A Glimpse on Uptake Kinetics and Molecular Responses of Arsenic Tolerance in Rice Plants

With ever-increasing arsenic (As) pollution in agricultural lands due to various and extensive anthropogenic activities, crop plants, rice to be particular, appeal for immediate attention with possible restriction mechanisms. Arsenic toxicity on rice plants also reveals simultaneous tolerance capacity of intracellular molecules that bind to arsenate/arsenite [As(V)/As(III)]. Interchange of As(III) and As(V) depends on the redox status of the rice field environment and that triggers the transportation competition between arsenate [AS(V)] to phosphate (PO43−) and arsenite [AS(III)] to water molecules as well as silica. Phyto-tolerance of As by rice plants is a dependent variable of As transport. Furthermore, studies suggest that inorganic forms of As are more mobile and toxic compared to organoarsenic compounds like monomethylarsonic acid (MMAA) and dimethylarsinic acid (DMAA). In response to As toxicity, various reactive oxygenic species (ROS) develop which in turn are subdued by the stress suppressor enzymes along with some specialized peptide molecules derived from glutathione (GSH), known as phytochelatins (PC). These protein molecules are well known to form PC-As complex that minimizes the toxicity by chelation. In addition, rice plant root cells are also equipped with Si transporter Lsi1 (OsNIP2;1) as well as aquaglyceroporin (AqpS) molecules that involve ATPase complex and effluxes out the As from the cellular matrix, sometimes transforming into volatile form engaging methylation cascade enzymes. Studies also reported, after analyzing rice genome, the presence of As tolerance gene regulating the quantitative trait locus (QTL) of phosphate uptake controller that suppresses As uptake and holds subsequent tolerance capacity in rice plant.