Two Neighboring CYP450s Orchestrate Quercetin-Mediated Defense and Growth in Tartary Buckwheat

Quercetin, a key flavonoid in Tartary buckwheat (Fagopyrum tataricum), plays a dual role in enhancing plant defense and human nutritional health. Through a genome-wide association study (GWAS) of quercetin content, we identified a significant locus containing four tandemly duplicated CYP450 genes. Functional studies revealed that two adjacent homologous genes, ‘FtCYP81-a’ and ‘FtCYP81-b’, exhibit functional divergence despite their high sequence similarity. ‘FtCYP81-a’ is regulated via the jasmonic acid signaling pathway by the interaction between the FtMYB2 transcription factor and the virulence protein Rs12, primarily enhancing quercetin accumulation in roots to improve resistance to Rhizoctonia solani. In contrast, ‘FtCYP81-b’ is modulated by transcription factor FtNAC2 and specifically influences quercetin levels in seeds, thereby affecting seed size. These findings reveal a novel mechanism by which gene duplication drives functional specialization in secondary metabolism and provide crucial genetic targets for the synergistic improvement of disease resistance and yield in Tartary buckwheat breeding.