The influence of transposable elements on genome size

Genome size displays an important variability between species without any direct link to complexity. This paradox, so-called "C value paradox", now becomes understood as resulting from a differential abundance of numerous repeated sequences, among which transposable elements. Genomes indeed contain a important proportion of such sequences (95 % of DNA in man, about 45 % of which are transposable elements, up to 99 % of DNA in some plants). While most investigations until now are focalized on genes or coding sequences, which thus represent a small part of the genome, more attention now is dedicated on so-called non-coding sequences. Transposable elements, which are capable of moving around in genomes, inducing mutations, chromosomal rearrangements, gene expression regulations, thus appear as major actors in diversity and evolution. We present here a brief review of the most prominent acquisition in this expanding domain.