A circadian clock in yeast

PhD ceremony: Ms. Z. Chen, 14.45 uur, Academiegebouw, Broerstraat 5, Groningen

Thesis: A circadian clock in yeast

Promotor(s): prof. M. Marrow

Faculty: Mathematics and Natural Sciences

Although circadian clocks are found widely in nature, they have been largely ignored in Saccharomyces cerevisiae. We looked for signatures of a circadian system in S. cerevisiae. We developed chemostat cultures to establish conditions that reveal characteristic clock properties as described in so many other species, thereby showing circadian timing in budding yeast. We monitored the oscillation of respiration in yeast in a fermentor. To evoke daily oscillations, temperature cycles were imposed on the cultures. We have investigated one readout - pH change in the media - to determine exactly what is regulated by a daily timer in yeast. The temperature cycle protocols reveal distinct processes in S. cerevisiae, namely entrainment and a damped free-running rhythm, that are consistent with a circadian timing mechanism.

To sum up, the work which is presented in this thesis reveals that there is a circadian system in budding yeast Saccharomyces cerevisiae. In this thesis I contribute to the progress in four areas:

1) Establishing conditions that support circadian rhythms in budding yeast S. cerevisiae.

2) Collect transcriptome and metabolome data on yeast under different circadian protocols.

3) Obtain information about the molecular mechanisms of circadian timing from the transcriptome and metabolome data in yeast.

4) Construct reporter (clock-regulated LUC) strains, which gives us a high throughput way to examine in vivo expression of (candidate) circadian genes.