State Key Laboratory of Microbial Technology, Shandong University, Qingdao, China.
School of Life Sciences, Shandong University, Qingdao, China; Taishan College, Shandong University, Jinan, China.
J Biol Chem. 2023 Mar;299(3):103000. doi: 10.1016/j.jbc.2023.103000. Epub 2023 Feb 9.
Microbially derived, protein-based biopesticides offer a more sustainable pest management alternative to synthetic pesticides. Vegetative insecticidal proteins (Vip3), multidomain proteins secreted by Bacillus thuringiensis, represent a second-generation insecticidal toxin that has been preliminarily used in transgenic crops. However, the molecular mechanism underlying Vip3's toxicity is poorly understood. Here, we determine the distinct functions and contributions of the domains of the Vip3Aa protein to its toxicity against Spodoptera frugiperda larvae. We demonstrate that Vip3Aa domains II and III (DII-DIII) bind the midgut epithelium, while DI is essential for Vip3Aa's stability and toxicity inside the protease-enriched host insect midgut. DI-DIII can be activated by midgut proteases and exhibits cytotoxicity similar to full-length Vip3Aa. In addition, we determine that DV can bind the peritrophic matrix via its glycan-binding activity, which contributes to Vip3Aa insecticidal activity. In summary, this study provides multiple insights into Vip3Aa's mode-of-action which should significantly facilitate the clarification of its insecticidal mechanism and its further rational development.
微生物源蛋白类生物农药为替代合成农药的可持续害虫管理提供了一种更优的选择。苏云金芽孢杆菌分泌的多结构域杀虫蛋白 VIP3 是第二代杀虫毒素，初步应用于转基因作物。然而，VIP3 毒性的分子机制尚不清楚。本研究确定了 VIP3Aa 蛋白结构域对其防治玉米螟幼虫的不同功能和贡献。研究表明，VIP3Aa 的结构域 II 和 III（DII-DIII）与中肠上皮结合，而结构域 I（DI）对于 VIP3Aa 在富含蛋白酶的昆虫中肠内的稳定性和毒性至关重要。DI-DIII 可被中肠蛋白酶激活，并表现出与全长 VIP3Aa 相似的细胞毒性。此外，本研究还确定了 DV 通过其糖结合活性与围食膜结合，这有助于 VIP3Aa 的杀虫活性。综上所述，本研究深入了解了 VIP3Aa 的作用模式，这将极大地促进阐明其杀虫机制及其进一步的合理开发。
