Transposable Element Domestication As an Adaptation to Evolutionary Conflicts

Abstract

Transposable elements (TEs) are selfish genetic units that typically encode proteins that enable their proliferation in the genome and spread across individual hosts. Here we review a growing number of studies that suggest that TE proteins have often been coopted or ‘domesticated’ by their host as adaptations to a variety of evolutionary conflicts. In particular, TE-derived proteins have been recurrently repurposed as part of defense systems that protect prokaryotes and eukaryotes against the proliferation of infectious or invasive agents, including viruses and TEs themselves. We argue that the domestication of TE proteins may often be the only evolutionary path toward the mitigation of the cost incurred by their own selfish activities.

Has gene expression neofunctionalization in the fire ant antennae contributed to queen discrimination behavior?

“…This general expression pattern could be explained either by supergene allele‐specific gene regulation or by copy number variation of TEs between SB and Sb genomes. The general consensus is that most TE insertions are neutral or slightly deleterious; however, TEs that cause adaptive phenotypes have been described in many organisms, including insects (van't Hof et al ; Jangam, Feschotte, Betrán, ; Li et al ). Thus, it would be interesting to determine whether the differential expression of these TEs is just nonfunctional noise or adaptive gene regulation, especially for those associated with social form.…”

The Mobilome of Reptiles: Evolution, Structure, and Function

“…There are now numerous examples of exaptation in vertebrates, and TEs have been shown to be a source of novel regulatory sequence (promoters or enhancers), of coding sequences (new genes or exons), of binding sites, and of noncoding RNAs (miRNAs and lncRNAs) [reviewed in Warren et al, 2015]. In fact, the exaptation of TEs has had some profound impacts on the evolution of networks as well as on the evolution of some important functions, such as immunity and neurotransmission [Feschotte, 2008;Jangam et al, 2017;Pastuzyn et al, 2018]. However, the vast majority of examples of exaptation in vertebrates have been found in mammals [Warren et al, 2015], arguably the best-studied vertebrate group in the field of comparative genomics.…”

Evolutionary origins and impacts of genome architecture in ciliates

“…Interestingly, a germline‐limited PiggyBac transposase has been identified in Tetrahymena and is required for precise excision of germline‐limited DNA, whereas the somatic PiggyBac , which is responsible for the bulk of IES excision, does so at variable boundaries . These data from ciliates are yet another example of how TE proteins, regardless of their domestication status, have often been co‐opted into numerous pathways as adaptations to a variety of evolutionary conflicts spanning the tree of life …”

“…From these duplicated loci, combinatorial rearrangements can take place during development (guided by the large pool of redundant pointer sequences), generating identical somatic sequences (Fig. A) . Over time, decay/divergence of redundant pointers and/or identical coding regions could become fixed, with negligible impacts on fitness (Fig.…”

“…41 These data from ciliates are yet another example of how TE proteins, regardless of their domestication status, have often been co-opted into numerous pathways as adaptations to a variety of evolutionary conflicts spanning the tree of life. 37,[41][42][43]…”