2015 Annual Science Report
University of Montana, Missoula Reporting | JAN 2015 – DEC 2015
Project 8: Limits to Optimality in Adaptive Evolution
The goal of this project is to determine how the genetic makeup of an organism influences its future evolution. We have developed a tracking system that allows us to track the emergence of mutations that make an organism more fit in a certain environment – we will be deploying this system to track such emergences in yeast strains with slightly different genetic makeup. This will allow us to see how the genetic makeup influences the evolutionary process.
In the first year, we have made limited progress, because it took a while to recruit a postdoc to work on the project. However, I now have a postdoc in place who is working on the project, and we I expect us to make rapid progress. We have selected 3 adaptive lineages that were isolated from our previously published experimental evolution work (Levy et al, 2015, Nature 519, 181-186.). These lineages have been sequenced, and we have both presumptive gain of function and loss of function beneficial mutations, which affect either the Ras/Protein Kinase A signaling pathway, or the Tor signaling pathway. Each of these lineages has been backcrossed to the ancestral strain that contains a “landing pad”. These have then been sporulated, so that we have isolated individuals with both the beneficial mutations and a blank landing pad. The landing pad allow us to rebarcode each strain (~500,000 individual barcoded lineages per mutant), so that we can track the emergence of beneficial mutations as each mutant is independently experimentally evolved. Prior to starting the experimental evolutions, we will first perform pairwise fitness competitions between independent segregants of each lineage against a fluorescently marked ancestor strain, to unequivocally prove that as predicted, the mutations do provide a fitness benefit.