740A Poster - 12. Physiology, metabolism and aging
Thursday April 07, 2:00 PM - 4:00 PM

Authors:
George Kapali ¹; Viviane Callier ²; Samuel Gascoigne ³; Jon Harrison ²; Alexander Shingleton ^1,3

Affiliations:
1) University of Illinois at Chicago, Chicago, IL; 2) Arizona State University, Tempe, AZ; 3) Lake Forest College, Lake Forest, IL

Keywords:
a. stress responses; n. hormonal control

In almost all animals, physiologically low oxygen (hypoxia) during development slows growth and reduces adult body size. The developmental mechanisms that determine growth under hypoxic conditions are, however, poorly understood. Here we show that the growth and body size response to moderate hypoxia (10% O₂) in Drosophila melanogaster is systemically regulated via the steroid hormone ecdysone. Levels of circulating ecdysone are elevated under hypoxia, and inhibition of ecdysone synthesis ameliorates the negative effect of low oxygen on growth rate. We also show that the effect of ecdysone on growth rate under hypoxic conditions is mediated by the insulin/IGF-signaling (IIS) pathway. Hypoxia reduces systemic IIS activity and the hypoxic growth-response is eliminated in larvae with suppressed IIS. Critically, hypoxia transiently increases the expression of Imp-L2, an ecdysone-response gene that suppresses systemic IIS. Inhibition of ecdysone synthesis eliminates this increase in Imp-L2 expression, while loss of Imp-L2 significantly reduces the negative effect of hypoxia on final body size. Collectively, these data indicate that growth suppression in hypoxic Drosophila larvae is accomplished by systemic endocrine mechanisms that overlap with mechanisms that regulate growth in response to low nutrition. This suggests the existence of growth-regulatory stress response mechanisms that respond to general environmental perturbation rather than individual environmental factors.