Genetic analysis of grapevine wood composition identifies glycosyltransferases involved in the biosynthesis of stilbene glycosides

Although wood extractives may play important roles in defense against pathogens, few studies have explored the genetic determinism of their accumulation. In this work, we have used a non-targeted metabolomic approach to perform a genetic analysis of grapevine (Vitis vinifera) wood extractive composition in a progeny from a cross between Riesling and Gewurztraminer. Metabolic quantitative trait loci (mQTL) analyses of cane and trunk wood extractives revealed a number of mQTLs. Analysis of one of these mQTL has led to the identification of a cluster of six UDP glycosyltransferase (UGT) genes linked to the accumulation of resveratrol-glucoside (piceid) in both canes and trunks. Detailed biochemical and structural characterization of these six UGTs highlighted a surprising functional diversity among this small gene family, as well as one UGT gene as a key determinant of the constitutive accumulation of piceid in lignified grapevine tissues. Molecular evolution analyses showed that the UGTs in this gene cluster were globally under strong purifying selection, suggesting important biological roles of the corresponding proteins. Moreover, the functional characterization showed that distinct UGT genes were involved in the biosynthesis of cis- and trans- isomers of piceid, suggesting that these isomers may play different biological roles in grapevine.