LOTUS and Tudor domain-containing proteins are intrinsic to germline development and are commonly found within germ granules. Drosophila versions of these proteins, Tejas and Tapas, localize Vasa to germ granules and play a role in piRNA-mediated retrotransposon silencing. Mammalian TDRD5 and TDRD7 proteins contain both LOTUS and Tudor domains and have essential roles during spermatogenesis. Here we describe D1081.7, the homolog of these proteins in C. elegans, named LOTR-1 for its LOTUS and Tudor domains. Within germ granules, LOTR-1 docks next to P granules to colocalize with the Z-granule component ZNFX-1. LOTR-1's Z-granule association requires its Tudor domain, but both LOTUS and Tudor deletions affect brood size when coupled with the knockdown of
glh-1. The localization of PGL-1, DEPS-1 and GLH-1 to P granules is not impacted in
lotr-1 mutants; however, LOTR-1 retains both ZNFX-1 and PRG-1 at the nuclear periphery. Quantitative LOTR-1 IP-mass spectrometry confirmed the Tudor-dependent association of ZNFX-1, PRG-1, DEPS-1, and other WAGO-class Argonautes. Like
znfx-1,
lotr-1 mutants redistribute the coverage of 22G-RNAs toward the 5' end of Mutator targets and impact transgenerational epigenetic inheritance. Unlike
znfx-1, the 5' shift in 22G-RNA coverage does not extend to CSR-1 targets. We hypothesize that LOTR-1 facilitates interactions between PRG-1/WAGO-class Argonautes, ZNFX-1 and target 3'UTRs to balance 22G-RNA distribution. These key aspects of LOTR-1 in C. elegans provide insight into TDRD5 and TDRD7 function during spermatogenesis and potential impact as cancer-testis (CT) antigens.