The G-protein coupled receptor SRX-97 is required for concentration dependent sensing of benzaldehyde in Caenorhabditis elegans

Abstract

The G-protein (heterotrimeric guanine nucleotide–binding protein)–coupled receptors in the olfactory system function to sense the surrounding environment and respond to various odorants. The genes coding for olfactory receptors in Caenorhabditis elegans are larger in number in comparison to those in mammals, suggesting complexity in the receptor–odorant relationships. Recent studies have shown that the same odorant in different concentrations could act on multiple receptors in different neurons to induce attractive or repulsive responses. The ASH neurons are known to be responsible for responding to high concentrations of volatile odorants. Here we characterize a new GPCR, SRX-97. We found that the srx-97 promoter drives expression specifically in the head ASH and tail PHB chemosensory neurons of C. elegans. Moreover, the SRX-97 protein localizes to the ciliary ends of the ASH neurons. Analysis of CRISPR-based deletion mutants of the srx-97 locus suggests that this gene is involved in recognition of high concentrations of benzaldehyde. This was further confirmed through rescue and neuronal ablation experiments. Our work brings novel insights into concentration-dependent receptor function in the olfactory system, and provides details of an additional molecule that helps the animal navigate its surroundings.

Significance Statement Although GPCRs have been known to function as chemosensory receptors, the expression pattern and function of a large number of GPCRs remains unknown. This work sheds light on the expression pattern of an uncharacterized GPCR, SRX-97. Our work shows that this protein is expressed very specifically in two sensory neuron pairs in the head and tail region and is required for concentration dependent sensing of odors in C. elegans.