作　　者： ; ; ; ; ;

机构地区： 河北农业大学植物保护学院河北省农作物病虫害生物防治工程技术研究中心

出　　处： 《昆虫学报》 2008年第6期601-608,共8页

摘　　要： 嗜线虫致病杆菌Xenorhabdus nematophila在侵入到寄主昆虫血腔后能够成功地逃避或抑制寄主昆虫的免疫反应并快速杀死昆虫。为深入了解嗜线虫致病杆菌的杀虫机理,明确关键的致病因子,作者应用盐析和制备型非变性凝胶电泳等方法,从嗜线虫致病杆菌HB310菌株的细胞内分离纯化了一种新的杀虫蛋白——Tp40,该蛋白对大蜡螟Galleria mellonella具有高血腔注射活性,对大蜡螟5龄幼虫的LD50为68.54ng/头。本文检测了该毒素对大蜡螟幼虫的致病特性,注射Tp40毒素后,大蜡螟幼虫表现出兴奋和痉挛等症状,当以不低于(70±0.02)ng/头的剂量注射Tp40,大蜡螟幼虫均在20min内死亡,但试虫的体色、血淋巴的颜色以及血细胞的形态没有发生明显的变化。对大蜡螟体内酶活性的测定结果显示,在注射LD50剂量的Tp40蛋白后,试虫体内羧酸酯酶和乙酰胆碱酯酶活力都明显的高于对照(P<0.05),而酚氧化酶活力显著低于对照(P<0.05)。对大蜡螟幼虫中肠的组织病理学研究显示:这种42kDa蛋白能够破坏试虫的中肠组织,导致其肠壁细胞出现排列紊乱、脱落和围食膜消失。据此推测,Tp40与嗜线虫致病杆菌对寄主昆虫的免疫抑制有关,寄主中肠组织可能是其作用靶标之一。 Xenorhabdus nematophila is an insect pathogen that overcomes immune response of insect host and kills a wide range of insects. To address the lethal mechanisms of the bacterium, we isolated and characterized the insecticidal toxins from X. nernatophila HB310 strain. A new protein Tp40 with high injectable haemocoel activity to Galleria mellonella larvae was obtained using methods such as salting out and native-PAGE from the cells of X. nematophila HB310. The injectable hemocoelic potency （LDso） of Tp40 was 68.54 ng/larva against 5th-instar larvae of G. mellonella. Post injection of Tp40, the larvae ceased feeding almost immediately and showed excitement and convulsion. The larvae injected with the dose of more than （70 ± 0.02） ng/larva of Tp40 all died within 20 min. The color of body and hemolymph of Tp40 treated larvae did not change distinctly. The hemocytes of Tp40-treated larvae also were not destroyed. The activity of the carboxylesterase （CarE） and the acetylcholinesterase （AchE） of G. mellonella larvae injected with the LD50 dose of Tp40 were obviously higher than that of PBS-control （ P 〈 0.05）, respectively.However, polyphenoloxidase （PO） activity of the Tp40-injected larvae was markedly lower than that of the control （ P 〈 0.05 ）. The study on the histopathology of the midgut of G. mellonella indicated that Tp40 destroyed the epithelium and the peritrophic membrane of the midgut. These results suggest that Tp40 was likely to be associated with the immunosuppression by X. nematophila to hosts. The midgut tissues of the host may be one of the acting targets of Tp40.

关 键 词： 嗜线虫致病杆菌 血腔毒素 酶活力 大蜡螟 中肠

领　　域： [生物学]