A novel strategy for arsenic phytoremediation

项目概要： 这个补充项目的主要目标是表征砷酸还原酶，ACR 2，作为一种多功能酶 因为它在砷耐受性、转运和限制粮食作物中积累方面的作用。在有氧条件下，植物 通过磷酸盐转运蛋白吸收土壤中的砷（AsV），然后在根中被电化学还原 通过内源性砷酸盐还原酶ACR 2或其同系物HAC 1的活性转化为亚砷酸盐（AsIII）。As III是 从根部挤出或强烈结合谷胱甘肽（GSH）和植物螯合素（PC），这导致诱捕最多 就像地下的根。以前，为了提高As向地上部组织的转运， 本研究利用RNA干扰技术（RNAi）敲减拟南芥AtACR 2基因的表达。RNAi品系 转移10- 16倍以上的芽和保留较少的作为根相比，野生型植物。因此，我们认为， 砷还原酶在植物体内砷的转运和积累过程中起着重要作用。与结果相反， AtACR 2的RNAi敲低，AtACR 2在拟南芥中的过表达提供了对AsV的强耐受性， 使地上部组织中砷的积累减少50-75%。然而，这种多功能AtACR 2 基因没有完全表征，并且在调节As耐受性/敏感性和积累中的作用模式也没有 很好理解。拟南芥AtACR 2含有一个典型的砷酸还原酶结构域“HCX 5 R”和一个高度半胱氨酸-天冬氨酸结构域。 丰富的C-末端结构域。经典的“HXC 5 R”和C-末端富含Cys的结构域在最近的研究中缺失。 其特征在于交替的砷酸盐还原酶HAC 1。我们推测“HCX 5 R”结构域将AsV还原为AsIII， 与富含Cys的C末端结构域结合，因此提供AsIII耐受性。n拟议的补充培训 项目，博士生实习生将描述这种AtACR 2基因，以了解其作用和机制 的耐受性和积累，使用突变的方法，通过取代保守的Cys残基的C- 终点站众所周知，水稻在可食用谷物中积累了高水平的As。这个项目的最终目标 补充项目是通过组成型过表达AtACR 2将知识转化为水稻， 耐性和限制砷在籽粒中的积累。所得到的过表达AtACR 2的转基因水稻品系将是 生长在砷污染土壤中，并将在温室条件下分析砷耐受性和积累 条件因此，拟议的项目将导致制定限制水稻中As的策略，以改善人类健康。 这将产生重大的社会影响。这个项目是直接相关的，但不重叠，我们的 R 01（项目编号：1 R 01 E032686 -01）项目“砷植物修复的新策略”。的目的 R 01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， 高生物量的非粮食作物海甘蓝（Crambe abyssinica）。

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.