ROLE OF ATTACHMENT OF XYLELLA FASTIDIOSA TO GRAPE AND INSECTS IN ITS VIRULENCE AND TRANSMISSIBILITY

• Author(s): Lindow, Steven; Purcell, Alexander;
• Abstract: Xylella fastidiosa causes Pierce's disease, a serious disease of grape, citrus variegated chlorosis, almond and oleander leaf scorches, and many other similar diseases. Although the complete genome sequences of several strains of this organism are now available, the function of most genes in this organism, especially those conferring virulence, is lacking. We are elucidating the role of fimbriae and adhesins in the pathogenicity of X. fastidiosa to grape, in the attachment to grape or to insect mouthparts, and in the transmissibility of the bacteria to grape via insects. We are also investigating the role of the non-fimbrial adhesins (HecA, B, C, and XadA) in the attachment process because we believe that these genes are important in the early steps of adhesion in bacterial cell-host cells surface attachment. We were successful in producing XadA- mutants of X. fastidiosa strains Temecula and STL and conducted various adhesion assays comparing wild-type to XadA- mutant cells phenotypes. Polymerase chain reaction and southern blot analyses of the mutants indicated that a double crossover event had occurred exclusively within the xadA gene, replacing the chromosomal gene with the disrupted gene and abolishing production of the corresponding protein, XadA. Scanning electron microscopy revealed that attachment to glass was inhibited for the XadA- mutants of X. fastidiosa when compared with the parental strain. XadA- mutants of X. fastidiosa remained pathogenic to grapevines, but further characterization of virulence and insect transmissibility are underway.
• Publication Date: Aug 2003
• Journal: 2003 Pierce's Disease Research Symposium