Resolving the infection process reveals striking differences in the contribution of environment, genetics and phylogeny to host-parasite interactions
Resolving the infection process reveals striking differences in the contribution of environment, genetics and phylogeny to host-parasite interactions
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DOI：
10.1186/1741-7007-9-11
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发表时间：
2011-02-22
期刊：
影响因子：
5.4
通讯作者：
Ebert, Dieter
中科院分区：
文献类型：
--
作者：
Duneau, David;Luijckx, Pepijn;Ebert, Dieter
背景：感染过程由一系列步骤组成，每个步骤对于宿主和寄生虫之间的相互作用至关重要。对宿主-寄生虫相互作用的研究很少考虑到这样一个事实，即不同的步骤可能受到不同因素的影响，因此可能对塑造共同进化做出不同的贡献。我们设计了一种新的方法，利用大型蚤（Daphnia magna）多枝巴斯德菌（Pasteuria ramosa）系统，这是一个罕见的协同进化的例子，为了解决感染的步骤和分析影响每个步骤的因素，我们使用透明的水蚤宿主和荧光标记的多枝巴斯德菌孢子，我们确定了一系列的感染步骤：寄生虫和宿主之间的相遇;寄生虫休眠孢子的激活;孢子附着于宿主;以及寄生虫在宿主内增殖。已表明，遭遇的机会取决于宿主基因型和环境。我们测试了遗传和环境因素在新描述的激活和附着步骤中的作用。不同基因型、性别和种属的疟原虫都能激活不同环境中所有供试的疟原虫克隆的内生孢子，这表明激活信号在植物遗传学上是保守的。我们接下来确定了寄生虫附着在宿主食管上的发生与宿主物种、性别和环境条件无关。相反，孢子活化，附着强烈依赖于宿主和寄生虫genotype.Conclusions的组合：我们的研究结果表明，不同的步骤是由不同的因素影响。不依赖宿主类型的孢子活化表明，这一步可以排除作为一个主要因素，水蚤巴斯德菌的共同进化。另一方面，我们表明，附件的步骤是至关重要的，该系统的显着的遗传特异性。我们认为，这一步可以解释宿主种群结构，并可能是共同进化周期背后的关键力量。我们讨论了如何不同的步骤可以解释不同方面的系统的协同进化动力学：属性的附件步骤，解释快速进化的感染性和属性的寄生虫增殖解释进化的毒力。我们的研究强调了解决感染过程的重要性，以便更好地了解宿主-寄生虫相互作用。
Background: Infection processes consist of a sequence of steps, each critical for the interaction between host and parasite. Studies of host-parasite interactions rarely take into account the fact that different steps might be influenced by different factors and might, therefore, make different contributions to shaping coevolution. We designed a new method using the Daphnia magna Pasteuria ramosa system, one of the rare examples where coevolution has been documented, in order to resolve the steps of the infection and analyse the factors that influence each of them.Results: Using the transparent Daphnia hosts and fluorescently-labelled spores of the bacterium P. ramosa, we identified a sequence of infection steps: encounter between parasite and host; activation of parasite dormant spores; attachment of spores to the host; and parasite proliferation inside the host. The chances of encounter had been shown to depend on host genotype and environment. We tested the role of genetic and environmental factors in the newly described activation and attachment steps. Hosts of different genotypes, gender and species were all able to activate endospores of all parasite clones tested in different environments; suggesting that the activation cue is phylogenetically conserved. We next established that parasite attachment occurs onto the host oesophagus independently of host species, gender and environmental conditions. In contrast to spore activation, attachment depended strongly on the combination of host and parasite genotypes.Conclusions: Our results show that different steps are influenced by different factors. Host-type-independent spore activation suggests that this step can be ruled out as a major factor in Daphnia-Pasteuria coevolution. On the other hand, we show that the attachment step is crucial for the pronounced genetic specificities of this system. We suggest that this one step can explain host population structure and could be a key force behind coevolutionary cycles. We discuss how different steps can explain different aspects of the coevolutionary dynamics of the system: the properties of the attachment step, explaining the rapid evolution of infectivity and the properties of later parasite proliferation explaining the evolution of virulence. Our study underlines the importance of resolving the infection process in order to better understand host-parasite interactions.