Exogenous ABA regulates stress tolerance of Leymus chinensis via modulation of PYL‑mediated signaling and antioxidant enzymes.

As an important species for ecological restoration and high-quality forage in northern China, Leymus chinensis has drawn considerable research interest regarding its stress tolerance regulatory mechanisms. Exogenous abscisic acid (ABA), a key stress-signaling hormone, can effectively pre-activate the antioxidant defense system in L. chinensis. To elucidate the ABA response mechanism, this study combined physiological assessments-including antioxidant enzyme activities-with transcriptome sequencing of ABA-treated plants. The results demonstrated that ABA treatment enhanced the activities of peroxidase, superoxide dismutase, and catalase in leaves while reducing malondialdehyde content. Transcriptomic analysis further revealed that ABA induced extensive gene expression reprogramming, with significant enrichment in pathways such as plant hormone signal transduction. Subsequently, 21 PYL gene family members (LcPYLs) were identified for the first time in the L. chinensis genome. Systematic characterization indicated that these genes possess conserved structures, contain promoter regions enriched in stress-responsive elements such as ABRE, and are phylogenetically closer to PYLs in rice. Expression profiling confirmed that multiple LcPYLs were significantly upregulated under both exogenous ABA and low-temperature stress. Collectively, this study reveals that exogenous ABA may improve stress tolerance in L. chinensis, which is potentially associated with the activation of the antioxidant system and PYL-mediated signaling. These findings provide valuable genetic resources and a theoretical reference for future molecular breeding of stress-resilient L. chinensis varieties.