BsMYB5-BsEGL1 transcriptional module activates low-temperature-induced anthocyanin biosynthesis in Begonia...

Low temperature is a key environmental stimulus that promotes anthocyanin biosynthesis in Begonia semperflorens. However, the molecular regulatory mechanism remains largely elusive. In this study, we first identified and functionally characterized dihydroflavonol 4-reductase (BsDFR) as a key enzyme in the anthocyanin pathway. Subsequently, we identified an R2R3-MYB transcription factor, BsMYB5, as a central regulator whose expression is rapidly upregulated under low-temperature treatment. Functional analyses revealed that BsMYB5 overexpression in B. semperflorens significantly enhances anthocyanin accumulation under both normal and low-temperature conditions. We further discovered that BsMYB5 specifically interacts with a low-temperature-induced bHLH transcription factor, BsEGL1. Crucially, we demonstrated that BsMYB5 and BsEGL1 form a functional complex that directly and synergistically binds to the promoter of BsDFR, as evidenced by yeast one-hybrid, dual-luciferase, and electrophoretic mobility shift assays, thereby activating its expression. Collectively, this study elucidates a core BsMYB5-BsEGL1 transcriptional module that mediates low-temperature-responsive anthocyanin biosynthesis in B. semperflorens, not only providing mechanistic insight into environmental adaptation but also promising genetic targets for breeding cultivars with enhanced cold tolerance and ornamental value.