"Collaborative Research: Circadian Rhythms of Gene Expression in Cyanobacteria"

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Circadian rhythms are an adaptation of organisms to the regular daily change of their environment. Although much is known about the formal properties of circadian rhythms which allow them to synchronize to the daily light\dark cycles, almost nothing is known about how these rhythms work on a biochemical level. This project is two-fold. First, the simplest organism now known to express circadian rhythms will be used namely, prokaryotic cyanobacteria. Second, genetic tools will be used to analyze its mechanism. A reporter gene encoding a bioluminescence enzyme has been attached to an endogenous promoter. Not only does this construct make these cyanobacteria bioluminescent, the glow meets all of the salient criteria of circadian rhythmicity| This is the first "artificial" overt rhythm of a circadian clock yet described. This unique case of circadian gene expression will be exploited to: (1) identify by action spectroscopy the photoreceptor involved in the clock's entrainment; (2) analyze the control pathway by which the circadian clock regulates this "artificial rhythm; and (3) search for genes which are involved in the clock's central mechanism. Using a simple prokaryotic system should accelerate the identification of cellular mechanisms by which circadian oscillators operate. %%% Most organisms respond to the cycles of light and dark by physiological mechanisms that are not well understood. Plants respond to these cycles by turning on and off certain genes. By genetic manipulation these investigators have introduce a light emitting enzyme gene into a gene that is turned on by a daily light-dark cycle. Thus after light exposure these bacteria will begin to glow as the gene is turned on. This novel technique will allow the investigators to better understand the biochemical genetic mechanisms by which organisms respond to light-dark cycles.