Tana1, a new putatively active Tc1-like transposable element in the genome of sturgeons.

Abstract We report the discovery of a new putatively active Tc 1-like transposable element ( Tana 1) in the genome of sturgeons, an ancient group of fish considered as living fossils. The complete sequence of Tana 1 was first characterized in the 454-sequenced transcriptome of the Adriatic sturgeon ( Acipenser naccarii ) and then isolated from the genome of the same species and from 12 additional sturgeons including three genera of the Acipenseridae ( Acipenser , Huso , Scaphirhynchus ). The element has a total length of 1588 bp and presents inverted repeats of 210 bp, one of which partially overlapping the 3′ region of the transposase gene. The spacing of the DDE motif within the catalytic domain in Tana 1 is unique (DD38E) and indicates that Tana 1 can be considered as the first representative of a new Tc 1 subfamily. The integrity of the native form (with no premature termination codons within the transposase), the presence of all expected functional domains and its occurrence in the sturgeon transcriptome suggest a current or recent activity of Tana 1. The presence of Tana 1 in the genome of the 13 sturgeon species in our study points to an ancient origin of the element that existed before the split of the group 170 million years ago. The dissemination of Tana 1 across sturgeon genomes could be interpreted by postulating vertical transmission from an ancestral Tana 1 with a particularly slow evolutionary rate Horizontal transmission might have also played a role in the dissemination of Tana 1 as evidenced by the presence of a complete copy in the genome of Atlantic salmon. Vertical and horizontal transmission are not mutually exclusive and may have concurred in shaping the evolution of Tana 1.