In situ architecture of the ciliary base reveals the stepwise assembly of intraflagellar transport trains

Science. 2022 Jul 29;377(6605):543-548. doi: 10.1126/science.abm6704. Epub 2022 Jul 28.


The cilium is an antenna-like organelle that performs numerous cellular functions, including motility, sensing, and signaling. The base of the cilium contains a selective barrier that regulates the entry of large intraflagellar transport (IFT) trains, which carry cargo proteins required for ciliary assembly and maintenance. However, the native architecture of the ciliary base and the process of IFT train assembly remain unresolved. In this work, we used in situ cryo-electron tomography to reveal native structures of the transition zone region and assembling IFT trains at the ciliary base in Chlamydomonas. We combined this direct cellular visualization with ultrastructure expansion microscopy to describe the front-to-back stepwise assembly of IFT trains: IFT-B forms the backbone, onto which bind IFT-A, dynein-1b, and finally kinesin-2 before entry into the cilium.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Biological Transport
  • Chlamydomonas*
  • Cilia* / physiology
  • Dyneins / metabolism
  • Flagella / ultrastructure
  • Signal Transduction


  • Dyneins