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. 宿主操纵（Host manipulation）指宿主表型的表达部分受寄生生物的遗传调控。该现象可提升寄生生物的传播效率，亦是诸多生物奇观的成因，例如“僵尸蚂蚁”，以及感染弓形虫（Toxoplasma）的啮齿动物对猫科捕食者产生的“致命吸引”。此类宿主操纵在所有主要的寄生生物系统发育谱系中均有演化，且被认为可提升寄生生物的适合度。
2. 然而，宿主操纵能力并非普遍存在；也就是说，诸多寄生生物演化支中同时包含具有操纵能力和不具有操纵能力的物种。这一现象预示着存在不利于宿主操纵演化的选择压力，但该推论难以通过实验验证。
3. 本研究采用三方互作系统：以感染辣椒金色花叶病毒（Pepper golden mosaic virus）且被非介体温室白粉虱（Trialeurodes vaporariorum）定殖的普通辣椒（Capsicum annuum）为研究材料，探究非介体植食性昆虫取食该侵染植株后对病毒载量的影响。
4. 研究结果显示，病毒侵染的植株会释放可吸引成虫烟粉虱的气味，其韧皮部的氨基酸含量为模拟接种对照组的3倍，且相较于对照组更能支持烟粉虱的繁殖。然而，携带烟粉虱的植株内病毒载量下降了近100倍，该现象与韧皮部氨基酸含量的耗竭密切相关。
5. 综合分析。本研究表明，当病毒诱导的植株改变使得非介体昆虫产生“致命吸引”，并利用该改变后的植株表型获取自身收益时，植物病毒的宿主体内繁殖速率会出现下降。由此产生的适合度成本，或可构成一种抑制寄生生物演化出宿主操纵能力的选择力量。