Salt priming coordinates transcriptional and epigenetic states for enhanced salt tolerance in mung bean (Vigna radiata).

Soil salinization threatens sustainable agriculture by reducing crop growth and yield. Stress priming, in which seedlings experience mild salt treatment followed by recovery before re-exposure, can enhance tolerance, but its molecular basis in legumes is unclear. Here, we used mung bean (Vigna radiata) to compare primed and non-primed plants under subsequent salt stress. Primed plants rapidly accumulated proline, activated antioxidant enzymes, and maintained lower Na⁺/K⁺ ratios at early stages. During intermediate stress, defense- and hormone-related transcripts remained elevated, sustaining physiological advantages. At later stages, primed plants preserved chlorophyll, reduced malondialdehyde accumulation, and limited electrolyte leakage, coinciding with persistently accessible stress-responsive promoters enriched for bZIP class A-like motifs. Genome-wide DNA methylation diverged, with primed plants retaining higher CpG, CHG, and CHH methylation and upregulating heterochromatin maintenance factors. These results reveal a temporal, multi-layer regulatory framework linking transcription, chromatin accessibility, and DNA methylation that underpins salt priming in mung bean.