Melatonin promotes notoginsenosides accumulation via a PnHSP17/PnJAZ5-PnWRKY11–PnSE regulatory module in Panax notoginseng

Melatonin is recognized as a regulator that enhances notoginsenosides accumulation in Panax notoginseng , yet the underlying molecular mechanisms remain poorly understood. Here, we demonstrate that melatonin treatment increases notoginsenosides levels in both whole plants and callus tissues. Transcriptomic analysis identified the PnWRKY11 as a melatonin-responsive regulator. The overexpression of PnWRKY11 in calli upregulated PnFPS, PnSE, and PnDS expression and significantly promoted notoginsenosides accumulation. Subsequent analyses verified that PnWRKY11 binds to the PnSE promoter and positively regulates its transcription. Yeast two-hybrid screening revealed PnHSP17 or PnJAZ5 as PnWRKY11-interacting proteins, which was validated by yeast dot and co-immunoprecipitation assays. Functional studies showed that PnJAZ5 represses PnWRKY11-mediated transactivation of PnSE , while melatonin alleviates this repression by inducing jasmonic acid (JA) biosynthesis—upregulating PnLOX4/5 and elevating endogenous JA, leading to PnJAZ5 degradation. In parallel, melatonin-induced PnHSP17 enhances the transcriptional activity of PnWRKY11. The results identify a dual-pathway regulatory mechanism through which melatonin enhanced notoginsenosides accumulation: by relieving PnJAZ5-mediated repression via JA signaling and by potentiating PnWRKY11 activity through PnHSP17. This study provides mechanistic insight into melatonin-mediated metabolic regulation and supports its potential application in P. notoginseng cultivation.