Xyloglucan processing by Xanthomonas plant pathogens and its role in the activation of virulence factors.

Xyloglucans are highly substituted polysaccharides found in the primary cell walls of all vascular plants, acting as a first barrier against pathogens. Herein, we revealed that the diverse and economically relevant Xanthomonas phytopathogens are endowed with an enzymatic system targeting xyloglucans. Furthermore, we demonstrate that the products generated by this system elicit the expression of multiple virulence factors including the type III secretion system, a membrane-embedded machinery to deliver effector proteins into the host cells. Together, these findings illuminate the intricate enzymatic apparatus employed by Xanthomonas to break down xyloglucans and connect this system to the pathogenesis through activating the expression of key virulence factors. mRNA profiles of X. citri grown on minimal media XVM2m containing xyloglucan-oligosaccharides relative to the media XVM2m containing glucose as a reference.