Trans-specificity at loci near the self-incompatibility loci in Arabidopsis. Genetics

Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3JT, United Kingdom.
Genetics (Impact Factor: 5.96). 05/2006; 172(4):2699-704. DOI: 10.1534/genetics.105.051938
Source: PubMed


We compared allele sequences of two loci near the Arabidopsis lyrata self-incompatibility (S) loci with sequences of A. thaliana orthologs and found high numbers of shared polymorphisms, even excluding singletons and sites likely to be highly mutable. This suggests maintenance of entire S-haplotypes for long evolutionary times and extreme recombination suppression in the region.

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Available from: Jenny Hagenblad, Oct 03, 2015
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    • "An equivalent phenomenon can be observed in absence of contemporary gene flow, when ancestral polymorphisms have been maintained during past speciation events (Avise and Robinson 2008; Fig. 1B). Known examples of incomplete lineage sorting of adaptive significance mostly include alleles under long-term balancing selection such as in plant / plant pathogen recognition systems (Stahl et al. 1999; Rose et al. 2007; Horger et al. 2012), major histocompatibility complexes in mammals (Edwards et al. 1997; Loisel et al. 2006), AB-blood type defining enzymes and viral response factors in primates (Newman et al. 2006; Ferrer-Admetlla et al. 2009; Segurel et al. 2012), photoreceptors sustaining color vision in New World monkeys (Hunt et al. 1998), and self-incompatibility genes in plants and fungi (Wu et al. 1998; Schierup et al. 2001; Charlesworth et al. 2006; Igic et al. 2006). The recent development of methods dedicated to the detection of ancestral polymorphisms should yield to better estimates of the frequency of this phenomenon (Scally et al. 2012; Segurel et al. 2012). "
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    ABSTRACT: What is the nature of the genetic changes underlying phenotypic evolution? We have catalogued 1008 alleles described in the literature that cause phenotypic differences among animals, plants, and yeasts. Surprisingly, evolution of similar traits in distinct lineages often involves mutations in the same gene ("gene reuse"). This compilation yields three important qualitative implications about repeated evolution. First, the apparent evolution of similar traits by gene reuse can be traced back to two alternatives, either several independent causative mutations or a single original mutational event followed by sorting processes. Second, hotspots of evolution-defined as the repeated occurrence of de novo mutations at orthologous loci and causing similar phenotypic variation-are omnipresent in the literature with more than 100 examples covering various levels of analysis, including numerous gain-of-function events. Finally, several alleles of large effect have been shown to result from the aggregation of multiple small-effect mutations at the same hotspot locus, thus reconciling micromutationist theories of adaptation with the empirical observation of large-effect variants. Although data heterogeneity and experimental biases prevented us from extracting quantitative trends, our synthesis highlights the existence of genetic paths of least resistance leading to viable evolutionary change.
    Evolution 05/2013; 67(5):1235-50. DOI:10.1111/evo.12081 · 4.61 Impact Factor
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    • "Numerous tests in Arabidopsis sporophytic SI systems have yielded scant evidence for recombination (Kamau and Charlesworth, 2005; Charlesworth et al., 2006; Hagenblad et al., 2006; Edh et al., 2009). Recombination has been detected in SI loci of Brassica species (Kusaba et al., 1997; Awadalla and Charlesworth, 1999; Takuno et al., 2007) but only in genes or gene domains that do not play a direct role in self-incompatibility specificity (Takuno et al., 2007; Edh et al., 2009). "
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    ABSTRACT: Allorecognition is the ability of an organism to differentiate self or close relatives from unrelated conspecifics. Effective allorecognition systems are critical to the survival of organisms; they prevent inbreeding and facilitate fusions between close relatives. Where the loci governing allorecognition outcomes have been identified, the corresponding proteins often exhibit exceptional polymorphism. Two important questions about this polymorphism remain unresolved: how is it created, and how is it maintained. Because the genetic bases of several allorecognition systems have now been identified, including alr1 and alr2 in Hydractinia, fusion histocompatibility in Botryllus, the het (vic) loci in fungi, tgrB1 and tgrC1 in Dictyostelium, and self-incompatibility (SI) loci in several plant families, we are now poised to achieve a clearer understanding of how these loci evolve. In this review, we summarize what is currently known about the evolution of allorecognition loci, highlight open questions, and suggest future directions.
    Frontiers in Immunology 12/2011; 2:79. DOI:10.3389/fimmu.2011.00079
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    • "This feature indicates that SRK and SCR polymorphisms are very old and are subject to diversifying selection (Bechsgaard et al. 2006; Charlesworth et al. 2006). "
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    ABSTRACT: Flowering plants have evolved several mechanisms for controlling pollination. Genetic self-incompatibility is one of the most elaborate and “smart” systems known to date. In the Brassicaceae, recognition of “self” pollen in the self-incompatibility response is based on highly specific interactions between matched stigma surface receptors and pollen coat ligands encoded by haplotypes of the S locus, which triggers arrest of pollen tube development. This chapter presents a brief historical account of the analysis of SI in the Brassicaceae, an overview of our current understanding of the recognition and response phases of SI, and a summary of progress made in elucidating the genetic basis of loss of SI and switches to self-fertility in various lineages, with an emphasis on knowledge gained from analysis of a recently developed transgenic Arabidopsis thaliana self-incompatible model. KeywordsSelf-incompatibility-Receptor-Ligand-Signaling-Mating system-Self-fertility- Arabidopsis thaliana
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