Acts downstream of piRNA production to promote mediator complex-dependent endogenous siRNA biogenesis from piRNA-target mRNAs in the RNA interference pathway in germ cells (PubMed:32338603). Not required to identify target mRNA by the piRNA pathway (PubMed:32338603). Plays a role in both spermatogenesis and oogenesis and in maintaining fertility over multiple generations, probably by directing mutator-dependent silencing to piRNA-targeted genes (PubMed:32338603). Localizes to perinuclear foci in germ cells, called SIMR foci, which are distinct from Mutator foci, P granules and Z granules (PubMed:32338603). SIMR foci are stacked, with znfx-1 localizing between simr-1 and pgl-1 (PubMed:32338603). Its localization at SIMR foci is adjacent to the mutator complex protein mut-16 (PubMed:32338603). Perinuclear localization is not dependent on mut-16 (PubMed:32338603). Tudor domain specifically binds peptides with symmetrically dimethylated arginines (sDMA) and may facilitate protein-protein interactions (PubMed:32338603). The Tudor domain contains the conserved arginine and aspartic acid residues, which play a structural role, but lacks two of the four conserved aromatic residues, so it is unclear whether it is functional to recognize a methylated substrate (PubMed:32338603).