Abstract

Salt stress is one of the major problems in agricultural fields. Currently, more than 20% of irrigated agricultural lands are affected by salinity. High concentrations of sodium affects plant growth by competing with the uptake of important ions like potassium (K⁺), and posing osmotic stress. Some plant species developed mechanisms such as modifying cellular metabolism to minimize effects of high salt concentrations. Gamma-aminobutyric acid (GABA) accumulation during salt stress is one of the results of modifications in cellular metabolism. However, whether this response is specific or not has not been shown before. Here, it was hypothesized that GABA accumulation is needed to counter the effects of salt stress. For that, GABA-depleted Arabidopsis gad1/2 mutant was investigated for altered response under salt stress. Indeed, the double mutant was oversensitive to 150 mM NaCl treatment. Furthermore, the mutant was oversensitive to osmotic stress; since the double mutant showed reduced shoot water content after 300 mM mannitol treatment. Comparison of metabolites between salt-treated wild type and gad1/2 mutant showed that GABA shunt plays a central role in modulating the carbon and nitrogen metabolism. Taken together, the findings show that GABA accumulation under salt stress conditions plays an important role to overcome the high salt concentration damage.

Key words: Salt stress, osmotic stress, GABA-shunt, tricarboxylic acid (TCA) cycle intermediates, potassium, transporters.