(A) Transient expression of Flag-IFT81, but not the tubulin-binding–deficient IFT81 mutants (in green), rescues the ciliogenesis defect after IFT81 siRNA knockdown. Primary cilia formation was induced by 0.5 μM cytochalasin D and detected by antibody to Arl13b (in red). CAP350 (in blue, inset images only) was used to visualize centrosomes. Mut1 and Mut2 are K73K75/EE and K73K75K113K114R115/EEEEE tubulin-binding mutants, respectively. Scale bar, 5 μm. (B) Quantification of the rescue experiment shown in (A). n = 3 independent experiments; statistical analyses by one-way analysis of variance.