What doesn’t kill you makes you stronger: The burdens and benefits of toxin sequestration in a milkweed aphid
What doesn’t kill you makes you stronger: The burdens and benefits of toxin sequestration in a milkweed aphid
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杀不死你的会让你变得更强大：马利筋蚜虫隔离毒素的负担和好处
DOI：
10.1111/1365-2435.13144
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发表时间：
2018
影响因子：
5.2
通讯作者：
Biere, ed., Arjen
中科院分区：
文献类型：
--
作者：
Züst, Tobias;Mou, Sophie;Agrawal, Anurag A.;Biere, ed., Arjen
专门的食草昆虫通常会利用植物防御来抵御捕食者，但对隔离的成本，收益和机制知之甚少。我们量化了专家蚜虫Aphis nerii在四种密切相关的马利筋上饲养时对有毒Cardenolides的隔离（Asclepias）种与>20倍的变化，在Cardenoprene含量，在存在或不存在通性瓢虫捕食者的情况下，非极性植物强心内酯的浓度增加蚜虫的螯合量。植物中的高浓度损害了蚜虫种群的增长，但也减少了捕食者的自上而下的影响。利用强心内酯的靶点（动物Na+/K+-ATP酶）对蚜虫体内总强心内酯进行的体外酶促测定显示，隔离的强心内酯亚组比叶子中的强心内酯毒性更大。所有蚜虫都积累了两种在其宿主植物中不存在的强心内酯，即使在叶子中强心内酯浓度非常低的植物上也是如此。夹竹桃对强毒强心甾内酯的螯合作用包括被动的、浓度依赖性的从寄主植物的吸收，以及可能更主动的植物强心甾内酯的修饰和富集机制。因此，寄主植物中毒素的浓度不仅决定了对蚜虫生长和性能的负面影响，而且决定了毒素被螯合用于蚜虫防御的难易程度和效率。使得植物毒素的成本和收益对植物和食草动物都高度依赖于环境。因此，植物毒素的变异对于植物-昆虫相互作用的共同进化至关重要，特别是在捕食者压力可变的环境中。
Specialized insect herbivores commonly co‐opt plant defences for protection against predators, but the costs, benefits and mechanisms of sequestration are poorly understood.We quantified sequestration of toxic cardenolides by the specialist aphidAphis neriiwhen reared on four closely related milkweed (Asclepias) species with >20‐fold variation in cardenolide content, and in the presence or absence of generalist ladybug predators.Increasing concentrations of apolar plant cardenolides increased sequestered amounts in aphids. High concentrations in plants impaired aphid population growth, but also reduced the top‐down effects of predators. An in vitro enzymatic assay of total cardenolides in aphid bodies using the cardenolides’ target (animal Na+/K+‐ATPase) revealed that the subset of sequestered cardenolides is disproportionally more toxic than cardenolides in leaves.All aphids accumulated two cardenolides not present in their host plant, even on plants with very low foliar cardenolide concentrations. Sequestration of potent cardenolides byA. neriithus involves passive, concentration‐dependent uptake from the host plant, as well as a presumably more active mechanism of modification and up‐concentration of plant cardenolides.The concentration of toxins in the host plant thus not only determines the negative impacts on growth and performance of an aphid, but also the ease and efficiency by which toxins are sequestered for the aphid’s defence, making the costs and benefits of plant toxins highly context‐dependent for both the plant and the herbivore. Therefore, variation in plant toxins is of central importance for co‐evolutionary plant–insect interactions, particularly in environments with variable predator pressure.A plain language summary is available for this article.
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