Resource presentation dictates genetic and phenotypic adaptation in yeast.

Abstract

Environments shape adaptive trajectories of populations, often leading to adaptive parallelism in identical, and divergence in different environments. However, how does the likelihood of these possibilities change with minute changes in the environment? In this study, we evolve Saccharomyces cerevisiae in environments which only differed in how sugar source is presented to the population. In one set of populations, carbon was presented as a mixture of glucose-galactose, and in the other, as melibiose, a glucose-galactose disaccharide. Since the two environments only differ in how the two monosaccharides are packaged, we call these environments "synonymous". Our results show that subtle changes in environments change the targets of selection between the two sets of evolved populations. However, despite different adaptive responses, pleiotropic effects of adaptation are largely predictable. Genome sequencing results demonstrate that small changes in the environment also strongly dictates the genetic basis of adaptation.