Polarized actomyosin condensation requires dynamic Myo-II phosphorylation. (A–C) Uncoupling Myo-II activation from Rok phosphorylation disrupts medioapical Myo-II coalescence. Time-lapse images are representative cells from sqh1 germline clone embryos expressing the indicated phosphomutants and Memb::Cherry (membrane). Bars, 5 µm. (D) Quantification of Myo-II medioapical polarity, which is the difference between medioapical Myo-II (light green in schematic) and junctional Myo-II (green in schematic) intensities normalized by the total Myo-II intensity in a cell. Error bars are SEM (n = 120 sqh-TS cells, two embryos; n = 100 sqh-AE cells, two embryos; n = 118 sqh-TA cells, two embryos). (E–G) The sqh-AE mutant fails to condense apical F-actin. Time-lapse images are of representative cells from sqh1 germline clone embryos expressing the indicated phosphomutants and Utr::mCherry (F-actin). Arrowheads indicate Myo-II and F-actin condensation. Cell outlines in yellow were made by manually segmenting the subapical Utr::mCherry signal 2 µm below the apical meshwork. Bars, 5 µm. *, P < 0.05; **, P < 0.01.
