TITLE	Copper-induced stress and antioxidative responses in roots of Brassica juncea L.
AUTHOR	Song-Hua Wang Department of Biochemistry and Molecular Biology, College of Life Science, Nanjing Agricultural University, Nanjing, 210095, P.R. China Zhi-Min Yang Department of Biochemistry and Molecular Biology, College of Life Science, Nanjing Agricultural University, Nanjing, 210095, P.R. China Hong Yang Department of Biochemistry and Molecular Biology, College of Life Science, Nanjing Agricultural University, Nanjing, 210095, P.R. China Bo Lu Department of Biochemistry and Molecular Biology, College of Life Science, Nanjing Agricultural University, Nanjing, 210095, P.R. China Shao-Qong Li Department of Biochemistry and Molecular Biology, College of Life Science, Nanjing Agricultural University, Nanjing, 210095, P.R. China Ya-Ping Lu Department of Biochemistry and Molecular Biology, College of Life Science, Nanjing Agricultural University, Nanjing, 210095, P.R. China
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ABSTRACT	Copper induced antioxidative reactions in the roots of Brassica juncea L. were investigated in both time-and concentration-dependent manners. The rapid uptake of Cu was observed immediately after the start of treatment. Application of Cu at 8 µM caused 50 percent reduction in biomass of Cu-treated roots as compared with control. Cu-induced root growth inhibition paralleled the level of root oxidative damage. Treatment with Cu at 8 µM induced a twofold increase in H2O2 content during the first 4 d, but it declined to the basal level thereafter. We also observed a twofold increase in superoxide dismutase activities with 8 µM Cu during the first 2 d. The stimulation lasted for 4 d and then gradually declined. Activities of both ascorbate peroxidase and guaiacol peroxidase in roots were found to be low during the first 4 d after seedling exposure to 8 µM Cu, but significantly increased after that, suggesting that increased enzyme activities would be responsible for the removal of H2O2. Catalase activities were always suppressed under Cu stress. Treatment of seedlings with 8 µM Cu induced general decreases in both reduced ascorbate and dehydroascorbate. The reduced glutathione content decreased at early stages of Cu treatment. However, it was restored to the level of controls thereafter. In contrast, the oxidized glutathione contents showed a progressive increase during the time of Cu treatment. The total non-protein thiol content was shown to increase during the first several days, but it declined at later stages.
KEYWORD	Antioxidative enzymes; Brassica juncea L.; Copper; Hydrogen peroxide; Non-protein thiols;
ARTICLE INFO	Botanical Bulletin of Academia Sinica, Volume 45 Number 3 July 2004, page 203-212, 10 pages
PUBLISHER	Institute of Plant and Microbial Biology, Academia Sinica, Taipei, Taiwan, Republic of China