Junco hyemalis Transcriptome or Gene expression

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 (SD=8h light:16h dark; LD=16h light:8h dark). Cold-acclimated birds increased thermogenic capacity compared to warm-acclimated birds, and this enhanced performance was associated with upregulation of genes involved in lipid transport and oxidation, and 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.