Regulation of glutathione S-transferase enzyme activity with salt pre-treatment under heat stress in maize leaves

Abstract

Abstract- The present study was conducted to present the responses of heat-sensitive (Shemal) and heat-tolerant (71MAY69) maize cultivars under heat stress (at 40 °C for 2 hours in 2 days) with pre-salinity treatment (50 mM NaCl) to determine the relation of salicylic acid (SA) and glutathione S-transferase (GST) enzyme activity in those responses. Relative water content (RWC), chlorophyll content (CHL), stomatal conductance (g_s), hydrogen peroxide (H₂O₂), malondialdehyde (MDA) content, GST enzyme and isoenzyme activity and internal SA levels were investigated. While heat treatments resulted in low RWC, CHL g_s and high MDA and H₂O₂ levels in sensitive cultivar, all these values were lower in tolerant cultivar. Compared to single heat stress treatments, heat stress with pre-salinity treatment increased GST enzyme and isozyme activity of both cultivars. Results also indicated that pre-salinity treatment triggered internal SA levels and hydrogen peroxide contents in sensitive leaves according to control groups. Such hydrogen peroxide levels also decreased by increasing total GST and isozyme activities under heat alone, pre-salinity treatment alone. As a result, it could be said that SA is a good signal for the changes of GST enzyme activity under heat stress treatment.