The gene plays a vital role at the start of metamorphosis for subsequent adult emergence.

The () gene has been extensively studied in many species for its functions in development, physiology, and behavior. It is common for genes that influence behavior and development to be essential genes, and has been found to be an essential gene in both fruit flies and mammals, with mutants dying before reaching the adult stage. However, the biological process underlying the lethality associated with this gene is not known. Here, we show that in , some but not all gene products of are essential for survival. Specifically, we show that promoter 3 of , but not promoters 1, 2, and 4 are required for survival past pupal stage. We use full and partial genetic deletions of , and temperature-restricted knock-down of the gene to further investigate the stage of lethality. While deletion analysis shows that flies lacking die at the end of pupal development, as pharate adults, temperature-restricted knock-down shows that is only required at the start of pupal development, for normal adult emergence (AE) and viability. We further show that the inability of these mutants to emerge from their pupal cases is linked to deficiencies in emergence behaviors, caused by a possible energy deficiency, and finally, that the lethality of mutants seems to be linked to protein isoform P3, transcribed from promoter 3.