Dynamic Changes Of DNA Methylation And Gene Expression During Bud Dormancy Release Of Tea Plant Xinyang 10 Overwintering

Bud dormancy,an important adaptive mechanism for most temperate perennials to resist the cold environment in winter,is essential for the normal growth and development of plants.DNA methylation is an important way to regulate gene expression in plants.Previous studies have shown that DNA methylation is widely involved in regulating the process of bud dormancy release in plant,but its regulatory role in tea plant bud dormancy release process remains unclear.Therefore,this study revealed the dynamic changes in gene expression and methylation level during the bud dormancy release process of tea plant Xinyang 10 and analyzed the key methylation regions and types that affect gene expression through the combined analysis of transcriptome and methylation group,providing the data support for tea dormancy release and germination,and laying a foundation for subsequent research.The main results of this study are as follows:(1)Significant differences in gene expression at different stages during bud dormancy release of tea plant Xinyang 10.Sequencing,quality control and gene expression correlation were conducted on the terminal buds at the pre dormancy stage(HQ),deep dormancy stage(HS),germination stage(MD)and leaf extension stage(ZY)in the process during bud dormancy release of tea plant Xinyang 10 overwintering.It was found that the internal biological reproducibility was strong in each stage,and the sample correlation coefficient was greater than 0.96.Through the analysis of gene expression differences,it was found that there were significant differences in gene expression of tea plant Xinyang 10 overwintering before and after bud dormancy release,among which some gene expression characteristics were significant during the deep dormancy stage,with significant differences compared to other stage,and the highest number of gene expressions were detected during the deep dormancy stage.(2)The expression of growth-related genes was active of tea plant Xinyang 10 after bud dormancy release.The number of DEGs between the deep dormancy stage and germination stage,leaf extension stage were relatively large,with 5341 and 5922,respectively.The number of DEGs in the germination stage and leaf expansion stage was the lowest,with a total of 241.DEGs were significantly enriched in ribosome and cell proliferation before and after dormancy release.Genes with elevated expression levels after dormancy release were closely related to plant growth,such as DNA replication,protein synthesis,cell proliferation;DEGs with high expression level before dormancy release were related to transmembrane transport and stress response;DEGs whose expression level increased continuously during the process of bud dormancy release were mainly involved in photosynthesis and carbohydrate synthesis.(3)Low correlation between CHH and CG,CHG methylation types before and after bud dormancy release of tea plant Xinyang 10.The average methylation rates in CG,CHG and CHH sequences were 83.63%,69.18% and 7.80%,respectively.After dormancy release,DNA methylation levels decreased.The Pearson correlation coefficient between the two samples of each stage was higher than 0.91 under the three sequence backgrounds,and the methylation patterns between m CG and m CHG were similar,while the methylation patterns between m CHH and m CG,m CHG were significantly different.(4)Different types of DNA methylation showed significant differences of tea plant Xinyang 10 before and after bud dormancy release.In this study,whole genome methylation profiles of CG,CHG and CHH were constructed during bud dormancy release of tea plant Xinyang 10.It was found that there were no significant differences in CG methylation levels before and after dormancy release,while differences in CHG and CHH genome methylation levels were significant.Differential methylation regions(DMRs)analysis showed that there were more DMRs between deep dormancy and the other three stages,and DMRs were mainly distributed in CHH DNA methylation.(5)CHH methyl was closely related to gene expression during bud dormancy release of tea plant Xinyang 10.We analyzed the relationship between DMRs and DEGs in three different methylation types,and the results showed that DMRs of CHH methylation type were associated with more DEGs.A total of 80 DEGs related to DNA methylation pathway were screened,and the expression level of most genes related to DNA methylation pathway was higher after dormancy release than before.The decrease in methylation levels of the CHG and CHH regions after dormancy release was strongly correlated with the increase in gene expression level.In conclusion,during the bud dormancy release process of tea plant Xinyang 10,the level of DNA methylation decreased,and genes related to the methylation pathway promoted the formation and stability of methylation.The whole genome methylation profile of tea plant Xinyang 10 during bud dormancy release was constructed to reveal the dynamic changes of DNA methylation during dormancy release.Analysis of the association between methylation changes in different gene regions and gene expression revealed that CHG and CHH are key methylation regions and methylation types that affect gene expression.These results reveal the role of DNA methylation in the process of tea plant bud dormancy release,which has potential theoretical and applied value in the fields of early tea plant germination and early tea leaf market.