Fig. 5
Lateral Actomyosin enrichment precedes basal actomyosin clearing. a Representative image sequence of a wild-type neuroblast expressing Sqh::mCherry (Myosin), LifeAct::GFP (Actin) and the Myosin activity FRET sensor. Curvature is determined for each pixel along the yellow line (4th row). Ingression occurs when curvature changes from “−“ to “ + ”. The region corresponding to the future cleavage furrow is indicated in red and plotted in the graphs below (grey line). Blue arrows emphasize furrowing. b Plot of a representative neuroblast showing Myosin (green line) and Actin (red line) intensity changes in the prospective furrow region, in relation to curvature changes. For this and subsequent plots, curves were smoothened (dashed black line with black triangles) and plotted in the same graph. The time difference between an increase in Myosin and Actin intensity in the prospective furrow region and furrowing (dashed lines and green and red arrows, respectively), was extracted from the smoothened curves and plotted in (c). d Plot showing changes in FRET ratios in the prospective furrow region in relation to furrowing. The time difference between the onset of FRET ratio increases and furrowing (dashed blue lines and blue arrows, respectively) are shown in e. f Actin (purple line) and Myosin (orange line) intensity changes were plotted for the basal cortex. The time difference between actomyosin intensity drops and furrowing (dashed lines and purple and orange arrows, respectively) were plotted in g. Asterisks denote statistical significance, derived from unpaired t tests: *p ≤ 0.05, **p ≤ 0.01, ***p ≤ 0.001, ****p ≤ 0.0001. Each measured cell (n) is represented with a dot in the scatter plots. For each experiment, the data were collected from at least 3 independent experiments. For each independent experiment, at least 5 larvae were dissected. Time: seconds (s). Scale bars: 5 µm. n.s. not significant
