title: Hitch-hiking to a locus under balancing selection: high sequence diversity and low population subdivision at the S-locus genomic region in Arabidopsis halleri.
abstract: Hitch-hiking to a site under balancing selection is expected to produce a local increase in nucleotide polymorphism and a decrease in population differentiation compared with the background genomic level, but empirical evidence supporting these predictions is scarce. We surveyed molecular diversity at four genes flanking the region controlling self-incompatibility (the S-locus) in samples from six populations of the herbaceous plant Arabidopsis halleri, and compared their polymorphism with sequences from five control genes unlinked to the S-locus. As a preliminary verification, the S-locus flanking genes were shown to co-segregate with SRK, the gene involved in the self-incompatibility reaction at the pistil level. In agreement with theory, our results demonstrated a significant peak of nucleotide diversity around the S-locus as well as a significant decrease in population genetic structure in the S-locus region compared with both control genes and a set of seven unlinked microsatellite markers. This is consistent with the theoretical expectation that balancing selection is increasing the effective migration rate in subdivided populations. Although only four S-locus flanking genes were investigated, our results suggest that these two signatures of the hitch-hiking effect are localized in a very narrow genomic region.
authors.affiliation: Université des Sciences et Technologies de Lille 1, Laboratoire de génétique et évolution des populations végétales, CNRS UMR 8016, Villeneuve d'Ascq, France.
authors.forename: Maria Valeria
authors.initials: MV
authors.lastname: Ruggiero
authors.forename: Bertrand
authors.initials: B
authors.lastname: Jacquemin
authors.forename: Vincent
authors.initials: V
authors.lastname: Castric
authors.forename: Xavier
authors.initials: X
authors.lastname: Vekemans
mesh_terms: D017360:Arabidopsis / Q000235:genetics*; D001483:Base Sequence / Q000235:genetics*; D005819:Genetic Markers; D014644:Genetic Variation; D005828:Genetics, Population; D018745:Genome, Plant; D012641:Selection, Genetic
chemical_list: D005819:Genetic Markers