Figure 1.

Dicytostelium myosin-null cells fail to form furrows during cytokinesis in suspension as shown by sequential differential interference contrast images. In these images, time 0 indicates the start of rounding and quiescence. (A) Cells expressing wild-type myosin can round up, elongate, furrow, and separate. Times of the panels are −70, 0, 140, 210, 280, and 350 s. Ruffling of the polar regions, as indicated by black arrows, coincided with the furrowing (210 s). (B) Myosin-null cells cannot divide in suspension. Times of the panels are −200, 0, 230, 430, and 570 s. They can round up, but they fail to elongate and furrow. However, like wild-type cells, they are able to polar ruffle, as indicated by arrows, at about the same time as wild-type cells (230 s).