Figure 4.

Single-cell clock response to dark-pulse perturbations. (A and B) Individual traces (P_kaiBC::eyfp-ssrA) show phase shifts caused by weak (2-h dark pulse) and strong (12-h dark pulse) perturbations. (C and D) Phase resetting of individual cells grown under constant light conditions for 36 h before being subjected to a 2-h (blue) or 12-h (red) pulse of darkness, with specific examples from panels (A) and (B) highlighted (^∗). Two distinct resetting behaviors are observed: a robust response (blue line in C) or a full phase reset (red line in D). (E–G) Density plot showing the phase response to 5-h, 7-h, and 9-h dark pulses, with resetting that switches between no response and full reset (blue and red dashed lines, respectively). Cells were grown under constant light conditions for 36 h before each dark pulse. In all panels, the location of subjective day (night) is marked with a light (dark) gray bar. See also Fig. S3. To see this figure in color, go online.