Alpha-tubulin from early-diverging eukaryotic lineages and the evolution of the tubulin family
Alpha-tubulin from early-diverging eukaryotic lineages and the evolution of the tubulin family
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DOI：
10.1093/oxfordjournals.molbev.a025576
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发表时间：
1996-12-01
影响因子：
10.7
通讯作者：
Doolittle, WF
中科院分区：
文献类型：
--
作者：
Keeling, PJ;Doolittle, WF
微管蛋白基因家族包括α-、β-和γ-微管蛋白亚家族，由高度保守的蛋白质组成，这些蛋白质是真核微管的主要结构和功能组分。我们感兴趣的是：（1）在真核生物进化过程中，确定导致旁系同源α的复制。β的和γ亚家族的出现和（2）微管蛋白序列在重建生物体发育中的可能用途。为了扩大α-微管蛋白的分类学代表性，使其大致等于β-微管蛋白，对来自三种微孢子虫（Encephalitozoon hellem，Nosema locustae和Spraguea lophii），两种副基虫（Monocercomonas sp.和Trichomitus batrachorum）和一种异叶虫（Acrasis rosea）的α-微管蛋白基因进行了测序。利用这些新基因构建了α-微管蛋白和β-微管蛋白的系统发育树并进行了比较。树是一致的，但与其他分子的同源性不一致。α-和β-微管蛋白树之间的一致性可能是由于一种分子与另一种分子的变体的共同适应而产生的，这是由于它们在微管中的紧密空间结合。因此，这些树可能无法为系统发育结果提供独立的支持。然而，这些意想不到的结果之一，即微孢子虫与真菌集群，由其他间接证据支持，因此可能反映了一个真实的关系，尽管通常分配给微孢子虫的基础位置。三种微管蛋白之间的关系也通过构建所有三种类型的树进行了研究。这些树被认为是有限的价值，以确定每个亚科内的根的位置，因为大的家族间的距离，但他们确实证实了所有已知的基因分为三个单系亚科的分类。来自秀丽隐杆线虫和酿酒酵母的差异基因被认为代表了新的δ-和ε-微管蛋白类，发现它们分别与来自动物和真菌的γ-微管蛋白特异性相关，因此最好被视为γ-微管蛋白的快速进化直向同源物。
The tubulin gene family, which includes alpha-, beta-, and gamma-tubulin subfamilies, is composed of highly conserved proteins which are the principle structural and functional components of eukaryotic microtubules. We are interested in (1) establishing when in eukaryotic evolution the duplications leading to paralogous alpha. beta. and gamma subfamilies occurred and (2) the possible utility of tubulin sequences in reconstructing organismal phylogeny. To broaden the taxonomic representation of alpha-tubulins so that it roughly equals that of beta-tubulins, alpha-tubulin genes from three Microsporidia (Encephalitozoon hellem, Nosema locustae, and Spraguea lophii), two Parabasalia (Monocercomonas sp. and Trichomitus batrachorum), and one Heterolobosean (Acrasis rosea) were sequenced. With these new genes, phylogenetic trees of alpha- and beta-tubulins were constructed and compared. Trees were congruent with each other, but incongruent with other molecular phylogenies. The agreement between alpha- and beta-tubulin trees could arise by the co-adaptation of one molecule to variants of the other as a result of their intimate steric association in microtubules. Thus, these trees may not be providing independent support for the phylogenetic results. However, one of these unexpected results, that microsporidia cluster with fungi, is supported by other circumstantial evidence, and may therefore reflect a real relationship despite the basal position usually assigned to microsporidia. Relationships between the three tubulins were also examined by constructing trees of all three types. These trees were found to be of limited value for determining the position of the root within each subfamily because of the great interfamily distances, but they do confirm the classification of all known genes into three monophyletic subfamilies. Divergent genes from Caenorhabditis elegans and Saccharomyces cerevisiae that have been proposed to represent the novel classes delta- and epsilon-tubulin were found to be specifically related to gamma-tubulins from animals and fungi respectively, and therefore are best seen as rapidly evolving orthologues of gamma-tubulin.