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.

中文翻译：

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低温电子层析成像揭示了含有中心车轮的区域的结构。

质心是进化上保守的微管三胞胎的桶，形成了中心体的核心和纤毛的基部。尽管已经充分证明了近端区域在中心粒生物发生中的关键作用，但其天然结构和进化保守性仍然相对未开发。在这里，我们使用来自四个进化距离远的物种的中心粒的冷冻电子断层扫描，报告了中心粒近端承轮区域的建筑多样性。我们的工作表明，车轮中心轮毂由成对的圆环构成，内部有车轮内部密度。在这两种草履虫和衣，车轮的重复结构单元的周期为25 nm，由三对环组成，有6个径向辐条散发并合并成一个束，该束通过D2杆和销头连接到微管三联体。最后，我们确定车轮通过从销头伸出的三重态基础结构间接连接到AC连接器。总之，我们的工作为中心粒近端区域的结构提供了空前的进化见解，而中心粒近端区域是中心粒生物发生的基础。