ABA-mediated salt tolerance in Astragalus cicer: From physiological-biochemical responses to key regulatory networks identified by transcriptome profiling and WGCNA.

Abstract

Soil salinization severely constrains the productivity of leguminous forages, but the regulatory mechanisms of salt acclimation in Astragalus cicer remain unclear. Here, we investigated the ABA-dependent salt tolerance network in this species through integrated physiological, biochemical, and transcriptomic analyses under controlled stress conditions, including salt treatment, exogenous ABA supplementation, and chemical inhibition of endogenous ABA synthesis. Our results show that exogenous ABA effectively mitigates salt-induced growth inhibition, enhances antioxidant capacity, preserves photosynthetic function, and maintains ion homeostasis, whereas blocking ABA biosynthesis exacerbates salt damage. Transcriptome profiling combined with co-expression network analysis revealed that ABA orchestrates salt responses primarily through hormone signaling and MAPK pathways. We identified several hub genes (e.g., AcMKK4_5, AcPPDK, AcGAPDH) and validated key components of the canonical ABA signaling cascade (AcPYL1, AcSnRK2s, AcABF2) as potential master regulators linking ABA perception to metabolic and stress adaptation in A. cicer. Collectively, these findings establish that exogenous ABA improves salt tolerance in A. cicer by coordinating antioxidant defense, photosystem protection, ion balance, and carbon metabolic remodeling. This work provides mechanistic insights and candidate genetic targets for breeding stress-resilient forages and restoring saline-alkali lands.