Abstract
Deficiency for small RNA nuclear silencing proteins that promote heterochromatin maintenance leads to defects in germ cell immortality where fertile mutant strains become sterile over successive generations. The transgenerational sterility of small RNA nuclear silencing is associated with mis-wiring of small RNA pathways and with progressive deterioration of heterochromatin, which leads to increased levels of transposon expression, transposition and RNA-DNA hybrids. However, the cause of transgenerational sterility in small RNA nuclear silencing mutants is not understood. We found that sterile small RNA genome silencing mutants display altered perinuclear germ granules. Moreover, germ granule dysfunction was sufficient to induce phenotypes associated with sterile small RNA genome silencing mutants, including germline atrophy, reproductive diapause and univalents in oocytes. We conclude that germ granules, which are intimately associated with small RNA nuclear silencing proteins and RNAs, orchestrate the transgenerational sterility of small RNA genome silencing mutants.