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The Pseudomonas syringae avrRpt2 Gene Product Promotes Pathogen Virulence from Inside Plant Cells

December 2000 , Volume 13 , Number  12
Pages  1,312 - 1,321

Zhongying Chen , 1 Andrew P. Kloek , 1 Jens Boch , 1 Fumiaki Katagiri , 2 and Barbara N. Kunkel 1

1Department of Biology, Washington University, St. Louis, MO 63130, U.S.A.; 2Department of Biological Sciences, University of Maryland-Baltimore County, Baltimore 21250, U.S.A.

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Accepted 9 August 2000.

Several bacterial avr genes have been shown to contribute to virulence on susceptible plants lacking the corresponding resistance (R) gene. The mechanisms by which avr genes promote parasitism and disease, however, are not well understood. We investigated the role of the Pseudomonas syringae pv. tomato avrRpt2 gene in pathogenesis by studying the interaction of P. syringae pv. tomato strain PstDC3000 expressing avrRpt2 with several Arabidopsis thaliana lines lacking the corresponding R gene, RPS2. We found that PstDC3000 expressing avrRpt2 grew to significantly higher levels and often resulted in the formation of more severe disease symptoms in ecotype No-0 plants carrying a mutant RPS2 allele, as well as in two Col-0 mutant lines, cpr5 rps2 and coi1 rps2, that exhibit enhanced resistance. We also generated transgenic A. thaliana lines expressing avrRpt2 and demonstrated, by using several different assays, that expression of avrRpt2 within the plant also promotes virulence of PstDC3000. Thus, AvrRpt2 appears to promote pathogen virulence from within the plant cell.

© 2000 The American Phytopathological Society