Wednesday, December 13, 2006 - 8:17 AM
1055

Microevolution and transcriptional regulation in the Orchesella cincta metallothionein promoter

Thierry K. S. Janssens1, Dick Roelofs, dick.roelofs@ecology.falw.vu.nl1, Janine Mariën, janine.marien@ecology.falw.vu.nl1, Peter Cenijn, peter.cenijn@ivm.vu.nl2, J. Legler, juliette.legler@ivm.vu.nl2, and Nico M. Van Straalen, nico.van.straalen@ecology.falw.vu.nl1. (1) Vrije Universiteit Amsterdam, Department of Animal Ecology, Institute of Ecological Science, De Boelelaan 1085, Amsterdam, Netherlands, (2) Vrije Universiteit Amsterdam, Institute for Environmental Studies, De Boelelaan 1085, Amsterdam, Netherlands

Strong evidence exists for adaptation to heavy metals, i.e. cadmium and lead, in populations of the soil arthropod O. cincta from heavy metal contaminated sites. A cadmium binding metallothionein (mt) was isolated, which is significantly higher expressed in a population from an old Pb-Zn mine, compared to a control population. Previous research suggested significant additive genetic variation for transcriptional regulation of the mt. Eight alleles of the promoter, 1.3 kb 5’ of the mt ORF, have been sequenced which differ in the number and the arrangement of transcription factor binding sites, such as metal responsive elements (MRE), antioxidant responsive element (ARE), molting hormone receptor sites. The dose-response relationship by heavy metals, oxidative stress and 20-hydroxyecdysone on the induction of these promoter alleles was analyzed in a luciferase reporter assay in an insect cell line. Striking differences in inducibility by Cd and oxidative stress (paraquat) were detected and allele frequencies in a preliminary field study suggest a combination of balancing and positive selection in a metal polluted environment.


Species 1: Collembola Entomobryidae Orchesella cincta