ABSTRACT
Horizontal transfer of transposable elements (HTT) has been reported across many species and the impact of such events on genome structure and function has been well described. However, few studies have focused on reptilian genomes, especially HTT events in Testudines (turtles). Here, as a consequence of investigating the repetitive content of Malaclemys terrapin terrapin (Diamondback turtle) we found a high similarity DNA transposon, annotated in RepBase as hAT-6_XT, shared between other turtle species, ray-finned fishes, and a frog. hAT-6_XT was notably absent in reptilian taxa closely related to turtles, such as crocodiles and birds. Successful invasion of DNA transposons into new genomes requires the conservation of specific residues in the encoded transposase, and through structural analysis, these residues were identified indicating some retention of functional transposition activity. We document six recent independent HTT events of a DNA transposon in turtles, which are known to have a low genomic evolutionary rate and ancient repeats.
ABSTRACT
Accurate annotation of genes and transposable elements (TEs) is vital for understanding genomes, but current annotation pipelines often misannotate TEs as genes. This study reveals how the general transcription factor II-I repeat domain-containing protein 2 (GTF2IRD2) erroneously annotated DNA transposons in non-mammalian species, as it contains a 3' fused hAT transposase domain. We also demonstrate the generality of this problem by identifying misannotated TEs as genes in other vertebrate genomes. Such misannotations can lead to errors in phylogenetic analyses and wasted time for investigators. The study proposes adding a final TE-check to gene annotation pipelines to mitigate this problem.
