Toll-like Receptor Signaling Promotes Development and Function of Sensory Neurons Required for a C. elegans Pathogen-Avoidance Behavior

Curr Biol. 2015 Aug 31;25(17):2228-37. doi: 10.1016/j.cub.2015.07.037. Epub 2015 Aug 13.


Toll-like receptors (TLRs) play critical roles in innate immunity in many animal species. The sole TLR of C. elegans--TOL-1--is required for a pathogen-avoidance behavior, yet how it promotes this behavior is unknown. We show that for pathogen avoidance TOL-1 signaling is required in the chemosensory BAG neurons, where it regulates gene expression and is necessary for their chemosensory function. Genetic studies revealed that TOL-1 acts together with many conserved components of TLR signaling. BAG neurons are activated by carbon dioxide (CO₂), and we found that this modality is required for pathogen avoidance. TLR signaling can therefore mediate host responses to microbes through an unexpected mechanism: by promoting the development and function of chemosensory neurons that surveil the metabolic activity of environmental microbes.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Avoidance Learning
  • Caenorhabditis elegans / genetics*
  • Caenorhabditis elegans / metabolism
  • Caenorhabditis elegans Proteins / genetics
  • Caenorhabditis elegans Proteins / metabolism
  • Carbon Dioxide / metabolism
  • Cues
  • Gene Expression*
  • Nerve Tissue Proteins / genetics
  • Nerve Tissue Proteins / metabolism
  • Sensory Receptor Cells / metabolism
  • Serratia marcescens / physiology*
  • Signal Transduction*


  • Caenorhabditis elegans Proteins
  • Nerve Tissue Proteins
  • Tol-1 protein, C elegans
  • Carbon Dioxide