Schematic diagram showing the proposed spatial compartmentalization of the BmN4 piRNA pathway. Nuage components: BmVasa, BmAgo3, Siwi; piP-body components: BmSpnE, BmQin, BmDcp2. Siwi-D670A mutation leads to the accumulation of the mutant itself in piP-bodies and colocalization with BmSpnE and BmQin. See also Figure EV1. 