TY - JOUR T1 - Dynamics of the IFT Machinery at the Ciliary Tip JF - bioRxiv DO - 10.1101/156844 SP - 156844 AU - Alexander Chien AU - Sheng Min Shih AU - Raqual Bower AU - Douglas Tritschler AU - Mary E. Porter AU - Ahmet Yildiz Y1 - 2017/01/01 UR - http://biorxiv.org/content/early/2017/06/28/156844.abstract N2 - Intraflagellar transport (IFT) of multiprotein complexes 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. We developed one-dimensional Photogate imaging and visualized the full range of movement of single IFT trains and motors in Chlamydomonas flagella. Anterograde trains split apart and the complexes mix with each other at the tip. Dynein-2 is carried to the tip by kinesin-2 as inactive cargo on anterograde trains. Unlike dynein-2, kinesin-2 detaches from IFT trains at the tip and diffuses in flagella. As the flagellum grows longer, diffusion delays return of kinesin-2 to the basal body, depleting available kinesin-2 for anterograde transport. Our results suggest that dissociation of kinesin-2 from IFT trains serves as a negative feedback mechanism that facilitates flagellar length control. ER -