DNA methylation variations induced by salt and alkali stresses and their differential responses in Tamarix chinensis L.

Soil salinization is a critical environmental challenge threatening plant survival. To adapt, certain plants have evolved tolerance to highly saline-alkali environments through long-term natural selection. Tamarix chinensis L., a typical halophyte with strong adaptability to salt and alkali stresses, serves as an essential germplasm resource and pioneer species for ecological conservation and remediation. However, the epigenetic mechanisms underlying its stress tolerance remain poorly understood. In this study, we systematically characterized the tolerance and genome-wide DNA methylation variations in T. chinensis under diverse salt and alkali stresses conditions. Phenotypic observations manifested severe leaf damage under 150 mM alkali stress over 10 days, whereas only slight injury occurred under 400 mM salt stress, indicating superior tolerance to salinity over alkalinity. MSAP analysis revealed that salt stress predominantly triggered genome-wide demethylation; conversely, alkali stress primarily induced hypermethylation, with both variations occurring mainly at CNG sites. Notably, DNA methylation alterations were more extensive under salt stress. Sequencing of methylation-variant bands yielded 17 stress-related sequences, eight of which are homologous to known stress-responsive genes. These findings provide a theoretical framework for dissecting differential epigenetic responses to salt and alkali stresses, facilitate the mining of resistance genes, and offer epigenetic references for the molecular breeding of T. chinensis to and ecological remediation of saline-alkaline lands.