Stability of the Synechococcus elongatus PCC 7942 circadian clock under directed anti-phase expression of the kai genes.

The kaiA, kaiB and kaiC genes encode the core components of the cyanobacterial circadian clock in Synechococcus elongatus PCC 7942. Rhythmic expression patterns of kaiA and of the kaiBC operon normally peak in synchrony. In some mutants the relative timing of peaks (phase relationship) between these transcription units is altered, but circadian rhythms persist robustly.

PsfR, a factor that stimulates psbAI expression in the cyanobacterium Synechococcus elongatus PCC 7942.

In this paper a gene (psfR) is reported that regulates psbAI activity in Synechococcus elongatus, a unicellular photoautotrophic cyanobacterium that carries out oxygenic (plant-type) photosynthesis and exhibits global circadian regulation of gene expression. In S. elongatus, a family of three psbA genes encodes the D1 protein of the photosystem II reaction centre.

Cyanobacterial circadian clocks--timing is everything.

For more than three billion years, the organisms on this planet have known, like Little Orphan Annie, that "The sun'll come out tomorrow", and many have honed their biochemistry to exploit this knowledge. The cyanobacteria have had ample time to fashion a suitable timepiece, as they are among the oldest inhabitants of the earth. For these organisms, light is food, and it is a nutrient that shows up at the same time every day.