The Boesenbergia rotunda R2R3-MYB Transcription Factor BrMYB2 Regulates Flavonoid Biosynthesis in Nicotiana tabacum

Flavonoids play essential roles in plant growth and development. However, their natural abundance is often low, limiting their large-scale commercial utilization. Understanding the molecular mechanisms underlying flavonoid biosynthesis is therefore critical to enhancing their production. Here, we isolated and functionally characterized BrMYB2, an R2R3-MYB transcriptional repressor from Boesenbergia rotunda. Sequence analysis revealed that BrMYB2 encodes a 219-amino acid protein with conserved subgroup 4 MYB domains, showing 92.8% similarity to a MYB-related protein from Zingiber officinale. To our knowledge, this is the first report of an R2R3-MYB repressor identified in B. rotunda. Heterologous expression of BrMYB2 in Nicotiana tabacum via Agrobacterium-mediated transformation led to the significant down-regulation of four key flavonoid biosynthetic genes (PAL, 4CL, CHI and DFR). Correspondingly, the accumulation of several targeted flavonoids, including p-coumaric acid, cinnamic acid, pinostrobin, and anthocyanin, was markedly reduced. These findings provide new insights into the transcriptional regulation of flavonoid metabolism in B. rotunda and establish a foundation for metabolic engineering strategies to enhance flavonoid production for pharmaceutical and agricultural applications.