Positive Selection of Caenorhabditis elegans Mutants With Increased Stress Resistance and Longevity

We developed selective conditions for long-lived mutants of the nematode Caenorhabditis elegans by subjecting the first larval stage (L1) to thermal stress at 30° for 7 days. The surviving larvae developed to fertile adults after the temperature was shifted to 15°. A total of one million F2 progeny and a half million F3 progeny of ethylmethanesulfonate-mutagenized animals were treated in three separate experiments. Among the 81 putative mutants that recovered and matured to the reproductive adult, 63 retested as thermotolerant and 49 (80%) exhibited a >15% increase in mean life span. All the known classes of dauer formation (Daf) mutant that affect longevity were found, including six new alleles of daf-2, and a unique temperature-sensitive, dauer-constitutive allele of age-1. Alleles of dyf-2 and unc-13 were isolated, and mutants of unc-18, a gene that interacts with unc-13, were also found to be long lived. Thirteen additional mutations define at least four new genes.