Identification of a Novel Aminopeptidase P-Like Gene OnAPP Possibly Involved in Bt Toxicity and Resistance in a Major Corn Pest Ostrinia nubilalisReport as inadecuate




Identification of a Novel Aminopeptidase P-Like Gene OnAPP Possibly Involved in Bt Toxicity and Resistance in a Major Corn Pest Ostrinia nubilalis - Download this document for free, or read online. Document in PDF available to download.

Studies to understand the Bacillus thuringiensis Bt resistance mechanism in European corn borer ECB, Ostrinia nubilalis suggest that resistance may be due to changes in the midgut-specific Bt toxin receptor. In this study, we identified 10 aminopeptidase-like genes, which have previously been identified as putative Bt toxin receptors in other insects and examined their expression in relation to Cry1Ab toxicity and resistance. Expression analysis for the 10 aminopeptidase-like genes revealed that most of these genes were expressed predominantly in the larval midgut, but there was no difference in the expression of these genes in Cry1Ab resistant and susceptible strains. This suggested that altered expression of these genes was unlikely to be responsible for resistance in these ECB strains. However, we found that there were changes in two amino acid residues of the aminopeptidase-P like gene OnAPP involving Glu305 to Lys305 and Arg307 to Leu307 in the two Cry1Ab-resistant strains as compared with three Cry1Ab-susceptible strains. The mature OnAPP contains 682 amino acid residues and has a putative signal peptide at the N-terminus, a predicted glycosylphosphatidyl-inositol GPI-anchor signal at the C-terminal, three predicted N-glycosylation sites at residues N178, N278 and N417, and an O-glycosylation site at residue T653. We used a feeding based-RNA interference assay to examine the role of the OnAPP gene in Cry1Ab toxicity and resistance. Bioassays of Cry1Ab in larvae fed diet containing OnAPP dsRNA resulted in a 38% reduction in the transcript level of OnAPP and a 25% reduction in the susceptibility to Cry1Ab as compared with larvae fed GFP dsRNA or water. These results strongly suggest that the OnAPP gene could be involved in binding the Cry1Ab toxin in the ECB larval midgut and that mutations in this gene may be associated with Bt resistance in these two ECB strains.



Author: Chitvan Khajuria, Lawrent L. Buschman, Ming-Shun Chen, Blair D. Siegfried, Kun Yan Zhu

Source: http://plos.srce.hr/



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