Genome sequecing of yeast strain evolved under high glucose

A population of Saccharomyces cerevisiae was cultured for approximately 450 generations in the presence of high glucose to select for genetic variants. This experiment allows for a controlled model of adaptive evolution under natural selection. Using the parental strain BY4741 as the starting population, an evolved culture was obtained after continuous aerobic growth in a glucose-high medium for approximately 450 generations. After the evolution period three single colony isolates were selected for analysis. Next-generation Ion Torrent sequencing was used to evaluate genetic changes. Greater than 100 deletion/insertion changes were found with approximately half of these effecting genes. Additionally, over 180 single-nucleotide polymorphisms (SNPs) were identified with more than one quarter of these resulting in a non-synonymous mutation. Affymetrix DNA microarrays and RNseq analysis were used to determine differences in gene expression in the evolved strains compared to the parental strain. It was established that approximately 900 genes demonstrated significantly altered expression in the evolved strains relative to the parental strain. Many of these genes showed similar alterations in their expression in all three evolved strains. Interestingly, genes with altered expression in the three evolved strains included genes with a role in the TCA cycle. Overall these results are consistent with the physiological observations of decreased ethanol production and suggest that the underlying metabolism switched from fermentation to respiration during aerobic growth.

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