Venomous protease of aphid soldier for colony defense
Venomous protease of aphid soldier for colony defense
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DOI：
10.1073/pnas.0402462101
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发表时间：
2004-08-03
影响因子：
11.1
通讯作者：
Fukatsu, T
中科院分区：
文献类型：
--
作者：
Kutsukake, M;Shibao, H;Fukatsu, T
在社会性蚜虫中，士兵和普通昆虫之间的形态、行为和生理上的差异归因于它们之间基因表达的差异，因为它们是由同一母亲孤雌生殖产生的克隆后代。利用cDNA差减技术，我们在二龄士兵亚种中鉴定了一种组织蛋白B家族的士兵特异性半胱氨酸水解酶。组织蛋白酶8基因在士兵和注定要成为士兵的一龄若虫中特异表达。组织蛋白酶B蛋白在士兵中优先表达，具有典型的组织蛋白酶B活性。组织蛋白酶B基因和蛋白定位于士兵的中肠。在群体防御中，士兵用刺刀攻击敌人，导致受害者瘫痪和死亡。值得注意的是，在士兵攻击蛾幼虫后，从瘫痪的幼虫中检测到组织蛋白酶B蛋白。注射纯化的重组组织蛋白酶B蛋白对受体蛾幼虫具有明显的致死作用。根据这些结果，我们得出结论，组织蛋白酶B蛋白是烟粉虱士兵产生的棉铃虫毒液的主要成分。组织蛋白酶B基因的士兵专一性表达也存在于夜蜂属的其他社会性蚜虫中。士兵特有的组织蛋白酶B基因表现出加速的分子进化，可能是正选择的作用所致，这也是从其他动物的有毒蛋白中已知的。
in social aphids, morphological, behavioral, and physiological differences between soldiers and normal insects are attributed to differences in gene expression between them, because they are clonal offspring parthenogenetically produced by the same mothers. By using cDNA subtraction, we identified a soldier-specific cysteine protease of the family cathepsin B in a social aphid, Tuberaphis styraci, with a second-instar soldier caste. The cathepsin 8 gene was specifically expressed in soldiers and first-instar nymphs destined to be soldiers. The cathepsin B protein was preferentially produced in soldiers and showed a protease activity typical of cathepsin B. The cathepsin B mRNA and protein were localized in the midgut of soldiers. For colony defense, soldiers attack enemies with their stylet, which causes paralysis and death of the victims. Notably, after soldiers attacked moth larvae, the cathepsin B protein was detected from the paralyzed larvae. Injection of purified recombinant cathepsin B protein certainly killed the recipient moth larvae. From these results, we concluded that the cathepsin B protein is a major component of the aphid venom produced by soldiers of T. styraci. Soldier-specific expression of the cathepsin B gene was found in other social aphids of the genus Tuberaphis. The soldier-specific cathepsin B gene showed an accelerated molecular evolution probably caused by the action of positive selection, which had been also known from venomous proteins of other animals.