[38] Detection and quantification of concerted evolution and molecular drive

Dover, Gabriel A.; Linares, Andrés; Bowen, Timothy; Hancock, John M.

doi:10.1016/0076-6879(93)24039-w

Cited by 60 publications

(22 citation statements)

References 28 publications

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“…The heteromorphism of homologous NORs has been well documented both in animals (Delany et al, 1991;Abuin et al, 1996;Hirai et al, 1998;Mandrioli et al, 1999) and plants (Miller et al, 1980;Moscone et al, 1995;Zoldos et al, 1999). This may be related to differences in the ribosomal gene copy number at homologous sites, which has been attributed to unequal crossing over (Fitch et al, 1990;Dover et al, 1993;Delany and Krupkin, 1999;Mandrioli et al, 1999). In D. melanogaster, several lines of evidence suggest that the chromosome 4 may have derived from an ancestral X chromosome (Hochman, 1976;Larsson et al, 2001).…”

Section: Resultsmentioning

confidence: 97%

Evolution of the chromosomal location of rDNA genes in two Drosophila species subgroups: ananassae and melanogaster

et al. 2005

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The evolution of the chromosomal location of ribosomal RNA gene clusters and the organization of heterochromatin in the Drosophila melanogaster group were investigated using fluorescence in situ hybridization and DAPI staining to mitotic chromosomes. The investigation of 18 species (11 of which were being examined for the first time) belonging to the melanogaster and ananassae subgroups suggests that the ancestral configuration consists of one nucleolus organizer (NOR) on each sex chromosome. This pattern, which is conserved throughout the melanogaster subgroup, except in D. simulans and D. sechellia, was observed only in the ercepeae complex within the ananassae subgroup. Both sexlinked NORs must have been lost in the lineage leading to D. varians and in the ananassae and bipectinata complexes, whereas new sites, characterized by intra-species variation in hybridization signal size, appeared on the fourth chromosome related to heterochromatic rearrangements. Nucleolar material is thought to be required for sex chromosome pairing and disjunction in a variety of organisms including Drosophila. Thus, either remnant sequences, possibly intergenic spacer repeats, are still present in the sex chromosomes which have lost their NORs (as observed in D. simulans and D. sechellia), or an alternative mechanism has evolved. Heredity (2005) 94, 388-395.

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Section: Resultsmentioning

confidence: 97%

Evolution of the chromosomal location of rDNA genes in two Drosophila species subgroups: ananassae and melanogaster

et al. 2005

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“…Sequence homogenization of gene families is a well-recognized phenomenon termed ''concerted evolution'' (26). Selection by a specific pathogen is only imposed on a plant population at intervals and many generations may set seed without experiencing a specific avirulence determinant.…”

Section: Discussionmentioning

confidence: 99%

Recombination between diverged clusters of the tomato Cf-9 plant disease resistance gene family

Parniske

Jones

1999

Proc. Natl. Acad. Sci. U.S.A.

111

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The tomato Cf-4 and Cf-9 genes are the founder members of a large gene family of homologues of Cladosporium fulvum resistance gene Cf-9 (Hcr9 genes), several of which confer resistance against C. fulvum through recognition of different pathogen-encoded avirulence determinants. Three loci of tandemly repeated Hcr9 genes-Southern Cross (SC), Milky Way (MW), and Northern Lights (NL)-are located on the short arm of tomato chromosome 1. Comparisons between 2 SC-Hcr9s, 11 from MW, and 5 from NL implicated sequence exchange between gene family members in their evolution. The extent to which novel variants can be generated by recombination depends on the degree of sequence polymorphism available within the gene family. Here we show that physical separation of Hcr9 genes can be associated with elevated sequence divergence. Two diverged subclasses of Hcr9s could be defined. These are physically separated from each other, with members of one class exclusively residing at Northern Lights. One exceptional Hcr9 at Northern Lights carried sequence features specific for Hcr9s at other loci, suggesting a recent transfer of this gene by an interlocus recombination event. As members of diverged subclasses are brought into physical vicinity within a tandem repeat, a larger spectrum of sequence variants can potentially be generated by subsequent interhomologue sequence exchange.Biological surveillance systems for the detection of nonself molecules are essential for the defense of higher eukaryotes against pathogens. As pathogens evolve to evade these recognition systems, the generation of novel recognition specificities appears crucial for fitness and long-term survival of the host species. In plants, recognition of pathogens is mediated by resistance genes (R genes). The cloning of several different classes of R genes over the last few years enables investigation of their evolution. Certain R genes are members of multigene families (1-3), with distinct specificities encoded by individual family members. For example, the highly homologous L 6 and M genes of flax confer resistance toward races of flax rust carrying different avirulence genes (4). The tomato Cf-4 and Cf-9 genes for resistance to the leaf mould fungus Cladosporium fulvum belong to a large family of homologues of C. fulvum resistance gene Cf-9 (Hcr9s) (5-7). This gene family is ideally suited for the analysis of evolutionary mechanisms, because at least five functional R genes have been identified encoding at least four distinct recognition specificities (5, 8-10). Furthermore, genetical and physical mapping as well as sequence data of multiple Hcr9s are available (5-7, 9, 11). Different recognition specificities within a gene family are conceptually based on amino acid sequence polymorphism. In R genes which consist of leucine-rich repeats (LRRs; refs. 11 and 12), the highest degree of amino acid variability is found in predicted solvent exposed residues of the LRR parallel ␤-sheet structure, which implicated this domain in the determination of recognition spec...

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“…ITS regions are segments of ribosomal DNA occurring in many copies within a genome. On the one hand, the multicopy character of the marker facilitates amplification, but on the other hand, such genomic regions may be prone to deviations from expected patterns due to processes such as concerted evolution (Arnheim, 1983;Dover et al, 1993;Murti et al, 1994) and gene conversion. In the latter process, which is thought to have evolved as part of DNA repair mechanisms, sequence heterogeneity between two strands of different chromosomes is removed by recombination, and sequence information of one of the chromosomes is re-written according to the template of the other (Holliday, 1964).…”

Section: Its-rflpmentioning

confidence: 99%

Identifying hybridizing taxa within the Daphnia longispina species complex: a comparison of genetic methods and phenotypic approaches

et al. 2010

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Daphnia galeata Sars, D. longispina O. F. Müller and D. cucullata Sars (Crustacea: Cladocera) are closely related species which often produce interspecific hybrids in natural populations. Several marker systems are available for taxon determination in this hybridizing complex, but their performance and reliability has not been systematically assessed. We compared results from identifications by three molecular methods. More than 1,200 individuals from 10 localities in the Czech Republic were identified as parental species or hybrids by allozyme electrophoresis and the analysis of the restriction fragment length polymorphism of the internal transcribed spacer (ITS-RFLP); over 440 of them were additionally analyzed and identified by 12 microsatellite loci. Identification by microsatellite markers corresponded well with allozyme analyses. However, consistent discrepancies between ITS-RFLP and other markers were observed in two out of 10 studied localities. Although some marker discrepancies may have been caused by occasional recent introgression, consistent deviations between ITS-RFLP and other markers suggest a long-term maintenance of introgressed alleles. These results warn against its use as a sole identification method in field studies. Additionally, we quantitatively evaluated the discriminatory power of geometric morphometric (elliptic Fourier) analysis of body shapes based on photos of over 1,300 individuals pre-classified by allozyme markers. Furthermore, a randomly selected subset of 240 individuals was independently determined from photos by several experts. Despite a tendency for morphological divergence among parental Daphnia species, some taxa (especially D. galeata, D. longispina, and their hybrids) substantially overlapped in their body shapes. This was reflected in different

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[38] Detection and quantification of concerted evolution and molecular drive

Cited by 60 publications

References 28 publications

Evolution of the chromosomal location of rDNA genes in two Drosophila species subgroups: ananassae and melanogaster

Evolution of the chromosomal location of rDNA genes in two Drosophila species subgroups: ananassae and melanogaster

Recombination between diverged clusters of the tomato Cf-9 plant disease resistance gene family

Identifying hybridizing taxa within the Daphnia longispina species complex: a comparison of genetic methods and phenotypic approaches

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