Fig. 4

Amino acid taste preference. a Schematic representation of the CAFE assay used to evaluate consumption preferences between a control solution without amino acid (-AA) and an amino acid-rich solution (+AA; 15 mM). b Preference for l-phenylalanine (l-Phe) by mated and virgin female flies of control and mutant OBP19b-Gal4 genotypes. Control and amino acid-rich solutions contained 1 mM sucrose. c Mated female preference for l-phenylalanine (l-Phe) solution in pure water (no sucrose). d Preference for l-phenylalanine (l-Phe), l-glutamine (l-Gln), l-alanine (l-Ala), and d-phenylalanine (d-Phe) by control, OBP19b-Gal4 null mutant and genetically rescued male flies (rescue: OBP19b-Gal4 > UAS-OBP19b). e Dose–response curves of control and OBP19b-Gal4 male flies in response to l-Phe and l-Ala. For each same-sex group (b/c or d), the letters indicate significant differences determined by the Kruskal–Wallis test and post hoc Wilcoxon test: ns = nonsignificant, *p < 0.05; ** p < 0.01; and ***p < 0.001). N = 7–15.