Domain III of Cry1Ac Is Critical to Binding and Toxicity against Soybean Looper (Chrysodeixis includens) but Not to Velvetbean Caterpillar (Anticarsia gemmatalis)

Insecticidal proteins Cry1Ac and Cry2Ac7 from the bacterium (Bt) belong to the three-domain family of Bt toxins. Commercial transgenic soybean hybrids produce Cry1Ac to control the larvae of the soybean looper ( ) and the velvet bean caterpillar ( ). The specificity of Cry1Ac is determined by loops...

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Bibliographic Details
Published in:Toxins 2018-02, Vol.10 (3), p.95
Main Authors: Mushtaq, Rubina, Shakoori, Abdul Rauf, Jurat-Fuentes, Juan Luis
Format: Article
Language:English
Subjects:
Animals
Anticarsia gemmatalis
Bacillus thuringiensis
Bacterial Proteins - chemistry
Bacterial Proteins - genetics
Bacterial Proteins - toxicity
Binding sites
Binding, Competitive
Bioassays
Biological Assay
Chrysodeixis
Chrysodeixis includens
Cry1Ac
Cry1Ac toxin
Endotoxins - chemistry
Endotoxins - genetics
Endotoxins - toxicity
Glycine max
Hemolysin Proteins - chemistry
Hemolysin Proteins - genetics
Hemolysin Proteins - toxicity
Hybrids
Larva - drug effects
Larvae
Lepidoptera - drug effects
Membrane vesicles
Midgut
Pests
Protein Domains
Proteins
Soybeans
Toxicity
toxin domain
Toxins
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Summary:Insecticidal proteins Cry1Ac and Cry2Ac7 from the bacterium (Bt) belong to the three-domain family of Bt toxins. Commercial transgenic soybean hybrids produce Cry1Ac to control the larvae of the soybean looper ( ) and the velvet bean caterpillar ( ). The specificity of Cry1Ac is determined by loops extending from domain II and regions of domain III in the three-dimensional structure of the toxin. In this study, we constructed a hybrid toxin (H1.2Ac) containing domains I and II of Cry1Ac and domain III of Cry2Ac7, in an attempt to obtain a protein with enhanced toxicity compared to parental toxins. Bioassays with H1.2Ac revealed toxicity against the larvae of but not against . Saturation binding assays with radiolabeled toxins and midgut brush border membrane vesicles demonstrated no specific H1.2Ac binding to , while binding in was specific and saturable. Results from competition binding assays supported the finding that Cry1Ac specificity against is mainly dictated by domain II. Taken together, these distinct interactions with binding sites may help explain the differential susceptibility to Cry1Ac in and , and guide the design of improved toxins against soybean pests.
ISSN:2072-6651
2072-6651
DOI:10.3390/toxins10030095