A receptor-type guanylate cyclase is required for carbon dioxide sensation by C. elegans

Carbon dioxide (CO2) is both a critical regulator of animal physiology and an important
sensory cue for many animals for host detection, food location, and mate finding. The
free-living soil nematode C. elegans demonstrates CO2-avoidance behavior, which
requires a pair of ciliated sensory neurons, the BAG neurons. Using in vivo calcium
imaging, we show that CO2 specifically activates the BAG neurons and that the CO2-
sensing function of BAG neurons requires TAX-2/TAX-4 cyclic nucleotide-gated ion
channels and the receptor-type guanylate cyclase GCY-9. Our results delineate a
molecular pathway for CO2 sensing and suggest that activation of a receptor-type
guanylate cyclase is an evolutionarily conserved mechanism by which animals detect
environmental CO2.