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A Novel Multidomain Polyketide Synthase Is Essential for Zeamine Production and the Virulence of Dickeya zeae

October 2011 , Volume 24 , Number  10
Pages  1,156 - 1,164

Jianuan Zhou,1 Haibao Zhang,2 Jien Wu,2 Qiongguang Liu,1 Pinggen Xi,1 Jasmine Lee,2 Jinling Liao,1 Zide Jiang,1 and Lian-Hui Zhang2

1Department of Plant pathology, South China Agricultural University, Guangzhou 510642, People's Republic of China; 2Institute of Molecular and Cell Biology, 61 Biopolis Drive, Singapore 138673

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Accepted 26 May 2011.

Dickeya zeae is the causal agent of the rice foot rot disease, but its mechanism of infection remains largely unknown. In this study, we identified and characterized a novel gene designated as zmsA. The gene encodes a large protein of 2,346 amino acids in length, which consists of multidomains arranged in the order of N-terminus, β-ketoacyl synthase, acyl transferase, acyl carrier protein, β-ketoacyl reductase, dehydratase. This multidomain structure and sequence alignment analysis suggest that ZmsA is a member of the polyketide synthase family. Mutation of zmsA abolished antimicrobial activity and attenuated the virulence of D. zeae. To determine the relationship between antimicrobial activity and virulence, active compounds were purified from D. zeae EC1 and were structurally characterized. This led to identification of two polyamino compounds, i.e., zeamine and zeamine II, that were phytotoxins and potent antibiotics. These results have established the essential role of ZmsA in zeamine biosynthesis and presented a new insight on the molecular mechanisms of D. zeae pathogenicity.

© 2011 The American Phytopathological Society