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          Institute: MPI für molekulare Genetik     Collection: Department of Vertebrate Genomics     Display Documents

ID: 230182.0, MPI für molekulare Genetik / Department of Vertebrate Genomics
Hypervariable and highly divergent intron–exon organizations in the chordate Oikopleura dioica
Authors:Edvardsen, Rolf B.; Lerat, Emmanuelle; Maeland, Anne Dorthea; Flåt, Mette; Tewari, Rita; Jensen, Marit F.; Lehrach, Hans; Reinhardt, Richard; Seo, Hee-Chan; Chourrou, Daniel
Date of Publication (YYYY-MM-DD):2004-10
Title of Journal:Journal of Molecular Evolution
Journal Abbrev.:J Mol Evol
Issue / Number:4
Start Page:448
End Page:457
Copyright:© Springer 2004. Part of Springer Science + Business Media
Review Status:not specified
Audience:Experts Only
Abstract / Description:Oikopleura dioica is a pelagic tunicate with a very small genome and a very short life cycle. In order to investigate the intron–exon organizations in Oikopleura, we have isolated and characterized ribosomal protein EF-1agr, Hox, and agr-tubulin genes. Their intron positions have been compared with those of the same genes from various invertebrates and vertebrates, including four species with entirely sequenced genomes. Oikopleura genes, like Caenorhabditis genes, have introns at a large number of nonconserved positions, which must originate from late insertions or intron sliding of ancient insertions. Both species exhibit hypervariable intron–exon organization within their agr-tubulin gene family. This is due to localization of most nonconserved intron positions in single members of this gene family. The hypervariability and divergence of intron positions in Oikopleura and Caenorhabditis may be related to the predominance of short introns, the processing of which is not very dependent upon the exonic environment compared to large introns. Also, both species have an undermethylated genome, and the control of methylation-induced point mutations imposes a control on exon size, at least in vertebrate genes. That introns placed at such variable positions in Oikopleura or C. elegans may serve a specific purpose is not easy to infer from our current knowledge and hypotheses on intron functions. We propose that new introns are retained in species with very short life cycles, because illegitimate exchanges including gene conversion are repressed. We also speculate that introns placed at gene-specific positions may contribute to suppressing these exchanges and thereby favor their own persistence.
Free Keywords:Intron; Conversion; agr-Tubulin; Hox; Ribosomal protein; Urochordate; Oikopleura
External Publication Status:published
Document Type:Article
Communicated by:Hans Lehrach
Affiliations:MPI für molekulare Genetik
External Affiliations:Sars Centre for Marine Molecular Biology, Bergen High Technology Centre, Thormoehlensgt. 55, 5020, Bergen, Norway;
Laboratoire de Biométrie et Biologie Evolutive, Université Lyon 1, 16 rue Dubois, 69622 Villeurbanne Cedex, France
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