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) 等有毒金属含量较高的土壤和水中对人类和环境健康有害。这四种金属属于超级基金的前五名优先危险物质。研究表明，通过根系将重金属吸收到植物中可以为有毒金属去除和土壤和水体修复提供有效且具有成本效益的方法。在植物和真菌中，植物螯合素是主要的重金属螯合和解毒硫醇肽，可与重金属（包括镉、锌、铅、汞）形成复合物并解毒，根据最近的研究，还可以解毒砷。植物螯合素合成酶 (PCS) 产生植物螯合素，因此是植物中主要的催化金属解毒机制。然而，编码植物螯合素合酶的基因尚未被鉴定。我们最近在植物和真菌中克隆了一个编码植物螯合素合酶的新基因家族（PCS）。 PCS cDNA 在酿酒酵母中的表达显着增强了对镉的抵抗力。粟酒裂殖酵母和拟南芥中 PCS 基因的破坏会增加重金属敏感性。重组 PCS 蛋白在体外合成植物螯合素。我们将测试以下假设：应激信号通路有助于 PCS 诱导和解毒，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增强植物对重金属的过度积累和去除。为了检验这些假设，我们将： (I) 表征诱导 PCS 表达的信号传导机制。 (II) 表征芥菜中 PCS 的表达和定位，芥菜是正在研究重金属生物介导的主要植物物种之一。 (III) 追求 PCS 植物中的转基因过度表达以及相关的金属解毒机制，以测试增强的重金属耐受性和积累，以及 (IV) 向 Phytotech Inc 提供选定的转基因品系，以纳入超级基金站点的田间试验。 (V) 在拟南芥和镉诱导的微阵列分析中寻求新的基因激活标签筛选，以确定与植物中重金属积累有关的新基因和途径。这些研究的结果可以在未来植物修复策略的制定中发挥核心作用，该策略用于吸收重金属以及从受污染的土壤和水中生物去除重金属。