Genome‐wide association and environmental suppression of the mortal germline phenotype of wild C. elegans

Abstract

The animal germline lineage needs to be maintained along generations. However, some Caenorhabditis elegans wild isolates display a mortal germline phenotype, leading to sterility after several generations at 25°C. Using a genome‐wide association approach, we detect a significant peak on chromosome III around 5 Mb, confirmed by introgressions. Thus, a seemingly deleterious genotype is maintained at intermediate frequency in the species. Environmental rescue is a likely explanation, and indeed associated bacteria and microsporidia suppress the phenotype of wild isolates as well as mutants in small RNA inheritance ( nrde‐2 ) and histone modifications ( set‐2 ). Escherichia coli strains of the K‐12 lineage suppress the phenotype compared to B strains. By shifting a wild strain from E. coli K‐12 to E. coli B, we find that memory of the suppressing condition is maintained over several generations. Thus, the mortal germline phenotype of wild C. elegans is in part revealed by laboratory conditions and may represent variation in epigenetic inheritance and environmental interactions. This study also points to the importance of non‐genetic memory in the face of environmental variation. image Many C. elegans wild strains become sterile along generations in laboratory conditions, a phenotype caused by an intermediate‐frequency allele and rescued by associated bacteria and intestinal microsporidia. This study highlights the importance of the environment on germline maintenance. A major locus underlies the variation in mortal germline phenotype among C. elegans wild strains. The mortal germline of wild strains and mutants in small RNA inheritance and histone modifications is environmentally rescued. Wild C. elegans isolates appear to keep a multigenerational memory of the bacteria on which they were cultured.