Maternal proteins help to establish body axes in many developing organisms. In Drosophila, the maternally encoded protein Oskar is responsible for the formation of the posterior pole plasm in the egg and thus the development of the adult's abdomen and germline. Jenny, Hachet and colleagues now report that oskar mRNA has an additional, translation-independent role in early Drosophila oogenesis (see ). Classical oskar mutants, which produce embryos that lack an abdomen and germ cells, make oskar mRNA but no Oskar protein. The researchers describe two new mutants in which little or no oskar mRNA is made. These mutants are sterile because of an early arrest in oogenesis, but their egg-less defect can be rescued by expression of the oskar 3′untranslated region alone, indicating that oskar mRNA mediates this early oskar function. The researchers suggest that oskarmRNA might either sequester a negative regulator of oogenesis or provide a scaffold on which the cytoplasmic complexes needed for oocyte development are assembled.
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