Vanfleteren J R, Van de Peer Y, Blaxter M L, Tweedie S A, Trotman C, Lu L, Van Hauwaert M L, Moens L
Department of Morphology, Systematics and Ecology, University of Ghent, Belgium.
Mol Phylogenet Evol. 1994 Jun;3(2):92-101. doi: 10.1006/mpev.1994.1012.
We have begun to reconstruct the ancient history of the nematode phylum based on cytochrome c and globin amino acid sequences. The data suggest that the nematode ancestor diverged from a line leading to mammals about 1 billion years ago and that the most recent common ancestor of the extant species Caenorhabditis elegans, Trichostrongylus colubriformis, Nippostrongylus brasiliensis, Ascaris suum, and Pseudoterranova decipiens lived about 550 MY ago. The rhabditids and strongylids emerged as one offshoot of this ancestor, the ascarids as another. Rhabditids and strongylids diverged some 400 MY ago, whereas the genera Trichostrongylus and Nippostrongylus diverged slightly over 200 MY ago. A gene duplication event in the strongylid branch is predicted to have occurred around 250-335 MY ago. There are two globin genes in Nippostrongylus, expressed in anatomically distinct compartments (body and cuticle), and the single sequence from Trichostrongylus is most like the Nippostrongylus body globin gene. A strikingly different duplication event occurred within the same period in the line leading to the extant ascarid genera, creating a single polypeptide containing two globin domains. The genera Ascaris and Pseudoterranova diverged some 150-250 MY ago. Interestingly, the second globin repeat evolved at a faster rate in both species examined. This is possibly related to the acquisition of an unusual carboxyterminal extension, composed of alternating positively and negatively charged residues, that is necessary for the assembly of several monomers into the native polymeric molecules.
我们已开始基于细胞色素c和珠蛋白氨基酸序列来重构线虫门的古代历史。数据表明，线虫祖先大约在10亿年前从通向哺乳动物的谱系中分化出来，而现存物种秀丽隐杆线虫、蛇形毛圆线虫、巴西日圆线虫、猪蛔虫和欺骗新蛔线虫的最近共同祖先生活在大约5.5亿年前。小杆线虫类和圆线虫类作为该祖先的一个分支出现，蛔虫类则作为另一个分支。小杆线虫类和圆线虫类大约在4亿年前分化，而毛圆线虫属和日圆线虫属在略超过2亿年前稍有分化。预计在圆线虫分支中约在2.5亿至3.35亿年前发生了一次基因复制事件。日圆线虫中有两个珠蛋白基因，在解剖学上不同的区室（身体和角质层）中表达，而来自毛圆线虫的单一序列最类似于日圆线虫的身体珠蛋白基因。在导致现存蛔虫属的谱系中，在同一时期发生了一次明显不同的复制事件，产生了一种包含两个珠蛋白结构域的单一多肽。蛔虫属和新蛔线虫属大约在1.5亿至2.5亿年前分化。有趣的是，在所研究的两个物种中，第二个珠蛋白重复序列的进化速度都更快。这可能与获得一种不寻常的羧基末端延伸有关，该延伸由带正电荷和负电荷的残基交替组成，这是几种单体组装成天然聚合分子所必需的。
