Limits...
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.

Show MeSH

Related in: MedlinePlus

Arsenate (As(V)) uptake and arsenite (As(III)) efflux in wild-type and AtACR2 mutants of Arabidopsis thaliana.Plants were exposed to 5 µM As(V) in a phosphate-free nutrient solution for 6 h.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC3412857&req=5

pone-0042408-g004: Arsenate (As(V)) uptake and arsenite (As(III)) efflux in wild-type and AtACR2 mutants of Arabidopsis thaliana.Plants were exposed to 5 µM As(V) in a phosphate-free nutrient solution for 6 h.

Mentions: Previous studies [12], [14] have shown that plant roots extrude As(III) to the external solution following uptake of As(V). If As(V) reduction is impaired in the acr2 mutants, it may be expected that As(III) efflux will also decrease. As(V) uptake and As(III) efflux were quantified by monitoring the changes in As speciation in the nutrient solution after 6 h exposure to As(V) at an initial concentration of 5 µM (without phosphate). The exposure time was chosen as it was in the middle of the linear uptake phase (see Figure 2). Both As(V) uptake and As(III) efflux were similar between WT and the acr2 mutants with As(III) efflux accounting for 77–79% of the As(V) uptake in all three lines (Figure 4).


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)

Arsenate (As(V)) uptake and arsenite (As(III)) efflux in wild-type and AtACR2 mutants of Arabidopsis thaliana.Plants were exposed to 5 µM As(V) in a phosphate-free nutrient solution for 6 h.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0042408-g004: Arsenate (As(V)) uptake and arsenite (As(III)) efflux in wild-type and AtACR2 mutants of Arabidopsis thaliana.Plants were exposed to 5 µM As(V) in a phosphate-free nutrient solution for 6 h.
Mentions: Previous studies [12], [14] have shown that plant roots extrude As(III) to the external solution following uptake of As(V). If As(V) reduction is impaired in the acr2 mutants, it may be expected that As(III) efflux will also decrease. As(V) uptake and As(III) efflux were quantified by monitoring the changes in As speciation in the nutrient solution after 6 h exposure to As(V) at an initial concentration of 5 µM (without phosphate). The exposure time was chosen as it was in the middle of the linear uptake phase (see Figure 2). Both As(V) uptake and As(III) efflux were similar between WT and the acr2 mutants with As(III) efflux accounting for 77–79% of the As(V) uptake in all three lines (Figure 4).

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