In a previous study, three determinants of fitness were identified as mutant alleles (each designated "e") that arose in yeast populations propagated in divergent environments. In a low-glucose environment, MDS3e and MKT1e interacted positively to confer a fitness advantage. PMA1e from a high-salt environment interacted negatively with MKT1e in low glucose, indicating a mechanism of reproductive isolation. In this thesis, I demonstrated that the negative interaction between PMA1e and MKT1e is mediated by alteration in intracellular pH and likely by a delay of the cell division cycle, while the positive interaction between MDS3e and MKT1e is mediated by changes in gene expression affecting glucose transporter genes. I also confirmed the evolutionary significance of the positive interaction by showing that an MDS3e genetic background is required for the recapitulation of the MKT1e mutation. Collectively, these results illustrate how epistasis can play a central role in both adaptation and speciation.
| Identifer | oai:union.ndltd.org:TORONTO/oai:tspace.library.utoronto.ca:1807/31380 |
| Date | 19 December 2011 |
| Creators | Parreiras, Lucas Salera |
| Contributors | Anderson, James, Kohn, Linda M. |
| Source Sets | University of Toronto |
| Language | en_ca |
| Detected Language | English |
| Type | Thesis |
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