Journal Article

Short- and Long-term Evolutionary Dynamics of Bacterial Insertion Sequences: Insights from <i>Wolbachia</i> Endosymbionts

Nicolas Cerveau, Sébastien Leclercq, Elodie Leroy, Didier Bouchon and Richard Cordaux

in Genome Biology and Evolution

Published on behalf of Society for Molecular Biology and Evolution

Volume 3, issue , pages 1175-1186
Published in print January 2011 |
Published online September 2011 | e-ISSN: 1759-6653 | DOI: https://dx.doi.org/10.1093/gbe/evr096

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Transposable elements (TE) are one of the major driving forces of genome evolution, raising the question of the long-term dynamics underlying their evolutionary success. Long-term TE evolution can readily be reconstructed in eukaryotes, thanks to many degraded copies constituting genomic fossil records of past TE proliferations. By contrast, bacterial genomes usually experience high sequence turnover and short TE retention times, thereby obscuring ancient TE evolutionary patterns. We found that Wolbachia bacterial genomes contain 52–171 insertion sequence (IS) TEs. IS account for 11% of Wolbachia wRi, which is one of the highest IS genomic coverage reported in prokaryotes to date. We show that many IS groups are currently expanding in various Wolbachia genomes and that IS horizontal transfers are frequent among strains, which can explain the apparent synchronicity of these IS proliferations. Remarkably, >70% of Wolbachia IS are nonfunctional. They constitute an unusual bacterial IS genomic fossil record providing direct empirical evidence for a long-term IS evolutionary dynamics following successive periods of intense transpositional activity. Our results show that comprehensive IS annotations have the potential to provide new insights into prokaryote TE evolution and, more generally, prokaryote genome evolution. Indeed, the identification of an important IS genomic fossil record in Wolbachia demonstrates that IS elements are not always of recent origin, contrary to the conventional view of TE evolution in prokaryote genomes. Our results also raise the question whether the abundance of IS fossils is specific to Wolbachia or it may be a general, albeit overlooked, feature of prokaryote genomes.

Keywords: insertion sequence; transposable element; evolutionary dynamics; prokaryote; Wolbachia; molecular palaeontology

Journal Article.  7371 words.  Illustrated.

Subjects: Bioinformatics and Computational Biology ; Evolutionary Biology ; Genetics and Genomics

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