Autocrine regulation of ecdysone synthesis by β3-octopamine receptor in the prothoracic gland is essential for Drosophila metamorphosis

Metamorphosis is an important biological process by which animals alter their body structures to become sexually mature adults. We discovered that tyramine signaling through the β3-octopamine receptor plays an essential role in producing the steroid hormone ecdysone, which is critical for metamorphosis. Based on our observations, we propose that monoamine signaling acts downstream of a body size checkpoint that allows metamorphosis to occur only when a critical body weight is attained during larval development and nutrients are sufficiently abundant. This work also provides a new perspective on an evolutionarily conserved monoaminergic regulation of steroid hormone production during developmental transitions such as metamorphosis. This study provides a new understanding of how metamorphosis is coordinately regulated by nutritional conditions and developmental timing.