MOE Key Laboratory for Biodiversity Science and Ecological Engineering, College of Life Sciences, Beijing Normal University, Beijing, 100875, China.
Department of Biology, Molecular Ecology and Evolution Laboratory, Lund University, Ecology Building, 223 62, Lund, SE, Sweden.
BMC Ecol Evol. 2023 Sep 11;23(1):49. doi: 10.1186/s12862-023-02155-5.
Mitochondrial respiration plays a central role in the survival of many eukaryotes, including apicomplexan parasites. A 479-bp fragment from the mitochondrial cytochrome b gene is widely used as a barcode to identify genetic lineages of avian malaria parasites Plasmodium and related haemosporidians. Here we looked for evidence of selection in the avian Plasmodium cyt b gene, using tests of selection and protein structure modeling. We also tested for the association between cyt b polymorphism and the host specificity of these parasites.
Based on 1,089 lineages retrieved from the Malavi database, we found that the frequency of the most conserved amino acids in most sites was more than 90%, indicating that the protein diversity of the avian Plasmodium cyt b barcode was low. The exceptions were four amino acid sites that were highly polymorphic, though the substitutions had only slight functional impacts on the encoded proteins. The selection analyses revealed that avian Plasmodium cyt b was under strong purifying selection, and no positively selected sites were detected. Besides, lineages with a wide host range tend to share cyt b protein haplotypes.
Our research indicates that purifying selection is the dominant force in the evolution of the avian Plasmodium cyt b lineages and leads to its low diversity at the protein level. Host specificity may also play a role in shaping the low mitochondrial diversity in the evolution of avian malaria parasites. Our results highlight the importance of considering selection pressure on the cyt b barcode region and lay a foundation for further understanding the evolutionary pattern of mitochondrial genes in avian malaria.
线粒体呼吸在许多真核生物的生存中起着核心作用，包括顶复门寄生虫。线粒体细胞色素 b 基因的 479 个碱基片段被广泛用作识别疟原虫和相关血孢子虫属寄生虫遗传谱系的条形码。在这里，我们使用选择测试和蛋白质结构建模来寻找鸟类疟原虫细胞色素 b 基因中的选择证据。我们还测试了细胞色素 b 多态性与这些寄生虫宿主特异性之间的关联。
基于从 Malavi 数据库中检索到的 1089 个谱系，我们发现大多数位点最保守氨基酸的频率超过 90%，这表明鸟类疟原虫细胞色素 b 条形码的蛋白质多样性较低。例外的是四个高度多态性的氨基酸位点，尽管这些取代对编码蛋白只有轻微的功能影响。选择分析表明，鸟类疟原虫细胞色素 b 受到强烈的纯化选择，没有检测到阳性选择位点。此外，宿主范围广泛的谱系往往具有共享的细胞色素 b 蛋白单倍型。
我们的研究表明，纯化选择是鸟类疟原虫细胞色素 b 谱系进化的主要力量，导致其在蛋白质水平上的多样性较低。宿主特异性也可能在塑造疟原虫寄生虫线粒体多样性的进化中发挥作用。我们的结果强调了考虑细胞色素 b 条形码区域选择压力的重要性，并为进一步了解鸟类疟疾中线粒体基因的进化模式奠定了基础。
