Origin and evolution of plastid-like organella in Apicomplexa

为了估计顶质体的起源和进化，一个质体样的细胞器，通常是在大多数的顶复门寄生虫中发现，并获得更多的见解有关顶复门的系统发育关系，我们克隆和测序基因编码核糖体RNA，延伸因子，异亮氨酰和缬氨酰tRNA合成酶从不同的分类谱系。包括顶复门（疟原虫属、弓形虫属、巴贝虫属、隐孢子虫属）、层孢子虫属（囊胚虫属、原喙虫属）、裸虫属（锥虫属）、阿米巴虫属（内阿米巴属、鞭毛虫属）和微孢子虫属（Glugea、脑孢子虫属）。利用这些数据结合公共数据库中的相关序列，通过分子系统发生学的最大似然法对每个个体基因进行详细的系统发育分析。将来自个体基因分析的估计对数似然性进行汇总，并在最大似然法的框架中进行组合遗传学。通过对隐孢子虫属的系统发育分析，得出以下结论：隐孢子虫属是顶复门的最早分支;（疟疾的寄生虫），接近间日疟原虫和其他猿类寄生虫;（3）顶复门与双鞭藻属的亲缘关系最近，而纤毛虫属与顶复门和双鞭藻属的共同祖先为姐妹群;（4）包括顶复门（Apicomplexa）、双鞭毛门（dianofiagellates）和纤毛门（Ciliophora）在内的高级谱系（Alveolata）的单系性得到多个基因的支持;（5）Alveolata与另一高级谱系（Stramenopiles）的关系密切;（6）Alveolata和Strarnenopiles的共同祖先在真核生物树中与裸藻动物门（Euglenozoa）或Viiridiplantae关系密切。

In order to estimate origin and evolution of the apicoplast, a plastid-like organelle that is usually found in most of apicomplexan parasites, and to gain more insights into the phylogenetic relationships concerning the phylum Apicomplexa, we cloned and sequenced genes encoding ribosomal RNAs, elongation factors, isoleucyl-and valyl-tRNA synthetases from diverse taxonomic lineages. These include Apicomplexa (Plasmodium, Toxoplasma, Babesia, Cryptosporidiuni), stramenopiles (Blastocystis, Proterornonas), Euglenozoa (Thypanosoma), Amoebozoa (Entamoeba, Mastigamoeba), and Microsporidia (Glugea, Encephalitozoon). Using these data in combination with related sequences in the public databases, detailed phylogenetic analyses were carried out on each of the individual genes by the maximum likelihood method of molecular phylogeny. The estimated log-likelihoods derived from the analyses of individual genes were summed up and combined phylogeny was performed in a framework of the maximum likelihood approach. Based on these analyses the following phylogenetic findings have been obtained up to now: (1)The genus Cryptosporidiurn is the earliest offshoot of Apicomplexa; (2) Plasmodium coatneyi, the phylogenetic position of which had been unknown in the genus Piasmodiuni (malaria 'parasites), is close to P vivax and other simian parasites;(3)The closest relative of the phylum Apicomplexa is dianofiagellates, and the genus Ciliophora shares a sister group' position to the common ancestor of Apicomplexa and dianoflagellates; (4)Monophyly of the higher-order lineage, Alveolata, including Apicomplexa, dianofiagellates, and Ciliophora is supported by several genes; (5)Alveolata is close to the other higher-order lineage, stramenopiles; (6)The common ancestor of Alveolata and strarnenopiles is close to Euglenozoa or to Viiridiplantae in the tree of Eukaryota.