Comparative proteome analysis of honey bee workers between overwintering and brood-rearing seasons

In winter, honey bees thermoregulate their hives to survive cold temperatures and maintain their physiological activity, without becoming completely dormant. At this time, nurses and foragers are not distinguishable. In late winter or early spring, as the brood rearing re-initiates, the division of labor resumes among the workers born in the fall. To understand the overall physiological changes of honey bee workers from late winter (end of overwintering) to early spring (beginning of brood rearing), we collected honey bees in January and February and compared their protein expression profiles. Among the 50 and 85 proteins showing greater than two-fold differences in expression levels in the head and abdomen, respectively, 20 proteins with relatively large differences in expression level between the months were selected and identified. Most proteins were more abundantly expressed in January than February and were mainly involved in nutrient storage, energy metabolism, and biosynthesis pathways in both the head and abdomen. This finding suggested that overwintering honey bees require large energy storage and metabolize stored nutrition to generate high cellular energy for thermoregulation of their hive without diapause and/or to prepare for the initiation of brood rearing in January.