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RNA interference of cadherin gene expression in Spodoptera exigua reveals its significance as a specific Bt target
1Department of Bioresource Sciences, Andong National University, Andong 760-749, Republic of Korea.
Abstract:
Cadherin is a calcium-dependent cell surface molecule and has been proposed to be a target molecule of Bacillus thuringiensis Cry proteins. Based on a partial cadherin gene obtained from 454 pyrosequencing transcripts of the fifth instar Spodoptera exigua midgut, a full open reading frame of cadherin gene (SeCad1) was cloned. Its predicted amino acid sequence encodes extracellular 9 cadherin repeats, a transmembrane, and intracellular domain. SeCad1 gene was expressed in all developmental stages specifically in gut tissue by RT-PCR analysis. Expression of SeCad1 gene was suppressed by both injection and feeding of its specific double-stranded RNA (dsRNA(SeCad1)) in the fifth instar. The suppression of SeCad1 expression did not significantly influence on pupal and adult developments of S. exigua. However, the larvae treated with dsRNA(SeCad1) (100 ng/larva) significantly reduced susceptibility to B. thuringiensis ssp. aizawai. In contrast, the dsRNA(SeCad1)-treated larvae did not show any change in susceptibility to B. thuringiensis ssp. kurstaki. These results suggest that SeCad1 is a specific target molecule to Cry1C toxin from B. thuringiensis in S. exigua, but not to Cry1A toxin.
Insights
The study identified the Spodoptera exigua cadherin 1 (SeCad1) gene as a specific target for Bacillus thuringiensis Cry1C toxin. Suppressing SeCad1 reduced larval susceptibility to B. thuringiensis ssp. aizawai, but not B. thuringiensis ssp. kurstaki.
Area of Science:
- Insect molecular biology
- Pest management
- Biotechnology
Background:
- Bacillus thuringiensis (Bt) Cry proteins are insecticidal toxins used in agriculture.
- Cadherins are cell surface proteins implicated as potential targets for Bt Cry toxins.
- Understanding specific toxin-receptor interactions is crucial for developing effective pest control strategies.
Purpose of the Study:
- To clone and characterize the cadherin gene (SeCad1) from Spodoptera exigua midgut.
- To investigate the role of SeCad1 as a target molecule for Bacillus thuringiensis Cry proteins.
- To evaluate the impact of SeCad1 suppression on larval susceptibility to different Bt strains.
Main Methods:
- Cloning of the full open reading frame of the SeCad1 gene from S. exigua.
- Gene expression analysis using RT-PCR across different developmental stages.
- RNA interference (RNAi) using double-stranded RNA (dsRNA(SeCad1)) to suppress SeCad1 expression.
- Assessing larval susceptibility to B. thuringiensis ssp. aizawai and B. thuringiensis ssp. kurstaki following dsRNA treatment.
Main Results:
- The SeCad1 gene encodes a full-length cadherin protein with characteristic domains.
- SeCad1 expression was confirmed in S. exigua gut tissue across all developmental stages.
- Suppression of SeCad1 via dsRNA(SeCad1) significantly reduced larval susceptibility to B. thuringiensis ssp. aizawai (Cry1C toxin).
- No significant change in susceptibility was observed against B. thuringiensis ssp. kurstaki (Cry1A toxin).
Conclusions:
- SeCad1 is identified as a specific target molecule for Bacillus thuringiensis Cry1C toxin in Spodoptera exigua.
- The findings highlight the specificity of Bt toxin-receptor interactions.
- This research provides insights for targeted pest control strategies using Bt toxins.
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