Synchronization of the Fungal and the Plant Circadian Clock by Light

Circadian clocks are endogenous time keeping devices that provide temporal control of physiology in accordance with predicted daily changes in the environment. Photoentrainment is the process that synchronizes circadian clocks-and thereby clock-controlled gene expression and physiology-to the environmental day/night cycles. Light is primarily detected by specialized photoreceptors that are coupled-directly or through other signaling components-to the rhythm-generating oscillator. As a consequence, the expression, the activity or the stability of oscillator components are altered, resulting in a change of phase and/or pace of the oscillator. In this review our present knowledge about light absorption/transduction and light-induced modifications of oscillator components in Neurospora crassa and Arabidopsis thaliana is summarized. These systems provide a basis for understanding the molecular mechanisms of entrainment in the fungal and plant circadian systems.