The Transcription Factor CaMADS1 Regulates Anthocyanin Biosynthesis in Pepper Leaves

The MADS-box transcription factor family is involved in regulating plant root germination, flowering, fruit development, maturation, and the biosynthesis of secondary metabolites. To investigate the role of MADS-box transcription factors in anthocyanin biosynthesis, this study utilized the pepper cultivar ‘CS03’ as experimental material. A transcription factor, CaMADS1, was selected from our previous transcriptome data for cloning and bioinformatic analysis. The results revealed that the CaMADS1 protein is localized to the nucleus. Quantitative real-time PCR analysis demonstrated that CaMADS1 is predominantly expressed in leaves. In CaMADS1-silenced plants, anthocyanin accumulation in the leaves decreased, which was consistent with the downregulated expression of structural genes in the biosynthesis pathway. In CaMADS1-overexpressing plants, both anthocyanin accumulation and the expression of these structural genes were elevated. Yeast one-hybrid and Dual-luciferase assays confirmed the interaction between CaMADS1 and the promoter of CaC4H, which encodes a key enzyme in anthocyanin biosynthesis. These results demonstrate that CaMADS1 positively regulates anthocyanin biosynthesis in pepper by directly binding to the promoter of the CaC4H gene.