COORDINATE INDUCTION OF ANTHOCYANIN BIOSYNTHETIC PATHWAY GENES BY VVMYBAS

Recent studies in grapevine revealed that VvMYBA transcription factors control the expression from UDP-glucose flavonoid: 3-O-glucosyltransferase (UFGT) to the candidate genes putatively involved in the vacuolar anthocyanin transport. Additionally, data on northern blot analysis had revealed that, in addition to UFGT, other anthocyanin biosynthesis pathway genes were also expressed coordinately at higher levels in red skin grapes than in white skin grapes. Hence, molecular targets of VvMYBAs may be a set of anthocyanin biosynthetic pathway genes. Therefore, we compared GeneChip data of the berry skin of ‘Pinot Noir’ and its white sport ‘Pinot Blanc’ to reveal the targets of VvMYBAs. Seventy highly hybridized probe sets (≥5 folds) of ‘Pinot Noir’ were mostly related to anthocyanin biosynthesis, whereas those of ‘Pinot Blanc’ (56 probe sets) were related to disease resistance and unidentified ones. In addition to flavonoid-3’, 5’-hydroxylase and cytochrome b5 DIF-F, the genes specific to and putatively involved in anthocyanin biosynthesis, such as UFGT, gluta-thione S-transferase, O-methyltransferase, and acyltransferase (serine carboxypeptidase like protein), were highly expressed in ‘Pinot Noir’, while their expressions were negligible in ‘Pinot Blanc’. This result confirmed that the expressions of these genes are induced by VvMYBAs. On the other hand, those involved in the common pathway of flavonoid biosynthesis, such as phenylalanine ammonia-lyase, chalcone synthase 3, flavanone-3-hydroxylase, dihydroflavonol 4-reductase, and leucoanthocyanidin dioxygenase, were also expressed in ‘Pinot Blanc’ to a certain extent, and their expressions were enhanced in ‘Pinot Noir’. This result indicates a possibility that VvMYBAs, in addition to other transcription factor(s), also induce the expression of these genes.