title: Cold acclimation allows Drosophila flies to maintain mitochondrial functioning under cold stress.
abstract: Environmental stress generally disturbs cellular homeostasis. Researchers have hypothesized that chilling injury is linked to a shortage of ATP. However, previous studies conducted on insects exposed to nonfreezing low temperatures presented conflicting results. In this study, we investigated the mitochondrial bioenergetics of Drosophila melanogaster flies exposed to chronic cold stress (4 °C). We assessed mitochondrial oxygen consumption while monitoring the rate of ATP synthesis at various times (0, 1, 2, and 3 days) during prolonged cold stress and at two assay temperatures (25 and 4 °C). We compared organelle responses between cold-susceptible and cold-acclimated phenotypes. Continuous exposure to low temperature provoked temporal declines in the rates of mitochondrial respiration and ATP synthesis. Respiratory control ratios (RCRs) suggested that mitochondria were not critically uncoupled. Nevertheless, after 3 days of continuous cold stress, a sharp decline in the mitochondrial ATP synthesis rate was observed in control flies when they were assayed at low temperature. This change was associated with reduced survival capacity in control flies. In contrast, cold-acclimated flies exhibited high survival and maintained higher rates of mitochondrial ATP synthesis and coupling (i.e., higher RCRs). Adaptive changes due to cold acclimation observed in the whole organism were thus manifested in isolated mitochondria. Our observations suggest that cold tolerance is linked to the ability to maintain bioenergetics capacity under cold stress.
authors.affiliation: UMR CNRS 6553 ECOBIO, Université de Rennes 1, 263 avenue du Général-Leclerc, 35042, Rennes, France. Electronic address: herve.colinet@univ-rennes1.fr.
authors.forename: Hervé
authors.initials: H
authors.lastname: Colinet
authors.affiliation: UMR CNRS 6553 ECOBIO, Université de Rennes 1, 263 avenue du Général-Leclerc, 35042, Rennes, France.
authors.forename: David
authors.initials: D
authors.lastname: Renault
authors.affiliation: Laboratoire d'Ecologie des Hydrosystèmes Naturels et Anthropisés, UMR 5023, CNRS, Université de Lyon 1, 69622, Villeurbanne, France.
authors.forename: Damien
authors.initials: D
authors.lastname: Roussel
mesh_terms: D000064:Acclimatization; D000818:Animals; D003080:Cold Temperature; D004331:Drosophila melanogaster / Q000502:physiology*; D004734:Energy Metabolism; D005260:Female; D008928:Mitochondria / Q000378:metabolism*; D010101:Oxygen Consumption; D013312:Stress, Physiological
keywords: ATP; Acclimation; Cold stress; Fruit flies; Respiration