Timmermans Martijn J T N, Ellers Jacintha, Roelofs Dick, van Straalen Nico M
Department of Animal Ecology, Institute of Ecological Science, Vrije Universiteit, Amsterdam, The Netherlands.
Ecotoxicology. 2005 Oct;14(7):727-39. doi: 10.1007/s10646-005-0020-x. Epub 2005 Sep 28.
Metal contamination in soil ecosystems is a permanent and often strong selection pressure. The present study investigates metal tolerance in 17 Orchesella cincta (Collembola) populations from metal-contaminated and reference sites, and combines analyses at the phenotypic and molecular level. Metal tolerance was phenotypically assayed by measuring survival times of laboratory cultures during exposure to cadmium. Comparisons of survival curves showed that five out of eight metal-stressed populations tested evolved increased cadmium tolerance (Stolberg, Plombieres, Hoboken, Hygum and Gusum). In addition, the role of the metallothionein (MT) gene in cadmium tolerance of O. cincta was studied by means of quantitative RT-PCR. The constitutive and Cd-induced MT mRNA expression of the laboratory cultures was measured. Results show that the mean constitutive MT mRNA expression of populations from polluted sites was significantly higher than of populations from reference sites. However, no correlation between MT mRNA expression levels after laboratory exposure to cadmium and field cadmium concentrations was observed. Furthermore, no relation between survival rate during exposure to cadmium and MT mRNA expression was detected. Our results suggest that constitutive MT mRNA expression plays a role in early protection against cadmium toxicity, and indicate that mechanisms other then MT up-regulation are involved in tolerance to prolonged exposure to cadmium.
土壤生态系统中的金属污染是一种持续且往往很强的选择压力。本研究调查了来自金属污染场地和对照场地的17个环带奥甲螨（弹尾目）种群的金属耐受性，并结合了表型和分子水平的分析。通过测量实验室培养物在镉暴露期间的存活时间，对金属耐受性进行了表型分析。存活曲线的比较表明，在测试的8个金属胁迫种群中，有5个进化出了更高的镉耐受性（斯托尔贝格、普隆比耶尔、霍博肯、许古姆和古苏姆）。此外，通过定量逆转录聚合酶链反应研究了金属硫蛋白（MT）基因在环带奥甲螨镉耐受性中的作用。测量了实验室培养物中组成型和镉诱导型MT mRNA的表达。结果表明，污染场地种群的平均组成型MT mRNA表达显著高于对照场地种群。然而，未观察到实验室镉暴露后MT mRNA表达水平与田间镉浓度之间的相关性。此外，未检测到镉暴露期间的存活率与MT mRNA表达之间的关系。我们的结果表明，组成型MT mRNA表达在早期抵抗镉毒性中起作用，并表明除了MT上调之外的其他机制参与了对长期镉暴露的耐受性。
