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Proc Natl Acad Sci U S A. 2014 Jun 3;111(22):8269-74. doi: 10.1073/pnas.1322512111. Epub 2014 May 19.

Humidity sensation requires both mechanosensory and thermosensory pathways in Caenorhabditis elegans.

Author information

1
Institute of Cell and Molecular Biology, Center for Brain, Behavior and Evolution, Center for Learning and Memory, Waggoner Center for Alcohol and Addiction Research, and Department of Neuroscience, The University of Texas at Austin, Austin, TX 78712.
2
Institute of Cell and Molecular Biology, Center for Brain, Behavior and Evolution, Center for Learning and Memory, Waggoner Center for Alcohol and Addiction Research, and Department of Neuroscience, The University of Texas at Austin, Austin, TX 78712 jonps@austin.utexas.edu.

Abstract

All terrestrial animals must find a proper level of moisture to ensure their health and survival. The cellular-molecular basis for sensing humidity is unknown in most animals, however. We used the model nematode Caenorhabditis elegans to uncover a mechanism for sensing humidity. We found that whereas C. elegans showed no obvious preference for humidity levels under standard culture conditions, worms displayed a strong preference after pairing starvation with different humidity levels, orienting to gradients as shallow as 0.03% relative humidity per millimeter. Cell-specific ablation and rescue experiments demonstrate that orientation to humidity in C. elegans requires the obligatory combination of distinct mechanosensitive and thermosensitive pathways. The mechanosensitive pathway requires a conserved DEG/ENaC/ASIC mechanoreceptor complex in the FLP neuron pair. Because humidity levels influence the hydration of the worm's cuticle, our results suggest that FLP may convey humidity information by reporting the degree that subcuticular dendritic sensory branches of FLP neurons are stretched by hydration. The thermosensitive pathway requires cGMP-gated channels in the AFD neuron pair. Because humidity levels affect evaporative cooling, AFD may convey humidity information by reporting thermal flux. Thus, humidity sensation arises as a metamodality in C. elegans that requires the integration of parallel mechanosensory and thermosensory pathways. This hygrosensation strategy, first proposed by Thunberg more than 100 y ago, may be conserved because the underlying pathways have cellular and molecular equivalents across a wide range of species, including insects and humans.

KEYWORDS:

mechanosensation; thermosensation

PMID:
24843133
PMCID:
PMC4050571
DOI:
10.1073/pnas.1322512111
[Indexed for MEDLINE]
Free PMC Article

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