Open AccessLocation and activity of members of a family of virPphA homologues in pathovars of Pseudomonas syringae and P. savastanoi
Author(s) -
Jackson Robert W.,
Mansfield John W.,
Ammouneh Hassan,
Dutton Lindsay C.,
Wharton Becky,
OrtizBarredo Amaya,
Arnold Dawn L.,
Tsiamis George,
Sesma Ane,
Butcher Diane,
Boch Jens,
Kim Young Jin,
Martin Gregory B.,
Tegli Stefania,
Murillo Jesús,
Vivian Alan
Publication year - 2002
Publication title -
molecular plant pathology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.945
H-Index - 103
eISSN - 1364-3703
pISSN - 1464-6722
DOI - 10.1046/j.1364-3703.2002.00121.x
Subject(s) - pseudomonas syringae , biology , virulence , plasmid , phaseolus , orfs , microbiology and biotechnology , gene , open reading frame , pseudomonas , pseudomonadaceae , genetics , bacteria , botany , peptide sequence
Summary virPphAis a major determinant of the pathogenicity ofPseudomonas savastanoipv.phaseolicolatoPhaseolusbean. A family of homologues ofvirPphAwas detected in pathovars ofP.savastanoiandP.syringae. We examined the structure and activity of alleles designatedvirPphA,virPphAPgy, andvirPphAPsvfromP.savastanoipathovarsphaseolicola,glycinea, andsavastanoi, respectively, andavrPtoBfromP.syringaepv.tomato. Sequencing showed that thevirPphAPgyhomologue had a 48‐bp central deletion in the open reading frame (ORF) compared withvirPphAandvirPphAPsv, but otherwise all threeP.savastanoialleles had > 98% identity at the DNA level. By contrast, AvrPtoB fromP.syringaepv.tomatostrain DC3000 was predicted to have only 51% amino acid similarity with VirPphA. All ORFs have an upstreamhrp‐box promoter indicating potential regulation by HrpL. Each cloned homologue was introduced into theP. savastanoipv.phaseolicolastrain RW60, which lacks a native plasmid carryingvirPphAas part of a pathogenicity island (PAI), and which is not pathogenic on bean. The homologues all restored virulence, as measured by the development of water‐soaked lesions in bean pods, and increased bacterial populations in leaves compared with RW60 alone. RW60 harbouringvirPphAorvirPphAPsvelicited a strong hypersensitive reaction (HR) in soybean cv. Osumi; the presence ofavrPtoBcaused a weak HR, butvirPphAPgydid not affect the null reaction observed in soybean with RW60 alone. A second effector gene,avrPphD, was detected on the genomic clones carryingvirPphAPgyandvirPphAPsv.avrPphDwas also present in bothP.savastanoipv.phaseolicolaandP.syringaepv.tomato, but elsewhere in their genomes. Comparison of the genomic locations ofvirPphAand other effectors found in theP. savastanoipv.phaseolicolaPAI revealed the greatest divergence of the sequences surroundingvirPphAto be inP.syringaepv.tomato .