The effects of Cd on lipid peroxidation, hydrogen peroxide content and antioxidant enzyme activities in Cd-sensitive mutant rice seedlings

Abstract

Cadmium-sensitive rice (Oryza sativa L. subsp. Japonica 'Zhonghua11') mutants were obtained using an Agrobacterium tumefaciens-based gene delivery system. Significant phenotypic differences were observed between a Cd-sensitive mutant (ST) and wild type (WT) rice seedlings. Results indicated that Cd accumulation in the leaves of the mutant was twice that of the wild type after 10 d of 0.5 mM Cd2+ treatment. Furthermore, a rapid Cd-induced H 2O2 increase was observed in the mutant leaves, which induced abnormally early activity in antioxidant enzymes such as superoxide dismutase (SOD). However, the mutant leaves showed lower catalase (CAT) activity. By contrast, guaiacol peroxidase (G-POD) activities were higher in the mutant than in the wild type roots. Together with the Cd toxicity-induced decline of early responsive enzymatic activities in vivo, especially CAT, the inability of mutants to scavenge accumulated H2O2 resulted in higher lipid peroxide levels. H2O2 might also strengthen the expression of G-POD as a signaling molecule. Results suggest that G-POD activity can be a potential biomarker reflecting Cd sensitivity in rice seedlings.