AUTHOR=Inoue Yusuke , Takeda Hiroyuki 

TITLE=Teratorn and its relatives – a cross-point of distinct mobile elements, transposons and viruses

JOURNAL=Frontiers in Veterinary Science

VOLUME=10

YEAR=2023

URL=https://www.frontiersin.org/journals/veterinary-science/articles/10.3389/fvets.2023.1158023

DOI=10.3389/fvets.2023.1158023

ISSN=2297-1769

ABSTRACT=<p>Mobile genetic elements (e.g., transposable elements and plasmids) and viruses display significant diversity with various life cycles, but how this diversity emerges remains obscure. We previously reported a novel and giant (180 kb long) mobile element, <italic>Teratorn</italic>, originally identified in the genome of medaka, <italic>Oryzias latipes</italic>. <italic>Teratorn</italic> is a composite DNA transposon created by a fusion of a <italic>piggyBac</italic>-like DNA transposon (<italic>piggyBac</italic>) and a novel herpesvirus of the <italic>Alloherpesviridae</italic> family. Genomic survey revealed that <italic>Teratorn</italic>-like herpesviruses are widely distributed among teleost genomes, the majority of which are also fused with <italic>piggyBac,</italic> suggesting that fusion with <italic>piggyBac</italic> is a trigger for the life-cycle shift of authentic herpesviruses to an intragenomic parasite. Thus, <italic>Teratorn</italic>-like herpesvirus provides a clear example of how novel mobile elements emerge, that is to say, the creation of diversity. In this review, we discuss the unique sequence and life-cycle characteristics of <italic>Teratorn</italic>, followed by the evolutionary process of <italic>piggyBac</italic>-herpesvirus fusion based on the distribution of <italic>Teratorn</italic>-like herpesviruses (relatives) among teleosts. Finally, we provide other examples of evolutionary associations between different classes of elements and propose that recombination could be a driving force generating novel mobile elements.</p>