Analysis of transposable elements expressed in the gonads of the siberian sturgeon

Abstract

Transposable elements (TEs) are mobile and repeated sequences that are major factors of diversity and evolution in genomes. We report here through the analysis of gonad transcriptomes of the Siberian sturgeon Acipenser baerii, a nonteleost ray-finned fish, that sturgeon genomes contain many families of TEs, which are expressed in gonads and might be involved in the evolution of this divergent fish lineage. The high diversity of TEs observed in sturgeons, which is also found in teleost fish, coelacanth, and amphibians but not in birds and mammals, strongly supports that many TE families were present in ancestral vertebrate genomes. Two types of transposable elements potentially differing in their evolutionary dynamics have been further characterized: DIRS-like retrotransposons, with a single lineage mainly transmitted vertically, and Tc1/mariner DNA transposons, with multiple lineages and the possible involvement of horizontal transfer. This first global analysis is a new step toward the understanding of TE evolution and evolutionary impact in non-teleost ray-finned fish and will help to annotate the upcoming sequences of the large sturgeon genomes.