Altitudinal regulation of flavonoid biosynthesis in Vitis vinifera: unraveling the VvbHLH88-VvUFGT module driving anthocyanin

In this study, Flavonoids in grape berry skins were monitored at four key developmental stages (green berry, veraison, pre-harvest, and harvest) and at different altitude gradients (two typical altitudes) using transcriptome analysis. Of the genes related to flavonoids, VvbHLH88 was identified as a candidate transcription factor related to the biosynthesis of anthocyanins (a class of flavonoids) by comparing skins from grapes grown at high and low altitudes. Determination of the anthocyanin content in wounded tissues of VvbHLH88-overexpressing and -silenced grape revealed that VvbHLH88 was a positive regulator of anthocyanin biosynthesis. Transcriptome analysis of VvbHLH88-overexpressing healing tissues showed that the expression of anthocyanin synthesis branching enzyme genes was up-regulated. In addition, VvbHLH88 directly bound to the promoter of the UDP-glucoflavone-3-O-glucosyltransferase (VvUFGT) gene and activated its transcriptional regulation of anthocyanin synthesis. Consequently, our results elucidate the molecular pathways and specific transcriptional regulatory networks by which high-altitude ecological factors affect grape flavonoid metabolism, deepening the theoretical understanding of the relationship between environmental factors, metabolic regulation, and fruit quality formation.