L31 Transposons of Hexacorallia: Distribution, Diversity, and Evolution

Abstract—

Transposable elements (TEs) of eukaryotes—retrotransposons and DNA transposons—are nucleotide sequences that can move from locus to locus of the genome, as well as between the genomes of different organisms. L31 DNA transposons are an ancient and diverse group belonging to the large IS630/Tc1/mariner group. L31 transposons are not widespread and are present in a limited number of taxa. In addition to the sequence encoding the DDE/D transposase, L31 transposons carry another ORF (ORF2). Detailed analysis of L31 elements in the genomes of six-rayed corals has provided detailed information on the distribution, diversity, and structure of the elements. Two large groups, L31-duo and L31-uno, were identified, differing in both catalytic domain pattern and structure. As a result of reconstruction of the evolution of L31 transposons, it was suggested that six-rayed corals received L31 transposons from bivalves. The split-off group L31-uno may have been obtained by mollusks as a result of horizontal transfer from corals. Studies of TE distribution and diversity in marine invertebrates will contribute to a better understanding of the evolutionary processes of TEs and their role in the evolutionary history of species.