Figure 6.

MYB transcription factors regulates the action network of anthocyanin in plants’ internal and external environment. Under light conditions, anthocyanin biosynthesis is initiated in developing leaves or developing flowers/fruits by PHY photoreceptors (1) binding directly to MYB and bHLH. At the same time, CRY (2) and UVR8 (3) photoreceptors could inhibit (4) COP1 factor. In the dark, COP1 degraded MYB transcription factors that reduce the expression of genes activating anthocyanin biosynthesis (5), ultimately inhibiting anthocyanin accumulation. Under cold stress, C repeated binding factor (CBF factor) (6) activated anthocyanin biosynthesis through physical interaction with MYB and bHLH. At the same time, HY5 factor (7) also induces anthocyanin accumulation so that the anthocyanin structural gene could be up-regulated under low temperature under light conditions to activate the downstream network of anthocyanins. Under drought conditions, HAT1 factor (8) negatively regulates anthocyanin accumulation by binding to MBW protein complexes, while in the presence of the plant hormone ABA, ABA could inhibit the physical interaction between HAT1 and MYB75 and activate MYB75 to induce anthocyanin accumulation. When the MYB target sequence was methylated (9), anthocyanin accumulation was also inhibited. Under light conditions, MPK4 (10) interacts with MYB and bHLH and phosphorylates MYB, then participating in the accumulation of light-induced anthocyanins.