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The Magnaporthe oryzae Avirulence Gene AvrPiz-t Encodes a Predicted Secreted Protein That Triggers the Immunity in Rice Mediated by the Blast Resistance Gene Piz-t

April 2009 , Volume 22 , Number  4
Pages  411 - 420

Wei Li,1,3 Baohua Wang,2 Jun Wu,1 Guodong Lu,2 Yajun Hu,1 Xing Zhang,4 Zhengguang Zhang,4 Qiang Zhao,1 Qi Feng,1 Hongyan Zhang,1 Zhengyi Wang,5 GuoLiang Wang,6 Bin Han,1 Zonghua Wang,2 and Bo Zhou1,5

1National Center for Gene Research & Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200233, China; 2Key Laboratory of Biopesticide and Chemical Biology, Ministry of Education, Fujian Agriculture and Forestry University, Fuzhou 350002, China; 3Graduate School of the Chinese Academy of Sciences, Beijing 100049, China; 4Department of Plant Pathology, Nanjing Agriculture University, Nanjing 210095, China; 5Biotechnology Institute, Zhejiang University, Hangzhou 310029, China; 6Department of Plant Pathology, the Ohio State University, Columbus 43210, U.S.A.

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Accepted 17 November 2008.

The Magnaporthe oryzae avirulence gene AvrPiz-t activates immunity in a gene-for-gene fashion to rice mediated by the blast resistance gene Piz-t. To dissect the molecular mechanism underlying their recognition, we initiated the cloning of AvrPiz-t using a map-based cloning strategy. The AvrPiz-t gene was delimited to an approximately 21-kb genomic fragment, in which six genes were predicted. Complementation tests of each of these six candidate genes led to the final identification of AvrPiz-t, which encodes a 108-amino-acid predicted secreted protein with unknown function and no homologues in M. oryzae or in other sequenced fungi. We found that AvrPiz-t is present in the virulent isolate GUY11 but contains a Pot3 insertion at a position 462 bp upstream from the start codon. Complementation tests of AvrPiz-t genes driven by promoters of varying length revealed that a promoter larger than 462 bp is essential to maintain the AvrPiz-t function. These results suggest that a Pot3 insertion in GUY11 might interfere with the proper function of AvrPiz-t. Additionally, we found that AvrPiz-t can suppress the programmed cell death triggered by mouse BAX protein in Nicotiana benthamiana, identifying a mechanism by which AvrPiz-t may contribute virulence of M. oryzae.

© 2009 The American Phytopathological Society