Abstract γ-Aminobutyric acid (GABA) is one of the key stress metabolites involved in the functioning of the plant cell signaling network. Ho
Abstract γ-Aminobutyric acid (GABA) is one of the key stress metabolites involved in the functioning of the plant cell signaling network. However, its functional relationships with main signaling molecules, particularly nitric oxide (NO), are not well understood. This study aimed to determine NO’s involvement in GABA’s stress-protective effect on wheat seedlings (Triticum aestivum L., Etana cultivar) under model drought conditions (13% PEG 6000). Priming grains with a 0.5 mM GABA solution or a 0.1 mM solution of the NO donor sodium nitroprusside (SNP) increased germination energy, seed germination, and water content in seedlings under stressful conditions. Additionally, GABA and SNP treatment mitigated the inhibitory effect of drought on the accumulation of root and shoot biomass. Osmotic stress increased NO content in shoots, and priming with GABA and SNP enhanced this effect. Treatment with the nitric oxide scavenger methylene blue (MB, 0.1 mM) eliminated the increase in NO content caused by stress or GABA action. MB also negated the positive effects of GABA on growth processes. Under the action of GABA and SNP, total amylase activity in grains and soluble carbohydrate content in shoots increased under stressful conditions; MB eliminated GABA’s effect on these parameters. Under the model drought, the content of oxidative stress markers (superoxide anion radical, hydrogen peroxide, and malondialdehyde) increased in shoots, but pretreatment of grains with GABA or SNP significantly reduced these effects. Osmotic stress caused an increase in activity of catalase and guaiacol peroxidase in shoots. Preliminary priming with GABA, SNP, and MB did not affect the nature of the changes in activity of these antioxidant enzymes caused by model drought. Meanwhile, superoxide dismutase activity remained unchanged following exposure to the model drought; however, pretreatment seeds with GABA, SNP, and MB increased the enzyme activity. Priming seeds with GABA and SNP increased the total content of phenolic compounds in shoots and preserved the anthocyanin pool under stressful conditions, while MB treatment eliminated these effects. It was concluded that the enhancement of grain germination and seedling growth induced by GABA priming under model drought conditions is largely due to NO-mediated modulation of carbohydrate and secondary compound metabolism.
