Summary
Intraflagellar transport (IFT) is the rapid bidirectional movement of large protein complexes driven by kinesin and dynein motors along microtubule doublets of cilia and flagella. Here we used a combination of high-resolution electron and light microscopy to investigate how and where these IFT trains move within the flagellum of the protist Trypanosoma brucei. Focused Ion Beam Scanning Electron Microscopy (FIB-SEM) analysis of trypanosomes showed that trains are found almost exclusively along doublets 4 and 7 and that trains distribute in two categories according to their length. High-resolution live imaging of cells expressing mNeonGreen::IFT81 or GFP::IFT52 revealed for the first time IFT trafficking on two distinct tracks within the flagellum and that anterograde and retrograde IFT takes place on each of these tracks. At the distal end, a large individual anterograde IFT train is converted in several smaller retrograde trains in the space of 3-4 seconds while remaining on the same track.
Abbreviations
- FIB-SEM
- Focused Ion Beam Scanning Electron Microscopy
- IFA
- immunofluorescence assay
- IFT
- intraflagellar transport
- PFR
- paraflagellar rod
- TEM
- transmission electron microscopy