Mechanisms Underlying the Complex Dynamics of Temperature Entrainment by a Circadian Clock

Abstract

Autonomously oscillating circadian clocks resonate with daily environmental (zeitgeber) rhythms to organize physiology around the solar day. While entrainment properties and mechanisms have been studied widely and in great detail for light-dark cycles, entrainment to daily temperature rhythms remains poorly understood despite that they are potent zeitgebers.Here we investigate the entrainment of the chronobiological model organism Neurospora crassa, subject to thermocycles of different periods and fractions of warm versus cold phases, mimicking seasonal variations. Depending on the properties of these thermocycles, regularly entrained rhythms, period-doubling (frequency demultiplication) but also irregular aperiodic behavior occurs. We demonstrate that the complex nonlinear phenomena of experimentally observed entrainment dynamics can be understood by molecular mathematical modeling.Abstract Figure

Circadian period is compensated for repressor protein turnover rates in single cells

“…they respond to zeitgebers. While several mechanisms have been proposed for temperature compensation [44][45][46] , less is known about how the clock is stabilized against changes in energy supply that affect the metabolic state and thus global reaction rates such as macromolecule assembly and turnover. [47][48][49] In this study, we exploit the natural heterogeneity of single cell clocks to discover fundamental principles for metabolic compensation of the circadian period without the need for genetic manipulation.…”