CHARACTERIZATION OF REGULATORY PATHWAYS CONTROLLING VIRULENCE IN XYLELLA FASTIDIOSA

• Author(s): Cooksey, Donald; Dumenyo, Korsi; Shi, Xiangyang;
• Abstract: We are pursuing a strategy to identify traits important in virulence of Xylella fastidiosa (Xf) through the mutagenesis of global regulatory genes, which are known to broadly regulate virulence functions in other microbes. In addition to phenotypic characterization of such mutants, we are using whole-genome microarrays to identify which genes are regulated by these global regulators and examine these genes as putative virulence factors. Here we report a specific example of this approach that has helped to define genes involved in aggregation, biofilm formation, and virulence of Xf. In previous work with X. fastidiosa, we mutated the global regulatory gene rsmA, and found a number of genes that were over-expressed in this mutant when grown in vitro, implying that these genes are normally repressed by the post-transcriptional regulator RsmA in the wild-type. In addition, the rsmA(-) mutant formed much more biofilm than wild type. Among the genes repressed by rsmA was another regulatory gene, algU, which regulates important virulence factors in Pseudomonas. In this study, an algU::nptII mutant had reduced cell-cell aggregation, attachment, biofilm formation, and lower virulence in grapevines. DNA microarray analysis showed that 42 genes had significantly lower expression in algU::nptII than wild type, including several genes which could contribute to cell aggregation and biofilm formation, as well as other physiological processes that could contribute to virulence and survival. Thus, rsmA appears to control biofilm formation and other traits partly through its repression of the positive regulator, algU.
• Publication Date: Nov 2006
• Journal: 2006 Pierce's Disease Research Symposium