Department of Integrative Bioscience and Biotechnology, University of Zurich Cooperative Laboratory, World Class University Program, Pohang University of Science and Technology, Pohang 790-784, Korea.
Proc Natl Acad Sci U S A. 2010 Dec 7;107(49):21187-92. doi: 10.1073/pnas.1013964107. Epub 2010 Nov 15.
Arsenic is an extremely toxic metalloid causing serious health problems. In Southeast Asia, aquifers providing drinking and agricultural water for tens of millions of people are contaminated with arsenic. To reduce nutritional arsenic intake through the consumption of contaminated plants, identification of the mechanisms for arsenic accumulation and detoxification in plants is a prerequisite. Phytochelatins (PCs) are glutathione-derived peptides that chelate heavy metals and metalloids such as arsenic, thereby functioning as the first step in their detoxification. Plant vacuoles act as final detoxification stores for heavy metals and arsenic. The essential PC-metal(loid) transporters that sequester toxic metal(loid)s in plant vacuoles have long been sought but remain unidentified in plants. Here we show that in the absence of two ABCC-type transporters, AtABCC1 and AtABCC2, Arabidopsis thaliana is extremely sensitive to arsenic and arsenic-based herbicides. Heterologous expression of these ABCC transporters in phytochelatin-producing Saccharomyces cerevisiae enhanced arsenic tolerance and accumulation. Furthermore, membrane vesicles isolated from these yeasts exhibited a pronounced arsenite [As(III)]-PC(2) transport activity. Vacuoles isolated from atabcc1 atabcc2 double knockout plants exhibited a very low residual As(III)-PC(2) transport activity, and interestingly, less PC was produced in mutant plants when exposed to arsenic. Overexpression of AtPCS1 and AtABCC1 resulted in plants exhibiting increased arsenic tolerance. Our findings demonstrate that AtABCC1 and AtABCC2 are the long-sought and major vacuolar PC transporters. Modulation of vacuolar PC transporters in other plants may allow engineering of plants suited either for phytoremediation or reduced accumulation of arsenic in edible organs.
砷是一种极其有毒的类金属，会导致严重的健康问题。在东南亚，为数千万人提供饮用水和农业用水的含水层受到砷的污染。为了减少通过食用受污染的植物摄入营养性砷，鉴定植物中砷的积累和解毒机制是前提。植物螯合肽（PCs）是谷胱甘肽衍生的肽，可螯合重金属和类金属如砷，从而作为其解毒的第一步。植物液泡充当重金属和砷的最终解毒储存库。将有毒金属（类）物隔离在植物液泡中的必需 PC-金属（类）转运蛋白长期以来一直被寻求，但在植物中仍未被鉴定。在这里，我们表明，在缺乏两种 ABCC 型转运蛋白 AtABCC1 和 AtABCC2 的情况下，拟南芥对砷和基于砷的除草剂非常敏感。在产生植物螯合肽的酿酒酵母中异源表达这些 ABCC 转运蛋白可增强砷耐受性和积累。此外，从这些酵母中分离的膜泡表现出明显的亚砷酸盐 [As（III）]-PC（2）转运活性。来自 atabcc1 atabcc2 双敲除植物的液泡分离物表现出非常低的残留 As（III）-PC（2）转运活性，有趣的是，当暴露于砷时，突变体植物中产生的 PC 较少。AtPCS1 和 AtABCC1 的过表达导致植物表现出增强的砷耐受性。我们的研究结果表明，AtABCC1 和 AtABCC2 是长期以来被寻找的主要液泡 PC 转运蛋白。调节其他植物中的液泡 PC 转运蛋白可能允许设计适合植物修复或减少可食用器官中砷积累的植物。
