COMBINED STRESS INDUCED GABA-MEDIATED STRESS SIGNALING IN BEAN PLANTS

Among stress metabolites, gamma aminobutyric acid (GABA) is an important non-proteinogenic amino acid, since its accumulation has been reported in response to various stress factors. However, the response of GABA metabolism in combined stress such as drought and salt is not well known. In this study, bean plants (Phaseolus vulgaris L.) were exposed to individual or combined salinity and PEG-induced osmotic stresses. Antioxidant enzymes activities and glutamate decarboxylase (GDH) activity as well as GABA and malondialdehyde (MDA) contents were analyzed. Among antioxidant enzymes ascorbate peroxidase and catalase activities were increased by individual salt and PEG-induced osmotic stress. GABA content was enhanced by salt, PEG and combined stresses. GDH activity was found parallel to GABA content. MDA content was increased by individual or combined stresses. According to our results individual and combined stress enhanced GABA content in bean plant. Moreover, there could be a strong relationship between GABA and antioxidant defense mechanism in order to cope with deleterious effects of individual or combined ionic and osmotic stresses.