this comparative genomic work . We also present a detailed genomic comparison between XF-9a5a and XAC . Based on this analysis, genes and operons were identified that might be relevant for adaptation to citrus . XAC has two copies of a type II secretion system, a large number of cell wall-degrading enzymes and sugar transporters, a complete energy metabolism, a whole set of avirulence genes associated with a type III secretion system, and a complete flagellar and chemotatic system . By contrast, XF-9a5c possesses more genes involved with type IV pili biosynthesis than does XAC, contains genes encoding for production of colicins, and has 4 copies of Type I restriction/modification system while XAC has only one. J Biol Chem, 2004 Oct 8, 279(41), 42462 - 8 Epub 2004 Jul 26. Evidence for a new sub-class of methionine sulfoxide reductases B with an alternative thioredoxin recognition signature; Neiers F et al.; Methionine sulfoxide reductases catalyze the reduction of protein-bound methionine sulfoxide back to methionine via a thioredoxin-recycling process . Two classes of methionine sulfoxide reductases, called MsrA and MsrB, exist that display opposite stereoselectivities toward the sulfoxide function . Although they are structurally unrelated, they share a similar chemical mechanism that includes three steps with 1) formation of a sulfenic acid intermediate with a concomitant release of 1 mol of methionine per mole of enzyme; 2) formation of an intradisulfide Msr bond; and 3) reduction of the oxidized Msr by thioredoxin . In the MsrBs that have been biochemically, enzymatically, and structurally characterized so far, the cysteine involved in the regeneration of the catalytic Cys-117 is Cys-63 . Cys-117 is located on a beta strand, whereas the recycling Cys-63 is on a loop near Cys-117 . The distance between the two cysteines is compatible with formation of the Cys-117/Cys-63 intradisulfide bond . Analyses of MsrB sequences show that at least 37% of the MsrBs do not possess the recycling Cys-63 . In the present study, it is shown that Cys-31 in the Xanthomonas campestris MsrB, which is located on another loop, can efficiently substitute for Cys-63 . Such a result implies flexibility of the MsrB structures, at least of the loops on which Cys-31 or Cys-63 are located . The fact that about 25% of the putative MsrBs have no recycling cysteine supports other recycling processes in which thioredoxin is not operative. Indian J Exp Biol, 2003 Jan, 41(1), 78 - 81 Effect of phenol on ultra structure and plasmid DNA of Xanthomonas oryzae pv . oryzae; Mohan N et al.; Most phenolic substances of plant origin are toxic to microorganisms and they confer some degree of protection to plants against phytopathogens . Xanthomonas oryzae pv . oryzae, bacterial blight pathogen of rice (Oryza sativa) was treated with phenol (monohydroxy benzene) and its effects on the morphology and cytological changes of the bacterium were studied . Total lysis of cells occurred with 5 mM conc of phenol while at 2 mM conc, the cell walls became rough and cell contents started shrinking . Plasmids isolated from both treated (2 mM) and control cells did not show any marked difference under electron microscope except that they differed in their quantity and might influence pathogenicity. J Appl Microbiol, 1998 Jan, 84(1), 115 - 24 Phenotypic diversity of Xanthomonas sp . mangiferaeindicae; Pruvost O et al.; Carbohydrate utilization profiles by means of the API (Appareils et Procedes d'Identification) system and sensitivity to antibiotics and heavy metal salts of 68 Xanthomonas sp . mangiferaeindicae strains isolated in nine countries from mango (Mangifera indica L.) and other genera of the Anacardiaceae were examined to assess the variability of the taxon . The strains could be separated into 10 groups according to Ward clustering . Apigmented strains isolated from the pepper tree {syn . Brazilian pepper} (Schinus terebenthifolius Raddi) could not be clearly differentiated from most apigmented strains isolated from mango . Yellow-pigmented strains isolated from mango in Brazil and Reunion Island, apigmented strains isolated from mango in Brazil and from ambarella in the French West Indies, clustered in distinct groups . The results are consistent with those of other studies, based on isozyme analysis of esterase, phosphoglucomutase and superoxide dismutase, and hrp-RFLP analysis; they indicate the need for a comprehensive taxonomic evaluation of xanthomonads associated with Anacardiaceae. Mol Plant Microbe Interact, 2004 Jul, 17(7), 805 - 15 Basal defenses induced in pepper by lipopolysaccharides are suppressed by Xanthomonas campestris pv . vesicatoria; Keshavarzi M et al.; The nonpathogenic hrcC mutant of Xanthomonas campestris pv . vesicatoria 85-10::hrpA22 multiplied in pepper leaves if it was mixed with pathogenic strains of X . campestris pv . vesicatoria . Reactions to the mutant alone included localized deposition of phenolics and callose in papillae, and alterations to the plant cell wall leading to increased electron density . Electron microscopy showed that the localized responses were suppressed in the presence of wild-type bacteria but other wall changes occurred at some sites, involving cellulose-rich ingrowth of the wall . Multiplication of the hrp mutant in mixed inocula was confirmed by tagging 85-10::hrpA22 using immunocytochemical location of AvrBs3 expressed from the plasmid pD36 . Elicitors of callose deposition and other wall changes were isolated from the hrcC mutant . Activity in extracts of bacteria was attributed to the presence of high molecular weight lipopolysaccharides (LPS) . Wild-type X . campestris pv . vesicatoria suppressed induction of structural changes caused by purified LPS . Results obtained suggest that effector proteins produced by phytopathogenic bacteria and delivered by the type III secretion system may have a key role in suppressing the basal defense responses activated by bacterial LPS, which lead to restricted multiplication of nonpathogens such as hrp mutants. Mol Plant Microbe Interact, 2004 Jul, 17(7), 771 - 9 The avrRxo1 gene from the rice pathogen Xanthomonas oryzae pv . oryzicola confers a nonhost defense reaction on maize with resistance gene Rxo1; Zhao B et al.; Maize lines that contain the single dominant gene Rxo1 exhibit a rapid hypersensitive response (HR) after infiltration with the rice bacterial streak pathogen Xanthomonas oryzae pv . oryzicola, but not with the rice bacterial blight pathogen X . oryzae pv . oryzae . The avirulence effector gene that corresponds to Rxo1, designated avrRxo1, was identified in an X . oryzae pv . oryzicola genomic library . When introduced into X . oryzae pv . oryzae, clones containing avrRxo1 induced an HR on maize with Rxo1, but not on maize without Rxo1 . The avrRxo1 gene is 1,266 bp long and shows no significant homology to any database sequences . When expressed in an X . oryzae pv . oryzae hrpC mutant that is deficient in the type III secretion system, avrRxo1 did not elicit the HR, indicating that the avrRxo1-Rxo1 interaction is dependent on type III secretion . Transient expression of avrRxo1 in onion cells after biolistic delivery revealed that the protein product was associated with the plasma membrane . Transient expression in maize lines carrying Rxo1 resulted in cell death, suggesting that AvrRxo1 functions from inside maize cells to elicit Rxo1-dependent pathogen recognition. J Microbiol Methods, 2004 Aug, 58(2), 281 - 4 A rapid and sensitive method for the detection of Xanthomonas fragariae, causal agent of angular leafspot disease in strawberry plants; Stoger A et al.; Angular leaf spot is a bacterial disease caused by Xanthomonas fragariae . It has become a serious disease in the USA and Europe in recent years . Several detection procedures are described for this plant pathogen . However, they are either too time-consuming, too insensitive or impractical when handling a large number of samples routinely . Here we describe a modified protocol of the REDExtract-N-Amp Plant PCR-Kit for the detection of X . fragariae in planta and demonstrate that it provides greater sensitivity, speed and high throughput potential than methods previously described. Mol Plant Microbe Interact, 2004 Jun, 17(6), 633 - 43 Characterization of the Xanthomonas AvrXv4 effector, a SUMO protease translocated into plant cells; Roden J et al.; Homologs of the Yersinia virulence factor YopJ are found in both animal and plant bacterial pathogens, as well as in plant symbionts . The conservation of this effector family indicates that several pathogens may use YopJ-like proteins to regulate bacteria-host interactions during infection . YopJ and YopJ-like proteins share structural homology with cysteine proteases and are hypothesized to functionally mimic small ubiquitin-like modifier (SUMO) proteases in eukaryotic cells . Strains of the phytopathogenic bacterium Xanthomonas campestris pv . vesicatoria are known to possess four YopJ-like proteins, AvrXv4, AvrBsT, AvrRxv, and XopJ . In this work, we have characterized AvrXv4 to determine if AvrXv4 functions like a SUMO protease in planta during Xanthomonas-plant interactions . We provide evidence that X . campestris pv . vesicatoria secretes and translocates the AvrXv4 protein into plant cells during infection in a type III-dependent manner . Once inside the plant cell, AvrXv4 is localized to the plant cytoplasm . By performing AvrXv4 deletion and mutational analysis, we have identified amino acids required for type III delivery and for host recognition . We show that AvrXv4 recognition by resistant plants requires a functional protease catalytic core, the domain that is conserved in all of the putative YopJ-like cysteine proteases . We also show that AvrXv4 expression in planta leads to a reduction in SUMO-modified proteins, demonstrating that AvrXv4 possesses SUMO isopeptidase activity . Overall, our studies reveal that the YopJ-like effector AvrXv4 encodes a type III SUMO protease effector that is active in the cytoplasmic compartment of plant cells. Mol Plant Microbe Interact, 2004 Jun, 17(6), 602 - 12 RaxH/RaxR: a two-component regulatory system in Xanthomonas oryzae pv . oryzae required for AvrXa21 activity; Burdman S et al.; Xanthomonas oryzae pv . oryzae is the causal agent of bacterial leaf blight, one of the most serious diseases in rice . X . oryzae pv . oryzae Philippine race 6 (PR6) strains are unable to establish infection in rice lines expressing the resistance gene Xa21 . Although the pathogen-associated molecule that triggers the Xa21-mediated defense response (AvrXa21) is unknown, six rax (required for AvrXa21 activity) genes encoding proteins involved in sulfur metabolism and Type I secretion were recently identified . Here, we report on the identification of two additional rax genes, raxR and raxH, which encode a response regulator and a histidine protein kinase of two-component regulatory systems, respectively . Null mutants of PR6 strain PXO99 that are impaired in either raxR, raxH, or both cause lesions significantly longer and grow to significantly higher levels than does the wild-type strain in Xa21-rice leaves . Both raxR and raxH mutants are complemented to wild-type levels of AvrXa21 activity by introduction of expression vectors carrying raxR and raxH, respectively . These null mutants do not affect AvrXa7 and AvrXa10 activities, as observed in inoculation experiments with Xa7- and Xa10-rice lines . Western blot and raxR/gfp promoter-reporter analyses confirmed RaxR expression in X . oryzae pv . oryzae . The results of promoter-reporter studies also suggest that the previously identified raxSTAB operon is a target for RaxH/RaxR regulation . Characterization of the RaxH/RaxR system provides new opportunities for understanding the specificity of the X . oryzae pv . oryzae-Xa21 interaction and may contribute to the identification of AvrXa21. Mol Plant Microbe Interact, 2004 Jun, 17(6), 593 - 601 Bacterial genes involved in type I secretion and sulfation are required to elicit the rice Xa21-mediated innate immune response; da Silva FG et al.; Innate immunity to microorganisms relies on the specific sensing of pathogen-associated molecules by host recognition receptors . Whereas studies in animals have largely focused on the recognition of extracellular pathogen-associated molecules by the TLR (toll-like receptor) superfamily, few studies have been carried out in plants, and it is not understood how these molecules are secreted or modified . The rice Xa21 gene encodes a receptor-like kinase that provides immunity against strains of the bacterial pathogen Xanthomonas oryzae pv . oryzae carrying AvrXa21 activity . We identified four X . oryzae pv . oryzae genes that are required for AvrXa21 activity . raxA, raxB, and raxC encode proteins with similarity to a membrane fusion protein, an ATP-binding cassette transporter, and an outer membrane protein, respectively, of bacterial type I secretion systems . The fourth gene, raxST, encodes a sulfotransferase-like protein . Sequence analysis of three naturally occurring X . oryzae pv . oryzae strains no longer recognized by Xa21 revealed alterations in the raxST and raxA genes . The raxC gene complemented an Escherichia coli tolC mutant for secretion of a double glycine-leader peptide confirming the function of raxC in type I secretion . These results indicate that bacterial type I secretion is necessary for Xa21-mediated recognition and immunity and further suggest that type I secretion and modification of pathogen-associated molecules play an important role in triggering the innate immune response in rice. Planta, 2004 Sep, 219(5), 797 - 806 Epub 2004 Jun 08. Molecular characterization of pepper germin-like protein as the novel PR-16 family of pathogenesis-related proteins isolated during the resistance response to viral and bacterial infection; Park CJ et al.; To understand the molecular defense mechanism controlling the hypersensitive response (HR) better, we examined the hot pepper plant (Capsicum annuum L . cv . Bugang), which exhibits an HR in response to infection by Tobacco mosaic virus pathotype P0 (TMV-P0) . A full-length cDNA clone was isolated by differential screening of a cDNA library that was constructed with mRNA extracted from hot pepper leaves during the resistance response to TMV-P0 . The predicted amino acid sequence of the cDNA clone exhibited a high sequence similarity to germin-like protein (GLP) . The CaGLP1 (Capsicum annuum GLP1) cDNA contains a single open reading frame of 660 bp encoding 220 amino acid residues . Upon inoculation with TMV or Xanthomonas, CaGLP1 transcripts were specifically accumulated in the incompatible interaction but not in the compatible interaction . In plants treated with salicylic acid (SA) or ethephon, which are signal molecules in the defense-related signal transduction pathway, CaGLP1 transcripts were accumulated rapidly . As far as we know, this is the first report that plant GLPs can be specifically induced during a defense response against viral infection . These data suggest that in the hot pepper plant CaGLP1 may be involved in the defense response to viral pathogens, and thus be classified as a new family of PR proteins, 'PR-16'. J Mol Microbiol Biotechnol, 2003, 6(3-4), 145 - 54 Molecular genetic analyses of potential beta-galactosidase genes in Xanthomonas campestris; Yang TC et al.; Xanthomonas campestris pv . campestris, which displays no significant beta-1,4-D-galactopyranosidase activity, has three annotated beta-galactosidase genes in the sequenced genome, designated galA, galB and galC herein . GalA and GalB are similar to glycosyl hydrolase (GH) family 2 enzymes, including Escherichia coli LacZ . galA and galB cannot express detectable activity even after being cloned in-frame and driven by the vector's promoter . GalC is a GH35 enzyme homologous to the Xanthomonas axonopodis pv . manihotis Bga . The latter cleaves beta,1-3-linked galactose 1,000 times faster than beta,1-4-linked galactose and is not responsible for lactose utilization . In X . campestris pv . campestris cells, GalC is readily detectable by Western blotting, and the levels can be increased by cloning the gene under the control of the vector's promoter . Results of insertional mutation, transcriptional fusion assay and Western blotting indicated that galC, clustered with several GH genes, is cotranscribed with the upstream gene(s) and is expressed constitutively . Xc17L is a previously isolated mutant with elevated beta-galactosidase activity and a greatly improved ability to grow on lactose . Results of DNA sequencing of Xc17L galA, galB and galC, enzyme assays of galA, galB and galC mutants derived from Xc17L, and Western blotting of GalC in Xc17L indicated that the three beta-galactosidase genes do not encode the elevated beta-galactosidase activity in Xc17L . The presence of a fourth beta-galactosidase gene is proposed . Plant Physiol, 2004 May, 135(1), 530 - 8 Epub 2004 May 07. The role of the jasmonate response in plant susceptibility to diverse pathogens with a range of lifestyles; Thaler JS et al.; Plants defend themselves against attack from insects and pathogens with various resistance strategies . The jasmonate and salicylate signaling pathways are two induced responses that protect plants against these attackers . Knowledge of the range of organisms that are affected by each response is important for understanding how plants coordinate their defenses against multiple attackers and the generality of effect of different resistance mechanisms . The jasmonate response is known to protect plants against a wide range of insect herbivores; in this study, we examined the role of the jasmonate response in susceptibility to eight pathogens with diverse lifestyles in the laboratory and field . Recent biochemical models suggest that the lifestyle of the pathogen (necrotroph versus biotroph) should predict whether the jasmonate response will be involved in resistance . We tested this by examining the susceptibility of wild-type (cv Castlemart with no known genes for resistance to the pathogens used) and jasmonate-deficient mutant tomato (Lycopersicon esculentum) plants (def1) and by employing rescue treatments of the mutant . Plant susceptibility to five of the eight pathogens we examined was reduced by the jasmonate response, including two bacteria (Pseudomonas syringae and Xanthomonas campestris), two fungi (Verticillium dahliae and Fusarium oxysporum f . sp . lycopersici), and an oomycete (Phytophthora infestans) . Susceptibility to three fungi was unaffected (Cladosporium fulvum, Oidium neolycopersici, and Septoria lycopersici) . Our results indicate that the jasmonate response reduces damage by a wide range of pathogens from different lifestyles, a result that contrasts with the emerging picture of diseases on Arabidopsis . Thus, the generality of jasmonate-based resistance of tomato challenges the view that ecologically distinct plant parasites are resisted via different mechanisms. Int J Pharm, 2004 Mar 1, 271(1-2), 197 - 205 Evaluation of xanthan and highly substituted galactomannan from M . scabrella as a sustained release matrix; Ughini F et al.; A highly substituted galactomannan (G) from Mimosa scabrella Bentham (Man:Gal 1.1:1), isolated from the seeds of a Brazilian leguminous tree and xanthan (X), an exopolysaccharide secreted by Xanthomonas campestris (Keltrol), were evaluated as a hydrophilic matrix system (XG) for controlled release (CR) of diclofenac sodium (DS) in tablets and capsules . The performance of XG (2:1) matrices containing 50 mg (A) or 100 mg (B) of DS was compared with a commercial CR product of DS . The drug release studies were carried out using a dissolution apparatus (paddle method) with gradual increase of pH values, from pH 1.4, to pH 4.0 (after 1 h) and to pH 6.8 (after 2 h) . The results suggested the potential of XG systems as release retarding materials, which released 78.6 and 35.1% of drug after 24 h for capsules (A) and tablets (A), respectively . Drug release decreased with the increase of amount of drug and it is dependent of dosage form . Analysis of release data indicate a rather zero-order drug release with the erosion mechanism playing a dominant role. J Bacteriol, 2004 May, 186(10), 2946 - 55 Functional dissection of the XpsN (GspC) protein of the Xanthomonas campestris pv . campestris type II secretion machinery; Lee HM et al.; Type II secretion machinery is composed of 12 to 15 proteins for translocating extracellular proteins across the outer membrane . XpsL, XpsM, and XpsN are components of such machinery in the plant pathogen Xanthomonas campestris pv . campestris . All are bitopic cytoplasmic-membrane proteins, each with a large C-terminal periplasmic domain . They have been demonstrated to form a dissociable ternary complex . By analyzing the C-terminally truncated XpsN and PhoA fusions, we discovered that truncation of the C-terminal 103 residues produced a functional protein, albeit present below detectable levels . Furthermore, just the first 46 residues, encompassing the membrane-spanning sequence (residues 10 to 32), are sufficient to keep XpsL and XpsM at normal abundance . XpsN46(His6), synthesized in Escherichia coli, is able to associate in a membrane-mixing experiment with the XpsL-XpsM complex preassembled in X . campestris pv . campestris . The XpsN N-terminal 46 residues are apparently sufficient not only for maintaining XpsL and XpsM at normal levels but also for their stable association . The membrane-spanning sequence of XpsN was not replaceable by that of TetA . However, coimmunoprecipitation with XpsL and XpsM was observed for XpsN97::PhoA, but not XpsN46::PhoA . Only XpsN97::PhoA is dominant negative . Single alanine substitutions for three charged residues within the region between residues 47 and 97 made the protein nonfunctional . In addition, the R78A mutant XpsN protein was pulled down by XpsL-XpsM(His6) immobilized on an Ni-nitrilotriacetic acid column to a lesser extent than the wild-type XpsN . Therefore, in addition to the N-terminal 46 residues, the region between residues 47 and 97 of XpsN probably also plays an important role in interaction with XpsL-XpsM. Theor Appl Genet, 2004 Mar, 108(5), 800 - 7 Epub 2003 Oct 31. High-resolution genetic mapping of Xa27(t), a new bacterial blight resistance gene in rice, Oryza sativa L; Gu K et al.; Bacterial blight of rice, caused by Xanthomonas oryzae pv . oryzae ( Xoo) (Ishyama) Dye, is one of the serious diseases prevalent throughout Asia . In a previous study, a resistance ( R) locus was transferred from the tetraploid wild rice Oryza minuta to the cultivated rice species, Oryza sativa L . Here, we report the fine genetic mapping of the R locus, tentatively designated as Xa27(t) . We performed disease evaluation with an Xa27(t) near-isogenic line, IRBB27, testing 35 Xoo strains collected from 11 countries . The Xa27(t) locus conferred a high level of resistance to 27 strains and moderate resistance to three strains . Resistance of the Xa27(t) gene was developmentally regulated in IRBB27 and showed semi-dominant or a dosage effect in the cv . CO39 genetic background . As a prelude to cloning Xa27(t), a molecular mapping strategy was employed with a large mapping population consisting of 3,875 gametes . Three molecular markers, M336, M1081, and M1059, closely linked to Xa27(t), were identified to facilitate the mapping of Xa27(t) to the long arm of chromosome 6 . The Xa27(t) locus was confirmed by chromosome landing of M1081 and M1095 markers on the rice genome . Markers derived from the genomic sequence of O . sativa cv . Nipponbare were used to further saturate the Xa27(t) genomic region . Xa27(t) was finally located within a genetic interval of 0.052 cM, flanked by markers M964 and M1197, and co-segregated with markers M631, M1230, and M449. Plant Physiol, 2004 May, 135(1), 561 - 73 Epub 2004 Apr 23. Capsicum annuum tobacco mosaic virus-induced clone 1 expression perturbation alters the plant's response to ethylene and interferes with the redox homeostasis; Shin R et al.; Capsicum annuum tobacco mosaic virus (TMV)-induced clone 1 (CaTin1) gene was expressed early during incompatible interaction of hot pepper (Caspsicum annuum) plants with TMV and Xanthomonas campestris . RNA-blot analysis showed that CaTin1 gene was expressed only in roots in untreated plants and induced mainly in leaf in response to ethylene, NaCl, and methyl viologen but not by salicylic acid and methyl jasmonate . The ethylene dependence of CaTin1 induction upon TMV inoculation was demonstrated by the decrease of CaTin1 expression in response to several inhibitors of ethylene biosynthesis or its action . Transgenic tobacco (Nicotiana tabacum) plants expressing CaTin1 gene in sense- or antisense-orientation showed interesting characteristics such as the accelerated growth and the enhanced resistance to biotic as well as abiotic stresses . Such characteristics appear to be caused by the elevated level of ethylene and H2O2 . Moreover, in transgenic plants expressing antisense CaTin1 gene, the expression of some pathogenesis-related genes was enhanced constitutively, which may be mainly due to the increased ethylene level . The promoter of CaTin1 has four GCC-boxes, two AT-rich regions, and an elicitor-inducible W-box . The induction of the promoter activity by ethylene depends on GCC-boxes and by TMV on W-box . Taken together, we propose that the CaTin1 up-regulation or down-regulation interferes with the redox balance of plants leading to the altered response to ethylene and biotic as well as abiotic stresses. Mol Plant Microbe Interact, 2004 Apr, 17(4), 414 - 27 Albicidin pathotoxin produced by Xanthomonas albilineans is encoded by three large PKS and NRPS genes present in a gene cluster also containing several putative modifying, regulatory, and resistance genes; Royer M et al.; Xanthomonas albilineans, which causes leaf scald disease of sugarcane, produces a highly potent pathotoxin called albicidin . We report here sequencing and homology analysis of the major gene cluster, XALB1 (55,839 bp), and a second, smaller region, XALB2 (2,986 bp), involved in albicidin biosynthesis . XALB1 contains 20 open reading frames, including i) three large genes with a modular architecture characteristic of polyketide synthases (PKSs) and nonribosomal peptide synthases (NRPSs) and ii) several putative modifying, regulatory, and resistance genes . Sequencing and complementation studies of six albicidin-defective mutants enabled us to confirm the involvement of the three PKS and NRPS genes encoded by XALB1 in albicidin production . XALB2 contains only one gene that is required for post-translational activation of PKS and NRPS enzymes, confirming the involvement of these enzymes in albicidin biosynthesis . In silico analysis of these three PKS or NRPS enzymes allowed us to propose a model for the albicidin backbone assembly and to gain insight into the structural features of this pathotoxin . This is the first description of a complete mixed PKS-NRPS gene cluster for toxin production in the genus Xanthomonas. Bioinformatics, 2004 Oct 12, 20(15), 2473 - 5 Epub 2004 Apr 08. G-PRIMER: greedy algorithm for selecting minimal primer set; Wang J et al.; G-PRIMER, a web-based primer design program, has been developed to compute a minimal primer set specifically annealed to all the open reading frames in a given microbial genome . This program has been successfully used in the microarray experiment for analyzing the expression of genes in the Xanthomonas campestris genome . AVAILABILITY: It is available at Its source code is available upon request. Sichuan Da Xue Xue Bao Yi Xue Ban, 2004 Mar, 35(2), 158 - 60 {Cloning the gene fragment coding the putative integrase-like protein from X maltophilia}; Liang SF et al.; OBJECTIVE: To amplify the nucleotide sequence of CG-like receptor from X anthomonas maltophilia(X maltophilia) . METHODS: Using the specific primer P1 designed by Grover's reported 342 bp partial nucleotide sequence of X maltophilia CG-like receptor and random primer to PCR amplify, PCR product was cloned in the pUCm-T vector . After the recombinant plasmid was tested by restriction endonuclease digestion, the insert on the recombinant plasmid was sequenced and analyzed . RESULTS: About 500 bp PCR product was cloned in the pUCm-T vector and obtained the recombinant pUCm-Int . By sequencing to the insert on the pUCm-Int with M13 universal sequencing primers, the 410-486 bp fragment of the cloned 510 bp nucleotide sequence (GenBank accession number: AY363962) showed 84% identity with the 9304-8958 bp fragment of the XACb0009 gene on plasmid pXAC64 of Xanthomonas axonopodis pv . citri . And the 4-166aa fragment of its translated 169aa sequence had 62% identity with the 38-200aa sequence of integrase-like protein coded by the XACb0009 gene . CONCLUSION: The cloned 510 bp nucleotide sequence was possibly the partial gene sequence coding the integrase-like protein of X maltophilia. Curr Microbiol, 2004 May, 48(5), 354 - 9 The oligopeptide permease (Opp) of the plant pathogen Xanthomonas axonopodis pv . citri; Moutran A et al.; The oligopeptide permease (Opp), a protein-dependent ABC transporter, has been found in the genome of Xanthomonas axonopodis pv . citri ( Xac), but not in Xanthomonas campestris pv . campestris ( Xcc) . Sequence analysis indicated that 4 opp genes ( oppA, oppB, oppC, oppD/F), located in a 33.8-kbp DNA fragment present only in the Xac genome, are arranged in an operon-like structure and share highest sequence similarities with Streptomyces roseofulvus orthologs . Nonetheless, analyses of the GC content, codon usage, and transposon positioning suggested that the Xac opp operon does not have an exogenous origin . The presence of a stop codon at one of the ATP-binding domains of OppD/F would render the uptake system nonfunctional, but detection of a single polycistronic mRNA and periplasmic OppA in actively growing bacteria suggests that the Opp permease is active and could contribute to the distinct nutritional requirements and host specificities of the two Xanthomonas species. J Bacteriol, 2004 Apr, 186(8), 2309 - 18 Characterization of the cis-acting regulatory element controlling HrpB-mediated activation of the type III secretion system and effector genes in Ralstonia solanacearum; Cunnac S et al.; The ability of Ralstonia solanacearum to cause disease on plants depends on its type III secretion system (TTSS) encoded by hrp genes . The expression of hrp genes and known TTSS substrates is coordinately regulated by HrpB, a member of the AraC family of transcriptional regulators . Two HrpB-regulated promoters (hrpY and popABC) were characterized by deletion analysis, and the HrpB-dependent activation of these promoters was found to be conferred by a 25-nucleotide DNA element, the hrp(II) box (TTCGn16TTCG), which is present in other hrp promoters . The hrp(II) box element is an imperfect plant inducible promoter box, an element which was originally found in hrp promoters of Xanthomonas campestris (S . Fenselau and U . Bonas, Mol . Plant-Microbe Interact . 8:845-854, 1995) but which was not characterized at the molecular level . Site-directed mutagenesis showed that the hrp(II) box is essential for hrpY promoter activation in vivo . Functional analysis of the hrp(II) box element identified critical parameters that are required for HrpB-dependent activity . Further mapping analyses of several other hrpB-dependent promoters also indicated that the position of the hrp(II) box is conserved, at -70 to -47 bp from the transcriptional start . As a first step toward identifying novel TTSS effectors, we used the hrp(II) box consensus sequence to search for potential HrpB-regulated promoters in the complete genome sequence of R . solanacearum strain GMI1000 . Among the 114 genes identified, a subset of promoters was found to have a structural relationship with hrp promoters, thus providing a pool of candidate genes encoding TTSS effectors. Folia Microbiol (Praha), 2003, 48(6), 799 - 804 Characterization of two antagonistic strains of Rahnella aquatilis isolated from soil in Egypt; el-Hendawy HH et al.; In an attempt to obtain biological control agents for controlling bacterial spot of cucumber, over 250 bacterial strains were isolated from agricultural soil samples, collected from different localities in Giza Governorate (Egypt) and screened for in vitro antibiosis towards Xanthomonas campestris . Only 2 strains showed antagonistic activity . They and their culture filtrates restricted the growth of a number of G- and G(+)-indicator bacteria . On Chrome Azurol S agar, both strains exhibited a marked siderophore production . Biolog plates identified these strains as Rahnella aquatilis . Their characteristics were studied and compared with literature data on R . aquatilis . This antagonistic bacterium has not been previously isolated in Egypt. Curr Microbiol, 2004 Apr, 48(4), 251 - 61 PilR enhances the sensitivity of Xanthomonas axonopodis pv . citri to the infection of filamentous bacteriophage Cf; Yang YC et al.; The pilA gene, which encodes the major structure of pili, is required for infection of Xanthomonas axonopodis pv . citri ( X . a . pv . citri) by the filamentous bacteriophage Cf . Two open reading frames (ORFs) located downstream of pilA were cloned and characterized . One 1392-bp ORF encodes a protein of 464 amino acids which shares substantial similarity with pilR of other bacterial species; the second ORF ( orf618), of 1854-bp, shares sequence similarity with pilS . The existence of the pilR-like and pilS-like genes in various X . campestris pathovars indicated that these two genes are well conserved in Xanthomonas . pilR and pilS mutants were constructed by gene replacement . We found that a pilR mutant, resistant to the infection of phage Cf, was unable to synthesize PilA protein; however, the abundance of the PilA protein and of the pilA transcript was markedly increased by the introduction of a plasmid containing the cloned pilR gene . The restoration of the normal pilus-specific sensitivity of this transformed clone to Cf indicated that the pilR gene functions as a transcriptional regulator of pilA . The pilS mutant, however, was susceptible to Cf infection, and the level of pilA expression in this mutant was similar to that of wild-type cells . Promoter analysis of luciferase reporter gene constructs containing the 5' untranslated regions of pilR or pilS genes revealed that, although the pilR and pilS are contiguous in X . a . pv . citri, the two genes are expressed independently, and the strong pilR promoter leads to the accumulation of PilR in X . a . pv . citri, which positively regulates the biosynthesis of PilA . These results revealed the enhanced sensitivity of X . a . pv . citri to phage Cf in the presence of PilR and indicated that the filamentous phage Cf utilize bacterial pili as a receptor site for its infection. Mol Cells, 2004 Feb 29, 17(1), 144 - 50 Molecular characterization of a pathogenesis-related protein 8 gene encoding a class III chitinase in rice; Park CH et al.; A cDNA encoding a class III chitinase (Oschib1) was isolated from a cDNA library constructed from rice leaves infected with the blast fungus Magnaporthe grisea . The cDNA contains an open reading frame of 861 nucleotides encoding 286 amino acid residues with a pI of 5.06 . The deduced amino acid sequence of Oschibl has a high level of similarity with class IIIb chitinases of Gladiolus gandavensis (46%) and Tulipa bakeri (49%) . A high level of Oschibl mRNA was detected after inoculation with M . grisea or Xanthomonas oryzae pv . oryzae . Expression of Oschib1 was induced more rapidly when an avirulent strain of M . grisea was inoculated (incompatible interaction) than when a virulent strain was used (compatible interaction) . Expression of Oschibl was also induced by treatment of signaling molecules such as salicylic acid, ethylene, and methyl jasmonic acid, and by treatment with H2O2 or CuSO4 . The induction patterns of Oschibl expression suggest that Oschib1 may be involved in defense response against pathogen infections and may be classified as a member of pathogenesis-related protein 8 in rice. BMC Evol Biol . 2004 Mar 24;4(1):10. A plant natriuretic peptide-like gene in the bacterial pathogen Xanthomonas axonopodis may induce hyper-hydration in the plant host: a hypothesis of molecular mimicry; Nembaware V et al.; BACKGROUND: Plant natriuretic peptides (PNPs) are systemically mobile molecules that regulate homeostasis at nanomolar concentrations . PNPs are up-regulated under conditions of osmotic stress and PNP-dependent processes include changes in ion transport and increases of H2O uptake into protoplasts and whole tissue . PRESENTATION OF THE HYPOTHESIS: The bacterial citrus pathogen Xanthomonas axonopodis pv . Citri str . 306 contains a gene encoding a PNP-like protein . We hypothesise that this bacterial protein can alter plant cell homeostasis and thus is likely to represent an example of molecular mimicry that enables the pathogen to manipulate plant responses in order to bring about conditions favourable to the pathogen such as the induced plant tissue hyper-hydration seen in the wet edged lesions associated with Xanthomonas axonopodis infection . TESTING THE HYPOTHESIS: We found a Xanthomonas axonopodis PNP-like protein that shares significant sequence similarity and identical domain organisation with PNPs . We also observed a significant excess of conserved residues between the two proteins within the domain previously identified as being sufficient to induce biological activity . Structural modelling predicts identical six stranded double-psi beta barrel folds for both proteins thus supporting the hypothesis of similar modes of action . No significant similarity between the Xanthomonas axonopodis protein and other bacterial proteins from GenBank was found . Sequence similarity of the Xanthomonas axonopodis PNP-like protein with the Arabidopsis thaliana PNP (AtPNP-A), shared domain organisation and incongruent phylogeny suggest that the PNP-gene may have been acquired by the bacteria in an ancient lateral gene transfer event . Finally, activity of a recombinant Xanthomonas axonopodis protein in plant tissue and changes in symptoms induced by a Xanthomonas axonopodis mutant with a knocked-out PNP-like gene will be experimental proof of molecular mimicry . IMPLICATION OF THE HYPOTHESIS: If the hypothesis is true, it could at least in part explain why the citrus pathogen Xanthomonas campestris that does not contain a PNP-like gene produces dry corky lesions while the closely related Xanthomonas axonopodis forms lesions with wet edges . It also suggests that genes typically found in the host, horizontally transferred or heterologous, can help to explain aspects of the physiology of the host-pathogen interactions. Mol Gen Mikrobiol Virusol, 2004, (1), 18 - 21 {Phytase activity in some groups of bacteria . Search for and cloning of genes for bacterial phytases}; Shedova EN et al.; A search for phytase genes in 9 Bacillus strains from the collection of IMGAN was implemented . The growth optimum of strains IX-22, IX-12B, K17-2, K18, IMG I, IMG II, M4 and M8 was 50-60 degrees C; the optimal growth temperature for Bacillus sp . 790 was 45-47 degrees C . According to the sequence data of 16S RNA genes, Bacillus sp . 790 belongs to the B . subtilis/amyloliquefaciens group . The other 8 strains were identified as B . licheniformis . Selection of Bacillus strains, potentially containing the phytase genes, was performed via PCR with primers designed on the basis of the conserved sequence regions of the phyA gene from B . amyloliquefaciens FZB45 with chromosomal DNA being used as the template . The nucleotide sequences of all PCR fragments showed a high level of homology to the known Bacillus phytase genes . The gene libraries of B . licheniformis M8 and B . amyloliquefaciens 790 in E . coli were constructed and phytase-containing clones were selected from them . Twenty-four Pseudomonas strains of different species, 5 Xanthomonas maltophilia strains and 1 Xanthomonas malvacearum (all from the mentioned collection) were tested for phytase activity . Such activity was found in 13 Pseudomonas strains and in 6 Xanthomonas strains . The accumulation of phytase in Pseudomonas was shown to take place at later (over 2 days') growth stages . The optimum pH for phytase from 3 Pseudomonas strains were established . The enzymes were found to be most active at pH 5.5. Genetics, 2004 Feb, 166(2), 693 - 706 Effector genes of Xanthomonas axonopodis pv . vesicatoria promote transmission and enhance other fitness traits in the field; Wichmann G et al.; Establishing durable disease resistance in agricultural crops, where much of the plant defense is provided through effector-R gene interactions, is complicated by the ability of pathogens to overcome R gene resistance by losing the corresponding effector gene . Many proposed methods to maintain disease resistance in the field depend on the idea that effector gene loss results in a fitness cost to the pathogen . In this article we test for fitness costs of effector gene function loss . We created directed knockouts of up to four effector genes from the bacterial plant pathogen Xanthomonas axonopodis pv . vesicatoria (Xav) and examined the effect of the loss of a functional gene product on several important fitness parameters in the field . These traits included transmission, lesion development, and epiphytic survival . We found that the products of all four effector genes had significant and often additive effects on fitness traits . Additional greenhouse tests revealed costs of effector gene loss on in planta growth and further showed that the effects on lesion development were separable from the effects on growth . Observable fitness effects of the three plasmid-borne effector genes were dependent upon the loss of functional avrBs2, indicating that complex functional interactions exist among effector genes with Xav. Annu Rev Phytopathol, 1998, 36, 41 - 58 Diversity among xanthomonads pathogenic on pepper and tomato; Jones JB et al.; Xanthomonas campestris pv . vesicatoria, causal agent of bacterial spot of tomato and pepper, had been considered for nearly 70 years to be a relatively homogeneous organism . However, in the past decade this bacterium was determined to be composed of two genetically and phenotypically distinct groups . The two groups, designated A and B, were distinguished based on amylolytic activity, expression of unique protein bands, reaction on differential hosts (tomato races T1 and T2), reaction patterns with monoclonal antibodies, DNA restriction profiles, and DNA:DNA hybridization . The A and B groups were placed into X . axonopodis pv . vesicatoria and X . vesicatoria, respectively . A third group, designated C, was pathogenically (race T3) and serologically distinct from A and B strains, and formed unique DNA restriction profiles . DNA:DNA hybridization data suggest that C is distinct but related to A strains and may represent a subspecies of A . A final group, designated D, consisted of X . gardneri, an organism identified in Yugoslavia in 1957, and also found in Costa Rica . Group D was determined to be genetically distinct from strains within the other two groups; it represents a third Xanthomonas species pathogenic on tomato and pepper. Biotechnol Lett, 2004 Jan, 26(2), 171 - 5 In vitro mutagenesis of Xanthomonas campestris alpha-amylase gene by partially replacing deoxythymidine triphosphate with 5-bromo-2'-deoxyuridine-5'-triphosphate using a PCR technique; Ma XD et al.; Three mutants of the wild type alpha-amylase gene from Xanthomonas campestris pv . campestris 8004 were obtained using a PCR technique in which deoxythymidine triphosphate (dTTP) was partially replaced by 5-bromo-2'-deoxyuridine-5'-triphosphate (BrdUTP), at an optimal dTTP:BrdUTP ratio of 1000:1 . Of thre three mutants that were obtained and which were sequenced, one mutant with 40 times higher activity than the wild type alpha-amylase gene product was obtained by using primary PCR products as a template for a second PCR reaction. Biochim Biophys Acta, 2004 Feb 20, 1676(3), 211 - 22 Identification of a novel pathogen-induced gene encoding a leucine-rich repeat protein expressed in phloem cells of Capsicum annuum; Jung EH et al.; The CALRR1 gene, expressed in pepper leaves following infection by Xanthomonas campestris pv . vesicatoria, encodes a secreted leucine-rich repeat (LRR) with five tandem repeats of a 24-amino-acid LRR motif . Northern blot analyses revealed that CALRR1 is not constitutively expressed in pepper plants, but is strongly induced upon the infection by X . campestris pv . vesicatoria, Phytophthora capsici, Colletotrichum coccodes and Colletotrichum gloeosporioides on leaves . CALRR1 was not systemically induced in upper leaves by bacterial infection . The inoculation of bacterial live cells, and treatment with dead cells and culture filtrates of pathogenic or nonpathogenic bacteria triggered the accumulation of CALRR1 transcripts . Treatment with signaling molecules, including salicylic acid (SA), ethylene (ET), methyl jasmonate (MeJA), dl-beta-amino-n-butyric acid (BABA) and benzothiadiazole (BTH), did not activate the transcription of the CALRR1 gene, indicating that CALRR1 expression is not regulated by defense signaling pathways activated by these molecules . CALRR1 was induced by treatment with high salinity, abscisic acid (ABA) and wounding, but not by drought and cold stress . An in situ hybridization study showed that CALRR1 mRNA was localized in phloem tissues of leaves, stems, and green fruits of pepper plants during the pathogen infection and ABA exposure . The location characteristics and the spatio-temporal expression pattern of CALRR1 suggest that it may play a role in protecting phloem cells against biotic and abiotic stresses affecting phloem function. J Bacteriol, 2004 Mar, 186(5), 1374 - 80 Evidence for HrpXo-dependent expression of type II secretory proteins in Xanthomonas oryzae pv . oryzae; Furutani A et al.; Xanthomonas oryzae pv . oryzae is a causal agent of bacterial leaf blight of rice . Recently, an efficient hrp-inducing medium, XOM2, was established for this bacterium . In this medium, more than 10 proteins were secreted from the wild-type strain of X . oryzae pv . oryzae . Many of these proteins disappeared or decreased in amount in culture on XOM2 when incubated with the strain that has a mutation in the hrp regulatory gene . Interestingly, the secretory protein profile of a mutant lacking a type III secretion system (TTSS), components of which are encoded by hrp genes, was similar to that of the wild-type strain except that a few proteins had disappeared . This finding suggests that many HrpXo-dependent secretory proteins are secreted via systems other than the TTSS . By isolating mutant strains lacking a type II secretion system, we examined this hypothesis . As expected, many of the HrpXo-dependent secretory proteins disappeared or decreased when the mutant was cultured in XOM2 . By determining the N-terminal amino acid sequence, we identified one of the type II secretory proteins as a cysteine protease homolog, CysP2 . Nucleotide sequence analysis revealed that cysP2 has an imperfect plant-inducible-promoter box, a consensus sequence which HrpXo regulons possess in the promoter region, and a deduced signal peptide sequence at the N terminus . By reverse transcription-PCR analysis and examination of the expression of CysP2 by using a plasmid harboring a cysP2::gus fusion gene, HrpXo-dependent expression of CysP2 was confirmed . Here, we reveal that the hrp regulatory gene hrpXo is also involved in the expression of not only hrp genes and type III secretory proteins but also some type II secretory proteins. Mol Plant Microbe Interact, 2004 Feb, 17(2), 140 - 51 Overexpression of (At)NPR1 in rice leads to a BTH- and environment-induced lesion-mimic/cell death phenotype; Fitzgerald HA et al.; Systemic acquired resistance (SAR) is an inducible defense response that protects plants against a broad spectrum of pathogens . A central regulator of SAR in Arabidopsis is NPR1 (nonexpresser of pathogenesis-related genes) . In rice, overexpression of Arabidopsis NPR1 enhances plant resistance to the bacterial pathogen Xanthomonas oryzae pv . oryzae . This report demonstrates that overexpression of (At)NPR1 in rice also triggers a lesion-mimic/cell death (LMD) phenotype . The LMD phenotype is environmentally regulated and heritable . In addition, the development of lesions and death correlates with the expression of rice defense genes and the accumulation of hydrogen peroxide . Application of the salicylic acid (SA) analog, benzo(1,2,3) thiadiazole-7-carbothioc acid S-methyl ester (BTH), potentiates this phenotype Endogenous SA levels are reduced in rice overexpressing (At)NPR1 when compared with wildtype plants, supporting the idea that (At)NPR1 may perceive and modulate the accumulation of SA . The association of (At)NPR1 expression in rice with the development of an LMD phenotype suggests that (At)NPR1 has multiple roles in plant stress responses that may affect its efficacy as a transgenic tool for engineering broad-spectrum resistance. Plant J, 2004 Feb, 37(4), 517 - 27 Xa26, a gene conferring resistance to Xanthomonas oryzae pv . oryzae in rice, encodes an LRR receptor kinase-like protein; Sun X et al.; Rice bacterial blight, caused by Xanthomonas oryzae pv . oryzae (Xoo), is one of the most serious rice diseases worldwide . A rice gene, Xa26, conferring resistance against Xoo at both seedling and adult stages was isolated by map-based cloning strategies from the rice cultivar Minghui 63 . Xa26 belongs to a multigene family consisting of four members . It encodes a leucine-rich repeat (LRR) receptor kinase-like protein and is constitutively expressed . Sequence analysis revealed that IRBB3 and Zhachanglong lines that are resistant to a broad range of Xoo strains, also carry Xa26 . However, significant difference in lesion length was observed among these lines after inoculation with a set of Xoo strains . Moreover, transgenic plants carrying Xa26 showed enhanced resistance compared with the donor line of the gene in both seedling and adult stages . These results suggest that the resistance conferred by Xa26 is influenced by the genetic background. Funct Integr Genomics, 2004 Jul, 4(3), 196 - 205 Epub 2004 Feb 04. EST and microarray analyses of pathogen-responsive genes in hot pepper ( Capsicum annuum L.) non-host resistance against soybean pustule pathogen ( Xanthomonas axonopodis pv . glycines); Lee S et al.; Large-scale single-pass sequencing of cDNA libraries and microarray analysis have proven to be useful tools for discovering new genes and studying gene expression . As a first step in elucidating the defense mechanisms in hot pepper plants, a total of 8,525 expressed sequence tags (ESTs) were generated and analyzed in silico . The cDNA microarray analysis identified 613 hot pepper genes that were transcriptionally responsive to the non-host soybean pustule pathogen Xanthomonas axonopodis pv . glycines ( Xag) . Several functional types of genes, including those involved in cell wall modification/biosynthesis, transport, signaling pathways and divergent defense reactions, were induced at the early stage of Xag infiltration . In contrast, genes encoding proteins that are involved in photosynthesis, carbohydrate metabolism and the synthesis of chloroplast biogenetic proteins were down-regulated at the late stage of Xag infiltration . These expression profiles share common features with the expression profiles elicited by other stresses, such as fungal challenge, wounding, cold, drought and high salinity . However, we also identified several novel transcription factors that may be specifically involved in the defense reaction of the hot pepper . We also found that the defense reaction of the hot pepper may involve the deactivation of gibberellin . Furthermore, many genes encoding proteins with unknown function were identified . Functional analysis of these genes may broaden our understanding of non-host resistance . This study is the first report of large-scale sequencing and non-host defense transcriptome analysis of the hot pepper plant species . (The sequence data in this paper have been submitted to the dbEST and GenBank database under the codes 10227604-10236595 and BM059564-BM068555, respectively . Additional information is available at http://plant.pdrc.re.kr/ks200201/pepper.html). Int J Syst Evol Microbiol, 2004 Jan, 54(Pt 1), 15 - 24 Polyphasic characterization of xanthomonads isolated from onion, garlic and Welsh onion (Allium spp.) and their relatedness to different Xanthomonas species; Roumagnac P et al.; Bacterial blight is an emerging disease that affects primarily onion, but also garlic and Welsh onion . The present study was undertaken to characterize the causative xanthomonad(s) by a polyphasic approach using a worldwide collection of 33 bacterial strains . Analysis of 16S rRNA gene sequence similarities indicated that the causal agent belongs to the campestris core in the genus Xanthomonas, which is in agreement with results of phenotypic characterization (analyses of carbon source utilization and fatty acid methyl esters) . However, DNA-DNA hybridization, thermal stability of DNA reassociation and fluorescent amplified fragment length polymorphism analysis allowed the causal agent to be identified as a pathovar of Xanthomonas axonopodis. J Biol Chem, 2004 Apr 9, 279(15), 14819 - 27 Epub 2004 Jan 23. LeMPK3 is a mitogen-activated protein kinase with dual specificity induced during tomato defense and wounding responses; Mayrose M et al.; Mitogen-activated protein (MAP) kinase cascades are readily activated during the response of plants to avirulent pathogens or to pathogen-derived elicitors . Here we show that the tomato MAP kinase LeMPK3 is specifically induced at the mRNA level during elicitation of the hypersensitive response in resistant plants infected by avirulent strains of the phytopathogenic bacteria Xanthomonas campestris pv . vesicatoria and Pseudomonas syringae pv . tomato, as well as upon treatment with the fungal elicitor ethylene-inducing xylanase . LeMPK3 gene expression was also induced very rapidly by mechanical stress and wounding much earlier than upon pathogen infection, but not in response to the defense-related plant hormones ethylene and jasmonic acid . Moreover, in resistant tomato plants infected by X . campestris pv . vesicatoria, transcript accumulation was followed by an increase in LeMPK3 kinase activity . Biochemical characterization of a glutathione S-transferase-LeMPK3 fusion protein revealed that the LeMPK3 MAP kinase autophosphorylates in vitro mainly on tyrosine and less so on threonine and serine, whereas it phosphorylates myelin basic protein on serine and threonine . In vitro phosphorylation of a poly-(Glu-Tyr) copolymer by LeMPK3 demonstrated its capability to phosphorylate tyrosine residues on substrates as well . By mutagenesis and phosphoamino acid analysis, Tyr-201 in the kinase activation domain was identified as the main LeMPK3 autophosphorylation site and as critical for kinase activity . Finally, LeMPK3 autophosphorylation showed a preference for Mn(2+) cations and proceeded via an intramolecular mechanism with an estimated K(m) value for ATP of 9.5 microm . These results define LeMPK3 as a MAP kinase with dual specificity and strongly suggest that it represents a convergence point for different signaling pathways inducing the activation of defense responses in tomato. Glycobiology, 2004 Mar, 14(3), 233 - 41 Epub 2004 Jan 21. Functional characterization of GumK, a membrane-associated beta-glucuronosyltransferase from Xanthomonas campestris required for xanthan polysaccharide synthesis; Barreras M et al.; Xanthomonas campestris is a Gram-negative bacterium that produces an exopolysaccharide known as xanthan gum . Xanthan is involved in a variety of biological functions, including pathogenesis, and is widely used in the industry as thickener and viscosifier . Although the genetics and biosynthetic process of xanthan are well documented, the enzymatic components have not been examined and no data on glycosyltransferases have been reported . We describe the functional characterization of the gumK gene product, an essential protein for xanthan synthesis . Immunoblots and complementation studies showed that GumK is a 44-kDa protein associated to the membrane fraction . This value corresponds to the expected molecular mass for GumK encoded by an extended open reading frame than proposed from previous genetic data and in X . campestris published complete genome . The protein was expressed in Escherichia coli cells . The purified protein catalyzed the transfer of a glucuronic acid residue from UDP-glucuronic acid to mannose-alpha-1,3-glucose-beta-1,4-glucose-P-P-polyisoprenyl with formation of a glucuronic acid-beta-mannose linkage . We examined the acceptor substrate specificity . GumK was unable to use the trisaccharide acceptor freed from the pyrophosphate lipid moiety . Replacement of the natural lipid moiety by phytanyl showed that the catalytic function could proceed with glucuronic acid transfer . These results suggest the enzyme does not show specificity for the lipidic portion of the acceptor . GumK showed diminished activity when tested with 6-O-acetyl-mannose-alpha-1,3-glucose-beta-1,4-glucose-P-P-polyisoprenyl, a putative intermediate in the synthesis of xanthan . This could indicate that acetylation of the internal mannose takes place after the formation of the GumK product. Mol Microbiol, 2004 Feb, 51(3), 903 - 12 A bacterial cell-cell communication signal with cross-kingdom structural analogues; Wang LH et al.; Extracellular signals are the key components of microbial cell-cell communication systems . This report identified a diffusible signal factor (DSF), which regulates virulence in Xanthomonas campestris pv . campestris, as cis-11-methyl-2-dodecenoic acid, an alpha,beta unsaturated fatty acid . Analysis of DSF derivatives established the double bond at the alpha,beta positions as the most important structural feature for DSF biological activity . A range of bacterial pathogens, including several Mycobacterium species, also displayed DSF-like activity . Furthermore, DSF is structurally and functionally related to farnesoic acid (FA), which regulates morphological transition and virulence by Candida albicans, a fungal pathogen . Similar to FA, which is also an alpha,beta unsaturated fatty acid, DSF inhibits the dimorphic transition of C . albicans at a physiologically relevant concentration . We conclude that alpha,beta unsaturated fatty acids represent a new class of extracellular signals for bacterial and fungal cell-cell communications . As prokaryote-eukaryote interactions are ubiquitous, such cross-kingdom conservation in cell-cell communication systems might have significant ecological and economic importance. Appl Environ Microbiol, 2004 Jan, 70(1), 255 - 61 Genetic structure and population dynamics of Xanthomonas axonopodis pv . manihotis in Colombia from 1995 to 1999; Restrepo S et al.; Restriction fragment length polymorphisms (RFLPs) were used to study the population genetics and temporal dynamics of the cassava bacterial pathogen Xanthomonas axonopodis pv . manihotis . The population dynamics were addressed by comparing samples collected from 1995 to 1999 from six locations, spanning four different edaphoclimatic zones (ECZs) . Forty-five different X . axonopodis pv . manihotis RFLP types or haplotypes were identified between 1995 and 1999 . High genetic diversity of the X . axonopodis pv . manihotis strains was evident within most of the fields sampled . In all but one site, diversity decreased over time within fields . Haplotype frequencies significantly differed over the years in all but one location . Studies of the rate of change of X . axonopodis pv . manihotis populations during the cropping cycle in two sites showed significant changes in the haplotype frequencies but not composition . However, variations in pathotype composition were observed from one year to the next at a single site in ECZs 1 and 2 and new pathotypes were described after 1997 in these ECZs, thus revealing the dramatic change in the pathogen population structure of X . axonopodis pv . manihotis . Disease incidence was used to show the progress of cassava bacterial blight in Colombia during the 5-year period in different ecosystems . Low disease incidence values were correlated with low rainfall in 1997 in ECZ 1. J Bacteriol, 2004 Jan, 186(2), 411 - 8 Molecular and functional characterization of a unique sucrose hydrolase from Xanthomonas axonopodis pv . glycines; Kim HS et al.; A novel sucrose hydrolase (SUH) from Xanthomonas axonopodis pv . glycines, a causative agent of bacterial pustule disease on soybeans, was studied at the functional and molecular levels . SUH was shown to act rather specifically on sucrose (K(m) = 2.5 mM) but not on sucrose-6-phosphate . Protein analysis of purified SUH revealed that, in this monomeric enzyme with an estimated molecular mass of 70,223 +/- 12 Da, amino acid sequences determined for several segments have corresponding nucleotide sequences in XAC3490, a protein-coding gene found in the genome of X . axonopodis pv . citri . Based on this information, the SUH gene, consisting of an open reading frame of 1,935 bp, was cloned by screening a genomic library of X . axonopodis pv . glycines 8ra . Database searches and sequence comparison revealed that SUH has significant homology to some family 13 enzymes, with all of the crucial invariant residues involved in the catalytic mechanism conserved, but it shows no similarity to known invertases belonging to family 32 . suh expression in X . axonopodis pv . glycines requires sucrose induction, and insertional mutagenesis resulted in an absence of sucrose-inducible sucrose hydrolase activity in crude protein extracts and a sucrose-negative phenotype . Recombinant SUH, overproduced in Escherichia coli and purified, was shown to have the same enzymatic characteristics in terms of kinetic parameters. Antimicrob Agents Chemother, 2004 Jan, 48(1), 209 - 15 Constitutive expression of a chromosomal class A (BJM group 2) beta-lactamase in Xanthomonas campestris; Weng SF et al.; Sequencing of the upstream region of the beta-lactamase gene from Xanthomonas campestris pv . campestris 11 (bla(XCC-1)) revealed the cognate ampR1 gene (289 amino acids, 31 kDa) . It runs divergently from bla(XCC-1) with a 100-bp intergenic region (IG) containing partially overlapped promoters with structural features typical of the bla-ampR IG . The deduced AmpR1 protein shows significant identity in amino acid sequence and conserved motifs with AmpR proteins of other species, e.g., of Pseudomonas aeruginosa (58.2% amino acid identity) . Results of insertional mutation, complementation tests, and beta-lactamase assays suggested that expression of bla(XCC-1) was constitutive and dependent on AmpR1 . Four bla genes and two ampR genes are present in the fully sequenced X . campestris pv . campestris ATCC 33913 genome, with XCC3039 and XCC3040 considered the analogues of bla(XCC-1) and ampR1, respectively . An ampR1 homologue was detected by Southern hybridization in the ampicillin-resistant Xanthomonas strains, which appear to express beta-lactamase constitutively . Although the significance remains to be studied, constitutive expression of beta-lactamase by a widespread bacterial genus raises environmental concerns regarding the dissemination of resistance genes. Plant J, 2004 Jan, 37(2), 186 - 98 Pathogenesis-related protein 10 isolated from hot pepper functions as a ribonuclease in an antiviral pathway; Park CJ et al.; A hot pepper (Capsicum annuum) cDNA clone encoding pathogenesis-related protein 10 (CaPR-10) was isolated by differential screening of a cDNA library prepared from pepper leaves inoculated with tobacco mosaic virus pathotype (TMV-P0) . CaPR-10 transcripts were induced in the inc