The Regulation of Glutathione S-Transferases by Gibberellic Acid Application in Salt Treated Maize Leaves

Abstract

Plant hormones and antioxidant system changes occur during plants' exposure to stress conditions. Although the interactions of some plant hormones (abscisic acid, salicylic acid, jasmonic acid, nitric oxide, and ethylene) with the glutathione s-transferase (GST) enzyme, which is one of the antioxidant enzymes, have already been reported, the influence of gibberellic acid (GA(3)) on this enzyme under saline conditions has not yet been reported. Plant material for the experiments was obtained from M14G144 cultivar of maize (Zea mays L.) plants grown as a soil culture in growth chambers at 22 & DEG;C, 65-70% moisture, 16-h light/8-h dark conditions, and with full strength Hoagland solution for 8 days under controlled growth conditions. Then, the plants were exposed to salt stress (350 mM NaCl and 100, 300, and 500 ppm GA(3)) simultaneously. In maize leaves, GA(3) treatment alleviated the physiological parameters under salt stress. Specifically, the treatments with 100 and 500 ppm of GA(3) were able to trigger GST enzyme and isoenzyme activities as well as hydrogen sulfide accumulation and anthocyanin content, although the lowest malondialdehyde, hydrogen peroxide, and superoxide radical content were under the treatment of 300 ppm of GA(3). Besides this, GST gene expression levels were found to be upregulated between 1.5 and fourfold higher in all the plants treated with GA(3) at different concentrations in proportion to salt stress. These results first indicated that the reason for the changes in GA(3)-treated plants was the stimulating role of this hormone to maintain GST regulation in maize plants.