Synthetic control of Dal80p levels tunes noise in Gdh1p expression. (A) Schematic of the genetic construct for building the galactose-tunable Dal80p system. A region 500 nt upstream of the DAL80 coding region was replaced through homologous recombination with a construct encoding the GAL1-10 promoter and a selectable LEU2 marker. (B) DAL80 transcript levels vary linearly with exogenous galactose in the engineered strain. Relative DAL80 transcript levels were measured by qRT-PCR and are shown relative to wildtype DAL80 transcript levels. (C) Gdh1p abundance does not change as Dal80p levels change. The percent galactose added to the culture is shown in parentheses. (D) Noise in Gdh1p expression changes as Dal80p levels change. Populations of the engineered strain show higher noise at low Dal80p levels (low galactose concentrations) and lower noise with increasing Dal80p (increasing galactose concentrations). Percent galactose added to the culture is shown in parentheses.