Enhancement of anthocyanin biosynthesis by sugar in radish (Raphanus sativus) hypocotyl

Radish (Raphanus sativus) hypocotyl accumulates anthocyanins as the plant grows. Although anthocyanins were detected in both the peripheral cortex and pericycle, the major site of accumulation was the pericycle. Detached hypocotyls of radish seedlings produced large amounts of anthocyanins using exogenous glucose, fructose, or sucrose, but little anthocyanin using mannose or 3-O-methyl-D-glucose. Treatment with 175 mM sucrose was most effective in inducing anthocyanin biosynthesis in the hypocotyl system. Two anthocyanin biosynthetic genes, chalcone synthase and anthocyanidin synthase, were significantly activated by sucrose, whereas these genes were expressed weakly in the control. These results suggested that sugars transported into hypocotyls promote anthocyanin biosynthesis by inducing expression of the biosynthetic genes in radish. (C) 2002 Elsevier Science Ireland Ltd. All rights reserved.