Insights into Genome Plasticity and Pathogenicity of the Plant Pathogenic Bacterium Xanthomonas campestris pv. vesicatoria Revealed by the Complete Genome Sequence (original) (raw)
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Genomic approaches in Xanthomonas campestris pv. vesicatoria allow fishing for virulence genes
Journal of Biotechnology, 2003
Xanthomonas campestris pv. vesicatoria is an economically important pathogen of pepper and tomato and has been established as a model organism to study bacterial infection strategies. In the last two decades, intensive genetic and molecular analyses led to the isolation of many genes that play a role in the intimate molecular relationship with the host plant. Essential for pathogenicity is a type III protein secretion system, which delivers bacterial effector proteins into the host cell. Currently, the genome of X. campestris pv. vesicatoria is being sequenced. The availability of genomic sequence information will pave the way for the identification of new bacterial virulence factors by bioinformatic approaches. In this article, we will present preliminary data from the genomic sequence analysis and describe recent and novel studies to identify bacterial type III effector genes.
How the bacterial plant pathogen Xanthomonas campestris pv. vesicatoria conquers the host
Molecular Plant Pathology, 2000
Xanthomonas campestris pv. vesicatoria ( Xcv ) is the causal agent of bacterial spot disease on pepper and tomato. Pathogenicity on susceptible plants and the induction of the hypersensitive reaction (HR) on resistant plants requires a number of genes, designated hrp , most of which are clustered in a 23-kb chromosomal region. Nine hrp genes encode components of a type III protein secretion apparatus that is conserved in Gramnegative plant and animal pathogenic bacteria. We have recently demonstrated that Xcv secretes proteins into the culture medium in a hrp -dependent manner. Substrates of the Hrp secretion machinery are pathogenicity factors and avirulence proteins, e.g. AvrBs3. The AvrBs3 protein governs recognition, i.e. HR induction, when bacteria infect pepper plants carrying the corresponding resistance gene Bs3 . Intriguingly, the AvrBs3 protein contains eukaryotic signatures such as nuclear localization signals (NLS), and has been shown to act inside the plant cell. We postulate that AvrBs3 is transferred into the plant cell via the Hrp type III pathway and that recognition of AvrBs3 takes place in the plant cell nucleus.
Comparative genomics reveals diversity among xanthomonads infecting tomato and pepper
BMC Genomics, 2011
Background: Bacterial spot of tomato and pepper is caused by four Xanthomonas species and is a major plant disease in warm humid climates. The four species are distinct from each other based on physiological and molecular characteristics. The genome sequence of strain 85-10, a member of one of the species, Xanthomonas euvesicatoria (Xcv) has been previously reported. To determine the relationship of the four species at the genome level and to investigate the molecular basis of their virulence and differing host ranges, draft genomic sequences of members of the other three species were determined and compared to strain 85-10. Results: We sequenced the genomes of X. vesicatoria (Xv) strain 1111 (ATCC 35937), X. perforans (Xp) strain 91-118 and X. gardneri (Xg) strain 101 (ATCC 19865). The genomes were compared with each other and with the previously sequenced Xcv strain 85-10. In addition, the molecular features were predicted that may be required for pathogenicity including the type III secretion apparatus, type III effectors, other secretion systems, quorum sensing systems, adhesins, extracellular polysaccharide, and lipopolysaccharide determinants. Several novel type III effectors from Xg strain 101 and Xv strain 1111 genomes were computationally identified and their translocation was validated using a reporter gene assay. A homolog to Ax21, the elicitor of XA21-mediated resistance in rice, and a functional Ax21 sulfation system were identified in Xcv. Genes encoding proteins with functions mediated by type II and type IV secretion systems have also been compared, including enzymes involved in cell wall deconstruction, as contributors to pathogenicity.
Diversity of effector genes in plant pathogenic bacteria of genus Xanthomonas
Microbiology, 2010
Gram negative plant pathogenic bacteria are secreting into plant cell a special type of pathogenic ity related proteins called effectors. They are capable of suppressing plant innate immunity or stimulating synthesis and export of metabolites desired by the pathogen. We identified a number of effector coding genes typical of xanthomonads analyzing 8 completely sequenced genomes of genus Xanthomonas. Using represen tative collection provided by Russian Research Institute of Phytopathology we identified genetic diversity of effector gene loci in population of Xanthomonas bacteria. Patterns of effector genes were identified for indi vidual strains and statistic linkage between particular genes and race of the pathogen was established. For the first time several untypical effector genes were found in strains of Xanthomonas campestris pv. campestris.
Proceedings of the National Academy of Sciences, 2004
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
Microbiology-sgm, 2009
This study uses sequences from four genes, which are involved in the formation of the type III secretion apparatus, to determine the role of horizontal gene transfer in the evolution of virulence genes for the enterobacterial plant pathogens. Sequences of Erwinia, Brenneria, Pectobacterium, Dickeya and Pantoea were compared (a) with one another, (b) with sequences of enterobacterial animal pathogens, and (c) with sequences of plant pathogenic c and b proteobacteria, to evaluate probable paths of lateral exchange leading to the current distribution of virulence determinants among these microorganisms. Phylogenies were reconstructed based on hrcC, hrcR, hrcJ and hrcV gene sequences using parsimony and maximum-likelihood algorithms. Virulence gene phylogenies were also compared with several housekeeping gene loci in order to evaluate patterns of lateral versus vertical acquisition. The resulting phylogenies suggest that multiple horizontal gene transfer events have occurred both within and among the enterobacterial plant pathogens and plant pathogenic c and b proteobacteria. hrcJ sequences are the most similar, exhibiting anywhere from 2 to 50 % variation at the nucleotide level, with the highest degree of variation present between plant and animal pathogen sequences. hrcV sequences are conserved among plant and animal pathogens at the N terminus. The C-terminal domain is conserved only among the enterobacterial plant pathogens, as are the hrcC and hrcR sequences. Additionally, hrcJ and hrcV sequence phylogenies suggest that at least some type III secretion system virulence genes from enterobacterial plant pathogens are related more closely to those of the genus Pseudomonas, a conclusion neither supported nor refuted by hrcC or hrcR.
PLoS ONE, 2014
In comparison to dicot-infecting bacteria, only limited numbers of genome sequences are available for monocot-infecting and in particular cereal-infecting bacteria. Herein we report the characterisation and genome sequence of Xanthomonas translucens isolate DAR61454 pathogenic on wheat and barley. Based on phylogenetic analysis of the ATP synthase beta subunit (atpD) gene, DAR61454 is most closely related to other X. translucens strains and the sugarcane-and bananainfecting Xanthomonas strains, but shares a type III secretion system (T3SS) with X. translucens pv. graminis and more distantly related xanthomonads. Assays with an adenylate cyclase reporter protein demonstrate that DAR61454's T3SS is functional in delivering proteins to wheat cells. X. translucens DAR61454 also encodes two type VI secretion systems with one most closely related to those found in some strains of the rice infecting strain X. oryzae pv. oryzae but not other xanthomonads. Comparative analysis of 18 different Xanthomonas isolates revealed 84 proteins unique to cereal (i.e. rice) infecting isolates and the wheat/barley infecting DAR61454. Genes encoding 60 of these proteins are found in gene clusters in the X. translucens DAR61454 genome, suggesting cereal-specific pathogenicity islands. However, none of the cereal pathogen specific proteins were homologous to known Xanthomonas spp. effectors. Comparative analysis outside of the bacterial kingdom revealed a nucleoside triphosphate pyrophosphohydrolase encoding gene in DAR61454 also present in other bacteria as well as a number of pathogenic Fusarium species, suggesting that this gene may have been transmitted horizontally from bacteria to the Fusarium lineage of pathogenic fungi. This example further highlights the importance of horizontal gene acquisition from bacteria in the evolution of fungi.
Profiling the secretomes of plant pathogenic Proteobacteria⋆
FEMS microbiology …, 2005
Secreted proteins are central to the success of plant pathogenic bacteria. They are used by plant pathogens to adhere to and degrade plant cell walls, to suppress plant defence responses, and to deliver bacterial DNA and proteins into the cytoplasm of plant cells. However, experimental investigations into the identity and role of secreted proteins in plant pathogenesis have been hindered by the fact that many of these proteins are only expressed or secreted in planta, that knockout mutations of individual proteins frequently have little or no obvious phenotype, and that some obligate and fastidious plant pathogens remain recalcitrant to genetic manipulation. The availability of genome sequence data for a large number of agriculturally and scientifically important plant pathogens enables us to predict and compare the complete secretomes of these bacteria. In this paper we outline strategies that are currently being used to identify secretion systems and secreted proteins in Proteobacterial plant pathogens and discuss the implications of these analyses for future investigations into the molecular mechanisms of plant pathogenesis.
Cellular Microbiology, 2009
In mid-July a workshop entitled the 'Xanthomonas Genomics Conference' took place at the stunning location of Pingree Park, Colorado State University, USA. This meeting, which was supported this time round by United States Department of Agriculture and US National Science Foundation, was the third official workshop dedicated to the study of phytopathogens belonging to the species Xanthomonas. One of the major goals of this meeting was to discuss the insight that comparative analysis of Xanthomonas genomes has given both to an understanding of the ability of this important group of bacteria to exploit an extraordinary diversity of plant hosts and host tissues, and to the development of needed improvements in disease control and prevention. In this report we give an overview of recent developments in this field that were presented during the meeting. These highlights included the unveiling of 11 new Xanthomonas genomic sequences, structural and functional insights into the peptide Ax21 elicitor, the first description of small non-coding RNAs in Xanthomonas and the role they play in the regulation of virulence, as well as a description of novel type III-secreted effectors which target different hosts.