Identification and molecular detection of a deletion mutation responsible for a truncated cadherin of Helicoverpa armigera

Cadherins are a class of receptor proteins for Bacillus thuringiensis Cry1A toxins. Disruption of a cadherin gene (Ha_BtR) is associated with Cry1Ac resistance in the cotton bollworm Helicoverpa armigera [Xu, X., Yu, L., Wu, Y., 2005. Disruption of a cadherin gene associated with resistance to Cry1Ac δ-endotoxin of B. thuringiensis in H. armigera. Appl. Environ. Microbiol. 71, 948–954]. Determination of the genomic DNA sequences of Ha_BtR gene showed that the wild type Ha_BtR coding sequence is comprised of 34 exons. A deletion between Exon 8 and Exon 25 was found to be responsible for a truncated cadherin in the Cry1Ac-resistant GYBT strain of H. armigera. The mutant allele of Ha_BtR (r1) has two possible transcription variants, both of which produce the same truncated protein. A DNA-based detection method specific to the r1 allele was developed. This study will facilitate the monitoring of cadherin mutant frequency in field populations of H. armigera.