Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Molecular basis of the copulatory plug polymorphism in Caenorhabditis elegans


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 plugs1. The copulatory plug is a gelatinous mass that covers the hermaphrodite vulva, and its deposition decreases the mating success of subsequent males2. 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 ancestor3,4, it occurs primarily as self-fertilizing hermaphrodites5,6,7. 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.

This is a preview of subscription content, access via your institution

Relevant articles

Open Access articles citing this article.

Access options

Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Figure 1: The plg-1 gene.
Figure 2: The mucin gene is plg-1.
Figure 3: The copulatory plug contains carbohydrate structures typical of mucins and plg-1 is expressed in only a small number of male cells.
Figure 4: The plg-1 loss-of-function allele is globally distributed and Cer1 has been recently active.


  1. Hodgkin, J. & Doniach, T. Natural variation and copulatory plug formation in Caenorhabditis elegans . Genetics 146, 149?164 (1997)

    CAS  PubMed  PubMed Central  Google Scholar 

  2. Barker, D. M. Copulatory plugs and paternity assurance in the nematode Caenorhabditis elegans . Anim. Behav. 48, 147?156 (1994)

    Article  Google Scholar 

  3. Kiontke, K. et al. Caenorhabditis phylogeny predicts convergence of hermaphroditism and extensive intron loss. Proc. Natl Acad. Sci. USA 101, 9003?9008 (2004)

    ADS  CAS  Article  PubMed  PubMed Central  Google Scholar 

  4. Cho, S., Jin, S. W., Cohen, A. & Ellis, R. E. A phylogeny of Caenorhabditis reveals frequent loss of introns during nematode evolution. Genome Res. 14, 1207?1220 (2004)

    CAS  Article  PubMed  PubMed Central  Google Scholar 

  5. Barriere, A. & Felix, M. A. High local genetic diversity and low outcrossing rate in Caenorhabditis elegans natural populations. Curr. Biol. 15, 1176?1184 (2005)

    CAS  Article  PubMed  Google Scholar 

  6. Barriere, A. & Felix, M. A. Temporal dynamics and linkage disequilibrium in natural Caenorhabditis elegans populations. Genetics 176, 999?1011 (2007)

    CAS  Article  PubMed  PubMed Central  Google Scholar 

  7. Sivasundar, A. & Hey, J. Sampling from natural populations with RNAi reveals high outcrossing and population structure in Caenorhabditis elegans . Curr. Biol. 15, 1598?1602 (2005)

    CAS  Article  PubMed  Google Scholar 

  8. Barriere, A. & Felix, M. A. Natural variation and population genetics of Caenorhabditis elegans . WormBook 10.1895/wormbook.1.43.1 (2005); 〈

    Google Scholar 

  9. Desseyn, J. L., Aubert, J. P., Porchet, N. & Laine, A. Evolution of the large secreted gel-forming mucins. Mol. Biol. Evol. 17, 1175?1184 (2000)

    CAS  Article  PubMed  Google Scholar 

  10. Perez-Vilar, J. & Hill, R. L. The structure and assembly of secreted mucins. J. Biol. Chem. 274, 31751?31754 (1999)

    CAS  Article  PubMed  Google Scholar 

  11. Lang, T., Alexandersson, M., Hansson, G. C. & Samuelsson, T. Bioinformatic identification of polymerizing and transmembrane mucins in the puffer fish Fugu rubripes . Glycobiology 14, 521?527 (2004)

    CAS  Article  PubMed  Google Scholar 

  12. Julenius, K., Molgaard, A., Gupta, R. & Brunak, S. Prediction, conservation analysis, and structural characterization of mammalian mucin-type O-glycosylation sites. Glycobiology 15, 153?164 (2005)

    CAS  Article  PubMed  Google Scholar 

  13. Bendtsen, J. D., Nielsen, H., von Heijne, G. & Brunak, S. Improved prediction of signal peptides: SignalP 3.0. J. Mol. Biol. 340, 783?795 (2004)

    Article  PubMed  Google Scholar 

  14. Dover, G. Molecular drive: A cohesive mode of species evolution. Nature 299, 111?117 (1982)

    ADS  CAS  Article  PubMed  Google Scholar 

  15. Lotan, R., Skutelsky, E., Danon, D. & Sharon, N. The purification, composition, and specificity of the anti-T lectin from peanut (Arachis hypogaea). J. Biol. Chem. 250, 8518?8523 (1975)

    CAS  PubMed  Google Scholar 

  16. Carlson, D. M. Structures and immunochemical properties of oligosaccharides isolated from pig submaxillary mucins. J. Biol. Chem. 243, 616?626 (1968)

    CAS  PubMed  Google Scholar 

  17. Lints, R. & Hall, D. H. Handbook of C. elegans male anatomy. WormAtlas〉 (2005)

    Google Scholar 

  18. Ganko, E. W., Fielman, K. T. & McDonald, J. F. Evolutionary history of Cer elements and their impact on the C. elegans genome. Genome Res. 11, 2066?2074 (2001)

    CAS  Article  PubMed  PubMed Central  Google Scholar 

  19. Britten, R. J. Active gypsy/Ty3 retrotransposons or retroviruses in Caenorhabditis elegans . Proc. Natl Acad. Sci. USA 92, 599?601 (1995)

    ADS  CAS  Article  PubMed  PubMed Central  Google Scholar 

  20. Barr, M. M. & Sternberg, P. W. A polycystic kidney-disease gene homologue required for male mating behaviour in C. elegans . Nature 401, 386?389 (1999)

    ADS  CAS  PubMed  Google Scholar 

  21. Peden, E. M. & Barr, M. M. The KLP-6 kinesin is required for male mating behaviors and polycystin localization in Caenorhabditis elegans . Curr. Biol. 15, 394?404 (2005)

    CAS  Article  PubMed  Google Scholar 

  22. Barr, M. M. & Garcia, L. R. Male mating behavior. WormBook 10.1895/wormbook.1.78.1 (2006); 〈〉.

    Google Scholar 

  23. Fisher, R. A. The Genetical Theory of Natural Selection (Oxford Univ. Press, 1930)

    Book  Google Scholar 

  24. Stern, D. L. Evolutionary developmental biology and the problem of variation. Evolution 54, 1079?1091 (2000)

    CAS  Article  PubMed  Google Scholar 

  25. Lints, R. & Emmons, S. W. Regulation of sex-specific differentiation and mating behavior in C. elegans by a new member of the DM domain transcription factor family. Genes Dev. 16, 2390?2402 (2002)

    CAS  Article  PubMed  PubMed Central  Google Scholar 

  26. Chasnov, J. R. & Chow, K. L. Why are there males in the hermaphroditic species Caenorhabditis elegans? Genetics 160, 983?994 (2002)

    CAS  PubMed  PubMed Central  Google Scholar 

  27. Cutter, A. D. & Ward, S. Sexual and temporal dynamics of molecular evolution in C. elegans development. Mol. Biol. Evol. 22, 178?188 (2005)

    CAS  Article  PubMed  Google Scholar 

  28. Stewart, A. D. & Phillips, P. C. Selection and maintenance of androdioecy in Caenorhabditis elegans . Genetics 160, 975?982 (2002)

    PubMed  PubMed Central  Google Scholar 

  29. Sulston, J. E. & Hodgkin, J. in The Nematode Caenorhabditis elegans (Cold Spring Harbor Press, 1988)

    Google Scholar 

  30. Brudno, M. et al. LAGAN and Multi-LAGAN: Efficient tools for large-scale multiple alignment of genomic DNA. Genome Res. 13, 721?731 (2003)

    CAS  Article  PubMed  PubMed Central  Google Scholar 

  31. Kamath, R. S. & Ahringer, J. Genome-wide RNAi screening in Caenorhabditis elegans . Methods 30, 313?321 (2003)

    CAS  Article  PubMed  Google Scholar 

  32. Tijsterman, M., Okihara, K. L., Thijssen, K. & Plasterk, R. H. PPW-1, a PAZ/PIWI protein required for efficient germline RNAi, is defective in a natural isolate of C. elegans . Curr. Biol. 12, 1535?1540 (2002)

    CAS  Article  PubMed  Google Scholar 

Download references


We thank the Caenorhabditis Genetics Center, M. Ailion, E. Dolgin, A. Barrière, M.-A. Félix and P. McGrath for strains and reagents. Work at Bowdoin College was supported by college funds, by the NIH (grant P20 RR-016463 from the INBRE Program of the National Center for Research Resources), the NSF (grant 0110994), and by an award to Bowdoin College by the Howard Hughes Medical Institute under the Undergraduate Science Education Program. Work at Princeton University was supported by grants from the NIH (R01 HG004321 to L.K. and P50 GM071508 to the Lewis-Sigler Institute), a James S. McDonnell Foundation Centennial Fellowship (L.K.), and a Jane Coffin Childs Fellowship (M.V.R.). We thank S. Civillico for assistance in the laboratory, F. Hagen for experimental advice, and E. Anderson, H. Coller, L. Gordon and H. Seidel for comments on the manuscript.

Author information

Authors and Affiliations


Corresponding author

Correspondence to Michael F. Palopoli.

Supplementary information

Supplementary Information 1

The file contains Supplementary Methods and Supplementary Figures S1-S5 with Legends. (PDF 1761 kb)

Supplementary Information 2

The file contains Supplementary Movie 1. Three-dimensional reconstruction of a stack of confocal images of an F1 male from a cross between CB4856 and QX1193, which carries the integrated plg-1::GFP transgene qqIs1. (AVI 16770 kb)

Supplementary Information 3

The file contains Supplementary Table 1 including natural isolate strains, localities, phenotypes, and genotypes. (XLS 32 kb)

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Palopoli, M., Rockman, M., TinMaung, A. et al. Molecular basis of the copulatory plug polymorphism in Caenorhabditis elegans. Nature 454, 1019–1022 (2008).

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI:

This article is cited by


By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.


Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing