Department of Cell Biology, University of Geneva, Sciences III, Geneva, Switzerland.
Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ. Paris Sud, Université Paris-Saclay, Gif sur Yvette, France.
EMBO J. 2020 Nov 16;39(22):e106246. doi: 10.15252/embj.2020106246. Epub 2020 Sep 20.
Centrioles are evolutionarily conserved barrels of microtubule triplets that form the core of the centrosome and the base of the cilium. While the crucial role of the proximal region in centriole biogenesis has been well documented, its native architecture and evolutionary conservation remain relatively unexplored. Here, using cryo-electron tomography of centrioles from four evolutionarily distant species, we report on the architectural diversity of the centriole's proximal cartwheel-bearing region. Our work reveals that the cartwheel central hub is constructed from a stack of paired rings with cartwheel inner densities inside. In both Paramecium and Chlamydomonas, the repeating structural unit of the cartwheel has a periodicity of 25 nm and consists of three ring pairs, with 6 radial spokes emanating and merging into a single bundle that connects to the microtubule triplet via the D2-rod and the pinhead. Finally, we identified that the cartwheel is indirectly connected to the A-C linker through the triplet base structure extending from the pinhead. Together, our work provides unprecedented evolutionary insights into the architecture of the centriole proximal region, which underlies centriole biogenesis.
中心粒是进化上保守的微管三联体桶，它构成了中心体的核心和纤毛的基部。虽然近端区域在中心粒发生中的关键作用已经得到了很好的证明，但它的天然结构和进化保守性仍然相对未知。在这里，我们使用来自四个进化上不同的物种的中心粒的冷冻电子断层扫描，报告了中心粒近端轮辐状结构域的结构多样性。我们的工作揭示了轮辐中央轮毂由堆叠的成对环和内部轮辐内密度构成。在草履虫和衣藻中，轮辐的重复结构单元具有 25nm 的周期性，由三个环对组成，6 个放射状辐条发出并合并成一个单一的束，通过 D2 杆和钉头连接到微管三联体。最后，我们确定轮辐通过从钉头延伸的三联体基底结构间接连接到 A-C 接头。总的来说，我们的工作为中心粒近端区域的结构提供了前所未有的进化见解，这是中心粒发生的基础。
