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Inversions and adaptation to the plant toxin ouabain shape DNA sequence variation within and between chromosomal inversions of Drosophila subobscura.

Pegueroles C, Ferrés-Coy A, Martí-Solano M, Aquadro CF, Pascual M, Mestres F - Sci Rep (2016)

Bottom Line: Genetic differentiation was significant between inversions despite extensive recombination inside inverted regions, irrespective of gene distance to the inversion breakpoints.Surprisingly, the highest level of genetic differentiation between arrangements was found for the Atpα gene, which is located outside the O1 and O7 inversions.Similarities in the Atpα variants, conferring ouabain resistance in both arrangements, may be the result of convergent substitution and be favoured in response to selective pressures presumably related to the presence of plants containing ouabain in the geographic locations where both inversions are present.

View Article: PubMed Central - PubMed

Affiliation: Departament de Genètica and IRBio, Facultat de Biologia, Universitat de Barcelona, Barcelona 08028, Spain.

ABSTRACT
Adaptation is defined as an evolutionary process allowing organisms to succeed in certain habitats or conditions. Chromosomal inversions have the potential to be key in the adaptation processes, since they can contribute to the maintenance of favoured combinations of adaptive alleles through reduced recombination between individuals carrying different inversions. We have analysed six genes (Pif1A, Abi, Sqd, Yrt, Atpα and Fmr1), located inside and outside three inversions of the O chromosome in European populations of Drosophila subobscura. Genetic differentiation was significant between inversions despite extensive recombination inside inverted regions, irrespective of gene distance to the inversion breakpoints. Surprisingly, the highest level of genetic differentiation between arrangements was found for the Atpα gene, which is located outside the O1 and O7 inversions. Two derived unrelated arrangements (O3+4+1 and O3+4+7) are nearly fixed for several amino acid substitutions at the Atpα gene that have been described to confer resistance in other species to the cardenolide ouabain, a plant toxin capable of blocking ATPases. Similarities in the Atpα variants, conferring ouabain resistance in both arrangements, may be the result of convergent substitution and be favoured in response to selective pressures presumably related to the presence of plants containing ouabain in the geographic locations where both inversions are present.

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Mentions: Adaptation is a major evolutionary mechanism that allows organisms to live in certain habitats or conditions12. Prime evidence for adaptation is the maintenance and reproducibility of latitudinal clines in the frequency of chromosomal inversions observed in continuous populations of several species of drosophilids across continents3456. In particular, Drosophila subobscura has been studied extensively due to its abundant inversion polymorphism and its recent invasion of large areas of North and South America. The frequencies of most chromosomal inversions in D. subobscura are correlated with latitude in the Palearctic region. In addition, similar latitudinal clines were also detected in both colonized American regions, suggesting that the geographic distribution of its inversion polymorphism is adaptive and not a mere consequence of historic events378. The chromosomal arrangements of D. subobscura are formed by single and overlapped inversions that may differentially affect levels of nucleotide variability, since the overlapped inversions may effectively reduce recombination. Previous studies focused on chromosomal inversions located in the segment I of the O chromosome (Fig. 1) and the A chromosome910111213, but segment II of the O chromosome remains largely unexplored despite bearing some chromosomal inversions whose frequencies cycle seasonally and respond to acute environmental events14.


Inversions and adaptation to the plant toxin ouabain shape DNA sequence variation within and between chromosomal inversions of Drosophila subobscura.

Pegueroles C, Ferrés-Coy A, Martí-Solano M, Aquadro CF, Pascual M, Mestres F - Sci Rep (2016)

© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4815013&req=5

Mentions: Adaptation is a major evolutionary mechanism that allows organisms to live in certain habitats or conditions12. Prime evidence for adaptation is the maintenance and reproducibility of latitudinal clines in the frequency of chromosomal inversions observed in continuous populations of several species of drosophilids across continents3456. In particular, Drosophila subobscura has been studied extensively due to its abundant inversion polymorphism and its recent invasion of large areas of North and South America. The frequencies of most chromosomal inversions in D. subobscura are correlated with latitude in the Palearctic region. In addition, similar latitudinal clines were also detected in both colonized American regions, suggesting that the geographic distribution of its inversion polymorphism is adaptive and not a mere consequence of historic events378. The chromosomal arrangements of D. subobscura are formed by single and overlapped inversions that may differentially affect levels of nucleotide variability, since the overlapped inversions may effectively reduce recombination. Previous studies focused on chromosomal inversions located in the segment I of the O chromosome (Fig. 1) and the A chromosome910111213, but segment II of the O chromosome remains largely unexplored despite bearing some chromosomal inversions whose frequencies cycle seasonally and respond to acute environmental events14.

Bottom Line: Genetic differentiation was significant between inversions despite extensive recombination inside inverted regions, irrespective of gene distance to the inversion breakpoints.Surprisingly, the highest level of genetic differentiation between arrangements was found for the Atpα gene, which is located outside the O1 and O7 inversions.Similarities in the Atpα variants, conferring ouabain resistance in both arrangements, may be the result of convergent substitution and be favoured in response to selective pressures presumably related to the presence of plants containing ouabain in the geographic locations where both inversions are present.

View Article: PubMed Central - PubMed

Affiliation: Departament de Genètica and IRBio, Facultat de Biologia, Universitat de Barcelona, Barcelona 08028, Spain.

ABSTRACT
Adaptation is defined as an evolutionary process allowing organisms to succeed in certain habitats or conditions. Chromosomal inversions have the potential to be key in the adaptation processes, since they can contribute to the maintenance of favoured combinations of adaptive alleles through reduced recombination between individuals carrying different inversions. We have analysed six genes (Pif1A, Abi, Sqd, Yrt, Atpα and Fmr1), located inside and outside three inversions of the O chromosome in European populations of Drosophila subobscura. Genetic differentiation was significant between inversions despite extensive recombination inside inverted regions, irrespective of gene distance to the inversion breakpoints. Surprisingly, the highest level of genetic differentiation between arrangements was found for the Atpα gene, which is located outside the O1 and O7 inversions. Two derived unrelated arrangements (O3+4+1 and O3+4+7) are nearly fixed for several amino acid substitutions at the Atpα gene that have been described to confer resistance in other species to the cardenolide ouabain, a plant toxin capable of blocking ATPases. Similarities in the Atpα variants, conferring ouabain resistance in both arrangements, may be the result of convergent substitution and be favoured in response to selective pressures presumably related to the presence of plants containing ouabain in the geographic locations where both inversions are present.

No MeSH data available.


Related in: MedlinePlus