Characterization of Three Glucosyltransferase Genes in Tartary Buckwheat and Their Expression after Cold Stress

Anthocyanins confer the red color in the hypocotyl of tartary buckwheat sprouts. Uridine diphosphate (UDP)-glucose:flavonoid 3-O-glycosyltransferase (UFGT) stabilizes anthocyanin by attaching the glucosyl moiety from UDP-glucose to the C3 hydroxyl of anthocyanin. In this study, we characterized three UFGT-like genes, designated FtUFGT1, 2, and 3 from tartary buckwheat. The results revealed that FtUFGT1, FtUFGT2, and FtUFGT3 can convert cyanidin to cyanidin 3-O-glucoside, with specific activities of 20.01 × 10(-3), 8.93 × 10(-3), and 20.24 × 10(-3) IU/mg, respectively. The active-site residues of the C-terminal domains and the N-terminal domains are important for the donor and acceptor recognition of these proteins. The expression of the three FtUFGTs paralleled the tissue-specific anthocyanin accumulation. After cold treatment, the increased content of anthocyanin was accompanied by the up-regulated expression of the three FtUFGTs. Among these three UGFT gene members, FtUFGT3 showed the highest expression level and the highest specific activity, suggesting that FtUFGT3 might be the major gene involved in anthocyanin biosynthesis. These results suggested that the FtUFGT genes, FtUFGT3 in particular, might be important candidates for anthocyanin formation in tartary buckwheat sprouts.