Mode of action of Bt 3d-Cry toxins and use of genetically modified toxins to counter pest resistance

2016 ◽  
Author(s):  
Mario Soberón
Keyword(s):  
Mode Of Action ◽  
Genetically Modified ◽  
Pest Resistance ◽  
Cry Toxins

scholarly journals Genetically Modified Potato for Pest Resistance: Thrift or Threat?

2021 ◽  
Author(s):  
Martin Raspor ◽  
Aleksandar Cingel
Keyword(s):  
Insect Pests ◽  
Genetically Modified ◽  
New Technology ◽  
Single Gene ◽  
Genetically Modified Crops ◽  
Pest Resistance ◽  
Potato Production ◽  
Bt Toxin ◽  
Long Term Impact ◽  
The Cost

Significant limitations in potato production are crop loss due to the damage made by insect pests, and the cost of enormous amount of chemicals, harmful to humans and environment, extensively used in their control. As an alternative, development of genetically modified potato offered possibility for pest management in a more sustainable, environmentally friendly way. Over the past 30 years introduction of pest resistance traits progressed from a single gene to multiple stacked events and from Bt-toxin expression to expression of proteins from non-Bt sources, dsRNA and their combination, while advances in molecular biology have brought “cleaner” gene manipulation technologies. However, together with benefits any new technology also bears its risks, and there are still a range of unanswered questions and concerns about long-term impact of genetically modified crops – that with knowledge and precautionary approaches can be avoided or mitigated. Sustainability of genetically modified crops for pest control largely depends on the willingness to gain and implement such knowledge.

scholarly journals Specific Binding of Bacillus thuringiensis Cry2A Insecticidal Proteins to a Common Site in the Midgut of Helicoverpa Species

2008 ◽  
Vol 74 (24) ◽  
pp. 7654-7659 ◽  
Author(s):  
Carmen Sara Hernández-Rodríguez ◽  
Adri Van Vliet ◽  
Nadine Bautsoens ◽  
Jeroen Van Rie ◽  
Juan Ferré
Keyword(s):  
Binding Sites ◽  
Mode Of Action ◽  
Helicoverpa Zea ◽  
Tertiary Structure ◽  
Specific Binding ◽  
Membrane Vesicles ◽  
Binding Assays ◽  
Cry Toxins ◽  
Long Time ◽  
Competition Assays

ABSTRACT For a long time, it has been assumed that the mode of action of Cry2A toxins was unique and different from that of other three-domain Cry toxins due to their apparent nonspecific and unsaturable binding to an unlimited number of receptors. However, based on the homology of the tertiary structure among three-domain Cry toxins, similar modes of action for all of them are expected. To confirm this hypothesis, binding assays were carried out with 125I-labeled Cry2Ab. Saturation assays showed that Cry2Ab binds in a specific and saturable manner to brush border membrane vesicles (BBMVs) of Helicoverpa armigera. Homologous-competition assays with 125I-Cry2Ab demonstrated that this toxin binds with high affinity to binding sites in H. armigera and Helicoverpa zea midgut. Heterologous-competition assays showed a common binding site for three toxins belonging to the Cry2A family (Cry2Aa, Cry2Ab, and Cry2Ae), which is not shared by Cry1Ac. Estimation of K d (dissociation constant) values revealed that Cry2Ab had around 35-fold less affinity than Cry1Ac for BBMV binding sites in both insect species. Only minor differences were found regarding R t (concentration of binding sites) values. This study questions previous interpretations from other authors performing binding assays with Cry2A toxins and establishes the basis for the mode of action of Cry2A toxins.

scholarly journals Impact of Antibiotics on Efficacy of Cry Toxins Produced in Two Different Genetically Modified Bt Maize Varieties in Two Lepidopteran Herbivore Species, Ostrinia nubilalis and Spodoptera littoralis

Toxins ◽  
2018 ◽  
Vol 10 (12) ◽  
pp. 489 ◽  
Author(s):  
Angelika Hilbeck ◽  
Nicolas Defarge ◽  
Thomas Bøhn ◽  
Michelle Krautter ◽  
Constanze Conradin ◽  
...  
Keyword(s):  
Ostrinia Nubilalis ◽  
Spodoptera Littoralis ◽  
European Corn Borer ◽  
Genetically Modified ◽  
Gut Bacteria ◽  
Bt Maize ◽  
Cry Toxins ◽  
Gm Plants ◽  
Bt Toxins ◽  
Maize Varieties

The insecticidal crystal proteins from Bacillus thuringiensis (Bt) are widely-used biopesticides that are used both as Bt spore-crystal preparations in sprayable formulations and as activated toxins in genetically modified (GM) plants. Models for their modes of action have been proposed but many issues remain unresolved. Among those is the role of commensal gut bacteria in target insect death: previous studies showed that antibiotics attenuate the toxicity of Bt sprays. We tested whether antibiotics interfere with the effects of GM plant-produced Bt toxins in larvae of two Lepidopteran species, the European corn borer Ostrinia nubilalis and the cotton leafworm Spodoptera littoralis. The larvae were reared on artificial diet with or without antibiotics and, thereafter, fed two varieties of Bt GM maize in comparison to conventional non-Bt maize leaves sprayed with antibiotic solution and/or with a Bt formulation. Antibiotics significantly reduced or delayed the toxicity of Cry toxins, although to a lesser extent than previously reported for Bt-sprays. This supports the hypothesis that Cry toxins induce mortality by themselves in the absence of Bt bacteria and spores, and of commensal gut bacteria. However, larvae that were not treated with antibiotics died faster and at a higher rate which was further compounded by plant variety and species sensitivity. These findings support a hypothesis that toxicemia alone can inflict significant mortality. However, in the absence of antibiotics, the gut bacteria likely enhance the Cry toxin effect by inflicting, additionally, bacterial septicemia. This has important implications in field situations where antibiotic substances are present—e.g., from manure of animals from conventional production systems—and for ecotoxicological testing schemes of Bt toxins and nontarget organisms that are often using artificial diets enriched with high concentrations of antibiotics.

scholarly journals Employing phage display to study the mode of action of Bacillus thuringiensis Cry toxins

Peptides ◽  
2008 ◽  
Vol 29 (2) ◽  
pp. 324-329 ◽  
Author(s):  
Luisa Elena Fernández ◽  
Isabel Gómez ◽  
Sabino Pacheco ◽  
Iván Arenas ◽  
Sarjeet S. Gilla ◽  
...  
Keyword(s):  
Bacillus Thuringiensis ◽  
Phage Display ◽  
Mode Of Action ◽  
Cry Toxins

scholarly journals Key Residues of Bacillus Thuringiensis Cry2Ab for Oligomerization and Pore-Formation Activity

2021 ◽  
Author(s):  
Zhi-Zhen Pan ◽  
Lian Xu ◽  
Bo Liu ◽  
Qing-Xi Chen ◽  
Yu-Jing Zhu
Keyword(s):  
Bacillus Thuringiensis ◽  
Insecticidal Activity ◽  
Mode Of Action ◽  
Pore Formation ◽  
Wild Type ◽  
Cry Toxins ◽  
Key Residues ◽  
Domain I ◽  
First Time

Abstract As a pore-forming toxin, oligomerization and pore-formation were both required for the mode of action of Cry toxins. Previous studies revealed that Domain I helices α4-α5 were involved in oligomerization of Cry2Ab, while the active residues in charge of Cry2Ab aggregation remained ambiguous. In present studies, we built 20 Cry2Ab alanine mutants site directed in helices α4-α5 and demonstrated that mutants N151A, T152A, F157A, L183A, L185A and I188A blocked the assembly of 250 kDa oligomers, suggesting that those residues were key residues for Cry2Ab oligomerization. As expected, those variants severely reduced the insecticidal activity against P. xylostella which was similar to our previous reports. Furthermore, we found that the pore-forming activities of non-oligomerization mutants sharply decreased compared to wild-type Cry2Ab. Taken together, our data comprehensively identified key residues for Cry2Ab for the first time and emphasized that oligomerization was closely related to insecticidal activity and pore-forming activity in Cry2Ab.

Countering pest resistance with genetically modified Bt toxins.

2015 ◽  
pp. 150-161
Author(s):  
M. Soberón ◽  
B. I. García-Gómez ◽  
S. Pacheco ◽  
J. Sánchez ◽  
B. E. Tabashnik ◽  
...  
Keyword(s):  
Genetically Modified ◽  
Pest Resistance ◽  
Bt Toxins

scholarly journals Persistence of Cry toxins and cry genes from genetically modified plants in two agricultural soils

2007 ◽  
Vol 27 (3) ◽  
pp. 231-236 ◽  
Author(s):  
Elisa Marchetti ◽  
Cesare Accinelli ◽  
Valentina Talamè ◽  
Rosanna Epifani
Keyword(s):  
Agricultural Soils ◽  
Genetically Modified ◽  
Genetically Modified Plants ◽  
Cry Genes ◽  
Cry Toxins
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