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Toxins 2019, 11(4), 186; https://doi.org/10.3390/toxins11040186

Pink Bollworm Resistance to Bt Toxin Cry1Ac Associated with an Insertion in Cadherin Exon 20

1
Key Laboratory of Integrated Pest Management on Crops in Central China, Ministry of Agriculture, Hubei Key Laboratory of Crop Disease, Insect Pests and Weeds Control, Institute of Plant Protection and Soil Fertility, Hubei Academy of Agricultural Sciences, Wuhan 430064, China
2
State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, China
3
School of Life Science, Central China Normal University, Wuhan 430079, China
4
Agricultural Genomics Institute at Shenzhen, Chinese Academy of Agricultural Sciences, Shenzhen 518120, China
5
Department of Entomology, University of Arizona, Tucson, AZ 85721, USA
*
Author to whom correspondence should be addressed.
Received: 24 March 2019 / Accepted: 26 March 2019 / Published: 28 March 2019
(This article belongs to the Special Issue Insecticidal Toxins from Bacillus thuringiensis)
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Abstract

Insecticidal proteins from Bacillus thuringiensis (Bt) are widely used to control insect pests, but their efficacy is reduced when pests evolve resistance. We report on a novel allele (r16) of the cadherin gene (PgCad1) in pink bollworm (Pectinophora gossypiella) associated with resistance to Bt toxin Cry1Ac, which is produced by transgenic cotton. The r16 allele isolated from a field population in China has 1545 base pairs of a degenerate transposon inserted in exon 20 of PgCad1, which generates a mis-spliced transcript containing a premature stop codon. A strain homozygous for r16 had 300-fold resistance to Cry1Ac, 2.6-fold cross-resistance to Cry2Ab, and completed its life cycle on transgenic Bt cotton producing Cry1Ac. Inheritance of Cry1Ac resistance was recessive and tightly linked with r16. Compared with transfected insect cells expressing wild-type PgCad1, cells expressing r16 were less susceptible to Cry1Ac. Recombinant cadherin protein was transported to the cell membrane in cells transfected with the wild-type PgCad1 allele, but not in cells transfected with r16. Cadherin occurred on brush border membrane vesicles (BBMVs) in the midgut of susceptible larvae, but not resistant larvae. These results imply that the r16 allele mediates Cry1Ac resistance in pink bollworm by interfering with the localization of cadherin. View Full-Text
Keywords: Bt cotton; resistance mechanism; Cry1Ac; Bacillus thuringiensis; Pectinophora gossypiella; genetically engineered crop; transposon Bt cotton; resistance mechanism; Cry1Ac; Bacillus thuringiensis; Pectinophora gossypiella; genetically engineered crop; transposon
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Wang, L.; Ma, Y.; Guo, X.; Wan, P.; Liu, K.; Cong, S.; Wang, J.; Xu, D.; Xiao, Y.; Li, X.; Tabashnik, B.E.; Wu, K. Pink Bollworm Resistance to Bt Toxin Cry1Ac Associated with an Insertion in Cadherin Exon 20. Toxins 2019, 11, 186.

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