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Title: Corazonin in insects

item Nachman, Ronald

Submitted to: Peptides
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/19/2006
Publication Date: 1/15/2007
Citation: Predel, R., Neupert, S., Russell, W.K., Schreibner, O., Nachman, R.J. 2007. Corazonin in insects. Peptides. 28:3-10.

Interpretive Summary: Because of problems with the development of resistance to conventional pesticides, there is a critical need for new concepts and alternative approaches in controlling insect pests. The basic premise of this research is that neuropeptides (short chains of amino acids) serve as potent messengers in insects to regulate vital functions. New, selective control measures may be developed by designing metabolically stable mimics of these neuropeptides that actively inhibit or over-stimulate functions regulated by them, resulting in disruption of the internal environment of the insect. We report on the discovery of a novel form (only the fourth known in nature) of the corazonin class of neuropeptides from a fly using state-of-the-art analytical techniques. In addition, the same analytical techniques are marshaled to catalog corazonin forms among a broad range of insect groups. Interestingly, one form of corazonin is uniquely found in bees, an important beneficial group of insects. The fact that different forms of corazonin are used by pest and beneficial insects to regulate critical life processes increases the likelihood that control measures based on this neuropeptide can be developed to be highly selective. The work brings us one step closer to the development of practical neuropeptide-like substances that will be effective in controlling pest insects in an environmentally friendly fashion.

Technical Abstract: Corazonin is a peptidergic neurohormone of insects which is expressed in neurosecretory neurons of the pars lateralis of the protocerebrum and transported via nervi corpus cardiaci in the storage lobes of the corpora cardiaca. This peptide occurs with a single isofomr in all insects studied so far, only in Coleoptera a corazonin form could not be detected at all. Very few modifications of [Arg7]-corazonin, originally isolated from cockroaches, are known, namely [His7]-corazonin which is expressed in certain locusts and the stick insect Carausius morosis and [Thr4, His7]-corazonin recently described from the honey bee Apis mellifera. In this study, we performed a comprehensive screening for corazonin in the different insect groups which was initiated after the detection of a fourth isoform in a crane fly, Tipula sp. [Arg7]-corazonin is distributed in most major lineages of insects, and is thus the ancient form which is present at the time the insect orders evolved. The replacement of Arg with His at position 7 from the N-terminus occurred several times in the evolution of insects. The third isoform, [Thr4,His7]-corazonin, seems to be restricted to bees (Apidae); wasps (Vespidae) and even a bumble bee (Apidae) each express other corazonins, namely [His7]-corazonin and [Tyr3, Gln7, Gln10]-corazonin. A novel corazonin form, [His4, Gln7]-corazonin, was also detected in all South African members of the newly described insect order Mantophasmatodea. The [His4,Gln7]-corazonin separates these species from the Namibian Mantophasmatodea which express [Arg7]-corazonin and can be used as a distinct character to distinguish these morphologically very similar insects.