Transgenerational Sterility of Piwi Mutants Represents a Dynamic Form of Adult Reproductive Diapause

Abstract

Summary: Environmental stress can induce adult reproductive diapause, a state of developmental arrest that temporarily suspends reproduction. Deficiency for C. elegans Piwi protein PRG-1 results in strains that reproduce for many generations but then become sterile. We found that sterile-generation prg-1/Piwi mutants typically displayed pronounced germ cell atrophy as L4 larvae matured into 1-day-old adults. Atrophied germlines spontaneously reproliferated across the first days of adulthood, and this was accompanied by fertility for day 2–4 adults. Sterile day 5 prg-1 mutant adults remained sterile indefinitely, but providing an alternative food source could restore their fertility. Our data imply that late-generation prg-1 mutants experience a dynamic form of adult reproductive diapause, promoted by stress response, cell death, and RNAi pathways, where delayed fertility and reproductive quiescence represent parallel adaptive developmental outcomes. This may occur in response to a form of “heritable stress” that is transmitted by gametes and epigenetic in nature. : Heestand et al. examine a form of diapause that occurs in late-generation C. elegans Piwi/prg-1 mutants. They argue that the sterility of late-generation prg-1 mutants may be a consequence of “heritable stress.” Thus, an endogenous form of stress may be transmitted by germ cells to modulate heredity and fertility. Keywords: germ cell immortality, adult reproductive diapause, reproductive quiescence, prg-1, heritable stress