title: Metallothionein mRNA expression and cadmium tolerance in metal-stressed and reference populations of the springtail Orchesella cincta.
abstract: 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.
authors.affiliation: Department of Animal Ecology, Institute of Ecological Science, Vrije Universiteit, Amsterdam, The Netherlands. martijn.timmermans@falw.vu.nl
authors.forename: Martijn J T N
authors.initials: MJ
authors.lastname: Timmermans
authors.forename: Jacintha
authors.initials: J
authors.lastname: Ellers
authors.forename: Dick
authors.initials: D
authors.lastname: Roelofs
authors.forename: Nico M
authors.initials: NM
authors.lastname: van Straalen
mesh_terms: D000222:Adaptation, Physiological; D000818:Animals; D001181:Arthropods / Q000187:drug effects* / Q000378:metabolism; D004784:Environmental Monitoring; D005060:Europe; D005786:Gene Expression Regulation / Q000187:drug effects; D008668:Metallothionein / Q000235:genetics / Q000378:metabolism*; D019216:Metals, Heavy / Q000032:analysis / Q000633:toxicity*; D012333:RNA, Messenger / Q000378:metabolism; D012989:Soil Pollutants / Q000032:analysis / Q000633:toxicity*; D023382:Toxicity Tests, Acute
chemical_list: D019216:Metals, Heavy; D012333:RNA, Messenger; D012989:Soil Pollutants; D008668:Metallothionein