Regulation of Anthocyanin Biosynthesis in Tissues of a Teinturier Grape Cultivar under Sunlight Exclusion

Yan-73 (Vitis vinifera) is a teinturier grape cultivar, which accumulates anthocyanins in skin, pulp, pedicels, and rachis. The effects of sunlight on anthocyanin biosynthesis and regulation in various tissues of this teinturier cultivar were investigated. Light transmission measurements showed that covering with opaque boxes substantially reduced light intensity around clusters; <= 0.25% of incident light reached the berry skin and <0.05% reached the pulp. The pulp naturally experiences increasing sunlight exclusion by skin during ripening. Sunlight exclusion reduced and delayed anthocyanin biosynthesis in skin and pulp during berry development, while both tissues nevertheless accumulated enough anthocyanins to turn dark red. No strong reduction of anthocyanin concentration was observed in pedicels or rachis. Sunlight exclusion decreased transcript abundance of VvUFGT, VvMybA1, VvMybA2, and VvMyc1 in both skin and pulp and also decreased transcript abundance of VvMycA1 in pulp. Sunlight exclusion differently influenced the anthocyanin components: it decreased the relative proportion of 3 ',4 ',5 '-hydroxylated anthocyanins and increased that of 3 ',4 '-hydroxylated anthocyanins in berry skin and pulp, which corresponded to the change in the ratio of VvF3 ' H to VvF3 ' 5 ' H. These results allow for insight on anthocyanin biosynthesis in various grape tissues in absence of sunlight.