Meeting Abstract
Eukaryotes are made up of two different genomes that must interact with one another precisely and mitonuclear coevolution is predicted to maintain these interactions. Nuclear compensation, a form of mitonuclear coevolution, is often assumed, but few have directly tested for it. We tested the hypothesis that positive selection in nuclear-encoded genes is a response to deleterious mutations occurring in mitochondrial (mt) genes. To test predictions stemming from this hypothesis, publicly available sequence and structural data were gathered from across mammals for the oxidative phosphorylation enzyme cytochrome c oxidase (COX). We tested whether nuclear-encoded sites under positive selection were overrepresented at mt contact sites, as predicted by nuclear compensation. While nuclear genes had a greater number of positively selected sites than mt genes, sites of positive selection did not particularly contact mt-encoded sites. We also tested if mt mutations are deleterious when expressed alongside novel nuclear genes. To evaluate this, structural information was used to model mitonuclear hybrids to examine the stability of these hybrids compared with “wildtype” structures where mt genes are expressed against their native nuclear counterparts. Under nuclear compensation, structural stability should decrease without a compensatory nuclear component. Preliminary results suggest stability is similar between native “matched” structures and the “mismatched” structures of hybrids. Despite previous studies showing strong support for mitonuclear coevolution, these preliminary results suggest nuclear compensation may be difficult to detect at the molecular level across taxa. Future work will address whether individual nuclear changes tend to follow mt changes in space and time, as predicted by nuclear compensation.
