Animals suffer many stresses from natural environment. For their survival, it is important that animals can avoid harmful conditions and can resist these stresses. In C. elegans, insulin-signaling pathway regulates resistance to heat shock stress, oxidative stress, and UV stress via DAF-16 transcriptional factor, while mutants difective in MAP kinase pathway are more sensitive to high osmolarity conditions than wild type. A body of C. elegans is covered by cuticles, which is a border between external and internal environment. Therefore, cuticles must play important roles for stress resistance. We found that
osm-7(
n1515) shows strong resistance to high osmolarity.
osm-7 was isolated by Thormas and Horvitz as a mutant which shows a defect in osmotic avoidance.
osm-7 worms are able to survive on a plate containing 800mM NaAc, whereas wild type animals can not survive more than a few minutes. Positional cloning of
osm-7 reveals that OSM-7 consists of 651 amino acid residues with a signal peptide, suggesting that OSM-7 is a secretory protein. Expression studies using a
osm-7;;gfp translational fusion, which can rescue all the phenotypes of
osm-7, suggest that OSM-7 is localized in cuticles. Expression of
osm-7 in hypodermis is sufficient to restore the sensitivity to high osmolarity, but expression in neurons is not. To examine whether
osm-7 related insulin-signaling pathway or not, we made a double mutant,
osm-7;
daf-16 and found that this double mutant still has resistance to high osmolarity as
osm-7 single mutant, indicating that
osm-7 is not involved in the insulin-signaling pathway. To examine whether
osm-7 can resist other stresses than high osmolarity, we analyzed response to high concentration of oxygen, and found that
osm-7 is highly sensitive to oxygen like
mev-1(
kn1) mutant. Although
mev-1 mutant has a shorter life span than N2,
osm-7 mutant has a slightly expanded life span. These results implicate that OSM-7 is not involved in sensitivity to intracellular oxidative stress but it is involved in permeability of oxygen through cuticles. We suppose that not only stress responses but also properties of cuticles may affect sensitivity to environmental stresses.