Pleiotropy allows recovery of phenotypic plasticity in constant environments

Phenotypic plasticity confers a fitness advantage to an organism by tailoring phenotype to environmental circumstances. The extent to which phenotypic plasticity emerges as an adaptive response is still unknown, however it is predicted that the emergence and maintenance of phenotypic plasticity occurs only during evolution in fluctuating environments. Interestingly, experimental studies have shown that phenotypic plasticity can be preserved for several generations during evolution in a constant environment. Here, we evolve a mutant strain of Saccharomyces cerevisiae that has reduced plasticity in a constant and fluctuating environment. Subsequently we compared the adaptive response of the evolved cell, both at the phenotype and genotype level. As predicted by current theory, we find that evolution in a fluctuating environment results in a recovery of phenotypic plasticity. Surprisingly, evolution in a constant environment can lead to a similar recovery of plasticity due to a pleiotropic coupling of different traits. Thus, plasticity can emerge in both fluctuating and constant environments and its prevalence may mainly be determined by network structure. In addition, pleiotropic interactions may be an important structural component of biological networks that can facilitate the recovery of phenotypic plasticity without the requirement to continuously encounter environmental fluctuations.