Aphid-encoded variability in susceptibility to a parasitoid

Background: Many animals exhibit variation in resistance to specific natural enemies. Such variation may be encoded in their genomes or derived from infection with protective symbionts. The pea aphid, Acyrthosiphon pisum, for example, exhibits tremendous variation in susceptibility to a common natural enemy, the parasitic wasp Aphidius ervi. Pea aphids are often infected with the heritable bacterial symbiont, Hamiltonella defensa, which confers partial to complete resistance against this parasitoid depending on bacterial strain and associated bacteriophages. That previous studies found that pea aphids without H. defensa (or other symbionts) were generally susceptible to parasitism, together with observations of a limited encapsulation response, suggested that pea aphids largely rely on infection with H. defensa for protection against parasitoids. However, the limited number of uninfected clones previously examined, and our recent report of two symbiont-free resistant clones, led us to ...研究背景：诸多动物对特定天敌的抗性存在显著变异。此类变异既可由宿主基因组编码决定，也可因感染保护性共生菌而产生。以豌豆蚜（Acyrthosiphon pisum）为例，其对常见天敌寄生蜂（Aphidius ervi）的易感性差异极大。豌豆蚜常携带可垂直传播的细菌共生菌汉密尔顿菌（Hamiltonella defensa），该共生菌可根据自身菌株及伴随的噬菌体类型，为宿主提供针对该寄生蜂的部分至完全抗性。既往研究显示，未感染汉密尔顿菌（H. defensa）或其他共生菌的豌豆蚜通常易被寄生，加之此前观察到的有限包囊化免疫响应，提示豌豆蚜主要依赖汉密尔顿菌感染来获得针对寄生蜂的保护。然而，既往研究中检测的未感染克隆株数量有限，且我们近期报道了两株无共生菌的抗性克隆，这促使我们……