Light induces VvbHLH93 transcription to promote anthocyanin biosynthesis in grapes

Anthocyanins, the key water-soluble pigments, can determine grape berry color and contribute to market value, stress tolerance, and human health benefits. Light is a major environmental factor regulating anthocyanin biosynthesis; however, the underlying molecular mechanisms remain not fully clarified. Previously, VvbHLH93 was found to negatively regulate proanthocyanidin biosynthesis, and preliminary evidence indicated a possible influence on anthocyanin-related genes in grape. However, its specific role in light-responsive anthocyanin production had not been explored. In this study, VvbHLH93 is demonstrated to function as a light-inducible transcription factor that may stimulate anthocyanin production. Analysis of the 1023-bp VvbHLH93 promoter showed an enrichment of light-responsive elements (LREs), which was further supported by promoter activity assays in Nicotiana benthamiana and Arabidopsis thaliana. Over-expression of VvbHLH93 in grape callus led to increased light-induced anthocyanin production, together with up-regulation of key biosynthetic genes and the master regulator VvMYBA1. These results suggest a potential regulatory pathway in which light signals, perceived through LREs in the VvbHLH93 promoter, induce VvbHLH93 expression, which may then contribute to the transcriptional activation of downstream targets to promote anthocyanin biosynthesis. The present work sheds some new lights on the light-mediated regulatory network controlling anthocyanin synthesis in grapes and suggests potential approaches for enhancing berry quality across diverse viticultural environments.

The online version contains supplementary material available at 10.1007/s12298-026-01772-w.