PT  - JOURNAL ARTICLE
AU  - Hugo van den Hoek
AU  - Nikolai Klena
AU  - Mareike A. Jordan
AU  - Gonzalo Alvarez Viar
AU  - Miroslava Schaffer
AU  - Philipp S. Erdmann
AU  - William Wan
AU  - Jürgen M. Plitzko
AU  - Wolfgang Baumeister
AU  - Gaia Pigino
AU  - Virginie Hamel
AU  - Paul Guichard
AU  - Benjamin D. Engel
TI  - <em>In situ</em> architecture of the ciliary base reveals the stepwise assembly of IFT trains
AID  - 10.1101/2021.10.17.464685
DP  - 2021 Jan 01
TA  - bioRxiv
PG  - 2021.10.17.464685
4099  - http://biorxiv.org/content/early/2021/10/17/2021.10.17.464685.short
4100  - http://biorxiv.org/content/early/2021/10/17/2021.10.17.464685.full
AB  - 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. Here, we use in situ cryo-electron tomography to reveal native structures of the transition zone region and assembling IFT trains at the ciliary base. We combine 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 IFT-A, then dynein-1b, and finally kinesin-2 sequentially bind before entry into the cilium.Highlight Native molecular structure of the ciliary transition zone and hierarchical order of IFT assembly visualized within Chlamydomonas cells.Competing Interest StatementThe authors have declared no competing interest.