Supplementary Figure 3: Both length and non-MT based electron-dense structures of the TZ vary between different cilia types.

Representative electron micrographs show longitudinal sections (i) and sets of serial cross sections (ii) of the marked regions in the TZs of olfactory neurons (a), auditory neurons (b), spermatocytes (c) and early elongating spermatids (d). For cross-section series analysis, 70 nm serial sections were collected. Arrowheads mark the transition fibres (similar to distal appendage) that connect the distal tip of the BB to the ciliary membrane. The white arrow marks the single MT in the lumen of the spermatid BB in d. The cross section images in a, c and d are from serial sections of a TZ of olfactory, spermatocyte and spermatid, respectively. The cross section images in b were compiled from three different sets of serial sections. Notably, here the area that is distal to the BB and shows electron density on and around the MTs in longitudinal sections of ciliary bases is considered TZ. The region distal to the TZ is considered ciliary shaft (axoneme). All electron micrographs shown here represent features that were observed in 3 samples (the experiments presented in this figure were repeated independently twice with similar results). Scale bars on the longitudinal (a-di) and cross (a-dii) section micrographs are 500 nm and 100 nm, respectively (see also Fig. 3 and Supplementary Videos V7,8).