daf-42is an evolutionarily young gene essential for dauer development inCaenorhabditis elegans

Under adverse environmental conditions, nematodes arrest into dauer, an alternative developmental stage for diapause. Dauer endures unfavorable environments and interacts with host animals to access favorable environments, thus playing a critical role in survival. Here, we report that inCaenorhabditis elegans,daf-42is essential for development into the dauer stage, as the null mutant ofdaf-42exhibited a “no viable dauer” phenotype in which no viable dauers were obtained in any dauer-inducing conditions. Long-term time lapse microscopy of synchonized larvae revealed thatdaf-42is involved in developmental changes from the pre-dauer L2d stage to the dauer stage.daf-42encodes large, disordered proteins of various sizes that are expressed in and secreted from the seam cells within a narrow time window shortly before the molt into dauer stage. Transcriptome analysis showed that the transcription of genes involved in larval physiology and dauer metabolism are highly affected by thedaf-42 mutation. Contrary to the notion that essential genes that control the life and death of an organism may well be conserved across diverse species,daf-42is an evolutionarily young gene conserved only in theCaenorhabditisgenus. Our study shows that dauer formation is a vital process that is controlled not only by conserved genes but also by newly emerged genes, providing important insights into evolutionary mechanisms.