Department of Cellular Biology, University of Georgia, 500 D.W. Brooks Drive, Athens, GA 30602, USA.
Protist. 2010 Dec;161(5):672-87. doi: 10.1016/j.protis.2010.09.002. Epub 2010 Oct 30.
Plastids are found across the tree of life in a tremendous diversity of life forms. Surprisingly they are not limited to photosynthetic organisms but also found in numerous predators and parasites. An important reason for the pervasiveness of plastids has been their ability to move laterally and to jump from one branch of the tree of life to the next through secondary endosymbiosis. Eukaryotic algae have entered endosymbiotic relationships with other eukaryotes on multiple independent occasions. The descendants of these endosymbiotic events now carry complex plastids, organelles that are bound by three or even four membranes. As in all endosymbiotic organelles most of the symbiont's genes have been transferred to the host and their protein products have to be imported into the organelle. As four membranes might suggest, this is a complex process. The emerging mechanisms display a series of translocons that mirror the divergent ancestry of the membranes they cross. This review is written from the viewpoint of a parasite biologist and seeks to provide a brief overview of plastid evolution in particular for readers not already familiar with plant and algal biology and then focuses on recent molecular discoveries using genetically tractable Apicomplexa and diatoms.
质体存在于生命之树的各个分支中，具有巨大的多样性。令人惊讶的是，它们不仅限于光合生物，也存在于众多捕食者和寄生虫中。质体普遍存在的一个重要原因是它们能够横向移动，并通过二次内共生从生命之树的一个分支跳跃到另一个分支。真核藻类已经多次与其他真核生物发生内共生关系。这些内共生事件的后代现在携带复杂的质体，这些细胞器由三层甚至四层膜组成。与所有内共生细胞器一样，共生体的大部分基因已经转移到宿主中，其蛋白质产物必须被导入细胞器。正如四层膜所表明的那样，这是一个复杂的过程。新兴的机制显示出一系列移位子，反映了它们穿越的膜的不同起源。这篇综述从寄生虫生物学家的角度撰写，旨在为那些对植物和藻类生物学不熟悉的读者提供质体进化的简要概述，然后重点介绍使用遗传上可操作的顶复门生物和硅藻的最新分子发现。
