Investigating the Vitis vinifera – Plasmopara viticola interaction: stable overexpression of a Vitis riparia ATL gene in Vitis vinifera and characterization of the grapevine ATL gene family.

Grapevine (Vitis vinifera) is one of the most important fruit crops in the world, with a high economic impact, mainly due to wine production. Despite many years of breeding selection on the basis of the organoleptic qualities, very little has been achieved regarding the resistance towards pathogens. Our research group studies the interaction between grapevine and Plasmopara viticola, the causative agent of downy mildew. From a previous microarray experiment we found a set of genes specifically upregulated in Vitis riparia, a naturally resistant species, compared to V. vinifera during the early stages of infection with P. viticola. Interestingly, eight of those genes were annotated as ATLs, a group of RING E3-Ubiquitin ligases, known to be involved in the resistance processes. With the aim to reduce the susceptibility of the cultivated grapevine towards pathogens, we started a project of stable transformation of V. vinifera with a promising ATL gene from V. riparia. Up to date few plants overexpressing the candidate gene have been regenerated from embryogenic calli of V. vinifera. cv Shiraz and are now in the process of molecular and phenotypical characterization. In parallel, we carried out the bioinformatic analysis of the ATL gene family in grapevine defining the phylogenetic relationships, gene structures and chromosomal localizations. Furthermore we began studying the different responsiveness of the regulative regions of the ATL candidate gene from both Vitis species, by stably transforming Arabidopsis thaliana with the GUS reporter gene under the control of the selected ATL promoters.