Collaborative Research: The Molecular Identification and Action of Bursicon, the Insect Cuticle Sclerotizing Hormone

Vanderbilt University, Nashville TN

Investigators

Abstract

An insect hormone called bursicon is essential for hardening of the new skin (cuticle) after the insect has shed its old one during molting (ecdysis). The timed release and actions of bursicon are critically important for the survival of all insects and, most likely, all arthropods. Although bursicon was discovered in 1935 and is known to be a peptide, its molecular structure has not been established, and remains a major unsolved problem in insect neuroendocrinology. The Honegger lab has purified the hormone and obtained partial amino acid sequences for bursicon from some insects. Recently they were able to use these sequences to identify a particular gene sequence, CG13419, in the genome of the fruitfly Drosophila. The primary aim of this collaborative project is to determine whether the CG13419 gene product is the functional bursicon hormone, as an important step to understanding the actions of bursicon. Molecular techniques for gene expression in eukaryotic cells and overexpression in Drosophila will be combined with the 'ligated fly' bioassay using the related blowfly (Sarcophaga) to test for bursicon activity. If bioactive bursicon is shown, the sequence will be used for cDNA screening in the moth Manduca, a well-studied insect system in which the complex hormonal interactions regulating ecdysis have been illuminated. From the recombinant proteins and synthesized peptides from conserved sequence stretches, new antibodies will be produced to identify neurosecretory cells in the brain, and to clarify the temporal and spatial activation of bursicon release in Manduca. Results from this work will provide a potential breakthrough for understanding how the brain and endocrine systems together orchestrate multiple biochemical events leading to periodic cuticular hardening. Knowledge about this key hormone may provide novel strategies for agriculture in developing insect pest controls, and in managing crustacean aquaculture. In addition, this collaboration between two institutions includes multi-disciplinary postdoctoral training.