Abstract #69

Isolation and characterization of quiescent (G0) and non-quiescent cells from yeast stationary-phase cultures. Margaret Werner-Washburne¹, Chris Allen¹, Sabrina Büner³, Anthony Aragon¹, Osorio Meirelles⁵, Sushmita Roy⁴, Don Benn¹, Martin Veenhuis², Frank Madeo³. 1) Dept Biol, Univ New Mexico, Albuquerque, NM; 2) Laboratory of Eukaryotic Microbiology University of GroningenLaboratory of Eukaryotic Microbiology University of Groningen The Netherlands; 3) Institute for Molecular Biosciences University of Graz Graz, Austria; 4) Department of Computer Sciences University of New Mexico, Albuquerque, NM; 5) Department of Math and Statistics University of New Mexico Albuquerque, NM.
   We have isolated two cell fractions based on density from stationary-phase cultures. The heavier fraction is uniform, unbudded, refractive by phase-contrast microscopy, and extremely thermotolerant. Budding indices and DNA-content analysis revealed that these cells are synchronous upon re-entry into mitosis. Examination of FUN1-viability and colony-forming capacity indicates that these cells are viable for at least 4 weeks in YPD. Flow cytometry and microscopic analysis of bud scars revealed that over 90% of these cells are new daughters. We conclude that these cells are quiescent and probably in G0. In contrast, the upper fraction is heterogeneous, contains many budded cells that are dark by phase-contrast microscopy, and significantly less thermotolerant. These cells retain FUN1-viability and rapidly lose the ability to produce daughter cells. A high percentage of these cells become DHE-positive by 7 days post inoculation and about 50% exhibit markers of apoptosis or necrosis by day 14 post inoculation. Microarray analysis confirmed that these two yeast cell populations are extremely different. Quiescent cells accumulated transcripts involved in the response to oxidative stress. Non-quiescent cells accumulated transcripts encoding proteins involved in DNA recombination and TY element transposition, consistent with their apoptotic phenotype. The isolation of quiescent cells and the identification of the non-quiescent cell fraction that contains several interesting types of cells opens up new and important areas for study in yeast.

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