Picking out parallels: plant circadian clocks in context

Molecular models have been described for the circadian clocks of representatives of several different taxa. Much of the work on the plant circadian system has been carried out using the thale cress,Arabidopsis thaliana, as a model. We discuss the roles of genes implicated in the plant circadian system, with special emphasis onArabidopsis. Plants have an endogenous clock that regulates many aspects of circadian and photoperiodic behaviour. Despite the discovery of components that resemble those involved in the clocks of animals or fungi, no coherent model of the plant clock has yet been proposed. In this review, we aim to provide an overview of studies of theArabidopsiscircadian system. We shall compare these with results from different taxa and discuss them in the context of what is known about clocks in other organisms.