title: Different Relationship betweenhsp70mRNA and hsp70 Levels in the Heat Shock Response of Two Salmonids with Dissimilar Temperature Preference.
abstract: The heat shock response (HSR) refers to the rapid production of heat shock proteins (hsps) in response to a sudden increase in temperature. Its regulation by heat shock factors is a good example of how gene expression is transcriptionally regulated by environmental stresses. In contrast, little is known about post-transcriptional regulation of the response. The heat shock response is often used to characterize the temperature tolerance of species with the rationale that whenever the response sets on, a species is approaching its lethal temperature. It has commonly been considered that an increase inhspmRNA gives an accurate indication that the same happens to the protein level, but this need not be the case. With climate change, understanding the effects of temperature on gene expression of especially polar organisms has become imperative to evaluate how both biodiversity and commercially important species respond, since temperature increases are expected to be largest in polar areas. Here we studied the HSR of two phylogenetically related Arctic species, which differ in their temperature tolerance with Arctic charr having lower maximally tolerated temperature than Atlantic salmon. Arctic charr acclimated to 15°C and exposed to 7°C temperature increase for 30 min showed both an increase inhsp70mRNA and hsp70 whereas in salmon onlyhsp70mRNA increased. Our results indicate that the temperature for transcriptional induction ofhspcan be different from the one required for a measurable change in inducible hsp level. The species with lower temperature tolerance, Arctic charr, are experiencing temperature stress already at the higher acclimation temperature, 15°C, as theirhsp70mRNA and hsp70 levels were higher, and they grow less than fish at 8°C (whereas for salmon the opposite is true). Consequently, charr experience more drastic heat shock than salmon. Although further studies are needed to establish the temperature range and length of exposure wherehspmRNA and hsp level are disconnected, the observation suggests that by measuring bothhspmRNA and hsp level, one can evaluate if a species is approaching the higher end of its temperature tolerance, and thus evaluate the vulnerability of an organism to the challenges imposed by elevated water temperature.
authors.affiliation: Laboratory of Animal Physiology, Department of Biology, University of Turku Turku, Finland.
authors.forename: Mario
authors.initials: M
authors.lastname: Lewis
authors.affiliation: Laboratory of Animal Physiology, Department of Biology, University of Turku Turku, Finland.
authors.forename: Miriam
authors.initials: M
authors.lastname: Götting
authors.affiliation: Laboratory of Animal Physiology, Department of Biology, University of Turku Turku, Finland.
authors.forename: Katja
authors.initials: K
authors.lastname: Anttila
authors.affiliation: Laboratory of Animal Physiology, Department of Biology, University of Turku Turku, Finland.
authors.forename: Mirella
authors.initials: M
authors.lastname: Kanerva
authors.affiliation: Laboratory of Animal Physiology, Department of Biology, University of Turku Turku, Finland.
authors.forename: Jenni M
authors.initials: JM
authors.lastname: Prokkola
authors.affiliation: Natural Resources Institute Finland (Luke) Enonkoski, Finland.
authors.forename: Eila
authors.initials: E
authors.lastname: Seppänen
authors.affiliation: Natural Resources Institute Finland (Luke) Enonkoski, Finland.
authors.forename: Irma
authors.initials: I
authors.lastname: Kolari
authors.affiliation: Laboratory of Animal Physiology, Department of Biology, University of Turku Turku, Finland.
authors.forename: Mikko
authors.initials: M
authors.lastname: Nikinmaa
keywords: chaperones; climate change; heat shock proteins; heat shock response; salmonids; temperature acclimation