title: Selection on amino acid substitutions in Arabidopsis.
abstract: Studies of nucleotide diversity have found an excess of low-frequency amino acid polymorphisms segregating in Arabidopsis thaliana, suggesting a predominance of weak purifying selection acting on amino acid polymorphism in this inbreeding species. Here, we investigate levels of diversity and divergence at synonymous and nonsynonymous sites in 6 circumpolar populations of the outbreeding Arabidopsis lyrata and compare these results with A. thaliana, to test for differences in mutation and selection parameters across genes, populations, and species. We find that A. lyrata shows an excess of low-frequency nonsynonymous polymorphisms both within populations and species wide, consistent with weak purifying selection similar to the patterns observed in A. thaliana. Furthermore, nonsynonymous polymorphisms tend to be more restricted in their population distribution in A. lyrata, consistent with purifying selection preventing their geographic spread. Highly expressed genes show a reduced ratio of amino acid to synonymous change for both polymorphism and fixed differences, suggesting a general pattern of stronger purifying selection on high-expression proteins.
authors.affiliation: Department of Biology, York University, Toronto, Ontario, Canada.
authors.forename: John Paul
authors.initials: JP
authors.lastname: Foxe
authors.forename: Vaqaar-un-Nisa
authors.initials: VU
authors.lastname: Dar
authors.forename: Honggang
authors.initials: H
authors.lastname: Zheng
authors.forename: Magnus
authors.initials: M
authors.lastname: Nordborg
authors.forename: Brandon S
authors.initials: BS
authors.lastname: Gaut
authors.forename: Stephen I
authors.initials: SI
authors.lastname: Wright
mesh_terms: D019943:Amino Acid Substitution; D000818:Animals; D017360:Arabidopsis / Q000235:genetics*; D029681:Arabidopsis Proteins / Q000235:genetics*; D001499:Bayes Theorem; D005828:Genetics, Population; D006801:Humans; D011110:Polymorphism, Genetic; D012641:Selection, Genetic
chemical_list: D029681:Arabidopsis Proteins