Blue light enhances anthocyanin accumulation in grape berries, yet the molecular mechanisms underlying this photoreceptor-mediated process remain partially elucidated. ‘Kyoho’ grapevines were subjected to various light treatments, including monochromatic blue and red light (blue, red, or white) and mixed red-blue light treatments before fruit coloration. Anthocyanin content, transcriptome profiles, and gene expression were analyzed. Blue light most effectively promoted anthocyanin biosynthesis and upregulated structural genes ( VvCHS, VvUFGT, VvANS ) and the photoreceptor gene ( VvCRY2 ) expression, whose expression was strongly correlated with anthocyanin accumulation. VvCRY2 physically interacts with the E3 ubiquitin ligase VvCOP1, repressing its activity under blue light. VvCOP1 interacts with transcription factors VvHY5 and VvMYBA1 in darkness, suppressing anthocyanin synthesis. Overexpression of VvCRY2 or VvHY5 enhanced anthocyanin accumulation in transgenic grape calli and strawberry fruits under blue light. VvHY5 directly binds to G-box elements in promoters of VvMYBA1, VvCHS, VvUFGT and VvANS , activating their expression via dual-luciferase assay. We propose a mechanistic model wherein blue light-activated VvCRY2 inhibits VvCOP1, releasing VvHY5 to transcriptionally activate anthocyanin biosynthesis genes. This study elucidates the VvCRY2-VvCOP1-VvHY5 module as a central regulatory axis for light-quality-mediated fruit coloration in grape.
Dong et al. (Sun,) studied this question.