Activity And Subsellular Localization Of Isoforms Of Superoxide Dismutase, Accumulation Of Glycine Betaine And Malondialdehyde In Wheat Genotypes Subjected To Continuous Soil Drought

Drought resistance is provided by multicomponent antioxidant system, causing rearrangements at the physiological, cellular and molecular levels. Experiments with two durum (Triticum durum Desf.) wheat genotypes with contrasting drought tolerance were carried out to study the effect of soil drought on changes in activities and subcellular localization of isoforms of superoxide dismutase, levels of malondoaldehyde, glycine betaine and total protein content. The level of the enzyme activity appeared to depend on the wheat genotypes, duration of drought and stages of the plant growth. Wheat responds to water deficit through accumulation of glycine betaine in leaves. Significant accumulation of MDA occurred in the sensitive variety Gragylchig-2 contrary to the tolerant Barakatli-95 under severe stress conditions. Native polyacrylamide gel electrophoresis (PAGE) revealed the presence of 9 isoforms of superoxide dismutase in wheat leaves during drought. Wheat leaves contain three different types of SODs (Mn-, Fe-, Cu/Zn-SOD) Mn-SOD was found in the mitochondrial fractions, Fe-SOD in the chloroplast fraction and Cu/Zn-SOD is localized in all subcellular fractions. The long-term drought was accompanied by the expression of the levels of these isoforms. Three isoforms of Mn-SOD, one isoform of Fe-SOD and five of Cu/Zn-SOD were observed in wheat leaves using 3mM KCN and 5 mM H2O2 as selective inhibitors. Mn-SOD was established to make the most contribution to increase of SOD activity. It seems that this isoform plays a major role in the scavenging of superoxide radicals during a longterm drought.