Bimodal gene expression by genetically identical cells is a pervasive feature of signaling networks, and has been suggested to allow organisms to hedge their "bets" in uncertain conditions. In the galactose-utilization (GAL) pathway of Saccharomyces cerevisiae, gene induction is unimodal or bimodal depending on natural genetic variation and pre-induction conditions. Here, we find that this variation in modality arises from regulation of two features of the pathway response: the fraction of cells that show induction, and their level of expression. GAL3, the galactose sensor, controls the fraction of induced cells, and titrating its expression is sufficient to control modality; moreover, all the observed differences in modality between different pre-induction conditions and amongst natural isolates can be explained by changes in GAL3's regulation and activity. The ability to switch modality by tuning the activity of a single protein may allow rapid adaptation of bet hedging to maximize fitness in complex environments.

Dataset 1 GAL induction of natural isolates in galactose titration experiments (Figure 1B, Figure S1). Contains .fcs files of raw flow cytometry data.

Dataset 2 GAL induction of natural isolates in glucose titrations with a constant galactose concentration (Figure 1C-D, Figure 4A-E, Figure S2). Contains .fcs files of raw flow cytometry data.

Dataset 3 GAL induction of a S288C mig1Δ strain in glucose titrations with a constant galactose concentration (Figure 4F). Contains .fcs files of raw flow cytometry data.

Dataset 4 GAL induction of natural isolates in glucose titrations with a constant galactose concentration after growth in different carbon source (Figure 1D, Figure 5, Figure S11-12). Contains .fcs files of raw flow cytometry data.

Dataset 5 Steady-state expression of S288C GAL promoters in different carbon sources (Figure 6A). Contains .fcs files of raw flow cytometry data.

Dataset 6 Expression of the S288C GAL3 promoter in different carbon sources and different natural isolates (Figure 6B). Contains .fcs files of raw flow cytometry data.

Dataset 7 GAL induction of S288C with inducible GAL3 expression in glucose titrations with a constant galactose concentration after growth in raffinose and mannose and quantification of inducible expression after pre-induction growth with a TetO7pr-YFP strain (Figure 6C). Contains .fcs files of raw flow cytometry data.

Dataset 8 GAL induction of a S288C gal3Δ strain with inducible GAL3-mCherry expression in glucose titrations with a constant galactose concentration after growth in different carbon sources (Figure 6D). Contains .fcs files of raw flow cytometry data.

Dataset 9 GAL3 levels of the S288C gal3Δ strain with inducible GAL3-mCherry expression (see Dataset 8) before the switch to glucose and galactose medium (Figure 6D). Contains .tif files of raw flow microscopy data.

Dataset 10 GAL induction of GAL3 allele swap strains in glucose titrations with a constant galactose concentration (Figure 7, Figure S13). Contains .fcs files of raw flow cytometry data.