Mutant1

Cells in glucose-limited Saccharomyces cerevisiae cultures differentiate into quiescent (Q) and non-quiescent (NQ) fractions prior to entering stationary phase. To identify genes involved in this differentiation, Q and NQ cells from 101 deletion-mutant strains were tested for viability and reproductive capacity. Twenty-one mutants were identified, including 7 that affected reproductive capacity of both cell types. Thirteen affected only Q or NQ cells, indicating significant differentiation of these cell types. doa4 strains, lacking ubiquitin hydrolase, affected viability and reproductive capacity in both cell types. More than 1300 mRNAs differentiating Q and NQ cell fractions were identified by microarray analysis. Gene-ontology analysis of Q-cell mRNAs showed significant increases in protein-encoding mRNAs involved in membrane maintenance, oxidative stress response, and signal transduction. NQ-cell mRNAs encode proteins involved in Ty-element transposition and DNA recombination, consistent with apoptosis in these cells. Consistent with preparation for rapid response to environmental stimuli, approximately 2000 protease-labile mRNAs were identified in Q cells. The differentiation of these cell types and the ability of genes to selectively affect the survival of Q or NQ cells in yeast are relevant to chronological aging, cell-cycle, genome-evolution, and stem-cell research and provides insight into complex responses that even simple organisms have to starvation. Keywords: Cell type comparison Yeast deletion mutants (BY4742 background) were grown to stationary-phase (7 days) and then separted into Q and NQ cells using Percoll density gradients. Microarrays were carried out on these different cell fractions.