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. Author manuscript; available in PMC: 2020 Feb 11.
Published in final edited form as: Dev Cell. 2019 Feb 11;48(3):361–370.e3. doi: 10.1016/j.devcel.2019.01.009

Figure 5. Distinct target genes act as accumulators and thresholders of Erk activity.

Figure 5.

(a) Model of cumulative load sensing by an accumulator/ thresholder circuit. An accumulator node would increase linearly in response to Erk activity until a critical threshold θ is reached, at which point a thresholder node would turn on in a switch-like fashion. (b,c) Analysis of RNA FISH data from OptoSOS embryos exposed to varying durations of blue light and stained for (b) tll and (c) hkb/mist. The mean expression levels around the surface the embryo is shown in each embryo-shaped heatmap; at least 50 embryos were analyzed for each light duration in b and c. The heatmaps are saturated so that the white color is equivalent to the maximum level seen in a wild-type embryo (full plots are shown in Figure S5). For the inset plots in c-d, the gene expression of cells at the dorsal-most cap of the embryo is plotted as a function of light duration, where a value of 1 is set to the maximum RNA signal seen in wild-type embryos.