Studies on phytoextraction and phytomining of heavy metals

本研究的主要目的是阐明金属结合肽、植物螯合素在重金属转运和动态平衡中的作用，并以日本常见植物镍超积累植物刺参和锰超积累植物刺参为例，对转运蛋白的功能进行分析。比较了来自北海道三个不同地区的日本血吸虫生态型对镍锌的积累能力。结果表明：1.不同生态型和不同生境的日本血藤植株均能积累较高的镍/锌积累量。从日本血吸虫中克隆了植物螯合素合成酶基因，命名为TjPCS。用TjPCS转化的酵母对Cd~(2+)有明显的耐性。从Cd超积累植物蓝藻中克隆到相同的基因。从日本血吸虫中克隆了ZIP和NRAMP金属转运蛋白的同源基因，克隆了两个ZIP转运蛋白基因(TjZNT1，2)和一个NRAMP基因(TjNRAMP4)。转化TjZNT1、2的酵母菌对Ni~(2+)的耐受性显著提高。相反，TjNRAMP4的表达引起细胞对镍离子敏感性和镍离子浓度的升高。接穗木霉在持续降低培养液pH值的同时，还需要进一步研究这些基因在植物中的表达，以阐明这些基因在植物中的作用，并利用转化的植物进行植物修复。

The main purposes of this study are clarification of the role of metal-binding peptides, phytochelatin, and functional analysis of transporters in heavy metal transport and homeostasis using Ni hyperaccumulator Thlaspi japonicum and Mn hyperaccumulator Chengiopanax sciadophylloides, ordinary plants in Japan.1. Ni/Zn accumulation ability of T. japonicum ecotypes from three different areas in Hokkaido was compared. T. japonicum plants were able to accumulate high Ni/Zn accumulation regardless ecotype and habitat.2. The phytochelatin synthase gene was cloned from T. japonicum and designated as TjPCS. The yeast transformed with the TjPCSshowed an obvious Cd^<2+> tolerance. The same gene was cloned from a Cd hyperaccumulator plant Thlaspi caerulescens.3. Homologous genes of ZIP and NRAMP metal transporters were cloned from T. japonicum and two ZIP transporter genes (TjZNT1, 2) and one NRAMP gene (TjNRAMP4) were cloned. The yeast transformed with TjZNT1, 2 showed a marked increase in Ni^<2+> tolerance. In contrast, the expression of TjNRAMP4 caused elevation of Ni^<2+> sensitivity and Ni^<2+> concentration.4. C. sciadophylloides lowered the pH of the culture solution continuously and simultaneously solubilized MnO_2 in the medium Further studies on each gene expression in plants are needed to clarify the role of these genes in plants and to use the transformed plants for phytoremediation.