Liquid-like condensate function was shown to be required for RNAi inheritance in the nematode C.elegans. Surprisingly, we found that several mutants in core components of the germ granules (
pptr-1,
meg-3/4,
pgl-1,
wago-4) are nevertheless able to inherit RNAi. In
pptr-1 mutants this ability to inherit RNAi is enhanced, long lasting (>70 generations) and constant. In contrast,
meg-3/4 and
pgl-1 mutants can display strong RNAi inheritance, but gradually loose this capacity many generations after homozygosity. In
meg-3/4 mutants, we found that the function of the germ granules in the ancestors was memorized via small RNAs and transmitted to the progeny regardless of their own genotype, affecting their ability to inherit RNAi. When the
meg-3/4 functional alleles were introduced via the maternal lineage, both the wild-type and mutant progeny were able to inherit RNAi. However, when the
meg-3/4 functional alleles were introduced via the paternal lineage, the mutants and wild type progeny could not inherit RNAi at all. The impaired ability of wild type animals to inherit RNAi lasts for multiple (>16) generations, although their germ granules are intact. Even though germ granules are maternally deposited, we found that the paternal lineage contributes to the progeny's phenotype as well, further strengthening the idea that the phenotype in the progeny is not determined by their own germ granules. We found that the transmission of the germ granules function is mediated by the argonaute protein HRDE-1, which binds to small RNAs in the germline. Transient removal of
hrde-1 in the ancestors resets the progeny's ability to inherit RNAi. RNA-seq data from germ granules mutants revealed a substantial imbalance in small RNA pools. Overall, these findings suggest that the ancestral function of germ granules is memorized in the following generations via small RNAs. While the argonaute HRDE-1 was previously shown to be absolutely essential for heritable silencing, we found that hrde?1;meg?3/4 triple mutants can nevertheless inherit RNAi, highlighting that the disturbances in small RNA pools caused by defective germ granules can be transgenerationally inherited via non-conventional routes. Here we will present new insights about the way germ granules shapes the small RNA pool.