title: Chronic dietary salt stress mitigates hyperkalemia and facilitates chill coma recovery in Drosophila melanogaster.
abstract: Chill susceptible insects like Drosophila lose the ability to regulate water and ion homeostasis at low temperatures. This loss of hemolymph ion and water balance drives a hyperkalemic state that depolarizes cells, causing cellular injury and death. The ability to maintain ion homeostasis at low temperatures and/or recover ion homeostasis upon rewarming is closely related to insect cold tolerance. We thus hypothesized that changes to organismal ion balance, which can be achieved in Drosophila through dietary salt loading, could alter whole animal cold tolerance phenotypes. We put Drosophila melanogaster in the presence of diets highly enriched in NaCl, KCl, xylitol (an osmotic control) or sucrose (a dietary supplement known to impact cold tolerance) for 24h and confirmed that they consumed the novel food. Independently of their osmotic effects, NaCl, KCl, and sucrose supplementation all improved the ability of flies to maintain K+balance in the cold, which allowed for faster recovery from chill coma after 6h at 0°C. These supplements, however, also slightly increased the CTminand had little impact on survival rates following chronic cold stress (24h at 0°C), suggesting that the effect of diet on cold tolerance depends on the measure of cold tolerance assessed. In contrast to prolonged salt stress, brief feeding (1.5h) on diets high in salt slowed coma recovery, suggesting that the long-term effects of NaCl and KCl on chilling tolerance result from phenotypic plasticity, induced in response to a salty diet, rather than simply the presence of the diet in the gut lumen.
authors.affiliation: Department of Biology, York University, 4700 Keele St., Toronto M3J 1P3, Canada.
authors.forename: Gil Y
authors.initials: GY
authors.lastname: Yerushalmi
authors.affiliation: Department of Biology, York University, 4700 Keele St., Toronto M3J 1P3, Canada.
authors.forename: Lidiya
authors.initials: L
authors.lastname: Misyura
authors.affiliation: Department of Biology, York University, 4700 Keele St., Toronto M3J 1P3, Canada.
authors.forename: Andrew
authors.initials: A
authors.lastname: Donini
authors.affiliation: Department of Biology, York University, 4700 Keele St., Toronto M3J 1P3, Canada. Electronic address: macmilla@yorku.ca.
authors.forename: Heath A
authors.initials: HA
authors.lastname: MacMillan
mesh_terms: D000821:Animal Feed / Q000032:analysis; D000818:Animals; D003080:Cold Temperature / Q000009:adverse effects*; D058639:Cold-Shock Response; D004032:Diet; D019587:Dietary Supplements / Q000032:analysis; D004331:Drosophila melanogaster / Q000187:drug effects / Q000502:physiology*; D005260:Female; D011189:Potassium Chloride / Q000378:metabolism*; D012965:Sodium Chloride / Q000378:metabolism*; D014882:Water-Electrolyte Balance
chemical_list: D012965:Sodium Chloride; D011189:Potassium Chloride
keywords: Chill coma recovery; Cold tolerance; Ion balance; Salt stress