Dioecious Caenorhabditis remanei and androdioecious C. elegans are two closely related species belonging to the ELEGANS group of the subgenus Caenorhabditis. Despite their distinct mating systems and evolutionary divergence, our lab has demonstrated that virgin C. remanei females secrete a potent sex-specific pheromone that attracts young adult males of both species from afar. Intriguingly, this chemotaxic behavior requires AWA and CEM neurons in male C. elegans. I will present the experiment data suggesting the requirement of the G-protein coupled receptor SRD-1 in AWA neurons in male C. elegans for sensing the pheromone secreted by C. remanei females. The srd-1 was previously reported being expressed in both AWA and ASI neurons. The sub-cellular localization of SRD-1 recepto...[ Read more ]

Dioecious Caenorhabditis remanei and androdioecious C. elegans are two closely related species belonging to the ELEGANS group of the subgenus Caenorhabditis. Despite their distinct mating systems and evolutionary divergence, our lab has demonstrated that virgin C. remanei females secrete a potent sex-specific pheromone that attracts young adult males of both species from afar. Intriguingly, this chemotaxic behavior requires AWA and CEM neurons in male C. elegans. I will present the experiment data suggesting the requirement of the G-protein coupled receptor SRD-1 in AWA neurons in male C. elegans for sensing the pheromone secreted by C. remanei females. The srd-1 was previously reported being expressed in both AWA and ASI neurons. The sub-cellular localization of SRD-1 receptor in male AWA neurons was found in the tip of cilia. Using the chemotaxis assay, we found that the srd-1 mutant males lost their pheromone responsiveness. This defect can be rescued using srd-1 cDNA driven by AWA specific promoter of gene odr-7. We visualized the excitation of AWA neurons upon treatments of multiple odors and found that AWA neurons of the srd-1 mutant males cannot be stimulated by the pheromone extract, but are responsive to other chemo-attractants. Consistent with this finding, heterologously expressing srd-1 cDNA in HEK293 FT mammalian cell line can mildly confer the host sensitivity to concentrated pheromone extract. Moreover, we employed the C. elegans ARR-1 protein from the desensitization pathway and constructed a protein complementation system with two split beta-lactamase fragments separately tagged onto ARR-1 and GPCRs (ODR-10 and SRD-1). When expressing the system in HEK293 FT cell line, we visualized the desensitization of both ODR-10 and SRD-1 upon the stimuli of diacetyl and concentrated pheromone extract, respectively, using an auto FRET substrate of beta-lactamase, CCF-2 AM. With the above evidence, we conclude that SRD-1 is one receptor responsible for sensing active sex pheromone extract component derived from virgin females of C. remanei.