New Mechanism of Resistance of Helicoverpa armigera to transgenic Bt crops discovered by Chinese Academy of Agricultural Sciences

??? People's Daily, Beijing, Feb. 16 (Reporter Ma Li) recently, it was learned from the Institute of Plant Protection of the Chinese Academy of Agricultural Sciences that a study by the cash crop pest monitoring and control team found that a variation in the toxin receptor gene ABCC2 of Bacillus thuringiensis (Bt) in cotton bollworm could lead to a high level of resistance to Bt crops, but this variation significantly increased the sensitivity of resistant cotton bollworm to another biotoxin avermectin. The relevant research results were published online in the well-known international journal Public Library Pathogens (PLoS Pathogens) on Feb. 12.

??? It is reported that crystal proteins produced in the metabolic process of Bacillus thuringiensis (Bt) have toxic effects on a variety of pests. Bt cotton, Bt corn and Bt soybeans bred by transgenic technology have been commercialized all over the world.

??? Avermectin is a kind of 16-membered macrolides with insecticidal, acaricidal and nematicidal activities, which is produced by Streptomyces avermitilis fermentation and is widely used in the control of agricultural pests. Adenosine triphosphate binding box transporter (ABC transporter) is a kind of membrane integrin, which plays an important role in maintaining the normal physiological function of cells. ABCC2 is an important member of the ABC transporter family, which is responsible for enriching and transporting heavy metal ions and secondary metabolites in the intestinal cavity and digestive tract of insects. It is a potential toxin receptor newly discovered in insects and plays an important role in the metabolic clearance of exogenous toxins in insects. This study found that cotton bollworm ABCC2 is the receptor of Bt toxin Cry1Ac, and its variation can lead to the loss of binding sites of Bt-Cry1Ac toxin in the midgut of Helicoverpa armigera, resulting in a high level of resistance to Bt crops. Because the ABCC2 gene of Helicoverpa armigera has the biological function of metabolizing and excluding avermectin from the insect, the variation of ABCC2 leads to the accumulation of avermectin in the worm and significantly increases its insecticidal toxicity. This study confirmed the negative cross-resistance of Helicoverpa armigera to two biotoxins and explained its molecular mechanism, which provided a new idea for the resistance management of cotton bollworm and other target pests to Bt crops. At the same time, this study also laid a foundation for further analysis of the interaction between cotton bollworm / Bt toxin / avermectin and further clarifying the co-evolutionary mechanism between insects and pathogenic microorganisms.

??? The study was completed by cooperation between the Institute of Plant Protection and Central China normal University, and was supported by projects such as the National Natural Science Foundation of China. The Institute of Plant Protection is the first completion unit of the thesis, Dr. Xiao Yutao is the first author, and Academician Wu Kongming is the correspondent author of the paper.