Molecular aspects of the Arabidopsis circadian clock

Abstract

Circadian rhythms are endogenous, self-sustaining and self-generating cycles of an approximately 24-h period that are present in all living systems that prepare organisms for periodic environmental changes of light and temperature. Although poor compared to animal systems, our understanding of the circadian system in plants has increased considerably in recent years. This review presents our current knowledge of the plant circadian system, focussing on that described for the model plant, Arabidopsis thaliana, upon which most of our information is based. The repertoire of proteins that play a crucial role in clock regulation, as well as the photoreceptors and signaltransduction pathways proposed to be involved in transmitting light information to synchronise the endogenous clock with the outside world are described. Finally, our current understanding of how the mechanisms by which the central oscillator controls the activity of the various clock controlled genes, the "hands of the clock", is briefly discussed.