Observations on the Presence of the Peritrophic Membrane in LarvalTrichoplusia niand Its Role in Limiting Baculovirus Infection

Abstract

Light microscopical examinations of dissected and stained peritrophic membranes (PMs) were conducted to determine the presence or absence of this protective structure in larvae ofTrichoplusia ni, prior to and through ecdysis. Observations of fourth- and fifth-instar larvae ofT. nifrom two independent rearing colonies showed that PMs were present and lined the midgut prior to, during, and immediately after ecdysis in both instars. Western blot analysis of insect intestinal mucin (IIM), a major protective protein in theT. niPM, indicated that synthesis of IIM occurred duringT. niembryonic development, or more precisely, that IIM synthesis started approximately 4 h prior to hatching. These results demonstrated that the neonateT. nimidgut is lined with a protective mucinous layer at hatching. A baculovirus enhancin fromT. nigranulosis virus (TnGV) enhancedper osviral infections of budded viruses (BVs) ofAutographa californicamultiple nuclear polyhedrosis virus (AcMNPV) andT. nisingle nuclear polyhedrosis virus (TnSNPV) in neonate, fourth-, and fifth-instar larvae ofT. ni.These results provided further evidence that the PM may serve as a partial barrier to viruses in the midgut lumen and that enhancins can facilitate the infection process. © 1998 Academic Press.