Search

Rutin-degrading enzymes play a crucial role in catalyzing the hydrolysis of rutin (quercetin 3-O-rutinoside) into the bitter compound quercetin, contributing significantly to the bitterness of Tartary buckwheat (Fagopyrum tataricum) (TB). Mitigating this bitterness is vital for improving the palatability and marketability of TB products. In this study, we integrated genomic and transcriptomic data with molecular docking analyses to identify 12 potential rutin-degrading enzymes in TB. Among them, FtBGLU29 exhibited a stable binding affinity for rutin and significantly higher expression levels, specifically in TB seeds. This unique expression was confirmed through Native-PAGE and MALDI-TOF/TOF-MS, which identified FtBGLU29 as the predominant rutin-degrading enzyme in TB seeds. In vitrohydrolysis experiments revealed that FtBGLU29 efficiently catalyzes the conversion of rutin to quercetin upon the hydration of TB flour. Functional studies showed that FtBGLU29overexpression in TB seeds significantly enhanced the rutin hydrolysis rate relative to the control group (p< 0.05). In conclusion, this study establishes FtBGLU29 as a key enzyme in the degradation of rutin in TB seeds, highlighting its critical role in enhancing the enzymatic conversion efficiency and potentially reducing the bitterness of TB products.

Tartary buckwheat is highly valued for its abundant rutin (quercetin 3-O-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, FtUFGT163, potentially encoding flavonol 3-O-glucoside (1 → 6) rhamnosyltransferase in Tartary buckwheat through omics analysis and molecular docking methods. The recombinant FtUFGT163 expressed in Escherichia colidemonstrated the capacity to glycosylate isoquercetin into rutin. Overexpression of FtUFGT163significantly enhanced the rutin content in Tartary buckwheat. Further investigation identified a novel bZIP transcription factor, FtGBF1, that enhances FtUFGT163expression 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 FtGBF1promoter. Collectively, this study elucidates a novel regulatory module, termed “FtMYB5/6–FtGBF1–FtUFGT163”, which effectively coordinates the biosynthesis of rutin in Tartary buckwheat, offering insights into the genetic enhancement of nutraceutical components in crops.