Sexually Antagonistic Mitonuclear Coevolution in Duplicate Oxidative Phosphorylation Genes

Area of Science:

• Genetics
• Evolutionary Biology
• Molecular Biology

Background:

• Mitochondrial function is essential for eukaryotic energy production, relying on coordinated nuclear and mitochondrial gene products, particularly in oxidative phosphorylation (OXPHOS) complexes.
• Mitochondrial genomes, due to maternal inheritance, can accumulate male-harming mutations ('mother's curse'), potentially leading to sexually antagonistic coevolution with nuclear genes.

Purpose of the Study:

• To investigate sexually antagonistic coevolution between nuclear-encoded OXPHOS paralogs and mitochondrial genes in mammals and Drosophila.
• To test the hypothesis that testis-specific OXPHOS paralogs evolved to counteract male-harming mitochondrial mutations.

Main Methods:

• Comparative analysis of evolutionary rates in nuclear-encoded OXPHOS paralogs, focusing on testis-specific expression patterns.
• Examination of structural data to assess the role of mitonuclear interactions in OXPHOS paralog evolution.
• Evaluation of selection pressures, including positive and relaxed selection, on these genes.

Main Results:

• Increased evolutionary rates were observed in testis-specific OXPHOS paralogs in both mammals and Drosophila, initially supporting the hypothesis.
• Further analysis suggested relaxed selection, particularly in Drosophila, might explain these rapid evolution patterns.
• Structural data indicated mitonuclear interactions are not consistently major drivers for many OXPHOS paralog evolution.

Conclusions:

• No single OXPHOS paralog definitively met criteria for evolving to counteract male-harming mitochondrial mutations.
• Alternative explanations for rapid evolution include mutualistic coevolution, adaptive subfunctionalization post-gene duplication, and relaxed selection in male tissues.