Hormonal Control of Pupal Commitment of Metamorphosis

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9728727 Nijhout Metamorphosis is one of the critical periods in insects development, during which an immature larva transforms into a mature adult insect. Understanding the mechanisms that control metamorphosis is of critical importance to many areas of insect physiology and development. Dr. Nijhout's current understanding of the hormonal control of metamorphosis rests largely on information derived from studies on the epidermis and general body wall. The PI has found in recent years that metamorphosis of the imaginal disks, the structures that give rise to the legs, wings, antennae, and mouthparts of the adult insect, appear to be controlled in a manner quite different from that of the general epidermis. In particular, these structures begin the developmental process of metamorphosis much earlier than the general epidermis. Imaginal disks begin metamorphosis at a time when the level of juvenile hormone (the hormone that controls the progress of development of insects) is present at high levels in the blood and is still actively inhibiting metamorphosis of the epidermis. The PI has developed a series of investigations to test an array of alternative hypotheses that could explain this divergence of physiological control of development of epidermis and imaginal disks. Among others, the PI will study the relative roles of juvenile hormone and ecdysone (the molting hormone) in controlling the expression patterns of genes associated with the early stages of metamorphic development, the relative sensitivities of imaginal disks and epidermis to these developmental hormones, and the role of cell-cell communication signals in determining the timing and spatial pattern of the developmental commitment to metamorphosis in these tissues. By providing a comparative understanding of the control of development of epidermis and imaginal disks, these studies will provide a deeper insight into the mechanisms that control of insect metamorphosis.