1. Most promoters preserve their relative activity levels across conditions.
Most promoters preserve their relative activity levels across conditions. (A) The promoter activity in glucose (x axis) and glucose lacking amino acids (y axis) is shown. Black lines represent three standard deviations of experimental noise around a robust linear fit to the data (cyan line) (Materials and methods). The slope of the robust linear fit represents the global scaling factor between the two conditions and is notably different than 1 (blue line), indicating that absolute values change between the conditions, but in a proportional manner. Promoters are colored black or gray depending on whether they fall within or outside the black lines, respectively. Dashed red lines indicate the lowest promoter activity level detected by our experimental system. (B) Same as in (A), but in logarithmic scale. Here, the scaling is reflected by the vertical shift between the blue and cyan lines. (C) Zoom‐in on (B), showing the major global response and the identities of several specifically responding genes, all involved in amino‐acid metabolism. (D–K) Same as in (B), but when comparing glucose (x axis) to fructose (D), sorbitol 1 M (E), growth at 39°C (F), NaCl 1 M (G), galactose lacking amino acids (H), galactose (I), glycerol (J), and ethanol (K).
Leeat Keren et al. Mol Syst Biol 2013;9:701
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