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At least 289 records · Page 16Linked to original sources
PubMed2006

Comparative genomics of host-specific virulence in Pseudomonas syringae.

While much study has gone into characterizing virulence factors that play a general role in disease, less work has been directed at identifying pathogen factors that act in a host-specific manner. Understanding these factors will help reveal the variety of mechanisms used by pathogens to suppress or avoid host defenses. We identified candidate Pseudomonas syringae host-specific virulence genes by searching for genes whose distribution among natural P. syringae isolates was statistically associated with hosts of isolation. We analyzed 91 strains isolated from 39 plant hosts by DNA microarray-based comparative genomic hybridization against an array containing 353 virulence-associated (VA) genes, including 53 type III secretion system effectors (T3SEs). We identified individual genes and gene profiles that were significantly associated with strains isolated from cauliflower, Chinese cabbage, soybean, rice, and tomato. We also identified specific horizontal gene acquisition events associated with host shifts by mapping the array data onto the core genome phylogeny of the species. This study provides the largest suite of candidate host-specificity factors from any pathogen, suggests that there are multiple ways in which P. syringae isolates can adapt to the same host, and provides insight into the evolutionary mechanisms underlying host adaptation.

Gene Expression Profiling↗
PubMedDate not supplied

[Effect of the lipopolysaccharide-protein complex of Pseudomonas syringae PV. atrofaciens on the process of tumor formation caused by Agrobacterium tumefaciens].

It has been found that the agent of bacterial spotting of rye P. syringae pv. atrofaciens 8281 has no antagonistic action on the strains 9052 and 9054 of Agrobacterium tumefaciens--the agent of crown gall tumor. Lipopolysaccharide-protein complex of P. syringae pv. atrofaciens 8281 when added to the culture medium does not affect the growth and development of A. tumefaciens bacteria. It has been experimentally established that the lipopolysaccharide-protein complex of P. syringae pv. atrofaciens 8281, when used to treat the potato explants before inoculation of A. tumefaciens, decreases induction and development of tumours on the explants. Tumour formation inhibition depends on concentration of lipopolysaccharide-protein complex solution.

Agrobacterium tumefaciens↗
PubMedDate not supplied

[Serological heterogeneity of Pseudomonas syringae pv. atrofaciens strains and their ecological niches].

The paper deals with a comparative analysis of the serological and ecological properties of Pseudomonas syringae pv. atrofaciens strains from the collections of microbial cultures at the Malkov Institute for Plant Genetic Resources and Zabolotny Institute of Microbiology and Virology. All of the strains from the Bulgarian collection, except for one, fall into five serogroups (II through VI) of the classification system of Pastushenko and Simonovich. The P. syringae pv. atrofaciens strains isolated from Bulgarian and Ukrainian wheats belong mainly to serogroups II and IV, respectively. The strains that were isolated from rye plants belong to serogroup I. The strains isolated from sorghum and Sudan grass belong to serogroups II, IV, and VL. Serogroup III includes the P. syringae pv. atrofaciens strains that were isolated from cereals in the United Kingdom but not in Ukraine.

Bulgaria↗
PubMedDate not supplied

[Structural diversity of O-polysaccharides and serological classification of Pseudomonas syringae pv. garcae and other strains of genomospecies 4].

Novel O-serotypes were revealed among Pseudomonas syringae pv. garcae strains by using a set of mouse monoclonal antibodies specific to the lipopolysaccharide O-polysaccharide. Structural studies showed that the O-polysaccharide of P. syringae pv. garcae NCPPB 2708 is a hitherto unknown linear L-rhamnan lacking strict regularity and having two oligosaccharide repeating units I and II, which differ in the position of substitution in one of the rhamnose residues and have the following structures: I: --> 3)-alpha-L-Rha-(1 --> 2)-alpha-L-Rha-(1 --> 2)-alpha-L-Rha-(1 --> 3)-alpha-L-Rha-(1 -->; II: --> 3)-alpha-L-Rha-(1 --> 3)-alpha-L-Rha-(1 --> 2)-alpha-L-Rha-(1 --> 3)-alpha-L-Rha-(1 -->. The branched polysaccharides of P. syringae pv. garcae ICMP 8047 and NCPPB 588 have the same L-rhamnan backbone with repeating units I and II and a lateral chain of (alpha1 --> 4)- or (alpha1 --> 3)-linked residues of 3-acetamido-3,6-dideoxy-D-galactose (D-Fuc3NAc). Several monoclonal antibody epitopes associated with the L-rhamnan backbone or the lateral alpha-D-Fuc3NAc residues were characterized.

Acetylgalactosamine↗
PubMedDate not supplied

[Chemical and biological characterization of lipopolysaccharides from the Pseudomonas syringae pv. maculicola IMV 381 collection culture and its dissociants].

Lipopolysaccharides (LPS) were isolated from the crude bacterial mass of the Pseudomonas syringae pv. maculicola IMV 381 collection culture and its virulent and avirulent subcultures isolated earlier from the heterogeneous collection culture due to its natural variability during long-term storage. The composition, immunochemical properties, and certain parameters of the biological activity of the LPS preparations obtained were studied. The structural parts of the LPS macromolecule--lipid A, the core oligosaccharide, and O-specific polysaccharide (OPS)--were isolated and characterized. The following fatty acids were identified in the lipid A composition of all cultures: 3-OH-C10:0, C12:0, 2-OH-C12:0, 3-OH-C12:0, C16:1, C16:0, C18:1, and C18:0. Glucosamine (GlcN), ethanolamine (EtN), phosphoethanolamine (EtN-P), and phosphorus (P) were revealed in the hydrophilic portion of the macromolecule. In the core portion of the LPS macromolecule, glucose (Glc), rhamnose (Rha), GlcN, galactosamine (GalN), 2-keto-3-deoxyoctulosonic acid (KDO), alanine (Ala), and P were found. The peculiarities of the structure of LPS isolated from the stable collection culture (LPS(stab)) and its virulent (LPS(vir)) and avirulent (LPS(air)) subcultures were studied. LPS(vir) and LPS(avir) were identical in the monosaccharide composition and contained as the main components L-rhamnose (L-Rha) and 3-acetamido-3,6-dideoxy-D-galactose (D-Fuc3NAc), like LPS(stab) studied earlier. The NMR spectra of LPS(vir) were identical to the spectra of LPS(stab), whose O-chain repeating unit structure was studied by us earlier, whereas LPS(avir) differed from LPS(vir) in the NMR spectrum and was identified by us as the SR form. LPS(avir) was serologically identical to LP(stab) and LPS(vir). Hence, the degree of polymerism of the LPS O-chain of P. syringae pv. maculicola IMV 381 is the main virulence factor in the infected model plants. Serological relationships were studied between P. syringae pv. maculicola IMV 381 and the strains of other pathovars with structurally similar LPS.

Animals↗
PubMedDate not supplied

[Mechanism of antimutagenic activity of Pseudomonas syringae lipopolysaccharides].

The antimutagenic activity of lipopolysaccharides of phytopathogenic bacteria,which are the agents of grain crops diseases, has been investigated using bacterial test-system with Salmonella typhimurium. It has been established that the greatest antimutagen activity of Pseudomonas syringae pv. atrofaciens and P. syringae pv. coronafaciens lipopolysaccharides was,if they and bichromate potassium be simultaneously added to cells test-strains of S. typhimurium. They decreased to a less degree quantity of His+ -revertants in S. typhimurium cells pretreated by potassium bichromate. Li popolysaccharides of pathovars of P. syringae do not increase test-strain cells resistance to mutagenic effect of potassium bichromate under pretreatment of S. typhimurium by them.

Antimutagenic Agents↗
PubMed1994

Purification and characterization of CopR, a transcriptional activator protein that binds to a conserved domain (cop box) in copper-inducible promoters of Pseudomonas syringae.

The copper resistance (cop) operon promoter (Pcop) of Pseudomonas syringae is copper-inducible, and requires the regulatory genes copRS. Sequence analysis revealed that CopR has significant homology with other known activator proteins from bacterial two-component regulatory systems. In the present study we characterized Pcop and its interaction with CopR. We found that crude protein extracts from copper-resistant and -sensitive strains of P. syringae contain a Pcop-specific DNA-binding protein. We hypothesized that this DNA-binding protein was the product of copR. A 27-kDa protein, which corresponded to the predicted copR product, was expressed from this gene in Escherichia coli. CopR was purified, and the first eight amino acids were sequenced to confirm its relationship to copR. Specific binding of purified CopR to the plasmid-borne Pcop and the chromosomally encoded cop homolog promoter (PcopH), identified in this report, was demonstrated using specific and non-specific promoter competitors in DNA mobility shift assays. DNAse I footprinting identified a conserved CopR binding region (cop box) on Pcop and PcopH. The cop box contains an inverted repeat within a stretch of 16 bp, which shares approximately 75% identity with the PhoB binding region from several phosphate regulon gene promoters in E. coli. Primer extension analysis identified the transcriptional initiation site of Pcop 59 bp 5' to the translational start site of copA, and the transcriptional initiation site of PcopH 88 bp 5' to the translational start site of the chromosomal homolog of copA. The cop box was localized to between positions -54 and -35 relative to the transcriptional initiation site of Pcop and PcopH. Deletion analysis of Pcop delimited copper-inducible activity to a 104-bp region. Pcop and PcopH do not share a sequence consensus with other characterized promoters from P. syrinagae or E. coli. The results presented delineate important regions on two copper-inducible promoters form P. syringae.

Bacterial Outer Membrane Proteins↗
PubMed2001

Multilocus enzyme electrophoresis analysis of Pseudomonas syringae pv. phaseolicola.

A multilocus enzyme electrophoresis technique was developed to detect variation in seven enzyme loci among isolates of Pseudomonas syringae pv. phaseolicola, representing three races from different geographical locations, the causal agent of the halo blight disease of beans. Cellulose acetate gel electrophoresis of seven enzymes revealed 19 electrotypes (ET) among 21 Pseudomonas syringae pv. phaseolicola isolates. One of the pathovar syringae and one of the pathovar tomato isolates were represented by two different ET. The population of Turkish isolates and three races of the pathovar phaseolicola appeared to be genetically diverse.

Electrophoresis↗
PubMed1999

Phylogenetic analysis of Pseudomonas syringae pathovars suggests the horizontal gene transfer of argK and the evolutionary stability of hrp gene cluster.

Pseudomonas syringae are differentiated into approximately 50 pathovars with different plant pathogenicities and host specificities. To understand its pathogenicity differentiation and the evolutionary mechanisms of pathogenicity-related genes, phylogenetic analyses were conducted using 56 strains belonging to 19 pathovars. gyrB and rpoD were adopted as the index genes to determine the course of bacterial genome evolution, and hrpL and hrpS were selected as the representatives of the pathogenicity-related genes located on the genome (chromosome). Based on these data, NJ, MP, and ML phylogenetic trees were constructed, and thus 3 trees for each gene and 12 gene trees in total were obtained, all of which showed three distinct monophyletic groups: Groups 1, 2 and 3. The observation that the same set of OTUs constitute each group in all four genes suggests that these genes had not experienced any intergroup horizontal gene transfer within P. syringae but have been stable on and evolved along with the P. syringae genome. These four index genes were then compared with another pathogenicity-related gene, argK (the phaseolotoxin-resistant ornithine carbamoyltransferase gene, which exists within the argK-tox gene cluster). All 13 strains of pv. phaseolicola and pv. actinidiae used had been confirmed to produce phaseolotoxin and to have argK, whose sequences were completely identical, without a single synonymous substitution among the strains used (Sawada et al. 1997a). On the other hand, argK were not present on the genomes of the other 43 strains used other than pv. actinidiae and pv. phaseolicola. Thus, the productivity of phaseolotoxin and the possession of the argK gene were shown at only two points on the phylogenetic tree: Group 1 (pv. actinidiae) and Group 3 (pv. phaseolicola). A t test between these two pathovars for the synonymous distances of argK and the tandemly combined sequence of the four index genes showed a high significance, suggesting that the argK gene (or argK-tox gene cluster) experienced horizontal gene transfer and expanded its distribution over two pathovars after the pathovars had separated, thus showing a base substitution pattern extremely different from that of the noncluster region of the genome.

Bacterial Proteins↗
PubMed2001

Biological Control of Pseudomonas syringae pv. glycinea by Epiphytic Bacteria under Field Conditions.

The efficacy of a bacterial strain as a biocontrol agent in the field may be related to the ecological similarity between the biocontrol agent and the target pathogen. Therefore, a number of different Pseudomonas syringae strains were evaluated for their antagonistic activities in vitro (agar-diffusion assay) and in planta (greenhouse assay) against the target pathogen, Pseudomonas syringae pv. glycinea. Six strains of five different pathovars were found to be antagonistic in vitro as well as in planta. The epiphytic fitness of the antagonistic Pseudomonas syringae strain 22d/93 and its two antibiotic-resistant mutants were examined on soybean plants in the fields. After adaptation the parental strain and its mutants had the ability to establish and maintain large epiphytic populations (about 106 cfu/g FW) over the whole growing season after a single spray inoculation. The epiphytic behaviors of the mutants and the parent were not significantly different. The introduced bacteria did not influence the total bacterial population size. When the antagonist was coinoculated with the pathogen, the development of the pathogen was significantly reduced during the whole growing season. When the antagonistic strain was inoculated 4 weeks in advance of the pathogen, this antagonistic effect could be markedly enhanced. The final population size of the pathogen reached just 104 cfu/g FW and was significantly reduced to 0.12% compared to the pathogen alone. This study demonstrates that biological control of foliar pathogens through colonization of the host plants with near isogenic or ecologically similar antagonistical strains seems to be a realistic goal.

Journal Article↗
PubMed1996

Properties of beta-lactamase from Pseudomonas syringae.

Pseudomonas syringae isolate BR2R produces tabtoxin, a beta-lactam-containing antibiotic, and the causative agent of wildfire disease of green bean (Phaseolus vulgaris). beta-Lactamase production has been suggested as the mechanism that protects P. syringae from tabtoxin. We sought to determine whether the organism produces beta-lactamase and whether the enzyme plays a role in protection from this antibiotic. P. syringae and mutants defective in tabtoxin production and resistance produce beta-lactamase. Three distinct beta-lactamases with molecular weights of 41,000 were identified. The isoelectric points of the proteins were 6.1, 6.8, and 9.2. The enzymes preferentially hydrolyze cephalosporin. This investigation demonstrates that the organism produces multiple beta-lactamases and describes characteristics of the proteins.

Isoelectric Focusing↗
PubMed1999

A RNA polymerase with transcriptional activity at 0 degrees C from the Antarctic bacterium Pseudomonas syringae.

A DNA-dependent RNA polymerase was purified from the Antarctic psychrotrophic bacterium Pseudomonas syringae. The RNA polymerase showed a typical eubacterial subunit composition with beta, beta', alpha2 and sigma subunits. The subunits cross-reacted with antibodies raised against holoenzyme and the individual subunits of the RNA polymerase of Escherichia coli. However, the enzyme was considered unique, since unlike the RNA polymerase of mesophilic E. coli it exhibited significant and consistent transcriptional activity (10-15%) even at 0 degrees C. But, similar to the enzyme from the mesophilic bacterium, the RNA polymerase from P. syringae exhibited optimum activity at 37 degrees C. The study also demonstrates that the RNA polymerase of P. syringae could preferentially transcribe the cold-inducible gene cspA of E. coli only at lower temperatures (0-22 degrees C). The polymerase was also observed to be relatively more rifampicin-resistant during transcription at lower temperature.

Adaptation, Biological↗
PubMed2003

RpoN (sigma(54)) is required for plasmid-encoded coronatine biosynthesis in Pseudomonas syringae.

The plant pathogen Pseudomonas syringae pv. glycinea PG4180 produces coronatine (COR), a phytotoxin which functions as a virulence factor in bacterial blight of soybeans. The COR biosynthetic gene cluster in PG4180 is borne on a 90-kb plasmid named p4180A. Although pathway-specific regulatory genes for COR have been identified, global regulatory genes for COR production in PG4180 remain undefined. In the present study, we evaluated the role of rpoN, which encodes sigma(54), in the virulence of strain PG4180. A rpoN mutant of PG4180, designated PG4180.K2, was unable to grow in M9 minimal medium; however, the addition of exogenous glutamate, glutamine or aspartate to M9 medium enabled PG4180.K2 to grow in vitro. PG4180.K2 could not induce disease symptoms or multiply in soybean plants and was defective in COR production and cor gene expression. Furthermore, PG4180.K2 was impaired in transcription of hrpL, an alternate sigma factor that mediates expression of genes in the type III secretion system of P. syringae. PG4180.K2 transconjugants with a wild-type copy of rpoN were complemented for hrpL and cor gene expression, COR biosynthesis, and growth in vitro. Our results indicate that rpoN is required for growth and the expression of both chromosomal and plasmid-encoded virulence factors in P. syringae pv. glycinea PG4180.

Amino Acids↗
PubMed2001

Characterization of the lipopolysaccharide and structure of the O-specific polysaccharide of the bacterium Pseudomonas syringae pv. atrofaciens IMV 948.

Lipopolysaccharide (LPS) was isolated from the phytopathogenic bacterium Pseudomonas syringae pv. atrofaciens IMV 948 by mild extraction of the microbial cells with saline, and the properties, composition, and structure of the LPS were studied. The LPS showed low toxicity in D- galactosamine-sensitized mice and low biological activity in plants. Structural components of LPS--lipid A, core oligosaccharide, and O-specific polysaccharide (OPS)--were obtained by mild acid degradation and characterized. The lipid A contained fatty acids 3-HO-C10:0, C12:0, 2-HO-C12:0, 3-HO-C12:0, C16:0, C16:1, C18:0, and C18:1, as well as components of the hydrophilic moiety: GlcN, ethanolamine, phosphate, and phosphoethanolamine. The LPS core contained components typical of pseudomonads: glucose, rhamnose (Rha), L-glycero-D-manno-heptose, GlcN, GalN, 2-keto-3-deoxy-D-manno-octonic acid, alanine, and phosphate. The OPS consisted of L-Rha and D-GlcNAc in the ratio 4 : 1 and was structurally heterogeneous. The main pentasaccharide repeating unit of the OPS has the following structure: [structure see text]. Immunochemical studies showed that P. syringae pv. atrofaciens IMV 948 is serologically separate from other P. syringae strains, including those that have structurally similar OPS.

Chromatography, Gel↗
PubMed2005

Genetic architecture of Arabidopsis thaliana response to infection by Pseudomonas syringae.

Plant pathogens can severely reduce host yield and fitness. Thus, investigating the genetic basis of plant response to pathogens is important to further understand plant-pathogen coevolution and to improve crop production. The interaction between Arabidopsis thaliana and Pseudomonas syringae is an important model for studying the genetic basis of plant-pathogen interactions. Studies in this model have led to the discovery of many genes that differentiate a resistant from a susceptible plant. However, little is known about the genetic basis of quantitative variation in response to P. syringae. In this study, we investigate the genetic basis of three aspects of A. thaliana's response to P. syringae: symptom severity, bacterial population size and fruit production using a quantitative trait loci (QTL) analysis. We found two QTL for symptom severity and two for fruit production (possible candidate genes for observed QTL are discussed). We also found significant two-locus epistatic effect on symptom severity and fruit production. Although bacterial population size and symptom severity were strongly phenotypically correlated, we did not detect any QTL for bacterial population size. Despite the detected genetic variation observed for susceptibility, we found only a weak overall relationship between susceptibility traits and fitness, suggesting that these traits may not respond to selection.

Arabidopsis↗
PubMed2001

Effects of urate, a natural inhibitor of peroxynitrite-mediated toxicity, in the response of Arabidopsis thaliana to the bacterial pathogen Pseudomonas syringae.

Urate, a natural peroxynitrite scavenger, has been used to investigate the possible role of peroxynitrite during plant-pathogen interactions. Urate greatly reduced lesion formation in Arabidopsis leaves treated with an abiotic peroxynitrite-generating system or with a peroxynitrite solution, indicating that it can act as an effective scavenger in planta. In the interaction with the avirulent Pseudomonas syringae pv. phaseolicola (avrRPM1+), cell death in the inoculated area was strongly reduced by urate, without compromising disease resistance. In contrast, urate promoted discrete cell death in response to an isogenic Pseudomonas syringae (avrRPM1-), which did not trigger an HR when inoculated alone, and it induced resistance and arrest of pathogen growth. Scavenging of peroxynitrite did not modify the response of Arabidopsis to an avirulent strain of Xanthomonas campestris pv campestris, that showed a high resistance to NO and peroxynitrite. Our data indicate that peroxynitrite plays a significant role in the responses of plants to Pseudomonas syringae.

Arabidopsis↗
PubMed1998

Structure of the O polysaccharide and immunochemical relationships between the lipopolysaccharides of Pseudomonas syringae pathovar tomato and pathovar maculicola.

O polysaccharides (OPS) of the lipopolysaccharides (LPS) of Pseudomonas syringae pathovar tomato GSPB 483 and pathovar maculicola IMV 381 were studied by 1H-NMR and 13C-NMR spectroscopy, including two-dimensional COSY, rotating-frame NOE spectroscopy (ROESY), and H-detected 1H,13C heteronuclear multiple-quantum coherence (HMQC) experiments. The OPS from both strains were shown to be chemically identical. Two structurally different types of repeating units (O repeats 1 and 2) were elucidated in each OPS. The minor O repeat is a pentasaccharide having the structure 2. The same structure has been reported earlier for some other OPS of P. syringae. The major O repeat is a hexasaccharide with the novel structure 1 which is distinguished from 2 by the presence of the second lateral residue of 3-acetamido-3,6-dideoxy-D-galactose (D-Fuc3NAc) and by a different position of substitution of one of the L-rhamnose (Rha) residues in the backbone. [structures: see text] Structural and serological diversity of OPS of strains belonging to P. syringae pv. tomato and pv. maculicola and phylogenetic relatedness of the strains are discussed.

Carbohydrate Conformation↗
PubMedDate not supplied

Recognition of the avirulence gene avrB from Pseudomonas syringae pv. glycinea by Arabidopsis thaliana.

The response of Arabidopsis thaliana land race Columbia to the bacterial pathogen Pseudomonas syringae pv. maculicola 4326 harboring cloned avirulence genes avrB and avrC from P. syringae pv. glycinea and avrA and avrD from P. syringae pv. tomato was examined. Only avrB was recognized by Columbia, as evidenced by attenuation of disease symptoms, slower bacterial multiplication in planta, and differentially greater induction of mRNA for several defense-related genes. This contrasts with two A. thaliana land races where P. s. pv. maculicola strains containing avrB were not recognized. These plants showed typical disease symptoms, and bacterial multiplication in planta was not reduced in response to P. s. pv. maculicola containing avrB. In addition, there was no differential induction of defense-related mRNAs in these susceptible land races after infiltration with bacteria containing or lacking avrB. These results extend previous observations that avirulence genes from pathogens of one host plant can be recognized by "nonhost" plants and provide the genetic framework for analysis of the plant-specified response to the bacterial avrB gene product in A. thaliana.

Arabidopsis↗