我们前期研究发现，我国北方天然草原地区分布的马蔺适应镉胁迫的对策是根系将吸收的大量Cd2+，经长距离运输富集在地上部以增强镉耐受性，但它是如何从介质中吸收Cd2+的分子机理仍不清楚。天然抗性相关巨噬细胞蛋白NRAMP5在Cd2+吸收中起关键作用。目前Cd2+吸收研究均以镉耐受性较弱的植物为对象，其Cd2+吸收能力有限，并不是研究Cd2+吸收机理的理想材料。鉴于此，本项目拟以Cd2+吸收能力强的马蔺为材料，克隆其IlNRAMP5，利用qRT-PCR技术定量分析镉胁迫下IlNRAMP5转录丰度，并分析IlNRAMP5在根细胞与亚细胞中的定位及在酵母中的功能互补；采用RNA干扰技术沉默IlNRAMP5基因表达，测试RNA干扰转化植株各组织中的Cd2+浓度及根部Cd2+净吸收速率。以期解析IlNRAMP5在马蔺Cd2+吸收中的作用及对Cd2+转运富集的影响，将为土壤镉污染修复提供重要的理论依据。

Our previous study found that one of the strategies for adaptation of Iris lactea distributed in natural prairie of northern China to Cd stress is absorbing a great quantity of Cd2+ to accumulate in shoots via long distance transport improving Cd tolerance, however, it is how to molecular mechanism of Cd2+ uptake from medium remains still unclear. NRAMP5, a Natural Resistance-Associated Macrophage Proteins, plays a pivotal role in Cd2+ uptake in plants. At present, plants used in these researches were not the ideal materials for Cd2+ uptake mechanism due to the weak Cd tolerance with limited Cd2+ absorption capacity. In view of this, the present project will take the strong Cd2+ absorption capacity of I. lacea as experimental material to clone IlNRAMP5; the transcript abundances of IlNRAMP5 is quantificationally analyzed by qRT-PCR technique under Cd stress; root cellular/subcellular localization of IlNRAMP5 and its functional complementation in yeast are investigated; Cd2+ concentrations in different tissues and the net absorption rate of Cd2+ in roots is measured after gene silencing of IlNRAMP5 using RNA interference technique, which dissects the role of IlNRAMP5 in Cd2+ uptake pathway and in the effect on Cd2+ translocation and accumulation in plants exposed to Cd. This would provide an important theoretical basis for the remediation of Cd contaminated soils.