The Light-Regulated SsMYB106 Transcription Factor Promotes Flavonoids in Spatholobus suberectus

<i>Spatholobus suberectus</i> Dunn is rich in flavonoids, which were previously demonstrated to respond to changing light conditions. In this study, through weighted gene co-expression network analysis (WGCNA), <i>MYB</i> genes were screened as the potential regulator for these light-intensity-induced changes. One <i>MYB</i> gene, <i>SsMYB106</i>, was chosen for in-depth research. Analysis showed that <i>SsMYB106</i> was an R2R3-type MYB transcription factor, regulated by light, and involved in controlling the light responses of <i>S. suberectus</i>. <i>SsMYB106</i> was then transiently overexpressed in <i>S. suberectus</i> flowers and stably overexpressed in <i>Nicotiana benthamiana</i> Domin. <i>SsMYB106</i> overexpression promoted flavonoids (especially catechins) accumulation, and affected expressions of all the flavonoid biosynthetic pathway genes. In transient overexpression, <i>SsDFR1</i> was the only significantly decreased gene, while other 17 genes were significantly increased. In stable overexpression, nearly all genes were upregulated or at least unchanged. <i>SsMYB106</i> overexpression also might function in inhibiting anthocyanin and lignin biosynthesis. This study deepens our understanding of <i>SsMYBs</i> gene functions in regulating and enhancing flavonoids, and would be beneficial for designing high-valued <i>S. suberectus</i> in future.