Data from: Fatal attraction of non-vector impairs fitness of manipulating plant virus

1. Host manipulation refers to the expression of a host phenotype that is partly under the genetic control of a parasite. This phenomenon can enhance parasite transmission rates and is responsible for biological marvels such as 'Zombie-ants' and the 'fatal attraction' of Toxoplasma-infected rodents to their feline predators. Such host manipulation has evolved in all major phylogenetic lineages of parasites and is assumed to enhance the fitness of the parasite.
2. However, the capacity to manipulate is not ubiquitous; that is, many clades of parasites comprise manipulating and non-manipulating species. This pattern leads to the prediction of costs that select against the evolution of manipulation, but this has been difficult to show empirically.
3. In the present study, we used a tripartitate system consisting of chili (Capsicum annuum) plants infected with Pepper golden mosaic virus and colonized by non-vector whiteflies (Trialeurodes vaporariorum), to study the effects on viral load when a non-vector herbivore feeds on the infected plants.
4. We observed that virus-infected plants emitted odours that attracted adult whiteflies, contained three times more amino acids in the phloem than mock-inoculated controls and supported higher whitefly reproduction as compared to controls. However, viral load decreased almost 100-fold in whitefly-carrying plants, which was associated with a depletion of phloem amino acids.
5. Synthesis. We show that a plant virus can suffer from a reduced within-host reproduction rate when virus-induced alterations of the plant cause a 'fatal attraction' of a non-vector insect that exploits the altered plant phenotype at its own benefits. The resulting fitness costs might represent a force that can select against the evolution of host manipulation by parasites.

1. 宿主操控（Host manipulation）指宿主表型的表达部分受寄生物的遗传调控。该现象可提升寄生物的传播效率，亦是诸多生物奇观的成因，例如"僵尸蚂蚁"，以及弓形虫（Toxoplasma）感染的啮齿动物对其猫科捕食者的"致命吸引力"。此类宿主操控已在所有主要的寄生物系统发育谱系中演化，并被认为可提升寄生物的适合度（fitness）。
2. 然而，宿主操控能力并非普遍存在：诸多寄生物演化支同时涵盖具备操控能力与不具备操控能力的物种。这一模式催生了"宿主操控的演化存在适应性代价，进而对其演化产生负选择"的预测，但该预测难以通过实证研究验证。
3. 本研究构建了一套三方实验体系：以感染辣椒金色花叶病毒（Pepper golden mosaic virus）且被非介体型温室白粉虱（Trialeurodes vaporariorum）定殖的普通辣椒（Capsicum annuum）为研究对象，探究非介体植食性昆虫取食感染植株后对病毒载量（viral load）的影响。
4. 研究发现，病毒感染植株释放的气味可吸引成虫期白粉虱；其韧皮部（phloem）中的氨基酸含量为空白接种（mock-inoculated）对照组的3倍，且相较于对照组，更利于白粉虱繁殖。但携带白粉虱的植株中，病毒载量几乎下降了100倍，该现象与韧皮部氨基酸的耗竭密切相关。
5. 综合分析：本研究证实，当病毒诱导的植物表型改变引发非介体昆虫产生"致命吸引力"，且该昆虫借此改变的植物表型谋取自身利益时，植物病毒的宿主体内繁殖率会出现下降。由此产生的适应性代价，或可成为抑制寄生物演化出宿主操控能力的选择压力。