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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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Dose-response of arsenate (As(V)) reduction in Arabidopsis thaliana wild-type and AtACR2 mutants.As speciation in roots (A), shoots (B) and the ratio of shoot to root As concentration (C). Plants were exposed to 5–100 µM As(V) for 24 h.
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pone-0042408-g003: Dose-response of arsenate (As(V)) reduction in Arabidopsis thaliana wild-type and AtACR2 mutants.As speciation in roots (A), shoots (B) and the ratio of shoot to root As concentration (C). Plants were exposed to 5–100 µM As(V) for 24 h.

Mentions: To investigate if arsenate reduction is affected by the dose of arsenate exposure, three concentrations of arsenate were used, representing low (5 µM), medium (25 µM) and high (100 µM) doses of arsenate exposure [18]. After exposure for 24 h, most of the As accumulated in the roots and shoots was in the form of As(III) (Figure 3A, B). The percentage of As(III) in the roots decreased slightly from 94% to 86% with increasing concentration of arsenate exposure, whereas the percentage in the shoots increased slightly from 92% at 5 µM arsenate to 98% at both the 25 and 100 µM arsenate treatments. Regardless of the level of arsenate exposure, the As(III) percentage was similar between WT and the acr2 mutants. The ratio of shoot to root As concentrations was also similar between WT and the mutants (Figure 3C). Larger ratios were obtained at 100 µM arsenate than the other two arsenate treatments.


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)

Dose-response of arsenate (As(V)) reduction in Arabidopsis thaliana wild-type and AtACR2 mutants.As speciation in roots (A), shoots (B) and the ratio of shoot to root As concentration (C). Plants were exposed to 5–100 µM As(V) for 24 h.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0042408-g003: Dose-response of arsenate (As(V)) reduction in Arabidopsis thaliana wild-type and AtACR2 mutants.As speciation in roots (A), shoots (B) and the ratio of shoot to root As concentration (C). Plants were exposed to 5–100 µM As(V) for 24 h.
Mentions: To investigate if arsenate reduction is affected by the dose of arsenate exposure, three concentrations of arsenate were used, representing low (5 µM), medium (25 µM) and high (100 µM) doses of arsenate exposure [18]. After exposure for 24 h, most of the As accumulated in the roots and shoots was in the form of As(III) (Figure 3A, B). The percentage of As(III) in the roots decreased slightly from 94% to 86% with increasing concentration of arsenate exposure, whereas the percentage in the shoots increased slightly from 92% at 5 µM arsenate to 98% at both the 25 and 100 µM arsenate treatments. Regardless of the level of arsenate exposure, the As(III) percentage was similar between WT and the acr2 mutants. The ratio of shoot to root As concentrations was also similar between WT and the mutants (Figure 3C). Larger ratios were obtained at 100 µM arsenate than the other two arsenate treatments.

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