Submitted to: European Journal of Plant Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/19/2017
Publication Date: 7/11/2017
Citation: Shi, X., Lin, H. 2017. The chemotaxis regulator pilG of Xylella fastidiosa is required for virulence in Vitis vinifera grapevines. European Journal of Plant Pathology. doi: 10.1007/s10658-017-1282-x.
Interpretive Summary: Xylella fastidiosa (Xf) causes Pierce's disease (PD) of grapevines. To understand pathogenicity of Xf, genetic analyses were conducted with a of wild type and a mutant strain of Xf with defective PilG, a virulence gene that is predicted to play a key role for PD. Greenhouse experiments indicated that grapevines inoculated with the mutant strain showed no PD symptoms compared to grapevines infected with Xf wild type. This study confirms that PilG is a key virulence gene that is required to develop PD in grapevines.
Technical Abstract: Type IV pili of X. fastidiosa are regulated by pilG, a response regulator protein putatively involved in chemotaxis-like operon sensing stimuli through signal transduction pathways. To elucidate roles of pilG in pathogenicity of X. fastidiosa, the pilG-deletion mutant and complementary strain containing native pilG were generated. While all tested strains had similar growth curves in vitro, pilG mutant showed significant reduction in cell-matrix adherence and biofilm production compared with wild type X. fastidiosa and Xf'pilG-C. The genes pilE, pilU, pilT, and pilS were down-regulated in pilG mutant when compared with wild type X. fastidiosa and its complement strain. No Pierce’s disease symptoms were observed in grapevines inoculated with pilG mutant whereas grapevines inoculated with wild type X. fastidiosa and complement strain developed typical PD symptoms. The results indicate that pilG is required for virulence of X. fastidiosa in grapevines.