Department of Integrative Biology, University of Guelph, 50 Stone Road East, Guelph, ON, N1G 2W1 Canada.
Biodiversity Institute of Ontario, University of Guelph, 50 Stone Road East, Guelph, ON, N1G 2W1 Canada.
Gigascience. 2017 Oct 1;6(10):1-14. doi: 10.1093/gigascience/gix073.
The evolution of powered flight is a major innovation that has facilitated the success of insects. Previously, studies of birds, bats, and insects have detected molecular signatures of differing selection regimes in energy-related genes associated with flight evolution and/or loss. Here, using DNA sequences from more than 1000 nuclear and mitochondrial protein-coding genes obtained from insect transcriptomes, we conduct a broader exploration of which gene categories display positive and relaxed selection at the origin of flight as well as with multiple independent losses of flight. We detected a number of categories of nuclear genes more often under positive selection in the lineage leading to the winged insects (Pterygota), related to catabolic processes such as proteases, as well as splicing-related genes. Flight loss was associated with relaxed selection signatures in splicing genes, mirroring the results for flight evolution. Similar to previous studies of flight loss in various animal taxa, we observed consistently higher nonsynonymous-to-synonymous substitution ratios in mitochondrial genes of flightless lineages, indicative of relaxed selection in energy-related genes. While oxidative phosphorylation genes were not detected as being under selection with the origin of flight specifically, they were most often detected as being under positive selection in holometabolous (complete metamorphosis) insects as compared with other insect lineages. This study supports some convergence in gene-specific selection pressures associated with flight ability, and the exploratory analysis provided some new insights into gene categories potentially associated with the gain and loss of flight in insects.
飞行的进化是一项重大创新，它促进了昆虫的成功。以前，对鸟类、蝙蝠和昆虫的研究已经检测到与飞行进化和/或丧失相关的能量相关基因中的分子特征，这些基因具有不同的选择机制。在这里，我们利用来自 1000 多个昆虫转录组的核和线粒体蛋白编码基因的 DNA 序列，更广泛地探索了哪些基因类别在飞行起源时以及在多次独立丧失飞行能力时表现出正选择和松弛选择。我们检测到一些核基因类别在有翅昆虫（Pterygota）的进化支中经常受到正选择，这些基因与蛋白酶等分解代谢过程有关，以及与剪接相关的基因。飞行丧失与剪接基因的松弛选择特征相关，这与飞行进化的结果相似。与各种动物类群中飞行丧失的先前研究类似，我们观察到无翅谱系的线粒体基因中的非同义替换与同义替换比率始终较高，表明与能量相关的基因选择松弛。虽然与飞行起源特别相关的氧化磷酸化基因没有被检测到受到选择，但与其他昆虫谱系相比，它们在完全变态（完全变态）昆虫中经常被检测到受到正选择。这项研究支持与飞行能力相关的基因特异性选择压力的一些趋同，并对可能与昆虫飞行获得和丧失相关的基因类别进行了一些新的探索性分析。
