FIGURE 1. PHO5 promoter variants and quantitative expression behaviour.

a, Schematic of all PHO5 promoter variants controlling expression of yeGFP1. Large grey ovals represent nucleosomes, red triangles the high-affinity Pho4 motif (CACGTGg), blue ovals the low-affinity Pho4 motif (CACGTTt), and X the motif ablations. b, Physiological transcriptional response to extracellular inorganic phosphate (P_i) measured by flow cytometry. Data points represent median steady-state expression levels normalized to the median observed in P_i starvation. Error bars represent interquartile ranges, which were observed to encompass the medians of at least three independent measurements. c, Induction kinetics in P_i starvation. Data points represent median fluorescence levels scaled between the promoter-specific expression minimum at 0 h and maximum at 7 h. For b and c, red traces designate variants with an exposed high-affinity site, and blue traces variants with an exposed low-affinity site.