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RNA Interference of Cadherin Gene Expression in Spodoptera exigua by Oral Ingestion of dsRNASeCad1
Cadherin gene, which is a receptor of the Bacillus thuringiensis toxins, was predicted from 454 pyrosequencing transcripts from fifth instar larvae of the beet armyworm, Spodoptera exigua. The S. exigua cadherin gene (SeCad1) encodes 9 cadherin repeats and a tranmembrane domain. The SeCad1 gene was expressed in all developmental stage specifically in gut tissue by RT-PCR analysis. Expression of SeCad1 gene was suppressed by both injection and feeding of its specific dsRNASeCad1 in 5th instar larval stage. The suppression of SeCad1 expression did not significantly influence on pupal and adult development of S. exigua. However, the larval treated with dsRNASeCad1 (100 ng/larva) significantly reduced susceptibility to B. thuringiensis ssp. aizawai (3 × 106 CFU/larva). By contrast, the dsRNASeCad1-treated larvae did not show any change in susceptibility to B. thuringiensis ssp. krustaki (4 × 107 CFU/larva). These results suggest that SeCad1 is a specific receptor of Cry1A toxin from B. thuringiensis in S. exigua, but not Cry1C toxin.
