Integrated physiological and multi-omics analyses reveal genotype-specific GABA responses associated with salt tolerance in Brassica rapa.

Soil salinity restricts the yield of winter Brassica rapa, yet it remains unclear whether gamma-aminobutyric acid (GABA) alleviates salt stress through universal physiological responses or genotype-specific regulatory patterns. To resolve this question, salt-tolerant KY and salt-sensitive Qin were subjected to four treatments: blank control (CK), sole GABA supplementation(G), single salt stress(S), and combined salt stress plus GABA(S+G). Multiple indicators covering seedling growth status, membrane impairment, reactive oxygen species buildup, antioxidant performance, Na+/K+ balance and ion transportation were measured. Transcriptome profiling, DIA proteomic detection and qRT-PCR confirmation were also conducted for multi-omics exploration. Exogenous GABA relieved salt-triggered growth suppression, oxidative injury and ion disorder across both genotypes, with KY displaying stronger physiological and molecular responses associated with salt stress adaptation. Under NaCl stress conditions, KY possessed stronger antioxidant buffering potential, steadier Na+/K+ homeostasis, as well as enhanced native capacities to take in K+ and expel Na+. Omics data identified a KY-enriched regulatory module associated with phenylpropanoid and flavonoid metabolism, where BrPAL2, BrCSE, BrGSTU25, BrGASA7 and BrCYP74A were identified as candidate genes potentially associated with GABA-responsive salt tolerance. Collectively, GABA exerts non-universal salt-mitigating effects; its protective performance depends on genotype-matched coordination of physiological defense, ionic equilibrium and stress-responsive molecular pathways. These findings provide insights into genotype-dependent GABA responses and may contribute to future evaluation of GABA application and saline-adapted germplasm improvement in B. rapa.