title: Adult heat tolerance variation in Drosophila melanogaster is not related to Hsp70 expression.
abstract: Expression of heat-inducible Hsp70 is considered closely linked to thermotolerance in Drosophila melanogaster and other ectotherms. However, intra-specific variation of Hsp70 expression levels and its relationship to heat resistance has only been investigated in a few studies. Although in Drosophila larvae Hsp70 expression may be a key determinant of heat tolerance, the evidence for this in adults is equivocal. We therefore examined heat-induced Hsp70 expression and several measurements of adult heat tolerance in three independent collections of D. melanogaster, measured in three laboratories and using slightly different protocols. Expression levels of Hsp70 were quantified using ELISA or Western blots on extracts from adult females. Both Hsp70 and heat tolerance exhibited substantial within-population variation as previously reported. However, in all experiments there were no significant correlation between Hsp70 expression and laboratory assays of adult heat tolerance commonly used in Drosophila. When combining data across three studies we had high power to detect associations but the results showed that variation in Hsp70 expression is only likely to explain a small proportion of variation in adult heat tolerance. Therefore, although Hsp70 expression is a major component of the cellular heat stress response, its influence on intra-specific heat tolerance variation may be life-stage specific.
authors.affiliation: Department of Biological Sciences, Aarhus University, Aarhus, Denmark. ltj@mb.au.dk
authors.forename: Louise Toft
authors.initials: LT
authors.lastname: Jensen
authors.forename: Fiona Elizabeth
authors.initials: FE
authors.lastname: Cockerell
authors.forename: Torsten Nygaard
authors.initials: TN
authors.lastname: Kristensen
authors.forename: Lea
authors.initials: L
authors.lastname: Rako
authors.forename: Volker
authors.initials: V
authors.lastname: Loeschcke
authors.forename: Stephen William
authors.initials: SW
authors.lastname: McKechnie
authors.forename: Ary Anthony
authors.initials: AA
authors.lastname: Hoffmann
mesh_terms: D000818:Animals; D015153:Blotting, Western; D029721:Drosophila Proteins / Q000096:biosynthesis / Q000502:physiology*; D004331:Drosophila melanogaster / Q000502:physiology*; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D014644:Genetic Variation / Q000502:physiology; D018840:HSP70 Heat-Shock Proteins / Q000096:biosynthesis / Q000502:physiology*; D006358:Hot Temperature; D007814:Larva / Q000502:physiology; D008018:Life Cycle Stages / Q000502:physiology; D008297:Male
chemical_list: D029721:Drosophila Proteins; D018840:HSP70 Heat-Shock Proteins