A novel strategy for arsenic phytoremediation

项目总结： 这个补充项目的主要目标是将砷酸还原酶ACR2表征为一种多功能酶 因为它在粮食作物的耐砷、转运和限制积累方面发挥了作用。在好氧条件下，植物 通过磷转运体从土壤中吸收砷(Asv)，然后在根中电化学还原Asv 通过内源性砷酸还原酶ACR2或其同系物HAC1的活性转化为亚砷酸盐(AsIII)。AS III是 从根部挤出或与谷胱甘肽(GSH)和植物螯合素(PC)强烈结合，这会导致大多数 就像在地下的根。以前，为了植物修复，加强As向地上部组织的转移 目的：利用RNA干扰技术(RNAi)下调AtACR2在拟南芥中的表达。RNAi系 与野生型植物相比，在地上部的转运量增加了10到16倍，而在根中的转移量减少了。因此， 砷酸还原酶在植物体内砷的运输和积累中起着关键作用。与…的结果相反 AtACR2的RNAi敲除后，AtACR2在拟南芥中的过表达提供了对ASV和 可使地上部组织中砷的积累减少50-75%。然而，这款多功能AtACR2 基因的特性还不完全，调节砷耐受性/敏感性和积累的作用方式也不是 很好理解。拟南芥AtACR2含有一个规范的砷酸还原酶结构域“HCX5R”和一个高度的半胱氨酸- 富含C-末端结构域。典型的“HXC5R”和C-末端富含Cys的结构域在最近的 表征交替砷酸还原酶HAC1。我们推测，“HCX5R”结构域将ASV还原为AsIII，从而 与富含半胱氨酸的C-末端结构域结合，从而提供对AsIII的耐受性。N拟议的补充培训 项目中，博士生实习生将对AtACR2基因进行表征，以了解其作用和机制 利用突变方法通过取代C-中保守的Cys-残基来耐受和积累As 终点站。众所周知，水稻在可食用谷物中积累了高水平的砷。这样做的最终目的是 补充项目是通过结构性地过度表达AtACR2来将知识转化为水稻以增加产量 耐砷和限制砷在籽粒中的积累。由此产生的过量表达AtACR2的转基因水稻株系将是 在As污染的土壤中生长，并将在温室下分析As的耐受性和积累 条件。因此，拟议的项目将导致制定限制大米中砷含量的策略，以改善人类 因此，它将产生重大的社会影响。该项目与我们的项目直接相关，但没有重叠 R01(项目ID：1R01E032686-01)项目“植物修复砷的新策略”。该计划的目标是 R01项目是开发一种基于遗传学的植物修复策略，用于砷的吸收、转运、解毒、 并向快速生长、高生物量的非粮食作物Crambe abyssinica转化。

Project Summary: The main objective of this supplemental project is to characterize arsenate reductase, ACR2, as a multifunctional enzyme for its role in arsenic tolerance, translocation, and limiting accumulation in food crops. Under aerobic conditions, plants absorb arsenate (AsV) from soil through phosphate transporters, and then AsV in roots is electrochemically reduced to arsenite (AsIII) by the activity of endogenous arsenate reductase, ACR2, or its homologs HAC1. AsIII is either extruded out of the roots or strongly binds to glutathione (GSH) and phytochelatins (PCs), which causes trapping most As belowground in the roots. Previously, to enhance the translocation of As to shoot tissues for phytoremediation purpose, we knocked down the AtACR2 expression using RNA interference (RNAi) in Arabidopsis. RNAi lines translocated 10- to 16-fold more As in shoots and retained less As in roots compared to wild-type plants. Therefore, arsenate reductases play a critical role in the translocation and accumulation of As in plants. Contrary to the results of RNAi knockdown of AtACR2, the overexpression of AtACR2 in Arabidopsis provided strong tolerance to AsV and caused a 50-75% reduction of As accumulation in aboveground shoot tissues. However, this multifunctional AtACR2 gene is not fully characterized and the mode of action in modulating the As tolerance/sensitivity and accumulation is not well understood. Arabidopsis AtACR2 contains a canonical arsenate reductase domain “HCX5R” and a highly cysteine- rich C-terminal domain. The canonical “HXC5R” and C-terminal Cys-rich domains are missing in the recently characterized alternate arsenate reductase HAC1. We speculate that “HCX5R” domain reduces AsV to AsIII, which binds to the Cys-rich C-terminal domain and hence provides AsIII tolerance. n the proposed supplemental training project, the PhD student trainee will characterize this AtACR2 gene to understand its role and mechanism of As tolerance and accumulation using a mutational approach by replacing the conserved Cys-residues in the C- terminus. Rice (Oryza sativa) is well known to accumulate high levels of As in edible grains. The ultimate goal of this supplemental project is to translate the knowledge into rice via overexpressing AtACR2 constitutively for increase tolerance and limiting As accumulation in the grains. The resulting transgenic rice lines overexpressing AtACR2 will be grown in As contaminated soils and will be analyzed for As tolerance and accumulation under greenhouse conditions. Therefore, the proposed project will lead to developing strategies for limiting As in rice to improve human health and thus will have a significant societal impact. This project is directly related, but not overlapped, to our R01 (Project ID: 1R01E032686-01) project “A novel strategy for arsenic phytoremediation”. The objective of the R01 project is to develop a genetics-based phytoremediation strategy for arsenic uptake, translocation, detoxification, and hyperaccumulation into the fast-growing, high biomass, non-food crop Crambe abyssinica.