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TEs and intra/inter species variation (Coord. M Fablet)

Transposable element dynamics and variability between and within species


Transposable elements are found in the genomes of virtually all living organisms, but their proportions and activities vary greatly between and within species. In order to understand TE dynamics, we focus on wild-type strains of Drosophila melanogaster and D. simulans, two closely related species which have a three-fold difference in their TE content. In particular, we explore variability in epigenetic TE regulation in relationship to variability in TE dynamics and content. One of the major defense mechanisms against TEs in Drosophila is an RNA interference machinery based on a particular class of small RNAs : piwi-interacting small RNAs (piRNAs). We are currently investigating the link between differences in TE and piRNA content between different populations and species of Drosophila using available genomes and NGS data. We focus on tirant, an endogenous retrovirus which activity varies between wild-type strains of D.simulans : while tirant is either inactive and embedded in heterochromatin in most strains, or it displays post-transcriptionaly silenced euchromatic copies, we identified one strain in which tirant behaves as an endogenous retrovirus and increases in copy number. We use this system of three-type wild-type strains to decipher the dynamics of tirant, with an emphasis on the regulation by piRNAs.

People involved : M. Fablet, C. Vieira,L. Modolo

Collaborators :
Abdou Akkouche et Séverine Chambeyron (Institute of Human Genetics,
Montpellier, France), Christophe Terzian (Infections et Rétrovirus
Endogènes, Lyon, France)

Transposable elements and hybrids incompatibility




It has been postulated in the literature that TEs may be some how implicated in hybrid incompatibility, or that they are associated with speciation events. At the intra species level, this was typically shown in the case of the hybrid digenesis in Drosophila, in which several different TEs may be involved. We are addressing this question with two different models. One consists in the analysis of hybrids from D. mojavensis and D. arizonae. These two species diverged less than 1 Mya and it is still possible to produce hybrids in the laboratory. We are analyzing the dynamics of TEs in the hybrids versus the parental lines. The other deals with a lower level of divergence using intra-specific hybrids between distinct natural populations of D. melanogaster or D. simulans. This projet is funded by the ANR ExHyb. New students are welcome to work on the project. Please contact Cristina Vieira.

People involved : C. Vieira, H. Lopez
Collaborators : Vincent Lacroix (LBBE), Claudia Carareto and Elias Carnelossi (Department of Biology ; UNESP—São Paulo State University ; São Paulo, Brazil)