Interorgan communication in the control of metamorphosis

Steroid hormones control major developmental transitions such as metamorphosis in insects and puberty in mammals. The juvenile must attain a sufficient size before it begins maturation in order to give rise to a properly sized and reproductively fit adult. Studies in the insect Drosophila have begun to reveal a remarkable example of the complex interplay between different organs and the neuroendocrine system that controls the production of the steroid ecdysone, which triggers metamorphosis. This review discusses the inter-organ signals mediating this crosstalk, which allows the neuroendocrine system to assess nutrient availability and growth status of internal organs, ensuring that maturation is initiated at the appropriate time. We discuss how the neuroendocrine system integrates signals from different tissues to coordinate growth and maturation. These studies are still unraveling the organ-to-organ signaling networks that control the timing of metamorphosis, defining important principles underlying the logic of growth and maturation coordination in animals.