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Acute carbon dioxide avoidance in Caenorhabditis elegans
- Hallem, Elissa A., Sternberg, Paul W.
- Proceedings of the National Academy of Sciences of the United States of America 2008 v.105 no.23 pp. 8038-8043
- Caenorhabditis elegans, adults, animals, avoidance behavior, carbon dioxide, cell respiration, cyclic GMP, insulin, neural networks, neuropeptide Y, nutritional status, physiological state, predators, sensory neurons, signal transduction, transforming growth factor beta
- Carbon dioxide is produced as a by-product of cellular respiration by all aerobic organisms and thus serves for many animals as an important indicator of food, mates, and predators. However, whether free-living terrestrial nematodes such as Caenorhabditis elegans respond to CO₂ was unclear. We have demonstrated that adult C. elegans display an acute avoidance response upon exposure to CO₂ that is characterized by the cessation of forward movement and the rapid initiation of backward movement. This response is mediated by a cGMP signaling pathway that includes the cGMP-gated heteromeric channel TAX-2/TAX-4. CO₂ avoidance is modulated by multiple signaling molecules, including the neuropeptide Y receptor NPR-1 and the calcineurin subunits TAX-6 and CNB-1. Nutritional status also modulates CO₂ responsiveness via the insulin and TGFβ signaling pathways. CO₂ response is mediated by a neural circuit that includes the BAG neurons, a pair of sensory neurons of previously unknown function. TAX-2/TAX-4 function in the BAG neurons to mediate acute CO₂ avoidance. Our results demonstrate that C. elegans senses and responds to CO₂ using multiple signaling pathways and a neural network that includes the BAG neurons and that this response is modulated by the physiological state of the worm.