Targets of TGF-beta signaling in Caenorhabditis elegans dauer formation.
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.
Inoue
T
T
Department of Genetics, University of Washington, Seattle, Washington, 98195, USA.
Thomas
J H
JH
D000483:Alleles; D000595:Amino Acid Sequence; D000818:Animals; D030801:Animals, Genetically Modified; D017173:Caenorhabditis elegans / Q000235:genetics / Q000378:metabolism*; D029742:Caenorhabditis elegans Proteins; D003001:Cloning, Molecular; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics*; D049452:Green Fluorescent Proteins; D008164:Luminescent Proteins / Q000235:genetics; D008969:Molecular Sequence Data; D009030:Mosaicism; D011401:Promoter Regions, Genetic; D011993:Recombinant Fusion Proteins / Q000235:genetics; D015398:Signal Transduction; D051785:Smad Proteins; D015534:Trans-Activators / Q000737:chemistry / Q000235:genetics*; D016212:Transforming Growth Factor beta / Q000378:metabolism*
D029742:Caenorhabditis elegans Proteins; C403466:DAF-14 protein, C elegans; D004268:DNA-Binding Proteins; D008164:Luminescent Proteins; D011993:Recombinant Fusion Proteins; D051785:Smad Proteins; D015534:Trans-Activators; D016212:Transforming Growth Factor beta; D049452:Green Fluorescent Proteins