BP001-002: The genomic landscape of compensatory evolution

Adaptive evolution is generally assumed to progress through the accumulation of beneficial mutations. However, deleterious mutations may also have an important role by promoting adaptive genetic changes that are otherwise inaccessible. Here we study the capacity of the baker’s yeast genome to compensate the complete loss of genes during evolution, and explore the long-term consequences of this process. We initiated laboratory evolutionary experiments with over 180 haploid yeast genotypes, all of which initially displayed slow growth due to the deletion of a single gene. Compensatory adaptation was rapid and pervasive, and it promoted the genomic divergence of parallel evolving populations. The accumulated mutations did not restore wild type genomic expression states and generated diverse growth phenotypes across environments. Taken together, gene loss initiates genomic changes that can influence evolutionary potential upon environmental change. Evolved yeast-lines were generated by growing strains for 400 doublings during 104 days on YPD medium in 96 wells plates, 8 evolved lines were selected for microarray analysis. Two independent colonies of the wild type control, evolved and corresponding ancestor knock-out strains were grown to early midlog and used for transcription profiling by dual channel array against a common reference.