DNA MICROARRAY AND MUTATIONAL ANALYSIS TO IDENTIFY VIRULENCE GENES IN XYLELLA FASTIDIOSA

• Author(s): Cooksey, Donald; Dumenyo, Korsi; Hernandez, Rufina;
• Abstract: The development of successful management and control strategies of Pierces disease of grape requires the identification of virulence and pathogenicity genes and determining how they functions to control the disease development process. Based on the presumption that biofilm formation is a major pathogenicity factor of Xylella and that it may play a major role in the disease causing process, we have been studying the factors genetic and environmental that affect biofilm formation by Xylella fastidiosa. We have identified that, Bovine serum albumen, a component of PW medium specifically inhibits biofilm formation in X. fastidiosa and that this inhibition is BSA concentration dependent. Because of its effect on the biofilm formation in vitro, we are studying the expression profiles of X. fastidiosa genes in the presence and absence of BSA in the media. We have also identified a global regulatory gene, rsmA (rsm = regulator of secondary metabolism) that control biofilm. An rsmA-deficient strain of X. fastidiosa forms more biofilm in vitro than the wild type. In a preliminary nylon membrane DNA macroarray experiment using about a 100 select candidate pathogenicity genes, we have determined an increased expression of 15 genes in the mutant when compared to the wild type parent. We are now using full genome microarrays of Xylella fastidiosa to catalogue the genes whose expressions are controlled by either rsmA or BSA. The results from these ongoing analyses using both approaches should help us catalogue X. fastidiosa genes which may be involved in pathogenicity and biofilm formation. Subsequent genetic analysis of the genes to be identified should give us some understanding of not only how pathogenicity is regulated in this bacterium but also how to tackle the problems posed by Pierces disease.
• Publication Date: Dec 2004
• Journal: 2004 Pierce's Disease Research Symposium