From bioassays to Drosophila genetics: strategies for characterizing an essential insect neurohormone, bursicon.

We describe the molecular analysis and cellular expression of the insect peptide neurohormone, bursicon. Bursicon triggers the sclerotization of the soft insect cuticle after ecdysis. Using protein elution analyses from SDS gels, we determined the molecular weight of bursicon from different insects to be approximately 30 kDa. Four partial peptide sequences of Periplaneta americana bursicon were obtained from purified nerve cord homogenates separated on two-dimensional gels. Antibodies produced against one of the sequences identified the cellular location of bursicon in different insects and showed that bursicon is co-produced with crustacean cardioactive peptide (CCAP) in the same neurons in all insects tested so far. Additionally, using the partial peptide sequences, we successfully searched the Drosophila genome project for the gene encoding bursicon. With Drosophila as a tool, we can now verify the function of the sequence using transgenic flies. Sequence comparisons also allowed us to verify that bursicon is conserved, corroborating the older data from bioassays and immunohistochemical analyses. The sequence of bursicon will enable further analysis of its function, release, and evolution.