Characterization of autonomous families of Tc1/mariner transposons in neoteleost genomes.

We report the comprehensive analysis of Tc1/mariner transposons in six species of neoteleost (cod, tetraodon, fugu, medaka, stickleback, and tilapia) for which draft sequences are available. In total, 33 Tc1/mariner families were identified in these neoteleost genomes, with 3-7 families in each species. Thirty of these are in full length and designed as autonomous families, and were classified into the DD34E (Tc1) and DD×D (pogo) groups. The DD34E (Tc1) group was further classified into five clusters (Passport-like, SB-like, Frog Prince-like, Minos-like, and Bari-like). Within the genomes of cod, tetraodon, fugu, and stickleback, the Tc1/mariner DNA transposons exhibit very low proliferation with <1% of genome. In contrast, medaka and tilapia display high accumulation of Tc1/mariner transposons with 2.91% and 5.09% of genome coverages, respectively. Divergence analysis revealed that most identified Tc1/mariner transposons have undergone one round of recent accumulation, followed by a decrease in activity. One family in stickleback (Tc1_6_Ga) exhibits a very recent and strong expansion, which suggests that this element is a very young invader and putatively active. The structural organization of these Tc1/mariner elements is also described. Generally, the Tc1/mariner transposons display a high diversity and varied abundance in the neoteleost genomes with current and recent activity.