The circadian clock of the Drosophila melanogaster eye regulates morning anticipation and is selectively linked to the circadian neuronal network

Abstract

How multiple circadian clocks within the circadian neuronal network (CNN) converge to regulate behaviour remains elusive. Circadian behaviour is an organism’s response to environmental cues (e.g., day/night cycles), regulated by the circadian clock, a ~24-h transcription/translation negative feedback loop. Using Drosophila melanogaster, we aim to understand how the eye communicates to the CNN to regulate behaviour. Each hemisphere of the fly brain contains nine clusters of circadian neurons. Various aspects of circadian behaviour are regulated by the different neuronal clusters, suggesting that they must cooperate to regulate coherent behaviour. Given that light is the strongest environmental cue for circadian entrainment, and the visual system is an input point for light in flies and in mammals, we modified the circadian clock of the eye and measured clock oscillations in individual neuronal clusters to determine which brain clocks are linked to the eye clock. Our results demonstrate that the eye clock regulates morning anticipation behaviour and communicates to two neuronal clusters of the CNN. Our study suggests that the brain clocks use different neuronal pathways to communicate and regulate various aspects of behaviour.