GABA Metabolism and MDA Production in Barley (Hordeum vulgare L.) Seedlings under Salinity and Osmotic Stresses

This study examined the gamma-aminobutyric acid (GABA) shunt pathway in response to salt and osmotic stresses in three barley (Hordeum vulgare L.) genotypes (Acsad176, Athroh, and Rum) in terms of seed germination, seedlings growth, oxidative damage through malondialdehyde (MDA) accumulation as an indicator for reactive oxygen species (ROS), GABA metabolite accumulation, chlorophyll level, total proteins, total carbohydrates and the expression of glutamate decarboxylase gene (GAD) analysis.

GABA is a secondary metabolite that modulates nitrogen metabolism, protects against oxidative damage, and cytosolic pH in response to various abiotic and biotic stress in plants.

The effects of salt and osmotic stresses imposed by different concentrations of mannitol, sorbitol, and NaCl on the three barley genotypes were studied. Seed germination, seedling length, fresh weight, and dry mass were recorded. The physiological and biochemical responses as per GABA and MDA accumulation, total chlorophyll, proteins and carbohydrates, and the level of GAD expression were also characterized and determined.

Mannitol, sorbitol, and NaCl treatments decreased seed germination and seedling growth for the three barely genotypes used in this study. MDA concentration was increased in seedlings of all genotypes with increasing NaCl, mannitol, and sorbitol concentrations. Acsad 176 showed high GABA accumulation under NaCl treatment. Mannitol treatment significantly increased GABA accumulation in the Rum genotype. All salt and osmotic treatments decreased chlorophyll a and b and carbohydrate content and significantly increased GAD transcription in all barley genotypes. Salt and osmotic stresses affected the total protein content in all genotypes.

Acsad 176 genotype may adapt to NaCl stress by accumulating carbohydrates more than Athroh and Rum. GABA shunt is a crucial signaling and metabolic pathway facilitating barley's adaptation to salt and osmotic stress. In soil with high salt and osmotic contents, the Acsad 176 genotype is the recommended genotype for cultivation.