Molecular basis of fatty acid taste in <i>Drosophila</i>.

Ahn, Ji-Eun; Chen, Yan; Amrein, Hubert · Elife · 2017

basic_science · Level V

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Abstract

Behavioral studies have established that <i>Drosophila</i> appetitive taste responses towards fatty acids are mediated by sweet sensing Gustatory Receptor Neurons (GRNs). Here we show that sweet GRN activation requires the function of the <i>Ionotropic Receptor</i> genes <i>IR25a</i>, <i>IR76b</i> and <i>IR56d</i>. The former two <i>IR</i> genes are expressed in several neurons per sensillum, while <i>IR56d</i> expression is restricted to sweet GRNs. Importantly, loss of appetitive behavioral responses to fatty acids in <i>IR25a</i> and <i>IR76b</i> mutant flies can be completely rescued by expression of respective transgenes in sweet GRNs. Interestingly, appetitive behavioral responses of wild type flies to hexanoic acid reach a plateau at ~1%, but decrease with higher concentration, a property mediated through IR25a/IR76b independent activation of bitter GRNs. With our previous report on sour taste, our studies suggest that IR-based receptors mediate different taste qualities through cell-type specific IR subunits.

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