Natural entrainment of the drosophila melanogaster circadian clock

In the laboratory, the circadian clock of Drosophila has been studied by analysing locomotor activity rhythms in either rectangular light-dark cycles in constant temperature or temperature cycles in constant light. In this way, the molecular components of the circadian clock have been characterised and their entrainment to the environment has been dissected. In nature, however, light-dark cycles and temperature cycles occur together and represent a dynamic environment. The aim of this work is to study the entrainment of D. melanogaster to natural conditions. The locomotor activity profile of wild-type flies in natural conditions has been described in detail. In particular, the position of the morning and evening components have been analysed with relation to the environment. It is found that temperature comprises the principal environmental cue that determines the timing of both morning and evening behaviour. Morning behaviour appears to be more responsive to the dynamic environment of the morning, apparently responding to light intensities as low as 0.0006 lux. Apart from wild-type flies, mutants for the canonical clock genes (per01, tim01, Clock jerk, per01tim01) as well as the output and input genes Pdf 01 and cry0also show temporally regulated behaviour in natural conditions, suggesting the presence in ‘clockless’ flies of a residual timing mechanism. This work has revealed that clockless mutants can affect different parts of the circadian behavioural profile, and that GAL4 mediated disruption of the network of circadian neurons in the brain, can have unanticipated phenotypes. Preliminary molecular work has also revealed that the effect of light is dominant over that of temperature on the cycling of TIM. A de-coupling of this cycling among different neuronal groups in the brain is observed in natural conditions. Finally, an antibody has been generated against CRY, the dedicated circadian photoreceptor.