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Dev Biol. 2000 Jan 1;217(1):192-204.

Targets of TGF-beta signaling in Caenorhabditis elegans dauer formation.

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Department of Genetics, University of Washington, Seattle, Washington, 98195, USA.


Caenorhabditis elegans dauer formation is controlled by multiple environmental factors. The chemosensory neuron ASI regulates dauer formation by secretion of DAF-7/TGF-beta, but the molecular targets of the DAF-7 ligand are incompletely defined and the cellular targets are unknown. We genetically characterized and cloned a putative transducer of DAF-7 signaling called daf-14 and found that it encodes a Smad protein. DAF-14 Smad has a highly unusual structure completely lacking the N-terminal domain found in all other Smad proteins known to date. daf-14 genetically interacts with daf-8, which encodes another Smad, and the interaction suggests partial functional redundancy between these two Smad proteins. We also studied the cellular targets of DAF-7 signaling by studying the sites of action of daf-14 and daf-4, the putative receptor for DAF-7. daf-14::gfp is expressed in multiple tissues that are remodeled during dauer formation. However, analysis of mosaics generated by free duplication loss and tissue-specific expression constructs indicate cell-nonautonomous function of daf-4, arguing against direct DAF-7 signaling to tissues throughout the animal. Instead, these experiments suggest the nervous system as a target of DAF-7 signaling and that the nervous system in turn regulates dauer formation by other tissues.

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