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Poster: Molecular & Cellular Plant-Microbe Interactions: MPMI


The chemotaxis regulator pilG of Xylella fastidiosa is required for virulence in Vitis vinifera grapevines
H. LIN (1), X. Shi (2) (1) USDA-ARS, U.S.A.; (2) USDA-ARS, U.S.A.

Xylella fastidiosa is a Gram-negative, xylem-limited pathogenic bacterium that causes Pierce’s disease of grapevines. Type IV pili of X. fastidiosa are regulated by pilG, a chemotaxis regulator in Pil-Chp operon involving signal transduction pathways. To elucidate the role of pilG in twitching motility and pathogenicity, phenotypes of wild type, pilG-mutant and a complementary strain were characterized. While in vitro studies showed that all tested strains had similar growth curves, mutant XfΔpliG exhibited a twitching defective phenotype and significant reduction in biofilm formation and cell-cell aggregation. Greenhouse in planta experiment further confirmed that grapevines infected with XfΔpilG showed very mild PD symptoms whereas grapevines inoculated with X. fastidiosa wild type and XfΔpilG-C developed typical PD symptoms. These results demonstrate that pilG of X. fastidiosa is required for twitching motility and full virulence.