Biology Department/Institute of Genomics and Evolutionary Medicine (iGEM), Temple University, Philadelphia, PA 19122-1801, USA.
Museu de História Natural e da Ciência da Universidade do Porto, Praça de Gomes Teixeira, 4099-002 Porto, Portugal; Departamento de Zoologia e Antropología (Museu Bocage), Museu Nacional de História Natural e da Ciência, Universidade de Lisboa, Rua da Escola Politécnica, 58, 1269-102 Lisboa, Portugal.
Infect Genet Evol. 2020 Nov;85:104576. doi: 10.1016/j.meegid.2020.104576. Epub 2020 Sep 29.
Haemosporida are diverse vector-borne parasites associated with terrestrial vertebrates. Driven by the interest in species causing malaria (genus Plasmodium), the diversity of avian and mammalian haemosporidian species has been extensively studied, relying mostly on mitochondrial genes, particularly cytochrome b. However, parasites from reptiles have been neglected in biodiversity surveys. Reptilian haemosporidian parasites include Haemocystidium, a genus that shares morphological features with Plasmodium and Haemoproteus. Here, the first complete Haemocystidium mitochondrial DNA (mtDNA) genomes are studied. In particular, three mtDNA genomes from Haemocystidium spp. sampled in Africa, Oceania, and South America, are described. The Haemocystidium mtDNA genomes showed a high A + T content and a gene organization, including an extreme fragmentation of the rRNAs, found in other Haemosporida. These Haemocystidium mtDNA genomes were incorporated in phylogenetic and molecular clock analyses together with a representative sample of haemosporidian parasites from birds, mammals, and reptiles. The recovered phylogeny supported Haemocystidium as a monophyletic group apart from Plasmodium and other Haemosporida. Both the phylogenetic and molecular clock analyses yielded results consistent with a scenario in which haemosporidian parasites radiated with modern birds. Haemocystidium, like mammalian parasite clades, seems to originate from host switches by avian Haemosporida that allowed for the colonization of new vertebrate hosts. This hypothesis can be tested by investigating additional parasite species from all vertebrate hosts, particularly from reptiles. The mtDNA genomes reported here provide baseline data that can be used to scale up studies in haemosporidian parasites of reptiles using barcode approaches.
血孢子虫是与陆地脊椎动物相关的多样化的媒介传播寄生虫。由于对引起疟疾的物种（疟原虫属）的关注，鸟类和哺乳动物血孢子虫物种的多样性已得到广泛研究，主要依赖于线粒体基因，特别是细胞色素 b。然而，在生物多样性调查中，爬行动物寄生虫被忽视了。爬行动物血孢子虫寄生虫包括 Haemocystidium，一个与疟原虫和血变原虫具有形态特征的属。在这里，研究了第一个完整的 Haemocystidium 线粒体 DNA (mtDNA) 基因组。特别是，描述了从非洲、大洋洲和南美洲采集的三种 Haemocystidium spp. 的 mtDNA 基因组。Haemocystidium mtDNA 基因组表现出高 A + T 含量和基因组织，包括 rRNA 的极端碎片化，这在其他血孢子虫中也有发现。这些 Haemocystidium mtDNA 基因组与来自鸟类、哺乳动物和爬行动物的代表性血孢子虫寄生虫样本一起纳入了系统发育和分子钟分析。恢复的系统发育支持 Haemocystidium 作为一个单系群，与疟原虫和其他血孢子虫分开。系统发育和分子钟分析的结果都与血孢子虫寄生虫与现代鸟类一起辐射的情景一致。Haemocystidium 与哺乳动物寄生虫类群一样，似乎起源于鸟类血孢子虫的宿主转换，这允许它们殖民新的脊椎动物宿主。通过调查所有脊椎动物宿主，特别是爬行动物的额外寄生虫物种，可以检验这一假设。这里报道的 mtDNA 基因组提供了基线数据，可以用于使用条形码方法扩大对爬行动物血孢子虫寄生虫的研究。
