Oxidative Stress and Dna Damage in Broad Bean (vicia Faba

6300 words in the text 6325 This ET&C Paper in Press manuscript is in its original unedited form and has not been copyedited or formatted for final production. This manuscript is fully citable. ©2008 Society of Environmental Toxicology and Chemistry (SETAC). This ET&C Paper in Press manuscript is in its original unedited form and has not been copyedited or formatted for final production. This manuscript is fully citable. ©2008 Society of Environmental Toxicology and Chemistry (SETAC). 3 *To whom correspondence may be addressed ([email protected]). Abstract–Thallium is a metal of great toxicological concern as it is highly toxic to all living organisms through yet poorly understood mechanisms. Since thallium is accumulated by important crops, the present study aimed to analyze the biological effects induced by bioaccumulation of thallium in broad bean (Vicia faba L.) as well as plant's antioxidative defense mechanisms usually activated by heavy metals. Thallium toxicity has been related to production of reactive oxygen species in leaves and roots of broad bean seedlings following short-term (72 h) exposure to thallium (I) acetate (0, 0.5, 1, 5 and 10 mg/L) by evaluating DNA damage and oxidative stress parameters as well as antioxidative response. Possible antagonistic effect of potassium was tested by combined treatment – 5 mg/L of thallium (Tl+) and 10 mg/L of potassium (K+) acetate. Accumulation of Tl+ in roots was 50 to 250 times higher than in broad bean shoots and accompanied by increase in dry weight and proline. Despite responsive antioxidative defense (increased activities of superoxide dismutase, ascorbate peroxidase and pyrogallol peroxidase), Tl+ caused oxidative damage to lipids and proteins as evaluated by malondialdehyde and carbonyl group levels and induced DNA strand breaks. Combined treatment caused no oxidative alternations to lipids and proteins though it induced DNA damage. The difference in Tl-induced genotoxicity following both acellular and cellular exposure implies indirect DNA damage. Results obtained indicate that oxidative stress is involved in the mechanism of thallium toxicity and that the tolerance of broad bean to thallium is achieved, at least in part, through the increased activity of antioxidant enzymes. This ET&C Paper in Press manuscript is in its original unedited form and has not been copyedited or formatted for final production. This manuscript is fully citable. ©2008 Society of Environmental Toxicology and Chemistry (SETAC).