Molecular Cloning, Genomic Organization, and Expression of a B-Type (Cricket-Type) Allatostatin Preprohormone from Drosophila melanogaster

Abstract

The insect allatostatins obtained their names because they block the biosynthesis of juvenile hormone (a terpenoid) in the corpora allata (two endocrine organs near the insect brain). Chemically, the allatostatins can be subdivided into three different peptide groups: the A-type allatostatins, first discovered in cockroaches, which have the C-terminal sequence Y/FXFGLamide in common; the B-type allatostatins, first discovered in crickets, which all have the C-terminal sequence W(X)6Wamide; and the C-type allatostatins, first discovered in the moth Manduca sexta, which have an unrelated and nonamidated C terminus. We have previously reported the structure of an A-type allatostatin preprohormone from the fruitfly Drosophila melanogaster. Here we describe the molecular cloning of a B-type prepro-allatostatin from Drosophila (DAP-B). DAP-B is 211 amino acid residues long and contains one copy each of the following putative allatostatins: AWQSLQSSWamide (drostatin-B1), AWKSMNVAWamide (drostatin-B2), <EAQGWNKFRGAWamide (drostatin-B3), EPTWNNLKGMWamide (drostatin-B4), and DQWQKLHGGWamide (drostatin-B5). All five drostatins are novel peptide structures. The DAP-B gene has one intron and two exons and is located at position 74B1 on the left arm of the third chromosome. The gene is expressed in all developmental stages, but weakly in embryos and strongly in larvae. In situ hybridizations of larvae showed that neurons in the brain and abdominal ganglia and endocrine cells in the gut expressed DAP-B. This is the first published report of a B-type allatostatin preprohormone in insects, and the first paper describing the presence of B-type allatostatins in a representative of the insect order Diptera (flies).