Global Gene Expression Responses to Water-Deficit in Roots and Berries of Grapevine

According to climate forecasts, an increase in average temperatures and a decrease in rainfall during spring and summer are expected by the end of the 21st century in Europe, exposing vineyards to an increased risk of severe periods of drought. To investigate the effects of water deficit at the rootstock and berry levels, two projects have been developed. A first approach was undertaken for a comprehensive analysis of rootstocks response and adaptation to water-limiting conditions. Drought experiments have been conducted with four rootstock/scion combinations exhibiting contrasted sensitivity to water deficit. Root samples were subjected to global transcriptome analyses using whole-genome arrays and RNAseq. Although drought affects the expression of about 5000 genes in roots, only a small set of these genes exhibit genotype-specific response to water-deficit, some of them being potentially involved in the adaptive mechanisms of the rootstock.

Another approach investigated the effects of water stress on berry composition and transcriptome. Vitis vinifera cv. Pinot noir grafted on either rootstock 110R (drought tolerant) or 125AA (drought sensitive) were studied during three growing seasons in the field under normal rainfall or water shortage conditions. Berry composition analysis indicates that water stress did not significantly affect berry weight and sugar content, but increased anthocyanin content regardless of rootstock. Under drought stress, transcriptome analysis reveals differences between the two rootstocks for genes related to jasmonate and phenylpropanoid metabolisms. Moreover, and according to our data, a link between these two functional categories in water-stressed berries can be suggested.