Takishita Kiyotaka, Yamaguchi Haruyo, Maruyama Tadashi, Inagaki Yuji
Japan Agency for Marine-Earth Science and Technology, Yokosuka, Kanagawa, Japan.
PLoS One. 2009;4(3):e4737. doi: 10.1371/journal.pone.0004737. Epub 2009 Mar 9.
Eukaryotes bearing red alga-derived plastids--photosynthetic alveolates (dinoflagellates plus the apicomplexan Toxoplasma gondii plus the chromerid Chromera velia), photosynthetic stramenopiles, haptophytes, and cryptophytes--possess unique plastid-targeted glyceraldehyde-3-phosphate dehydrogenases (henceforth designated as "GapC1"). Pioneering phylogenetic studies have indicated a single origin of the GapC1 enzymes in eukaryotic evolution, but there are two potential idiosyncrasies in the GapC1 phylogeny: Firstly, the GapC1 tree topology is apparently inconsistent with the organismal relationship among the "GapC1-containing" groups. Secondly, four stramenopile GapC1 homologues are consistently paraphyletic in previously published studies, although these organisms have been widely accepted as monophyletic. For a closer examination of the above issues, in this study GapC1 gene sampling was improved by determining/identifying nine stramenopile and two cryptophyte genes. Phylogenetic analyses of our GapC1 dataset, which is particularly rich in the stramenopile homologues, prompt us to propose a new scenario that assumes multiple, lateral GapC1 gene transfer events to explain the incongruity between the GapC1 phylogeny and the organismal relationships amongst the "GapC1-containing" groups. Under our new scenario, GapC1 genes uniquely found in photosynthetic alveolates, photosynthetic stramenopiles, haptophytes, and cryptopyhytes are not necessarily a character vertically inherited from a common ancestor.
含有红藻衍生质体的真核生物——光合性囊泡藻（甲藻加上顶复门的刚地弓形虫加上色虫纲的维氏色虫）、光合性不等鞭毛藻、定鞭藻和隐藻——拥有独特的靶向质体的甘油醛-3-磷酸脱氢酶（以下简称“GapC1”）。开创性的系统发育研究表明，GapC1酶在真核生物进化中起源单一，但GapC1系统发育中有两个潜在的特殊之处：首先，GapC1树形拓扑结构显然与“含有GapC1”的类群之间的生物关系不一致。其次，在先前发表的研究中，四个不等鞭毛藻GapC1同源物一直是并系的，尽管这些生物已被广泛认为是单系的。为了更仔细地研究上述问题，在本研究中，通过确定/鉴定九个不等鞭毛藻和两个隐藻基因，改进了GapC1基因取样。我们对GapC1数据集进行的系统发育分析，该数据集特别富含不等鞭毛藻同源物，促使我们提出一种新的设想，即假设发生多次横向GapC1基因转移事件，以解释GapC1系统发育与“含有GapC1”的类群之间生物关系的不一致。在我们的新设想下，在光合性囊泡藻、光合性不等鞭毛藻、定鞭藻和隐藻中独特发现的GapC1基因不一定是从共同祖先垂直遗传的特征。
