title: Natural Variation in plep-1 Causes Male-Male Copulatory Behavior in C. elegans.
abstract: In sexual species, gametes have to find and recognize one another. Signaling is thus central to sexual reproduction and involves a rapidly evolving interplay of shared and divergent interests [1-4]. Among Caenorhabditis nematodes, three species have evolved self-fertilization, changing the balance of intersexual relations [5]. Males in these androdioecious species are rare, and the evolutionary interests of hermaphrodites dominate. Signaling has shifted accordingly, with females losing behavioral responses to males [6, 7] and males losing competitive abilities [8, 9]. Males in these species also show variable same-sex and autocopulatory mating behaviors [6, 10]. These behaviors could have evolved by relaxed selection on male function, accumulation of sexually antagonistic alleles that benefit hermaphrodites and harm males [5, 11], or neither of these, because androdioecy also reduces the ability of populations to respond to selection [12-14]. We have identified the genetic cause of a male-male mating behavior exhibited by geographically dispersed C. elegans isolates, wherein males mate with and deposit copulatory plugs on one another's excretory pores. We find a single locus of major effect that is explained by segregation of a loss-of-function mutation in an uncharacterized gene, plep-1, expressed in the excretory cell in both sexes. Males homozygous for the plep-1 mutation have excretory pores that are attractive or receptive to copulatory behavior of other males. Excretory pore plugs are injurious and hermaphrodite activity is compromised in plep-1 mutants, so the allele might be unconditionally deleterious, persisting in the population because the species' androdioecious mating system limits the reach of selection.
authors.affiliation: Department of Biology and Center for Genomics & Systems Biology, New York University, 12 Waverly Place, New York, NY 10003, USA.
authors.forename: Luke M
authors.initials: LM
authors.lastname: Noble
authors.affiliation: Department of Biology and Center for Genomics & Systems Biology, New York University, 12 Waverly Place, New York, NY 10003, USA.
authors.forename: Audrey S
authors.initials: AS
authors.lastname: Chang
authors.affiliation: Department of Biology and Center for Genomics & Systems Biology, New York University, 12 Waverly Place, New York, NY 10003, USA.
authors.forename: Daniel
authors.initials: D
authors.lastname: McNelis
authors.affiliation: Department of Biology and Center for Genomics & Systems Biology, New York University, 12 Waverly Place, New York, NY 10003, USA.
authors.forename: Max
authors.initials: M
authors.lastname: Kramer
authors.affiliation: Department of Biology and Center for Genomics & Systems Biology, New York University, 12 Waverly Place, New York, NY 10003, USA.
authors.forename: Mimi
authors.initials: M
authors.lastname: Yen
authors.affiliation: Department of Biology and Center for Genomics & Systems Biology, New York University, 12 Waverly Place, New York, NY 10003, USA.
authors.forename: Jasmine P
authors.initials: JP
authors.lastname: Nicodemus
authors.affiliation: Department of Biology and Center for Genomics & Systems Biology, New York University, 12 Waverly Place, New York, NY 10003, USA.
authors.forename: David D
authors.initials: DD
authors.lastname: Riccardi
authors.affiliation: Department of Biology and Center for Genomics & Systems Biology, New York University, 12 Waverly Place, New York, NY 10003, USA.
authors.forename: Patrick
authors.initials: P
authors.lastname: Ammerman
authors.affiliation: Department of Biology and Center for Genomics & Systems Biology, New York University, 12 Waverly Place, New York, NY 10003, USA.
authors.forename: Matthew
authors.initials: M
authors.lastname: Phillips
authors.affiliation: Department of Biology and Center for Genomics & Systems Biology, New York University, 12 Waverly Place, New York, NY 10003, USA.
authors.forename: Tangirul
authors.initials: T
authors.lastname: Islam
authors.affiliation: Department of Biology and Center for Genomics & Systems Biology, New York University, 12 Waverly Place, New York, NY 10003, USA. Electronic address: mrockman@nyu.edu.
authors.forename: Matthew V
authors.initials: MV
authors.lastname: Rockman
mesh_terms: D000818:Animals; D017173:Caenorhabditis elegans / Q000235:genetics / Q000502:physiology*; D029742:Caenorhabditis elegans Proteins / Q000235:genetics* / Q000378:metabolism; D014644:Genetic Variation; D008297:Male; D011110:Polymorphism, Genetic; D012726:Sexual Behavior, Animal
chemical_list: D029742:Caenorhabditis elegans Proteins; C000609459:PLEP-1 protein, C elegans