title: Contrasted patterns of molecular evolution in dominant and recessive self-incompatibility haplotypes in Arabidopsis.
abstract: Self-incompatibility has been considered by geneticists a model system for reproductive biology and balancing selection, but our understanding of the genetic basis and evolution of this molecular lock-and-key system has remained limited by the extreme level of sequence divergence among haplotypes, resulting in a lack of appropriate genomic sequences. In this study, we report and analyze the full sequence of eleven distinct haplotypes of the self-incompatibility locus (S-locus) in two closely related Arabidopsis species, obtained from individual BAC libraries. We use this extensive dataset to highlight sharply contrasted patterns of molecular evolution of each of the two genes controlling self-incompatibility themselves, as well as of the genomic region surrounding them. We find strong collinearity of the flanking regions among haplotypes on each side of the S-locus together with high levels of sequence similarity. In contrast, the S-locus region itself shows spectacularly deep gene genealogies, high variability in size and gene organization, as well as complete absence of sequence similarity in intergenic sequences and striking accumulation of transposable elements. Of particular interest, we demonstrate that dominant and recessive S-haplotypes experience sharply contrasted patterns of molecular evolution. Indeed, dominant haplotypes exhibit larger size and a much higher density of transposable elements, being matched only by that in the centromere. Overall, these properties highlight that the S-locus presents many striking similarities with other regions involved in the determination of mating-types, such as sex chromosomes in animals or in plants, or the mating-type locus in fungi and green algae.
authors.affiliation: Laboratoire GEPV, Univ Lille 1 - Univ Lille Nord de France, Cité Scientifique, Villeneuve d'Ascq, France.
authors.forename: Pauline M
authors.initials: PM
authors.lastname: Goubet
authors.forename: Hélène
authors.initials: H
authors.lastname: Bergès
authors.forename: Arnaud
authors.initials: A
authors.lastname: Bellec
authors.forename: Elisa
authors.initials: E
authors.lastname: Prat
authors.forename: Nicolas
authors.initials: N
authors.lastname: Helmstetter
authors.forename: Sophie
authors.initials: S
authors.lastname: Mangenot
authors.forename: Sophie
authors.initials: S
authors.lastname: Gallina
authors.forename: Anne-Catherine
authors.initials: AC
authors.lastname: Holl
authors.forename: Isabelle
authors.initials: I
authors.lastname: Fobis-Loisy
authors.forename: Xavier
authors.initials: X
authors.lastname: Vekemans
authors.forename: Vincent
authors.initials: V
authors.lastname: Castric
mesh_terms: D017360:Arabidopsis / Q000235:genetics*; D029681:Arabidopsis Proteins / Q000235:genetics*; D004251:DNA Transposable Elements / Q000235:genetics; D019143:Evolution, Molecular; D015321:Gene Rearrangement; D005799:Genes, Dominant; D005808:Genes, Recessive; D006239:Haplotypes; D010802:Phylogeny; D011995:Recombination, Genetic; D060436:Self-Incompatibility in Flowering Plants / Q000235:genetics*; D017422:Sequence Analysis, DNA
chemical_list: D029681:Arabidopsis Proteins; D004251:DNA Transposable Elements