title: Simplification and desexualization of gene expression in self-fertile nematodes.
abstract: Evolutionary transitions between sexual modes could be potent forces in genome evolution. Several Caenorhabditis nematode species have evolved self-fertile hermaphrodites from the obligately outcrossing females of their ancestors. We explored the relationship between sexual mode and global gene expression by comparing two selfing species, C. elegans and C. briggsae, with three phylogenetically informative outcrossing relatives, C. remanei, C. brenneri, and C. japonica. Adult transcriptome assemblies from the selfing species are consistently and strikingly smaller than those of the outcrossing species. Against this background of overall simplification, genes conserved in multiple outcrossing species with strong sex-biased expression are even more likely to be missing from the genomes of the selfing species. In addition, the sexual regulation of remaining transcripts has diverged markedly from the ancestral pattern in both selfing lineages, though in distinct ways. Thus, both the complexity and the sexual specialization of transciptomes are rapidly altered in response to the evolution of self-fertility. These changes may result from the combination of relaxed sexual selection and a recently reported genetic mechanism favoring genome shrinkage in partial selfers.
authors.affiliation: Department of Biology, University of Maryland, College Park, MD 20742, USA.
authors.forename: Cristel G
authors.initials: CG
authors.lastname: Thomas
authors.forename: Renhua
authors.initials: R
authors.lastname: Li
authors.forename: Harold E
authors.initials: HE
authors.lastname: Smith
authors.forename: Gavin C
authors.initials: GC
authors.lastname: Woodruff
authors.forename: Brian
authors.initials: B
authors.lastname: Oliver
authors.forename: Eric S
authors.initials: ES
authors.lastname: Haag
mesh_terms: D000818:Animals; D005075:Biological Evolution; D005260:Female; D005786:Gene Expression Regulation / Q000502:physiology*; D015801:Helminth Proteins / Q000235:genetics / Q000378:metabolism*; D057850:Hermaphroditic Organisms / Q000235:genetics* / Q000378:metabolism*; D008297:Male; D009348:Nematoda / Q000235:genetics / Q000378:metabolism*; D013045:Species Specificity
chemical_list: D015801:Helminth Proteins