title: Parallel evolution of domesticated Caenorhabditis species targets pheromone receptor genes.
abstract: Evolution can follow predictable genetic trajectories, indicating that discrete environmental shifts can select for reproducible genetic changes. Conspecific individuals are an important feature of an animal's environment, and a potential source of selective pressures. Here we show that adaptation of two Caenorhabditis species to growth at high density, a feature common to domestic environments, occurs by reproducible genetic changes to pheromone receptor genes. Chemical communication through pheromones that accumulate during high-density growth causes young nematode larvae to enter the long-lived but non-reproductive dauer stage. Two strains of Caenorhabditis elegans grown at high density have independently acquired multigenic resistance to pheromone-induced dauer formation. In each strain, resistance to the pheromone ascaroside C3 results from a deletion that disrupts the adjacent chemoreceptor genes serpentine receptor class g (srg)-36 and -37. Through misexpression experiments, we show that these genes encode redundant G-protein-coupled receptors for ascaroside C3. Multigenic resistance to dauer formation has also arisen in high-density cultures of a different nematode species, Caenorhabditis briggsae, resulting in part from deletion of an srg gene paralogous to srg-36 and srg-37. These results demonstrate rapid remodelling of the chemoreceptor repertoire as an adaptation to specific environments, and indicate that parallel changes to a common genetic substrate can affect life-history traits across species.
authors.affiliation: Howard Hughes Medical Institute, Laboratory of Neural Circuits and Behavior, The Rockefeller University, New York, New York 10065, USA.
authors.forename: Patrick T
authors.initials: PT
authors.lastname: McGrath
authors.forename: Yifan
authors.initials: Y
authors.lastname: Xu
authors.forename: Michael
authors.initials: M
authors.lastname: Ailion
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Garrison
authors.forename: Rebecca A
authors.initials: RA
authors.lastname: Butcher
authors.forename: Cornelia I
authors.initials: CI
authors.lastname: Bargmann
mesh_terms: D000222:Adaptation, Physiological / Q000235:genetics / Q000502:physiology; D000818:Animals; D005075:Biological Evolution; D017173:Caenorhabditis elegans / Q000145:classification / Q000187:drug effects / Q000235:genetics* / Q000502:physiology*; D004777:Environment; D019143:Evolution, Molecular; D006017:Glycolipids / Q000378:metabolism / Q000494:pharmacology; D006605:Hibernation / Q000235:genetics / Q000502:physiology; D007814:Larva / Q000254:growth & development; D010675:Pheromones / Q000378:metabolism / Q000494:pharmacology; D011156:Population Density; D040641:Quantitative Trait Loci / Q000235:genetics; D043563:Receptors, Pheromone / Q000235:genetics* / Q000378:metabolism
chemical_list: D006017:Glycolipids; D010675:Pheromones; D043563:Receptors, Pheromone; C004441:ascaroside C