title: Selenium ameliorates arsenic induced oxidative stress through modulation of antioxidant enzymes and thiols in rice (Oryza sativa L.).
abstract: Arsenic (As) contamination of rice is a major problem for South-East Asia. In the present study, the effect of selenium (Se) on rice (Oryza sativa L.) plants exposed to As was studied in hydroponic culture. Arsenic accumulation, plant growth, thiolic ligands and antioxidative enzyme activities were assayed after single (As and Se) and simultaneous supplementations (As + Se). The results indicated that the presence of Se (25 µM) decreased As accumulation by threefold in roots and twofold in shoots as compared to single As (25 µM) exposed plants. Arsenic induced oxidative stress in roots and shoots was significantly ameliorated by Se supplementation. The observed positive response was found associated with the increased activities of ascorbate peroxidase (APX; EC 1.11.1.11), catalase (CAT; EC 1.11.1.6) and glutathione peroxidase (GPx; EC 1.11.1.9) and induced levels of non-protein thiols (NPTs), glutathione (GSH) and phytochelatins (PCs) in As + Se exposed plants as compared to single As treatment. Selenium supplementation modulated the thiol metabolism enzymes viz., γ-glutamylcysteine synthetase (γ-ECS; EC 6.3.2.2), glutathione-S-transferase (GST; EC 2.5.1.18) and phytochelatin synthase (PCS; EC 2.3.2.15). Gene expression analysis of several metalloid responsive genes (LOX, SOD and MATE) showed upregulation during As stress, however, significant downregulation during As + Se exposure as compared to single As treatment. Gene expressions of enzymes of antioxidant and GSH and PC biosynthetic systems, such as APX, CAT, GPx, γ-ECS and PCS were found to be significantly positively correlated with their enzyme activities. The findings suggested that Se supplementation could be an effective strategy to reduce As accumulation and toxicity in rice plants.
authors.affiliation: Plant Ecology and Environmental Science Division, C.S.I.R.-National Botanical, Research Institute, Rana Pratap Marg, Lucknow, 226 001, India.
authors.forename: Amit
authors.initials: A
authors.lastname: Kumar
authors.forename: Rana Pratap
authors.initials: RP
authors.lastname: Singh
authors.forename: Pradyumna Kumar
authors.initials: PK
authors.lastname: Singh
authors.forename: Surabhi
authors.initials: S
authors.lastname: Awasthi
authors.forename: Debasis
authors.initials: D
authors.lastname: Chakrabarty
authors.forename: Prabodh Kumar
authors.initials: PK
authors.lastname: Trivedi
authors.forename: Rudra Deo
authors.initials: RD
authors.lastname: Tripathi
mesh_terms: D000975:Antioxidants / Q000378:metabolism; D001151:Arsenic / Q000633:toxicity*; D060387:Ascorbate Peroxidases / Q000378:metabolism; D002374:Catalase / Q000378:metabolism; D004151:Dipeptides / Q000378:metabolism; D005506:Food Contamination; D018506:Gene Expression Regulation, Plant; D005978:Glutathione / Q000378:metabolism; D005979:Glutathione Peroxidase / Q000378:metabolism; D005982:Glutathione Transferase / Q000378:metabolism; D015227:Lipid Peroxidation; D012275:Oryza / Q000187:drug effects* / Q000201:enzymology; D018384:Oxidative Stress / Q000187:drug effects*; D054811:Phytochelatins / Q000378:metabolism; D012643:Selenium / Q000494:pharmacology*; D013438:Sulfhydryl Compounds / Q000378:metabolism*
chemical_list: D000975:Antioxidants; D004151:Dipeptides; D013438:Sulfhydryl Compounds; D054811:Phytochelatins; D060387:Ascorbate Peroxidases; D002374:Catalase; D005979:Glutathione Peroxidase; D005982:Glutathione Transferase; D005978:Glutathione; D012643:Selenium; C017341:gamma-glutamylcysteine; D001151:Arsenic