Abstract
Ostrinia furnacalis is an important borer on maize. Long-term and large-scale planting of transgenic corn has led O. furnacalis evolving resistance and reducing the control effect. Recently, high levels of resistance to Bt Cry1 toxins have been reported to be genetically linked to the mutation or down-regulation of ABC transporter subfamily G gene ABCG4 in O. furnacalis. In order to further determine the relationship between ABCG4 gene and the resistance to Cry1 toxins in O. furnacalis, the novel CRISPR/Cas9 genome engineering system was utilized to successfully construct ABCG4-KO knockout homozygous strain. Bioassay results indicated that an ABCG4-KO strain had a higher resistance to Cry1 proteins compared with a susceptible strain (ACB-BtS). The result indicates that the ABCG4 gene may act as a receptor of the Bt Cry1 toxin in O. furnacalis. Furthermore, the development time was significantly changed in the early stage ABCG4-KO larvae, and the population parameters were also significantly changed. In summary, our CRISPR/Cas9-mediated genome editing study presents evidence that ABCG4 gene is a functional receptor for Bt Cry1 toxins, laying the foundation for further clarification of the Bt resistance mechanism.
Highlights
The Asian corn borer (ACB), Ostrinia furnacalis (Lepidoptera: Crambidae), is a worldwide agricultural pest that causes damage from East and Southeast Asia to the Western Pacific islands [1]
The results showed that CRISPR/Cas9 editing of the ABCG4 gene in the susceptible ACB-BtS strain significantly increased the resistance to Cry1 toxins
Studies showed that Alkaline phosphatase (ALP) [28], Aminopeptidase N (APN) [29], Cadherin (CAD) [30], and some other proteins are the receptors of Bacillus thuringiensis (Bt) toxins [31]
Summary
The Asian corn borer (ACB), Ostrinia furnacalis (Lepidoptera: Crambidae), is a worldwide agricultural pest that causes damage from East and Southeast Asia to the Western Pacific islands [1]. Chemical insecticides are used to control O. furnacalis, which has led to several problems, including environmental pollution, the occurrence of resistance, and loss of biodiversity [3]. Bt produces insecticidal crystalline proteins during sporulation. The crystalline proteins are dissolved to a fragment after being ingested by an insect. The active fragments are processed by a proteolytic enzyme, binding to specific receptors on the brush boundary membrane of the midgut epithelium. Bt toxin receptors play an important role in toxin specificity and toxicity, and mutations in these genes lead to high levels of resistance in many insect species. Plutella xylostella was the first documented pest that developed Bt resistance in the field, repeated application of Bt protein insecticide produced significant resistance in P. xylostella [8–12]
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