Identify key virulence gene as a control target to mitigate Pierce’s disease of grape

Abstract

Xylella fastidiosa (Xf) is an important phytopathogen that infects a number of economically important crops including citrus, almonds, coffee and olive. The Xf Temecula1 strain causes Pierce’s disease of grapevines, a devastating disease to the viticulture industry. We deleted the pilG in Xf (XfΔpliG) and found that the mutant strain was avirulent. Type IV pili of Xyella fastidiosa are regulated by pilG, a response regulator protein putatively involved in chemotaxis-like operon sensing stimuli through signal transduction pathways. Results demonstrated that XfΔpliG showed significant reduction in cell-matrix adherence and biofilm production compared with wild type X. fastidiosa. In planta experiments showed that no Pierce’s disease (PD) symptoms were observed in grapevines inoculated with XfΔpilG, whereas grapevines inoculated with the wild type X. fastidiosa and complemented strain XfΔpilG-C developed typical PD symptoms. These results suggest that pilG plays a key role in X. fastidiosa virulence. To develop a target-basis of therapeutic control of X. fastidiosa virulence, we evaluate the effect of putative anti-virulence molecules on the target gene. Our studies identified several small molecules that exhibit effective suppression on twitching motility and virulence traits under in vitro and in planta evaluation. This study facilitates the development of a novel target-basis strategy to mitigate the Pierce’s disease of grapevines.