Phylogeny and evolution of amitochondriate eukaryotes

为了阐明真核生物的早期进化，我们一直在利用多分子序列数据研究原生生物（包括线粒体生物）的系统发育关系。本项目建立了蓝氏贾第鞭毛虫（dionads）、阴道毛滴虫（Trichon2onas阴道毛滴虫）、溶组织内阿米巴原虫（Entamoebidae）、克氏锥虫（Euglenoids）、人型双囊虫、人畜脑虫、海莱因锥虫、小孢子虫、巴拉木马螺虫等原生生物基因分析所需的DNA提取方法。基于这些原生生物的DNA，我们克隆了编码异亮基和谷氨酸trna合成酶、核糖体蛋白、7OkDa热休克蛋白和肽延伸因子的基因，并对其序列进行了测序，这些基因的序列尚未确定。包括这些原始数据的系统发育分析表明：(1)所有线粒体原生生物的序列都明显表现出典型真核生物的序列特征；(2)在进化过程中，4个线粒体原生生物谱系（Diplomonads、Tricbomonads、Entarnoebidae和Microsporidia）都发生了线粒体的二次丢失；(3)B. hominis与层桩有关，而层桩最近的近亲被Alveolata撕裂。

In order to elucidate early evolution of eukaryotes, we have been studying phylogenetic relationship aimng protists including arnitochondriate ones with the use of multiple molecular sequence data. In this project, we established the methods to get enough DNA needed for gene analyses of the protists, including Giardia lamblia (Diplomonads), Trichon2onas vaginalis, T. tenax (Trichomonads), Entamoeba histolytica (Entamoebidae), Trypanosoma cruzi (Euglenoids), Biastocystis hominis, Encephalitozoon cuniculi, E.heilein, Glugeaplecogiossi (Microsporidia), and Mastigarnoeba balamuthi. On the basis of the DNA of these protists, we cloned and sequenced the genes encoding isoleucyl- and valyl-tRNA synthetases, ribosomal proteins, 7OkDa heat shock proteins, and peptide elongation factors, the sequences of which had yet been detennined. Phylogenetic analyses including these original data suggested 1) that all the sequences from amitochondriate protists clearly show the sequence feature of typical eukaryotic type, 2) that all of the four amitochondriate protists lineages, Diplomonads, Tricbomonads, Entarnoebidae, and Microsporidia lost their mitochondria secondarily during their evolution, and 3) that B. hominis is involved in Stramenopiles and the closest relative of the Stramenopiles is shred by Alveolata.