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Identification of an Operon, Pil-Chp, That Controls Twitching Motility and Virulence in Xylella fastidiosa

October 2011 , Volume 24 , Number  10
Pages  1,198 - 1,206

Luciana Cursino,1,2 Cheryl D. Galvani,1,2 Dusit Athinuwat,1 Paulo A. Zaini,1,3 Yaxin Li,1 Leonardo De La Fuente,1,4 Harvey C. Hoch,1 Thomas J. Burr,1 and Patricia Mowery2

1Department of Plant Pathology and Plant-Microbe Biology, Cornell University–New York State Agricultural Experiment Station, Geneva, NY 14456, U.S.A.; 2Department of Biology, Hobart and William Smith Colleges, Geneva, NY 14456, U.S.A.; 3Department of Biochemistry, University of São Paulo, SP 05508-000, Brazil; 4Department of Entomology and Plant Pathology, Auburn University, Auburn, AL 36849, U.S.A.

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Accepted 10 June 2011.

Xylella fastidiosa is an important phytopathogenic bacterium that causes many serious plant diseases, including Pierce's disease of grapevines. Disease manifestation by X. fastidiosa is associated with the expression of several factors, including the type IV pili that are required for twitching motility. We provide evidence that an operon, named Pil-Chp, with genes homologous to those found in chemotaxis systems, regulates twitching motility. Transposon insertion into the pilL gene of the operon resulted in loss of twitching motility (pilL is homologous to cheA genes encoding kinases). The X. fastidiosa mutant maintained the type IV pili, indicating that the disrupted pilL or downstream operon genes are involved in pili function, and not biogenesis. The mutated X. fastidiosa produced less biofilm than wild-type cells, indicating that the operon contributes to biofilm formation. Finally, in planta the mutant produced delayed and less severe disease, indicating that the Pil-Chp operon contributes to the virulence of X. fastidiosa, presumably through its role in twitching motility.

© 2011 The American Phytopathological Society