Résumé
Expression QTL (eQTL) mapping consists in applying QTL analysis method on transcript abundance in a segregating population. eQTL studies allow the identification of candidate regions and therefore candidate genes involved in regulation of transcript abundance. We describe here the first eQTL study in grapevine. We used a pseudo-F1 population of 191 progenies (SxG) derived from a reciprocal cross of Syrah and Grenache. Expression of target genes was recorded by RT-qPCR. Our interest pathway is the proanthocyanidin (PA) branch of the flavonoid biosynthesis. Indeed, PA are the most abundant secondary metabolites in grape berry and are responsible of astringency, a major quality trait of wine. We first validated the feasibility of eQTL approach by mapping expression of VvUFGT, a well known gene of anthocyanin synthesis, another branch of the flavonoid pathway. A cis- and a trans-eQTL were detected for VvUFGT, and the trans-eQTL colocalized with the major transcription factor cluster of anthocyanin synthesis. For PA branch, we measured the expression of specific PA synthetic genes (VvANR, VvLAR1, VvLAR2) and two genes of the flavonoid synthesis, VvDFR and VvLDOX, common to both PA and anthocyanin synthesis. One trans- and two cis-eQTL were detected for three of the five investigated genes. Our results show the interest to use eQTL approach to understand genomic regulation of grapevine quality traits and provide perspectives to extend grapevine eQTL analysis to a genome-wide extent.