Soil Science Department, Rothamsted Research, Harpenden, Hertfordshire AL5 2JQ, UK.
Research Institute for Bioresources, Okayama University, Chuo 2-20-1, Kurashiki 710-0046, Japan.
New Phytol. 2009 Mar;181(4):777-794. doi: 10.1111/j.1469-8137.2008.02716.x.
Arsenic (As) is an element that is nonessential for and toxic to plants. Arsenic contamination in the environment occurs in many regions, and, depending on environmental factors, its accumulation in food crops may pose a health risk to humans.Recent progress in understanding the mechanisms of As uptake and metabolism in plants is reviewed here. Arsenate is taken up by phosphate transporters. A number of the aquaporin nodulin26-like intrinsic proteins (NIPs) are able to transport arsenite,the predominant form of As in reducing environments. In rice (Oryza sativa), arsenite uptake shares the highly efficient silicon (Si) pathway of entry to root cells and efflux towards the xylem. In root cells arsenate is rapidly reduced to arsenite, which is effluxed to the external medium, complexed by thiol peptides or translocated to shoots. One type of arsenate reductase has been identified, but its in planta functions remain to be investigated. Some fern species in the Pteridaceae family are able to hyperaccumulate As in above-ground tissues. Hyperaccumulation appears to involve enhanced arsenate uptake, decreased arsenite-thiol complexation and arsenite efflux to the external medium, greatly enhanced xylem translocation of arsenite, and vacuolar sequestration of arsenite in fronds. Current knowledge gaps and future research directions are also identified.
砷（As）是一种对植物既非必需又有毒的元素。环境中的砷污染存在于许多地区，并且根据环境因素的不同，其在粮食作物中的积累可能会对人类健康构成威胁。本文综述了近年来人们对植物砷吸收和代谢机制的认识进展。砷酸盐由磷酸盐转运蛋白摄取。许多水通道蛋白类nodulin26 内在蛋白（NIPs）能够转运亚砷酸盐，这是还原环境中砷的主要存在形式。在水稻（Oryza sativa）中，亚砷酸盐的摄取与硅（Si）进入根细胞的高效途径共享，并向木质部流出。在根细胞中，砷酸盐迅速被还原为亚砷酸盐，然后被运出到外部介质，与硫醇肽结合或转运到地上部分。已经鉴定出一种类型的砷酸盐还原酶，但它在植物体内的功能仍有待研究。凤尾蕨科的一些蕨类植物能够在地上部分超积累砷。超积累似乎涉及增强的砷酸盐摄取、减少的亚砷酸盐-硫醇复合物形成和亚砷酸盐向外部介质的流出、极大增强的木质部砷酸盐转运以及砷酸盐在蕨叶中的液泡隔离。本文还确定了当前的知识空白和未来的研究方向。
