Extended Data Fig. 9: Mapping of odour-specificity determinants of Or22a.

a, Electrophysiological responses of D. melanogaster Or22a/b-mutant neurons expressing DsecOr22a^WT or DmelOr22a^WT upon stimulation with increasing concentrations of noni fruit extract. Mean ± s.em. and individual data points; n = 9, female flies. Significantly different values are indicated. Pairwise Wilcoxon rank-sum test. b, Protein sequence alignment of Or22a orthologues of six species within the D. melanogaster species subgroup of drosophilids. Red shading, amino acid differences between D. melanogaster, D. sechellia, D. simulans and D. mauritiana that were analysed by mutagenesis in this study; blue shading, all other sequence differences. Arrowheads, chimaera breakpoints (for chimaeras analysed in c). Predicted transmembrane (TM) domains are indicated with grey lines (location as in a previous publication¹¹). c, Electrophysiological responses to a panel of noni odours conferred by chimeric Or22a proteins encoded by transgenes integrated at the Or22a/b locus of D. melanogaster. n = 5–6, female flies. Schematics on the left indicate the relative proportions of D. sechellia (red) and D. melanogaster (dark grey) sequences in each chimaera (precise chimaera breakpoints are shown in b). Significant differences to responses of DmelOr22a^WT-expressing neurons are shown. In c, d, g, pairwise Wilcoxon rank-sum test and P values adjusted for multiple comparisons using the Benjamini and Hochberg method. d, Electrophysiological responses of D. melanogaster Or22a/b-mutant neurons expressing different Or22a variants. n = 5–7, female flies. The location of each mutated residue is indicated in b. Data for responses of Or22a/b-mutant and DmelOr22a^WT-expressing neurons are replotted from c. Significant differences to responses of DmelOr22a^WT-expressing neurons are shown. e, Box plots with individual data points showing the same data as in c. f, Box plots with individual data points showing the same data as in d. g, Dose-dependent electrophysiological responses of D. sechellia Or22a neurons that express the indicated transgenes to ethyl or methyl hexanoate. Mean ± s.e.m. and individual data points; n = 10–11, female flies. Significant comparisons to the responses of neurons expressing the DmelOr22a^WT (left) or the DsecOr22a^WT (right) transgene are shown. NS, not significant (P > 0.05); *P < 0.05; **P < 0.01; ***P < 0.001.