Abstract
Summary The nematode Caenorhabditis elegans utilizes chemosensation to navigate an ever-changing environment for its survival. A class of secreted small-molecule pheromones, termed ascarosides, play an important role in olfactory perception by affecting biological functions ranging from development to behavior. The ascaroside ascr#8 mediates sex-specific behaviors, driving avoidance in hermaphrodites and attraction in males. Males sense ascr#8 via the ciliated male-specific cephalic sensory (CEM) neurons, which exhibit radial symmetry along dorsal-ventral and left-right axes. Calcium imaging studies suggest a complex neural coding mechanism that translates stochastic physiological responses in these neurons to reliable behavioral outputs. To test the hypothesis that neurophysiological complexity arises from differential expression of genes, we performed cell-specific transcriptomic profiling; this revealed between 18 and 62 genes with at least two-fold higher expression in a specific CEM neuron type versus both other CEM neurons and adult males. These included two G protein coupled receptor (GPCR) genes, srw-97 and dmsr-12, that were specifically expressed in non-overlapping subsets of CEM neurons and whose expression was confirmed by GFP reporter analysis. Single CRISPR-Cas9 knockouts of either srw-97 or dmsr-12 resulted in partial defects, while a double knockout of both srw-97 and dmsr-12 completely abolished the attractive response to ascr#8. Together, our results suggest that the evolutionarily distinct GPCRs SRW-97 and DMSR-12 act non-redundantly in discrete olfactory neurons to facilitate male-specific sensation of ascr#8.
Competing Interest Statement
The authors have declared no competing interest.
Footnotes
This revised version addresses all the concerns raised in the original submission of the manuscript. Specifically, in the current version, we: 1. computed a new RNA-seq differential expression analysis by comparing our CEM RNA-seq data to male-specific C. elegans RNA-seq data published by Thomas et al. (2012; PubMed 23103191). These analyses allowed us to determine that genes we scored as CEM-specific maintained this status when tested against bulk gene expression of adult C. elegans males (New Figure 1). 2. quantified that the two receptors (srw-97 and dmsr-12) are expressed in non-overlapping subsets of CEM neurons (New Figure 3C-D; Supplementary Table S7) 3. co-localized our receptors with known CEM markers (klp-6) to demonstrate that our receptors are expressed in CEM neurons 4. added gene structures of both receptors (srw-97 and dmsr-12) (Supplementary Figure S5)
