Enhancement of Bacillus thuringiensis toxicity to lepidopterous species with the enhancin from Trichoplusia ni granulovirus

The enhancin from the Trichoplusia ni (Hubner) granulovirus (TnGV) is a 104 -kDa viral protein that can significantly increase the virulence of several baculoviruses. Enhancin can destroy the structural integrity of the peritr ophic membrane (PM) of lepidopterous larvae, resulting in more efficient pe netration of the PM by virions and avoidance of inactivation by larval midg ut factors. In this study we demonstrate that TnGV enhancin can also enhanc e toxicity of Bacillus thuringiensis (Berliner) (Bt) to several noctuid spe cies. Addition of enhancin significantly increased the toxicity of Dipel, a commercial Pt formulation, to six species (T. ni, Helicoverpa tea (Boddie) , Heliothis virescens (Fabricius), Spodoptera exigua (Hubner), Pseudoplusia includens (Walker), and Anticarsia gemmatalis (Hubner)). Furthermore, the effectiveness of four commercial Pt-based products (Cutlass, Javelin, Biobi t, and Dipel) against T. ni was enhanced three- to sixfold by adding purifi ed enhancin. We hypothesize that the PM of larvae can impede the movement o f the BT toxin protein to the midgut brush border and that enhancin can inc rease the toxicity by affecting the permeability of the PM. (C) 2001 Academ ic Press.