Evolution of Skipper (SK), a family of DD34E/Tc1 transposons, in animals

Abstract High diversity and differential evolution profiles have been observed for DD34E/Tc1 transposons; several families originating from these groups, such as DD34E/ZB, DD34E/SB, DD35E/TR, DD36E/IC, and DD38E/IT, have been well defined. Even though Frisky, Tiang, Tsessebe, and Topi transposons have been identified in Anopheles gambiae, their taxonomic distribution and phylogenetic relationship in nature remain largely unknown. The evolutionary profiles of Frisky, Tiang, Tsessebe, and Topi homology transposons were investigated in the current study. In total, 254 homology transposons of Frisky, Tiang, Hob, Tsessebe, and Topi were obtained in 200 species by data mining. The phylogenetic tree revealed that these transposons were classified into five main clades (Frisky, Tiang, Hob, Tsessebe, and Topi) forming a monophyletic clade with 98% bootstrap support, belonging to the DD34E/Tc1 group, and named as Skipper (SK). SK transposons show a wide distribution in animals; however, differential taxonomic distribution patterns were observed for the subfamilies of Frisky, Tiang, Hob, Tsessebe, and Topi; extensive invasion of Frisky in animals was found, whereas Tiang, Hob, Tsessebe, and Topi were mainly detected in Diptera. SK elements share a similar structural organization and display high sequence identities across subfamilies. Evolutionary dynamics and structural analysis revealed that SKs in some species, such as Bombyx mori, Lordiphosa magnipectinata, Carassius gibelio, Triplophysa dalaica, and Silurus glanis, have recently evolved and present as intact copies, indicating that SKs in these genomes may be active. Together, these observations improve our understanding of the diversity of DD34E/Tc1 transposons and their impacts on genome evolution in animals.