Involved in the piRNA pathway in germline. tissues. Interacts with rhi. Localized to perinuclear puncta in the nurse cells of younger egg chambers. Accumulates at centromeric/pericentromeric positions in germ-cell nuclei and strongly colocalizes with the major heterochromatic domains. Females exhibit severely reduced fecundity. Defects in germline cyst development and result in ventralized eggs as a result of reduced Grk expression. Increase in the transcript levels of two retrotransposable elements, Het-A and Tart. Belongs to the DXO/Dom3Z family. In contrast to other members of the family that display ribonuclease activity, lacks the conserved catalytic sites that bind the divalent metal cations. Ribonuclease activity is therefore unsure. Extended N-terminus.