Open AccessThe Pseudomonas syringae phytotoxin coronatine promotes virulence by overcoming salicylic acid‐dependent defences in Arabidopsis thaliana
Author(s) -
BROOKS DAVID M.,
BENDER CAROL L.,
KUNKEL BARBARA N.
Publication year - 2005
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 - 10.1111/j.1364-3703.2005.00311.x
Subject(s) - pseudomonas syringae , coronatine , phytotoxin , arabidopsis thaliana , biology , mutant , virulence , salicylic acid , jasmonate , methyl jasmonate , microbiology and biotechnology , arabidopsis , pathogen , hypersensitive response , biochemistry , plant disease resistance , gene , toxin
SUMMARY Successful pathogen infection likely involves the suppression of general antimicrobial host defences. One Pseudomonas syringae virulence factor proposed to act in this manner is coronatine (COR), a phytotoxin believed to function as an analogue of one or more jasmonates, a family of plant growth regulators. COR biosynthetic (COR − ) mutants of P. syringae pv. tomato strain DC3000 exhibit reduced virulence on Arabidopsis thaliana and tomato . In the present study, three genetically and biochemically defined COR − mutants of DC3000 were used to explore potential effects of COR and its precursors, coronafacic acid (CFA) and coronamic acid (CMA), on defence signalling pathways in A. thaliana . Inoculation with wild‐type DC3000 resulted in the accumulation of several jasmonate‐responsive transcripts, whereas infection with a mutant strain that accumulates CFA, which is structurally similar to methyl jasmonate (MeJA), did not. Thus, COR, but not CFA, stimulates jasmonate signalling during P. syringae infection of A. thaliana . The ability of the COR − mutants to grow to high levels in planta was fully restored in A. thaliana lines deficient for salicylic acid (SA) accumulation. Although the COR − mutants grew to high levels in SA‐deficient plants, disease symptoms were reduced in these plants. Collectively, these results indicate that COR is required both for overcoming or suppressing SA‐dependent defences during growth in plant tissue and for normal disease symptom development in A. thaliana .