Genome-wide DNA methylation dynamics and RNA-seq analysis during grape (cv. 'Cabernet Franc') skin coloration.

This study generated whole genome DNA methylation maps to characterize DNA methylomes of grape (cv. 'Cabernet Franc') skins and examine their functional significance during grape skin coloration. We sampled grape skin tissues at three key stages (the early stage of grape berry swelling, the late stage of grape berry swelling and the veraison) during which the color of grape berries changed from green to red. DNA methylation levels of grape skins at the three stages were higher in transposable element regions than in the genic regions, and the CG and CHG DNA methylation levels of the genic region were higher than the CHH DNA methylation levels. We identified differentially methylated regions (DMRs) in S2_vs_S1 and S3_vs_S1. The results indicated that DMRs predominantly occurred within the CHH context during grape skin coloration. Many gene ontology (GO)-enriched DMR-related genes were involved in "nucleotide binding," "catalytic activity" and "ribonucleotide binding" terms; however, many KEGG-enriched DMR-related genes were involved in the "flavonoid biosynthesis" pathway. Our results could provide an important foundation for future research on the development mechanism of grape berries.