Single-dendritic labellum neurons discriminate substrates of different stiffness during feeding.

a The preference of food hardness between 0.25% and 0.4% agarose of the mechanotransduction channel gene mutants (iav1, tmc-sgal4, tmc1, nangal4) in the two-way choice feeding assay. 10 mM sucrose was added to different concentrations of agarose. n = 33, 20, 27, 14 and 25 for each group. Statistical test: one-way ANOVA with Dunnett’s correction for multiple comparisons against the w1118 group; mean ± SEM. b The preference of food hardness of iav1 males between 0.25% and 5 different stiffness (0.25%, 0.35%, 0.4%, 0.45%, 0.5%) in the two-way choice feeding assay. 10 mM sucrose was added to different concentrations of agarose. n = 10, 9, 12, 9 and 13 for each group. Data are represented as mean ± SEM. c The preference of food hardness when sd-L neurons were silenced with kir2.1 in the two-way choice feeding assay. 10 mM sucrose was added to different concentrations of agarose. n = 21, 21 and 18 for each group. Statistical test: one-way ANOVA with Dunnett’s correction for multiple comparisons against the sd-L-SS > UAS-kir2.1 group; mean ± SEM. d Expression patterns for sd-L-SS (split-Gal4: vGluT-AD and iav-DBD) in the labellum and brain. Immunostaining used either anti-GFP and/or anti-Brp (magenta). Scale bar, 50 μm. Brain was counter-stained with the neuropil marker nc82 (magenta). Red arrow pointed to sd-L neurons (in the labellum) and its axon (in the brain). e PER assay of flies when sd-L neurons were activated using CsChrimson by exposure to 1 mW/cm2 light (595nm). Flies were tested with 20 mM sucrose. n = 29, 18, 14 and 21 for each group. Statistical test: one-way ANOVA with Dunnett’s correction for multiple comparisons against the sd-L-SS > UAS-CsChrimson with ATR group; mean ± SEM. f-h FlyPAD assay of flies when sd-L neurons were silenced with kir2.1. Flies were all starved for 24 h before assay. Both 0.25% and 0.4% agarose containing 10 mM sucrose. Cumulative sips numbers of sd-L-SS flies, n = 16 for each group (f). Cumulative sip numbers of UAS-kir2.1flies, n = 16 for each group (g). Cumulative sip numbers of sd-L-SS > UAS-kir2.1 flies, n = 15 for each group (h). For all analyses, statistical differences are represented as follows: ns, not significant, p > 0.05; *, p < 0.05; **, p < 0.01; ***, p < 0.001; ****, p < 0.0001.