title: Functional divergence of type 2 deiodinase paralogs in the Atlantic salmon.
abstract: Thyroid hormone (TH) is an ancestral signal linked to seasonal life history transitions throughout vertebrates. TH action depends upon tissue-localized regulation of levels of active TH (triiodothyronine, T3), through spatiotemporal expression of thyroid hormone deiodinase (dio) genes. We investigated the dio gene family in juvenile Atlantic salmon (Salmo salar) parr, which prepare for seaward migration in the spring (smoltification) through TH-dependent changes in physiology. We identified two type 2 deiodinase paralogs, dio2a and dio2b, responsible for conversion of thyroxine (T4) to T3. During smoltification, dio2b was induced in the brain and gills in zones of cell proliferation following increasing day length. Contrastingly, dio2a expression was induced in the gills by transfer to salt water (SW), with the magnitude of the response proportional to the plasma chloride level. This response reflected a selective enrichment for osmotic response elements (OREs) in the dio2a promoter region. Transcriptomic profiling of gill tissue from fish transferred to SW plus or minus the deiodinase inhibitor, iopanoic acid, revealed SW-induced increases in cellular respiration as the principal consequence of gill dio2 activity. Divergent evolution of dio2 paralogs supports organ-specific timing of the TH-dependent events governing the phenotypic plasticity required for migration to sea.
authors: Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen AB24 2TZ, UK.
authors: Marlene
authors: M
authors: Lorgen
authors: Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen AB24 2TZ, UK.
authors: Elisa
authors: E
authors: Casadei
authors: Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen AB24 2TZ, UK.
authors: Elżbieta
authors: E
authors: Król
authors: Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen AB24 2TZ, UK.
authors: Alex
authors: A
authors: Douglas
authors: Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen AB24 2TZ, UK.
authors: Mike J
authors: MJ
authors: Birnie
authors: Uni Research Environment, Uni Research AS, Thormøhlensgt 49B, 5006 Bergen, Norway.
authors: Lars O E
authors: LO
authors: Ebbesson
authors: Uni Research Environment, Uni Research AS, Thormøhlensgt 49B, 5006 Bergen, Norway.
authors: Tom O
authors: TO
authors: Nilsen
authors: Zoological Society London, Institute of Zoology, London NW1 4RY, UK.
authors: William C
authors: WC
authors: Jordan
authors: Department of Arctic and Marine Biology, Faculty of BioSciences, Fisheries and Economy, University of Tromsø, 9037 Tromsø, Norway.
authors: Even H
authors: EH
authors: Jørgensen
authors: INRA UMR85, CNRS UMR7247, Université de Tours, IFCE, 37380 Nouzilly, France.
authors: Hugues
authors: H
authors: Dardente
authors: Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen AB24 2TZ, UK; Department of Arctic and Marine Biology, Faculty of BioSciences, Fisheries and Economy, University of Tromsø, 9037 Tromsø, Norway. Electronic address: david.hazlerigg@uit.no.
authors: David G
authors: DG
authors: Hazlerigg
authors: Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen AB24 2TZ, UK.
authors: Samuel A M
authors: SA
authors: Martin
mesh_terms: D000818:Animals; D005880:Gills / Q000254:growth & development / Q000378:metabolism*; D007453:Iodide Peroxidase / Q000235:genetics / Q000378:metabolism*; D008018:Life Cycle Stages / Q000235:genetics / Q000502:physiology*; D008969:Molecular Sequence Data; D009997:Osmotic Pressure; D020317:Salmo salar / Q000254:growth & development*; D012621:Seasons; D013963:Thyroid Hormones / Q000235:genetics / Q000378:metabolism*; D013974:Thyroxine / Q000378:metabolism; D014284:Triiodothyronine / Q000378:metabolism; D000097564:Iodothyronine Deiodinase Type II
chemical_list: D007453:Iodide Peroxidase; D013963:Thyroid Hormones; D013974:Thyroxine; D014284:Triiodothyronine; D000097564:Iodothyronine Deiodinase Type II