Abstract
One of the most unexpected insights that followed from the completion of the human genome a decade ago was that more than half of our DNA is derived from transposable elements (TEs). Due to advances in high throughput sequencing technologies it is now clear that TEs comprise the largest molecular class within most metazoan genomes. TEs, once categorised as "junk DNA", are now known to influence genomic structure and function by increasing the coding and non-coding genetic repertoire of the host. In this way TEs are key elements that stimulate the evolution of metazoan genomes. This review highlights several lines of TE research including the horizontal transfer of TEs through host-parasite interactions, the vertical maintenance of TEs over long periods of evolutionary time, and the direct role that TEs have played in generating morphological novelty.
Highlights
One of the most unexpected insights that followed from the completion of the human genome a decade ago was that more than half of our distinct from the original (DNA) is derived from transposable elements (TEs)
Classical examples of horizontally transferred TEs between metazoans include the P-elements in Drosophila [48], the Mariner transposons in insects [49], and the chromoviruses, the oldest and largest lineage of Long terminal repeat elements (LTRs) elements, which were horizontally transferred into the genome of the ancestor of gnathostomes [50]
While horizontally transferred DNA transposons can provide information concerning the ecological interactions of host species, retroposons are usually vertically inherited and can provide information concerning the phylogenetic relationships of species
Summary
During her career Barbara McClintock discovered and described transposable elements (TEs), a class of mobile genetic elements often abundantly distributed throughout the genomes of eukaryotic organisms [1–4; reviewed in 5]. At the time, her findings were in line with the popular theory of selfish. Following the completion of the first metazoan genome in 1998 using 'first generation' technologies [18], draft genomes of "non-model" organisms are released with increasing annual frequency With this flood of sequence data has come the need to develop bioinformatic tools designed to detect and characterise TEs [19,20,21]. With the sequencing of more phylogenetically representative taxa from the metazoan tree of life for evolutionary studies [39,40,41], and the corresponding development of tools to annotate these datasets [42,43,44], it can be expected that in the near future we will come to appreciate that the evolutionary histories and functions of TEs are as complex and diverse as the biological populations bearing them
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