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敲除 ACR2 不影响拟南芥中的砷氧化还原状态:对植物砷解毒和积累的影响。

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

机构信息

Rothamsted Research, Harpenden, Hertfordshire, United Kingdom.

出版信息

PLoS One. 2012;7(8):e42408. doi: 10.1371/journal.pone.0042408. Epub 2012 Aug 6.

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.

摘要

许多植物物种能够有效地将砷酸盐还原为亚砷酸盐,这是解毒砷的重要步骤,通过亚砷酸盐的外排或与巯基化合物的络合来实现。据推测,这种还原是由 ACR2 催化的,ACR2 是酵母砷酸盐还原酶 ScACR2 的植物同源物。报道称,沉默 AtACR2 会导致拟南芥 shoot 中砷的超积累。然而,目前还没有关于体内砷形态的信息。在这里,我们研究了 AtACR2 敲除或过表达对砷形态、根中亚砷酸盐的外排和 shoot 中砷积累的影响。T-DNA 插入系、过表达系和野生型(WT)植物分别暴露于不同浓度的砷酸盐不同时间,并使用 HPLC-ICP-MS 测定植物中的砷形态和亚砷酸盐的外排。不同系之间的砷形态没有显著差异,根和 shoot 中的总可提取砷中,亚砷酸盐均占>90%。在 6 小时暴露期间,亚砷酸盐向外部介质的外排平均占摄取的砷酸盐的 77%,但 WT 和突变体或过表达系之间没有显著差异。AtACR2 敲除或过表达对 shoot 中砷的积累也没有影响。此外,在暴露于砷酸盐后,缺失 ScACR2 的酵母(酿酒酵母)菌株表现出与 WT 相似的砷形态,亚砷酸盐-巯基复合物是主要的物种。我们的结果表明,植物和酵母中存在多种砷酸盐还原途径。

https://cdn.ncbi.nlm.nih.gov/pmc/blobs/5833/3412857/609dc778e022/pone.0042408.g001.jpg

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