Aphids harbor nine common facultative symbionts, most mediating one or more ecological interactions. Wolbachia pipientis, well-studied in other arthropods, remains poorly characterized in aphids. In Pentalonia nigronervosa and P. caladii, global pests of banana, Wolbachia was initially hypothesized to function as a co-obligate nutritional symbiont alongside the traditional obligate Buchnera. However, genomic analyses failed to support this role. Our sampling across numerous populations revealed that more than 80% of Pentalonia aphids carried an M-supergroup strain of Wolbachia (wPni). The lack of fixation further supports a facultative status for Wolbachia, while high infection frequencies in these entirely asexual aphids strongly suggest Wolbachia confers net fitness benefits. Finding no correlation between Wolbachia presence and food plant use, we challenged Wolbachia-infected aphids with common natural enemies. Bioassays revealed that Wolbachia conferred significant protection against a specialized fungal pathogen (Pandora neoaphidis) but not against generalist pathogens or parasitoids. Wolbachia also improved aphid fitness in the absence of enemy challenge. Thus, we identified the first clear benefits for aphid-associated Wolbachia and M-supergroup strains specifically. Aphid-Wolbachia systems provide unique opportunities to merge key models of symbiosis to better understand infection dynamics and mechanisms underpinning symbiont-mediated phenotypes.

中文翻译：

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工具箱中的另一个工具：蚜虫特异性沃尔巴克氏体可抵御真菌病原体


蚜虫拥有 9 个常见的兼性共生体，大多数介导一种或多种生态相互作用。Wolbachia pipientis 在其他节肢动物中得到了充分研究，但在蚜虫中的特征仍然很差。在全球香蕉害虫 Pentalonia nigronervosa 和 P. caladii 中，沃尔巴克氏体最初被假设与传统专性 Buchnera 一起作为共专性营养共生体发挥作用。然而，基因组分析未能支持这一作用。我们对众多种群的抽样显示，超过 80% 的五角蚜蚜携带沃尔巴克氏体 （wPni） 的 M 超群菌株。缺乏固定进一步支持 Wolbachia 的兼性状态，而这些完全无性蚜虫的高感染频率强烈表明 Wolbachia 具有净健康益处。发现沃尔巴克氏体的存在与食用植物的使用之间没有相关性，我们用共同的天敌挑战了沃尔巴克氏体感染的蚜虫。生物测定显示，沃尔巴克氏体对一种特殊的真菌病原体 （Pandora neoaphidis） 具有显着保护作用，但对通用病原体或寄生虫没有保护作用。Wolbachia 还在没有敌人挑战的情况下改善了蚜虫的适应性。因此，我们确定了蚜虫相关沃尔巴克氏体和 M 超群菌株的第一个明确益处。Aphid-Wolbachia 系统为合并共生的关键模型提供了独特的机会，以更好地了解支持共生体介导的表型的感染动力学和机制。