Evidence from beta-tubulin phylogeny that microsporidia evolved from within the fungi
Evidence from beta-tubulin phylogeny that microsporidia evolved from within the fungi
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DOI：
10.1093/oxfordjournals.molbev.a026235
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发表时间：
2000-01-01
影响因子：
10.7
通讯作者：
Palmer, JD
中科院分区：
文献类型：
--
作者：
Keeling, PJ;Luker, MA;Palmer, JD
微孢子虫是专性细胞内寄生虫，被认为是一种古老的真核生物谱系，基于核糖体RNA和翻译延伸因子的分子系统发育。然而，这种古老的起源最近受到了质疑，因为其他几个分子系统发育表明，小孢子虫与真菌密切相关。然而，大多数将微孢子虫与真菌放在一起的蛋白质树都没有得到很好的采样，因此无法确定微孢子虫是由真菌进化而来还是从真菌的原生亲戚进化而来。我们对3种微孢子虫、4种壶菌和12种接合菌真菌的β -微管蛋白进行了测序，扩大了β -微管蛋白的代表性，包括所有4种真菌分裂和广泛的微孢子虫。在包括这些新序列的系统发育树中，真菌β -微管蛋白的总体拓扑结构总体上符合真菌四个分裂之间的预期关系，尽管在一些分析中接合菌是多系的。微孢子虫始终属于这种真菌多样化，而不是真菌的姐妹群。总的来说，微管蛋白系统发育表明，微孢子虫是在壶菌分化后由真菌进化而来的。我们还发现壶菌的α -和β -微管蛋白与其他真菌或微孢子虫的微管蛋白差异要小得多。在只有壶菌为真菌代表的树木中，微孢子虫仍然与真菌（即壶菌）分支，这表明微孢子虫和真菌微管蛋白之间的联系不是长枝吸引的产物。
Microsporidia are obligate intracellular parasites that were thought to be an ancient eukaryotic lineage based on molecular phylogenies using ribosomal RNA and translation elongation factors. However, this ancient origin of microsporidia has been contested recently, as several other molecular phylogenies suggest that microsporidia are closely related to fungi. Most of the protein trees that place microsporidia with fungi are not well sampled, however, and it is impossible to resolve whether microsporidia evolved from a fungus or from a protistan relative of fungi. We have sequenced beta-tubulins from 3 microsporidia, 4 chytrid fungi, and 12 zygomycete fungi, expanding the representation of beta-tubulin to include all four fungal divisions and a wide diversity of microsporidia. In phylogenetic trees including these new sequences, the overall topology of the fungal beta-tubulins generally matched the expected relationships among the four fungal divisions, although the zygomycetes were polyphyletic in some analyses. The microsporidia consistently fell within this fungal diversification, and not as a sister group to fungi. Overall, beta-tubulin phylogeny suggests that microsporidia evolved from a fungus sometime after the divergence of chytrids. We also found that chytrid alpha- and beta-tubulins are much less divergent than are tubulins from other fungi or microsporidia. In trees in which the only fungal representatives were the chytrids, microsporidia still branched with fungi (i.e., with chytrids), suggesting that the affiliation between microsporidian and fungal tubulins is not an artifact of long-branch attraction.