Determining factors, regulation system, and domestication of anthocyanin biosynthesis in rice leaves

Wild and cultivated rice show a significant difference in anthocyanin biosynthesis in the leaf. The regulation system of anthocyanin biosynthesis in rice leaf and the causal mechanism of the difference in this biosynthesis between wild and cultivated rice remain largely unknown. In this study, a genome-wide association study and transcriptome analysis were performed to identify the determinant factors and dissect the regulatory system for anthocyanin biosynthesis in rice leaves. OsC1, OsRb and OsDFR were identified as the determinants of anthocyanin biosynthesis in rice leaves. Artificial selection of certain null mutations of OsC1 and OsRb was the main causal mechanism underlying the loss of anthocyanin pigmentation in most cultivated rice. OsP1 and the MYB-bHLH-WD40 complexes regulate anthocyanin biosynthetic genes in rice leaves with partial functional overlap. OsP1 specifically activates upstream biosynthetic genes (OsCHS, OsCHI and OsF3'H) for anthocyanin biosynthesis, whereas the ternary MYB-bHLH-WD40 complex activates all anthocyanin biosynthetic genes including OsCHS, OsCHI, OsF3'H, OsF3H, OsDFR and OsANS. OsC1 and OsRb are tissue-specific regulators that do not influence anthocyanin biosynthesis in the pericarp. Our results reveal the determinant factors, regulatory system and domestication of anthocyanin biosynthesis in rice leaves, and show the potential of engineering anthocyanin biosynthesis in rice.