Characterization of the E3-Ubiquitine ligase ATL gene family in grapevine and stable transformation of Vitis vinifera with an ATL gene from Vitis riparia.

Our research group is mainly focused on the molecular basis of grapevine resistance to Plasmopara viticola, which is being investigated through different approaches. In previous microarray analyses, we identified several hundred genes, specifically activated in the resistant species Vitis riparia and not in the cultivated susceptible V. vinifera. Many of these genes are related to signal transduction or are homologous to known regulators of the defence response in other species. Among them, a group of genes encoding RING-Finger proteins (ATL subfamily) with E3-ubiquitine ligase activity are strongly upregulated only in the resistant species, very early after infection (12 hours post- inoculation). Based on published research, genes of this family could be interesting candidates for breeding or for biotechnological applications, to confer resistance against different stresses in crops. We have undertaken a project to characterize the ATL gene family in grapevine in terms of phylogenetic relationships, gene structure, chromosomal localization and expression in different biotic and abiotic stress conditions. In parallel, we started a stable grapevine transformation to express in V. vinifera an ATL gene from V. riparia, provisionally designed as VrATL - highly homologous to the ATL2 gene of Arabidopsis thaliana- under the 35S promoter. Transformed plants have been obtained from cv. Shiraz embryogenic calli and are now grown for further molecular and phenotypic characterization. Moreover, A. thaliana plants are being transformed with the GUS reporter gene under the control of the VrATL promoter, to investigate the responsiveness of this promoter to different biotic and environmental stresses.