The Mode of Action of the Bacillus thuringiensis Vegetative Insecticidal Protein Vip3A Differs from That of Cry1Ab δ-Endotoxin

Abstract

The Vip3A protein, secreted by Bacillus spp. during the vegetative stage of growth, represents a new family of insecticidal proteins. In our investigation of the mode of action of Vip3A, the 88-kDa Vip3A full-length toxin (Vip3A-F) was proteolytically activated to an approximately 62-kDa core toxin either by trypsin (Vip3A-T) or lepidopteran gut juice extracts (Vip3A-G). Biotinylated Vip3A-G demonstrated competitive binding to lepidopteran midgut brush border membrane vesicles (BBMV). Furthermore, in ligand blotting experiments with BBMV from the tobacco hornworm, Manduca sexta (Linnaeus), activated Cry1Ab bound to 120-kDa aminopeptidase N (APN)-like and 250-kDa cadherin-like molecules, whereas Vip3A-G bound to 80-kDa and 100-kDa molecules which are distinct from the known Cry1Ab receptors. In addition, separate blotting experiments with Vip3A-G did not show binding to isolated Cry1A receptors, such as M. sexta APN protein, or a cadherin Cry1Ab ecto-binding domain. In voltage clamping assays with dissected midgut from the susceptible insect, M. sexta, Vip3A-G clearly formed pores, whereas Vip3A-F was incapable of pore formation. In the same assay, Vip3A-G was incapable of forming pores with larvae of the nonsusceptible insect, monarch butterfly, Danaus plexippus (Linnaeus). In planar lipid bilayers, both Vip3A-G and Vip3A-T formed stable ion channels in the absence of any receptors, supporting pore formation as an inherent property of Vip3A. Both Cry1Ab and Vip3A channels were voltage independent and highly cation selective; however, they differed considerably in their principal conductance state and cation specificity. The mode of action of Vip3A supports its use as a novel insecticidal agent.

Interação de proteínas Cry1 e Vip3A de Bacillus thuringiensis para controle de lepidópteros-praga

“…A massa molecular das pró-toxinas Cry está compreendida entre 130 e 135 kDa (Lightwood et al, 2000), enquanto a das pró-toxinas Vip3A é de 88,5 kDa (Loguercio et al, 2002 vip3Aa,vip3Ae,vip3Af,cry1Aa,cry1Ab,cry1Ac, cry1Ca e cry1Ea. MM, marcador de massa molecular (kDa).…”

“…As toxinas Vip3 atuam no controle de lepidópteros e, para se tornarem ativas, devem sofrer a clivagem de 199 aminoácidos na região N-terminal (Lee et al, 2003).…”

Vip3A is responsible for the potency of Bacillus thuringiensis 9816C culture supernatant against Helicoverpa armigera and Spodoptera exigua

“…It shows no homology with the Bt toxins or any other protein, whereas it possesses insecticidal activity against a wide spectrum of lepidopteran insects, especially those which are less sensitive to d-endotoxins (Donovan et al, 2001;Estruch et al, 1996;Lee et al, 2003;Loguercio et al, 2002;Selvapandiyan et al, 2001;Yu et al, 1997). To further investigate if Vip3A is responsible for the activity of Bt9816C supernatant, we must evaluate its potency.…”

Genetic diversity and susceptibility to Vip3Aa20 protein in Brazilian populations of <i>Helicoverpa armigera</i> and <i>Helicoverpa zea</i> (Lepidoptera: Noctuidae)

“…Vip3A protein has been an important tool for IRM programs, because there is no cross-resistance with Cry proteins (LEE et al, 2003).…”

“…These species were considered the major target pests of genetically modified maize expressing Bacillus thuringiensis (Berliner) (Bt) genes until the detection of Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) in 2013 (CZEPACK et al, 2013; proteins is different from the Cry proteins (SELVAPANDIYAN et al, 2001;LEE et al, 2003). Hence, there is no cross-resistance between these insecticidal proteins in insects (JACKSON et al, 2007;SENA;HERNANDEZ-RODRIGUEZ;FERRÃO, 2009;KURTZ, 2010;GULZAR et al, 2012).…”