Figure 2. nphp-2 single, arl-13; nphp-2 double, and arl-13; hdac-6; nphp-2 triple mutants exhibit defects in ciliary ultrastructure.

Horizontal panels indicated by 1, 2, and 3 correspond to singlet region, doublet region-to-singlet region transition, and TZ levels, respectively, and are comparable across the genotypes. The insets show an enlarged view of the region within the white box, and are diagrammed in the accompanying cartoon. All scale bars are 250 nm. (A1–3) In wild-type amphids, all doublet B-tubules within a cilium have similar spans. (A1) Distal microtubule singlets are devoid of B-tubules. B-tubule containing microtubule doublets are present in (A2) the doublet region and (A3) the TZ. (B1–3) In nphp-2 animals, amphid channel cilia are shifted lengthwise with respect to each other (cf. Fig. 6A). Within a cilium, spans of microtubule doublet B-tubules are asynchronous; arrows in insets indicate these microtubules. TZ Y-links are disorganized (C1–3) In arl-13; nphp-2 animals, most amphid channel cilia are absent. (C1) The distal end is filled with electron dense material with unresolvable microtubules. (C2) A single, stub-like cilium is visible, consisting of only microtubule singlets. (C3) TZ microtubules are abnormal with some missing microtubule doublets. We also observe vesicle-like structures at this level that are indicated by arrows. (D1–3) In arl-13; hdac-6; nphp-2 animals, most amphid cilia are visible. Ectopic singlets and doublets are still present. Cilia are shifted posteriorly towards the tail. (D1–2) insets show asynchronous microtubules within cilia.