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Variation in the strength of DNA strand asymmetry in Buchnera aphidicola
Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Department of Evolution, Genomics and Systematics.
Article in journal (Refereed) Submitted
URN: urn:nbn:se:uu:diva-93291OAI: oai:DiVA.org:uu-93291DiVA: diva2:166728
Available from: 2005-09-01 Created: 2005-09-01Bibliographically approved
In thesis
1. Genome Evolution in Maternally Inherited Insect Endosymbionts
Open this publication in new window or tab >>Genome Evolution in Maternally Inherited Insect Endosymbionts
2005 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Symbiosis is a widely common phenomenon in nature and has undoubtedly contributed to the evolution of all organisms on earth. Symbiotic associations can be of varying character, such as parasitic or mutualistic, but all imply a close relationship. To study the evolution of genomes of insect endosymbionts, we have sequenced the genomes of the mutualist Buchnera aphidicola from the aphid Schizaphis graminum (Sg) and the reproductive manipulator Wolbachia pipientis strain wRi from Drosophila simulans that show strikingly different evolutionary patterns.

The comparison between the genome of B.aphidicola (Sg) and the genome of B.aphidicola from the aphid Acyrthosiphon pisum (Ap), that are believed to have diverged 50 million years ago, revealed a perfect gene order conservation and loss of only 14 genes in either of the lineages. In contrast, the rate of nucleotide turnover is very fast probably due to relaxed selection and loss of DNA repair genes. The genomic stasis observed in Buchnera was attributed to the loss of repeats and of the gene recA.

In striking contrast to the genomes of B.aphidicola, a vast amount of repeats were found in the genome sequence of W.pipientis strain wMel. The comparison between the genomes of W.pipientis strain wRi and W.pipientis strain wMel shows that a lot of rearrangements have occurred since their divergence. The massive amount of repeats might stem from relaxed selection pressure but possibly also from selection to create variability via recombination.

Comparisons between pairs of genomes from closely related bacteria showed that the stability of gene order and content is connected to an intracellular lifestyle and indicated that homologous recombination between repeats is an important mechanisms for causing intrachromosomal rearrangements. Our studies show that the lifestyle of a bacterium to a great extent shapes the evolution of their genetic material and future capabilities to adapt to new environments.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2005. 54 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 75
Biology, Biologi
National Category
Biological Sciences
urn:nbn:se:uu:diva-5885 (URN)91-554-6299-5 (ISBN)
Public defence
2005-09-22, Lindahlsalen, EBC, Uppsala, 10:00
Available from: 2005-09-01 Created: 2005-09-01Bibliographically approved

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