Genetic Analysis of Ecdysis Behavior inDrosophilaReveals Partially Overlapping Functions of Two Unrelated Neuropeptides

Abstract

Ecdysis behavior allows insects to shed their old exoskeleton at the end of every molt. It is controlled by a suite of interacting hormones and neuropeptides, and has served as a useful behavior for understanding how bioactive peptides regulate CNS function. Previous findings suggest that crustacean cardioactive peptide (CCAP) activates the ecdysis motor program; the hormone bursicon is believed to then act downstream of CCAP to inflate, pigment, and harden the exoskeleton of the next stage. However, the exact roles of these signaling molecules in regulating ecdysis remain unclear. Here we use a genetic approach to investigate the functions of CCAP and bursicon in Drosophila ecdysis. We show that null mutants in CCAP express no apparent defects in ecdysis and postecdysis, producing normal adults. By contrast, a substantial fraction of flies genetically null for one of the two subunits of bursicon [encoded by the partner of bursicon gene (pburs)] show severe defects in ecdysis, with escaper adults exhibiting the expected failures in wing expansion and exoskeleton pigmentation and hardening. Furthermore, flies lacking both CCAP and bursicon show much more severe defects at ecdysis than do animals null for either neuropeptide alone. Our results show that the functions thought to be subserved by CCAP are partially effected by bursicon, and that bursicon plays an important and heretofore undescribed role in ecdysis behavior itself. These findings have important implications for understanding the regulation of this vital insect behavior and the mechanisms by which hormones and neuropeptides control the physiology and behavior of animals.

CCAP and FMRFamide-like peptides accelerate the contraction rate of the antennal accessory pulsatile organs (auxiliary hearts) of mosquitoes

“…This neuropeptide was discovered in the shore crab, Carcinus maenas, where it was shown to have a potent cardioacceleratory effect on semi-isolated heart preparations (Stangier et al, 1987). In insects, CCAP functions in ecdysis, hormone release and the contraction of visceral organs (Veelaert et al, 1997;Donini et al, 2001;Ewer and Reynolds, 2002;Sakai et al, 2004;Arakane et al, 2008;Lahr et al, 2012), and more relevant to the present study, CCAP is cardioacceleratory in both holometabolous and hemimetabolous insects (Furuya et al, 1993;Lehman et al, 1993;Wasielewski and The ampulla of an antennal APO propels hemolymph in the upward direction via an antennal vessel. When hemolymph reaches the distal end of the appendage, it is released into a wider antennal hemocoel and it flows in the downward direction as it returns to the head.…”

Neuromolecular responses to social challenge: Common mechanisms across mouse, stickleback fish, and honey bee

“…Mouse GPCRs included a dopamine receptor (Drd1a) and an adenosine receptor (Adora2a) associated with human panic disorders (13). Honey bee GPCRs included CcapR and hormone receptor EthR, which are responsive to ecdysone (14,15) (Table S1). Fz2, a Wnt-activated receptor, was another GPCR identified in honey bee.…”

Targeted inactivation of the rickets receptor in muscle compromisesDrosophilaviability

“…In fact, global knockdown of rk in vivo using RNAi results in developmental arrest, rather than just impaired wing expansion, melanization and cuticle hardening (Loveall and Deitcher, 2010). A recent study also showed that deletion of the bursicon β-subunit results in significant lethality throughout pupariation, specifically during ecdysis (Lahr et al, 2012;Loveall and Deitcher, 2010).…”

“…We subsequently used a series of Gal4 driver lines to target our tethered ligand to selected tissues and thus define the critical cell type(s) that requires rk and underlies the lethality/wing expansion phenotypes (Table 1). Although many studies have focused on the spatial and temporal release of bursicon (Lahr et al, 2012;Peabody et al, 2008;Peabody et al, 2009), the localization of the bursicon receptors that are essential for survival has remained elusive. Our study strongly supports that a peripheral rk, localized in muscle, plays an important role in Drosophila development.…”