Regulatory Module FtMYB5/6-FtGBF1- Promotes Rutin Biosynthesis in Tartary Buckwheat.

Tartary buckwheat is highly valued for its abundant rutin (quercetin 3--rutinoside). As a flavonoid glycoside, rutin is synthesized with the crucial involvement of UDP-dependent glycosyltransferases (UGTs). However, the functions and transcriptional regulation of the UGT-encoded genes remain poorly understood. This study identified a key gene, , potentially encoding flavonol 3--glucoside (1 → 6) rhamnosyltransferase in Tartary buckwheat through omics analysis and molecular docking methods. The recombinant FtUFGT163 expressed in demonstrated the capacity to glycosylate isoquercetin into rutin. Overexpression of significantly enhanced the rutin content in Tartary buckwheat. Further investigation identified a novel bZIP transcription factor, FtGBF1, that enhances expression by binding to the G-box element within its promoter, thereby augmenting rutin biosynthesis. Additional molecular biology experiments indicated that the specific positive regulator of rutin, FtMYB5/6, could directly activate the promoter. Collectively, this study elucidates a novel regulatory module, termed "FtMYB5/6-FtGBF1-", which effectively coordinates the biosynthesis of rutin in Tartary buckwheat, offering insights into the genetic enhancement of nutraceutical components in crops.