Chitin synthesis in Spodoptera frugiperda wing imaginal discs. III: Role of the peripodial membrane

Abstract

AbstractWe determined the contribution of the peripodial membrane to chitin synthesis in cultured wing imaginal discs of Spodoptera frugiperda. This was accomplished by examining chitin synthesis in vitro in intact imaginal discs, in the peripodial membrane, and in imaginal discs in which the peripodial membrane had been injured. Chitin synthesis in peripodial membrane‐deprived imaginal discs, peripodial membrane injured imaginal discs, and peripodial membrane fragments was assessed by measuring incorporation of [14C]GlcNAc after treatment with 20‐hydroxyecdysone in tissue culture. Removing or injuring the peripodial membrane resulted in a marked decrease in ecdysteroid‐dependent chitin synthesis in these wing discs compared with intact wing discs. In addition, a break in the ecdysteroid treatment of 4 h reduced chitin synthesis in the wing discs substantially. These biochemical experiments were supplemented with ultrastructural and immunocytochemical approaches. A wheat germ agglutinin colloidal gold complex was used to visualize the presence of chitin synthesized by wing discs including the peripodial membrane. These experiments confirmed the importance of an intact peripodial membrane for optimal production of cuticle by the wing pouch. Our results demonstrate that for opti‐ma1 production of chitin in tissue culture, wing discs must be treated with 20‐hydroxyecdysone for an uninterrupted period of 48 h, and the peripodial membrane of these imaginal discs must be present and uninjured. © 1995 Wiley‐Liss, Inc.This article is a US Government work and, as such, is in the public domain in the United States of America.