Premium
Identification of novel hrp ‐regulated genes through functional genomic analysis of the Pseudomonas syringae pv. tomato DC3000 genome
Author(s) -
ZwieslerVollick Julie,
PlovanichJones Anne E.,
Nomura Kinya,
Bandyopadhyay Sruti,
Joardar Vinita,
Kunkel Barbara N.,
He Sheng Yang
Publication year - 2002
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1046/j.1365-2958.2002.02964.x
Subject(s) - pseudomonas syringae , biology , effector , gene , operon , genetics , type three secretion system , genome , promoter , arabidopsis , gene expression , virulence , microbiology and biotechnology , mutant
Summary Pseudomonas syringaepv.tomato(Pst) strain DC3000 infects the model plantsArabidopsis thalianaand tomato, causing disease symptoms characterized by necrotic lesions surrounded by chlorosis. One mechanism used byPstDC3000 to infect host plants is the type III protein secretion system, which is thought to deliver multiple effector proteins to the plant cell. The exact number of type III effectors inPstDC3000 or any other plant pathogenic bacterium is not known. All known type III effector genes ofP. syringaeare regulated by HrpS, an NtrC family protein, and the HrpL alternative sigma factor, which presumably binds to a conservedciselement (called the ‘hrp box’) in the promoters of type III secretion‐associated genes. In this study, we designed a search motif based on the promoter sequences conserved in 12 publishedhrpoperons and putative effector genes inPstDC3000. Seventy‐three predicted genes were retrieved from the January 2001 release of thePstDC3000 genome sequence, which had 95% genome coverage. The expression of the 73 genes was analysed by microarray and Northern blotting, revealing 24 genes/operons (including eight novel genes), the expression of which was consistently higher inhrp‐inducing minimal medium than in nutrient‐rich Luria–Bertani broth. Expression of all eight genes was dependent on thehrpSgene. Most were also dependent on thehrpLgene, but at least one was dependent on thehrpSgene, but not on thehrpLgene. An AvrRpt2‐based type III translocation assay provides evidence that some of thehrpS ‐regulated novel genes encode putative effector proteins.