The localisation of bicoid mRNA to the anterior of the Drosophila oocyte, which is required for the patterning of the embryo's anteroposterior axis, involves the movement of bicoid mRNA transport particles along microtubules. Elizabeth Gavis and co-workers have been investigating how the bicoid mRNA localisation factors Staufen and Swallow act in bicoid mRNA transport and, on p. , they report that these proteins play direct and indirect roles, respectively. By carefully studying the distribution of Swallow, Staufen, dynein and bicoid mRNA during late oogenesis, the researchers show that Swallow and bicoid mRNA are transported independently and are not colocalised at their final destination. By contrast, Staufen, dynein and bicoid mRNA form non-membranous, electron-dense particles at the oocyte anterior. Given these and other results, the researchers propose that Swallow is transported independently by dynein to the oocyte plasma membrane, where it contributes indirectly to bicoid mRNA localisation by organising the cytoskeleton, whereas Staufen plays a direct role in dynein-dependent bicoid mRNA transport.
