Molecular basis of the copulatory plug polymorphism in Caenorhabditis elegans

Nature. 2008 Aug 21;454(7207):1019-22. doi: 10.1038/nature07171. Epub 2008 Jul 16.


Heritable variation is the raw material for evolutionary change, and understanding its genetic basis is one of the central problems in modern biology. We investigated the genetic basis of a classic phenotypic dimorphism in the nematode Caenorhabditis elegans. Males from many natural isolates deposit a copulatory plug after mating, whereas males from other natural isolates?including the standard wild-type strain (N2 Bristol) that is used in most research laboratories?do not deposit plugs. The copulatory plug is a gelatinous mass that covers the hermaphrodite vulva, and its deposition decreases the mating success of subsequent males. We show that the plugging polymorphism results from the insertion of a retrotransposon into an exon of a novel mucin-like gene, plg-1, whose product is a major structural component of the copulatory plug. The gene is expressed in a subset of secretory cells of the male somatic gonad, and its loss has no evident effects beyond the loss of male mate-guarding. Although C. elegans descends from an obligate-outcrossing, male?female ancestor, it occurs primarily as self-fertilizing hermaphrodites. The reduced selection on male?male competition associated with the origin of hermaphroditism may have permitted the global spread of a loss-of-function mutation with restricted pleiotropy.

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

  • Alleles
  • Amino Acid Sequence
  • Animals
  • Caenorhabditis elegans / genetics*
  • Caenorhabditis elegans / physiology
  • Caenorhabditis elegans Proteins / chemistry
  • Caenorhabditis elegans Proteins / genetics*
  • Caenorhabditis elegans Proteins / metabolism
  • Copulation*
  • Disorders of Sex Development / genetics
  • Gene Expression Regulation
  • Male
  • Mucins / chemistry
  • Mucins / genetics*
  • Mucins / metabolism
  • Polymorphism, Genetic*
  • Retroelements / genetics


  • Caenorhabditis elegans Proteins
  • Mucins
  • Retroelements
  • plg-1 protein, C elegans