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Mitonuclear Coevolution, but not Nuclear Compensation, Drives Evolution of OXPHOS Complexes in Bivalves
Giovanni Piccinini1, Mariangela Iannello1, Guglielmo Puccio1
1Department of Biological, Geological and Environmental Sciences, University of Bologna, Bologna, Italy.
Molecular Biology and Evolution
|February 22, 2021
Summary
Mitochondrial and nuclear genes show strong coevolution in bivalves, challenging the nuclear compensation hypothesis for oxidative phosphorylation (OXPHOS) evolution. This suggests a broader model for mitonuclear coadaptation.
Area of Science:
- Evolutionary biology
- Genomics
- Molecular biology
Background:
- Oxidative phosphorylation (OXPHOS) complexes involve proteins encoded by both mitochondrial (mtDNA) and nuclear (nuDNA) genomes, necessitating mitonuclear coevolution.
- The nuclear compensation hypothesis posits that nuclear genes adapt to compensate for less efficient mitochondrial selection on mtDNA-encoded OXPHOS subunits.
- Bivalves exhibit extreme mtDNA variability and unique inheritance patterns, making them ideal for studying mitonuclear interactions.
Purpose of the Study:
- To investigate patterns of sequence evolution in OXPHOS subunits across 31 bivalve species.
- To test for evidence of mitonuclear coevolution and the nuclear compensation hypothesis in bivalves.
- To analyze the evolutionary rates and selection pressures on both mtDNA- and nuDNA-encoded OXPHOS subunits.
Main Methods:
- Phylogenetic analysis of 79 OXPHOS subunits from 31 bivalve species.
- Comparative analysis of evolutionary rates (dN/dS ratios) between mtDNA- and nuDNA-encoded OXPHOS subunits.
- Examination of phylogenetic concordance between nuclear-encoded OXPHOS (nuOXPHOS) and mitochondrial-encoded OXPHOS (mtOXPHOS) subunits.
Main Results:
- Strong signals of mitonuclear coevolution were detected, with concordant phylogenetic topologies between nuOXPHOS and mtOXPHOS subunits.
- Evolutionary rates of interacting mtOXPHOS and nuOXPHOS subunits were highly correlated.
- Contrary to the nuclear compensation hypothesis, mtDNA- and nuDNA-encoded subunits showed similar dN/dS ratios, and no compensatory positive selection was found in nuOXPHOS genes.
Conclusions:
- This study provides robust evidence for mitonuclear coevolution in bivalves, extending its known occurrence to a new major taxonomic group.
- The findings challenge the universal applicability of the nuclear compensation hypothesis, suggesting a need for revised models of mitonuclear coadaptation.
- Further research is needed to elucidate alternative mechanisms driving mitonuclear coevolution in the face of high mtDNA variability.
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