Fig. 6.

Model for cytokinesis in Giardia. (A) Comparison of experimental perturbations and their corresponding control treatments. Note the distance to scission at which each perturbed cellular system slowed or arrested division. The stall point is interpreted as the point at which the pathway contributes to furrow progression. (B) Model for myosin-independent cytokinesis. The ventral discs in gray, actin in green, Rab11 in red, and forces driving daughter cell separation are indicated by orange arrows. 1, Mitosis is initiated, actin positions the microtubule cytoskeleton. 2, Rab11 loads onto the intracytoplasmic axonemes and is guided into the furrow by the nascent axonemes. Ventral disk opening permits furrow progression, and the intracytoplasmic caudal flagella push daughter discs in opposite directions to initiate a furrow. 3, Caudal axonemes continue pushing discs apart, and differential cortical actin and Laplace pressure (green arrows) direct furrow advancement. 4, Flagella propulsion generates cortical tension between daughter cells and actin, and Rab11 coordinates membrane remodeling for abscission.