Figure 2.

Positive feedback of F-actin via the vesicle organizing center hypothesis. Vesicles can interact indirectly with actin filament via myosin XI and directly via associated formin. As the actin polymerizes more myosin XI carrying vesicles attach to actin. Positive feedback continues as more myosin XIs attach to actin filaments and more vesicles begin to nucleate the polymerization of more filaments. Vesicles eventually diffuse and are exocytosed. Membrane is recycled via endocytosis and some of the endocytic cargo is recycled at the apex for continuous secretion.