Xanthomonas citri pv. citri pathotypes: LPS structure and function as microbe-associated molecular patterns

Xanthomonas citri pv. citri is the pathogen responsible for the Asiatic citrus canker, one of the most serious diseases of citrus worldwide. The lipopolysaccharide (LPS) molecule was demonstrated to be involved in X. citri pv. citri virulence. Despite the enormous progress made in the investigation of molecular mechanisms responsible for bacterial pathogenicity, the determination of the detailed LPS structure-activity relationship still remains limited as the current knowledge is mainly based on structural determination of one X. citri pv. citri strain. Since X. citri pv. citri strains were distinguished into three main pathogenicity groups, we characterized the full structure of the LPS from two pathotypes differing in their host range specificity, revealing an intriguing different LPS O-chain structure. We also tested the LPSs and the isolated lipid A moieties for their capability to act as Microbe-Associated Molecular Patterns in Arabidopsis thaliana. We demonstrated that both LPS/lipid As were able to induce ROS accumulation but no differences were observed among the two pathotypes.