EVOLUTION
Long-term evolution of transposable elements

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*Laboratoire Évolution, Génomes, et Spéciation, Avenue de la Terrasse, Bâtiment 13, 91198 Gif-sur-Yvette Cedex, France; and
Faculté des Sciences d'Orsay, IFR 115, Génome, Structure, Fonction, Évolution, Université Paris Sud, 91405 Orsay Cedex, France
Edited by Daniel L. Hartl, Harvard University, Cambridge, MA, and approved October 15, 2007 (received for review June 4, 2007)
Abstract
Transposable elements are often considered parasitic DNA sequences, able to invade the genome of their host thanks to their self-replicating ability. This colonization process has been extensively studied, both theoretically and experimentally, but their long-term coevolution with the genomes is still poorly understood. In this work, we aim to challenge previous population genetics models by considering features of transposable elements as quantitative, rather than discrete, variables. We also describe more realistic transposable element dynamics by accounting for the variability of the insertion effect, from deleterious to adaptive, as well as mutations leading to a loss of transposition activity and to nonautonomous copies. Individual-based simulations of the behavior of a transposable-element family over several thousand generations show different ways in which active or inactive copies can be maintained for a very long time. Results reveal an unexpected impact of genetic drift on the "junk DNA" content of the genome and strongly question the likelihood of the sustainable long-term stable transposition-selection equilibrium on which numerous previous works were based.
genome evolution | molecular domestication | population genetics
Author contributions: A.L.R. and P.C. designed research; A.L.R. and T.S.B. performed research; A.L.R. and T.S.B. analyzed data; and A.L.R., T.S.B., and P.C. wrote the paper.
Present address: Center for Ecological and Evolutionary Synthesis, University of Oslo, Oslo 0316, Norway.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
To whom correspondence should be addressed. E-mail: capy{at}legs.cnrs-gif.fr
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