2024年4月29日，国际顶级学术期刊《自然植物（Nature Plants）》以“iJAZ-based approach to engineer lepidopteran pest resistance in multiple crop species”为题，发表了中国农业科学院棉花研究所李付广研究员团队的最新科研成果，详细介绍了研究团队在棉花中发现的具有广谱应用价值的新型高效杀虫蛋白的分子机制及其应用前景。
Over the years, the research team has been engaged in cotton transgenic research for a long time, and found that the genetically engineered cotton materials from the same batch of transformants were all sterile plants, and it was also found that the sterile strains were resistant to cotton bollworm, and the insect test results showed a high level of resistance. Falling armyworm, which invaded the continent in 2018, is one of the top 10 agricultural pests in the world as recognized by the Food and Agriculture Organization of the United Nations, harming more than 350 species of plants in 76 families and posing a major threat to agricultural production. Fall armyworm is a lepidopteran pest like cotton bollworm. The research team fed Fall Armyworm larvae with the leaves of the sterile cotton plants, which also showed good insecticidal effects. Further studies showed that the sterile phenotype and insect resistance traits of transgenic cotton were caused by the overexpression of GhJAZ24 protein, which is a natural protein derived from cotton.
GhJAZ24 protein showed significant insect resistance to both cotton bollworm and fall armyworm, suggesting that the natural protein may have potential application value in the control of lepidopteran pests. Overexpression of GhJAZ24 protein can lead to sterility in cotton plants, which has become an important obstacle to its breeding application. To this end, the team designed a damage-induced secretory expression vector of GhJAZ24 protein and named it iJAZ. When the pest feeds on the transgenic iJAZ genetically engineered plants, the expression of GhJAZ24 protein is induced in the cells around the leaf tissue damaged by the pest about 1 hour, and the expression level reaches the peak in about 5 hours, and the highly expressed GhJAZ24 protein is secreted into the cells for storage. The fertility of the transgenic cotton obtained by the research team using the iJAZ vector was restored to normal, and it had significant insect resistance.
Fall armyworm is divided into rice type and maize type. The research team used iJAZ vector for transgenic and obtained iJAZ genetically engineered rice and genetically engineered maize, both of which maintained good fertility. In vivo fluorescence imaging of GFP reporter protein showed that GhJAZ24 protein was induced to be induced in iJAZ maize leaves, and the insect test results showed that both iJAZ rice and iJAZ maize showed significant insecticidal effects on fall armyworm. The obtained iJAZ rice and iJAZ corn were fed with rice leaf roller borer and corn borer, respectively, and the same showed high resistance levels.
JAZ protein is a plant-specific transcriptional repressor protein. In-depth studies have found that the NGR motif contained in GhJAZ24 protein can specifically recognize APN receptors that are abundant in the intestinal tract of pests. Studies have shown that the highly homologous sequence of JAZ protein containing NGR motif only exists in a few plants such as cotton, pumpkin, durian, etc. The NGR motif specifically recognizes and binds to the SfAPN4 receptor, so that GhJAZ24 enters the intestinal cells of Fall armyworm and translocates to the nucleus, targeting the activity of SfHDAC3 in the nucleus, resulting in histone acetylation and reprogramming in the cells, resulting in inflammation in the intestinal surface cells, and may further trigger the disorder of stem cell mitosis in the surface cells, and the eventual death of Fall Armyworm. Homology analysis showed that the NHP domain of SfAPN4 and the Zn binding site domain of SfHDAC3 targeted by GhJAZ24 were conserved among other herbivores, especially lepidopteran pests, including Helicoverpa armigera, Ostrinia nubilalis corn borer, Plutella xylostella, Manduca sexta, and Danaus These suggested that GhJAZ24, a native protein of cotton, may have broad-spectrum insecticidal properties against lepidopteran pests, and may also be resistant to other insects with NHP domains and highly conserved Zn binding sites.
The insecticidal mechanism of GhJAZ24 protein is completely different from that of Bacillus thuringiensis Bt Cry1Ac protein. The NGR-containing GhJAZ24 protein enters Fall Armyworm cells by binding to the NHP domain of the APN receptor (345N-472Y), while the Cry1Ac protein binds to the 949T-970T region of APN1 of Hipsypodia armyworm. Some lepidopteran pests, such as fall armyworm, have been reported to become resistant to the Cry1Ac protein. The results of this study showed that GhJAZ24 protein had good complementarity with Cry1Ac protein, and its insecticidal spectrum was broader.
iJAZ was a damage-induced secretory expression vector, and the GhJAZ24 protein of iJAZ genetically engineered plants was only induced in the cells around the leaf area where the pests fed on the leaves, while the harvested crop seeds or fruits did not contain GhJAZ24 protein due to gene expression.
The research team believes that the iJAZ vector has a broad application prospect in the control of major lepidopteran pests in crops, and may also play an important role in the control of lepidopteran pests in forests and grasses, fruits and vegetables. GhJAZ24 protein is composed of 119 amino acids (Cry1Ac contains 1178 amino acids), and the effective polypeptide is about 40 amino acids, with small molecular weight, easy synthesis, convenient storage and transportation, and is expected to be sprayed on crops as a biological insecticide to be environmentally friendly and residueless, and can be used as a green biopesticide for the prevention and control of various types of lepidopteran pests, and may also have important application prospects.
Mo Huijuan, associate researcher of China Cotton Institute, is the first author, Chang Huimin, a doctoral student of China Cotton Institute, Dr. Zhao Ge of the College of Agriculture of Zhengzhou University, and Hu Guanjing, researcher of China Cotton Institute, are the co-first authors of the paper, Li Fuguang, a researcher of China Cotton Institute, is the corresponding author of the paper, Professor Ren Maozhi of the Institute of Urban Agriculture of the Chinese Academy of Agricultural Sciences, Chen Xiaoya, academician of Shanghai Chenshan Botanical Garden, and Jonathan F. Wendel, academician of Iowa State University, USA, are the co-corresponding authors of the paper. This work was supported by the National Key R&D Program of China (No. 2020YFA0908000 and 2023YFE0199400) and the National Natural Science Foundation of China (No. 31621005, U23A20182, U1804231 and 31972469).
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