Evidence for a conserved CCAP-signaling pathway controlling ecdysis in a hemimetabolous insect, Rhodnius prolixus

Abstract

A vital feature in the success of Ecdysozoa is their ability to shed their exoskeleton (a process called ecdysis) such that they can grow or change their morphology. In holometabolous insects, these behaviors are orchestrated by the sequential actions of neuropeptides, one of which is crustacean cardioactive peptide (CCAP). Little is known about the control of ecdysis in hemimetabolous insects. Here, we report that CCAP is essential for successful ecdysis in the hemimetabolous insect, Rhodnius prolixus; the vector of Chagas disease. The first indication of CCAP's involvement in ecdysis was the observation of decreased staining intensity of CCAP-containing neurons immediately following ecdysis, indicative of the release of CCAP. The critical importance of the CCAP signaling pathway was further demonstrated by knockdown (as determined by qPCR and immunohistochemistry) of the CCAP and CCAPR transcripts utilizing dsRNA. This technique reduced the staining intensity of CCAP-containing neurons, and knocked down the transcript levels by up to 92%, with lethal consequences to the insect. Insects with these transcripts knocked down had very high mortality (up to 84%), typically at the expected time of the ecdysis sequence, or had ecdysis extremely delayed. This is the first report of the susceptibility of R. prolixus to dsRNA knockdown of neuropeptide and receptor transcripts, and the data clearly demonstrates the conserved nature of the CCAP signaling pathway in ecdysis between holometabolous and hemimetabolous insects.

Peptidomics of Neuropeptidergic Tissues of the Tsetse FlyGlossina morsitans morsitans

“…It is a pleiotropic neuropeptide, mediating numerous processes. Besides promoting cardiac muscle contractions, it is involved in initiating ecdysis, stimulating digestive secretions, and stimulating visceral muscles [53][54][55][56]. Our study failed to detect the mature PFCNAFTGCa, but did show the presence of CCAPprecursor-derived spacer peptides in the CNS and PM.…”

Ecdysis behaviors and circadian rhythm of ecdysis in the stick insect, Carausius morosus

“…The CCAP expressing cells (commonly called Cells 27) have a unique morphology first described by Dircksen (1991; 1998). These CCAP neurons have been suggested to be the targets of EH action via cGMP during ecdysis (Gammie and Truman, 1999), and CCAP has been shown to regulate ecdysis in the hemimetabolous insect R. prolixus (Lee et al, 2013). Furthermore, CCAP has been identified in C. morosus by HPLC (Predel et al, 1999), and the CCAP immunoreactive neurons show a homologous morphology in all insects investigated so far and have been designated as Cells27/IN704 (Zitnan and Adams, 2012).…”

Molecular Identification of Cysteine and Trypsin Protease, Effect of Different Hosts on Protease Expression, and Rnai Mediated Silencing of Cysteine Protease Gene in the Sunn Pest

“…Cytochrome P dsRNA shortened the life span of D. citri . In the other hemipteran, Rhodnius prolixus , knocked down of crustacean cardioactive peptide by dsRNA had up to 84% mortality (Lee et al., ). Meanwhile, in this hemipteran insect, injection of chitin synthase dsRNA reduced transcript levels and oviposition, also caused reduction of ovary size, deformed eggs, and ecdysis abnormalities (Mansur et al., ).…”