Abstract Bacillus thuringiensis (Bt) is a well-known entomopathogen. In this study, we cloned the vip3Aa1 gene from Bt strain GIM1.147 and investigated the insecticidal activity of Bt Vip3Aa1 protein produced by Escherichia coli against Periplaneta americana and Blattella germanica. The results showed that purified Vip3Aa1 exhibited an LC50 at 24 h against P. americana and B. germanica of 0.182 mg·ml-1 and 0.276 mg·ml-1, respectively. Investigations of its mode of action showed that Vip3Aa1 could be proteolyzed into a 62-kDa toxic protein by P. americana gut-soluble proteases. In addition, Vip3Aa1 caused severe damage to the columnar colon and the midgut, as observed through hematoxylin-eosin staining and scanning electron microscopy. The 62-kDa activated Vip3Aa1 protein could form ion channels in the colon and the midgut in vitro. Based on protease activity analysis, Vip3Aa1 at concentrations of 0.125 mg·ml-1 and 0.031 mg·ml-1 could downregulate the activities of glutathione S-transferase, α-NA esterase, trypsin, and chymotrypsin. This report provides the first description of the activity of Vip3Aa1 toxins toward P. americana and B. germanica and demonstrates that the mechanism through which Vip3Aa1 kills P. americana and B. germanica differs from that involved in the killing of lepidopteran insects.

中文翻译：

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Vip3Aa1 对美洲大蠊的活性


摘要 苏云金芽孢杆菌（Bt）是一种众所周知的昆虫病原体。本研究克隆了Bt菌株GIM1.147的vip3Aa1基因，并研究了大肠杆菌产生的Bt Vip3Aa1蛋白对美洲大蠊和德国小蠊的杀虫活性。结果表明，纯化的Vip3Aa1在24 h时对美洲大蠹和德国小蠹的LC50分别为0.182 mg·ml-1和0.276 mg·ml-1。对其作用方式的研究表明，Vip3Aa1 可以被美洲对虾肠溶性蛋白酶水解成 62 kDa 的有毒蛋白。此外，通过苏木精-伊红染色和扫描电镜观察发现，Vip3Aa1对柱状结肠和中肠造成严重损伤。 62 kDa 激活的 Vip3Aa1 蛋白可以在体外在结肠和中肠中形成离子通道。根据蛋白酶活性分析，0.125 mg·ml-1和0.031 mg·ml-1浓度的Vip3Aa1可下调谷胱甘肽S-转移酶、α-NA酯酶、胰蛋白酶和糜蛋白酶的活性。该报告首次描述了 Vip3Aa1 毒素对美洲对虾和德国小蠹的活性，并证明了 Vip3Aa1 杀死美洲对虾和德国小蠹的机制不同于杀死鳞翅目昆虫的机制。