Characterization of Venom and Oviduct Components of Parasitoid Wasp Asobara japonica.
Characterization of Venom and Oviduct Components of Parasitoid Wasp Asobara japonica.
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DOI：
10.1371/journal.pone.0160210
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发表时间：
2016
期刊：
影响因子：
3.7
通讯作者：
Hayakawa Y
中科院分区：
文献类型：
--
作者：
Furihata S;Matsumura T;Hirata M;Mizutani T;Nagata N;Kataoka M;Katayama Y;Omatsu T;Matsumoto H;Hayakawa Y
在自然寄生过程中，日本天牛在注射毒液后不久将侧输卵管(LO)成分引入果蝇体内，以中和其强烈的毒性，否则寄主将死亡。尽管成功寄生所必需的毒液和LO组分之间的协调关系已经引起了这一领域的许多研究人员的注意，但这两个因素的分子性质仍然不明确。我们在这里表明，通过超速离心法沉淀的毒液成分产生的有毒部分经紫外线照射、煮沸和超声波处理后被灭活，这表明它是一种类似病毒的实体。超速离心后的沉淀物形态观察显示，大小不均的球形病毒样颗粒直径为20~40 nm。该毒素对黑腹水母幼虫的毒害作用不是被LO组分直接中和，而是被LO因子激活的血淋巴中和因子所阻断。此外，我们还发现日本曲线虫毒液和LO组分对斜纹夜蛾幼虫的作用相似：注射毒液可导致斜纹夜蛾幼虫死亡，但联合注射LO因子可保护斜纹夜蛾幼虫免受毒液的毒害。而与黑腹隐翅虫亲缘关系较近但非习性寄主的无花果夜蛾和双果夜蛾，由于其血淋巴中具有天然的中和活性，并未受到日本隐翅虫毒液的负面影响，说明它们在进化过程中一定获得了日本隐翅虫毒液的中和剂。这些结果为了解毒液和LO组分的特征提供了新的见解：虽然非习惯性寄主果蝇的血淋巴中和物具有活性，但在进化过程使它们能够使用LO因子激活宿主血淋巴中和剂前体后，日本蜜蜂雌性利用了类似病毒的有毒毒液因子来利用更广泛的宿主物种。
During natural parasitization, Asobara japonica wasps introduce lateral oviduct (LO) components into their Drosophila hosts soon after the venom injection to neutralize its strong toxicity; otherwise, the host will die. Although the orchestrated relationship between the venom and LO components necessary for successful parasitism has attracted the attention of many researchers in this field, the molecular natures of both factors remain ambiguous. We here showed that precipitation of the venom components by ultracentrifugation yielded a toxic fraction that was inactivated by ultraviolet light irradiation, boiling, and sonication, suggesting that it is a virus-like entity. Morphological observation of the precipitate after ultracentrifugation showed small spherical heterogeneous virus-like particles 20–40 nm in diameter. The venom’s detrimental effect on D. melanogaster larvae was not directly neutralized by the LO components but blocked by a hemolymphal neutralizing factor activated by the LO factor. Furthermore, we found that A. japonica venom and LO components acted similarly on the larvae of the common cutworm Spodoptera litura: the venom injection caused mortality but coinjection of the LO factor protected S. litura larvae from the venom’s toxicity. In contrast, D. ficusphila and D. bipectinata, which are closely related to D. melanogaster but non-habitual host species of A. japonica, were not negatively affected by A. japonica venom due to an intrinsic neutralizing activity in their hemolymph, indicating that these species must have acquired a neutralizer of A. japonica venom during evolution. These results give new insights into the characteristics of both the venom and LO components: A. japonica females have utilized the virus-like toxic venom factor to exploit a wider range of host species after the evolutionary process enabled them to use the LO factor for activation of the host hemolymph neutralizer precursor, although the non-habitual host Drosophila species possess an active intrinsic neutralizer in their hemolymph.