Co-localization of DrPiwi-1 and DrPiwi-2 in the oogonial cytoplasm is essential for oocyte differentiation in sexualized planarians.

P-Element-induced wimpy testis (Piwi) subfamily proteins form complexes that bind to Piwi-interacting RNA. This interaction is crucial for stem cell regulation and formation, maintenance of germline stem cells, and gametogenesis in several metazoans. Planarians are effective models for studying stem cells.