title: Unlinked genetic loci control the reduced transcription of aminopeptidase N 1 and 3 in the European corn borer and determine tolerance to Bacillus thuringiensis Cry1Ab toxin.
abstract: Transgenic expression of Bacillus thuringiensis (Bt) crystalline (Cry) toxins by crop plants result in reduced insect feeding damage, but sustainability is threatened by the development of resistance traits in target insect populations. We investigated Bt toxin resistance trait in a laboratory colony of the European corn borer, Ostrinia nubilalis, selected for increased survival when exposed to Cry1Ab and correlated survival on Cry1Ab toxin with a constitutive ∼146.2 ± 17.3-fold reduction in midgut aminopeptidase N1 (apn1) transcript levels. A 7.1 ± 1.9-fold reduction apn3 transcript level was also correlated with Cry1Ab resistance. Quantitative trait locus (QTL) mapping identified a single major genome region controlling Cry1Ab resistance on linkage group 24 (LG24), and a minor QTL on LG27. Both QTL were independent of apn1 and apn3 loci on LG02. Positional mapping identified genetic markers that may assist in the identification of causal gene(s) within QTL intervals. This study indicates that genetic factor(s) may act in trans to reduce both apn1 and apn3 expression in Cry1Ab resistant O. nubilalis larvae, and suggest that gene regulatory pathways can influence Bt resistance traits. These findings show that gene interactions (epistasis) may influence Bt resistance in target insect populations.
authors.affiliation: USDA-ARS, Corn Insect and Crop Genetics Research Unit, Genetics Laboratory, Iowa State University, Ames, IA 50011, USA; Department of Entomology, Iowa State University, Ames, IA 50011, USA. Electronic address: brad.coates@ars.usda.gov.
authors.forename: Brad S
authors.initials: BS
authors.lastname: Coates
authors.forename: Douglas V
authors.initials: DV
authors.lastname: Sumerford
authors.forename: Blair D
authors.initials: BD
authors.lastname: Siegfried
authors.forename: Richard L
authors.initials: RL
authors.lastname: Hellmich
authors.forename: Craig A
authors.initials: CA
authors.lastname: Abel
mesh_terms: D000818:Animals; D001413:Bacillus thuringiensis / Q000472:pathogenicity; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins / Q000235:genetics / Q000493:pharmacokinetics; D018826:CD13 Antigens / Q000096:biosynthesis* / Q000235:genetics; D004731:Endotoxins / Q000235:genetics / Q000493:pharmacokinetics; D008040:Genetic Linkage; D006460:Hemolysin Proteins / Q000235:genetics / Q000493:pharmacokinetics; D007305:Insecticide Resistance / Q000187:drug effects / Q000235:genetics*; D007306:Insecticides / Q000494:pharmacology; D007915:Lepidoptera / Q000201:enzymology; D010572:Pest Control, Biological; D030821:Plants, Genetically Modified; D040641:Quantitative Trait Loci / Q000235:genetics*; D014158:Transcription, Genetic
chemical_list: D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D004731:Endotoxins; D006460:Hemolysin Proteins; D007306:Insecticides; C030956:insecticidal crystal protein, Bacillus Thuringiensis; D018826:CD13 Antigens
keywords: Crystalline (cry) toxin resistance; Gene network; Gene regulation