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Xanthomonas campestris pv. vesicatoria Effector AvrBsT Induces Cell Death in Pepper, but Suppresses Defense Responses in Tomato

August 2010 , Volume 23 , Number  8
Pages  1,069 - 1,082

Nak Hyun Kim, Hyong Woo Choi, and Byung Kook Hwang

Laboratory of Molecular Plant Pathology, School of Life Sciences and Biotechnology, Korea University, Anam-dong, Sungbuk-ku, Seoul 136-713, Republic of Korea

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Accepted 29 March 2010.

A type III effector protein, AvrBsT, is secreted into plant cells from Xanthomonas campestris pv. vesicatoria Bv5-4a, which causes bacterial spot disease on pepper (Capsicum annuum) and tomato (Solanum lycopersicum). To define the function and recognition of AvrBsT in the two host plants, avrBsT was introduced into the virulent pepper strain X. campestris pv. vesicatoria Ds1. Expression of AvrBsT in Ds1 rendered the strain avirulent to pepper plants. Infection of pepper leaves with Ds1 (avrBsT) expressing AvrBsT but not with near-isogenic control strains triggered a hypersensitive response (HR) accompanied by strong H2O2 generation, callose deposition, and defense-marker gene expressions. Mutation of avrBsT, however, compromised HR induction by X. campestris pv. vesicatoria Bv5-4a, suggesting its avirulence function in pepper plants. In contrast, AvrBsT acted as a virulence factor in tomato plants. Growth of strains Ds1 (avrBsT) and Bv5-4a ΔavrBsT was significantly enhanced and reduced, respectively, in tomato leaves. X. campestris pv. vesicatoria-expressed AvrBsT also significantly compromised callose deposition and defense-marker gene expression in tomato plants. Together, these results suggest that the X. campestris pv. vesicatoria type III effector AvrBsT is differentially recognized by pepper and tomato plants.

© 2010 The American Phytopathological Society