Phytochelatin synthase & resistance to heavy metals

植物螯合素合酶

• 批准号: 6577797
• 负责人: JULIAN I SCHROEDER
• 金额: $ 17.5万
• 依托单位: UNIVERSITY OF CALIFORNIA, SAN DIEGO
• 依托单位国家: 美国
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-04-01 至 2003-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6577797
• 关键词: Cruciferae; arsenic; biological signal transduction; biotransformation; cadmium; environmental health; environmental toxicology; environmental transport; enzyme activity; gene expression; genetically modified plants; hazardous substances; heavy metals; lead; mercury; plant physiology; soil pollution; waste treatment; water pollution

Soils and waters with high levels of toxic metals such as cadmium (Cd), arsenic (As), lead (Pb) and mercury (Hg) are detrimental to human and environmental health. These four metals are among the Superfund;'s top five priority hazardous substances. Studies suggest that uptake of heavy metals into plant via the root system could provide a potent and cost effective approach for toxic metal removal and remediation of soils and waters. In plants and fungi, phytochelatins are major heavy metal chelating and detoxifying thiolate peptides, that form complexes with and detoxify heavy metals, including Cd, Zn, Pb, Hg and based on recent research also As. The enzyme phytochelatin synthase (PCS) produces phytochelatin, thus functioning as a major catalytic metal detoxification mechanisms in plants. However genes encoding phytochelatin synthases, had not yet been identified. We have recently cloned a new gene family (PCS) encoding phytochelatin synthases in plants and fungi. Expression of PCS cDNAs in S. cerevisiae dramatically enhance resistance to cadmium. Disruption of the PCS genes in S. pombe and Arabidopsis thaliana produces increased heavy metal sensitivity. Recombinant PCS proteins synthesize phytochelatins in vitro. We will test the hypotheses that stress-signaling pathways contribute to PCS induction and detoxification and that transgenic expression of PCS genes can, together with other metal-interacting mechanisms, enhance heavy metal hyper-accumulation and removal by plants. To test these hypotheses we will: (I) Characterize signaling mechanisms that induce PCS expression. (II) Characterize PCS expression and localization in Brassica juncea, which is one of the major plant species being studied for heavy metal biomediation. (III) Pursue transgenic over-expression in plants of PCS together with associated metal detoxification mechanisms to test for enhanced heavy metal tolerance and accumulation and (IV) provide selected transgenic lines to Phytotech Inc to include in field trials on super fund sites. (V) Pursue novel genetic activation-tagging screens in Arabidopsis and Cd-induced microarray analyses to identify new genes and pathways involved in heavy metal accumulation in plants. Results from these studies could play a central role in the development of future phytoremediation strategies for heavy metal uptake and biological removal of heavy metals form contaminated soils and waters.

镉（Cd）、砷（as）、铅（Pb）和汞（Hg）等有毒金属含量高的土壤和水体对人类和环境健康有害。这四种金属属于超级基金；美国的五大优先有害物质。研究表明，植物通过根系吸收重金属可能为有毒金属的去除和土壤和水体的修复提供一种有效且经济有效的方法。在植物和真菌中，植物螯合素是一种主要的重金属螯合解毒巯基肽，它与镉、锌、铅、汞等重金属形成络合物并解毒，近年来也有研究表明。植物螯合素合成酶（phytochelatin synthase， PCS）产生植物螯合素，是植物体内主要的金属解毒催化机制。然而，编码植物螯合素合成酶的基因尚未被确定。我们最近克隆了一个新的基因家族（PCS）编码植物和真菌中的植物螯合素合成酶。在酿酒酵母中表达PCS cdna可显著增强对镉的抗性。破坏拟南芥和拟南芥的PCS基因会增加重金属敏感性。重组PCS蛋白体外合成植物螯合素。我们将验证胁迫信号通路有助于PCS诱导和解毒的假设，以及PCS基因的转基因表达可以与其他金属相互作用机制一起促进植物对重金属的超积累和去除。为了验证这些假设，我们将：(I)表征诱导PCS表达的信号机制。（II）表征了重金属生物介导研究的主要植物之一芥菜（Brassica juncea）中PCS的表达和定位。（三）在植物中进行PCS的转基因过表达以及相关的金属解毒机制，以测试其对重金属耐受性和积累的增强；（四）向Phytotech Inc提供精选的转基因品系，在超级基金站点进行田间试验。(5)在拟南芥中开展新的基因激活标记筛选和cd诱导微阵列分析，以确定参与植物重金属积累的新基因和途径。这些研究的结果可以在未来植物修复策略的发展中发挥核心作用，以吸收和生物去除污染土壤和水中的重金属。