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Alternative TitleExpression study of Tetrahymena thermophila tox-genes exposed to cadmium and DDT
Thesis Advisor沈蕴芬 ; 缪炜
Degree Grantor中国科学院水生生物研究所
Place of Conferral水生生物研究所
Degree Discipline动物学
Keyword Ddt 嗜热四膜虫 毒性相关基因 荧光定量pcr
Abstract重金属污染和环境类雌激素污染是当前人类面对的两大重要环境问题,本研究以两类物质中的镉和DDT为代表,针对它们分子机理复杂、缺乏高效灵敏的环境监测评价系统等问题,以原生动物嗜热四膜虫为材料,利用实时荧光定量PCR方法,开展了以下分子毒理学研究: 考察了不同浓度的镉单独存在、以及与铜共存情况下嗜热四膜虫金属硫蛋白MTT1基因的表达规律:镉离子对MTT1基因表达的诱导更灵敏,且在一定阈值浓度(≤35.2 mol/L)范围内,MTT1基因的表达量随镉离子浓度的升高而增加,超过该阈值后表达量迅速下降;镉与铜同时诱导时,该阈值浓度减小为22 mol/L,表明二者的联合毒性为协同作用,并且镉离子在浓度低于22 mol/L时,与铜离子的共同作用大大增加了MTT1基因的表达量,从而增强了四膜虫的解毒能力。探讨了镉的单独毒性和镉铜共存时协同毒性的可能分子机理。 在克隆得到5个嗜热四膜虫DDT毒性相关基因(TtSCP-2、TtOMC、TtGST、TtCYP和NgoA)cDNA全长序列的基础上,分析它们的结构特征、功能背景和在不同浓度DDT暴露下的表达情况以及基因上游调控序列发现:这些基因均与DDT胁迫下细胞的毒理相关生理生化过程有关,包括细胞内物质转运(TtSCP-2及TtOMC)、毒物胁迫下的细胞毒性产生(所有5个基因)和异生质代谢过程(TtGST及TtCYP)等,有助于从分子水平揭示环境雌激素类物质对真核生物产生细胞毒性的机理;同时在一定DDT浓度范围内这些基因的表达变化显著,因此可作为对DDT以及类似的环境雌激素物质具有特异响应的重要候选分子标记,为最终构建特异、灵敏的四膜虫毒性评价体系提供了理论与实验基础。
Other AbstractThe heavy metal pollutions and environmental estrogen pollutions are two crucial environmental problems faced by human beings. In this study, with two representative substances cadmium and DDT, considering their complicated molecular mechanisms and lack of effective and sensitive monitoring assessment system, using fluorescent real-time PCR method and Tetrahymena thermophila cells as materials, we carried out research introduced as follows: The expression of metallothionein gene (MTT1) in T. thermophila treated with different concentrations of heavy metals cadmium and copper was studied, of which the results shows: MTT1 gene was more sensitive to cadmium induction compared to copper, and in a certain threshold scale (≤35.2 mol/L), raising the cadmium concentrations increased the MTT1 expression level, but made it decreased while beyond the threshold; the expression rule of MTT1 induced by both cadmium and copper was similar to that treated with cadmium only, but then the threshold down to 22 mol/L, indicating that combined toxicity of cadmium and copper in T. thermophila was synergism. When treating concentration was lower than 22 mol/L, cadmium cooperated with 244 mol/L copper greatly increased the expression level of MTT1, hence enhancing the detoxification ability of Tetrahymena. The potential molecular mechanism of combined toxicity caused by cadmium alone or with copper together was also discussed. Based on cloning and sequencing of five T. thermophila tox-genes (TtSCP-2、TtOMC、TtGST、TtCYP and NgoA), analysis were made to their structural features, function backgrounds, expression levels exposed to different concentrations of DDT and the genes’ upstream-side regulation sequences while the results suggests: The 5 genes are all related to the physiological and biochemical processes involved in cell toxicology under DDT treatment, including intracellular transportation (TtSCP-2 and TtOMC), cellular toxicity genesis under toxic substances treatment (all of the 5 genes) and xenobiotic metabolic processes (TtGST and TtCYP), which is helpful to elucidate mechanisms of cell toxicity genesis caused by environmental estrogens in Eukaryotics; the remarkable changes on their expression levels under certain DDT concentrations also indicate that these genes could be taken as important molecular marks specific responsive to DDT and environmental estrogens, thus providing theoretical and experimental bases on which the final goal aiming to a Tetrahymena monitoring and assessment system with high specificity and sensitivity could be achieved.
Document Type学位论文
Recommended Citation
GB/T 7714
俞婷. 镉和DDT暴露下嗜热四膜虫毒性相关基因的表达研究[D]. 水生生物研究所. 中国科学院水生生物研究所,2006.
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