Kuraku S, Hoshiyama D, Katoh K, Suga H, Miyata T
Department of Biophysics, Graduate School of Science, Kyoto University, Kyoto 606-8502 Japan.
J Mol Evol. 1999 Dec;49(6):729-35. doi: 10.1007/pl00006595.
The phylogenetic position of hagfishes in vertebrate evolution is currently controversial. The 18S and 28S rRNA trees support the monophyly of hagfishes and lampreys. In contrast, the mitochondrial DNAs suggest the close association of lampreys and gnathostomes. To clarify this controversial issue, we have conducted cloning and sequencing of the four nuclear DNA-coded single-copy genes encoding the triose phosphate isomerase, calreticulin, and the largest subunit of RNA polymerase II and III. Based on these proteins, together with the Mn superoxide dismutase for which hagfish and lamprey sequences are available in database, phylogenetic trees have been inferred by the maximum likelihood (ML) method of protein phylogeny. It was shown that all the five proteins prefer the monophyletic tree of cyclostomes, and the total log-likelihood of the five proteins significantly supports the cyclostome monophyly at the level of +/-1 SE. The ML trees of aldolase family comprising three nonallelic isoforms and the complement component group comprising C3, C4, and C5, both of which diverged during vertebrate evolution by gene duplications, also suggest the cyclostome monophyly.
盲鳗在脊椎动物进化中的系统发育位置目前存在争议。18S和28S rRNA树支持盲鳗和七鳃鳗的单系性。相比之下，线粒体DNA表明七鳃鳗与有颌类动物关系密切。为了澄清这个有争议的问题，我们对编码磷酸丙糖异构酶、钙网蛋白以及RNA聚合酶II和III最大亚基的四个核DNA编码单拷贝基因进行了克隆和测序。基于这些蛋白质，连同数据库中可获得盲鳗和七鳃鳗序列的锰超氧化物歧化酶，通过蛋白质系统发育的最大似然（ML）方法推断了系统发育树。结果表明，所有这五种蛋白质都倾向于圆口纲动物的单系树，并且这五种蛋白质的总对数似然性在±1个标准误水平上显著支持圆口纲动物的单系性。醛缩酶家族（由三种非等位异构体组成）和补体成分组（由C3、C4和C5组成）的ML树，这两者在脊椎动物进化过程中通过基因复制而分化，也表明了圆口纲动物的单系性。
