Toxicity and binding analyses of Bacillus thuringiensis toxin Vip3A in Cry1Ac-resistant and -susceptible strains of Helicoverpa armigera (Hübner)

Abstract

The Bacillus thuringiensis vegetative insecticidal protein, Vip3A, represents a new family of Bt toxin and is currently applied to commercial transgenic cotton. To determine whether the Cry1Ac-resistant Helicoverpa armigera would be cross-resistant to Vip3Aa protein, insecticidal activities, proteolytic activations and binding properties of Vip3Aa toxin were investigated using Cry1Ac-susceptible (96S) and Cry1Ac-resistant H. armigera strain (Cry1Ac-R). The toxicity of Vip3Aa in Cry1Ac-R slightly reduced compared with 96S, the resistance ratio was only 1.7-fold. The digestion rate of full-length Vip3Aa by gut juice extracts from 96S was little faster than that from Cry1Ac-R. Surface plasmon resonance (SPR) showed there was no significant difference between the binding affinity of Vip3Aa and BBMVs between 96S and Cry1Ac-R strain, and there was no significant competitive binding between Vip3Aa and Cry1Ac in susceptible or resistant strains. So there had little cross-resistance between Vip3Aa and Cry1Ac, the pyramid strategy, Vip3A+Cry proteins, maybe the suitable way to control H. armigera for China in the future.

The progress in insect cross‐resistance among Bacillus thuringiensis toxins

“…Studies also demonstrated that the colonies resistant to Cry1A proteins, Cry2Ab proteins ( T. ni and H. armigera ) or Dipel ( O. furnacalis , H. armigera , Plodia interpunctella, and T. ni ) had no cross‐resistance to Vip3 proteins (Gomis‐cebolla et al, ; P. Wang et al, ; Tables S3, S4). Several colonies of H. armigera with resistance to either Cry1Ac or Cry2Ab were also not cross‐resistance to Vip3Aa (An et al, ; Q. Zhang, Chen, Lu, Zhang, & Liang, ; Wei, Wu, Yang, & Wu, ; Table S3). Meanwhile, lack of cross‐resistance to Vip3A proteins was found in S. Frugiperda , which showed resistance to Cry1F or Cry2Ab2 in a series of studies (Bernardi et al, ; Vélez et al, ; Yang, Kerns, Head, & Brown, ; Yang, Kerns, Head, Price, & Huang, ).…”

Bacillus thuringiensis Vip3Aa Toxin Resistance in Heliothis virescens (Lepidoptera: Noctuidae)

“…A Cry1Ac-resistant H. zea population also demonstrated a lack of cross-resistance to Vip3Aa (25). A Cry1Ac-selected population of H. armigera showed 1.7-fold resistance to Vip3Aa (29). In another study, cross-resistance between Cry1Ac and Vip3Aa was low in Cry1Ac-Sel H. armigera (30).…”

Insecticidal Activity of 11 Bt toxins and 3 Transgenic Maize Events Expressing Vip3Aa19 to Black Cutworm, Agrotis ipsilon (Hufnagel)

“…Vip3A is well known for its wide spectrum of toxic activity to lepidopteran, especially Nuctuidae insect pests such as Helicoverpa armigera, Spodoptera frugiperda, Spodoptera exigua, but no toxic activity has been shown to Ostrinia nubilalis and Ostrinia furnacalis [21][22][23]. Vip3Aa has no structural similarity with Cry1 and Cry2 proteins and has a different mode of action [12,24,25]. Vip3Aa is therefore considered to be a good candidate co-expressed with Cry proteins in Bt crops for targeting a broad spectrum and delaying the evolution of insect resistance.…”