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We report studies of seven members of the S-domain gene family in Arabidopsis lyrata, a member of the Brassicaceae that has a sporophytic self-incompatibility (SI) system. Orthologs for five loci are identifiable in the self-compatible relative A. thaliana. Like the Brassica stigmatic incompatibility protein locus (SRK), some of these genes have kinase domains. We show that several of these genes are unlinked to the putative A. lyrata SRK, Aly13. These genes have much lower nonsynonymous and synonymous polymorphism than Aly13 in the S-domains within natural populations, and differentiation between populations is higher, consistent with balancing selection at the Aly13 locus. One gene (Aly8) is linked to Aly13 and has high diversity. No departures from neutrality were detected for any of the loci. Comparing different loci within A. lyrata, sites corresponding to hypervariable regions in the Brassica S-loci (SLG and SRK) and in comparable regions of Aly13 have greater replacement site divergence than the rest of the S-domain. This suggests that the high polymorphism in these regions of incompatibility loci is due to balancing selection acting on sites within or near these regions, combined with low selective constraints.

Original publication

DOI

10.1093/genetics/164.4.1519

Type

Journal article

Journal

Genetics

Publication Date

08/2003

Volume

164

Pages

1519 - 1535

Addresses

Institute of Cell, Animal and Population Biology, University of Edinburgh, Ashworth Laboratories, King's Buildings, West Mains Road, Edinburgh EH9 3JT, Scotland, UK. deborah.charlesworth@ed.ac.uk

Keywords

Arabidopsis, Plant Proteins, Cloning, Molecular, Sequence Analysis, DNA, Genetics, Population, Evolution, Molecular, Phylogeny, Recombination, Genetic, Amino Acid Sequence, Base Sequence, Sequence Homology, Amino Acid, Haplotypes, Linkage Disequilibrium, Polymorphism, Genetic, Alleles, Genes, Plant, Genome, Plant, Molecular Sequence Data, Genetic Variation, Selection, Genetic, Genetic Linkage