Exogenous γ-aminobutyric acid mitigates physiological and transcriptomic responses of Prunus mongolica under combined alkali salt and cadmium stress

Introduction Prunus mongolica is a relict xerophytic shrub important for desert ecosystem stability and vegetation restoration in arid regions. However, its adaptive mechanisms under combined alkali salt and cadmium stress remain unclear. This study investigated the regulatory role of exogenous γ-aminobutyric acid (GABA) in stress tolerance under single and combined stresses. Methods In this study, seedlings were subjected to alkali salt, cadmium, and combined stress treatments, followed by foliar application of GABA. Germination, growth, physiological traits, and transcriptomic responses were analyzed using an integrated multi-level approach. Results The alkali salt, cadmium, and combined alkali salt and cadmium stress significantly inhibited germination and growth, with combined stress showing the strongest effects. Stress induced reactive oxygen species accumulation, lipid peroxidation, and photosynthetic inhibition. Exogenous γ-aminobutyric acid alleviated these effects by improving germination, growth, chlorophyll content, and root activity, while reducing oxidative damage. It enhanced osmotic adjustment via increased proline and soluble sugars and strengthened antioxidant enzyme activities, including superoxide dismutase, peroxidase, catalase, ascorbate peroxidase, and glutathione reductase, restoring redox homeostasis. Discussion Transcriptome analysis showed that GABA reprogrammed stress-responsive genes enriched in “MAPK signaling pathway–plant”, “Plant hormone signal transduction”, “Plant–pathogen interaction”, “Peroxisome”, and “Glutathione metabolism” pathways. Gene set enrichment analysis further indicated recovery of photosynthesis, carbon metabolism, and primary “metabolic process”, suggesting restoration of energy balance and metabolic homeostasis. Collectively, GABA functions as a multi-level regulator integrating redox balance, signaling pathways, and metabolic reprogramming to enhance stress tolerance in Prunus mongolica .