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Appl. Chem. Vol. 74, No. 7, pp.
Pure and Applied Chemistry
Vol. 74, Issue 7
Drosophila sweet taste receptor*
Kunio Isono1,**, Kohei Ueno2, Masayuki Ohta1,
and Hiromi Morita1
1Tohoku University, Graduate School of Information
Sciences, Sendai 980-8579, Japan; 2Institute of Behavioral Sciences,
Gunma University School of Medicine, Maebashi 371-8511, Japan
Abstract: Like the Sac locus controlling sugar sensitivity
in mice, the taste gene Tre of the fruitfly Drosophila
was discovered in wild populations as a genetic dimorphism controlling
gustatory sensitivity to a sugar trehalose. By activating a P-element
transposon near the gene locus we obtained induced Tre mutations
and analyzed the associated changes in gene organizations and the mRNA
expressions. The analysis showed that Tre is identical to Gr5a,
a gene that belongs to a novel seven-transmembrane receptor family expressed
in chemosensory neurons and predicted to encode chemosensory receptors.
Thus, Gr5a is a candidate sweet taste receptor in the fly. An
amino acid substitution in the second intracellular loop domain was
identified to be functionally correlated with the genetic dimorphism
of Tre. Since Tre controls sweet taste sensitivity to
a limited subset of sugars, other Gr genes phylogenetically related
to Tre may also encode sweet taste receptors. Those candidate
sweet taste receptors, however, are phylogenetically distinct from vertebrate
sweet taste receptors, suggesting that the sweet taste receptors in
animals do not share a common origin.
* A special topic issue on the science
** Corresponding author.
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