Hydrogen sulfide primes drought tolerance in plants by metabolic control of DNA methylation

Hydrogen sulfide (H₂S) is a gasotransmitter that contributes to plant stress responses. In this study, we investigated the mechanisms underlying H₂S-induced priming in rice drought tolerance. Combining transcriptomic and epigenomic analyses, we show that H₂S pretreatment establishes a coordinated regulatory program associated with enhanced stress resilience. H₂S attenuated drought-induced transcriptional changes while promoting the expression of dehydrin genes, a hallmark of the primed state. Under non-stress conditions, H₂S triggered sustained transcriptional reprogramming, including activation of stress-related transcription factors and repression of cell wall-associated genes. Whole-genome bisulfite sequencing revealed global DNA hypomethylation accompanied by increased CG methylation within gene bodies. Metabolite analyses showed that H₂S reduces S-adenosylmethionine levels without affecting S-adenosylhomocysteine, thereby lowering cellular methylation capacity; restoring SAM-reversed DNA hypomethylation. These findings indicate that H₂S primes drought tolerance through metabolic control of DNA methylation, linking sulfur signaling to epigenetic regulation.