Data from: An alternative pathway to eusociality: exploring the molecular and functional basis of fortress defense

Some animals express a form of eusociality known as 'fortress defense', in which defense rather than brood care is the primary social act. Aphids are small plant-feeding insects, but like termites, some species express division of labor and castes of aggressive juvenile 'soldiers'. What is the functional basis of fortress defense eusociality in aphids? Previous work showed that the acquisition of venoms might be a key innovation in aphid social evolution. We show that the lethality of aphid soldiers derives in part from the induction of exaggerated immune responses in insects they attack. Comparisons between closely-related social and non-social species identified a number of secreted effector molecules that are candidates for immune modulation, including a convergently-recruited protease described in unrelated aphid species with venom-like functions. These results suggest that aphids are capable of antagonizing conserved features of the insect immune response, and provide new insights into the mechanisms underlying the evolution of fortress defense eusociality in aphids.

部分动物演化出一种被称为"堡垒防御型"（fortress defense）的真社会性（eusociality）组织形式，其核心社会行为以防御而非育幼为主。蚜虫为小型植食性昆虫，与白蚁类似，部分蚜虫物种展现出劳动分工与品级分化，存在具有攻击性的幼态"士兵"品级。蚜虫的堡垒防御型真社会性，其功能基础究竟为何？既往研究表明，毒液（venoms）的获得或许是蚜虫社会演化过程中的一项关键创新。本研究发现，蚜虫兵蚁的致死性，部分源于其诱导了被攻击昆虫的过度免疫应答。通过对亲缘关系相近的社会性与非社会性蚜虫物种开展比较分析，研究团队鉴定出多种可作为免疫调控候选因子的分泌型效应分子（secreted effector molecules），其中包括在无亲缘关系的蚜虫物种中被发现、具有毒液样功能的趋同招募蛋白酶（convergently-recruited protease）。本研究结果表明，蚜虫能够拮抗昆虫免疫应答的保守特征，同时为阐释蚜虫堡垒防御型真社会性的演化机制提供了全新视角。