title: Regulatory mechanisms of metabolic flexibility in the dark-eyed junco (Junco hyemalis).
abstract: Small temperate birds reversibly modify their aerobic performance to maintain thermoregulatory homeostasis under seasonally changing environmental conditions and these physiological adjustments may be attributable to changes in the expression of genes in the underlying regulatory networks. Here, we report the results of an experimental procedure designed to gain insight into the fundamental mechanisms of metabolic flexibility in the dark-eyed junco (Junco hyemalis). We combined genomic transcriptional profiles with measures of metabolic enzyme activities and whole-animal thermogenic performance from juncos exposed to four 6-week acclimation treatments that varied in temperature (cold, 3°C; warm, 24°C) and photoperiod (short day, 8 h light:16 h dark; long day, 16 h light:8 h dark). Cold-acclimated birds increased thermogenic capacity compared with warm-acclimated birds, and this enhanced performance was associated with upregulation of genes involved in muscle hypertrophy, angiogenesis, and lipid transport and oxidation, as well as with catabolic enzyme activities. These physiological changes occurred over ecologically relevant timescales, suggesting that birds make regulatory adjustments to interacting, hierarchical pathways in order to seasonally enhance thermogenic capacity.
authors.affiliation: Department of Animal Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA stager2@illinois.edu.
authors.forename: Maria
authors.initials: M
authors.lastname: Stager
authors.affiliation: Department of Biology, University of South Dakota, Vermillion, SD 57069, USA.
authors.forename: David L
authors.initials: DL
authors.lastname: Swanson
authors.affiliation: Department of Animal Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
authors.forename: Zachary A
authors.initials: ZA
authors.lastname: Cheviron
mesh_terms: D000064:Acclimatization; D000818:Animals; D001833:Body Temperature Regulation; D004734:Energy Metabolism; D005786:Gene Expression Regulation; D018482:Muscle, Skeletal / Q000033:anatomy & histology; D017440:Photoperiod; D012621:Seasons; D020308:Songbirds / Q000033:anatomy & histology / Q000378:metabolism*; D013696:Temperature
keywords: Phenotypic flexibility; Seasonal adjustments; Transcriptomics; Winter acclimatization