A wild species of budding yeast, Saccharomyces paradoxus, is more resistant to cold temperature stress than the domesticated species, Saccharomyces cerevisiae
Authors:
Chidinma Amakiri, Nicolette Harmon, Nicholas Rohacz, Katrina SherbinaMentors:
- Kam Dahlquist, Associate Professor of Biology, Loyola Marymount University
- Ben Fitzpatrick, Professor of Mathematics, Loyola Marymount University
The growth rate of a wild species of yeast, Saccharomyces paradoxus, was compared to the domesticated species, Saccharomyces cerevisiae, when both were subjected to different temperatures and inhibitory drugs. We found that S. paradoxus had a shorter doubling time than S. cerevisiae at both 30 and 13°C, and that S. paradoxus grew significantly faster at the cold temperature than was expected by its warm temperature growth rate. Furthermore, S. paradoxus was more resistant to the growth-inhibitory drugs, rapamycin and caffeine, than S. cerevisiae. Finally, we performed a DNA microarray experiment on S. paradoxus subjected to cold shock to determine the gene expression changes that occur during resistance to cold stress. S. paradoxus cells were grown to an OD600 of 0.2 at 30°C. Cells were harvested and then the remainder of the culture was transferred to a 13°C incubator. Cells were then harvested after 15, 30 and 60 minutes of cold shock. After 60 minutes of cold shock the cells were returned to 30°C for recovery; cells were harvested after 30 and 60 minutes of recovery. Total RNA was purified from the harvested cells. cDNA and then aRNA were synthesized, labeled, and hybridized to the microarray chips. Four replicates of the experiment were performed. A preliminary analysis of the data was carried out using software called STEM, which clusters genes with similar expression profiles and provides the Gene Ontology categories that belonged to genes in each cluster. The main cluster of genes that were up-regulated during cold shock and down-regulated during recovery were associated with ribosome biogenesis. This is similar to what is found in S. cerevisiae. Further analysis is needed to determine differences in gene expression between the two species of yeast.