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Fig. 5 ERK activity becomes more pulsatile as periderm expansion slows. (A) Stills from timelapse imaging of representative periderm cells expressing krt4:ERK-KTR-mCerulean and krt4:H2A-mCherry. While some pulses of ERK activity are seen at 30 to 50 hpf (Top panel), ERK activity becomes increasingly pulsatile from 54 to 74 hpf (Bottom panel). (Scale bar, 10 µm.) (B) Mean of CWT of ERK activity signal for 30 to 50 hpf embryos during randomly chosen 5 h time window of nonmitotic cells, averaged across the individual CWT plots for individual cell ERK traces. Traces derived from 5 embryos, with total 107 cells (traces). For 54 to 74 hpf embryos, cells from 4 embryos used with total 99 cells (traces). The plots were modified to exclude CWT results along low-confidence regions of the trace which are confounded by edge effects. There is a statistically significant difference in the mean of the CWT plots between 30 to 50 hpf and 54 to 74 hpf (C) based on the one-sided KS test, P-value = 4e-5, suggesting higher average CWT value at 54 to 74 hpf implying more pulsatile ERK activity.