Fig. 3. Actin is required for Myo2 ring formation but not for the recruitment of Myo2 to the medial cell cortex. myo2-gc cdc25-22 cells were synchronised by temperature shift and allowed to enter mitosis either in DMSO (A,B) or 10 µM latrunculin B. (C-E). A and C show the timing of cell cycle events in the two cultures. In control cells (A), Myo2 rings (green filled circles) formed before the appearance of binucleate cells (filled blue diamonds) or septa (filled black squares). (C) Myo2 rings and binucleate cells failed to appear in the absence of actin but septal material (shown as a dashed line to distinguish it from true septa in A), appears at the cell equator on cue. (B,D) Micrographs of Myo2-GFP (left panels) and DAPI-calcofluor staining (right panels) from the 40 minute time points in (A,C). Myo2 rings failed to form in latrunculin B but Myo2 nevertheless accumulated at the medial cell cortex (E) Detail from (D): arrows point to colocalisation of Myo2 and cell wall material. Bar, 10 µm.

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