IFT-B polypeptide OSM-6∷GFP abnormally associates with kinesin-II in nphp-4 mutants. OSM-6∷GFP in amphid (a–d and i–l) and phasmid (e–h and m–p) cilia in various IFT and nphp-4 mutants. The IFT-B polypeptide OSM-6∷GFP enters ciliary distal segments in kap-1 and kap-1;bbs-7 single and double mutants (b and f and d and h). OSM-6∷GFP localizes to middle segments of osm-3 mutants (c and g) and is absent from missing distal segments. In kap-1;nphp-4 and kap-1;bbs-7;nphp-4 animals, OSM-6∷GFP severely aggregates in amphid cilia (j and l, arrowhead) and fails to enter distal segments (j and n and l and p). The arrow in panel n indicates dendritic accumulation of OSM-6∷GFP. No IFT is detected, though slight amounts of OSM-6∷GFP passively enter severely stunted cilia (n and p). In contrast, IFT is detected in nphp-4;osm-3 double mutants (k and o; Table I). Brackets indicate separation of middle (M), distal (D), and TZ regions of cilia. (a–d) Lateral view of the lips; the anterior is to the top. (e–h) Lateral view of the tail; posterior is to the top. Bar, 10 μm.