The G-Protein-Coupled Receptor SRX-97 Is Required for Concentration-Dependent Sensing of Benzaldehyde in Caenorhabditis elegans

The SRX-97 transmembrane domain and CRISPR/Cas9 generated mutation of srx-97. A, Amino acid sequence showing the predicted seven transmembrane domain of SRX-97. B, Exonic structure of the srx-97 gene with the red line showing the CRISPR/Cas9 deletion obtained. The deletion encompasses the gene from the 61st base pair to the 1895th base pair including part of the 3′ UTR of the gene. C, Amplification of the chromosomal region showing the deletion of the srx-97 gene (2730 bp) using CRISPR/Cas9 compared with control WT (4566 bp) gene. A 1-kb DNA ladder was used in the line marked Marker (M). Extended Data Figure 2-1 supports this figure.

Behavior of srx-97 mutant animals toward water-soluble and volatile chemicals. A, Graph showing the delay in avoidance response toward a dry spot of 2 m glycerol in WT, srx-97, and odr-3 mutant animals. The number of animals assayed for each genotype is indicated at the base of each plot for panels A–D. B, Graph showing the delay in avoidance toward a dry spot of 0.1% SDS in WT, srx-97, and odr-3 mutant animals. C, Graph showing the delay in avoidance toward a dry spot of 10 mm CuSO₄ in WT, srx-97, and odr-3 mutant animals. D, Graph showing the percentage of avoidance on nose touch stimuli of WT, srx-97, and glr-1 mutant animals. The numbers at the base of graphs in A–D indicate the number of animals tested for each genotype. E, Graph indicating the negative chemotaxis indices of WT, srx-97, and odr-3 mutant animals toward the repellent octanol. The assay was done in triplicates over multiple days for all chmotaxis assays. Each dot indicates an assay done in triplicate for all graphs from E–H. F, Chemotaxis indices toward high concentrations (10⁻¹) of DA and IAA. G, Chemotaxis indices toward multiple concentrations of benzaldehyde. H, Chemotaxis indices toward high concentrations of benzaldehyde in WT, srx-97, and rescue strains of srx-97. This rescue experiments used SRX-97 under its own promoter and under the osm-10 promoter. Animals that did not show expression of the arrays (NA, no array) were used as controls in these experiments. The error bars represent SEM, and statistical significance is represented as “ns” for not significant, *p < 0.05, **p < 0.01, ***p < 0.001. The numbers at the base of each graph from E–H indicates the total number of times the experiment was performed with 50–150 animals used in each trial. Extended Data Figure 3-1 supports this figure.

Ablation of ASH neurons shows defects toward chemosensation to benzaldehyde. A, Illustration of the design of the plates used for analyzing the chemotaxis frequency of C. elegans along with the formula used for this calculation. Each sector (a–d) is 1 cm in width. B, Graph of chemotaxis frequencies of WT, srx-97, the srx-97 rescue line and a control odr-3 mutant line to a high concentration of benzaldehyde. The assay was performed in triplicate over multiple days with each dot indicating an assay done in triplicate. The numbers at the base of each plot indicate the number of times the experiment was performed with each genotype. C, Graph plotting the delay in response of animals toward a high benzaldehyde concentration. The animals used in this experiment have undergone mock ablation or ASH ablation in WT or srx-97 mutant backgrounds. Each dot indicates a response from a single animal. Approximately 25 mock ablated animals and ASH ablated animals in WT and srx-97 mutant background were analyzed for this experiment over multiple days. The error bars represent SEM, and statistical significance is represented as “ns” for not significant; *p < 0.05, **p < 0.01, ***p < 0.001.