Temperature compensation of the circadian clock of Drosophila melanogaster

Basic data for this project

Description

Circadian clocks are self-sustained endogenous oscillators, able to control biological rhythms in a constant environment (i.e. constant darkness and temperature) with a period of ca. 24 h. They ensure the proper daily timing of behavioural and physiological events and must therefore be synchronized (or entrained) with the natural environmental cycles of light and temperature. Mammalian and insect circadian clocks are exquisitely sensitive to temperature, because small but regular temperature changes defining day and night result in robust clock synchronization. In contrast, the self-sustained 24 h period of circadian clocks is independent of its surrounding temperatures, i.e., circadian clocks are temperature compensated. This is a remarkable feature, because biological processes usually speed up with increasing temperatures. It is also an essential feature, because a clock that changes its speed according to the surrounding temperature would be useful as a thermometer, but not as an accurate timer. While there have been recent advances understanding the exquisite temperature sensitivity for synchronizing the circadian clock with temperature cycles, the buffering of the oscillator against ambient temperature changes (temperature compensation) is not understood on a genetic or molecular level. The apparent contradiction between exquisite temperature sensitivity on one hand and efficient buffering of the oscillator against fluctuations of ambient temperature also provides a compelling example of the general problem of sensory adaptation applicable to virtually all sensory systems. It is therefore important to fully understand the various interactions of temperature with circadian clocks on a molecular and mechanistic level. The current project aims to reveal the underlying mechanisms of temperature compensation using a combination of genetic and molecular approaches. A central objective will be to isolate novel genes involved in temperature compensation using an unbiased forward genetic screen. In parallel we will characterize novel molecular mechanisms underlying temperature compensation, focussing on temperature dependent regulation of nuclear export of clock proteins. Combined these two approaches are expected to critically increase our knowledge and understanding of one of the most fundamental characteristics of circadian clocks. In addition, integration of temperature compensation and synchronization principles, will potentially contribute to understanding the problem of sensory adaption.