Temperature-Compensation in Biological Clocks: Models and Experiments

Abstract

In order to function as physiological clocks, circadian (and certain ultradian) rhythms contain homeostatic mechanisms which compensate for external temperature variations and other environmental influences. In this paper a theory for temperature-compensation and general homeostasis for physiological clocks is presented and compared with experimental findings. Results obtained from different organisms indicate that circadian pacemakers are based on one or several negative feedback loops where protein products of clock genes act as inhibitors of their own transcription. We have simulated the occurrence of temperature-compensation by using a simple reaction-kinetic model (the so-called Goodwin oscillator) which mimicks the negative feedback loop of a circadian pacemaker. The comparison between simulation calculations and experiments ofNeurospora andDrosophila clock mutants shows that both period length and temperature-compensation appear closely connected through the stability/degradation rate of clock proteins.