D Each isoform from Gr28b.a to Gr28b.e was driven by Gr28b.a-GAL4 or Gr28b.c-GAL4 in a Gr28bMi background. The asterisks indicate significant differences from that of the Gr28b mutant detected by a single-factor ANOVA with Scheffe's analysis (**P < 0.01). D Saponin-induced action potential frequencies from the indicated transgenic flies on S6 sensilla (n = 7). 