Involved both in the piRNA and miRNA metabolic processes. As a component of the meiotic nuage, plays a central role during oogenesis by repressing transposable elements and preventing their mobilization, which is essential for the germline integrity. Repression of transposable elements is mediated via the piRNA metabolic process, which mediates the repression of transposable elements during meiosis by forming complexes composed of piRNAs and Piwi proteins and governs the repression of transposons. As a nuclear component, it is required for proper differentiation in the germline stem cell (GSC) lineage by repressing microRNA-7 (miR-7), thereby acting as an indirect regulator of bag-of-marbles (Bam). Acts by binding to the promoter of miR-7 gene and repressing its expression; miR-7 repression alleviates the Bam repression by miR-7, thereby allowing differentiation in the germline stem cell (GSC) lineage. Indirectly required to position the microtubule organizing center in stage 2-6 oocytes. Component of the meiotic nuage, also named P granule, a germ-cell-specific organelle required to repress transposon activity during meiosis. Vas, aub and spn-E are required for nuage localization. Shuttles between the cytoplasm and the nucleus. In germaria and egg chambers, it is detected in the germline. In the germarium, it is in all regions, including region I where the germ cells are dividing. In early egg chambers, it is uniformly distributed throughout the nurse cells and oocyte but, by stage 5, it is most concentrated around the outer margins of the cells, closest to the periphery of the egg chamber. Level decreases in stages 5 and 6, but most noticeably in the oocyte, where protein level remains. No detectable protein from stage 8 onward (at protein level). Female sterility and defects in karyosome formation and oocyte polarity due to transposable element derepression. Ovary shows mislocalization of 2 proteins involved in the microRNA and/or RNAi pathways, Dicer and AGO2. In testis, transit-amplifying cysts fail to differentiate into primary spermatocytes, instead breaking down into ectopic germline stem cells (GSC) and smaller cysts, due to a depletion of Bag-of-marbles (Bam) protein. Belongs to the maelstrom family.