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ClpXP Protease Regulates the Type III Secretion System of Dickeya dadantii 3937 and Is Essential for the Bacterial Virulence

July 2010 , Volume 23 , Number  7
Pages  871 - 878

Yan Li,1,2 Akihiro Yamazaki,2 Lifang Zou,2 Eulandria Biddle,2 Quan Zeng,2 Yongjun Wang,3 Haiping Lin,3 Qi Wang,1 and Ching-Hong Yang2

1Department of Plant Pathology, College of Agronomy & Biotechnology, China Agricultural University, Beijing 100193, China; 2Department of Biological Sciences, University of Wisconsin--Milwaukee 53211, U.S.A.; 3College of Forestry and Biotechnology, Zhejiang Forestry University, Lin'an 311300, China

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Accepted 24 March 2010.

The type III secretion system (T3SS) is considered one of the major virulence factors in many bacterial pathogens. This report demonstrates that RssB, ClpXP, and RpoS play a role in T3SS regulation of Dickeya dadantii 3937. ClpP is a serine-type protease which associates with the ClpX chaperone to form a functional Clp proteolytic complex for degradation of proteins. With the assistance of recognition factor RssB, ClpXP degrades the RpoS sigma factor. RpoS positively regulates the expression of the rsmA gene encoding an RNA-binding regulatory protein. By interacting with the hrpL mRNA, RsmA reduces HrpL production and downregulates the T3SS genes in the HrpL regulon. In addition, ClpXP, RssB, and RpoS affect pectinolytic enzyme production in D. dadantii 3937, probably through RsmA. The ClpXP and RssB proteins are essential for bacterial virulence.

© 2010 The American Phytopathological Society