Effects of abscisic acid agonist or antagonist applications on aroma volatiles and anthocyanin biosynthesis in grape berries

The effects of applying abscisic acid (ABA), Abz (abscinazole, an inhibitor of CYP707A), and nordihydroguaiaretic acid ((NDGA), an inhibitor of 9-cis-epoxycarotenoid dioxygenase (NCED)) on fruit firmness, anthocyanin biosynthesis, aroma volatiles, and their related genes were investigated in grape berries (Vitis vinifera L. × Vitis labrusca L. cv. Kyoho). ABA and Abz application promoted the accumulation of anthocyanin and aroma volatiles, the activity of polygalacturonase (PG), pectin methylesterase, and cellulase, but reduced fruit firmness. On the other hand, NDGA showed the opposite tendencies. Abz decreased VvCYP707A1 expression but increased VvPYL8 expression. VvPP2C49 expression was negatively correlated with ABA concentration. The expression levels of VvMYBA2 and VvUFGT correlated with anthocyanin concentration, unlike those of VvLAR1. ABA and Abz application increased endogenous ABA concentrations and the expression levels of VvOPR3, VvACO1, and VvPG, whereas NDGA application decreased them. These results suggest that ABA concentrations influence anthocyanin formation and fruit softening through the expression of VvMYBA2, VvUFGT, and VvPG.