Role of DNA methylation dynamics in desiccation and salinity stress responses in rice cultivars

DNA methylation is an epigenetic mark that controls gene expression in response to internal and environmental cues. In this study, we sought to understand the role of DNA methylation in response to desiccation and salinity stresses in three rice cultivars (IR64, stress-sensitive; Nagina 22, drought-tolerant and Pokkali, salinity-tolerant) via bisulphite sequencing. We identified DNA methylation patterns in different genomic/genic regions and analysed their correlation with gene expression. Methylation in CG context within gene body and methylation in CHH context in distal promoter regions were positively correlated with gene expression. However, methylation in other sequence contexts and genic regions was negatively correlated with gene expression. DNA methylation was found to be most dynamic in CHH context under stress condition(s) in the rice cultivars. The expression profiles of genes involved in de-novo methylation were correlated with methylation dynamics. Hypomethylation in Nagina 22 and hypermethylation in Pokkali in response to desiccation and salinity stress, respectively, were correlated with higher expression of abiotic stress response related genes. Our results suggest an important role of DNA methylation in abiotic stress responses in rice in cultivar-specific manner. This study provides useful resource of DNA methylomes that can be integrated with other data to understand abiotic stress response in rice.