C. elegans arl-13 mutants possess defective cilium structure, morphology, and functions. (A) arl-13 gene schematic, showing genomic position of in-frame tm2322 deletion. (B) tm2322 encodes a ciliary ARL-13 protein. Fluorescence images of amphid/phasmid channel cilia in worms expressing arl-13(tm2322)::gfp are shown. GFP signals are restricted to MSs (m) and excluded from DSs (d). Some abnormal accumulations are found beneath cilia (arrowheads). (C) tm2322 mutants are dye-filling (Dyf) defective. Merged differential interference contrast (DIC)–fluorescence images after a DiI uptake assay are shown. Dye uptake into amphid (head) and phasmid (tail) neuron cell bodies (denoted by brackets) is strongly reduced in tm2322 mutants and weakly reduced in WT animals expressing arl-13(delPal)::gfp but restored in tm2322 animals expressing arl-13(WT)::gfp. (D) Cilium morphologies are defective in tm2322 worms. Fluorescence images of cilia from N2 and tm2322 animals expressing ciliated cell–specific transcriptional GFP markers srb-6p::gfp (PHA/B), gcy-5p::gfp (ASER), str-1p::gfp (AWB), str-2p::gfp (AWC), and gpa-6p::gfp (AWA) are shown. All images are similarly orientated, with ciliary base denoted (asterisks). Arrowheads indicate morphology defects such as kinks (ASER), bulges (PHA/B and AWA), curls (AWB,) and ectopic projections (AWC). (E) tm2322 mutants are chemosensory defective. Indices obtained from 30- and 60-min chemoattraction assays toward isoamyl alcohol for tm2322, N2, and osm-5(p802) worms are shown. Assay numbers are shown in parentheses. Error bars indicate SEM. Bars: (B and D) 3 µm; (C) 10 µm.