Genetic properties underlying transcriptional plasticity and evolvability in E. coli

The rate and direction of phenotypic evolution depends on the availability of phenotypic variants induced either genetically or environmentally for selection act upon. Theoretical suggest that genetic interactions between genes governing phenotypes could explain how the bias in phenotypic variability arises. However, it remains unknown whether the phenotypic variability is explained by real known genetic interactions as expected. To address this question, we analyzed transcriptional variability in a model microorganism, Escherichia coli, in response to different environmental and genetic perturbations. Thanks to the rich knowledge of the genetic interactions of E. coli, we identified common genetic properties that potentially affect transcriptional variability in both environmental and genetic causes. These empirical evidences support the relevance of the genetic interactions to shape phenotypic variability that is shared by different perturbations. Our results provide a mechanistic insight into how evolution learns from past environments to generalize to new environments. Transcriptomic profiles of the MA lineages (12 isolates and two founders) of E. coli were analized by DNA microarrays. Two biological replicates of each founder were also analyzed. A total of 16 samples were analyzed. All samples were cultured in LB and total RNA was extracted from the cells in the exponential growth phase.