The R2R3-MYB transcriptional repressor CaMYB330 negatively regulates anthocyanin biosynthesis in pepper

Anthocyanins are important secondary metabolites of the flavonoid pathway that contribute to plant coloration, stress responses, and human health benefits. In pepper ( Capsicum annuum L.), activator MYB transcription factors involved in anthocyanin biosynthesis have been extensively reported, whereas the roles of repressor MYBs remain poorly understood. In this study, we identified an R2R3-MYB transcriptional repressor, CaMYB330 . Expression analysis showed a significant negative correlation between the transcript level of CaMYB330 and anthocyanin accumulation. Overexpression of CaMYB330 suppressed the expression of key anthocyanin structural genes such as CaDFR, CaANS , and CaUFGT , while silencing CaMYB330 promoted anthocyanin accumulation in pepper leaves. Mechanistically, CaMYB330 regulates anthocyanin biosynthesis through two modes: (i) directly binding to and repressing the promoters of structural genes, thereby reducing their expression, and (ii) competing with the activator CaMYBA for interaction with CaMYC, which weakens the activity of the CaMYBA–CaMYC complex. Furthermore, the light-responsive transcription factor CaHY5 bound the CaMYB330 promoter and suppressed its expression, thereby alleviating the repressive effect of CaMYB330 under light conditions and promoting anthocyanin biosynthesis. Collectively, these findings indicate that CaMYB330 functions as a negative regulator of anthocyanin biosynthesis in pepper leaves. Moreover, they support the existence of a CaHY5–CaMYB330 regulatory module, providing new insights for pepper color improvement and molecular breeding strategies.