Slow unreliable assembly of contractile rings from clumps in cofilin mutant cells. (A–C) Fluorescence micrographs of maximum intensity projections of wild-type and cofilin mutant cells expressing fluorescent proteins fused to contractile ring proteins. These proteins concentrated in strands (arrows) in dividing cells. (A) Rlc1p-mEGFP in wild-type and adf1-M2 cells. (B) GFP-Cdc15p in wild-type and adf1-M3 cells. (C) Cdc12p-3GFP in wild-type, adf1-M2, and adf1-M3 cells. (D and E) Time series of maximum intensity projections of negative-contrast confocal slides; fluorescence micrographs of cells expressing Rlc1p-3GFP. Numbers are times in minutes. (D) This adf1-M2 cell assembled a contractile ring from two clumps of nodes (empty arrows). The region of interest is outlined in the image of the whole cell on the left. (E) This adf1-M2 Δain1 cell failed to assemble stable strands or a ring. The last frame is a DIC micrograph showing the cell at the last time point. Bars, 5 µm.