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Vol. 19, Issue 3, 1271-1280, March 2008

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Characterization of Differentiated Quiescent and Nonquiescent Cells in Yeast Stationary-Phase Cultures

Anthony D. Aragon^*, Angelina L. Rodriguez^*, Osorio Meirelles, Sushmita Roy, George S. Davidson, Phillip H. Tapia^*, Chris Allen^||, Ray Joe^*, Don Benn^*, and Margaret Werner-Washburne^*

Departments of *Biology, Math and Statistics, Computer Science, University of New Mexico, Albuquerque, NM 87131; Sandia National Laboratories, Albuquerque NM 87185; and ^||Department of Cytometry, University of New Mexico Health Sciences Center, Albuquerque, NM 87131

Submitted July 13, 2007; Revised December 19, 2007; Accepted January 4, 2008
Monitoring Editor: Thomas Fox

Cells in glucose-limited Saccharomyces cerevisiae cultures differentiate into quiescent (Q) and nonquiescent (NQ) fractions before entering stationary phase. To understand this differentiation, Q and NQ cells from 101 deletion-mutant strains were tested for viability and reproductive capacity. Eleven mutants that affected one or both phenotypes in Q or NQ fractions were identified. NQ fractions exhibit a high level of petite colonies, and nine mutants affecting this phenotype were identified. Microarray analysis revealed >1300 mRNAs distinguished Q from NQ fractions. Q cell-specific mRNAs encode proteins involved in membrane maintenance, oxidative stress response, and signal transduction. NQ-cell mRNAs, consistent with apoptosis in these cells, encode proteins involved in Ty-element transposition and DNA recombination. More than 2000 protease-released mRNAs were identified only in Q cells, consistent with these cells being physiologically poised to respond to environmental changes. Our results indicate that Q and NQ cells differentiate significantly, with Q cells providing genomic stability and NQ cells providing nutrients to Q cells and a regular source of genetic diversity through mutation and transposition. These studies are relevant to chronological aging, cell cycle, and genome evolution, and they provide insight into complex responses that even simple organisms have to starvation.

Address correspondence to: Dr. Margaret Werner-Wasburne (maggieww{at}unm.edu)

Abbreviations used: NQ, nonquiescent; Q, quiescent; SP, stationary phase.