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

Abstract

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.

Detecting de novo mitochondrial mutations in angiosperms with highly divergent evolutionary rates

“…In contrast, species such as S. noctiflora and S. conica represent lineages (sections Elisanthe and Conoimorpha, respectively) that are within the same subgenus as section Melandrium but have highly divergent mtDNA sequence. These large differences among close relatives in Silene have enabled comparative approaches to investigate the evolutionary consequences of accelerated substitution rates for mitochondrial genome architecture (SLOAN et al 2012a), RNA editing , mitonuclear coevolution HAVIRD et al 2015;HAVIRD et al 2017), and mitochondrial physiology (HAVIRD et al 2019;WEAVER et al 2020). Notably, accelerated species such as S. noctiflora and S. conica also exhibit massively expanded mitochondrial genomes that have been fragmented into dozens of circularly mapping chromosomes (SLOAN et al 2012a).…”