Development of Sensory Genomics and Basic Analysis on Taste Bioinformation Technology

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Taste is an essential sensation for any animal to keep its appropriate feeding behavior. It has also had an indispensable motivation for us to construct our traditional food cultures and develop sophisticated food industries. To have clear insights into the molecular basis of this important sensation, we have conducted the studies using genomics on taste reception and signaling. In detail, the studies are comprised of 1) analysis of taste signal transmission pathways in model fish and 2) analysis of taste signal transduction pathways in mice, with the following results. (1) We investigates the GPCR→G-protein→PLCbeta2→TRPM5 pathway and found that the taste signal effector, PLCbeta2, was expressed in medaka and zebrafish as well as in mammals. We then revealed that the taste receptors, T1RGPCRs and T2R GPCRs, and TROM5 existed in these fish as well as in humans and other vertebrates. Interestingly enough, the fish received amino acid by T1R2/3 as well as by T1R1/3 and bitter tastants by T2Rs We also tried to ligate the dominant-negative G-protein to the PLC promoter and succeeded to construct a transgenic, taste-blind medaka mutant. (2) For taste transmission studies, we constructed transgenic mice by ligation of the lectin, wheat germ agglutinin (WGA) to the T1R3 promoter, and observed the WGA signaling events in the taste bud, primary neurons, GG, NPG and TG, as well as those in NST. The observation revealed that both the WGA mRNA and the protein were expressed just in the T1R3-positive cells, with no expression in other taste cells responding to bitterness and sourness. The WGA signal was also observed in parts of neurocytes with GG, NPG and even NST, and we thus succeeded to differentially identify the taste cell→taste neuron→NST neuron pathway for sweet and umami-taste transmission.