PT  - JOURNAL ARTICLE
AU  - Jamin Jung
AU  - Julien Santi-Rocca
AU  - Cécile Fort
AU  - Jean-Yves Tinevez
AU  - Cataldo Schietroma
AU  - Philippe Bastin
TI  - Concentration of intraflagellar transport proteins at the ciliary base is required for proper train injection
AID  - 10.1101/2021.08.02.454739
DP  - 2021 Jan 01
TA  - bioRxiv
PG  - 2021.08.02.454739
4099  - http://biorxiv.org/content/early/2021/08/02/2021.08.02.454739.short
4100  - http://biorxiv.org/content/early/2021/08/02/2021.08.02.454739.full
AB  - Construction of cilia and flagella relies on Intraflagellar Transport (IFT). Although IFT proteins can be found in multiple locations in the cell, transport has only been reported along the axoneme. Here, we reveal that IFT concentration at the base of the flagellum of Trypanosoma brucei is required for proper assembly of IFT trains. Using live cell imaging at high resolution and direct optical nanoscopy with axially localized detection (DONALD) of fixed trypanosomes, we demonstrate that IFT proteins are localised around the 9 doublet microtubules of the proximal portion of the transition zone, just on top of the transition fibres. Super-resolution microscopy and photobleaching studies reveal that knockdown of the RP2 transition fibre protein results in reduced IFT protein concentration and turnover at the base of the flagellum. This in turn is accompanied by a 4- to 8-fold drop in the frequency of IFT train injection. We propose that the flagellum base provides a unique environment to assemble IFT trains.Competing Interest StatementThe authors have declared no competing interest.