Comparison of sections of IFT trains from a tomogram and the 3D model. (a) Schematic representation of part of a tomogram from a fla14 flagellum. The selected volume contains part of an IFT train, located in the space between the flagellar membrane (m) and an MT doublet (md). (b and d) Virtual sections (∼15 nm thick) obtained by sectioning the reconstructed volume tangentially to the axoneme, between the flagellar membrane and the MT doublet (as shown in panel a), thus sectioning the IFT train longitudinally. The white arrows indicate the IFT particles aligned along the train. (c and e) Individual planes of IFT particles from fla14 flagella maps after tomographic reconstruction and particle averaging. The planes are cut with the same orientation and at levels comparable to those in panels b and d. Notice the strong similarity of IFT sectioning contours between panels b and c and panels d and e. Colored masks are used to highlight the similarity of the structures in panels b and c (yellow masks) and d and e (red masks), and the similarity between the particles composing each IFT unit. The arrowheads in panels d and e indicate the link between the top and the bottom IFT particles.