title: Balancing selection and low recombination affect diversity near the self-incompatibility loci of the plant Arabidopsis lyrata.
abstract: The self-incompatibility (S-) locus region of plants in the Brassica family is a small genome region. In Arabidopsis lyrata, the S-genes, SRK and SCR, encode the functional female and pollen recognition proteins, which must be coadapted to maintain correct associations between the two component genes, and thus self-incompatibility (SI). Recombinants would be self-compatible and thus probably disadvantageous in self-incompatible species. Therefore, tight linkage between the two genes in incompatibility systems is predicted to evolve to avoid producing such recombinant haplotypes. The evolution of low recombination in S-locus regions has not been rigorously tested. To test whether these regions' per-nucleotide recombination rates differ from those elsewhere in the genome, and to investigate whether the A. lyrata S-loci have the predicted effect on diversity in their immediate genome region, we studied diversity in genes that are linked to the S-loci but are not involved in incompatibility and are not under balancing selection. Compared with other A. lyrata loci, genes linked to the S-loci have extraordinarily high polymorphism. Our estimated recombination in this region, from fitting a model of the effects of S-allele polymorphism on linked neutral sites, supports the hypothesis of locally suppressed recombination around the S-locus.
authors.affiliation: Institute of Evolutionary Biology, University of Edinburgh, UK.
authors.forename: Esther
authors.initials: E
authors.lastname: Kamau
authors.forename: Deborah
authors.initials: D
authors.lastname: Charlesworth
mesh_terms: D017360:Arabidopsis / Q000235:genetics*; D029681:Arabidopsis Proteins / Q000235:genetics; D001483:Base Sequence; D017931:DNA Primers; D017343:Genes, Plant / Q000235:genetics*; D008040:Genetic Linkage; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000235:genetics; D011110:Polymorphism, Genetic; D011494:Protein Kinases / Q000235:genetics; D011995:Recombination, Genetic / Q000235:genetics*; D012641:Selection, Genetic; D017422:Sequence Analysis, DNA
chemical_list: D029681:Arabidopsis Proteins; D017931:DNA Primers; D010940:Plant Proteins; C100978:SCR protein, Arabidopsis; D011494:Protein Kinases; C079832:S-receptor kinase