Relaxed selection on male mitochondrial genes in DUI bivalves eases the need for mitonuclear coevolution.
Relaxed selection on male mitochondrial genes in DUI bivalves eases the need for mitonuclear coevolution.
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DOI：
10.1111/jeb.13931
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发表时间：
2021-11
影响因子：
2.1
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中科院分区：
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有丝核协同进化是真核生物高效能源生产的重要前提。然而，许多双壳类动物具有双单代遗传（DUI）和性别特异性线粒体（mt）基因组，这对有丝核共同进化提出了挑战。我们研究了调和有丝核共同进化与DUI的可能机制。在DUI蛤中没有发现核编码的，性别特异性的OXPHOS相似物，反驳了OXPHOS相似物作为该物种的解决方案。由于性别特异性mt-残基或在M - mt基因中处于正选择的mt-残基在接触核编码残基时没有被耗尽，因此导致核相互作用中断的mt变化也不太可能被强烈选择。然而，与假定的祖先F基因组相比，M基因组在所有mt OXPHOS基因和所有DUI物种中始终显示出更高的dN/dS比率。进一步的分析表明，这一直是由于M和F mt OXPHOS基因的宽松选择，而不是正选择。同样，与母系严格遗传的物种相比，DUI物种的F基因组选择更为宽松。结合最近的生理和分子进化研究，我们认为与F基因组相比，M基因组对线粒体功能的宽松选择限制了维持有丝核相互作用的需要。我们讨论了关于OXPHOS功能和DUI起源的研究结果。
Mitonuclear coevolution is an important prerequisite for efficient energy production in eukaryotes. However, many bivalve taxa experience doubly uniparental inheritance (DUI) and have sex-specific mitochondrial (mt) genomes, providing a challenge for mitonuclear coevolution. We examined possible mechanisms to reconcile mitonuclear coevolution with DUI. No nuclear-encoded, sex-specific OXPHOS paralogs were found in the DUI clam Ruditapes philippinarum, refuting OXPHOS paralogy as a solution in this species. It is also unlikely that mt changes causing disruption of nuclear interactions are strongly selected against because sex-specific mt-residues or those under positive selection in M mt genes were not depleted for contacting nuclear-encoded residues. However, M genomes showed consistently higher dN/dS ratios compared to putatively ancestral F genomes in all mt OXPHOS genes and across all DUI species. Further analyses indicated that this was consistently due to relaxed, not positive selection on M vs. F mt OXPHOS genes. Similarly, selection was relaxed on the F genome of DUI species compared to species with strict maternal inheritance. Coupled with recent physiological and molecular evolution studies, we suggest that relaxed selection on M mt function limits the need to maintain mitonuclear interactions in M genomes compared to F genomes. We discuss our findings with regard to OXPHOS function and the origin of DUI.