Showing papers by "Alan Collmer published in 2003"
TL;DR: The complete genome sequence of the model bacterial pathogen Pseudomonas syringae pathovar tomato DC3000 (DC3000), which is pathogenic on tomato and Arabidopsis thaliana, is reported and 1,159 genes unique to DC3000 are revealed, of which 811 lack a known function.
Abstract: We report the complete genome sequence of the model bacterial pathogen Pseudomonas syringae pathovar tomato DC3000 (DC3000), which is pathogenic on tomato and Arabidopsis thaliana. The DC3000 genome (6.5 megabases) contains a circular chromosome and two plasmids, which collectively encode 5,763 ORFs. We identified 298 established and putative virulence genes, including several clusters of genes encoding 31 confirmed and 19 predicted type III secretion system effector proteins. Many of the virulence genes were members of paralogous families and also were proximal to mobile elements, which collectively comprise 7% of the DC3000 genome. The bacterium possesses a large repertoire of transporters for the acquisition of nutrients, particularly sugars, as well as genes implicated in attachment to plant surfaces. Over 12% of the genes are dedicated to regulation, which may reflect the need for rapid adaptation to the diverse environments encountered during epiphytic growth and pathogenesis. Comparative analyses confirmed a high degree of similarity with two sequenced pseudomonads, Pseudomonas putida and Pseudomonas aeruginosa, yet revealed 1,159 genes unique to DC3000, of which 811 lack a known function.
835 citations
TL;DR: It is established that GacA, located at the top in a regulatory cascade in DC3000, functions as a central regulator by controlling an assortment of transcriptional and posttranscriptional factors.
Abstract: Concerted investigations of factors affecting host-pathogen interactions are now possible with the model plant Arabidopsis thaliana and its model pathogen Pseudomo-nas syringae pv. tomato DC3000, a...
173 citations
TL;DR: HopPtoM is a type III effector that, among known plant pathogen effectors, is unusual in making a major contribution to the elicitation of lesion symptoms but not growth in host tomato leaves.
Abstract: Summary Pseudomonas syringae pv. tomato DC3000 is a patho- gen of tomato and Arabidopsis that injects virulence effector proteins into host cells via a type III secretion system (TTSS). TTSS-deficient mutants have a Hrp - phenotype, that is, they cannot elicit the hypersensi- tive response (HR) in non-host plants or pathogene- sis in host plants. Mutations in effector genes typically have weak virulence phenotypes (apparently due to redundancy), but deletion of six open reading frames (ORF) in the DC3000 conserved effector locus (CEL) reduces parasitic growth and abolishes disease symptoms without affecting function of the TTSS. The inability of the D CEL mutant to cause disease symp- toms in tomato was restored by a clone expressing two of the six ORF that had been deleted: CEL ORF3 (HopPtoM) and ORF4 (ShcM). A D hopPtoM :: nptII mutant was constructed and found to grow like the wild type in tomato but to be strongly reduced in its production of necrotic lesion symptoms. HopPtoM expression in DC3000 was activated by the HrpL alter- native sigma factor, and the protein was secreted by the Hrp TTSS in culture and translocated into Arabi- dopsis cells by the Hrp TTSS during infection. Secre- tion and translocation were dependent on ShcM, which was neither secreted nor translocated but, like typical TTSS chaperones, could be shown to interact with HopPtoM, its cognate effector, in yeast two- hybrid experiments. Thus, HopPtoM is a type III effec- tor that, among known plant pathogen effectors, is unusual in making a major contribution to the elicita- tion of lesion symptoms but not growth in host tomato leaves.
101 citations
TL;DR: Comparative analyses suggest that the EEL effector genes were acquired by horizontal transfer after the acquisition of the hrp/hrc gene cluster but before the divergence of modern pathovars and that some EELs underwent transpositions yielding effector exchanges or point mutations producing effector pseudogenes after their acquisition.
Abstract: Pseudomonas syringae is a plant pathogen whose pathogenicity and host specificity are thought to be determined by Hop/Avr effector proteins injected into plant cells by a type III secretion system. P. syringae pv. syringae B728a, which causes brown spot of bean, is a particularly well-studied strain. The type III secretion system in P. syringae is encoded by hrp (hypersensitive response and pathogenicity) and hrc (hrp conserved) genes, which are clustered in a pathogenicity island with a tripartite structure such that the hrp/hrc genes are flanked by a conserved effector locus and an exchangeable effector locus (EEL). The EELs of P. syringae pv. syringae B728a, P. syringae strain 61, and P. syringae pv. tomato DC3000 differ in size and effector gene composition; the EEL of P. syringae pv. syringae B728a is the largest and most complex. The three putative effector proteins encoded by the P. syringae pv. syringae B728a EEL—HopPsyC, HopPsyE, and HopPsyV—were demonstrated to be secreted in an Hrp-dependent manner in culture. Heterologous expression of hopPsyC, hopPsyE, and hopPsyV in P. syringae pv. tabaci induced the hypersensitive response in tobacco leaves, demonstrating avirulence activity in a nonhost plant. Deletion of the P. syringae pv. syringae B728a EEL strongly reduced virulence in host bean leaves. EELs from nine additional strains representing nine P. syringae pathovars were isolated and sequenced. Homologs of avrPphE (e.g., hopPsyE) and hopPsyA were particularly common. Comparative analyses of these effector genes and hrpK (which flanks the EEL) suggest that the EEL effector genes were acquired by horizontal transfer after the acquisition of the hrp/hrc gene cluster but before the divergence of modern pathovars and that some EELs underwent transpositions yielding effector exchanges or point mutations producing effector pseudogenes after their acquisition.
70 citations
TL;DR: Observations support the concept that the P. syringae effector proteins, rather than secretion system components, are the primary determinants of host range at both the species and cultivar levels of host specificity.
Abstract: The plant pathogenic species Pseudomonas syringae is divided into numerous pathovars based on host specificity. For example, P. syringae pv. tomato DC3000 is pathogenic on tomato and Arabidopsis, whereas P. syringae pv. syringae 61 is pathogenic on bean. The ability of P. syringae strains to elicit the hypersensitive response (HR) in non-hosts or be pathogenic (or parasitic) in hosts is dependent on the Hrp (type III secretion) system and effector proteins this system is thought to inject into plant cells. To test the role of the Hrp system in determining host range, the hrp/hrc gene cluster (hrpK through hrpR) was deleted from DC3000 and complemented in trans with the orthologous cluster from strain 61. Mutant CUCPB5114 expressing the bean pathogen Hrp system on plasmid pCPP2071 retained the ability of wild-type DC3000 to elicit the HR in bean, to grow and cause bacterial speck in tomato, and to elicit a cultivar-specific (gene-for-gene) HR in tomato plants carrying the Pto resistance gene. However, the symptoms produced in compatible tomato plants involved markedly reduced chlorosis, and CUCPB5114(pCPP2071) did not grow or produce symptoms in Arabidopsis Col-0 although it was weakly virulent in NahG Arabidopsis. A hypersensitive-like collapse was produced by CUCPB5114(pCPP2071) in Arabidopsis Col-0 at 1 x 10(7) CFU/ml, but only if the bacteria also expressed AvrB, which is recognized by the RPM1 resistance gene in Col-0 and confers incompatibility. These observations support the concept that the P. syringae effector proteins, rather than secretion system components, are the primary determinants of host range at both the species and cultivar levels of host specificity.
46 citations
01 Jan 2003
TL;DR: A hypothetical scenario of the critical factors triggering disease development and of the potential efficiency of different control strategies is reported, based on the description of possible outbreaks of this disease elsewhere in the world.
Abstract: Since the early 1990's, bacterial blight has emerged as an important disease of cantaloupe in France, particularly in the south-west but has caused epidemics in all the production regions of this country. The pathogen is a complex composed of strains identified as Pseudomonas syringae pv. aptata (70% of the strains) and the remaining resembling P. viridijlava (2%), P. s. pv. lachrymans (1%) or P. syringae in general but with no correspondence to a known pathovar. To investigate the epidemiology of this disease and to develop disease control strategies, we have attempted to identify sources of inoculum in the field, factors contributing to the explosive development of the disease, resistance of the bacterium to copper pesticides, and sources of disease resistance in Cucumis melo. Based on our observations and on the description of possible outbreaks of this disease elsewhere in the world, we report here a hypothetical scenario of the critical factors triggering disease development and of the potential efficiency of different control strategies.
38 citations
Patent•
30 Jan 2003
TL;DR: In this article, isolated proteins or polypeptides which elicit a hypersensitive response in plants, as well as isolated DNA molecules which encode the hypersensitive responses eliciting proteins, are used to impart disease resistance, stress resistance, and enhanced growth to plants or plants grown from treated seeds.
Abstract: The present invention is directed to isolated proteins or polypeptides which elicit a hypersensitive response in plants, as well as isolated DNA molecules which encode the hypersensitive response eliciting proteins or polypeptides. These isolated proteins or polypeptides and the isolated DNA molecules can be used to impart disease resistance, stress resistance, and enhanced growth to plants or plants grown from treated seeds, to control insects on plants or plants grown from treated plant seeds, to impart post-harvest disease or desiccation resistance in fruits or vegetables, to impart enhanced longevity of fruit or vegetable ripeness, to impart desiccation resistance to cuttings of ornamental plants, and/or promote early flowering of ornamental plants, either by topical application of the proteins or polypeptides or transgenic expression in recombinant plants or plant seeds.
5 citations
01 Jan 2003
TL;DR: Several novel Hops have a clear potential to modify plant signal transduction pathways, which is consistent with the predicted roles for TTSS effectors.
Abstract: The ability of Pseudomonas syringae pv. tomato DC3000 to be pathogenic on plants is dependent upon the type III secretion system (TTSS) and the effector proteins it translocates into plant cells. A draft sequence of DC3000 is currently being analysed for hop (Hrp outer protein) genes that encode TTSS substrates. Several different approaches were used to mine hop genes from the DC3000 genome. These approaches included ones that were based on linkage to other hop genes, the presence of apparent Hrp promoters, indicators of horizontal transfer, and N-terminal export-associated patterns. Many candidate hop genes were confirmed to encode TTSS-secreted proteins based on secretion and/or translocation assays. These approaches have substantially enlarged the inventory of DC3000 TTSS substrates. Hop proteins include extracellular accessory proteins that aid in translocation and effectors that are injected into plant cells. Several novel Hops have a clear potential to modify plant signal transduction pathways, which is consistent with the predicted roles for TTSS effectors. Activities of several Hops and new insights into bacterial pathogenesis of plants will be discussed.