PT  - JOURNAL ARTICLE
AU  - Alexander Chien
AU  - Sheng Min Shih
AU  - Raqual Bower
AU  - Douglas Tritschler
AU  - Mary E. Porter
AU  - Ahmet Yildiz
TI  - Dynamics of the IFT Machinery at the Ciliary Tip
AID  - 10.1101/156844
DP  - 2017 Jan 01
TA  - bioRxiv
PG  - 156844
4099  - http://biorxiv.org/content/early/2017/09/15/156844.short
4100  - http://biorxiv.org/content/early/2017/09/15/156844.full
AB  - Intraflagellar transport (IFT) is essential for the elongation and maintenance of eukaryotic cilia and flagella. Due to the traffic jam of multiple trains at the ciliary tip, how IFT trains are remodeled in these turnaround zones cannot be determined by conventional imaging. Using Photogate, we visualized the full range of movement of single IFT trains and motors in Chlamydomonas flagella. Anterograde trains split apart and IFT complexes mix with each other at the tip to assemble retrograde trains. Dynein-1b is carried to the tip by kinesin-II as inactive cargo on anterograde trains. Unlike dynein-1b, kinesin-II detaches from IFT trains at the tip and diffuses in flagella. As the flagellum grows longer, diffusion delays return of kinesin-II to the basal body, depleting kinesin-II available for anterograde transport. Our results suggest that dissociation of kinesin-II from IFT trains serves as a negative feedback mechanism that facilitates flagellar length control in Chlamydomonas.