Figure 1.

Scheme of flavonoid biosynthetic pathways in grapevine. Anthocyanins are synthesized by a multienzyme complex loosely associated to the endoplasmic reticulum (CHS, chalcone synthase; CHI, chalcone isomerase; F3H, flavanone 3-hydroxylase; F3′H, flavonoid 3′-hydroxylase; F3′5′H, flavonoid 3′5′-hydroxylase; DFR, dihydroflavonol reductase; LDOX, leucoanthocyanidin oxidase; UFGT, UDP-glucose:flavonoid 3-O-glucosyl transferase; MT, methyltransferase). Flavonol and proanthocyanidin syntheses branch off from the anthocyanin pathway (FLS, flavonol synthase; LAR, leucoanthocyanidin reductase; ANR, anthocyanidin reductase).