title: Thermal fluctuations affect the transcriptome through mechanisms independent of average temperature.
abstract: Terrestrial ectotherms are challenged by variation in both mean and variance of temperature. Phenotypic plasticity (thermal acclimation) might mitigate adverse effects, however, we lack a fundamental understanding of the molecular mechanisms of thermal acclimation and how they are affected by fluctuating temperature. Here we investigated the effect of thermal acclimation in Drosophila melanogaster on critical thermal maxima (CTmax) and associated global gene expression profiles as induced by two constant and two ecologically relevant (non-stressful) diurnally fluctuating temperature regimes. Both mean and fluctuation of temperature contributed to thermal acclimation and affected the transcriptome. The transcriptomic response to mean temperatures comprised modification of a major part of the transcriptome, while the response to fluctuations affected a much smaller set of genes, which was highly independent of both the response to a change in mean temperature and to the classic heat shock response. Although the independent transcriptional effects caused by fluctuations were relatively small, they are likely to contribute to our understanding of thermal adaptation. We provide evidence that environmental sensing, particularly phototransduction, is a central mechanism underlying the regulation of thermal acclimation to fluctuating temperatures. Thus, genes and pathways involved in phototransduction are likely of importance in fluctuating climates.
authors.affiliation: Department of Bioscience, Section for Genetics, Ecology and Evolution, Aarhus University, Ny Munkegade 114, 8000 Aarhus C, Denmark.
authors.forename: Jesper Givskov
authors.initials: JG
authors.lastname: Sørensen
authors.affiliation: Department of Bioscience, Section for Genetics, Ecology and Evolution, Aarhus University, Ny Munkegade 114, 8000 Aarhus C, Denmark.
authors.forename: Mads Fristrup
authors.initials: MF
authors.lastname: Schou
authors.affiliation: Department of Chemistry and Bioscience, Aalborg University, Fredrik Bajers Vej 7H, 9220 Aalborg E, Denmark.
authors.forename: Torsten Nygaard
authors.initials: TN
authors.lastname: Kristensen
authors.affiliation: Department of Bioscience, Section for Genetics, Ecology and Evolution, Aarhus University, Ny Munkegade 114, 8000 Aarhus C, Denmark.
authors.forename: Volker
authors.initials: V
authors.lastname: Loeschcke
mesh_terms: D000064:Acclimatization; D000818:Animals; D004331:Drosophila melanogaster / Q000502:physiology*; D020869:Gene Expression Profiling; D006360:Heat-Shock Proteins / Q000378:metabolism*; D018869:Heat-Shock Response; D006358:Hot Temperature / Q000009:adverse effects; D055537:Light Signal Transduction / Q000235:genetics; D000071436:Thermotolerance; D059467:Transcriptome
chemical_list: D006360:Heat-Shock Proteins