Heme oxygenase-1 is involved in ascorbic acid-induced alleviation of cadmium toxicity in root tissues of Medicago sativa
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Heme oxygenase-1 is involved in ascorbic acid-induced alleviation of cadmium toxicity in root tissues of Medicago sativa Qijiang Jin & Kaikai Zhu & Yanjie Xie & Wenbiao Shen
Received: 8 July 2012 / Accepted: 2 September 2012 / Published online: 21 September 2012 # Springer Science+Business Media B.V. 2012
Abstract Aims This study explored molecular mechanism of ascorbic acid (AsA)-mediated enhancement of plant tolerance against cadmium (Cd) stress. Methods Complex pharmacological, histochemical and molecular approaches were applied to analyse the effect of AsA on the alleviation of Cd stress and corresponding signalling pathway. Results Cd stress brought about severe oxidative damage and remarkable decrease in AsA content in alfalfa (Medicago sativa) seedling roots. Exogenous AsA not only increased AsA content in vivo, and strengthened the up-regulation of alfalfa heme oxygenase-1 (HO-1) transcript and HO activity triggered by Cd, but also significantly decreased Cd accumulation and oxidative damage, which was confirmed by the histochemical analysis. The responses of AsA were further impaired by the potent inhibitor of HO-1, zinc protoporphyrin IX (ZnPP), which were blocked further when 50 % saturation of carbon monoxide (CO) aqueous solution (in particular) or bilirubin (BR), two catalytic by-products of HO-1, was added, respectively. Molecular evidence illustrated that AsA-triggered the up-regulation of antioxidant enzyme genes, especially Mn-SOD and POD, were sensitive to ZnPP and reversed by CO. Responsible Editor: Juan Barcelo. Q. Jin : K. Zhu : Y. Xie : W. Shen (*) College of Life Sciences, Co. Laboratory of Nanjing Agricultural University and Carl Zeiss Far East, Jiangsu Province, Nanjing Agricultural University, Nanjing 210095, People,s Republic of China e-mail: [email protected]
Conclusions In short, above results suggested that cytoprotective roles triggered by AsA might be, at least partially, through HO-1-dependent fashion by the induction of antioxidant system and lowering Cd accumulation. Keywords Ascorbic acid . Cadmium toxicity . Heme oxygenase-1 . Medicago sativa . Oxidative damage . Root tissues Abbreviations APX Ascorbate peroxidase AsA Ascorbic acid BR Bilirubin BV Biliverdin IXα CO Carbon monoxide EF-2 Elongation factor 2 HO Heme oxygenase HO-1 Heme oxygenase-1 Mn-SOD Manganese superoxide dismutase POD Guaiacol peroxidase TBARS Thiobarbituric acid reactive substances ZnPP Zinc protoporphyrin IX
Introduction Cadmium (Cd) is a highly toxic and persistent environmental poison for plants and animals (Sanità and Gabbrielli 1999). Besides the severe seedling growth inhibition and Cd accumulation, one of the indirectly primary responses of plants to Cd exposure is oxidative
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damage, which led to lipid peroxidation of the plasma membrane (Xiang and Oliver 1998; Rodríguez-Serrano et al. 2006; De Michele et al. 2009). It was well established that the excess formation of reactive oxygen species (ROS) in plant cells, including superoxide anion radical (O2-), hydrogen peroxide (H2
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