Dataset Information

Cultivar-specific avirulence and virulence functions assigned to avrPphF in Pseudomonas syringae pv. phaseolicola, the cause of bean halo-blight disease.

ABSTRACT: The avrPphF gene was cloned from Pseudomonas syringae pathovar phaseolicola (PPH:) races 5 and 7, based on its ability to confer avirulence towards bean cultivars carrying the R1 gene for halo-blight resistance, such as Red Mexican. avrPphF comprised two open reading frames, which were both required for function, and was located on a 154 kb plasmid (pAV511) in PPH: Strain RW60 of PPH:, lacking pAV511, displayed a loss in virulence to a range of previously susceptible cultivars such as Tendergreen and Canadian Wonder. In Tendergreen virulence was restored to RW60 by avrPphF alone, whereas subcloned avrPphF in the absence of pAV511 greatly accelerated the hypersensitive resistance reaction caused by RW60 in Canadian Wonder. A second gene from pAV511, avrPphC, which controls avirulence to soybean, was found to block the activity of avrPphF in Canadian Wonder, but not in Red Mexican. avrPphF also conferred virulence in soybean. The multiple functions of avrPphF illustrate how effector proteins from plant pathogens have evolved to be recognized by R gene products and, therefore, be classified as encoded by avirulence genes.

SUBMITTER: Tsiamis G

PROVIDER: S-EPMC313945 | biostudies-literature | 2000 Jul

REPOSITORIES: biostudies-literature

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Publications

Cultivar-specific avirulence and virulence functions assigned to avrPphF in Pseudomonas syringae pv. phaseolicola, the cause of bean halo-blight disease.

Tsiamis G G Mansfield J W JW Hockenhull R R Jackson R W RW Sesma A A Athanassopoulos E E Bennett M A MA Stevens C C Vivian A A Taylor J D JD Murillo J J

The EMBO journal 20000701 13

The avrPphF gene was cloned from Pseudomonas syringae pathovar phaseolicola (PPH:) races 5 and 7, based on its ability to confer avirulence towards bean cultivars carrying the R1 gene for halo-blight resistance, such as Red Mexican. avrPphF comprised two open reading frames, which were both required for function, and was located on a 154 kb plasmid (pAV511) in PPH: Strain RW60 of PPH:, lacking pAV511, displayed a loss in virulence to a range of previously susceptible cultivars such as Tendergree ...[more]

PMID: 10880434

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Project description:BackgroundPseudomonas syringae pv. phaseolicola 1448a (P. syringae 1448a), the causative agent of bean halo blight, is a bacterium capable of occupying diverse biological niches. Under conditions of iron starvation P. syringae 1448a secretes siderophores for active uptake of iron. The primary siderophore of P. syringae 1448a is pyoverdine, a fluorescent molecule that is assembled from amino acid precursors by non-ribosomal peptide synthetase (NRPS) enzymes. Whereas other species of Pseudomonas often exhibit structural variations in the pyoverdine produced by different strains, all P. syringae pathovars previously tested have been found to make an identical pyoverdine molecule. P. syringae 1448a also appears to have the genetic potential to make two secondary siderophores, achromobactin and yersiniabactin, each of which has previously been detected in different P. syringae pathovars.ResultsFive putative pyoverdine NRPS genes in P. syringae 1448a were characterized in-silico and their role in pyoverdine biosynthesis was confirmed by gene knockout. Pyoverdine was purified from P. syringae 1448a and analyzed by MALDI-TOF and MS/MS spectroscopy. Peaks were detected corresponding to the expected sizes for the pyoverdine structure previously found in other P. syringae pathovars, but surprisingly P. syringae 1448a appears to also produce a variant pyoverdine species that has an additional 71 Da monomer incorporated into the peptide side chain. Creation of pyoverdine null mutants of P. syringae 1448a revealed that this strain also produces achromobactin as a temperature-regulated secondary siderophore, but does not appear to make yersiniabactin. Pyoverdine and achromobactin null mutants were characterized in regard to siderophore production, iron uptake, virulence and growth in iron limited conditions.ConclusionsThis study provides the first evidence of a P. syringae pathovar producing a side chain variant form of pyoverdine. We also describe novel IC₅₀ and liquid CAS assays to quantify the contribution of different siderophores across a range of iron starvation conditions, and show that although achromobactin has potential to contribute to fitness its contribution is masked by the presence of pyoverdine, which is a significantly more effective siderophore. Neither pyoverdine nor achromobactin appear to be required for P. syringae 1448a to cause bean halo blight, indicating that these siderophores are not promising targets for crop protection strategies.

Dataset Information

Cultivar-specific avirulence and virulence functions assigned to avrPphF in Pseudomonas syringae pv. phaseolicola, the cause of bean halo-blight disease.

Publications

Cultivar-specific avirulence and virulence functions assigned to avrPphF in Pseudomonas syringae pv. phaseolicola, the cause of bean halo-blight disease.

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