A HYDROPHOBIC PEPTIDE (VAP-PEPTIDE) OF THE SILKWORM, BOMBYX-MORI - A UNIQUE ROLE FOR ADULT ACTIVITY PROPOSED FROM GENE-EXPRESSION AND PRODUCTION AT THE TERMINAL PHASE OF METAMORPHOSIS

A unique hydrophobic peptide (VAP-peptide) isolated from male adult he ads of the silkworm, Bombyx mori, has been shown to act as a synergist to the diapause hormone when administered exogenously. Here, we inves tigated the true roles of the endogenous VAP-peptide on differentiatio n and development of adult organs in the silkworm. By northern blot an alyses, the VAP-peptide gene was shown to be exclusively expressed at the terminal phase of adult development in epithelial tissues, especia lly in the wing and the thoracic integument. In situ hybridization ana lysis revealed that the gene was highly expressed in the epidermal cel ls of the wing vein and the thoracic integument. The stage- and tissue -dependent gene expression were clearly correlated to the accumulation profile of VAP-peptide. In the adult thoracic integument, VAP-peptide was predominantly deposited in the cuticle layer. Affinity chromatogr aphy indicated the ability of VAP-peptide to bind to chitin. Based on its expression patterns, localization, and chemical properties, VAP-pe ptide is conceived to be a structural protein that participates in mec hanical strengthening of specific cuticle structures, supporting their physical requirements in the adult life of the silkworm. (C) 1998 Els evier Science Ltd. All rights reserved.