GABA and ABA-mediated mitigation of salt stress–induced oxidative damage by modulating secondary metabolites, defense metabolism, and photosynthetic pathways in wheat

Wheat crop vulnerability to varying salinity levels is escalating, significantly endangering global food security. To resolve these challenges, studies on the role of signaling molecules in salt stress could be an imperative tool for sustaining wheat productivity. While the individual roles of γ-aminobutyric acid (GABA) and abscisic acid (ABA) in stress mitigation are well-known, this study demonstrates their synergistic orchestration of the metabolic networks. In this study, GABA and ABA applications stabilize cellular redox homeostasis through antioxidants’ activation and lignification, which has reduced the occurrence of oxidative stress biomarkers, including lipid peroxidation. Further, GABA and ABA modulated the GABA shunt pathway, and adjusted the carbon anabolism (Calvin cycle), catabolism (glycolysis pathway) and amphibolic (tricarboxylic acid [TCA] cycle) events, leading to the accumulation of photosynthesis-end products (starch and sucrose) under salt stress. Hence, the co-application of GABA and ABA has systematically reconfigured sugar and starch metabolism, providing a robust metabolic framework for salt tolerance in wheat. Additionally, nitric oxide (NO) biosynthesis induced upon GABA and ABA co-application has aided in regulating the ionic homeostasis under salt stress. The role of GABA and ABA biosynthesis in salt tolerance has been also substantiated through employing aminooxyacetic acid and fluridone (GABA and ABA biosynthesis inhibitors, respectively). Consequently, these findings establish that the maintenance of an optimal redox state is a prerequisite for sustaining the carbon metabolic flux required for the optimal grain yield under salt stress. By integrating the synergistic GABA-ABA signaling pathways with the carbon metabolic network, this study provides a specific physiological and molecular blueprint for developing "salt-smart" wheat cultivars through targeting the potential plant pathways to balance source-sink partitioning under salt stress.