Drought response mechanism of the Tartary buckwheat (Fagopyrum tataricum) variety ‘Dingku1’: multiple regulation of flavonoid biosynthesis by FtMYBs

• Innovative Discoveries: This study identifies Dingku1 as a strongly drought-resistant Tartary buckwheat cultivar and reveals the critical role of the FtMYB family in regulating flavonoid biosynthesis under drought stress. Notably, FtMYB78 is characterized as a key regulator with dual functions in phenylalanine metabolism branches, uncovering complex MYB-mediated regulatory networks in Tartary buckwheat’s stress responses. • Technical Methods: Integrative approaches were employed, including comparative phenotypic analysis of drought-responsive varieties, transcriptome profiling to link FtMYBs with flavonoid pathways, yeast one-hybrid, dual luciferase assays and hairy root transformation to validate regulatory interactions between FtMYBs and target flavonoid genes, and HPLC quantification of quercetin and rutin levels in MYB-overexpressing hairy roots, ensuring robust mechanistic validation. • Scientific Significance: These findings advance understanding of Tartary buckwheat’s drought tolerance mechanisms, particularly the multifaceted roles of MYB transcription factors in coordinating metabolic pathways. This work provides a theoretical foundation for molecular breeding of drought-resistant cultivars, enhancing agricultural sustainability for this economically important crop. Fagopyrum tataricum exhibits robust stress tolerance, while the molecular mechanisms governing its elite drought-resistant cultivars remain inadequately elucidated. In this study, different Tartary buckwheat varieties show varied drought responses; Dingku1 exhibits strong drought resistance. Further experiments and transcriptome analysis showed FtMYB family correlates with flavonoid biosynthesis under drought stress. Dual luciferase assays and yeast one-hybrid (Y1H) analyzed regulatory links between FtMYBs and key flavonoid genes. High-Performance Liquid Chromatography (HPLC) revealed quercetin and rutin changes after MYBs overexpression in hairy roots. Results indicated FtMYB78 has dual roles in phenylalanine metabolism branches, showing complex MYB regulation in Tartary buckwheat. Collectively, these findings illuminate Tartary buckwheat's drought response mechanisms, laying a theoretical basis for breeding drought-resistant varieties of this crucial crop.