The global dynamic of dna methylation in response to heat stress revealed epigenetic mechanism of heat acclimation in Saccharina japonica.

Saccharina japonica is an ecologically and economically important kelp in cold-temperate region. When it is cultivated on a large scale in the temperate and even subtropical zones, heat stress is a frequent abiotic stress. This study is the first attempt to reveal the regulatory mechanism of the response to heat stress from the perspective of DNA methylation in S. japonica. We firstly obtained the characteristics of variation in the methylome under heat stress, and found that heat stress caused a slight increase in the overall methylation level and methylation rate, especially in the non-coding regions of the genome. Secondly, we found that methylation was probably one of factors affecting the expression of genes, and the methylation within the gene body was positively correlated with the gene expression (rho=0.0784). Moreover, it was found that among the differentially expressed genes regulated by methylation, many genes were proved to be related to heat stress response, such as HSP gene family, genes of antioxidant enzymes, genes related to proteasome-ubiquitination pathway and plant cell signaling pathways, etc. This study demonstrated that DNA methylation is involved in regulating the response to heat stress, laying a foundation for studying the acclimation and adaptation of S. japonica to heat stress from an epigenetic perspective.