Calcofluor disrupts the midgut defense system in insects

The insect midgut is generally lined with a unique protective chitin/protei n structure, the peritrophic membrane (PM). We demonstrated that in Trichop lusia ni larvae, the majority of PM proteins were assembled with chitin as a consequence of their chitin binding properties. These proteins could be d issociated from the PM in vitro by Calcofluor, a well-known chemical with c hitin binding properties. The chitin binding characteristics of FM proteins were confirmed by their high affinity binding in vitro to regenerated chit in. In vivo assays demonstrated that Calcofluor could inhibit PM formation in five lepidopteran insects tested. The inhibition of T. ni PM formation b y Calcofluor, was accompanied by increased larval susceptibility to baculov irus infection. Continuous inhibition of PM formation by Calcofluor resulte d in retarded larval development and mortality. The destructive effect of C alcofluor on PM formation was demonstrated to be transient and reversible d epending on the presence of Calcofluor within the midgut. In addition, degr adation of the insect intestinal mucin was observed concurrently with the i nhibition of PM formation by Calcofluor. our studies revealed a potential n ovel approach to develop strategies for insect control by utilizing chitin binding molecules to specifically target PM formation in a broad range of i nsect pest species. (C) 2000 Elsevier Science Ltd. All rights reserved.