In the laboratory, yeast is usually grown in the presence of high glucose, and lab yeast is adapted for those conditions. If strains more typical of wild yeast are maintained under conditions with few nutrients, they will show a synchronous cycle of alternating respiratory and glycolytic metabolism. Cell division is confined to the glycolytic (or reductive) phase. Chen et al. hypothesized that this occurs to prevent replication from taking place in an oxidizing environment, which could cause mutations. When cells were forced to divide during the oxidizing phase of the metabolic cycle by introducing one of several cell cycle mutations or treating with H2O2, an increased level of DNA mutation was indeed observed. In addition, a mutation in a DNA checkpoint kinase that links the cell and circadian cycles in other fungi disrupts cell synchrony, suggesting parallels between the metabolic and circadian cycles.
Z. Chen, E. A. Odstrcil, B. P. Tu, S. L. McKnight, Restriction of DNA replication to the reductive phase of the metabolic cycle protects genome integrity. Science 316, 1916-1919 (2007). [Abstract] [Full Text]