Jasmonate-responsive transcription factor StMYC2 coordinately regulates peltate glandular trichome development and monoterpenoid biosynthesis in Schizonepeta tenuifolia

Schizonepeta tenuifolia is a medicinal plant whose bioactive monoterpenoids, such as pulegone, are biosynthesized and stored in peltate glandular trichomes. Although jasmonate signaling is known to promote trichome development and terpenoid accumulation, the underlying transcriptional regulators in S. tenuifolia remain unknown. Here, we identified two jasmonate-responsive MYC2-type transcription factors, StMYC2a and StMYC2b, which are predominantly expressed in leaves and localized to the nucleus. Overexpression of StMYC2a and StMYC2b in S. tenuifolia increased the peltate glandular trichome density and monoterpenoid content. Conversely, transgenically silenced StMYC2a and StMYC2b lines had attenuated peltate glandular trichome development and reduced monoterpenoid accumulation. We further demonstrated that StMYC2a and StMYC2b directly activate two key monoterpenoid biosynthetic genes, StL3OH and StPR, by binding to G-box motifs in their promoters. Protein interaction analysis reveals that only StMYC2b physically interacts with the repressor StJAZ2, which suppresses StMYC2b-mediated transactivation, but this repression was alleviated upon stimulation with methyl jasmonate. The results revealed that the StJAZ2-StMYC2b-StL3OH/StPR functional module regulates jasmonic acid signaling-mediated glandular trichome development and monoterpenoid synthesis in S. tenuifolia. The enrichment of the transcriptional regulatory network for monoterpenoid synthesis provides a new theoretical basis for producing S. tenuifolia with high medicinal value.