A CYCLIC NUCLEOTIDE-GATED CHANNEL INHIBITS SENSORY AXON OUTGROWTH IN LARVAL AND ADULT CAENORHABDITIS-ELEGANS - A DISTINCT PATHWAY FOR MAINTENANCE OF SENSORY AXON STRUCTURE

The tax-2 and tax-4 genes of C, elegans encode two subunits of a cycli c nucleotide-gated channel that is required for chemosensation, thermo sensation and normal axon outgrowth of some sensory neurons, Here we s how that, in tax-2 and tax-4 mutants, young larvae have superficially normal axons, but axon outgrowth resumes in inappropriate regions in l ate larval stages, Using a temperature-sensitive mutation in tax-2, we find that tax-2 activity is required during the adult stage to preser ve normal axon morphology. These results indicate that tax-2 and tax-4 are required for the maintenance of correct axon structure, and revea l an unexpected plasticity that allows C. elegans axons to be remodele d long after their initial connections have been established, TAX-2 an d TAX-4 have been proposed to form a transduction channel for chemosen sation and thermosensation, and tax-2 activity is required in the adul t stage for normal chemotaxis to NaCl and odorants, Animals mutant for the daf-11 gene have axon phenotypes that are similar to those of tax -2 and tax 4 mutants; this axon phenotype also has a late time of acti on, daf-11 regulates a developmental process called dauer larva format ion that is controlled by sensory stimuli, and tax-2 and tax-4 can eit her stimulate or inhibit dauer larva formation in different contexts.