Figure 4: Functional interaction between MNs and sweet GRNs in the SEZ.
From: Mechanosensory neurons control sweet sensing in Drosophila
(a) PER on activation of MNs. PER assays were performed at the indicated temperature. ANOVA with Tukey post-hoc. **P<0.01. (b) Double-labelling of labellar MN and sweet GRN projections in the SEZ. Brains of Gr5a-LexA/+;UAS-mCD8::GFP/+;VT2692-GAL4/LexAOp-mCherryHA flies were stained with a rabbit anti-GFP (green) and the neuropil marker nc82 (blue). Scale bar, 50 μm. (c) GRASP between MNs labelled with VT2692-GAL4 and sweet GRNs labelled with Gr5a-LexA. The genotypes are Gr5a-LexA/+;LexAOp-CD4::spGFP11/+;UAS-CD4::spGFP1-10/VT2692-GAL4 (GRASP, left), Gr5a-LexA/+;LexAOp-CD4::spGFP11/+;UAS-CD4::spGFP1-10/+ (LexA only, middle), and LexAOp-CD4::spGFP11/+;UAS-CD4::spGFP1-10/VT2692-GAL4 (GAL4 only, right). Brains were stained with the neuropil marker nc82 (magenta). A schematic for GRASP is shown below. Scale bar, 50 μm. (d–f) Measurement of sweet GRN activity in the SEZ on MN activation. GCaMP3 was expressed in Gr5a-LexA neurons for calcium imaging and dTrpA1 was expressed in MNs (VT2692-GAL4 and R41E11-GAL4) for artificial neuronal activation. 100 mM sucrose was applied to the labellum. (d) Representative pseudocoluor images showing sweet GRN activity. Scale bar, 20 μm. SEZ ROIs are outlined in white. Arrows point to the corresponding traces in e. (e) Representative traces of fluorescence intensity changes evoked by 100 mM sucrose in sweet GRN termini on MN activation. (f) Mean maximal fluorescent intensity changes. Each trial was carried out at the indicated temperature. Repeated measure ANOVAs with post-hoc Mann–Whitney U-tests, *P<0.05, **P<0.01. n is indicated in parentheses. All data are presented as means±s.e.m.
