Fig. 4: Convergent cortical actin flow aligns F-actin parallel to the division plane.

a Schematic showing the light activation protocol to track F-actin reorganization dynamics. Light activation was performed once at the midplane (i), then focused on the bottom surface (ii), and kept tracking the F-actin organization at the furrow surface (iii). b F-actin organization at the bottom surface of the liposome and corresponding order parameter before light activation. c F-actin organization at the furrow after deformation has ended. The dashed yellow rectangle is the region cropped in (d). d Time-lapse images showing the F-actin organization at the furrow (top), corresponding orientation field (middle) and order parameter (bottom) calculated within the dashed yellow rectangle. e PIV within the yellow rectangle in (d). Arrows show the total displacement, u, over 5 min, with vector magnitudes normalized by the maximum (left). The colormap represents local strain fields (right). f Mean order parameter and cumulative strain over time within the yellow rectangle in (d). g Scatter plot showing total strain vs. maximum increase of the mean order parameter \({\left\langle {S}_{{||}}\right\rangle }_{\max }-{\left\langle {S}_{{||}}\right\rangle }_{\min }\) calculated within the furrow (n = 26 liposomes and N = 16 independent experiments). The dashed line is a linear fitting. Inset shows the mean order parameter and cumulative strain over time used for the scatter plot. Data are presented as mean ± SD (g). ***p < 0.001 in a two-sided Pearson’s linear correlation coefficient (g). Scale bars, 10 μm. Source data are provided as a Source Data file.