Horizontal Transfer and Evolutionary Profiles of Two DD34E Transposons ( and ) in Vertebrates.

Both ZeBrafish (), a recently identified DNA transposon in the zebrafish genome, and , a reconstructed transposon originally discovered in several fish species, are known to exhibit high transposition activity in vertebrate cells. Although a similar structural organization was observed for and transposons, the evolutionary profiles of their homologs in various species remain unknown. In the present study, we compared their taxonomic ranges, structural arrangements, sequence identities, evolution dynamics, and horizontal transfer occurrences in vertebrates. In total, 629 and 366 homologs were obtained and classified into four distinct clades, named , -like, and -like. They displayed narrow taxonomic distributions in eukaryotes, and were mostly found in vertebrates, Actinopterygii in particular tended to be the major reservoir hosts of these transposons. Similar structural features and high sequence identities were observed for transposons and transposase, notably homologous to the and elements. The genomic sequences that flank the and transposons in the genomes revealed highly conserved integration profiles with strong preferential integration into AT repeats. Both and transposons experienced horizontal transfer (HT) events, which were most common in Actinopterygii. Our current study helps to increase our understanding of the evolutionary properties and histories of and transposon families in animals.