Expression and tissue and subcellular localization of anthocyanidin synthase (ANS) in grapevine.

Anthocyanidin synthase (ANS) is one of the key enzymes in the biosynthesis of both anthocyanins and proanthocyanidins in grapevine. Although substantial researches have investigated ANS gene expression and regulation at the transcriptional level, little is yet known about protein expression and distribution in grapevine. Here, the expression and tissue and subcellular localization of ANS in different Cabernet sauvignon grapevine tissues were investigated by using the techniques of Western blotting, immunohistochemical localization, immuno-electron microscopy, and confocal microscopy. The results showed that the ANS was expressed in the grape berries, leaves, stems, petioles, and leaf buds. In grape berry skin and flesh, ANS expression is developmental dependent. Immunohistochemical analysis revealed that ANS is primarily distributed in the exocarp, mesocarp, and seed of the fruit; in palisade and spongy tissues of the leaves; in the primary phloem and pith ray in the stems; and in the growth point and leaf primordium of the leaf buds. Furthermore, at the subcellular level, the ANS was mainly localized in the cytoplasm regardless of cell types and some ANS were also found in the nucleus in the mesocarp vascular bundle and leaf bud cells. This research will give further insight for the biosynthesis and regulation of different flavonoid compounds in grapevine.