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Distinct Impact of Processing on Cross-Order Cry1I Insecticidal Activity.
Dafne Toledo1,2, Yolanda Bel1,2, Stefanie Menezes de Moura3,4
1Institute of Biotechnology and Biomedicine, University of Valencia, 46100 Valencia, Spain.
Toxins
|February 25, 2025
Summary
Bacillus thuringiensis Cry1I insecticidal proteins show varying toxicity based on insect type. N-terminal cleavage impacts efficacy against lepidopteran pests but not coleopteran pests.
Area of Science:
- Biochemistry
- Entomology
- Molecular Biology
Background:
- Bacillus thuringiensis (Bt) Cry proteins are vital for biopesticides and transgenic crops.
- The Cry1I protein family exhibits unique characteristics, including vegetative production, protoxin dimerization, and dual toxicity against lepidopteran and coleopteran pests.
Purpose of the Study:
- To investigate the oligomerization and toxicity of Cry1Ia intermediate forms.
- To compare the insecticidal activity of different Cry1Ia processing stages against specific pests.
Main Methods:
- Heterologous expression of Cry1Ia intermediate forms.
- Trypsinization and larval gut fluid treatments to generate protein variants.
- Bioassays using Ostrinia nubilalis (European corn borer) and Leptinotarsa decemlineata (Colorado potato beetle) larvae.
Main Results:
- Cry1Ia intermediate forms oligomerized and retained toxicity against Ostrinia nubilalis.
- The fully processed Cry1Ia toxin was significantly less toxic to Ostrinia nubilalis compared to intermediate forms.
- No significant toxicity differences were observed among Cry1Ia forms against Leptinotarsa decemlineata.
Conclusions:
- Cry1I protein's mode of action varies between insect orders (lepidopteran vs. coleopteran).
- N-terminal cleavage critically affects Cry1I toxicity in lepidopteran pests, but not in coleopteran pests.
- Understanding these processing-dependent effects is crucial for optimizing Cry1I-based pest control strategies.
