Department of Biological Sciences, Arkansas State University, Jonesboro, AR, 72401, USA.
Illinois Natural History Survey, Prairie Research Institute, University of Illinois, Champaign, IL, 61820, USA.
Commun Biol. 2022 Jul 8;5(1):677. doi: 10.1038/s42003-022-03625-0.
The mitochondrial genomes (mitogenomes) of bilaterian animals are highly conserved structures that usually consist of a single circular chromosome. However, several species of parasitic lice (Insecta: Phthiraptera) possess fragmented mitogenomes, where the mitochondrial genes are present on separate, circular chromosomes. Nevertheless, the extent, causes, and consequences of this structural variation remain poorly understood. Here, we combined new and existing data to better understand the evolution of mitogenome fragmentation in major groups of parasitic lice. We found strong evidence that fragmented mitogenomes evolved many times within parasitic lice and that the level of fragmentation is highly variable, including examples of heteroplasmic arrangements. We also found a significant association between mitochondrial fragmentation and signatures of relaxed selection. Mitochondrial fragmentation was also associated with changes to a lower AT%, possibly due to differences in mutation biases. Together, our results provide a significant advance in understanding the process of mitogenome fragmentation and provide an important perspective on mitochondrial evolution in eukaryotes.
后生动物的线粒体基因组（mitogenome）是高度保守的结构，通常由单个环状染色体组成。然而，几种寄生虱（节肢动物门：Phthiraptera）具有碎片化的线粒体基因组，其中线粒体基因存在于单独的环状染色体上。尽管如此，这种结构变异的程度、原因和后果仍知之甚少。在这里，我们结合新的和现有的数据，以更好地了解寄生虱主要类群中线粒体基因组碎片化的进化。我们发现，碎片化的线粒体基因组在寄生虱内部多次进化，而且碎片化的程度高度可变，包括异质排列的例子。我们还发现，线粒体碎片化与选择放松的特征之间存在显著的关联。线粒体碎片化也与较低的 AT% 有关，这可能是由于突变偏向的差异造成的。总之，我们的研究结果在理解线粒体基因组碎片化的过程方面取得了重大进展，并为真核生物中线粒体进化提供了重要视角。
