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Handbook of Arsenic Toxicology
2015, Pages: 627–674

Biochemical and Molecular Basis of Arsenic Toxicity and Tolerance in Microbes and Plants

Sarita Pandey, Rashmi Rai, Lal Chand Rai

Molecular Biology Section, Laboratory of Algal Biology, Centre of Advanced Study in Botany, Banaras Hindu University, Varanasi, India.

Abstract

Arsenic is a ubiquitous toxic metalloid abundant in Earth’s crust. It is of major concern with respect to its increased accumulation in soils, in the food chain, or in drinking water. This chapter will focus on recent progress on the mechanisms of its uptake, toxicity, and detoxification in microbes and in planta. Due to widespread occurrence in nature, both microbes and plants have evolved a wide range of tolerance and detoxification mechanisms such as reduced uptake, immobilization, chelation, reduction/oxidation, methylation, and efflux. Among microbes, the ars operon is a well-characterized genetic system for arsenic detoxification. The mechanisms proposed for metal detoxification and hyperaccumulation within the plant involve chelation of the metal cation by ligands and binding with thiol groups or sequestration of metals away from sites or metabolism in the cytoplasm, notably into the vacuole or cell wall. Finally, this chapter will also shed light on hyperaccumulators and mechanisms of hyperaccumulation.

Keywords: Ars; Aox; Arr; biomethylation; dissimilatory arsenate reductase.
 
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