1a.Objectives (from AD-416):
1. Identification of PD resistance genes in Vitis species.
2. Molecular determination PD resistance mechanisms.
1b.Approach (from AD-416):
1. Identify candidate R genes from microarray global gene expression analyses.
2. Cloning and molecular characterization of target genes using in vitro expression system.
3. Develop R gene molecular markers for marker-assisted selection.
This research project is to identify PD resistance mechanisms of grapevines in support of Objective 2 of the parent project to determine the nature and mechanism(s) of susceptibility/resistance to Xylella fastidiosa (Xf) infection in Vitis and Prunus species. Transcriptional profiling of PD-resistant and PD-susceptible grapevines in response to Xf infection were generated from stem tissue of Xf-infected and healthy grapevines at 1, 6, and 12 weeks post-inoculation. Eight candidate resistance genes that were up-regulated in response to Xf infection were identified in PD-resistant grapevines. Quantitative PCR was carried out to confirm the gene expression. Two defense response genes that encode jasmonic acid methyltransferase and methyljasmonate esterase were cloned, in vitro translated and the products biochemically characterized.