Fig. 5.

Lipid metabolism-related genes were involved in heat tolerance. A–C) Survival rate in the heat tolerance assay with a double mutant that impairs lipid metabolism-related genes asm-3 and scrm-4. Worms were grown at the specified temperatures (at 20°C [A, C] and 15°C [B]) constantly from egg to adult, then transferred and incubated at 31°C for 24 h, and survival rates were calculated. Number of assays ≥ 10. ([A] n = 662, 322, 551, and 440 worms, [B] n = 2,798, 746, 3,320, and 284 worms, [C] n = 1,371, 322, 1,862, and 457 worms). D) A schematic diagram of the genetic pathway for heat tolerance. Genetic epistasis analysis of mutations in emb-4, scrm-4 lacking scramblase, and asm-3 lacking acid sphingomyelinase (ASM) suggested a genetic model for heat tolerance in which emb-4 acts at downstream of asm-3, scrm-4 acts at downstream of EMB-4, and scrm-4 and asm-3 act in the same genetic pathway. E, F) Fat content in the gut was measured by oil red O staining. Worms were cultivated at 15°C (E) or 25°C (F) from egg to adult, and then day-1 adult worms were fixed and stained with oil red O. The fat content value in each bar is a relative value to the average value of wild-type worms. ([E] n = 40, 30, 30, 30, and 30 worms, [F] n = 40, 30, 30, 30, and 30 worms). The error bars indicate SEMs. n.s. P ≥ 0.05; *P < 0.05; **P < 0.01. The comparisons were performed using one-way ANOVA followed by Tukey Kramer's post hoc tests (A–C), or followed by Dunnett's post hoc tests (E, F).