RESISTANCE TO PIERCES DISEASE BY TRANSGENIC EXPRESSION OF PLANT-DERIVED ANTI-APOPTOTIC GENES

• Author(s): Gilchrist, David; Lincoln, James;
• Abstract: Several relatives of grape and other asymptomatic host plants can harbor high titers of Xylella fastidiosa (Xf) without exhibiting symptoms of Pierces disease (PD). The basis of what is a genetic difference is unknown. We have established that leaf scorch PD symptoms in grape result from apoptosis or programmed cell death (PCD). Clearly, Xf does not have to kill in order colonize the vascular system leaving this endophytic association asymptomatic. We have identified from a cDNA library screen several grape genes that block PCD when over-expressed in grape tissue. Preliminary experiments indicate that one of these genes, VVPR1A, is expressed or up-regulated in situations in which PCD is blocked in humans, nematodes, hookworms and several plant species. This gene also is upregulated in the presence of Xf. We are testing the hypothesis that over expression of one or more of the 12 genes recovered in the anti-apoptotic screen, with an initial focus on VVPR1A, can block both PCD induced by Xf and disease symptoms associated with Xf. Preliminary results reported here indicate that grape plants over expressing VVPR1A, metallothionein, or a Meloidogyne incognita upregulated gene can block symptoms in a cut branch assay. Experiments with whole transgenic plants inoculated with Xf are in progress to assess the movement of bacteria, the induction of Xf responsive grape genes and if symptoms of PD are affected by the anti-apoptotic transgenes.
• Publication Date: Nov 2006
• Journal: 2006 Pierce's Disease Research Symposium