Meeting Abstract
All living organisms require moisture for cellular and other essential processes, which often directly relates to the moisture content of their environments. Despite its significance to survival, little is understood about the mechanism through which variation in humidity is sensed and transduced. The successful examination of a variety of other sensory modalities in the nematode Caenorhabditis elegans makes this model organism an ideal candidate for our study of humidity sensation. Changes in humidity affect these soft-bodied invertebrates, which are vulnerable to both dessication and overhydration. Using a novel assay to test the ability of worms to migrate in a humidity gradient (hygrotaxis), we found that C. elegans can sense very slight changes in humidity, and demonstrate behavioral plasticity in response to a humidity gradient. Worms preferentially migrated down the humidity gradient of a chamber when starved. The FLP neuronal pair has been identified as the mechanosensory contributor to this integrative sensory system, operating through the conserved DEG/ENaC/ASIC mechanoreceptor complex. A second neuron pair, namely AFDs, has demonstrated a role in thermosensation through cGMP-gated channel signaling, detecting differential evaporative cooling from the worms along the humidity gradient. In both the FLP and AFD neuron pairs, mutations and genetic ablations wholly or partially eliminated hygrotactic behavior. The presence of similar neurons and orthologous proteins in other animals, including humans, enable the possibility that this may be a highly conserved mechanism for hygrosensation.
