Integration of input signals into the gene network in the plant circadian clock

Abstract

The circadian clock, an endogenous timekeeping mechanism, allows organisms to anticipate and prepare for daily environmental changes and increase their fitness in changing environments. Circadian clocks in plants, as in animals and insects, consist of a gene network forming multiple interlocking transcriptional feedback loops. To synchronize internal biological rhythms with surrounding environments, circadian clocks must be precisely adjusted by environmental cues. Light and temperature are well known as two major input signals for the plant circadian clock. In addition, it is emerging that nutritional status is also a crucial input for the plant clock. Although numerous studies have revealed that these external cues can entrain the circadian rhythms by affecting the transcript levels of several clock genes, little is known about how input signals are integrated into the core clock oscillator and reset the circadian rhythms at the molecular level. Recently, several studies have demonstrated that each of the input signals mutually influences the others, and that there are interactions among input signals. In this review, we summarize recent findings regarding the interactions among input signals and the integration of input signals into the circadian clocks in plants.