The role of melatonin in reinforcement of antioxidant system of rice plant ( Oryza sativa L.) under arsenite toxicity?
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ORIGINAL ARTICLE
The role of melatonin in reinforcement of antioxidant system of rice plant (Oryza sativa L.) under arsenite toxicity? Mehri Nazarian1 • Faezeh Ghanati1
Received: 12 August 2018 / Accepted: 27 May 2020 Indian Society for Plant Physiology 2020
Abstract Arsenic (As) is a toxic metalloid, which enters into the human food chain mainly through rice. One imminent toxic effect of As is oxidative stress. Melatonin is potentially an antioxidant compound. The aim of the present study was to evaluate the efficiency of melatonin to decrease arsenite (AsIII) toxicity in rice (Oryza sativa L.). Twenty one day old rice plants were treated with or without 25 lM AsIII, 0.25 lM melatonin, and a combination of both, for 48 h in hydroponic culture. Arsenite toxicity was manifested as reduced chlorophyll, soluble sugars and protein contents, and decreased growth of the plants (48%, 29.1%, 23.6% and 87.5% of the controls, respectively). In addition, AsIII increased the content of H2O2, the activity of catalase (CAT), the contents of total non-protein thiols (TNP-SH), glutathione (GSH), and phytochelatine (PCs) (2.5%, 926%, 191.5%, 12.3% and 361.4 of their corresponding controls, respectively). In the presence of AsIII, however, melatonin ameliorated oxidative stress on roots by reducing As content, increasing the contents of TNPSH, GSH, and PCs which led to decrease of H2O2 and malondialdehyde (MDA) content. The results also indicated that melatonin facilitated the transportation of As from roots to shoots, resulting in turn in higher accumulation of As in shoots and suppression of antioxidant system. Further studies are needed in order to clarify the mechanism(s) by which melatonin accelerated transportation of As from root to shoot of rice plant.
& Faezeh Ghanati [email protected] 1
Department of Plant Biology, Faculty of Biological Science, Tarbiat Modares University (TMU), POB 14115-154, Tehran, Iran
Keywords Antioxidant system Arsenite Melatonin Oxidative stress Rice
Introduction Arsenic (As) is a metalloid, which has deleterious effects for all forms of life including plants (Sharma 2012). As is exist in organic (monomethylarsonic acid and dimethylarsinic acid), and inorganic (arsenite and arsenate) forms (Tu et al. 2002). Application of arsenical pesticides, herbicides, and combustion of fossil fuels, mining, smelting of ores in addition to natural weathering of rocks and volcanic emissions are of main sources of As contamination (Smedley and Kinniburgh 2002). The use of As-contaminated groundwater and surface waters for irrigation of agricultural fields increases the concentration of As in crop plants (Flora 2011). Rice is the major crop in areas where severe arsenic contaminations have occurred (Ahsan et al. 2010). About 50% of the world population consumes rice as their staple food; therefore, excess accumulation of Asian rice is a serious threat to human health (Tripathi et al. 2012). Arsenite is taken up via the nodulin 26-like intrinsic proteins (NIPs) a subfamily of aquaporins (AQP) (Ma
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