Cloning and characterization of soybean gene Fg1 encoding flavonol 3-O-glucoside/galactoside (1→6) glucosyltransferase.

Key message Flavonoids are important secondary metabolites in plants. Sugar–sugar glycosyltransferases are involved in the final step of flavonoid biosynthesis and contribute to the structural diversity of flavonoids. This manuscript describes the first cloning of a sugar–sugar glucosyltransferase gene in the UGT family that attaches glucose to the 6″-position of sugar bound to a flavonol. The results provide a glimpse on the possible evolution of sugar–sugar glycosyltransferase genes and identify putative amino acids responsible for the recognition of the hydroxyl group of the sugar moiety and specification of sugar. A scheme for the genetic control of flavonol glycoside biosynthesis is proposed.