Birth, School, Work, Death, and Resurrection: The Life Stages and Dynamics of Transposable Element Proliferation.

Justin P Blumenstiel

doi:10.3390/genes10050336

Abstract

Transposable elements (TEs) can be maintained in sexually reproducing species even if they are harmful. However, the evolutionary strategies that TEs employ during proliferation can modulate their impact. In this review, I outline the different life stages of a TE lineage, from birth to proliferation to extinction. Through their interactions with the host, TEs can exploit diverse strategies that range from long-term coexistence to recurrent movement across species boundaries by horizontal transfer. TEs can also engage in a poorly understood phenomenon of TE resurrection, where TE lineages can apparently go extinct, only to proliferate again. By determining how this is possible, we may obtain new insights into the evolutionary dynamics of TEs and how they shape the genomes of their hosts.

Highlights

Transposable elements (TEs) can be maintained in sexually reproducing species even if they are harmful
How can such parasites spread if they are harmful? Alleles that are harmful are expected to be lost, but transposable elements exist in essentially all forms of life
The persistence of TEs is explained by the fact that sexual reproduction allows TEs to spread even if their net effect is a reduction in host fitness

Summary

Introduction

“And he that was dead came forth, bound hand and foot with graveclothes.” John 11:44. Transposable elements must walk a fine line between a sufficient rate of proliferation and one that is not so great that TEs become too burdened by the harmful effects that they impose The nature of this tension depends on the degree of intimacy with the host genome and is illuminated by considering the moment when a TE and the host genome first meet. A single TE insertion allele can be considered fixed if there are no non-insertion variants segregating in the population at that locus For both a new beneficial allele and a new transposable element, the fixation (or establishment) probabilities do not depend much on the population size since the dynamics of stochastic loss by drift when the novel variant first appears are the same whether the population size is one million or one trillion. I will argue that TEs that show this pattern—I will designate them Lazarus elements—may highlight interesting aspects of TE biology and host interaction

Long-Lasting Relationships

Horizontal Transfer

Extinction

Resurrection