High mitochondrial mutation rates in Silene are associated with nuclear-mediated changes in mitochondrial physiology

Mitochondrial (mt) respiration depends on proteins encoded both by the mitochondrial and nuclear genomes. Variation in mt-DNA mutation rates exists across eukaryotes, although the functional consequences of elevated mt mutation rates in some lineages remain underexplored. In the angiosperm genus Silene, closely related, ecologically similar species have either 'fast' or 'slow' mt-DNA mutation rates. Here, we investigated the functional consequences of elevated mt-DNA mutation rates on mt respiration profiles of Silene mitochondria. Overall levels of respiration were similar among Species. Fast species had lower respiration efficiency than slow species and relied up to 48% more on nuclear-encoded respiratory enzymes alternative oxidase (AOX) and accessory dehydrogenases (DHex), which participate in stress responses in plants. However, not all fast species showed these trends. Respiratory profiles of some enzymes were correlated, most notably AOX and DHex. We conclude that subtle differences in mt physiology among Silene lineages with dramatically different mt mutation rates may underly similar phenotypes at higher levels of biological organization, betraying the consequences of mt mutations.

Keywords: alternative oxidase; cytonuclear coevolution; flux control factor; mito–nuclear interactions; oxidative phosphorylation.