Effects of DNA methyltransferase inhibitor on fruit quality revealed by integrated DNA methylome analysis in Ziziphus jujuba cv. Dongzao

Ziziphus jujuba cv. Dongzao is a late-maturing fresh-eating jujube variety unique to China. DNA methylation plays a crucial regulatory role in its fruit development and quality formation. To investigate the effects of the DNA methylation inhibitor 5-azacytidine (5-azaC) on fruit development, quality formation, and methylation regulation in jujube, this study used fruits at the onset of coloration, corresponding to the transition from the white-ripe stage to the half-red stage, as experimental material and compared the color-changing state, quality indicators, physiological characteristics, and genome-wide methylation changes after treatment with different concentrations of 5-azaC. The results showed that 5-azaC promoted earlier color-changing in jujube fruits and improved their appearance, flavor, texture, and antioxidant physiological state. The 50 μmol·L –1 treatment showed the best overall effect, manifested as increased single-fruit weight, significantly improved sugar content, vitamin C, and soluble solids content, decreased acid content, firmness, and cracking force, enhanced POD, SOD, and CAT activities, and lower MDA accumulation. WGBS analysis showed that 5-azaC treatment reduced the whole-genome methylation level of jujube fruit and induced differential methylation changes in the CG, CHG, and CHH sequence backgrounds and gene functional regions. GO and KEGG enrichment results indicated that DMGs are mainly involved in basal metabolism, secondary metabolism, plant hormone signal transduction, redox regulation, and stress response. In conclusion, appropriate concentrations of 5-azaC altered DNA methylation patterns and were associated with changes in jujube ripening, coloration, and overall fruit quality. These findings provide preliminary epigenetic evidence for understanding the potential relationship between DNA methylation changes and fruit quality formation.