Figure Legeneds.
Figure 1. X-gal phenotype and lacI mutations in focal clones. A representative colony of each clone grown on TGX indicator plates is shown at left. All mutations across evolved clones were either a 4 bp insertion or deletion frameshift mutation in a mutational hotspot region of lacI (box at top). Only the insertion is shown for the ancestor lacI -, but the deletion was also assessed and had the same fitness effect and X-gal phenotype.
Figure 2. Fitness effect of lacI- in the ancestor and evolved genetic backgrounds measured in minimal glucose (purple symbols) and lactose (green symbols) environments. Asterisks indicate clones with significantly different lacI - fitness effect when compared to the effect in the ancestor (Dunnett’s test, P < 0.05). Symbols and error bars indicate mean and standard error of at least 10 (in the glucose environment) or three (in the lactose environment) replicate fitness estimates. Note that error bars are smaller than symbols for many of the glucose fitness estimates. The dashed lines represent the fitness effect of lacI - in the ancestor in glucose (dashes) and lactose (dots). Evolution environments are shown directly above clone names which denotes the population a clone was selected from (“Anc” indicates the ancestor). In the glucose environment, one clone had a significantly higher fitness than the ancestor indicating that compensatory mutations are alleviating the cost of lacI - in glucose.
Figure 3. Fitness effect of lacI- in ancestor and evolved clones measured in glucose and lactose environments. Symbols shapes indicate the evolution environment or genotype of each clone. The ancestral measurements (circle) indicates the expectation if there were no epistatic interactions between lacI - and other mutations in the evolved background.
Figure 4. Plac-GFP reporter expression of lacI+ and lacI- clones in glucose and lactose. The symbols and colors indicate the genetic background and evolution environment of each clone. The X-axis shows the genotype and assay environment that Plac- GFP expression was measured in. Each measurement is the average of the median expression values of independent replicates (n = 14 in glucose and n = 4 in lactose). Error bars show standard error of the mean (note that error bars are generally covered by symbols in the glucose environment assays).
Figure 5. Relationship between lac expression andlacI- fitness effect. Symbols indicate the mean fitness effect and lac -reporter expression of the ancestor and evolved clones as indicated in panel A. A , expression and fitness estimates measured in the glucose environment. B , expression and fitness estimates measured in the lactose environment.