Myo51 is involved in both early and late stages of cytokinesis. (A and B) Time courses (A) and quantifications (B) of contractile ring assembly in myo51Δ (Video 3) and two headless myo51 mutants using Rlc1 as the node and ring marker at 23°C. Arrows indicate the compact rings. Time 0 marks node appearance. Cell boundaries are indicated by broken lines. *, P < 0.001 compared with wt from a two-tailed t test. (C–F) Movement of Rlc1 nodes during contractile ring assembly in wt and myo51Δ at 23°C. (C) Time courses of node condensation from the boxed regions on the left. Red arrows mark nodes moving toward the center of the broad bands of nodes whereas green arrows indicate nodes moving toward cell tips for a certain time. (D–F) n = ∼30 nodes for each strain. (D) Histograms of angles of node displacements. Angles between directions of node displacements during ∼3 min and the long cell axis. (E) Node displacements during ∼3 min. (F) Distribution of instantaneous speed of node movements during ∼3 min (n > 2,000 speeds). (G) Synthetic interactions between rng8Δ, rng9Δ, or myo51 mutations and myp2Δ. Cells were grown at 36°C for 8 h before imaging. (H) myo51Δ myp2Δ cells are defective in ring stability/anchoring and disassembly during ring constriction. Arrows indicate distorted contractile ring, and the arrowhead indicates a contractile ring uncoupled from the invaginated membrane. See Video 4. Bars, 5 µm.