IP Digestion

Molecular structure of the peritrophic membrane and its implication for insect control

Chitin/protein structures perform important protective functions in microorganisms and invertebrate animals. The peritrophic membrane (PM) is such a protective chitin/protein structure in the midgut of most insects, lining the intestinal tract and performing multiple functions in food digestion and in defense against pathogens and toxic compounds. Proteins are major PM constituents and play essential roles in PM formation and for PM protective functions. We used Trichoplusia ni as a model lepidopteran insect to study the PM structure and functions. Our results from biochemical and molecular analyses revealed that the PM proteins (=peritrophins) are predominantly composed of two types: insect intestinal mucin (IIM) and chitin binding proteins. The characteristics of IIM which is present as a major protein in T. ni PM demonstrated that the insect PM is virtually an intestinal mucus layer reinforced by chitin and revealed a midgut defense mechanism. In addition to the IIM, most of the PM proteins are chitin binding proteins in nature, playing essential roles in PM formation. Our understanding on the biochemical and molecular characteristics PM proteins provided a basis for us to model the PM structure and its formation. Key features of the PM proteins include extensive O-glycosylation of the IIM for their protease resistant nature, susceptibility of IIM to proteolytic degradation by baculovirus enhancins, necessity of disulfide bonding in IIM for its stability, and unique multiple chitin binding domain structures which serve as the major driving force for PM formation and stability. Understanding of these PM features has suggested new approaches to design strategies to disrupt the PM structure. Those strategies can be demonstrated in vitro or in vivo assaying systems and may be further developed towards novel strategies for insect control.

Index terms: Trichoplusia ni, midgut, chitin/protein structure

Copyright: The copyrights of this abstract belong to the author (see right-most box of title table). This document also appears in Session 13 – INSECT PHISIOLOGY, NEUROSCIENCES, IMMUNITY AND CELL BIOLOGY Symposium and Poster Session, ABSTRACT BOOK II – XXI-International Congress of Entomology, Brazil, August 20-26, 2000.