Domestication of PIF transposable elements transposases as regulatory proteins in Drosophila melanogaster

Abstract

Transposable elements (TEs) are genetic units that are able to move and amplify within a host genome. As a result of their activities, TE insertions can cause disruptions of gene functions and ectopic recombination producing deleterious effects in the host and thus they are also referred to as selfish elements. The machineries that TEs harbor that facilitate their transposition have been shown to be co-opted by the host for their own benefit through a process called molecular domestication. In the first chapter, we review examples that show that TE proteins are domesticated as an adaptation to evolutionary conflicts. We provide evidence for TE proteins domestication through conflicts between host-pathogen, mother-embryo, host-TE, and potentially as a result of centromere drive. We also argue that as long as all the hallmarks of a TE are present, they remain opportunistic and could not be considered domesticated. In the two other chapters, we focus on identifying functions of domesticated transposase from PIF/Harbinger DNA TE in D. melanogaster. These PIF domesticated genes are named Drosophila PIF Like Genes (DPLGs). There are four DPLGs in D. melanogaster and all of these genes are old, under purifying selection, and arose though independent domestication events. We show that DPLGs are domesticated as regulatory proteins and a subset of these genes are involved in neuronal and gonadal functions, and affect the viability and survival of D. melanogaster. We also provide evidence for functional overlap of these independently domesticated PIF transposase providing support to the model that domestication of transposase promotes domestication of related transposases.