ANALYSIS OF THE EXPRESSION OF ANTHOCYANIN PATHWAY GENES IN DEVELOPINGVITIS-VINIFERA L-CV SHIRAZ GRAPE BERRIES AND THE IMPLICATIONS FOR PATHWAY REGULATION

Anthocyanin synthesis in Vitis vinifera L. cv Shiraz grape berries beg an 10 weeks postflowering and continued throughout berry ripening. Exp ression of seven genes of the anthocyanin biosynthetic pathway (phenyl alanine ammonia lyase [PAL], chalcone synthase [CHS], chalcone isomera se [CHI], flavanone-3-hydroxylase [F3H], dihydroflavonol 4-reductase [ DFR], leucoanthocyanidin dioxygenase [LDOX],and UDP glucose-flavonoid 3-o-glucosyl transferase [UFGT]) was determined. In flowers and grape berry skins, expression of all of the genes, except UFGT, was detected up to 4 weeks postflowering, followed by a reduction in this expressi on 6 to 8 weeks postflowering. Expression of CHS, CHI, F3H, DFR, LDOX, and UFGT then increased 10 weeks postflowering, coinciding with the o nset of anthocyanin synthesis. In grape berry flesh, no PAL or UFGT ex pression was detected at any stage of development, but CHS, CHI, F3H, DFR, and LDOX were expressed up to 4 weeks postflowering. These result s indicate that the onset of anthocyanin synthesis in ripening grape b erry skins coincides with a coordinated increase in expression of a nu mber of genes in the anthocyanin biosynthetic pathway, suggesting the involvement of regulatory genes. UFGT is regulated independently of th e other genes, suggesting that in grapes the major control point in th is pathway is later than that observed in maize, petunia, and snapdrag on.