Genomic evidence for ameiotic evolution in the bdelloid rotifer Adineta vaga

Jean François Flot, Boris Hespeels, Xiang Li, Benjamin Noel, Irina Arkhipova, Etienne G.J. Danchin, Andreas Hejnol, Bernard Henrissat, Romain Koszul, Jean Marc Aury, Valérie Barbe, Roxane Marie Barthélémy, Jens Bast, Georgii A. Bazykin, Olivier Chabrol, Arnaud Couloux, Martine Da Rocha, Corinne Da Silva, Eugene Gladyshev, Philippe GouretOskar Hallatschek, Bette Hecox-Lea, Karine Labadie, Benjamin Lejeune, Oliver Piskurek, Julie Poulain, Fernando Rodriguez, Joseph F. Ryan, Olga A. Vakhrusheva, Eric Wajnberg, Bénédicte Wirth, Irina Yushenova, Manolis Kellis, Alexey S. Kondrashov, David B.Mark Welch, Pierre Pontarotti, Jean Weissenbach, Patrick Wincker, Olivier Jaillon, Karine Van Doninck

Research output: Contribution to journalArticlepeer-review

245 Citations (Scopus)

Abstract

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 years. 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 pairing. 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), 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.

Original languageEnglish
Pages (from-to)453-457
Number of pages5
JournalNature
Volume500
Issue number7463
DOIs
Publication statusPublished - 2013
Externally publishedYes

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