Mutator foci are perinuclear granules in the germline of Caenorhabditis elegans that are required for the amplification of 22G-small interfering RNAs (siRNAs) (Phillips et al., 2012). These mutator-dependent siRNAs act downstream of primary endogenous and exogenous siRNA pathways and are necessary for robust and heritable silencing (Pak et al., 2007; Sijen et al., 2007; Gu et al., 2009; Gent et al., 2010; Vasale et al., 2010; Phillips et al., 2012). There are numerous factors that have been identified that localize to Mutator foci and are required for mutator-dependent siRNA biogenesis. These mutator-class proteins include the core component of Mutator foci MUT-16, the nucleotidyl transferase MUT-2, the 3-5 exonuclease MUT-7, the DEAD-box RNA helicases MUT-14 and SMUT-1, the Zc3h12a-like ribonucleases RDE-8, NYN-1, and NYN-2, and two proteins of unknown function, MUT-15 and RDE-2 (Ketting et al., 1999; Tijsterman et al., 2002; Vastenhouw et al., 2003; Chen et al., 2005; Tops et al., 2005; Phillips et al., 2012; Phillips et al., 2014; Tsai et al., 2015). Additionally, the RNA-dependent RNA polymerase RRF-1 localizes to Mutator foci but is redundant with EGO-1 for mutator-dependent siRNA biogenesis (Phillips et al., 2012; Gu et al., 2009). It was previously shown that mutations in mutator-class genes are sterile at elevated temperature (Ketting et al., 1999; Zhang et al., 2011; Rogers and Phillips, 2020). Recently, we performed a brood size assay using wild-type and mut-16
hermaphrodites cultured at 20C. We found that compared to wild-type animals, mut-16
mutant animals lay fewer eggs (56% fewer eggs laid compared to wild-type animals), and of those eggs, fewer mut-16
mutant eggs hatch (81% of mut-16
mutant eggs hatch compared to wild-type, where 100% of the eggs hatch) (Rogers and Phillips, 2020). Furthermore, 100% of wild-type larvae successfully mature to adulthood, whereas only 85% of mut-16
mutant larvae mature to adulthood (Rogers and Phillips, 2020). The reduced hatching rates and larval arrest of mut-16
mutant animals had not been previously reported...