Saccharomyces cerevisiae whi2 Mutants in Stationary Phase Retain the Properties of Exponentially Growing Cells

Summary: Stationary phase cultures of whi2 mutants of Saccharomyces cerevisiae were tested to discover whether they had undergone the changes which wild-type cells show in response to nutrient deprivation. The sensitivity to a 52°C heat shock, nystatin treatment and Zymolyase digestion of the cell wall was determined in isogenic WHI2+ and whi2 strains in both exponential and stationary growth phases. In each case, WH12+ cells become more resistant to these treatments in stationary phase but whi2 cells in stationary phase retained the sensitivity of exponential cultures. In addition, glycogen accumulation was reduced in the whi2 mutant, and DAPI fluorescent staining of the nuclei revealed that nuclear cycle arrest did not occur in G1, but at a minimum of three different phases of the cell cycle. We conclude that under the conditions of deprivation which occur in stationary phase, whi2 mutants retain the properties of exponentially growing cells.