Sculpting the endomembrane system in deep time: high resolution phylogenetics of Rab GTPases
Sculpting the endomembrane system in deep time: high resolution phylogenetics of Rab GTPases
复制标题
DOI：
10.1242/jcs.101378
复制
发表时间：
2012-05-15
影响因子：
4
通讯作者：
Dacks, Joel B.
中科院分区：
文献类型：
--
作者：
Elias, Marek;Brighouse, Andrew;Dacks, Joel B.
核和其他膜结合的细胞内区室的存在是真核细胞的定义特征。内共生解释了线粒体和质体的起源，但其余细胞区室的进化祖先并不完全记录。解决细胞器身份编码蛋白质的内膜系统内的进化历史是解开内源性衍生的细胞器的起源和多样化的必要条件。比较基因组学揭示了最后一个真核生物共同祖先（LECA）之后的事件，但在LECA之前的事件的解决，以及LECA中存在的细胞内隔室的完整描述，已被证明是难以捉摸的。我们已经设计并利用了一种新的系统发育策略来重建Rab GTP酶的历史，这是内膜特异性蛋白的一个关键家族。引人注目的是，我们推断一个非常复杂的细胞器组成LECA，我们预测拥有多达23个拉布GTP酶。这个剧目是显着大于目前在许多现代生物体，出乎意料地表明，在内膜系统的进化多样化的二次损失的主要作用。我们已经确定了两个功能未知但分布广泛的Rab旁系同源物，因此推测其性质古老; RabTitan和RTW。此外，我们发现，许多拉布旁系出现相对突然在早期后生动物的进化，这是在大多数其他主要真核生物群体的发病时缺乏显着的拉布家族扩张形成鲜明对比。最后，我们重建了高阶祖先分支的Rabs主要与内吞和外吞过程，这表明存在的原始Rabs与这些途径的建立，并给出了最深的一瞥到目前为止到前LECA历史的内膜系统。
The presence of a nucleus and other membrane-bounded intracellular compartments is the defining feature of eukaryotic cells. Endosymbiosis accounts for the origins of mitochondria and plastids, but the evolutionary ancestry of the remaining cellular compartments is incompletely documented. Resolving the evolutionary history of organelle-identity encoding proteins within the endomembrane system is a necessity for unravelling the origins and diversification of the endogenously derived organelles. Comparative genomics reveals events after the last eukaryotic common ancestor (LECA), but resolution of events prior to LECA, and a full account of the intracellular compartments present in LECA, has proved elusive. We have devised and exploited a new phylogenetic strategy to reconstruct the history of the Rab GTPases, a key family of endomembrane-specificity proteins. Strikingly, we infer a remarkably sophisticated organellar composition for LECA, which we predict possessed as many as 23 Rab GTPases. This repertoire is significantly greater than that present in many modern organisms and unexpectedly indicates a major role for secondary loss in the evolutionary diversification of the endomembrane system. We have identified two Rab paralogues of unknown function but wide distribution, and thus presumably ancient nature; RabTitan and RTW. Furthermore, we show that many Rab paralogues emerged relatively suddenly during early metazoan evolution, which is in stark contrast to the lack of significant Rab family expansions at the onset of most other major eukaryotic groups. Finally, we reconstruct higher-order ancestral clades of Rabs primarily linked with endocytic and exocytic process, suggesting the presence of primordial Rabs associated with the establishment of those pathways and giving the deepest glimpse to date into pre-LECA history of the endomembrane system.