Fig. 1

GA100-mCherry, but not GR100-mCherry or PR100-mCherry, can spread outside of ORNs. a-e Representative images of 5-days-old fly brains expressing mCherry (a & d), GA100-mCherry (b), PR100-mCherry (c) or GR100-mCherry (e) in Olfactory Receptor Neurons (ORNs) for 3 days. The same settings were applied to all genotypes while imaging their eGFP and mCherry signals. Spreading was only observed in flies expressing GA100-mCherry. EGFP and mCherry were detected using fluorescence as read-out. A GR-specific antibody was used to detect GR100-mCherry (e) and mCherry (d). Fly brains expressing only mCherry (a & d) were used as control to show that mCherry cannot spread by itself and to verify antibody specificity (d). Insets of the highlighted brain regions are shown. f Quantification of the number of mCherry puncta detected outside of ORNs across genotypes per brain after induction for 3 days. g Quantification of the eGFP signal detected within ORNs per brain (**P < 0.01 and *P < 0.05; One-way ANOVA, n = 4–6). Scale bars in images and insets are 100 um and 10 um, respectively