+ Site Statistics
+ Search Articles
+ PDF Full Text Service
How our service works
Request PDF Full Text
+ Follow Us
Follow on Facebook
Follow on Twitter
Follow on LinkedIn
+ Subscribe to Site Feeds
Most Shared
PDF Full Text
+ Translate
+ Recently Requested

Binding sites alteration is responsible for field-isolated resistance to Bacillus thuringiensis Cry2A insecticidal proteins in two Helicoverpa species

Binding sites alteration is responsible for field-isolated resistance to Bacillus thuringiensis Cry2A insecticidal proteins in two Helicoverpa species

PLoS ONE 5(4): e9975

Evolution of resistance by target pests is the main threat to the long-term efficacy of crops expressing Bacillus thuringiensis (Bt) insecticidal proteins. Cry2 proteins play a pivotal role in current Bt spray formulations and transgenic crops and they complement Cry1A proteins because of their different mode of action. Their presence is critical in the control of those lepidopteran species, such as Helicoverpa spp., which are not highly susceptible to Cry1A proteins. In Australia, a transgenic variety of cotton expressing Cry1Ac and Cry2Ab (Bollgard II) comprises at least 80% of the total cotton area. Prior to the widespread adoption of Bollgard II, the frequency of alleles conferring resistance to Cry2Ab in field populations of Helicoverpa armigera and Helicoverpa punctigera was significantly higher than anticipated. Colonies established from survivors of F2 screens against Cry2Ab are highly resistant to this toxin, but susceptible to Cry1Ac. Methodology/Principal Findings: Bioassays performed with surface-treated artificial diet on neonates of H. armigera and H. punctigera showed that Cry2Ab resistant insects were cross-resistant to Cry2Ae while susceptible to Cry1Ab. Binding analyses with 125 I-labeled Cry2Ab were performed with brush border membrane vesicles from midguts of Cry2Ab susceptible and resistant insects. The results of the binding analyses correlated with bioassay data and demonstrated that resistant insects exhibited greatly reduced binding of Cry2Ab toxin to midgut receptors, whereas no change in 125 I-labeled- Cry1Ac binding was detected. As previously demonstrated for H. armigera, Cry2Ab binding sites in H. punctigera were shown to be shared by Cry2Ae, which explains why an alteration of the shared binding site would lead to cross-resistance between the two Cry2A toxins. Conclusion/Significance: This is the first time that a mechanism of resistance to the Cry2 class of insecticidal proteins has been reported. Because we found the same mechanism of resistance in multiple strains representing several field populations, we conclude that target site alteration is the most likely means that field populations evolve resistance to Cry2 proteins in Helicoverpa spp. Our work also confirms the presence in the insect midgut of specific binding sites for this class of proteins. Characterizing the Cry2 receptors and their mutations that enable resistance could lead to the development of molecular tools to monitor resistance in the field.

Please choose payment method:

(PDF emailed within 1 workday: $29.90)

Accession: 037397109

Download citation: RISBibTeXText

Related references

Binding site alteration is responsible for field-isolated resistance to Bacillus thuringiensis Cry2A insecticidal proteins in two Helicoverpa species. Plos one 5(4): E9975, 2010

Specific binding of Bacillus thuringiensis Cry2A insecticidal proteins to a common site in the midgut of Helicoverpa species. Applied and Environmental Microbiology 74(24): 7654-7659, 2008

Safety Assessment of Bacillus thuringiensis Insecticidal Proteins Cry1C and Cry2A with a Zebrafish Embryotoxicity Test. Journal of Agricultural and Food Chemistry 66(17): 4336-4344, 2018

Analysis, of Cry2A proteins encoded by genes cloned from indigenous isolates of Bacillus thuringiensis for toxicity against Helicoverpa armigera. Current Science 86(4): 566-570, 2004

Toxicity of Bacillus thuringiensis insecticidal proteins for Helicoverpa armigera and Helicoverpa punctigera (Lepidoptera: Noctuidae), major pests of cotton. Journal of Invertebrate Pathology 80(1): 55-63, 2002

Differential effects of helper proteins encoded by the cry2A and cry11A operons on the formation of Cry2A inclusions in Bacillus thuringiensis. Fems Microbiology Letters 165(1): 35-41, 1998

CRISPR/Cas9 mediated genome editing of Helicoverpa armigera with mutations of an ABC transporter gene HaABCA2 confers resistance to Bacillus thuringiensis Cry2A toxins. Insect Biochemistry and Molecular Biology 87: 147-153, 2017

Specific binding of radiolabeled Cry1Fa insecticidal protein from Bacillus thuringiensis to midgut sites in lepidopteran species. Applied and Environmental Microbiology 78(11): 4048-4050, 2012

Characteristics of resistance to Bacillus thuringiensis toxin Cry2Ab in a strain of Helicoverpa punctigera (Lepidoptera: Noctuidae) isolated from a field population. Journal of Economic Entomology 103(6): 2147-2154, 2010

Susceptibility of Helicoverpa armigera Hubner instars to Bacillus thuringiensis insecticidal crystal proteins. Pesticide Research Journal 18(2): 186-189, 2006

Analysis of cross-resistance to Vip3 proteins in eight insect colonies, from four insect species, selected for resistance to Bacillus thuringiensis insecticidal proteins. Journal of Invertebrate Pathology 155: 64-70, 2018

Field evaluation of transgenic corn containing Bacillus thuringiensis Berliner insecticidal protein gene against Helicoverpa zea. Journal of Entomological Science 31(3): 340-346, 1996

Resistance monitoring of Helicoverpa armigera (Lepidoptera Noctuidae) to Bacillus thuringiensis insecticidal protein in China. Journal of Economic Entomology 95(4): 826-831, 2002

Knockout of three aminopeptidase N genes does not affect susceptibility of Helicoverpa armigera larvae to Bacillus thuringiensis Cry1A and Cry2A toxins. Insect Science 2019:, 2019

Inheritance and cross-resistance of Bacillus thuringiensis insecticidal crystal protein Cry1Ac resistance in cotton bollworm Helicoverpa armigera Hubner population from Tamil Nadu, India. Journal of pest science 80(3): 175-181, 2007