Abstract
Internal clocks driving rhythms of about a day (circadian) are ubiquitous in animals, allowing them to anticipate environmental changes. Genetic or environmental disturbances to circadian clocks or the rhythms they produce are commonly associated with illness, compromised performance or reduced survival. Nevertheless, some animals including Arctic mammals, open sea fish and social insects such as honeybees are active around-the-clock with no apparent ill effects. The mechanisms allowing this remarkable natural plasticity are unknown. We generated and validated a new and specific antibody against the clock protein PERIOD of the honeybee Apis mellifera (amPER) and used it to characterize the circadian network in the honeybee brain. We found many similarities to Drosophila melanogaster and other insects, suggesting common anatomical organization principles in the insect clock that have not been appreciated before. Time course analyses revealed strong daily oscillations in amPER levels in foragers, which show circadian rhythms, and also in nurses that do not, although the latter have attenuated oscillations in brain mRNA clock gene levels. The oscillations in nurses show that activity can be uncoupled from the circadian network and support the hypothesis that a ticking circadian clock is essential even in around-the-clock active animals in a constant physical environment.
Highlights
Circadian rhythms of about 24 h are ubiquitous in the metazoa and in some bacteria
Our findings provide the best description of the circadian network in the honeybee brain and set the stage for studies on the interplay between circadian clocks and complex behaviour
Antibodies against A. mellifera PERIOD protein were raised using a highly purified amPER protein in its native folded state recombinantly expressed in insect cell culture from forager brain cDNA
Summary
Circadian rhythms of about 24 h are ubiquitous in the metazoa and in some bacteria. It is thought that the clocks that generate these rhythms confer an adaptive benefit because they enable organisms to anticipate predictable day–night changes in their environment and align their physiology with these environmental cycles [1]. Studies with humans and model organisms reinforce this notion by showing that disturbing normal circadian rhythmicity by aberrant light–dark illumination or feeding regimes, or by disturbing clock anatomy or clock protein function, increases the risk of many diseases including cancer, metabolic disorders, mental disorders, heart attacks and infertility (reviewed in [2,3]). The molecular mechanism and many of the genes involved in rhythm generation are similar in animals as diverse as fruit flies and mice [4,5].
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