Evaluation of arsenic trioxide genotoxicity in wheat seedlings using oxidative system and RAPD assays

Arsenic is a metalloid that is toxic to living organisms. It is known that high concentration of arsenic causes toxic damage to cells and tissues of plants. While the toxic effect of arsenic is known, limited efforts have been made to study its genotoxic effect on the crops. In the present study, effects of arsenic trioxide (As2O3) on seed germination, root length, reactive oxygen species (ROS), lipid peroxidation (malondialdehyde (MDA)), and activities of antioxidant enzymes, as well as DNA in wheat seedlings were investigated. Seedlings were exposed to different (10 to 40 mg/L) As2O3 concentrations for 7 days. Seed germination and root elongation decreased with increase of As2O3 concentration. The values of hydrogen peroxide (H2O2), superoxide anion (O-2 (center dot-)), and MDA contents significantly increased by As2O3 concentrations. The highest values for H2O2, O-2 (center dot-), and MDA were obtained in 40 mg/L treated wheat seedling. A significant increase of peroxidase (POX) and catalase (CAT) activity in seedlings were observed with increased concentration of As2O3, then decreased when reaching a value of 40 mg/L, whereas the activities of superoxide dismutase (SOD) were gradually enhanced with increasing As2O3 concentration. Alterations of DNA in wheat seedlings were detected using randomly amplified polymorphic DNA (RAPD) technique. The changes occurring in RAPD profiles of seedlings following As2O3 treatment included loss of normal bands and appearance of new bands in comparison to that of control seedlings. The results of our study showed that As2O3 induced DNA damage in a dose-dependent meaner, and the root cells of wheat studied showed a defense against As2O3-induced oxidative stress by enhancing their antioxidant activities.