Sulfur mediated reduction of arsenic toxicity involves efficient thiol metabolism and the antioxidant defense system in rice

Garima Dixit, Amit Pal Singh, Amit Kumar Kumar, Pradyumna Kumar Singh, Smita Kumar, Sanjay Dwivedi, Prabodh Kumar Trivedi, Vivek Pandey, Gareth John Norton, Om Parkash Dhankher, Rudra Deo Tripathi

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Abstract

Arsenic (As) contamination is a global issue, with South Asia and South East Asia being worst affected. Rice is major crop in these regions and can potentially pose serious health risks due to its known As accumulation potential. Sulfur (S) is an essential macronutrient and a vital element to combat As toxicity. The aim of this study was to investigate the role of S with regards to As toxicity in rice under different S regimes. To achieve this aim, plants were stressed with AsIII and AsV under three different S conditions (low sulfur (0.5 mM), normal sulfur (3.5 mM) and high sulfur (5.0 mM)). High S treatment resulted in increased root As accumulation, likely due to As complexation through enhanced synthesis of thiolic ligands, such as non-protein thiols and phytochelatins, which restricted As translocation to the shoots. Enzymes of S assimilatory pathways and downstream thiolic metabolites were up-regulated with increased S supplementation; however, to maintain optimum concentrations of S, transcript levels of sulfate transporters were down-regulated at high S concentration. Oxidative stress generated due to As was counterbalanced in the high S treatment by reducing hydrogen peroxide concentration and enhancing antioxidant enzyme activities. The high S concentration resulted in reduced transcript levels of Lsi2 (a known transporter of As). This reduction in Lsi2 expression level is a probable reason for low shoot As accumulation, which has potential implications in reducing the risk of As in the food chain.
Original languageEnglish
Pages (from-to)241-251
Number of pages11
JournalJournal of Hazardous Materials
Volume298
Early online date5 Jun 2015
DOIs
Publication statusPublished - 15 Nov 2015

Keywords

  • antioxidant enzymes
  • arsenic
  • rice
  • sulfate and arsenic transporters
  • sulfur
  • thiol metabolism

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    Dixit, G., Singh, A. P., Kumar, A. K., Singh, P. K., Kumar, S., Dwivedi, S., Trivedi, P. K., Pandey, V., Norton, G. J., Dhankher, O. P., & Tripathi, R. D. (2015). Sulfur mediated reduction of arsenic toxicity involves efficient thiol metabolism and the antioxidant defense system in rice. Journal of Hazardous Materials, 298, 241-251. https://doi.org/10.1016/j.jhazmat.2015.06.008