Cyanamide Releases Buds Dormancy of ‘Shuijing’ Grapevine via DNA Methylation Reduction

Shuijing' grape is a deciduous vine fruit tree, and the low-temperature period during winter is required for its sprouting.Global warming has been associated with substantially decreased grape yields and lower grape quality because it reduces the low temperatures needed for grape dormancy.Treatment with cyanamide can efficiently cause the grape hibernacle's dormant release.However, the underlying epigenetic mechanisms remain unknown.This study collected mature branches of the annual 'Shuijing' grape and treated them with 2.5% cyanamide (on sprouts and joints).The treatment-induced sprouting and the physiological indices (e.g., soluble sugar, starch, and protein content) were measured.Whole-genome bisulfite sequencing (WGBS) was used for whole-genome differential methylation.The results demonstrated that following cyanamide treatment, sprouting and appearance of primordia occurred earlier, starch content decreased, and protein content and the bud axis increased during grape sprouting, facilitating flower-bud differentiation and inflorescence integrity.Cyanamide application resulted in a drop in DNA methylation levels in grapevine buds, particularly in the CHH methylation.This led to an increase in hypo-DMRs (regions with reduced methylation) and a decrease in hyper-DMRs (regions with higher methylation), ultimately resulting in the up-regulation of genes associated with sprouting.Biological processes (e.g., regulation of transcription, DNA-templated), cellular components (e.g., nucleus, plasma membrane, cytoplasm), and molecular functions (e.g., protein binding, ATP binding) involved in the dormancy release of grape were significantly enriched.Cyanamide treatment facilitated latent release since it damages the cell membrane and lipid structures of grapevine buds.Additionally, cyanamide treatment reduced DNA methylation levels of latent buds of the 'Shuijing' grapevine.The methylation traits associated with the 'Shuijing' grapevine aid in comprehending the molecular pathways involved in easing dormancy and encouraging bud differentiation.This work offers epigenetic references to understand the fundamental mechanisms involved in escaping dormancy in fruit trees.