Genome-Wide Identification of the MYB Family in Morus atropurpurea and Functional Characterization of MaDIV for Its Possible Involvement in Anthocyanin Biosynthesis

Background: Anthocyanin biosynthesis is tightly controlled by MYB transcription factors, yet the role of repressors, particularly those in the DIVARICATA-like (DIV) subfamily, remains poorly characterized. Methods: A genome-wide identification of MYB family members was performed in the mulberry (Morus atropurpurea) genome using a hidden Markov model and BLAST-based searches. Putative MYB genes were phylogenetically classified, and their expression profiles were analyzed across three fruit developmental stages. A DIV-like R2R3-MYB candidate, MaDIV, was functionally characterized via subcellular localization, quantitative real-time PCR, and heterologous overexpression in tobacco. Results: A total of 145 MaMYB genes were identified and classified into 31 distinct subfamilies. MaDIV expression showed a progressive decline during fruit ripening, which significantly correlated with increasing anthocyanin accumulation. Heterologous overexpression of MaDIV in tobacco led to a 42% reduction in floral anthocyanin content compared with wild-type plants. Concomitantly, the expression of the key anthocyanin biosynthetic gene NtDFR was strongly suppressed, whereas the flavonol synthase gene NtFLS1 was significantly upregulated. Conclusions: These findings point to a possible involvement of MaDIV in the regulation of anthocyanin biosynthesis and provide preliminary evidence for the functional diversification of the DIV-like MYB subfamily in plants. The results contribute to a better understanding of the transcriptional control of fruit pigmentation in mulberry and related species.