title: An independent occurrence of the chimeric P450 enzyme CYP337B3 of Helicoverpa armigera confers cypermethrin resistance in Pakistan.
abstract: The increasing resistance level of insect pest species is a major concern to agriculture worldwide. The cotton bollworm, Helicoverpa armigera, is one of the most important pest species due to being highly polyphagous, geographically widespread, and resistant towards many chemical classes of insecticides. We previously described the mechanism of fenvalerate resistance in Australian populations conferred by the chimeric cytochrome P450 monooxygenase CYP337B3, which arose by unequal crossing-over between CYP337B1 and CYP337B2. Here, we show that this mechanism is also present in the cypermethrin-resistant FSD strain from Pakistan. The Pakistani and the Australian CYP337B3 alleles differ by 18 synonymous and three nonsynonymous SNPs and additionally in the length and sequence of the intron. Nevertheless, the activity of both CYP337B3 proteins is comparable. We demonstrate that CYP337B3 is capable of metabolizing cypermethrin (trans- and especially cis-isomers) to the main metabolite 4'-hydroxycypermethrin, which exhibits no intrinsic toxicity towards susceptible larvae. In a bioassay, CYP337B3 confers a 7-fold resistance towards cypermethrin in FSD larvae compared to susceptible larvae from the Australian TWB strain lacking CYP337B3. Linkage analysis shows that presence of CYP337B3 accounts for most of the cypermethrin resistance in the FSD strain; up-regulation of other P450s in FSD plays no detectable role in resistance. The presence or absence of CYP337B3 can be easily detected by a simple PCR screen, providing a powerful tool to rapidly distinguish resistant from susceptible individuals in the field and to determine the geographical distribution of this resistance gene. Our results suggest that CYP337B3 evolved twice independently by unequal crossing-over between CYP337B2 and two different CYP337B1 alleles.
authors: Department of Entomology, Max Planck Institute for Chemical Ecology, Hans-Knöll-Str. 8, 07745 Jena, Germany. Electronic address: akhtarrasool@hotmail.com.
authors: Akhtar
authors: A
authors: Rasool
authors: Department of Entomology, Max Planck Institute for Chemical Ecology, Hans-Knöll-Str. 8, 07745 Jena, Germany. Electronic address: nicole.joussen@gmx.de.
authors: Nicole
authors: N
authors: Joußen
authors: Research Group Mass Spectrometry, Max Planck Institute for Chemical Ecology, Hans-Knöll-Str. 8, 07745 Jena, Germany. Electronic address: lorenz@ice.mpg.de.
authors: Sybille
authors: S
authors: Lorenz
authors: Research Group Biosynthesis/Nuclear Magnetic Resonance, Max Planck Institute for Chemical Ecology, Hans-Knöll-Str. 8, 07745 Jena, Germany. Electronic address: ellinger@ice.mpg.de.
authors: Renate
authors: R
authors: Ellinger
authors: Research Group Biosynthesis/Nuclear Magnetic Resonance, Max Planck Institute for Chemical Ecology, Hans-Knöll-Str. 8, 07745 Jena, Germany. Electronic address: schneider@ice.mpg.de.
authors: Bernd
authors: B
authors: Schneider
authors: Department of Entomology, Max Planck Institute for Chemical Ecology, Hans-Knöll-Str. 8, 07745 Jena, Germany. Electronic address: skhan@ice.mpg.de.
authors: Sher Afzal
authors: SA
authors: Khan
authors: Insect Molecular Biology Lab, National Institute for Biotechnology and Genetic Engineering (NIBGE), P.O. Box 577, Jhang Road, Faisalabad, Pakistan. Electronic address: mashfaq@uoguelph.ca.
authors: Muhammad
authors: M
authors: Ashfaq
authors: Department of Entomology, Max Planck Institute for Chemical Ecology, Hans-Knöll-Str. 8, 07745 Jena, Germany. Electronic address: heckel@ice.mpg.de.
authors: David G
authors: DG
authors: Heckel
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001681:Biological Assay; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics* / Q000378:metabolism; D007305:Insecticide Resistance / Q000235:genetics*; D007306:Insecticides / Q000494:pharmacology*; D007814:Larva / Q000187:drug effects; D008969:Molecular Sequence Data; D009036:Moths / Q000187:drug effects* / Q000201:enzymology* / Q000378:metabolism; D010154:Pakistan; D020033:Protein Isoforms; D011722:Pyrethrins / Q000494:pharmacology*
chemical_list: D007306:Insecticides; D020033:Protein Isoforms; D011722:Pyrethrins; C017160:cypermethrin; D003577:Cytochrome P-450 Enzyme System
keywords: Cypermethrin; Cytochrome P450 monooxygenase CYP337B3; Helicoverpa armigera; Pest management; Pyrethroid resistance; Unequal crossing-over