Insights into the Function and Evolution of Taste 1 Receptor Gene Family in the Carnivore Fish Gilthead Seabream ().

A plethora of molecular and functional studies in tetrapods has led to the discovery of multiple taste 1 receptor () genes encoding G-protein coupled receptors () responsible for sweet ( + ) and umami ( + ) taste. In fish, the gene family repertoires greatly expanded because of several gene duplications, and recent studies have shown functional divergence from canonical mammalian sweet taste perceptions, putatively as an adaptive mechanism to develop distinct feeding strategies in highly diverse aquatic habitats. We addressed this question in the carnivore fish gilthead seabream (), a model species of aquaculture interest, and found that the gene repertoire consists of eight members including , and six - gene duplicates, adding further evidence to the evolutionary complexity of fish families. To analyze taste functions, we first developed a stable gene reporter system based on Ca-dependent calcineurin/ signaling to examine specifically in vitro the responses of a subset of heterodimers to L-amino acids (L-AAs) and sweet ligands. We show that although differentially tuned in sensitivity and magnitude of responses, /, / and / may equally serve to transduce amino acid taste sensations. Furthermore, we present preliminary information on the potential involvement of the G protein alpha subunits and in taste signal transduction.