UMMS Affiliation

Department of Radiology; Witman Lab

Publication Date


Document Type



Algae | Amino Acids, Peptides, and Proteins | Cell Biology | Cellular and Molecular Physiology | Developmental Biology


Tubulin enters the cilium by diffusion and motor-based intraflagellar transport (IFT). However, the respective contribution of each route in providing tubulin for axonemal assembly remains unknown. Using Chlamydomonas, we attenuated IFT-based tubulin transport of GFP-beta-tubulin by altering the IFT74N-IFT81N tubulin-binding module and the C-terminal E-hook of tubulin. E-hook-deficient GFP-beta-tubulin was incorporated into the axonemal microtubules, but its transport frequency by IFT was reduced by approximately 90% in control cells and essentially abolished when the tubulin-binding site of IFT81 was incapacitated. Despite the strong reduction in IFT, the proportion of E-hook-deficient GFP-beta-tubulin in the axoneme was only moderately reduced. In vivo imaging showed more GFP-beta-tubulin particles entering cilia by diffusion than by IFT. Extrapolated to endogenous tubulin, the data indicate that diffusion provides most of the tubulin required for axonemal assembly. We propose that IFT of tubulin is nevertheless needed for ciliogenesis, because it augments the tubulin pool supplied to the ciliary tip by diffusion, thus ensuring that free tubulin there is maintained at the critical concentration for plus-end microtubule assembly during rapid ciliary growth.


Flagella, Cilia, Microtubule, Axoneme, Calponin homology domain, IFT81IFT74, Diffusion

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© 2020. Published by The Company of Biologists Ltd. Publisher PDF posted after 12 months as allowed by publisher's author rights policy at

DOI of Published Version



Craft Van De Weghe J, Harris JA, Kubo T, Witman GB, Lechtreck KF. Diffusion rather than intraflagellar transport likely provides most of the tubulin required for axonemal assembly in Chlamydomonas. J Cell Sci. 2020 Sep 11;133(17):jcs249805. doi: 10.1242/jcs.249805. PMID: 32801124; PMCID: PMC7502601. Link to article on publisher's site

Journal/Book/Conference Title

Journal of cell science

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Link to Article in PubMed

PubMed ID