Fig. 4. Ultrastructural changes caused by PtNSF gene silencing (A-D). Panel A shows a dilated cortical cisterna, located below a ciliary basal body (bb) and flanked by alveolar sacs (as), with locally attached 0.05 µm large vesicles (asterisk). Some attached ribosomes indicate its possible origin from endoplasmic reticulum, which is frequently swollen (er, lower left). The `terminal cisterna' (early endosome) normally expected below a basal body is absent. (B) A structure similar to that seen in A has rounded-up and closed to a wheel-like structure with vesicles firmly attached at the cytosolic site trapped inside (asterisk). (C) Close to the emergence of a cilium (c), here in oblique section, at the site where alveolar sacs are interrupted, vesicles occur, instead of the usual single `parasomal sac' (clathrin-coated pit/vesicle). The arrow points to a very slim vesicle approaching the inner side of an alveolar sac (a similar vesicle can be detected in A and more are seen in Fig. 5B). The `infraciliary lattice' (il) made up of filamentous structures is unchanged. (D) Note accumulation of clumped vesicular ER elements (va; corresponding to densely immunolabeled cytoplasmic zones in Fig. 6A,B), largely devoid of ribosomes, the occurrence of numerous free ribosomes outside such vesicle aggregates and of an autophagic vacuole (av). m, mitochondria; t, trichocyst. Bars, 0.1 µm.