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

• Author(s): Lindow, Steven; Purcell, Alexander; Baccari, Clelia;
• Abstract: The sharpshooter vector transmission of Xylella fastidiosa (Xf) to grape causes Pierces disease (PD). Identification of genes in Xf which are responsible for transmission is an essential step in understanding bacteria-vector interactions and may shed light on biofilm formation by Xf. The aim of this work is to understand the role of the genetic regulon of the rpf (regulation of pathogenicity factors) system in Xf and its role in disease transmission. In Xf, the rpf system likely regulates genes important for colonization of and transmission by insect vectors. The rpfF gene is one of the essential genes of the rpf cell-cell signaling system. Transcriptional control regulates genes by cell-cell signaling. The rpfF gene codes for the enzyme that synthesises the signaling molecule, DSF (diffusible signal factor). This system regulates the expression of a host of genes that are as yet unidentified in Xf. The rpf gene cluster of Xanthomonas campestris pathovar campestris is required for pathogenesis of this bacterium to plants (Dow et al. 2000). In a transmission experiment with the sharpshooter leafhopper Graphocephala atropunctata (BGSS), the Xf strain KLN61 (an rpfF knockout mutant) could not perform cell-cell signaling. It was not retained by the insect vector and consequently not transmitted to the plants (Newman, 2004). When the Xf rpfF mutant strain was compared with Xf wild type, it showed to be hypervirulent, non-transmissible, and lacked biofilm formation. Because the spread of Pierces disease requires the transmission by insects, this indicates that blocking bacterial transmission by insect vectors may be a strategy for controlling PD. However, this requires a better understanding the role of cell-cell signaling by Xf and its importance for transmission.
• Publication Date: Dec 2004
• Journal: 2004 Pierce's Disease Research Symposium