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Journal ArticleDOI

Arsenic uptake and metabolism in plants.

01 Mar 2009-New Phytologist (Wiley/Blackwell (10.1111))-Vol. 181, Iss: 4, pp 777-794
TL;DR: Hyperaccumulation appears to involve enhanced arsenate uptake, decreased arsenite-thiol complexation and arsenite efflux to the external medium, greatly enhanced xylem translocation of arsenite, and vacuolar sequestration of arsenites in fronds.
Abstract: Arsenic (As) is an element that is nonessential for and toxic to plants. Arsenic contamination in the environment occurs in many regions, and, depending on environmental factors, its accumulation in food crops may pose a health risk to humans.Recent progress in understanding the mechanisms of As uptake and metabolism in plants is reviewed here. Arsenate is taken up by phosphate transporters. A number of the aquaporin nodulin26-like intrinsic proteins (NIPs) are able to transport arsenite,the predominant form of As in reducing environments. In rice (Oryza sativa), arsenite uptake shares the highly efficient silicon (Si) pathway of entry to root cells and efflux towards the xylem. In root cells arsenate is rapidly reduced to arsenite, which is effluxed to the external medium, complexed by thiol peptides or translocated to shoots. One type of arsenate reductase has been identified, but its in planta functions remain to be investigated. Some fern species in the Pteridaceae family are able to hyperaccumulate As in above-ground tissues. Hyperaccumulation appears to involve enhanced arsenate uptake, decreased arsenite-thiol complexation and arsenite efflux to the external medium, greatly enhanced xylem translocation of arsenite, and vacuolar sequestration of arsenite in fronds. Current knowledge gaps and future research directions are also identified.
Citations
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Journal ArticleDOI
TL;DR: An overview of literature discussing the phytoremediation capacity of hyperaccumulators to clean up soils contaminated with heavy metals and the possibility of using these plants in phytomining is presented.

1,509 citations


Cites background from "Arsenic uptake and metabolism in pl..."

  • ...Storage of As as inorganic arsenite in vacuoles is a key mechnism found in fronds of hyperaccumulator ferns, although the ransport system located at the tonoplast has not been identified et [87]....

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  • ...Thus a high expression of such proteins might conceivably account for the arsenite transfer from root cell cytoplasm to xylem vessels in As hyperaccumulators [87]....

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Journal ArticleDOI
TL;DR: A range of mitigation methods, from agronomic measures and plant breeding to genetic modification, may be employed to reduce As uptake by food crops.
Abstract: Arsenic (As) is an environmental and food chain contaminant. Excessive accumulation of As, particularly inorganic arsenic (As(i)), in rice (Oryza sativa) poses a potential health risk to populations with high rice consumption. Rice is efficient at As accumulation owing to flooded paddy cultivation that leads to arsenite mobilization, and the inadvertent yet efficient uptake of arsenite through the silicon transport pathway. Iron, phosphorus, sulfur, and silicon interact strongly with As during its route from soil to plants. Plants take up arsenate through the phosphate transporters, and arsenite and undissociated methylated As species through the nodulin 26-like intrinsic (NIP) aquaporin channels. Arsenate is readily reduced to arsenite in planta, which is detoxified by complexation with thiol-rich peptides such as phytochelatins and/or vacuolar sequestration. A range of mitigation methods, from agronomic measures and plant breeding to genetic modification, may be employed to reduce As uptake by food crops.

1,025 citations

Journal ArticleDOI
TL;DR: Proteins mediating the uptake of arsenic and cadmium have been identified, and the speciation and biotransformations of arsenic are now understood, and factors controlling the efficiency of root-to-shoot translocation and the partitioning of toxic elements through the rice node have also been identified.
Abstract: Arsenic, cadmium, lead, and mercury are toxic elements that are almost ubiquitously present at low levels in the environment because of anthropogenic influences. Dietary intake of plant-derived food represents a major fraction of potentially health-threatening human exposure, especially to arsenic and cadmium. In the interest of better food safety, it is important to reduce toxic element accumulation in crops. A molecular understanding of the pathways responsible for this accumulation can enable the development of crop varieties with strongly reduced concentrations of toxic elements in their edible parts. Such understanding is rapidly progressing for arsenic and cadmium but is in its infancy for lead and mercury. Basic discoveries have been made in Arabidopsis, rice, and other models, and most advances in crops have been made in rice. Proteins mediating the uptake of arsenic and cadmium have been identified, and the speciation and biotransformations of arsenic are now understood. Factors controlling the efficiency of root-to-shoot translocation and the partitioning of toxic elements through the rice node have also been identified.

745 citations


Cites background from "Arsenic uptake and metabolism in pl..."

  • ...Finally, because aquaglyceroporins mediate facilitated diffusion and not active transport, Lsi1 can mediate efflux of As(III) as well (Figure 2), a process that has been observed in several plant species (146)....

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  • ...This difference is reflected in our article, which emphasizes the substantial progress made since several excellent reviews discussed the detoxification and accumulation of As and Cd by plants (81, 129, 146, 148)....

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  • ...As(III) is the dominant As species in the xylem of most plants analyzed to date (129, 146)....

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Journal ArticleDOI
TL;DR: Recent progress in understanding the mechanisms of As and Cd uptake and detoxification is presented, including the elucidation of why rice takes up so much arsenic from soil and of mechanisms of AS andCd hypertolerance.

703 citations


Cites background from "Arsenic uptake and metabolism in pl..."

  • ...As(V) accounts for a variable but considerable fraction of the total xylem As of nonhyperaccumulators although As(III) is always more abundant than As(V) [54,8 ]....

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  • ...vittata, xylem As is almost exclusively present as As(III), and As(III) efflux from roots into the rhizosphere is negligible, compared to non-As-hyperaccumulators (reviewed in [8 ]) (Figure 1)....

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  • ...adapted from [8 ]....

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  • ...As(V) is potentially toxic because it can substitute for phosphate in phosphorylation reactions, including ATP synthesis [8 ]....

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  • ...vittata, hardly any As(III) efflux was observed (Figure 1) (reviewed in [8 ])....

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Journal ArticleDOI
TL;DR: The two forms of inorganic arsenic, arsenate (AsV) and arsenite (AsIII), are easily taken up by the cells of the plant root Once in the cell, AsV can be readily converted to AsIII, the more toxic of the two forms AsV and AsIII both disrupt plant metabolism, but through distinct mechanisms as mentioned in this paper.
Abstract: The two forms of inorganic arsenic, arsenate (AsV) and arsenite (AsIII), are easily taken up by the cells of the plant root Once in the cell, AsV can be readily converted to AsIII, the more toxic of the two forms AsV and AsIII both disrupt plant metabolism, but through distinct mechanisms AsV is a chemical analog of phosphate that can disrupt at least some phosphate-dependent aspects of metabolism AsV can be translocated across cellular membranes by phosphate transport proteins, leading to imbalances in phosphate supply It can compete with phosphate during phosphorylation reactions, leading to the formation of AsV adducts that are often unstable and short-lived As an example, the formation and rapid autohydrolysis of AsV-ADP sets in place a futile cycle that uncouples photophosphorylation and oxidative phosphorylation, decreasing the ability of cells to produce ATP and carry out normal metabolism AsIII is a dithiol reactive compound that binds to and potentially inactivates enzymes containing closely spaced cysteine residues or dithiol co-factors Arsenic exposure generally induces the production of reactive oxygen species that can lead to the production of antioxidant metabolites and numerous enzymes involved in antioxidant defense Oxidative carbon metabolism, amino acid and protein relationships, and nitrogen and sulfur assimilation pathways are also impacted by As exposure Readjustment of several metabolic pathways, such as glutathione production, has been shown to lead to increased arsenic tolerance in plants Species- and cultivar-dependent variation in arsenic sensitivity and the remodeling of metabolite pools that occurs in response to As exposure gives hope that additional metabolic pathways associated with As tolerance will be identified

645 citations


Cites background or methods from "Arsenic uptake and metabolism in pl..."

  • ...It can compete with phosphate during phosphorylation reactions, leading to the formation of AsV adducts that are often unstable and short-lived....

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  • ...In the fronds, AsIII is sequestered as free AsIII in the vacuole (Lombi et al., 2002; Pickering et al., 2006), where it accumulates to extremely high levels (Zhao et al., 2009)....

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  • ...The rapid rate of uptake and translocation to the frond and a higher antioxidant capacity to maintain lower ROS levels (Cao et al., 2004; Zhao et al., 2009), perhaps coupled with relatively rapid dilution in the bulk of the aerial tissues, together seem to provide the hyperaccumulators with…...

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  • ...Of the small portion of As that is translocated, no more than 40% would be expected to be in the form of AsV, based on As speciation determinations in a number of species (Zhao et al., 2009)....

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  • ...Conversely, Pi fertilization can protect plants, including the hyperaccumulator P. vittata, from AsV toxicity (Tu and Ma, 2003)....

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References
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Journal ArticleDOI
01 Feb 2001-Nature
TL;DR: A hardy, versatile, fast-growing plant that helps to remove arsenic from contaminated soils.
Abstract: A hardy, versatile, fast-growing plant helps to remove arsenic from contaminated soils.

1,704 citations


"Arsenic uptake and metabolism in pl..." refers background in this paper

  • ...Since the first discovery of As hyperaccumulation in P. vittata (Ma et al., 2001), a total of 12 As hyperaccumulators have been identified, all of them belonging to the Pteridaceae family of ferns and most being found within the Pteris genus (Supporting Information Table S1)....

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  • ...vittata (Ma et al., 2001), a total of 12 As hyperaccumulators have been identified, all of them belonging to the Pteridaceae family of ferns and most being found within the Pteris genus (Supporting Information Table S1)....

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  • ...Meanwhile, the discovery of As-hyperaccumulating fern species (Ma et al., 2001) has attracted much attention and further research focusing on understanding the mechanisms behind this extraordinary phenomenon and evaluation of the phytoremediation potential of various As hyperaccumulators....

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Journal ArticleDOI
TL;DR: Genetically manipulating the Si uptake capacity of the root might help plants to accumulate more Si and, hence, improve their ability to overcome biotic and abiotic stresses.

1,471 citations


"Arsenic uptake and metabolism in pl..." refers background in this paper

  • ...In addition, Si application can increase rice yield by alleviating biotic and abiotic stresses (Ma & Yamaji, 2006)....

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Journal ArticleDOI
21 Jun 2002-Science
TL;DR: Nordstrom et al. as mentioned in this paper argue that human health risks from arsenic in ground water can be minimized by incorporating hydrogeochemical knowledge into water management decisions and by more careful monitoring for arsenic in geologically high-risk areas.
Abstract: Numerous aquifers worldwide carry soluble arsenic at concentrations greater than the World Health Organization--and U.S. Environmental Protection Agency--recommended drinking water standard of 10 mg per liter. Sources include both natural (black shales, young sediments with low flushing rates, gold mineralization, and geothermal environments) and anthropogenic (mining activities, livestock feed additives, pesticides, and arsenic trioxide wastes and stockpiles). Increased solubility and mobility of arsenic is promoted by high pH (>8.5), competing oxyanions, and reducing conditions. In this Policy Forum, Nordstrom argues that human health risks from arsenic in ground water can be minimized by incorporating hydrogeochemical knowledge into water management decisions and by more careful monitoring for arsenic in geologically high-risk areas.

1,469 citations

Journal ArticleDOI
30 Mar 2006-Nature
TL;DR: The identification of a silicon transporter provides both an insight into the silicon uptake system in plants, and a new strategy for producing crops with high resistance to multiple stresses by genetic modification of the root's silicon uptake capacity.
Abstract: Silicon is beneficial to plant growth and helps plants to overcome abiotic and biotic stresses by preventing lodging (falling over) and increasing resistance to pests and diseases, as well as other stresses. Silicon is essential for high and sustainable production of rice, but the molecular mechanism responsible for the uptake of silicon is unknown. Here we describe the Low silicon rice 1 (Lsi1) gene, which controls silicon accumulation in rice, a typical silicon-accumulating plant. This gene belongs to the aquaporin family and is constitutively expressed in the roots. Lsi1 is localized on the plasma membrane of the distal side of both exodermis and endodermis cells, where casparian strips are located. Suppression of Lsi1 expression resulted in reduced silicon uptake. Furthermore, expression of Lsi1 in Xenopus oocytes showed transport activity for silicon only. The identification of a silicon transporter provides both an insight into the silicon uptake system in plants, and a new strategy for producing crops with high resistance to multiple stresses by genetic modification of the root's silicon uptake capacity.

1,398 citations


"Arsenic uptake and metabolism in pl..." refers background in this paper

  • ...They are sometimes called aquaglyceroporins (Wallace et al., 2006), although some of the NIPs (e.g. OsNIP2;1) have little permeability to glycerol (Ma et al., 2006; Mitani et al., 2008), and there is no direct evidence for a physiological role in plants of glycerol transport through NIPs (Bienert…...

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  • ...Recently, Ma et al. (2008) have identified OsNIP2;1, also named Lsi1 because of its primary function as a silicon (Si) transporter (Ma et al., 2006), as a major pathway for the entry of arsenite into rice roots....

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  • ...Lsi1 is strongly expressed in rice roots and its expression is further enhanced in plants not supplied with Si (Ma et al., 2006)....

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  • ...(2008) have identified OsNIP2;1, also named Lsi1 because of its primary function as a silicon (Si) transporter (Ma et al., 2006), as a major pathway for the entry of arsenite into rice roots....

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  • ...Therefore, the pathway of Si transport from the external medium to the stele involves the influx of silicic acid mediated by the aquaporin channel Lsi1 (Ma et al., 2006), and the efflux of Si towards the stele mediated by Lsi2 (Ma et al....

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Journal ArticleDOI
TL;DR: It is reported that two different types of transporters mediate transport of arsenite, the predominant form of arsenic in paddy soil, from the external medium to the xylem, which explains why rice is efficient in arsenic accumulation.
Abstract: Arsenic poisoning affects millions of people worldwide. Human arsenic intake from rice consumption can be substantial because rice is particularly efficient in assimilating arsenic from paddy soils, although the mechanism has not been elucidated. Here we report that two different types of transporters mediate transport of arsenite, the predominant form of arsenic in paddy soil, from the external medium to the xylem. Transporters belonging to the NIP subfamily of aquaporins in rice are permeable to arsenite but not to arsenate. Mutation in OsNIP2;1 (Lsi1, a silicon influx transporter) significantly decreases arsenite uptake. Furthermore, in the rice mutants defective in the silicon efflux transporter Lsi2, arsenite transport to the xylem and accumulation in shoots and grain decreased greatly. Mutation in Lsi2 had a much greater impact on arsenic accumulation in shoots and grain in field-grown rice than Lsi1. Arsenite transport in rice roots therefore shares the same highly efficient pathway as silicon, which explains why rice is efficient in arsenic accumulation. Our results provide insight into the uptake mechanism of arsenite in rice and strategies for reducing arsenic accumulation in grain for enhanced food safety.

1,181 citations


"Arsenic uptake and metabolism in pl..." refers background or result in this paper

  • ...Recently, Ma et al. (2008) have identified OsNIP2;1, also named Lsi1 because of its primary function as a silicon (Si) transporter (Ma et al., 2006), as a major pathway for the entry of arsenite into rice roots....

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  • ...Ma et al. (2008) showed that, in addition to Lsi1, three other NIP channel proteins in rice, OsNIP1;1, OsNIP2;2 (also named Lsi6) and OsNIP3;1, are also able to mediate arsenite influx into X. laevis oocytes expressing these genes....

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  • ...While Lsi1 transports arsenite into rice root cells, a different transporter, Lsi2, has been found to mediate arsenite efflux in the direction of xylem (Ma et al., 2008) (Fig....

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  • ...NIPs have low to no water permeability and the ability to transport multiple uncharged solutes of varying sizes including glycerol, urea, ammonia, boric acid and silicic acid (Wallace et al., 2006), as well as arsenite (Bienert et al., 2008b; Isayenkov & Maathuis, 2008; Ma et al., 2008)....

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  • ...Recently, evidence that some plant aquaporin channels can mediate arsenite influx has been obtained from three independent studies (Bienert et al., 2008b; Isayenkov & Maathuis, 2008; Ma et al., 2008)....

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