Involved in specific localization of cytoplasmic proteins during the formation of pole plasm. Required for synthesis and/or stability of oskar protein (osk) and localization of tudor (tud) in both the nuage and posterior pole of the oocyte. Required for normal posterior localization of osk in later stages of oogenesis and for posterior localization of the vasa (vas) protein during the entire process of pole plasm assembly. May act by regulating the complex that contains the arginine N-methyltransferase csul. Interacts with csul and tud. In oocytes, localizes to pole plasm and nuage (at protein level). Expressed stronger in the germline than in somatic cells. In the germarium it sometimes concentrates in perinuclear aggregates that disappear by stage 2 of oogenesis. At later stages, it is uniformly distributed in the nurse cells and oocyte, as well as in young embryos, with no particular enrichment at the posterior or inside the pole cells (at protein level). Expressed both maternally and zygotically. Abundant in ovaries, early embryos and adult females, but reduced in adult males.