Poster: Plant Pathogen/Symbiont Interactions

Abs # 726: Molecular interplay between Arabidopsis nonhost resistance and Pseudomonas virulence

Presenter:	Zhou, Jian-Min , jzhou@ksu.edu
Authors	Zhou, Jian-Min  (A)   Kang, Li  (A)   Tang, Xiaoyan  (A)
Affiliations:	(A): Kansas State University

Nonhost resistance is prevalent between plants and specialized phytopathogens. The Arabidopsis NHO1 gene is required nonspecifically for resistance to at least three Pseudomonas syringae pathovars that are nonpathogenic on Arabidopsis. Interestingly, the nho1 mutant also supports the growth of P. fluorescens, a plant associating, nonpathogenic bacterium. However, NHO1 is completely ineffective against virulent Pseudomonas bacteria. We hypothesize that NHO1 define a general resistance and that virulent bacteria possess specific mechanisms to overcome/evade this resistance. We recently cloned NHO1 and showed that it encodes a glycerol kinase. Strikingly, NHO1 transcripts were induced by nonhost strains of P. syringae but suppressed by the virulent bacterium P. s. pv. tomato DC3000. DC3000 appeared to actively manipulate the jasmonate signaling pathway in the plant to suppress NHO1 expression. The suppression of NHO1 was relevant to bacterial virulence, because overexpression of NHO1 in plants reduced DC3000 bacterial growth. NHO1 is also required for complete gene-for-gene resistance mediated by at least four disease resistance genes, as the nho1 mutation compromised the resistance. Interestingly, DC3000 bacteria carrying the avrB gene induces, rather than suppresses, NHO1 expression. Thus the results demonstrated a strong interplay between bacterial virulence and the NHO1-mediated defense mechanism. A model depicting such interplay will be presented.