• Azacytidine (5-Aza) treatment significantly promotes postharvest melon ripening. • Fruit demethylation upregulates the ethylene biosynthesis and signaling pathwaypathway ( ACO, ACS, ERF ). • DNA hypomethylation activates key aroma biosynthetic genes ( LOX, ADH, AAT ). DNA demethylation is an essential epigenetic mechanism responsible for regulating the ripening and quality of fruit, yet its role in postharvest ethylene and volatile formation in oriental melon ( Cucumis melo var. Makuwa) remains largely unexplored. This study combined multi-omics analysis with epigenetic intervention to systematically investigate how DNA methylation affects fruit ripening by regulating ethylene and volatile production. The promoter methylation levels of several core genes related to ethylene and aliphatic aromatic compound biosynthesis, including LOX (MELO3C011885 and MELO3C024348), ADH (MELO3C011043), AAT (MELO3C024771 and MELO3C024007), and ACO (MELO3C007425 and MELO3C026436), were negatively correlated with transcriptional activity. DNA methyltransferase-encoding gene ( CMT, MET , and DRM ) expression declined during postharvest ripening, whereas that of the gene encoding the demethylase ( DML ) was significantly upregulated on day 7. Treatment with DNA demethylation agent (5-azacytidine, 5-Aza) improved the ester content by 2.1-fold, enhanced lipoxygenase and alcohol dehydrogenase activities by 1.8- and 2.3-fold, and up-regulated ethylene production by up to 1.9-fold. In conclusion, DNA methylation dynamically regulates the expression of lipid metabolism and ethylene biosynthesis pathway genes, thereby significantly influencing the accumulation of aliphatic aromatic compounds and ethylene production in oriental melons. The findings provide insights into epigenetic mechanisms that can be targeted for fruit quality improvement.
Guo et al. (Sun,) studied this question.