Journal Article

Genomic evidence for ameiotic evolution in the bdelloid rotifer Adineta vaga

This work was supported by Genoscope-CES (where most of the sequencing was performed), by US National Science Foundation grants MCB-0821956 and MCB-1121334 to I.A., by German Research Foundation grant HA 5163/2-1 to O.H., by grant 11.G34.31.0008 from the Ministry of Education and Science of the Russian Federation to A.S.K., by grant NSF CAREER number 0644282 to M.K., by US National Science Foundation grant MCB-0923676 to D.B.M.W., by FRFC grant 2.4.655.09.F from the Belgian Fonds National de la Recherche Scientifique (FNRS) and a start-up grant from the University of Namur to K.V.D.; J.F.F. and K.V.D. thank also J.-P. Descy (University of Namur) for funding support, Architecture et fonction des macromolécules biologiques (AFMB) ; Institut National de la Recherche Agronomique (INRA)-Aix Marseille Université (AMU)-Centre National de la Recherche Scientifique (CNRS), Rocha, Martine Da, Bast, Jens, Institut Sophia Agrobiotech (ISA) ; Institut National de la Recherche Agronomique (INRA)-Université

2013

Overview

Loss of sexual reproduction is considered an evolutionary dead end for metazoans, but bdelloid rotifers challenge this view as they appear to have persisted asexually for millions of years1. Neither male sex organs nor meiosis have ever been observed in these microscopic animals: oocytes are formed through mitotic divisions, with no reduction of chromosome number and no indication of chromosome pairing2. However, current evidence does not exclude that they may engage in sex on rare, cryptic occasions. Here we report the genome of a bdelloid rotifer, Adineta vaga (Davis, 1873)3, and show that its structure is incompatible with conventional meiosis. At gene scale, the genome of A. vaga is tetraploid and comprises both anciently duplicated segments and less divergent allelic regions. However, in contrast to sexual species, the allelic regions are rearranged and sometimes even found on the same chromosome. Such structure does not allow meiotic pairing; instead, we find abundant evidence of gene conversion, which may limit the accumulation of deleterious mutations in the absence of meiosis. Gene families involved in resistance to oxidation, carbohydrate metabolism and defence against transposons are significantly expanded, which may explain why transposable elements cover only 3% of the assembled sequence. Furthermore, 8% of the genes are likely to be of non-metazoan origin and were probably acquired horizontally. This apparent convergence between bdelloids and prokaryotes sheds new light on the evolutionary significance of sex.

• Publisher: Nature Publishing Group,CCSD,Nature Publishing Group UK
• Subject: 631/181/2474 / 631/208/182 / 631/208/212/2304 / Adineta vaga / Animals / Bdelloidea / Biochemistry, Molecular Biology / Biological Evolution / Deoxyribonucleic acid / DNA / DNA repair / Evolution / Evolutionary genetics / Gene Conversion - genetics / Gene Transfer, Horizontal - genetics / Genes / Genetic aspects / Genetics & genetic processes / Genome - genetics / Genomics / Génétique & processus génétiques / Humanities and Social Sciences / letter / Life Sciences / Meiosis / Meiosis - genetics / Metazoa / Models, Biological / multidisciplinary / Mutation / Observations / Reproduction / Reproduction, Asexual - genetics / Rotifera / Rotifera - genetics / Science / Sciences du vivant / Tetraploidy / Vaga / Zoologie / Zoology
• ISBN: 0003233161000