Integrated Analysis of DNA Methylation and Transcriptomic Dynamics in the Grape Variety ‘Cabernet Franc’ at Early and Late Stages of Fruit Development

DNA methylation is a key epigenetic regulator in plant development. However, the changes in methylation patterns between the early and late stages of grape berry development, the two phases with the most pronounced morphological differences, and the respective roles of methylation at these stages remain largely unexplored. To investigate the dynamic DNA methylation changes during this stage and their regulatory role in fruit development, we constructed genome-wide methylation maps of grape at two key time points: the early development stage (7 days after flowering, 7DAF; hereafter referred to as S1) and the late development stages (78 days after flowering, 78DAF; hereafter referred to as S2). Global cytosine methylation increased from 12.57% (S1) to 14.16% (S2), driven primarily by a substantial increase in CHH methylation (from 5.88% to 7.92%; p < 0.001), whereas CG and CHG methylation showed no statistically significant change. Most differentially methylated regions (DMRs) were hypermethylated in S2, predominantly in the CHH context. Integrative methylome and transcriptome analysis revealed that CHH hypermethylation was associated with the downregulation of YABBY5 (a berry size repressor) and upregulation of UGPase (a cell wall biosynthesis gene), suggesting a potential regulatory role in fruit expansion. Because our study compares only two time points, it cannot distinguish between gradual and stage-specific methylation changes, and functional validation of the identified genes is required. Nevertheless, these findings provides a valuable resource for understanding stage-specific DNA methylation dynamics and their association with gene expression during grape berry development.