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No doubt you have noticed that many organisms have daily rhythms in behavior and/or physiology (for example, you yourself may wake up at the same time each day even when you don't set an alarm). Many of these daily rhythms are controlled by an internal circadian clock and can continue even in the absence of environmental cues. These circadian (Latin for 'about a day') rhythms are widespread throughout nature. Circadian rhythms are found in some prokaryotes (cyanobacteria, photosynthetic algae) and in most eukaryotes. Higher plants also have circadian rhythms, which influence important physiological and developmental processes such as photosynthesis and the transition from vegetative to reproductive growth. Circadian rhythms are thought to provide an adaptive advantage by ensuring that particular clock outputs occur at the most appropriate time of day, or phase.

In all model organisms described thus far, circadian rhythms are the product of cell-autonomous oscillators, or clocks. Although circadian rhythms persist in the absence of environmental input, they can be reset by changes in environmental factors such as light and temperature.

Thus the circadian system can be roughly divided into three parts: clock outputs that are generated by the central oscillator, the oscillator itself, and the signal transduction pathways that can reset the central oscillator. However, these divisions are somewhat artificial; for example, clock outputs can feed back to modulate the effect of environmental stimuli on the central oscillator.

We are interested in understanding both the organization of the central oscillator and the types of physiological processes that it regulates in higher plants. Using Arabidopsis thaliana as our model organism, we are taking a variety of approaches to address these questions. We are using genomics, forward and reverse genetics, molecular biology, bioinformatics, and biochemistry to address fundamental questions in circadian biology.