Temporal synthesis of cuticle proteins during larval development in the tsetse fly, glossina morsitans morsitans

Abstract

The tsetse fly is an insect of great economic importance to man as a vector of both human and animal trypanosomiasis. The important functions of the cuticle are support, including muscle attachment, protection, and permeability barriers. Cuticle proteins are an important component, that define much of specialized structural and functional nature of the cuticle. A thorough knowledge of the patterns of cuticle proteins during larval development in G. m.morsitans is important in understanding their possible roles in cuticular sclerotization. Such knowledge might be useful in management of tsetse flies. In this study proteins extracted from larval, pupal and adult cuticles of the tsetse fly, Glossina morsitans morsitans were compared electrophoretically by both SDS polyacrylamide gel electrophoresis and two-dimensional gel electrophoresis. Proteins extracted from the third instar resolved into ten major bands (Mr 10 KD, 12 KD, 14 KD, 26 KD, 28 KD, as KD, 45 KD, 70 KD, 93 KD, 112 KD, 200 KD). In SDS-PAGE, two major proteins (45 KD and 200 KD) were common to all stages of development. The 45 KD had a carbohydrate moiety

as it stained with Periodic acid schiff reagent (PAS). Cuticles from three larval instars (first, second and third) contained six low molecular weight proteins (10 KD, 12 KD, 14 KD, 30 KD, 50 KD, 80 KD). Two proteins emerging in pupal cuticle (29 KD and 98 KD) persisted upto the adult stages. Further analysis by two-dimensional gel electrophoresis and silver staining showed that few cuticular proteins were synthesized between the 18t and z- instars. By third instar (2 days before larviposition), a large number of proteins were induced (M, < 30 KD). These proteins persisted upto the brown pupal stage and showed a rapid decline thereafter. Most of the proteins with molecular weights Mr < 30 KD were undetectable at apolysis (5 days after larviposition). By 15 days pupal stage, the number of cuticle proteins was very small. Ligation of adults at eclosion resulted in notable changes of cuticle proteins.