title: Erythrocyte heat shock protein responses to chronic (in vivo) and acute (in vitro) temperature challenge in diploid and triploid salmonids.
abstract: This research investigated how ploidy level (diploid versus triploid) affects the heat shock protein (HSP) response in erythrocytes under different thermal stress regimes, both in vivo and in vitro, in Atlantic salmon (Salmo salar) and brook charr (Salvelinus fontinalis) in order to address the question of why triploids typically have reduced thermal tolerance. A preliminary study confirmed that identical volumes of diploid and triploid erythrocytes (which equates to a smaller number of larger cells for triploids compared to diploids) did not differ in total protein synthesis rates. After chronic (100d) acclimation of fish to 5, 15 and 25°C, triploid erythrocytes had lower HSP70, HSP90, heat shock factor 1 (HSF1) and ubiquitin (free and total) levels than diploids in both species. Furthermore, Atlantic salmon erythrocytes showed significantly higher protein breakdown (based on conjugated ubiquitin levels) in triploids than diploids after acute heat stress in vitro, but no significant difference was detected between ploidies after acute cold stress. These results indicate that: 1) triploid erythrocytes synthesize more total protein per cell than diploids as a result of increased cell size; 2) triploids have sufficient total HSP levels for survival under low stress conditions; and 3) the lower basal titres of HSPs in triploids may be a handicap when combating acute stress. Taken together, this suggests that triploids are limited in their ability to withstand thermal stress because of a reduced ability to maintain proteostasis under stressful conditions.
authors.affiliation: Department of Biology, University of New Brunswick, P.O. Box 4400, Fredericton, New Brunswick E3B 5A3, Canada.
authors.forename: Pillai V
authors.initials: PV
authors.lastname: Saranyan
authors.affiliation: Institute for Marine Biosciences, National Research Council of Canada, 1411 Oxford Street, Halifax, Nova Scotia B3H 3Z1, Canada.
authors.forename: Neil W
authors.initials: NW
authors.lastname: Ross
authors.affiliation: Department of Biology, University of New Brunswick, P.O. Box 4400, Fredericton, New Brunswick E3B 5A3, Canada. Electronic address: benfey@unb.ca.
authors.forename: Tillmann J
authors.initials: TJ
authors.lastname: Benfey
mesh_terms: D000064:Acclimatization; D000818:Animals; D017756:Aquaculture; D048429:Cell Size; D003080:Cold Temperature / Q000009:adverse effects; D004268:DNA-Binding Proteins / Q000096:biosynthesis / Q000097:blood / Q000378:metabolism; D004171:Diploidy; D004912:Erythrocytes / Q000166:cytology / Q000378:metabolism*; D029941:Fish Proteins / Q000096:biosynthesis / Q000097:blood / Q000378:metabolism; D005786:Gene Expression Regulation; D018840:HSP70 Heat-Shock Proteins / Q000096:biosynthesis / Q000097:blood / Q000378:metabolism; D018841:HSP90 Heat-Shock Proteins / Q000096:biosynthesis / Q000097:blood / Q000378:metabolism; D000076249:Heat Shock Transcription Factors; D006360:Heat-Shock Proteins / Q000096:biosynthesis* / Q000097:blood / Q000378:metabolism; D066298:In Vitro Techniques / Q000662:veterinary; D008297:Male; D055550:Protein Stability; D012474:Salmon / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D013045:Species Specificity; D013312:Stress, Physiological; D014157:Transcription Factors / Q000096:biosynthesis / Q000097:blood / Q000378:metabolism; D057885:Triploidy; D014337:Trout / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D025801:Ubiquitin / Q000096:biosynthesis / Q000097:blood / Q000378:metabolism
chemical_list: D004268:DNA-Binding Proteins; D029941:Fish Proteins; D018840:HSP70 Heat-Shock Proteins; D018841:HSP90 Heat-Shock Proteins; D000076249:Heat Shock Transcription Factors; D006360:Heat-Shock Proteins; D014157:Transcription Factors; D025801:Ubiquitin
keywords: HSP; Proteostasis; Salmonid; Stress response; Triploidy