title: Interpopulation differences in expression of candidate genes for salinity tolerance in winter migrating anadromous brown trout (Salmo trutta L.).
abstract: BACKGROUND
  Winter migration of immature brown trout (Salmo trutta) into freshwater rivers has been hypothesized to result from physiologically stressful combinations of high salinity and low temperature in the sea.
  
  
  RESULTS
  We sampled brown trout from two Danish populations entering different saline conditions and quantified expression of the hsp70 and Na/K-ATPases alpha 1b genes following acclimation to freshwater and full-strength seawater at 2 degrees C and 10 degrees C. An interaction effect of low temperature and high salinity on expression of both hsp70 and Na/K-ATPase alpha 1b was found in trout from the river entering high saline conditions, while a temperature independent up-regulation of both genes in full-strength seawater was found for trout entering marine conditions with lower salinities.
  
  
  CONCLUSIONS
  Overall our results support the hypothesis that physiologically stressful conditions in the sea drive sea-run brown trout into freshwater rivers in winter. However, our results also demonstrate intra-specific differences in expression of important stress and osmoregulative genes most likely reflecting adaptive differences between trout populations on a regional scale, thus strongly suggesting local adaptations driven by the local marine environment.
authors.affiliation: Technical University of Denmark, Danish Institute for Fisheries Research, Department of Inland Fisheries, DK-8600 Silkeborg, Denmark. pfl@difres.dk
authors.forename: Peter F
authors.initials: PF
authors.lastname: Larsen
authors.forename: Einar E
authors.initials: EE
authors.lastname: Nielsen
authors.forename: Anders
authors.initials: A
authors.lastname: Koed
authors.forename: Dennis S
authors.initials: DS
authors.lastname: Thomsen
authors.forename: Pål A
authors.initials: PA
authors.lastname: Olsvik
authors.forename: Volker
authors.initials: V
authors.lastname: Loeschcke
mesh_terms: D000064:Acclimatization; D025041:Animal Migration; D000818:Animals; D005618:Fresh Water; D014644:Genetic Variation; D005880:Gills / Q000201:enzymology; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D054712:Salinity; D012623:Seawater; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism; D014337:Trout / Q000235:genetics*
chemical_list: D018840:HSP70 Heat-Shock Proteins; D000254:Sodium-Potassium-Exchanging ATPase