bims-cytox1 2019-04-14 papers

Issue of 2019–04–14
two papers selected by
Gavin McStay, Staffordshire University

Proc Biol Sci. 2019 Feb 13. 286(1896): 20182708

Metabolic remodelling associated with mtDNA: insights into the adaptive value of doubly uniparental inheritance of mitochondria.

Stefano Bettinazzi, Enrique Rodríguez, Liliana Milani, Pierre U Blier, Sophie Breton.

Mitochondria produce energy through oxidative phosphorylation (OXPHOS), which depends on the expression of both nuclear and mitochondrial DNA (mtDNA). In metazoans, a striking exception from strictly maternal inheritance of mitochondria is doubly uniparental inheritance (DUI). This unique system involves the maintenance of two highly divergent mtDNAs (F- and M-type, 8-40% of nucleotide divergence) associated with gametes, and occasionally coexisting in somatic tissues. To address whether metabolic differences underlie this condition, we characterized the OXPHOS activity of oocytes, spermatozoa, and gills of different species through respirometry. DUI species express different gender-linked mitochondrial phenotypes in gametes and partly in somatic tissues. The M-phenotype is specific to sperm and entails (i) low coupled/uncoupled respiration rates, (ii) a limitation by the phosphorylation system, and (iii) a null excess capacity of the final oxidases, supporting a strong control over the upstream complexes. To our knowledge, this is the first example of a phenotype resulting from direct selection on sperm mitochondria. This metabolic remodelling suggests an adaptive value of mtDNA variations and we propose that bearing sex-linked mitochondria could assure the energetic requirements of different gametes, potentially linking male-energetic adaptation, mitotype preservation and inheritance, as well as resistance to both heteroplasmy and ageing.

Keywords: ageing; doubly uniparental inheritance; heteroplasmy; mito-nuclear coevolution; mitochondria; oxidative phosphorylation

DOI: https://doi.org/10.1098/rspb.2018.2708

Nucleic Acids Res. 2019 Apr 10. pii: gkz266. [Epub ahead of print]

The mitoribosome-specific protein mS38 is preferentially required for synthesis of cytochrome c oxidase subunits.

Jeffri-Noelle Mays, Yolanda Camacho-Villasana, Rodolfo Garcia-Villegas, Xochitl Perez-Martinez, Antoni Barrientos, Flavia Fontanesi.

Message-specific translational regulation mechanisms shape the biogenesis of multimeric oxidative phosphorylation (OXPHOS) enzyme in mitochondria from the yeast Saccharomyces cerevisiae. These mechanisms, driven mainly by the action of mRNA-specific translational activators, help to coordinate synthesis of OXPHOS catalytic subunits by the mitoribosomes with both the import of their nucleus-encoded partners and their assembly to form the holocomplexes. However, little is known regarding the role that the mitoribosome itself may play in mRNA-specific translational regulation. Here, we show that the mitoribosome small subunit protein Cox24/mS38, known to be necessary for mitoribosome-specific intersubunit bridge formation and 15S rRNA H44 stabilization, is required for efficient mitoribogenesis. Consequently, mS38 is necessary to sustain the overall mitochondrial protein synthesis rate, despite an adaptive ∼2-fold increase in mitoribosome abundance in mS38-deleted cells. Additionally, the absence of mS38 preferentially disturbs translation initiation of COX1, COX2, and COX3 mRNAs, without affecting the levels of mRNA-specific translational activators. We propose that mS38 confers the mitochondrial ribosome an intrinsic capacity of translational regulation, probably acquired during evolution from bacterial ribosomes to facilitate the translation of mitochondrial mRNAs, which lack typical anti-Shine-Dalgarno sequences.

DOI: https://doi.org/10.1093/nar/gkz266