OBP19b is involved in the taste perception of amino acid in Drosophila melanogaster

Chemoperception plays a crucial role in the detection of nutritive food and avoidance of toxic compounds. It also allows animals to identify a suitable ecological niche and mating partners. As many other insects, Drosophila melanogaster possess a very sensitive chemosensory ability to detect and discriminate a wide panel of semiochemicals. Chemosensory detection is mostly mediated by olfactory and gustatory systems involving several multigene chemoreceptor families. Volatile and non-volatile chemicals compounds entering the sensory organ (sensillum) must be solubilized before being transported through the hydrophilic sensillum lymph bathing chemosensory receptors. Such “perireceptor events” involve a family of soluble proteins named odorant-binding proteins (OBPs). Despite the fact that they were originally found in olfactory sensilla, some OBPs are also expressed in gustatory sensilla. While the physiological role of OBPs in olfaction and gustation remains unclear, many studies suggest that they act as protein carriers of lipophilic chemicals. A recent study showed that the OBP49a, expressed in the gustatory system, is required for the sensing of some bitter compounds1. To determine more precisely the role of OBPs in the perception of food and pheromonal compounds in D. melanogaster adults, we studied the OBP19b, which is only expressed in gustatory sensilla. Hence, we heterologously produced OBP19b using the yeast Pichia pastoris. Ligand-binding properties of purified OBP19b were investigated using a competitive fluorescent binding assay. We found that some—but not all— amino acids bind OBP19b in a dose-dependent manner. Using a CAFÉ behavioral assay to compare the ability of D.melanogaster wild type and OBP19b mutant, we found that these genotypes diverged in their ability to detect and discriminate these amino acids. Therefore, OBP19b may be involved in the perception of specific amino acids. 1. Jeong, Y. et al. An odorant-binding protein required for suppression of sweet taste by bitter chemicals. Neuron 79, 725–737 (2013)