Fig. 1. Mutation of catp-1 confers resistance to the nicotinic agonist DMPP. (A) Dose-response sensitivity to DMPP of wild type (WT) and catp-1(kr17) mutants. (B) catp-1 gene structure and constructs used for transgenesis experiments. Triangle, Mos1 insertion; dashes, direct repeats; arrows, inverted repeats; ^*, STOP codon. (C) Survival on 0.75 mM DMPP. Error bars represent s.e.m. (n4 independent experiments, N96 total individuals, two independent transgenic lines per construct tested). Pcatp-1(br)::catp-1(br): extrachromosomal array carrying the C. briggsae catp-1 genomic region; Pcatp-1(br)::catp-1(el): C. elegans catp-1 cDNA under the control of a C. briggsae catp-1 promoter. Both constructs rescued catp-1(kr17) DMPP resistance. (D-G) catp-1 expression profile. Detection of GFP fluorescence by confocal (D) and epifluorescence microscopy (E) in transgenic larvae expressing Pcatp-1(C. briggsae)::GFP. catp-1 is expressed in the hyp (white arrowheads) and Pn.p cells of the epidermis (D) and in the duct cell of the excretory system (E-G). No GFP expression was detected in the lateral cells of the epidermis (seam cells: black arrowheads). In (G), the GFP image (E) of the duct cell was overlayed on a Nomarski picture of the same field (F) where the excretory duct is visible (black arrow). Scale bars: 20 µm (D); 5 µm (E-G). (H) Survival on 0.75 mM DMPP. Error bars represent s.e.m. (n3 independent experiments, N111 individuals, two independent lines). Expression of a dsRNA targeting catp-1 in the epidermis induces partial DMPP resistance in a sid-1(qt2) background (^*P<0.05, Mann-Whitney test).