Open AccessDiffusion rather than IFT likely provides most of the tubulin required for axonemal assembly
Author(s) -
Julie C. Van De Weghe,
J. Aaron Harris,
Tomohiro Kubo,
George B. Witman,
KarlFerdinand Lechtreck
Publication year - 2020
Publication title -
journal of cell science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.384
H-Index - 278
eISSN - 1477-9137
pISSN - 0021-9533
DOI - 10.1242/jcs.249805
Subject(s) - tubulin , microtubule , biology , axoneme , intraflagellar transport , ciliogenesis , cilium , microbiology and biotechnology , chlamydomonas , cytoskeleton , biophysics , biochemistry , flagellum , cell , mutant , gene
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-β-tubulins by altering the IFT74/IFT81 tubulin-binding module and the C-terminal E-hook of tubulin. E-hook deficient GFP-β-tubulin is incorporated into the axonemal microtubules, but its transport frequency by IFT was reduced by ∼90% in control cells and essentially abolished when the IFT81 tubulin-binding site was incapacitated. Despite the strong reduction in IFT, the proportion of E-hook deficient GFP-β-tubulin in the axoneme was only moderately reduced. In vivo imaging showed more GFP-β-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.