Studies On The Alternation Of AsA-GSH Cycle In Cadmium Sensitive/Insensitive Rice Mutant To Cadmium Stress

The Cd-sensitive/insensitive mutant rice(cadB-1/cadL-5)were obtained using the rice(Oryza sativa L.subsp.Japonica,cv.Zhonghua 11)mutants which derived from gene transformation mediated via Agrobacterium tumefaciens.We analyzed the different H₂O₂ content,AsA-GSH cycle and antioxidant enzymes activities responses to 0.1 mmol·L^-1,0.25 mmol·L^-1,0.5 mmol·L^-1and 0.75 mmol·L^-1Cd²⁺stress in cadB-1,cadL-5 and wild type(WT)rice seedlings.The results showed as follows:1.The research showed that wild type and the mutant(cadB-1/cadL-5)exhibited obvious phenotypic difference when exposed to 0.75 mmol·L^-1Cd²⁺stress.Cd²⁺ accumulated in the mutant cadB-1 were higher levels in roots,stems and leaves than the WT,while Cd²⁺accumulated in the mutant cadL-5 were lower levels in roots, stems,leaves and seeds than the WT.2.Cd²⁺could increase the H₂O₂ content of rice leaf and root in cadB-1,cadL-5 and WT.With increasing Cd²⁺concentrations,H₂O₂ accumulation was higher.The mutant cadB-1 was accumulating more H₂O₂ in leaves and roots than WT,while the mutant cadL-5 was accumulating less H₂O₂ in leaves and roots than WT.3.With increasing Cd²⁺concentration,the efficiency of AsA-GSH cycle and antioxidant enzymes activities decreased.The antioxidant system could not eliminate excess reactive oxygen species,thus malondialdehyde content increased,and integrality of cell membrane was destroyed.With increasing Cd²⁺concentration,the ratio of GSH/GSSG,AsA/DHA,NADPH/NADP⁺ were all decreasing with different levels in mutant cadB-1,cadL-5 and WT,mutant cadB-1 decreased most,mutant cadL-5 decreased lest,WT was between cadB-1 and cadL-5.In the whole,under Cd²⁺ stress,the AsA-GSH cycle and antioxidative enzymes were lest inhibited in mutant cadL-5,thus the mutant cadL-5 could eliminate excess reactive oxygen species, which is advantageous to the reduction of Cd²⁺injury,the AsA-GSH cycle and antioxidative enzymes were most inhibited in mutant cadB-1,which experience most serious oxidant stress.The AsA-GSH cycle and antioxidative enzymes in WT decreased were between mutant cadB-1 and cadL-5.The results showed the efficiency of AsA-GSH cycle and the diversification of antioxidative enzymes activities are the key physiological foundation for Oryza sativa L.to withstand Cd²⁺toxicity.