IDENTIFICATION, SEQUENCE AND MESSENGER-RNA EXPRESSION PATTERN DURING METAMORPHOSIS OF A CDNA-ENCODING A GLYCINE-RICH CUTICULAR PROTEIN IN TENEBRIO-MOLITOR

The study of insect cuticular proteins and their sequences is of inter est because they are involved in protein-protein and protein-chitin in teractions which confer the mechanical properties and fine architectur e of the cuticle. Moreover, in the coleopteran Tenebrio molitor there is a dramatic change in cuticular architecture between pre- and postec dysial secretion. We report the isolation, by differential screening, and the sequence characterization of a cDNA clone encoding a cuticular protein of T. molitor, ACP17. After insertion in the expression vecto r pEX1, the recognition of the fusion protein by an anti-cuticular mon oclonal antibody confirmed the cuticular nature of ACP17. Northern hyb ridization analysis showed that ACP17 mRNA expression begins weakly 3 days before adult ecdysis and strongly increases during the secretion of postecdysial adult cuticle, with a maximum just after ecdysis. In s itu hybridization revealed that the ACP17 mRNA is only present in the epidermis which secretes hard cuticle. The deduced amino acid (aa) com position exhibits a high content of Gly (28%) and Ala (20%) and, parti cularly, two poly(Gx) stretches separated by repetitive motifs with pr oline AAPVA, A comparison is made with other cuticle aa sequences.