Biology ETDs

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Yeast cells in stationary phase cultures, after several days growth in rich, glucose-based medium (YPD), are separable by density-gradient centrifugation into two fractions. The heavier, quiescent cells are mostly virgin daughters whereas the less-dense, non-quiescent cells, are a typical mixture of daughters to aged cells. Quiescent cells can also be separated based on expression of specific GFP-tagged proteins, including many that are localized to the mitochodria. To ask the question, what genes are required for this differentiation process, we used a combination of the diploid, homozygous yeast deletion set, the heterozygous deletion set (carrying one deleted 'essential' gene) and a third set designed to reduce mRNA abundance of a number of 'essential' genes. Samples from the cultures just prior to the diauxic shift (just prior to glucose exhaustion), stationary phase, and isolated quiescent (Q) and nonquiescent (NQ) cells were harvested and technical and biological replicates analyzed by microarray analysis. The results showed that deletions in more than 500 genes resulted in 2-fold or greater reduction in Q-cell formation. Thus, almost 10% of genes in the yeast genome were important for Q-cell formation. When mutants with a 2-fold in Q vs all other samples were compared, 411 genes were identified that were important for Q cells vs DS, NQ, and SP. These genes encoded proteins involved in mitochondrial function, protein localization, and vesicle transport. We concluded from these results that differentiation of quiescent cells requires a major cellular commitment and that the major functions required are similar to those identified by proteomic and transcriptomic analysis of Q cells done previously in our laboratory, furthering understanding of cell differentiation.




yeast, Saccharomyces cerevisiae, quiescence, cell differentiation

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Level of Degree


Department Name

UNM Biology Department

First Committee Member (Chair)

Natvig, Don

Second Committee Member

Northup, Diana