Abstract #57

Evolution of Gene Expression in Experimentally Evolved Yeast. Maitreya Dunham, Cheryl Christianson, Dave Pai. Lewis-Sigler Inst, Princeton Univ, Princeton, NJ.
   Experimental evolution can be used to observe the response of genetic networks to perturbation by long-term nutrient-limited chemostat growth. We have evolved 30 yeast populations of varying genetic background (FY, CEN.PK, and RM11), ploidy (1N and 2N), and nutrient conditions (glucose-, sulfur-, and phosphate-limitation). Population samples and clones regrown to steady state were assayed for genome-wide gene expression using microarrays. Over hundreds of generations, patterns of gene expression changed remarkably. Changes were generally exclusive to the different nutrient limitations, implying that this approach parses out the appropriate metabolic pathways. Sulfur limitations all converged upon a single gene expression "solution" within 200 generations while several patterns were observed for glucose-limited cultures. Although the three strain backgrounds had quite different starting gene expression, the genes that changed during the evolutions were in general strain-independent. Haploids and diploids also behaved similarly with the exception of more large-scale genome rearrangements in the diploids than in the haploids. With the recent advent of whole-genome mutation detection methods, we hope to connect these gene expression changes to particular mutations. For example, a point mutation in TIM13 found in a sulfur-limited culture may be responsible for changes in gene expression of phospholipid-related genes.

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