Evolutionary relationships among "jakobid" flagellates as indicated by alpha- and beta-tubulin phylogenies
Evolutionary relationships among "jakobid" flagellates as indicated by alpha- and beta-tubulin phylogenies
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DOI：
10.1093/oxfordjournals.molbev.a003830
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发表时间：
2001-04-01
影响因子：
10.7
通讯作者：
Sogin, ML
中科院分区：
文献类型：
--
作者：
Edgcomb, VP;Roger, AJ;Sogin, ML
Jakobid是自由生活的异养鞭毛虫，可能代表早期发散的线粒体原生生物。它们的超微结构与在分子系统发育中占据基础地位的真核生物有相似之处，它们的线粒体基因组结构类似于真细菌，这表明它们与起源于线粒体和氢小体的祖先α-蛋白细菌共生体有密切的亲缘关系。为了阐明Jakobids和其他早期分化的真核生物谱系之间的关系，我们鉴定了四个Jakobid：自由Jakoba、Jakoba incerata、美洲Reclinomonas americana(“核心Jakobids”)和Malawimonas Jakobiformis的α和β微管蛋白基因。这是首次报道来自这些生物体的核基因。基于阿尔法、贝塔和阿尔法加贝塔微管蛋白组合数据集的系统发育不支持雅各布类的单系性。虽然β-微管蛋白和结合的α-加β-微管蛋白的系统发育显示，自由J.Libera和美洲锥虫R.americana之间存在姐妹群关系，但另外两个雅各布形目和J.incarcerata的亲缘关系尚不清楚。在所有三个分析中，J.Libera、R.americana和M.jakobiformis都是从一个支撑良好的大型“植物-原生生物”分支中出现的，该分支包括植物、绿藻、隐芽植物、稻草虫、泡状动物、裸子虫、异叶藻和其他几个原生生物类群，但不包括动物、真菌、微孢子虫、副藻类或分支生物。在植物-原生生物分支中没有确定优先的分枝顺序，但J.Libera-R有一种趋势。美洲血统，由异球藻类、变形鞭毛虫和真甲虫原生动物组成的分支。Jakoba incerata在植物--贝塔原生支系--和阿尔法+贝塔-微管蛋白组合系统发育中分枝。在α-微管蛋白树中，J.incarcerata的地位尚未确定，根据所采用的系统发育方法，它与动物/真菌/微孢子虫类群或非线粒体类、副类群和分支类群属于弱类群。微管蛋白基因的系统发育与线粒体基因系统发育和超微结构数据基本一致，表明“Jakobids”可能是多系统发育的。与假想的深分枝的线粒体外交广告的关系仍然不确定。
Jakobids are free-living, heterotrophic flagellates that might represent early-diverging mitochondrial protists. They share ultrastructural similarities with eukaryotes that occupy basal positions in molecular phylogenies, and their mitochondrial genome architecture is eubacterial-like, suggesting a close affinity with the ancestral alpha-proteobacterial symbiont that gave rise to mitochondria and hydrogenosomes. To elucidate relationships among jakobids and other early-diverging eukaryotic lineages, we characterized alpha- and beta-tubulin genes from four jakobids: Jakoba libera, Jakoba incarcerata, Reclinomonas americana (the "core jakobids"), and Malawimonas jakobiformis. These are the first reports of nuclear genes from these organisms. Phylogenies based on alpha-, beta-, and combined alpha- plus beta-tubulin protein data sets do not support the monophyly of the jakobids. While beta-tubulin and combined alpha- plus beta-tubulin phylogenies showed a sister group relationship between J. libera and R. americana, the two other jakobids, M. jakobiformis and J. incarcerata, had unclear affinities. In all three analyses, J. libera, R. americana, and M. jakobiformis emerged from within a well-supported large "plant-protist" clade that included plants, green algae, cryptophytes, stramenopiles, alveolates, Euglenozoa, Heterolobosea, and several other protist groups, but not animals, fungi, microsporidia, parabasalids, or diplomonads. A preferred branching order within the plant-protist clade was not identified, but there was a tendency for the J. libera-R. americana lineage to group with a clade made up of the heteroloboseid amoeboflagellates and euglenozoan protists. Jakoba incarcerata branched within the plant-protist clade in the beta- and the combined alpha- plus beta-tubulin phylogenies. In alpha-tubulin trees, J. incarcerata occupied an unresolved position, weakly grouping with the animal/fungal/microsporidian group or with amitochondriate parabasalid and diplomonad lineages, depending on the phylogenetic method employed. Tubulin gene phylogenies were in general agreement with mitochondrial gene phylogenies and ultrastructural data in indicating that the "jakobids" may be polyphyletic. Relationships with the putatively deep-branching amitochondriate diplomonads remain uncertain.