The bZip transcription factor HY5 mediates CRY1a-induced anthocyanin biosynthesis in tomato

The production of anthocyanin is regulated by light and corresponding photoreceptors. In this study, we found that exposure to blue light and overexpression of CRY1a are associated with increased accumulation of anthocyanin in tomato (Solanum lycopersicum L.). These responses are the result of changes in mRNA and the protein levels of SlHY5, which is a transcription factor. In vitro and in vivo experiments using electrophoretic mobility shift assay and ChIP-qPCR assays revealed that SlHY5 could directly recognize and bind to the G-box and ACGT-containing element in the promoters of anthocyanin biosynthesis genes, such as chalcone synthase 1, chalcone synthase 2, and dihydroflavonol 4-reductase. Silencing of SlHY5 in OE-CRY1a lines decreased the accumulation of anthocyanin. The findings presented here not only deepened our understanding of how light controls anthocyanin biosynthesis and associated photoprotection in tomato leaves, but also allowed us to explore potential targets for improving pigment production.