Posterior localization of the Drosophila Giα protein during early embryogenesis requires a subset of the posterior group genes

Shortly after fertilization in Drosophila embryos, the G-protein a subunit, Giα, undergoes a dramatic redistribution. initially granules containing Giα are present throughout the embryonic cortex but during nuclear cleavage they become concentrated at the posterior pole and are lost by the blastoderm stage. Mutations that eliminate anterior structures bicoid, swallow, and exuperantia did not prevent the posterior accumulation of Giα. Likewise, embryos from mothers with dominant gain of function mutations in the Bicaudal D gene show normal polarization of Giα: granules. By contrast, a subset of mutations which eliminate posterior structures, cappuccino, spire, staufen, mago nashi, valois, and oskar, prevented the posterior accumulation of Giα. It is important to note that mutations in posterior genes lower in the putative hierarchy vasa, tudor nanos, and pumilio did not affect Giα redistribution. From these results we conclude that Giα redistribution to the posterior pole depends on maternal factors involved in the localization of the posterior morphogen nanos.