Bacillus thuringiensis Bel Protein Enhances the Toxicity of Cry1Ac Protein to Helicoverpa armigera Larvae by Degrading Insect Intestinal Mucin
Bacillus thuringiensis Bel Protein Enhances the Toxicity of Cry1Ac Protein to Helicoverpa armigera Larvae by Degrading Insect Intestinal Mucin
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DOI：
10.1128/aem.00532-09
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发表时间：
2009-08-15
影响因子：
4.4
通讯作者：
Sun, Ming
中科院分区：
文献类型：
--
作者：
Fang, Shangling;Wang, Li;Sun, Ming
苏云金芽孢杆菌已被用作生物杀虫剂来控制农业昆虫。蜡状芽孢杆菌基因组中含有一个类似芽孢杆菌增强蛋白的基因，编码一种与病毒增强蛋白具有20 ~ 30%同源性的多肽，它能通过降解昆虫中肠围食基质（PM）来增强病毒的感染。在这项研究中，发现bel基因具有与病毒增强蛋白基因相似的活性。通过使用无质粒B构建bel敲除突变体。苏云金杆菌衍生物BMB 171。该突变体加上cry 1Ac杀虫蛋白基因的50%致死浓度比BMB 171菌株高约5.8倍。当纯化的Bel与Cry 1Ac蛋白混合并饲喂棉铃虫幼虫时，单独3 μ g/ml Cry 1Ac诱导34.2%的死亡率。同时，当等量的Cry 1Ac与0.8 μ g/ml的Bel混合时，死亡率上升到74.4%。显微镜下观察发现，在中肠PM上检测到显著的破坏。棉铃虫幼虫取食Bel.体外降解实验表明，Bel对粉纹夜蛾和H.棉铃虫幼虫的各种降解产物，类似于病毒增强蛋白的发现。这些结果表明Bel毒性增强依赖于中肠PM和IIM的破坏，类似于病毒增强蛋白的情况。这一发现表明Bel具有增强B杀虫活性的潜力。基于苏云金杆菌的生物农药和转基因作物。
Bacillus thuringiensis has been used as a bioinsecticide to control agricultural insects. Bacillus cereus group genomes were found to have a Bacillus enhancin-like (bel) gene, encoding a peptide with 20 to 30% identity to viral enhancin protein, which can enhance viral infection by degradation of the peritrophic matrix (PM) of the insect midgut. In this study, the bel gene was found to have an activity similar to that of the viral enhancin gene. A bel knockout mutant was constructed by using a plasmid-free B. thuringiensis derivative, BMB171. The 50% lethal concentrations of this mutant plus the cry1Ac insecticidal protein gene were about 5.8-fold higher than those of the BMB171 strain. When purified Bel was mixed with the Cry1Ac protein and fed to Helicoverpa armigera larvae, 3 mu g/ml Cry1Ac alone induced 34.2% mortality. Meanwhile, the mortality rate rose to 74.4% when the same amount of Cry1Ac was mixed with 0.8 mu g/ml of Bel. Microscopic observation showed a significant disruption detected on the midgut PM of H. armigera larvae after they were fed Bel. In vitro degradation assays showed that Bel digested the intestinal mucin (IIM) of Trichoplusia ni and H. armigera larvae to various degrading products, similar to findings for viral enhancin. These results imply Bel toxicity enhancement depends on the destruction of midgut PM and IIM, similar to the case with viral enhancin. This discovery showed that Bel has the potential to enhance insecticidal activity of B. thuringiensis-based biopesticides and transgenic crops.