Two independent alleles of mua-3 show temperature-dependent phenotypes
The lethality of mua-3(uy19) mutants was reduced when the mutants were grown at two lower temperatures, 15° and 20° (Figure 4, A and B). To examine whether the temperature sensitivity is specific to this mutation or could be seen in other mua-3 mutations, we tested mua-3(rh195) mutants, the only viable mua-3 mutant isolated by Bercher et al. (2001). Wild-type animals have fewer progeny at 25° than 20°. However, they do not show any sterility phenotype. On the contrary, mua-3(rh195) grew normally at 20° with reduced brood size but became completely sterile when grown at 25° due to gonadal detachment (see Figure 4, C–E for quantification of their sterility). This is a milder phenotype than that of mua-3(uy19), which dies at the L4 molt, yet both mutations show severe phenotypes at a high temperature.
Figure 4  mua-3 mutants showed temperature-dependent phenotypes. (A) mua-3(uy19) mutants do not show lethality at 15°. (B) Increase of temperature to 20° reduces survival of mua-3(uy19) mutants. (C and D) Another allele of mua-3 mutants shows temperature-dependent sterility. mua-3(rh195) mutants show a normal gonad morphology at 20° (A, white arrow) but become sterile due to detachment of the gonad at 25° (D, red arrows). (E) The sterility induced by high temperature was quantified by counting the progeny of mua-3 mutants and wild-type animals grown at 20° and 25°. ***P < 0.001 for comparison between the numbers of progeny of mua-3 at 20° and 25° by Student's t test.