FtMYB6, a Light-Induced SG7 R2R3-MYB Transcription Factor, Promotes Flavonol Biosynthesis in Tartary Buckwheat (<i>Fagopyrum tataricum</i>)

Abstract

Tartary buckwheat (<i>Fagopyrum tataricum</i>) is rich in flavonols, which are thought to be highly beneficial for human health. However, little is known about the regulatory mechanism of flavonol biosynthesis in Tartary buckwheat. In this study, we identified and characterized a novel SG7 R2R3-MYB transcription factor in Tartary buckwheat, FtMYB6. We showed that <i>FtMYB6</i> is located in the nucleus and acts as a transcriptional activator. The <i>FtMYB6</i> promoter showed strong spatiotemporal specificity and was induced by light. The expression of <i>FtMYB6</i> showed a significant correlation with rutin accumulation in the roots, stems, leaves, and flowers. Overexpression of <i>FtMYB6</i> in transgenic Tartary buckwheat hairy roots and tobacco (<i>Nicotiana tabacum</i>) plants significantly increased the accumulation of flavonols. In transient luciferase (LUC) activity assay, FtMYB6 promoted the activity of <i>FtF3H</i> and <i>FtFLS1</i> promoters and inhibited the activity of the <i>Ft4CL</i> promoter. Collectively, our results suggest that FtMYB6 promotes flavonol biosynthesis by activating <i>FtF3H</i> and <i>FtFLS1</i> expression.