Location: Southern Insect Management ResearchTitle: Genetic knockouts indicate that the ABCC2 protein in the bollworm Helicoverpa zea is not a major receptor for the Cry1Ac insecticidal protein
|ABDELGAFFAR, HEBA - University Of Tennessee|
|JURAT-FUENTES, JUAN LUIS - University Of Tennessee|
|Reddy, Gadi V.P.|
Submitted to: Genes
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/26/2021
Publication Date: 9/28/2021
Citation: Perera, O.P., Little, N., Abdelgaffar, H., Jurat-Fuentes, J., Reddy, G.V. 2021. Genetic knockouts indicate that the ABCC2 gene in the bollworm Helicoverpa zea is not a major receptor for the Cry1Ac insecticidal protein. Genes. 12(10):1522. https://doi.org/10.3390/genes12101522.
Interpretive Summary: ATP binding cassette transporter subfamily C2 (ABCC2) in several noctuid moth species function as receptors for the Cry1Ac insecticidal protein from the soil bacterium Bacillus thuringiensis (Bt). Some pest moth species have become resistant to Cry1Ac produced by genetically modified crops due to mutations in ABCC2 protein. In this study, a series of mutations that deleted functional domains of the ABCC2 protein were used to evaluate the role of ABCC2 gene as a receptor for Cry1Ac in the bollworm, Helicoverpa zea. Bioassays of mutant insects with Cry1Ac revealed that ABCC2 is not a major receptor for Cry1Ac toxin in the bollworm and other proteins in the midgut may serve as receptors for Cry1Ac in this insect.
Technical Abstract: Members of the insect ATP binding cassette transporter subfamily C2 (ABCC2) in several moth species are known as receptors for the Cry1Ac insecticidal protein from Bacillus thuringiensis (Bt). Mutations that abolish the functional domains of ABCC2 are known to cause resistance to Cry1Ac, although the reported levels of resistance vary widely depending on insect species. In this study, the function of the ABCC2 gene as a putative Cry1Ac receptor in Helicoverpa zea, a major pest of over 300 crops, was evaluated using CRISPR/Cas9 to progressively eliminate different functional ABCC2 domains. Results from bioassays with edited insect lines support that mutations in ABCC2 were associated with Cry1Ac resistance ratios (RR) ranging from 7.3- to 39.8-fold. No significant differences in susceptibility to Cry1Ac were detected between H. zea with partial or complete ABCC2 knockout, although the highest levels of tolerance were observed when knocking out half of ABCC2. Based on >500–1000-fold RRs reported in similar studies for closely related moth species, the low RRs observed in H. zea knockouts support that ABCC2 is not a major Cry1Ac receptor in this insect.