LANTHANUM IONS INTERVENED IN ENZYMATIC PRODUCTION AND ELIMINATION OF REACTIVE OXYGEN SPECIES IN LEAVES OF RICE SEEDLINGS UNDER CADMIUM STRESS

Rare earth elements at proper concentrations were observed to alleviate heavy metal stress. However, the potential mechanisms of alleviation are not clear. Thus, the present study focused on the mechanisms of lanthanum (La) ions on the generation and elimination of reactive oxygen species (ROS) production in leaves of rice seedlings hydroponically cultivated in 30 mu M cadmium chloride (CdCl2) for 2 d. Results showed that the decline of superoxide (O-2 center dot(-)) or hydrogen peroxide (H2O2) was attributed not only to the decreased expressions of nicotinamide adenine dinucleotide phosphate oxidases-related gene, protein synthesis, and isozymes, but also to the decrease of xanthine oxidase, diamine oxidase, and guaiacol peroxidases isozymes and activities. Genes and isozymes related to superoxide dismutase, catalase, and ascorbate peroxidase were also differentially upregulated to control ROS accumulation when proper concentrations of La were combined with 30 mu M Cd. Based on the results, one may conclude that La at proper concentrations not only limited the generation of O-2 center dot(-) and H2O2 from the enzymatic sources but also promoted the elimination of O-2 center dot(-) and H2O2 via the upregulating expressions of antioxidant enzyme-related genes and activities in the rice seedling's leaves under Cd stress. (C) 2014 SETAC