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The Pseudomonas syringae type III effector AvrRpt2 functions downstream or independently of SA to promote virulence on Arabidopsis thaliana
Author(s) -
Chen Zhongying,
Kloek Andrew P.,
Cuzick Alayne,
Moeder Wolfgang,
Tang Dingzhong,
Innes Roger W.,
Klessig Daniel F.,
McDowell John M.,
Kunkel Barbara N.
Publication year - 2004
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1111/j.1365-313x.2003.01984.x
Subject(s) - pseudomonas syringae , virulence , biology , effector , pathogen , arabidopsis , hypersensitive response , microbiology and biotechnology , arabidopsis thaliana , gene , plant disease resistance , genetics , mutant
Summary AvrRpt2, a Pseudomonas syringae type III effector protein, functions from inside plant cells to promote the virulence of P. syringae pv. tomato strain DC3000 ( Pst DC3000) on Arabidopsis thaliana plants lacking a functional copy of the corresponding RPS2 resistance gene. In this study, we extended our understanding of AvrRpt2 virulence activity by exploring the hypothesis that AvrRpt2 promotes Pst DC3000 virulence by suppressing plant defenses. When delivered by Pst DC3000, AvrRpt2 suppresses pathogen‐related ( PR ) gene expression during infection, suggesting that AvrRpt2 suppresses defenses mediated by salicylic acid (SA). However, AvrRpt2 promotes Pst DC3000 growth on transgenic plants expressing the SA‐degrading enzyme NahG, indicating that AvrRpt2 does not promote bacterial virulence by modulating SA levels during infection. AvrRpt2 general virulence activity does not depend on the RPM1 resistance gene, as mutations in RPM1 had no effect on AvrRpt2‐induced phenotypes. Transgenic plants expressing AvrRpt2 displayed enhanced susceptibility to Pst DC3000 strains defective in type III secretion, indicating that enhanced susceptibility of these plants is not because of suppression of defense responses elicited by other type III effectors. Additionally, avrRpt2 transgenic plants did not exhibit increased susceptibility to Peronospora parasitica and Erysiphe cichoracearum , suggesting that AvrRpt2 virulence activity is specific to P. syringae .