The URX neurons contain a cilium-like structure at their distal dendritic ends: A) (Top) Schematic of an URX (orange) and representative amphid sensory neuron (blue) in the head of an adult C. elegans hermaphrodite. Only neurons on the left are shown. (Bottom) Localization of the basal body-associated protein DYF-19::tagRFP expressed under the
gcy-36 promoter at the URX distal dendritic ends. URX is marked via expression of
gcy-32p::GFP. B) (Top two rows) Localization of the transition zone proteins MKS-5::tagRFP and NPHP-4::GFP in URX. MKS-5::tagRFP and NPHP-4::GFP were expressed under the
gcy-32 and endogenous promoters, respectively. Arrow indicates localization of NPHP-4 in other cilia, asterisk indicates background fluorescence in the pharynx. URX is marked with
gcy-32p::GFP or
gcy-36p::RFP. (Bottom row) Colocalization of DYF-19::tagRFP and NPHP-4::GFP at the URX distal dendritic ends. C) (Top two rows) Colocalization of ARL-13::tagRFP and ARL-13::GFP with NPHP-4::GFP and DYF-19::tagRFP, respectively, at the URX distal dendritic ends. ARL-13 was expressed under the
gcy-32 promoter, NPHP-4 and DYF-19 were expressed under the
gcy-36 promoter. (Bottom row) Colocalization of GCY-35::mKate with GIP-2::GFP at the URX distal dendritic ends. GCY-35::mKate was expressed under the
gcy-36 promoter; GIP-2::GFP was expressed from its endogenous locus (Harterink et al. 2018); arrows indicate localization in other cells. D) Summary of localization patterns of examined fusion proteins at the URX sensory endings. TZ: transition zone, BB: basal body. E) Localization of KAP-1::GFP, OSM-3::GFP, XBX-1::GFP, OSM-6::GFP and DYF-19::tagRFP fusion proteins at the URX distal dendritic ends. Fusion proteins were expressed under the
gcy-32 (OSM-3, KAP-1, OSM-6) or
gcy-36 (XBX-1, DYF-19) promoters. URX was visualized via expression of
gcy-36p::RFP. (Right) Representative kymograph of XBX-1::GFP movement in the URX sensory endings. F) (Left) Histogram of OSM-6::GFP anterograde velocity in the URX cilium-like structure. OSM-6::GFP was expressed in URX under the
gcy-32 promoter. (Right) Representative kymograph and schematic of OSM-6::GFP movement in the URX cilium-like structure. n= total of 148 particles from 20 animals. G) Localization of ARL-13::tagRFP in URX (marked via expression of
gcy-32p::GFP) in wild-type and
osm-6(
p811) animals. White and yellow arrows indicate the main dendrite and dendritic branches, respectively. H) Average YFP/CFP ratio change (solid lines) in URX neurons expressing YC2.60 in animals of the indicated genotypes in response to a 7%-21% oxygen shift. Shaded areas are SEM. The black bar indicates the time intervals used for statistical comparisons (Mann-Whitney U Test). Only responding neurons were included for generating the graph and the statistical analysis (WT: 21/21;
osm-6: 20/44). Since the laboratory N2 strain contains a gain-of-function variant of the NPR-1 neuropeptide Y-like receptor that inhibits some oxygen responses (Weber et al. 2010; Busch et al. 2012), imaging experiments were performed in an
npr-1(
ad609) loss-of-function background. In all relevant panels, white and yellow arrowheads indicate the presumptive cilia-like structure and the basal body/transition zone, respectively. Anterior is at left in all image panels. Numbers in lower right corners indicate the percentage of animals exhibiting the observed localization pattern; n > 21 for each. Scale bars: 5 um unless otherwise noted.