Corazonin Neurons Function in Sexually Dimorphic Circuitry That Shape Behavioral Responses to Stress in Drosophila Yan Zhao 1 , Colin A. Bretz1, Shane A. Hawksworth1¤, Jay Hirsh2, Erik C. Johnson 1 * 1 Department of Biology, Wake Forest University, Winston-Salem, North Carolina, United States of America, 2 Department of Biology, University of Virginia, Charlottesville, Virginia, United States of America Abstract All organisms are confronted with dynamic environmental changes that challenge homeostasis, which is the operational definition of stress. Stress produces adaptive behavioral and physiological responses, which, in the Metazoa, are mediated through the actions of various hormones. Based on its associated phenotypes and its expression profiles, a candidate stress hormone in Drosophila is the corazonin neuropeptide. We evaluated the potential roles of corazonin in mediating stress- related changes in target behaviors and physiologies through genetic alteration of corazonin neuronal excitability. Ablation of corazonin neurons confers resistance to metabolic, osmotic, and oxidative stress, as measured by survival. Silencing and activation of corazonin neurons lead to differential lifespan under stress, and these effects showed a strong dependence on sex. Additionally, altered corazonin neuron physiology leads to fundamental differences in locomotor activity, and these effects were also sex-dependent. The dynamics of altered locomotor behavior accompanying stress was likewise altered in flies with altered corazonin neuronal function. We report that corazonin transcript expression is altered under starvation and osmotic stress, and that triglyceride and dopamine levels are equally impacted in corazonin neuronal alterations and these phenotypes similarly show significant sexual dimorphisms. Notably, these sexual dimorphisms map to corazonin neurons. These results underscore the importance of central peptidergic processing within the context of stress and place corazonin signaling as a critical feature of neuroendocrine events that shape stress responses and may underlie the inherent sexual dimorphic differences in stress responses. Citation: Zhao Y, Bretz CA, Hawksworth SA, Hirsh J, Johnson EC (2010) Corazonin Neurons Function in Sexually Dimorphic Circuitry That Shape Behavioral Responses to Stress in Drosophila. PLoS ONE 5(2): e9141. doi:10.1371/journal.pone.0009141 Editor: Michael N. Nitabach, Yale School of Medicine, United States of America Received June 2, 2009; Accepted January 22, 2010; Published February 10, 2010 Copyright: 2010 Zhao et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: This work was funded by the Science Research Fund, Wake Forest University, and NSF IOS 092931 to ECJ. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. * E-mail: johnsoec@wfu.edu ¤ Current address: Boston University School of Medicine, Boston, Massachusetts, United States of America Introduction Stress is defined as any challenge to the maintenance of homeostasis that produces adaptive behavioral and/or physiolog- ical responses [1]. Dynamic environments place significant constraints upon living systems to adapt and meet these challenges. There is significant central processing of these responses to stress, allowing for differential controls targeting different behavioral and physiological outputs. In mammals, one transmitter linked to central processing of stress is the corticotropin releasing factor (CRF). Levels of CRF transcript increase in response to many different types of stressors [2]. A major action of CRF is the control of ACTH secretion, which in turn increases the production of cortisol, which produces a multiplicity of different responses dependent upon cellular identity [3]. Another prominent action of CRF is the stress-induced inhibition of Gonadotropin releasing hormone (GnRH) signaling [4]. The corazonin neuropeptide was originally discovered based on its potent cardioacceleratory actions in the cockroach, Periplaneta [5]. Provocatively, in the locusts Locusta migratoria and Shistocerca gregaria, this hormone has been found to be the causal agent underlying gregarious phase pigmentation [6]. Additionally, the corazonin peptide has been shown to be co-expressed in clock cells in Manduca sexta, [7] and also in this same insect, coordinates the onset of the ecdysial behavioral program [8]. So, while it is recognized that corazonin is a highly conserved neuropeptide throughout the insects, a unifying theme to connect these different functions associated with corazonin has been lacking. In Drosophila, cells that express corazonin also express receptor molecules for two unrelated diuretic hormones, DH44 and DH31 [9]. The significance of this finding is that, by virtue of receptor similarities, DH44 and DH31 are related to CRF and CGRP (Calcitonin-Gene Related Peptide) respectively, both of which are established mammalian stress hormones [10–11]. Furthermore, the corazonin neuropeptide binds to a receptor belonging to the GnRH receptor family [12–13]. In the mammalian hypothalamus, GnRH cells express the receptors for both CRF and CGRP and are involved in the stress-induced suppression of GnRH release [4]. We reasoned that these disparate phenotypes of corazonin might be unified under the umbrella of a stress response pathway. For example, changes in locust pigmentation during gregarious conditions are thought to be a consequence of nutrient deprivation [14]. The ecdysis behavioral program is a critical developmental PLoS ONE | www.plosone.org 1 February 2010 | Volume 5 | Issue 2 | e9141