Journal Article

Alternative Splicing and Highly Variable Cadherin Transcripts Associated with Field-Evolved Resistance of Pink Bollworm to Bt Cotton in India

Fabrick, Jeffrey A., Yelich, Alex J., Unnithan, Gopalan C., Carrière, Yves, Tabashnik, Bruce E., Li, Xianchun, Tanwar, Raj K., Ponnuraj, Jeyakumar, Singh, Amar

2014

Overview

Evolution of resistance by insect pests can reduce the benefits of insecticidal proteins from Bacillus thuringiensis (Bt) that are used extensively in sprays and transgenic crops. Despite considerable knowledge of the genes conferring insect resistance to Bt toxins in laboratory-selected strains and in field populations exposed to Bt sprays, understanding of the genetic basis of field-evolved resistance to Bt crops remains limited. In particular, previous work has not identified the genes conferring resistance in any cases where field-evolved resistance has reduced the efficacy of a Bt crop. Here we report that mutations in a gene encoding a cadherin protein that binds Bt toxin Cry1Ac are associated with field-evolved resistance of pink bollworm (Pectinophora gossypiella) in India to Cry1Ac produced by transgenic cotton. We conducted laboratory bioassays that confirmed previously reported resistance to Cry1Ac in pink bollworm from the state of Gujarat, where Bt cotton producing Cry1Ac has been grown extensively. Analysis of DNA from 436 pink bollworm from seven populations in India detected none of the four cadherin resistance alleles previously reported to be linked with resistance to Cry1Ac in laboratory-selected strains of pink bollworm from Arizona. However, DNA sequencing of pink bollworm derived from resistant and susceptible field populations in India revealed eight novel, severely disrupted cadherin alleles associated with resistance to Cry1Ac. For these eight alleles, analysis of complementary DNA (cDNA) revealed a total of 19 transcript isoforms, each containing a premature stop codon, a deletion of at least 99 base pairs, or both. Seven of the eight disrupted alleles each produced two or more different transcript isoforms, which implicates alternative splicing of messenger RNA (mRNA). This represents the first example of alternative splicing associated with field-evolved resistance that reduced the efficacy of a Bt crop.

• Publisher: Public Library of Science,Public Library of Science (PLoS)
• Subject: Agriculture / Alleles / Alternative splicing / Alternative Splicing - genetics / Analysis / Animals / Bacillus thuringiensis / Bacterial Proteins - pharmacology / Base pairs / Base Sequence / Bioassays / Biological Evolution / Biology and life sciences / Cadherins / Cadherins - genetics / Complementary DNA / Cotton / Crops / Cry1Ac toxin / Deoxyribonucleic acid / DNA / DNA sequencing / DNA, Complementary - genetics / Endotoxins - pharmacology / Evolutionary biology / Gelechiidae / Gene amplification / Gene deletion / Gene sequencing / Genes / Genetic research / Genetically modified crops / Gossypium - parasitology / Helicoverpa armigera / Heliothis virescens / Hemolysin Proteins - pharmacology / India / Insect pests / Insecticide resistance / Insecticide Resistance - genetics / Insecticides / Insects / Isoforms / Laboratories / Lepidoptera / Molecular Sequence Data / Moths - drug effects / Moths - genetics / Mutation / Nonsense mutation / Pectinophora gossypiella / Pesticide resistance / Pests / Plants, Genetically Modified - parasitology / Plutella xylostella / Population genetics / Populations / Protein binding / Proteins / Ribonucleic acid / RNA / Sequence Analysis, DNA / Sprayers / Sprays / Stop codon / Toxins / Transcription / Transgenic plants