Blue light-induced MiBBX24 and MiBBX27 simultaneously promote peel anthocyanin and flesh carotenoid biosynthesis in mango

Blue light simultaneously enhances anthocyanin and carotenoid biosynthesis in mango (Mangifera indica L.) fruit peel and flesh, respectively, but the mechanism remains unclear. In this study, two blue light-triggered zinc-finger transcription factors, MiBBX24 and MiBBX27, that positively regulate anthocyanin and carotenoid biosynthesis in mango fruit were identified. Both MiBBXs transcriptionally activate the expression of MiMYB1, a positive regulator of anthocyanin biosynthesis. Furthermore, both MiBBXs also trigger the expression of a phytoene synthase gene (MiPSY), which is essential for carotenoid biosynthesis. Ectopic expression of MiBBX24 or MiBBX27 in Arabidopsis increased anthocyanin contents, and their positive effects on anthocyanin accumulation in mango peel were confirmed through transient overexpression and virus-induced silencing. Transient expression of MiBBX24 or MiBBX27 in tomato (Solanum lycopersicum) and mango fruit flesh increased the carotenoid content, while the virus-induced silencing of MiBBX24 or MiBBX27 in the mango fruit flesh decreased carotenoid accumulation. Overall, our study results reveal that MiBBX24 and MiBBX27 simultaneously promote the biosynthesis of anthocyanin and carotenoids biosynthesis in mango fruit peel and flesh under blue light, indicating that BBX-mediated dual effects on physiological functions contribute to mango fruit pigment accumulation. Furthermore, we herein shed new light on the simultaneous transcriptional regulatory effects of a single factor on the biosynthesis of different plant pigments.