Fig. 2: OR42b mediates LP^WJL volatile-induced host growth in an ORCO-independent manner.

a GF embryos were treated either without (+none) or with inhalation of 0.03% (v/v) volatile chemicals (+chemical) during entire larval stages. Larval sizes were measured at 144 h AEL. n = 3 biologically independent experiments. b, c Tetrameric assembly of OR42b. OR42b construct design for expression (b, left top) and SDS-PAGE of purified OR42b eluted from affinity chromatography (b, left bottom). GFP-OR42b fusion protein is indicated with white arrowheads. Fluorescence size-exclusion chromatography screening under LMNG and DDM detergent conditions (b, right). Representative micrograph of OR42b based on negative-stained electron microscopy (c). Notable particles are indicated by white boxes, and enlarged (c, top). 2D class averages are shown at the bottom right (c, bottom). d AlphaFold-predicted model of tetrameric OR42b is presented as side and top views. The putative odorant-binding pocket formed by S2, S3, S4, and S6 helices has a conical shape. Conserved residues in the binding pocket are highlighted as gray spheres and Y¹⁵⁶, S¹⁵⁸, and S¹⁵⁹ are shown in magenta. e, f GF embryos were treated either without (−) or with (+) inhalation of LP^WJL volatiles during entire larval stages. Larval sizes were measured at 144 h AEL. GF control animals (Control) and GF animals with gut-specific OR42b^DN (Mex1-Gal4 > UAS-OR42b^DN) were used in (e); GF Control animals (Control), GF ORCO mutant animals (ORCO^−/−) and GF OR42b^DN knock-in animals (OR42b^DN-KI) were used in (f). n = 3 biologically independent experiments in (e, f). Data are mean ± s.e.m. P values (***p < 0.001, ns not significant) are indicated: one-way ANOVA with Tukey’s post hoc test in (a); unpaired two-tailed t-test in (e, f). Genotypes, sample sizes, and statistical analyses are shown in Supplementary Data 1. Source data are provided in the Source Data file.