Molecular analysis of the role of methyl jasmonate in carotenoid biosynthesis in oriental melons (Cucumis melo) during storage

• Postharvest application of methyl jasmonate (MeJA) markedly increased carotenoid levels in oriental melon ( Cucumis melo . L) peel. • During the postharvest ripening of oriental melon, the MeJA-regulated key gene CmPYS1 for carotenoid biosynthesis interacts with CmNAC10 transcription factors, and CmNAC10 factors interact with miRNA164b. • MeJA stimulates carotenoid accumulation in oriental melon through a regulatory cascade: suppression of miRNA164b expression elevates CmNAC10 levels, which subsequently enhances CmPYS1 expression. Methyl jasmonate (MeJA) has diverse effects on the preservation and quality of postharvest fruits. However, it remains unclear whether these effects are mediated by miRNAs and mRNAs. The present study aimed to provide insights into the effect of MeJA on peel carotenoid content in “Huaguniang” oriental melon fruit ( Cucumis melo L.) by molecular analysis. Transcriptome and degradome analyses revealed 3571 mRNAs and 16 miRNAs of differentially expressed genes (DEGs) induced by MeJA. A weighted gene co-expression network analysis (WGCNA) divided the DEGs into 7 modules. WGCNA revealed that the "darkturquoise" module exhibited the strongest correlations with 4 major carotenoids. A transcriptional regulatory network was constructed using CmPYS1 , a carotenoid-associated differentially expressed gene from this module. Analysis of the CmPYS1 promoter identified NAC-binding motifs, while yeast two-hybrid assays confirmed the interaction between CmPYS1 and CmNAC10 within the module. Dual-luciferase assays in tobacco further demonstrated that MeJA-suppressed miRNA164 interacts with CmNAC10. Collectively, our findings indicate that MeJA stimulates carotenoid accumulation in oriental melon through a regulatory cascade: suppression of miRNA164 expression elevates CmNAC10 levels, which subsequently enhances CmPYS1 expression. This study elucidates the molecular mechanisms through which MeJA regulates carotenoid biosynthesis.