Cycles of Myo-II assembly and disassembly require dynamic RLC phosphorylation. (A–C) The sqh-AE and sqh-TA mutants inhibit Myo-II remodeling associated with pulses. Time-lapse images are representative cells from sqh1 germline clone embryos expressing the indicated phosphomutants and Memb::Cherry (membrane). Plots represent apical area and Myo-II intensity as a function of time for the same cells; the time highlighted in gray corresponds to the time time-lapse shown. Bars, 5 µm. (D) Quantification of frequency of instances where there is a rapid increase in Myo-II intensity (n = 94 sqh-TS cells, two embryos; n = 131 sqh-AE cells, three embryos; n = 92 sqh-TA cells, two embryos). (E) Quantification of frequency of instances of rapid apical area reduction (n = 94 sqh-TS cells, two embryos; n = 131 sqh-AE cells, three embryos; n = 92 sqh-TA cells, two embryos). (F) Quantification of maximal instantaneous constriction rate achieved in control or mutant cells (n = 138 sqh-TS cells, two embryos; n = 187 sqh-AE cells, three embryos; n = 172 sqh-TA cells, two embryos). (D–F) Error bars are SEM. (G) Mean cross-correlation between constriction rate and change in Myo-II intensity (n = 123 sqh-TS cells, two embryos; n = 143 sqh-AE cells, three embryos; n = 88 sqh-TA cells, two embryos). P-values were calculated at 0 time offset. **, P < 0.01; n.s., not significant.
