Multiple gene phylogenies support the monophyly of cryptomonad and haptophyte host lineages
Multiple gene phylogenies support the monophyly of cryptomonad and haptophyte host lineages
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DOI：
10.1016/j.cub.2007.03.069
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发表时间：
2007-05-15
期刊：
影响因子：
9.2
通讯作者：
Keeling, Patrick J.
中科院分区：
文献类型：
--
作者：
Patron, Nicola J.;Inagaki, Yuji;Keeling, Patrick J.
隐藻通过真核红球藻的次级内共生摄取获得其质体。其他几个藻类谱系通过这样的事件获得质体[1]，但隐藻的区别在于保留了一个遗留的红藻核，即核态[2]。核形（以及它在其他谱系中的缺失）可以揭示大量关于内共生的过程和历史，但前提是我们知道隐藻和其他藻类之间的关系，这一直是有争议的。最近的几项分析表明隐藻质体和其他一些或所有含红藻的谱系之间存在关系[3-6]，但我们还必须知道宿主核基因是否反映这种关系以确定内共生事件的数量，这尚未得到证实。我们已经进行了表达序列标签（EST）调查的隐单胞菌Guillardia theta。对102个直链藻核编码蛋白（18，425个氨基酸比对位置）的系统发育分析显示，隐藻和附着藻类之间存在强大的姐妹群关系，后者也具有红色次级质体。这种关系表明，核形的损失必须发生在附着植物独立的任何其他红藻含谱系，两者的祖先已经包含一个红藻内共生体。
Cryptomonad algae acquired their plastids by the secondary endosymbiotic uptake of a eukaryotic red alga. Several other algal lineages acquired plastids through such an event [1], but cryptomonads are distinguished by the retention of a relic red algal nucleus, the nucleomorph [2]. The nucleomorph (and its absence in other lineages) can reveal a great deal about the process and history of endosymbiosis, but only if we know the relationship between cryptomonads and other algae, and this has been controversial. Several recent analyses have suggested a relationship between plastids of cryptomonads and some or all other red alga-containing lineages [3-6], but we must also know whether host nuclear genes mirror this relationship to determine the number of endosymbiotic events, and this has not been demonstrated. We have carried out an expressed sequence tag (EST) survey of the cryptomonad Guillardia theta. Phylogenetic analyses of 102 orthologous nucleus-encoded proteins (18,425 amino acid alignment positions) show a robust sister-group relationship between cryptomonads and the haptophyte algae, which also have a red secondary plastid. This relationship demonstrates that loss of nucleomorphs must have taken place in haptophytes independently of any other red alga-containing lineages and that the ancestor of both already contained a red algal endosymbiont.