Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, Canada, B3H 4R2.
Institute for Molecular Evolution, Heinrich Heine University, 40225 Düsseldorf, Germany
J Cell Sci. 2018 Jan 29;131(2):jcs203414. doi: 10.1242/jcs.203414.
Plastids in plants and algae evolved from the endosymbiotic integration of a cyanobacterium by a heterotrophic eukaryote. New plastids can only emerge through fission; thus, the synchronization of bacterial division with the cell cycle of the eukaryotic host was vital to the origin of phototrophic eukaryotes. Most of the sampled algae house a single plastid per cell and basal-branching relatives of polyplastidic lineages are all monoplastidic, as are some non-vascular plants during certain stages of their life cycle. In this Review, we discuss recent advances in our understanding of the molecular components necessary for plastid division, including those of the peptidoglycan wall (of which remnants were recently identified in moss), in a wide range of phototrophic eukaryotes. Our comparison of the phenotype of 131 species harbouring plastids of either primary or secondary origin uncovers that one prerequisite for an algae or plant to house multiple plastids per nucleus appears to be the loss of the bacterial genes and from the plastid genome. The presence of a single plastid whose division is coupled to host cytokinesis was a prerequisite of plastid emergence. An escape from such a monoplastidic bottleneck succeeded rarely and appears to be coupled to the evolution of additional layers of control over plastid division and a complex morphology. The existence of a quality control checkpoint of plastid transmission remains to be demonstrated and is tied to understanding the monoplastidic bottleneck.
植物和藻类中的质体是通过异养真核生物内共生整合蓝细菌而进化而来的。新的质体只能通过分裂产生；因此，细菌分裂与真核宿主细胞周期的同步对于光合真核生物的起源至关重要。大多数被采样的藻类每个细胞中都有一个质体，而多质体谱系的基干分支都是单质体，某些非维管束植物在其生命周期的某些阶段也是如此。在这篇综述中，我们讨论了在理解质体分裂所需的分子成分方面的最新进展，包括在广泛的光合真核生物中肽聚糖壁的那些成分（最近在苔藓中鉴定出了其残留物）。我们对 131 个种的表型进行比较，这些种的质体要么具有原始起源，要么具有次生起源，揭示了一个藻类或植物每个核容纳多个质体的先决条件似乎是从质体基因组中丢失了细菌基因 和 。具有一个与宿主胞质分裂偶联的分裂质体是质体出现的先决条件。这种单质体瓶颈的逃脱很少成功，似乎与对质体分裂和复杂形态的额外控制层的进化有关。质体传递的质量控制检查点的存在仍有待证明，并且与理解单质体瓶颈有关。
