title: Arsenic stress in rice: redox consequences and regulation by iron.
abstract: Arsenic (As) contamination is a serious hazard to human health and agriculture. It has emerged as an important threat for rice cultivation mainly in South Asian countries. In this study, we investigated the effect of iron (Fe) supplementation on arsenic (As(V)) induced oxidative stress responses in rice (Oryza sativa L.). Rice seedlings treated with As(V) for 24 and 48 h in presence or absence of 2.5 mM Fe after which the root and shoot tissues were harvested for analysis. The results indicate significant (p ≤ 0.05) reduction in root and shoot length/dry biomass. Supplementation of Fe showed improved growth responses under stress as compared to As(V) alone. The scanning electron microscopy (SEM) analysis of roots under As(V) treatment for 48 h showed major alterations in root structure and integrity, although no noticeable changes were observed in Fe - supplemented seedlings. Significantly high (p ≤ 0.05) accumulation of As(V) was observed in root and shoot after 24 and 48 h of stress. However, under Fe - supplementation As accumulation in root and shoot were considerably low after 24 and 48 h of As(V) treatment. The hydrogen peroxide (H2O2) and malondialdehyde (MDA) content in both root and shoot increased significantly (p ≤ 0.05) after 24 and 48 h of As(V) treatment. In Fe - supplemented seedlings, the levels of H2O2 and MDA were considerably low as compared to As(V) alone. Ascorbate (AsA) and glutathione (GSH) levels also increased significantly (p ≤ 0.05) under As(V) stress as compared to control and Fe-supplemented seedlings. Activities of catalase (CAT) and superoxide dismutase (SOD) were significantly (p ≤ 0.05) high after 24 and 48 h of As(V) treatment as compared to Fe-supplemented seedlings. The gene expression analysis revealed up-regulation of metallothionein (MT1, MT2) and nodulin 26-like intrinsic protein (NIP2;1) genes after 5d of As treatment, while their expressions were repressed under Fe-supplementation. Our results indicate that Fe regulates oxidative stress and promotes growth under As stress.
authors.affiliation: Plant Molecular Biotechnology Laboratory, Department of Life Science and Bioinformatics, Assam University, Silchar 788 011, India.
authors.forename: Shwetosmita
authors.initials: S
authors.lastname: Nath
authors.affiliation: Plant Molecular Biotechnology Laboratory, Department of Life Science and Bioinformatics, Assam University, Silchar 788 011, India.
authors.forename: Piyalee
authors.initials: P
authors.lastname: Panda
authors.affiliation: Department of Biotechnology, Indian Institute of Technology, Guwahati 781 039, Assam, India.
authors.forename: Sagarika
authors.initials: S
authors.lastname: Mishra
authors.affiliation: Department of Biotechnology, Indian Institute of Technology, Guwahati 781 039, Assam, India.
authors.forename: Mohitosh
authors.initials: M
authors.lastname: Dey
authors.affiliation: Central Instrumentation Laboratory, Assam University, Silchar 788 011, India. Electronic address: shuvasish@gmail.com.
authors.forename: Shuvasish
authors.initials: S
authors.lastname: Choudhury
authors.affiliation: Department of Biotechnology, Indian Institute of Technology, Guwahati 781 039, Assam, India.
authors.forename: Lingaraj
authors.initials: L
authors.lastname: Sahoo
authors.affiliation: Plant Molecular Biotechnology Laboratory, Department of Life Science and Bioinformatics, Assam University, Silchar 788 011, India.
authors.forename: Sanjib Kumar
authors.initials: SK
authors.lastname: Panda
mesh_terms: D001151:Arsenic / Q000633:toxicity*; D007501:Iron / Q000378:metabolism*; D012275:Oryza / Q000187:drug effects* / Q000378:metabolism*; D010084:Oxidation-Reduction / Q000187:drug effects; D018384:Oxidative Stress / Q000187:drug effects
chemical_list: D007501:Iron; D001151:Arsenic
keywords: Antioxidants; Arsenic; Gene expression; Iron; Oryza sativa; Oxidative stress