In response to adverse environments C. elegans larvae may form stress-resistant and developmentally arrested dauer larvae. Entry into dauer interrupts developmental progression after the second larval molt (Cassada and Russell 1975), and the dauer formation decision must be coordinated with developmental pathways. Heterochronic genes control stage-specific cell fate decisions, and these genes interconnect with the dauer formation (daf) pathway in several ways. Dauer formation and daf genes affect heterochronic phenotypes, and conversely, heterochronic genes can impact dauer by controlling the timing of dauer formation, the morphology of dauer larvae, or the ability to enter dauer (Liu and Ambros 1989; Liu and Ambros 1991; Antebi et al. 1998; Tennessen et al. 2010; Karp and Ambros 2011; Karp and Ambros 2012). Here we find that the
lin-41 heterochronic gene regulates the dauer formation decision and dauer morphogenesis via its canonical target,
lin-29. The temperature-sensitive
daf-7(
e1372) allele results in constituitive dauer entry at 25˚C, and the allele is a useful tool for controlling dauer entry (Vowels and Thomas 1992; Karp 2018). While performing experiments examining the role of
lin-41 during dauer, we observed that
lin-41(0);
daf-7 worms rarely entered dauer. To better understand this phenotype, we quantified the number of dauer and nondauer larvae in synchronous populations of
daf-7(
e1372) larvae grown at the dauer-inducing temperature of 24˚C.
lin-41(0) mutants are sterile, and therefore the strain must be propagated as a heterozygote (Slack et al. 2000). We took advantage of a closely linked transgene, nIs408[LIN-29::mCherry,
ttx-3::gfp] to balance
lin-41(0) (Harris and Horvitz 2011).
lin-41(0) homozygous larvae were identified by the absence of fluorescence. Controls included nIs408-positive siblings, 2/3 of which should be
lin-41(0)/nIs408 and 1/3 of which should be nIs408/nIs408, as well as a strain that is homozygous for the wild-type allele of
lin-41.