Metamorphosis is a remarkable period during insect development that marks the transition from larval to adult life. The transformation of the animal during the non-feeding pupal stage is characterized by the destruction of most larval tissues and by the construction of the adult. The principle energy reserves to fuel this process reside in the pupal fat cells. The origin of these cells is unique, as they are larval fat cells which escape destruction. Upon completion of pupal development, these larval-derived fat cells continue to be an energy reservoir for the young adult. The overall goal of the research is to understand the role of the fat cells in regulating pupal development at the organismal, developmental, and cellular level. By genetic manipulations, the nutritional content of larval fat cells will be altered and the mechanisms by which the pupa adjusts to fulfill its energetic needs examined, and the energetic consequences of pupal development on the young adult determined. Genes from two cellular pathways, Ecdysone and Insulin signaling, have been identified as likely candidates important in metabolic regulation. This project will test the hypothesis that fat cells respond to the metabolic needs of the pupa and, through input from Ecdysone and Insulin signaling, monitor and regulate the release of energy to support development, while still maintaining energy reservoirs necessary for survival of the young adult. This metabolic regulation is essential for successful metamorphosis. This is a collaborative proposal between two labs with complementary expertise in developmental genetics and organismal physiology. Both labs have vigorous undergraduate research programs that have resulted in numerous conference presentations and co-authored journal articles by undergraduates. These activities will continue under this award, as will graduate training which will emphasize an interdisciplinary approach and highlight the use of cellular, molecular, and genetics techniques in understanding organismal physiology.