Cold adaptation increases rates of nutrient flow and metabolic plasticity during cold exposure in Drosophila melanogaster.
Metabolic flexibility is an important component of adaptation to stressful environments, including thermal stress and latitudinal adaptation. A long history of population genetic studies suggest that selection on core metabolic enzymes may shape life histories by altering metabolic flux. However, the direct relationship between selection on thermal stress hardiness and metabolic flux has not previously been tested. We investigated flexibility of nutrient catabolism during cold stress in Drosophila melanogaster artificially selected for fast or slow recovery from chill coma (i.e. cold-hardy or -susceptible), specifically testing the hypothesis that stress adaptation increases metabolic turnover. Using (13)C-labelled glucose, we first showed that cold-hardy flies more rapidly incorporate ingested carbon into amino acids and newly synthesized glucose, permitting rapid synthesis of proline, a compound shown elsewhere to improve survival of cold stress. Second, using glucose and leucine tracers we showed that cold-hardy flies had higher oxidation rates than cold-susceptible flies before cold exposure, similar oxidation rates during cold exposure, and returned to higher oxidation rates during recovery. Additionally, cold-hardy flies transferred compounds among body pools more rapidly during cold exposure and recovery. Increased metabolic turnover may allow cold-adapted flies to better prepare for, resist and repair/tolerate cold damage. This work illustrates for the first time differences in nutrient fluxes associated with cold adaptation, suggesting that metabolic costs associated with cold hardiness could invoke resource-based trade-offs that shape life histories.
Department of Entomology and Nematology, University of Florida, Gainesville, FL 32611, USA Department of Integrative Biology, University of California, Berkeley, CA 94720, USA cmw@berkeley.edu.
Caroline M
0000-0003-3112-0286
CM
Williams
Department of Biological Sciences, St Mary's University, San Antonio, TX 78228, USA.
Marshall D
MD
McCue
Department of Medicine, University of Florida, Gainesville, FL 32601, USA.
Nishanth E
NE
Sunny
Department of Entomology and Nematology, University of Florida, Gainesville, FL 32611, USA Department of Integrative Biology, University of California, Berkeley, CA 94720, USA.
Andre
A
Szejner-Sigal
Division of Biology, Kansas State University, Manhattan, KS 66506, USA.
Theodore J
TJ
Morgan
Section on Statistical Genetics, Department of Biostatistics, University of Alabama at Birmingham, Birmingham, AL 35294, USA.
David B
DB
Allison
Department of Entomology and Nematology, University of Florida, Gainesville, FL 32611, USA Genetics Institute, University of Florida, Gainesville, FL 32610, USA.
Daniel A
DA
Hahn
D000064:Acclimatization / Q000502:physiology*; D000818:Animals; D003080:Cold Temperature; D004331:Drosophila melanogaster / Q000378:metabolism*; D005502:Food; D008018:Life Cycle Stages
chill coma; ectotherm; insect; metabolism; stable isotopes; stress hardiness