Effects of 24-Epibrassinolide on DNA Methylation Variation in Soybean (Glycine max) Leaf and Root Under Saline-Alkali Stress

Saline-alkali stress is major stress that severely reduces plant growth and productivity, it is necessary to make clear whether exogenous 24-epibrassinolide (EBR) can improve the salt-alkali resistance of soybean (Glycine max) by affecting its DNA methylation. In this study, the effects of EBR on soybean adaptation to saline-alkali stress, genomic DNA methylation level and pattern changes in saline-alkali-stressed leaf and root with or without EBR treatment were compared using methylation-sensitive amplified polymorphism (MSAP). In the results, saline-alkali stress increased DNA methylation levels in leaf and root, with higher respective hemi-methylation and global methylation rates observed in leaf (6.22, 22.24%) than root (5.72, 21.76%). EBR application reduced leaf and root DNA methylation levels, with leaf hemi-methylation rate (6.15%) exceeding that of root (4.25%) and leaf global methylation rate (21.79%) below that of root (22.51%). There were distinct DNA remethylation and demethylation variations across different tissues and treatments, demethylation in leaves was dominant. Meanwhile, untreated saline-alkali-stressed roots exhibited major demethylation-based variations, while remethylation variations predominated post-treatment. Under saline-alkali stress, root remethylation and demethylation rates (6.17, 7.55%, respectively) both exceeded respective leaf rates (5.18 and 7.46%); however, post-EBR treatment, root methylation rate (6.45%) exceeded leaf rate (5.38%), while root demethylation rate (6.13%) fell below leaf rate (6.94%). In conclusion, exogenous EBR application to saline-alkali-stressed soybean can influence leaf and root genomic DNA methylation levels and patterns via distinct tissue-specific methylation mechanisms.