The VvHY5-VvMYB24-VvMYBA1 transcription factor cascade regulates the biosynthesis of anthocyanin in grape

Anthocyanins are important pigments and nutrients in fruits. Red grape is popular because of the high anthocyanin content. Previous studies have identified VvMYBA1 and its homologs as key regulators of fruit color; however, other transcription factors (TFs) that contribute to fruit color remain poorly understood. The present study identified the R2R3-MYB TF VvMYB24, whose gene expression levels were significantly higher in red berries (L51, Vitis vinifera × Vitis labrusca L.) than in green berries (L20, V. vinifera × V. labrusca L.). Overexpression of VvMYB24 in grape calli increased anthocyanin biosynthesis by upregulating the expression of specific structural genes (VvDFR and VvUFGT). Furthermore, VvMYB24 interacted with VvMYBA1 to form a protein complex that additionally increased the expression of VvDFR and VvUFGT. In addition, light-responsive TF VvHY5 could bind to the VvMYB24 promoters to activate its transcription. Taken together, the results reveal a regulatory module, VvHY5-VvMYB24-VvMYBA1, that influences anthocyanin biosynthesis in grape.