A SCREEN FOR XYLELLA FASTIDIOSA GENES INVOLVED IN TRANSMISSION BY INSECT VECTORS

• Author(s): Lindow, Steven; Purcell, Alexander; Baccari, Clelia;
• Abstract: Strain KLN61 is an rpfF mutant strain of Xylella fastidiosa (Xf) that cannot be transmitted to plants by the sharpshooter leafhopper, Graphocephala atropunctata (BGSS), an efficient vector of the wild-type strain of this bacterium. This mutant was not retained and did not form biofilm in the vector mouthparts, however was hypervirulent and formed biofilm when mechanically inoculated into grapevines (Newman et al. 2004). We created additional mutants of Xf rpfF mutant strain, KLN61 using a transposome-mediated mutagenesis technique (Streptomycin EZ::TN custom transposome mutagenesis system). Screening of mutants for restoration of vector transmissibility revealed that strains competed during systemic colonization of grapevines, with only a single strain eventually colonizing most of the plant. This prevented our further pursuit of using vector acquisition to screen for mutants that restored vector transmissibility. We are testing whether production of a signaling molecule in the plant by the wild-type Xf strain would restore the transmissibility of the mutant. Two transmission experiments in which BGSS were fed sequentially on the mutant KLN61 (not vector transmissible), then on the parent wild type strain Temecula, or the reverse order, showed that either exposure sequence reduced vector transmission by 35% to over 90% compared to a single exposure to the Temecula strain alone. These unexpected results imply that feeding exposure of vectors to a mutant Xf strain that does not produce cell signal can reduce later transmission of normally transmissible strains, as well as reducing transmission by vectors already infectious with a transmissible strain.
• Publication Date: Nov 2006
• Journal: 2006 Pierce's Disease Research Symposium