Evolution of a morphological novelty occurred before genome compaction in a lineage of extreme parasites
Evolution of a morphological novelty occurred before genome compaction in a lineage of extreme parasites
复制标题
DOI：
10.1073/pnas.1410442111
复制
发表时间：
2014-10-28
影响因子：
11.1
通讯作者：
Ebert, Dieter
中科院分区：
文献类型：
--
作者：
Haag, Karen L.;James, Timothy Y.;Ebert, Dieter
细胞内寄生导致极端的适应，其进化历史很难理解，因为寄生虫和它们已知的自由生活的亲戚彼此如此不同。微孢子虫是人类和其他动物的细胞内寄生虫，其进化出高度特化的形态结构，但也极端生理和基因组简化。它们被认为是真菌树上的早期分支分支，但与其他物种进行比较是困难的，因为它们的分子进化速度非常高。微孢子虫中的线粒体已经退化成称为线粒体的细胞器，这些细胞器已经失去了基因组和产生ATP的能力。在这里，我们描述了肠道寄生虫的甲壳类水蚤，尽管有显着的形态相似的微孢子虫，保留了其真菌祖先的基因组特征。这种寄生虫，我们称之为Mitosporidium daphlagen.et sp. nov.，具有线粒体基因组，包括氧化磷酸化基因，但孢子阶段具有高度特化的感染装置-极管-只有微孢子虫才知道。系统基因组学将M.在微孢子虫的根部有一个小孢子虫。比较基因组分析表明，能量代谢的减少，微孢子虫进化的一个突出特征，是由控制细胞周期，DNA重组，修复和基因表达的机器减少。这些数据表明，M.在微孢子虫进化出极端的宿主代谢依赖性和线粒体呼吸丧失（微孢子虫对此是众所周知的）之前，达芙妮和其它微孢子虫已经存在。
Intracellular parasitism results in extreme adaptations, whose evolutionary history is difficult to understand, because the parasites and their known free-living relatives are so divergent from one another. Microsporidia are intracellular parasites of humans and other animals, which evolved highly specialized morphological structures, but also extreme physiologic and genomic simplification. They are suggested to be an early-diverging branch on the fungal tree, but comparisons to other species are difficult because their rates of molecular evolution are exceptionally high. Mitochondria in microsporidia have degenerated into organelles called mitosomes, which have lost a genome and the ability to produce ATP. Here we describe a gut parasite of the crustacean Daphnia that despite having remarkable morphological similarity to the microsporidia, has retained genomic features of its fungal ancestors. This parasite, which we name Mitosporidium daphniae gen. et sp. nov., possesses a mitochondrial genome including genes for oxidative phosphorylation, yet a spore stage with a highly specialized infection apparatus-the polar tube-uniquely known only from microsporidia. Phylogenomics places M. daphniae at the root of the microsporidia. A comparative genomic analysis suggests that the reduction in energy metabolism, a prominent feature of microsporidian evolution, was preceded by a reduction in the machinery controlling cell cycle, DNA recombination, repair, and gene expression. These data show that the morphological features unique to M. daphniae and other microsporidia were already present before the lineage evolved the extreme host metabolic dependence and loss of mitochondrial respiration for which microsporidia are well known.