Melatonin-induced ZjWRKY11 and ZjWRKY7 regulate triterpenoid biosynthesis in jujube (Ziziphus jujuba Mill.)

Introduction Triterpenoids are key bioactive metabolites in jujube ( Ziziphus jujuba Mill.), yet their regulatory mechanisms remain unclear. Methods In this study, jujube samples were treated with exogenous melatonin (MT), and triterpenoid accumulation was measured. Transcriptomic analysis was performed to identify differentially expressed genes in response to MT treatment. Key biosynthetic genes and transcription factors were further validated through overexpression and silencing assays, and promoter binding was examined to elucidate the regulatory mechanism. Results Exogenous MT markedly enhanced the accumulation of major pentacyclic triterpenoids, with MT accumulation preceding triterpenoid biosynthesis. Transcriptomic analysis revealed that differentially expressed genes were significantly enriched in secondary metabolic pathways. Integrated analysis identified key biosynthetic genes ( ZjHMGR and ZjOSC1 ) and MT-responsive WRKY transcription factors, particularly ZjWRKY11 and ZjWRKY7 , that were strongly associated with triterpenoid accumulation. Functional assays demonstrated that overexpression of ZjWRKY11 and ZjWRKY7 markedly enhanced triterpenoid accumulation, whereas their silencing resulted in a significant reduction. Mechanistically, both transcription factors directly activated ZjHMGR and ZjOSC1 by binding to their promoters, with ZjWRKY11 showing stronger activation. Discussion Collectively, our findings suggest that MT induces the expression of ZjWRKY11 and ZjWRKY7 , which positively regulate triterpenoid biosynthesis and may contribute to MT-associated triterpenoid accumulation through the activation of key biosynthetic genes. These findings provide insights into the transcriptional regulation of secondary metabolism and identify potential targets for future metabolic engineering efforts.