Rapid genome shrinkage in a self-fertile nematode reveals sperm competition proteins

Science. 2018 Jan 5;359(6371):55-61. doi: 10.1126/science.aao0827.


To reveal impacts of sexual mode on genome content, we compared chromosome-scale assemblies of the outcrossing nematode Caenorhabditis nigoni to its self-fertile sibling species, C. briggsaeC. nigoni's genome resembles that of outcrossing relatives but encodes 31% more protein-coding genes than C. briggsaeC. nigoni genes lacking C. briggsae orthologs were disproportionately small and male-biased in expression. These include the male secreted short (mss) gene family, which encodes sperm surface glycoproteins conserved only in outcrossing species. Sperm from mss-null males of outcrossing C. remanei failed to compete with wild-type sperm, despite normal fertility in noncompetitive mating. Restoring mss to C. briggsae males was sufficient to enhance sperm competitiveness. Thus, sex has a pervasive influence on genome content that can be used to identify sperm competition factors.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Caenorhabditis / classification
  • Caenorhabditis / genetics*
  • Exons
  • Genome, Helminth
  • Glycoproteins / genetics*
  • Helminth Proteins / genetics*
  • Hermaphroditic Organisms / genetics*
  • INDEL Mutation
  • Introns
  • Male
  • Phylogeny
  • Proteome / genetics
  • Self-Fertilization / genetics*
  • Spermatozoa / metabolism*


  • Glycoproteins
  • Helminth Proteins
  • Proteome