Exogenous Hematin Alleviates Mercury-induced Oxidative Damage in the Roots of Medicago sativa  

作　　者：Yi Han Wei Xuan Tian Yu Wen-Bing Fang Tian-Ling Lou Yin Gao Xiao-Yue Chen XiaoXiao Wen-Biao Shen 

机构地区：[1]College of Life Sciences, Laboratory of Nanjing Agricultural University and Carl Zeiss Far East, Nanjing Agricultural University, Nanjing 210095, China

出　　处：《Journal of Integrative Plant Biology》2007年第12期1703-1713,共11页植物学报（英文版）

基　　金：Supported by the 111 Project of China(B07030);the National Natural Science Foundation of China(30671248);Student Research Training (SRT) Project(0606A03,KFJJ200501 and JD200502) of Nanjing Agricultural University

摘　　要：In the present study, we evaluated the protective effect of exogenous heme oxygenase-1 （HO-1 EC 1.14.99.3） inducer hematin against mercury-induced oxidative damage in the roots of Alfalfa （Medicago sativa L.）. Plants exposed to mercury （HgCl2） exhibited a significant increase of lipid peroxidation, as well as inhibition of root elongation. However, hematin （50 μM） supplementation to HgCl2 （100 μmol/L） treated plants effectively reduced the lipid peroxidation and partially increased the root elongation. These responses were mimicked by the application of aqueous solution of carbon monoxide （CO） with 50% saturation. Also, treatment with hematin could result in the potent induction of HO-1 transcript in the root tissues, as detected 12h following treatment. Moreover, the activation of anti-oxidant enzyme, including glutathione reductase, monodehydroascorbate reductase and superoxide dismutase activities, and the decrease of lipoxygenase activity, were induced by hematin at 12h or 24h, which was further confirmed by histochemical staining for the detection of lipid peroxidation and loss of membrane integrity. Whereas, ascorbate peroxidase and guaiacol peroxidase isozyme activities or their transcripts were reduced, respectively, indicating that hydrogen peroxide might act as a signal to mediate Hg- tolerance at the beginning of treatment. The ameliorating effects of hematin were specific, since the CO scavenger hemoglobin differentially reversed the above actions. Taken together, our results suggested that hematin exhibits a vital role in protecting the plant against Hg-induced oxidative damage.In the present study, we evaluated the protective effect of exogenous heme oxygenase-1 （HO-1 EC 1.14.99.3） inducer hematin against mercury-induced oxidative damage in the roots of Alfalfa （Medicago sativa L.）. Plants exposed to mercury （HgCl2） exhibited a significant increase of lipid peroxidation, as well as inhibition of root elongation. However, hematin （50 μM） supplementation to HgCl2 （100 μmol/L） treated plants effectively reduced the lipid peroxidation and partially increased the root elongation. These responses were mimicked by the application of aqueous solution of carbon monoxide （CO） with 50% saturation. Also, treatment with hematin could result in the potent induction of HO-1 transcript in the root tissues, as detected 12h following treatment. Moreover, the activation of anti-oxidant enzyme, including glutathione reductase, monodehydroascorbate reductase and superoxide dismutase activities, and the decrease of lipoxygenase activity, were induced by hematin at 12h or 24h, which was further confirmed by histochemical staining for the detection of lipid peroxidation and loss of membrane integrity. Whereas, ascorbate peroxidase and guaiacol peroxidase isozyme activities or their transcripts were reduced, respectively, indicating that hydrogen peroxide might act as a signal to mediate Hg- tolerance at the beginning of treatment. The ameliorating effects of hematin were specific, since the CO scavenger hemoglobin differentially reversed the above actions. Taken together, our results suggested that hematin exhibits a vital role in protecting the plant against Hg-induced oxidative damage.

关 键 词：carbon monoxide HEMATIN Medicago sativa mercury toxicity oxidative stress. 

分 类 号：Q946[生物学—植物学]