DNA Methylation and mRNA Exon Sequence Variations in the Salt Stress Adaptation of Paspalum vaginatum

Background: DNA methylation, as an epigenetic modification, is crucial in the regulatory mechanism of salt resistance in plants. Methods: To gain deeper insight into the relationship between DNA methylation and mRNA exons in halophytes and their potential roles in regulating salt tolerance, this study employed whole-genome bisulfite sequencing (WGBS) and transcriptome sequencing data to analyze the leaves of the halophyte Paspalum vaginatum, widely distributed in tropical regions. Results: The findings revealed that the methylation level of 5-methylcytosine (5mC) in the genomic elements of P. vaginatum increased with prolonged salt treatment under salt stress conditions. This observation suggested that the methylation level plays a pivotal role in the salt stress response of P. vaginatum. Notably, under salt stress, the number of variants at the mRNA exon level was significantly higher than that at the DNA level. Furthermore, comparative analysis revealed sequence variants within exonic regions of mature mRNA transcripts for several genes in salt-treated samples relative to pre-stress controls, and these changes were found to be enriched in several salt-tolerance pathways, including unsaturated fatty acid metabolism and ascorbic acid metabolism, among others. Further analysis demonstrated that the occurrence of these variants changed concomitantly with the dynamic changes in CG methylation levels in the gene body of some salt-tolerant genes. Therefore, it was speculated that mRNA exon variations probably promoted the elevation of CG 5mC methylation levels at the DNA level under salt stress conditions, further enabling the plant to adapt to the salt-stress environment. Conclusions: These findings offer preliminary insights into the relationship between DNA methylation and mRNA exon variations in P. vaginatum under salt stress, providing valuable information and avenues for further investigation into the regulatory role of mRNA in DNA methylation.