RgMYC2 promotes catalpol biosynthesis by regulating Rg10HGO in Rehmannia glutinosa

Catalpol, one of the major bioactive components in the traditional Chinese medicinal herb Rehmannia glutinosa, exhibits multiple pharmacological activities such as hypoglycemic and neuroprotective effects. Consequently, mechanistic elucidation of catalpol biosynthesis regulation in R. glutinosa is critically important. In this study, we identified RgMYC2, a basic helix-loop-helix (bHLH) transcription factor that is localized in the nucleus and exhibits transcriptional activation activity. Functional validation demonstrated that RgMYC2 overexpression significantly enhanced catalpol content in both the roots and leaves of R. glutinosa. This increase was concomitant with the upregulation of Rg10HGO, a gene encoding a key enzyme in the catalpol biosynthetic pathway. Mechanistic studies using yeast one-hybrid (Y1H), electrophoretic mobility shift assay (EMSA), and dual-luciferase reporter assays indicated that RgMYC2 binds to and transcriptionally activates the Rg10HGO promoter. Moreover, Rg10HGO overexpression significantly increased catalpol content in R. glutinosa roots and leaves, whereas its silencing led to a marked reduction, further confirming its pivotal role in catalpol biosynthesis. These findings demonstrate a functional RgMYC2-Rg10HGO regulatory module that promotes catalpol biosynthesis in R. glutinosa.