Effect of thiourea on proteins, catalase, guaiacol-peroxidase and protease activities in wheat leaves under H2O2 induced oxidative stress . Ajmad Hameed1*, Liala Jafri2 and Muneer A. Sheikh2

The effect of different thiourea (TU) concentrations (10 and 20 mM) on antioxidants, protease activity and protein content with and without H2O2 (50 mM) induced stress was investigated in wheat leaves. A gradual decrease in protein content with a peak at 72 hours was observed in stressed as well as control leaves. This gradual decrease in leaf protein content at different time intervals was completely prevented by 20 mM TU treatment. Leaf protease activity was increased due to oxidative stress by H2O2 while it decreased after 20 mM TU treatment under stressed and non-stressed condition. In general, catalase (CAT) activity increased under oxidative stress and after both thiourea treatments. However, at 72 hours, CAT activity reduced along with simultaneous increase in peroxidase activity under H2O2 induced stress. Actually, stress induced reduction in CAT activity at 72 hours was compensated with peroxidase. Oxidative stress and TU treatments generally raised the peroxidase activity. TU treatment followed by oxidative stress condition also increased the leaf peroxidase activity irrespective of applied concentration. Again, H2‌O2 and TU treatment induced reduction in CAT activity at 96 hours was compensated with a prompt increase in peroxidase activity. Collectively, H2O2 treatment increased the antioxidant and protease activities. Moreover, thiourea treatments prevented the protein loss (20mM TU), decreased the protease activity and enhanced the CAT and peroxidase activities which resulted in protective effects. Dose dependent effects of TU treatments were observed mostly.