Transposable elements and viruses as factors in adaptation and evolution: an expansion and strengthening of theTE‐Thrust hypothesis

Abstract

In addition to the strong divergent evolution and significant and episodic evolutionary transitions and speciation we previously attributed to TE-Thrust, we have expanded the hypothesis to more fully account for the contribution of viruses to TE-Thrust and evolution. The concept of symbiosis and holobiontic genomes is acknowledged, with particular emphasis placed on the creativity potential of the union of retroviral genomes with vertebrate genomes. Further expansions of the TE-Thrust hypothesis are proposed regarding a fuller account of horizontal transfer of TEs, the life cycle of TEs, and also, in the case of a mammalian innovation, the contributions of retroviruses to the functions of the placenta. The possibility of drift by TE families within isolated demes or disjunct populations, is acknowledged, and in addition, we suggest the possibility of horizontal transposon transfer into such subpopulations. “Adaptive potential” and “evolutionary potential” are proposed as the extremes of a continuum of “intra-genomic potential” due to TE-Thrust. Specific data is given, indicating “adaptive potential” being realized with regard to insecticide resistance, and other insect adaptations. In this regard, there is agreement between TE-Thrust and the concept of adaptation by a change in allele frequencies. Evidence on the realization of “evolutionary potential” is also presented, which is compatible with the known differential survivals, and radiations of lineages. Collectively, these data further suggest the possibility, or likelihood, of punctuated episodes of speciation events and evolutionary transitions, coinciding with, and heavily underpinned by, intermittent bursts of TE activity.

Accumulation of transposable elements inHoxgene clusters during adaptive radiation ofAnolislizards

“…through unequal crossing over), and thus impact gross genomic architecture [3]. While this may often be deleterious to individuals, the ability of TEs to bring about fast genomic changes might at times contribute to adaptation and diversification [4][5][6][7][8]. For example, TE activity may accelerate speciation by causing genomic incompatibilities between incipient species [9,10].…”

Regulatory roles of LINE-1-encoded reverse transcriptase in cancer onset and progression

“…A thought-provoking fact in this context is the total refractoriness of naked-mole rats to develop cancer [99]: strikingly, the genome of these rats has an unusually low content in retroelements (25%, compared to 40% and 45% of murine and human genomes, respectively) and, most importantly, none of their transposable element is viable [100]. It is tempting to attribute the amazing privilege of cancer resistance to the inactive state of the RT-mediated machinery.…”

Transposable Elements Activity is Positively Related to Rate of Speciation in Mammals

“…Furthermore, TEs have been key contributors to evolution (Biemont 2010; Oliver et al 2013; Kapusta et al 2017) and led the insurgences of the V(D)J system of acquired immunity (Kapitonov and Jurka 2005; Koonin and Krupovic 2014) and mammalian placenta (Lynch et al 2011). Given their huge impact on shaping genomes, TEs are also thought to influence differentiation (Huff et al 2016) and speciation as proposed by the Epi-Transposon (Zeh et al 2009), CArrier SubPopulation (Jurka et al 2011), and TE-Thrust (Oliver and Greene 2012) hypotheses.…”