Gene Expression and Molecular Architecture Reveals UDP-Glucose: Flavonoid-3- O-Glucosyltransferase UFGT as a Controller of Anthocyanin Production in Grapes

Anthocyanin pigments from the flavonoid biosynthesis pathway in grapes (Vitis sp.) are gaining increasing popularity in the wine industry as a mark for quality, preventive medicine in the natural products sector, food colorants and raw materials for cosmetics. Grape skins, the primary source of these pigments cannot meet increasing market demand, therefore, this study was undertaken to explore in-vitro cell culture of grape as a mean to redirect and control the expression of genes in the anthocyanin biosynthetic pathway. This study examined levels of expression of UDP-Glucose: Flavonoid-3-O-Glucosyltransferase (UFGT), which is a gene responsible for the last stages of anthocyanin production between unripe grape berries, ripening (veraison) berries and fully ripe (physiologically mature) berries. In-vitro red cell cultures were carried out to establish the optimal stage of harvesting cells for culturing to maximize production of anthocyanin and to determine feasibility of using cell culture over fresh grape tissues. Clones of the UFGT gene from muscadine grapes were isolated, sequenced, and compared to other known species to examine variations of functional significance. Changes in functional regions which could affect accumulation of anthocyanins including substrate binding sites, methyl donor binding sites and catalytic sites were examined. Results from this study indicated that, cell cultures produced significantly higher amount of anthocyanin over fresh tissues, and veraison was the optimum stage for harvesting cells for culturing. This work demonstrated that, the UFGT gene can be a viable candidate for shifting the metabolic flux of anthocyanins in grapes.