Fig. 3. IR25a and IR76b are required for sensing attractive carboxylic acids in sweet-sensing GRNs.

(A) Screening candidate Ir mutants from L6 sensilla stimulated with 1% LA (n = 10-14). (B) Neuronal firing responses of control, Ir25a², and Ir76b¹ from L4 and L6 sensilla stimulated with 1% GA and 1% CA (n = 10-16). (C) Representative sample traces of (A) and (B). (D) Electrophysiological rescue of Ir25a² and Ir76b¹ mutant defects elicited by the indicated acids from L4 and L6 sensilla using broadly expressed specific GAL4s (Ir25a-GAL4 and Ir76b-GAL4). Gr5a-GAL4 (sweet-sensing GRNs marker) was also used to drive both UAS lines. +/- indicate the presence or absence of the transgene, respectively (n = 10-14). cont., control. (E) Behavioral rescue of Ir25a² and Ir76b¹ mutant deficits to acid-attraction with the indicated acids in the binary food choice assay. UAS-Ir25a was driven by Ir25a-GAL4 or Gr5a-GAL4 in Ir25a² mutant while UAS-Ir76b was driven by Ir76b-GAL4 or Gr5a-GAL4 in Ir76b¹ mutant. +/- indicate the presence or absence of the transgene, respectively (n = 6-8). All error bars represent the SEM. Multiple sets of data were compared using single-factor ANOVA coupled with Scheffe’s post hoc test. Asterisks indicate statistical significance compared to the control (**P < 0.01).