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

• Author(s): Lindow, Steven; Purcell, Alexander; Feil, Helene;
• Abstract: Attachment of Xylella fastidiosa to xylem vessels and insect vectors may be required for virulence and transmission; therefore we have individually disrupted fimA, fimF, xadA, and hecA to assess their role in adhesion to plants and in the disease process. We performed adhesion assays using each mutant and wild-type separately as well as combination of two of the mutants and observation of the phenotypes of these mutants under a scanning electron microscope is underway. Patterns of cell adhesion and aggregation of mutants on surfaces lead us to hypothesize that fimA and fimF are important in cell-to-cell aggregation while xadA and hecA are involved in the first steps of adhesion of bacteria to the plant host. Rooted grapevine cuttings were inoculated with FimA-, FimF-, XadA-, HecA-, and wild-type X. fastidiosa Temecula or STL. A higher incidence and severity of disease was observed in vines inoculated with the wild-type X. fastidiosa strain compared with FimA-, FimF-, XadA- or HecA- mutant strains. Similarly, wild-type strain STL strain of X. fastidiosa resulted in more vines with symptoms than FimA-, FimF- or XadA- mutants of this strain indicating that the process of attachment appears to involve similar genes in both the Temecula and STL strains. It thus appears that successful colonization of plants by X. fastidiosa requires both cell-to-cell and cell-to-surface attachment. To distinguish the various mutants from each other in mixed inoculations and to determine what factors affect attachment of the mutants we have constructed disrupted fimA vectors for use in a gfp marked Xylella fastidiosa. This will allow us to distinguish the FimA- cells from other cells in a mixture adhesion assay using fluorescence microsopy and to follow these cells in grape following inoculation with these mutants. Because hecA is a large gene, we are also disrupting various locations within the HecA gene. We will test these different HecA- mutants in inoculation experiments to determine the role of HecA in virulence of X. fastidiosa to grape.
• Publication Date: Dec 2004
• Journal: 2004 Pierce's Disease Research Symposium