Fig. P1.
Bimodal response of the galactose gene regulatory network (GAL) relies on dual positive feedback loops mediated by Gal1p and Gal3p. (A) GAL network in S. cerevisiae. This circuit contains numerous feedback loops mediated by Gal1p, Gal2p, Gal3p, and Gal80p. The galactose-activated forms of Gal1p and Gal3p are indicated by an asterisk (*), and promoters are represented by PX, where X is a particular gene. (B) Single-cell flow cytometry data of a GAL10 promoter fusion to a fluorescent protein (Venus) that reports GAL network activity in response to a wide range of galactose concentrations. The four panels include WT, GAL1 feedback deletion (GAL1Δ fb), GAL3 feedback deletion (GAL3Δ fb), and double GAL1 and GAL3 feedback deletion (GAL1Δ GAL3Δ fb). The dashed box indicates bimodal distributions, and each black circle represents the mean of the distribution classified using a Gaussian mixture model.