Submitted to: Mechanisms of Development
Publication Type: Peer reviewed journal
Publication Acceptance Date: 9/11/2008
Publication Date: 9/2/2008
Publication URL: http://dx.doi.org/10.1016/j.mod.2008.09.002
Citation: Arakane, Y., Li, B., Muthukrishnan, S., Beeman, R.W., Kramer, K.J., Park, Y. 2008. Functional analysis of four neuropeptides, EH, ETH, CCAP and bursicon and their receptors, in adult ecdysis behavior of the red flour beetle, Tribolium castaneum. Mechanisms of Development. 125(11-12): 984-995. Doi: http://dx.doi.org/10.1016/j.mod.2008.09.002. Interpretive Summary: Insects must shed their old skins as they grow in size, but the behavior and physiology of this delicate and complex process of metamorphosis is still only poorly understood. We identified a group of hormones in the red flour beetle that are required for normal metamorphosis, and we showed that disruption of these hormones results in failure to shed the old skin, causing the death of the insect. Each of these newly-discovered hormones can become a target in screening assays for new biopesticides that disrupt insect growth and development.
Technical Abstract: Ecdysis behavior or shedding of the old cuticle in arthropods is driven by complex interactions among multiple neuropeptide signaling systems. To understand the roles of neuropeptides and their receptors in the red flour beetle, Tribolium castaneum, we performed systemic RNA interference (RNAi) utilizing post-embryonic injections of double-stranded (ds) RNAs corresponding to ten gene products representing four different peptide signaling pathways. These include eclosion hormone (EH), ecdysis triggering hormone (ETH), crustacean cardioactive peptide (CCAP) and bursicon. Behavioral modifications that resulted in lethal developmental arrests occurred as follows: 1) injection of dsRNA for eh or eth disrupted preecdysis behavior; 2) dsRNA for ccap interrupted ecdysis behavior; and 3) dsRNA for bursicon and partner of bursicon (pbur) resulted in wrinkled elytra due to incomplete wing expansion, but had no effect on cuticle tanning or viability. RNAi of the genes encoding receptors for those peptides produced phenocopies comparable to those of the respective cognate neuropeptides, except in those cases where more than one receptor was identified. These include ETH receptor-A and –B, and CCAP receptor-1 and -2. Among the multiple receptors, ETH receptor-A and CCAP receptor-2 were found to be necessary for preecdysis and ecdysis, respectively. The phenotypes resulting from neuropeptide RNAi in the beetle differ substantially from the phenotypes of the respective Drosophila mutants, indicating significant evolutionary changes in functions of neuropeptidergic systems that drive innate ecdysis behavior.