Abstract
Physiological rhythms with a cycle of about 24 hour period are called circadian rhythms. The rhythms share "robustness of period" against environmental fluctuations. Specifically, the robustness for temperature perturbations is called "temperature compensation".
An empirical fact about temperature compensation is known; the range of temperature where temperature compensation works is identical to the range of physiological temperature. If ambient temperature is out of the range, circadian rhythms can no longer be observed. Although many reports have mentioned this phenomenon, it is unclear if temperature stimulus affect circadian clock directly or through indirect paths, e.g. metabolic changes.
In this presentation, we will focus on why circadian rhythms can not be observed at low temperature. The circadian clock of cyanobacteria, the simplest organism that shows circadian rhythms, has been well examined. KaiC phosphorylation rhythms had been specified as the central oscillator generating rhythms and even reconstituted in vitro. Combining behavior of the chemical oscillator and knowledge of bifurcation theory, we will present a scenario of circadian arrhythmia at low temperature.
