Why can cotton bollworm resist transgenic Bt crops? CAAS discovers new mechanism
??? People's Daily Online, Beijing, February 16 (Reporter Ma Li) Recently, it was learned from the Institute of Plant Protection of the Chinese Academy of Agricultural Sciences that the institute's economic crop pest monitoring and control team found that variation in the Bacillus thuringiensis (Bt) toxin receptor gene ABCC2 in cotton bollworm can lead to high-level resistance to Bt crops, but this variation significantly increases the sensitivity of resistant cotton bollworm to another biological toxin, abamectin. The related research results were published online on February 12 in the internationally renowned journal PLoS Pathogens.
??? It is reported that the crystal proteins produced during the metabolism of Bacillus thuringiensis (Bt) have toxic effects on a variety of pests, and Bt cotton, Bt corn and Bt soybean developed using transgenic technology have been commercially planted worldwide.
??? Abamectin is a class of sixteen-membered macrolide compounds with insecticidal, acaricidal and nematicidal activity, produced by fermentation of Streptomyces avermitilis among streptomycetes, and is widely used in the control of agricultural pests. ATP-binding cassette transporters (ABC transporters) are a class of membrane-integrated proteins that play an important role in maintaining normal physiological functions of cells; ABCC2 is an important member of the ABC transporter family genes, responsible for concentrating and transporting heavy metal ions and secondary metabolites from the intestinal lumen and digestive tract of insects to the outside, and is a newly discovered potential toxin receptor in insects, playing an important function in the process of insect metabolic clearance of exogenous toxins. The study found that cotton bollworm ABCC2 is a receptor for the Bt toxin Cry1Ac, and its variation can cause the Bt-Cry1Ac toxin to lose its binding site in the midgut of cotton bollworm, thereby producing high-level resistance to Bt crops. Because the cotton bollworm ABCC2 gene has the biological function of metabolically excluding abamectin from the insect body, variation in ABCC2 leads to the accumulation of abamectin in the insect body and significantly increases its insecticidal toxicity. This study confirmed the phenomenon of negative cross-resistance in cotton bollworm to two biological toxins and explained its molecular mechanism, providing new ideas for the resistance management of target pests such as cotton bollworm to Bt crops. At the same time, this study also laid the foundation for further analyzing the interaction relationship of cotton bollworm/Bt toxin/abamectin and further clarifying the coevolution mechanism between insects and pathogenic microorganisms.
??? This study was completed by the Institute of Plant Protection in cooperation with Central China Normal University and other units, and was funded by projects such as the Innovation Research Group of the National Natural Science Foundation of China. The Institute of Plant Protection was the first completing unit of the paper, Dr. Xiao Yutao was the first author of the paper, and Academician Wu Kongming was the corresponding author of the paper.