VviAHA10, a tonoplast P3A-type ATPase from Vitis vinifera, reveals a functional link between vacuolar flavonoid accumulation and abiotic stress responses

In grapevine (Vitis vinifera), vacuolar accumulation of flavonoids such as anthocyanins and tannins is crucial for the organoleptic properties of wine, including color, aroma, and astringency. This process depends on proton pumps that generate an electrochemical gradient, enabling the active transport of flavonoids into the vacuole. In this study, we functionally characterize VviAHA10, a putative P3A-type H⁺-ATPase highly expressed in grape berry skins during veraison and post-veraison stages. Phylogenetic, structural, and motif analyses support its classification as a conserved vacuolar proton pump. Heterologous expression assays in tobacco showed that VviAHA10 is sufficient to promote vacuolar flavonoid accumulation, while in Arabidopsis thaliana, VviAHA10 rescued the anthocyanin and proanthocyanidin accumulation defects of the tt13-6 mutant. VviAHA10 expression also restored vacuolar pH homeostasis and root growth under complete phosphate starvation, salt stress, and combined stress conditions, enabling stress-induced anthocyanin accumulation comparable to wild-type levels. Confocal imaging of vacuolar pH in roots further revealed that VviAHA10 enhances vacuolar acidification capacity during stress. Altogether, our findings show VviAHA10 has the capacity to regulate flavonoid accumulation and stress-associated cellular processes when expressed in heterologous plant systems. These results highlight VviAHA10 as a promising molecular target for improving grape berry quality and resilience under changing environmental conditions.