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Knocking out ACR2 does not affect arsenic redox status in Arabidopsis thaliana: implications for as detoxification and accumulation in plants.

Liu W, Schat H, Bliek M, Chen Y, McGrath SP, George G, Salt DE, Zhao FJ - PLoS ONE (2012)

Bottom Line: There were no significant differences in As speciation between different lines, with arsenite accounting for >90% of the total extractable As in both roots and shoots.Arsenite efflux to the external medium represented on average 77% of the arsenate taken up during 6 h exposure, but there were no significant differences between WT and mutants or overexpression lines.Our results suggest the existence of multiple pathways of arsenate reduction in plants and yeast.

View Article: PubMed Central - PubMed

Affiliation: Rothamsted Research, Harpenden, Hertfordshire, United Kingdom.

ABSTRACT
Many plant species are able to reduce arsenate to arsenite efficiently, which is an important step allowing detoxification of As through either efflux of arsenite or complexation with thiol compounds. It has been suggested that this reduction is catalyzed by ACR2, a plant homologue of the yeast arsenate reductase ScACR2. Silencing of AtACR2 was reported to result in As hyperaccumulation in the shoots of Arabidopsis thaliana. However, no information of the in vivo As speciation has been reported. Here, we investigated the effect of AtACR2 knockout or overexpression on As speciation, arsenite efflux from roots and As accumulation in shoots. T-DNA insertion lines, overexpression lines and wild-type (WT) plants were exposed to different concentrations of arsenate for different periods, and As speciation in plants and arsenite efflux were determined using HPLC-ICP-MS. There were no significant differences in As speciation between different lines, with arsenite accounting for >90% of the total extractable As in both roots and shoots. Arsenite efflux to the external medium represented on average 77% of the arsenate taken up during 6 h exposure, but there were no significant differences between WT and mutants or overexpression lines. Accumulation of As in the shoots was also unaffected by AtACR2 knockout or overexpression. Additionally, after exposure to arsenate, the yeast (Saccharomyces cerevisiae) strain with ScACR2 deleted showed similar As speciation as the WT with arsenite-thiol complexes being the predominant species. Our results suggest the existence of multiple pathways of arsenate reduction in plants and yeast.

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Related in: MedlinePlus

Root elongation as affected by arsenate and phosphate concentrations in wild-type, AtACR2 knockout mutant (acr2-1) and overexpression line (ACR2-OE1).
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pone-0042408-g006: Root elongation as affected by arsenate and phosphate concentrations in wild-type, AtACR2 knockout mutant (acr2-1) and overexpression line (ACR2-OE1).

Mentions: Arsenic tolerance was tested in WT, acr2-1 and ACR2-OE1 lines using a root elongation assay. Significant differences between WT and the knockout mutant or the overexpression line were observed at either a very low (1 µM) or a very high (1000 µM) phosphate concentration, but not at medium phosphate concentrations (10 and 100 µM) (Figure 6). At 1 µM phosphate, the knockout mutant was more sensitive to As than WT, whereas the overexpressing line was more tolerant to As than WT. At 1000 µM phosphate, the knockout mutant became more tolerant to As than WT, whereas the overexpressing line had a level of tolerance similar to that of WT. In contrast to root growth, no clear difference in shoot growth was observed.


Knocking out ACR2 does not affect arsenic redox status in Arabidopsis thaliana: implications for as detoxification and accumulation in plants.

Liu W, Schat H, Bliek M, Chen Y, McGrath SP, George G, Salt DE, Zhao FJ - PLoS ONE (2012)

Root elongation as affected by arsenate and phosphate concentrations in wild-type, AtACR2 knockout mutant (acr2-1) and overexpression line (ACR2-OE1).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3412857&req=5

pone-0042408-g006: Root elongation as affected by arsenate and phosphate concentrations in wild-type, AtACR2 knockout mutant (acr2-1) and overexpression line (ACR2-OE1).
Mentions: Arsenic tolerance was tested in WT, acr2-1 and ACR2-OE1 lines using a root elongation assay. Significant differences between WT and the knockout mutant or the overexpression line were observed at either a very low (1 µM) or a very high (1000 µM) phosphate concentration, but not at medium phosphate concentrations (10 and 100 µM) (Figure 6). At 1 µM phosphate, the knockout mutant was more sensitive to As than WT, whereas the overexpressing line was more tolerant to As than WT. At 1000 µM phosphate, the knockout mutant became more tolerant to As than WT, whereas the overexpressing line had a level of tolerance similar to that of WT. In contrast to root growth, no clear difference in shoot growth was observed.

Bottom Line: There were no significant differences in As speciation between different lines, with arsenite accounting for >90% of the total extractable As in both roots and shoots.Arsenite efflux to the external medium represented on average 77% of the arsenate taken up during 6 h exposure, but there were no significant differences between WT and mutants or overexpression lines.Our results suggest the existence of multiple pathways of arsenate reduction in plants and yeast.

View Article: PubMed Central - PubMed

Affiliation: Rothamsted Research, Harpenden, Hertfordshire, United Kingdom.

ABSTRACT
Many plant species are able to reduce arsenate to arsenite efficiently, which is an important step allowing detoxification of As through either efflux of arsenite or complexation with thiol compounds. It has been suggested that this reduction is catalyzed by ACR2, a plant homologue of the yeast arsenate reductase ScACR2. Silencing of AtACR2 was reported to result in As hyperaccumulation in the shoots of Arabidopsis thaliana. However, no information of the in vivo As speciation has been reported. Here, we investigated the effect of AtACR2 knockout or overexpression on As speciation, arsenite efflux from roots and As accumulation in shoots. T-DNA insertion lines, overexpression lines and wild-type (WT) plants were exposed to different concentrations of arsenate for different periods, and As speciation in plants and arsenite efflux were determined using HPLC-ICP-MS. There were no significant differences in As speciation between different lines, with arsenite accounting for >90% of the total extractable As in both roots and shoots. Arsenite efflux to the external medium represented on average 77% of the arsenate taken up during 6 h exposure, but there were no significant differences between WT and mutants or overexpression lines. Accumulation of As in the shoots was also unaffected by AtACR2 knockout or overexpression. Additionally, after exposure to arsenate, the yeast (Saccharomyces cerevisiae) strain with ScACR2 deleted showed similar As speciation as the WT with arsenite-thiol complexes being the predominant species. Our results suggest the existence of multiple pathways of arsenate reduction in plants and yeast.

Show MeSH
Related in: MedlinePlus