Myo51 regulates actin structure and dynamics during cytokinesis. Actin was labeled with Lifeact-mGFP. (A) Time courses showing actin meshwork during contractile ring assembly (Video 5). Cell boundaries are indicated by broken lines. (B and C) Actin cable morphology (B) and orientation (C) during cytokinesis and interphase. Cells were treated with 100 µM Arp2/3 inhibitor CK666 for 5 min before imaging. Red and yellow arrows indicate misoriented and curved cables during cytokinesis and interphase, respectively. (C) Quantification of misoriented actin cables (see Materials and methods). Error bars indicate 1 SD. *, P < 0.001 compared with wt from a two-tailed t test. (D and E) Actin in the contractile ring is more dynamic in myo51Δ. Cells were preincubated with 100 µM CK666 for 5 min and imaged immediately after adding 4 µM Lat-A at time 0. (D and E) Micrographs (D) and fluorescence curves (E; mean ± SD) showing the fluorescence decay in the contractile ring before ring constriction. Bars, 5 µm.