Dataset Information

Demography and mating system shape the genome-wide impact of purifying selection in Arabis alpina.

ABSTRACT: Plant mating systems have profound effects on levels and structuring of genetic variation and can affect the impact of natural selection. Although theory predicts that intermediate outcrossing rates may allow plants to prevent accumulation of deleterious alleles, few studies have empirically tested this prediction using genomic data. Here, we study the effect of mating system on purifying selection by conducting population-genomic analyses on whole-genome resequencing data from 38 European individuals of the arctic-alpine crucifer Arabis alpina We find that outcrossing and mixed-mating populations maintain genetic diversity at similar levels, whereas highly self-fertilizing Scandinavian A. alpina show a strong reduction in genetic diversity, most likely as a result of a postglacial colonization bottleneck. We further find evidence for accumulation of genetic load in highly self-fertilizing populations, whereas the genome-wide impact of purifying selection does not differ greatly between mixed-mating and outcrossing populations. Our results demonstrate that intermediate levels of outcrossing may allow efficient selection against harmful alleles, whereas demographic effects can be important for relaxed purifying selection in highly selfing populations. Thus, mating system and demography shape the impact of purifying selection on genomic variation in A. alpina These results are important for an improved understanding of the evolutionary consequences of mating system variation and the maintenance of mixed-mating strategies.

SUBMITTER: Laenen B

PROVIDER: S-EPMC5789905 | biostudies-literature | 2018 Jan

REPOSITORIES: biostudies-literature

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Demography and mating system shape the genome-wide impact of purifying selection in <i>Arabis alpina</i>.

Laenen Benjamin B Tedder Andrew A Nowak Michael D MD Toräng Per P Wunder Jörg J Wötzel Stefan S Steige Kim A KA Kourmpetis Yiannis Y Odong Thomas T Drouzas Andreas D AD Bink Marco C A M MCAM Ågren Jon J Coupland George G Slotte Tanja T

Proceedings of the National Academy of Sciences of the United States of America 20180104 4

Plant mating systems have profound effects on levels and structuring of genetic variation and can affect the impact of natural selection. Although theory predicts that intermediate outcrossing rates may allow plants to prevent accumulation of deleterious alleles, few studies have empirically tested this prediction using genomic data. Here, we study the effect of mating system on purifying selection by conducting population-genomic analyses on whole-genome resequencing data from 38 European indiv ...[more]

PMID: 29301967

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Project description:Background and aimsSporophytic self-incompatibility (SI) prevents inbreeding in many members of the Brassicaceae, and has been well documented in a variety of high-profile species. Arabis alpina is currently being developed as a model system for studying the ecological genetics of arctic-alpine environments, and is the focus of numerous studies on population structure and alpine phylogeography. Although it is highly inbreeding throughout most of its range, populations in central Italy have been identified that show inbreeding coefficients (F(IS)) more typical of self-incompatible relatives. The purpose of this study was to establish whether this variation is due to a functioning SI system.MethodsOutcrossing rate estimates were calculated based on 16 allozyme loci and self-compatibility assessed based on controlled pollinations for six Italian populations that have previously been shown to vary in F(IS) values. Putative SRK alleles (the gene controlling the female component of SI in other Brassicaceae) amplified from A. alpina were compared with those published for other species. Linkage of putative SRK alleles and SI phenotypes was assessed using a diallel cross.Key resultsFunctional avoidance of inbreeding is demonstrated in three populations of A. alpina, corresponding with previous F(IS) values. The presence is described of 15 putative SRK-like alleles, which show high sequence identity to known alleles from Brassica and Arabidopsis and the high levels of synonymous and nonsynonymous variation typical of genes under balancing selection. Also, orthologues of two other members of the S-receptor kinase gene family, Aly8 (ARK3) and Aly9 (AtS1) are identified. Further to this, co-segregation between some of the putative S-alleles and compatibility phenotypes was demonstrated using a full-sibling cross design.ConclusionsThe results strongly suggest that, as with other species in the Brassicaceae, A. alpina has a sporophytic SI system but shows variation in the strength of SI within and between populations.

Dataset Information

Demography and mating system shape the genome-wide impact of purifying selection in Arabis alpina.

Publications

Demography and mating system shape the genome-wide impact of purifying selection in <i>Arabis alpina</i>.

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