FIGURE 3.

osk mRNA localization proceeds through three distinct mechanisms. In early oogenesis (top panel), a microtubule organizing center (MTOC) forms in the oocyte, and microtubules (green lines) emanate from there through the ring canals into the nurse cells. The motor protein dynein transports osk (blue) along these microtubules into the oocyte. During stages 8–9 of oogenesis (middle panel), microtubules (shaded green) reorganize so that their minus‐ends accumulate all around the oocyte cortex except at the posterior pole. The plus‐end directed motor kinesin drives osk (blue) away from the cortex and it accumulates at the posterior thanks to a weak plus‐end microtubule bias. In late oogenesis (lower panel) rapid cytoplasmic streaming (red arrows) takes place, which transports macromolecules throughout the oocyte cytoplasm. osk mRNA is carried along by these movements and is anchored at the posterior, where there is a relative absence of microtubules, by myosin V