Integrated transcriptomic and metabolomic reveal the metabolic basis and regulatory networks of triterpenoids biosynthesis in Ziziphus jujuba Mill. cv. Junzao fruits during different harvest times

Triterpenoids are the primary bioactive constituents responsible for the medicinal efficacy of Ziziphus jujuba Mill. cv. Junzao (Z. jujuba cv. Junzao) fruits. However, the metabolic characteristics and dynamic accumulation patterns of triterpenoids during fruit development remain poorly understood. This study employed integrated metabolomics and transcriptomics approaches to elucidate triterpenoid accumulation in Z. jujuba cv. Junzao fruits across five developmental stages. Total triterpenoid content exhibited a stage-specific accumulation pattern, peaking at YG, declining sharply by 37% at PD, rebounding at BS, and gradually decreasing through CS and WS stages. A total of 347 terpenoid differentially accumulated metabolites (DAMs) and 18,926 differentially expressed genes (DEGs) were identified, among which triterpenes (138, 33.91%) and triterpene saponins (86, 21.13%) were predominant. Multiple terpenoid biosynthesis pathways were significantly enriched in KEGG analysis of DEGs and DAMs. Weighted gene co-expression network analysis (WGCNA) identified six key modules (salmon, midnightblue, black, blue, yellow, and brown modules) strongly correlated with triterpenoid accumulation. Furthermore, integrated correlation analysis revealed that cytochrome P450 family genes, particularly CYP716A, CYP716C49, CYP716C53/55, CYP72A397, CYP88A, and CYP88D, were likely hub genes governing triterpenoid biosynthesis, with RT-qPCR validation of eight key genes confirming the transcriptome data. These findings provide a comprehensive framework for understanding triterpenoid biosynthesis and offer theoretical foundations for optimizing harvest timing and advancing metabolic engineering in Z. jujuba cv. Junzao fruits.