Parasite-host specificity: Experimental studies on the basis of parasite adaptation
Parasite-host specificity: Experimental studies on the basis of parasite adaptation
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DOI：
10.1111/j.0014-3820.2006.tb01079.x
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发表时间：
2006-01-01
期刊：
影响因子：
3.3
通讯作者：
Ebert, D
中科院分区：
文献类型：
--
作者：
Little, TJ;Watt, K;Ebert, D
寄生虫相互作用的特异性可以通过仅对寄生虫基因型的子集具有抗性的宿主基因型和对宿主基因型的子集具有感染性的寄生虫基因型来定义。它并不总是清楚，如果特异性是由基因型的相互作用，或者如果表型可塑性（有时称为驯化）发挥更大的作用。共同进化的结果主要取决于遗传相互作用的普遍性。我们使用细菌寄生虫多枝巴斯德菌及其甲壳类宿主大型蚤研究了特异性。首先，我们测试了在不同宿主基因型之间迅速转移的多枝假单胞菌品系的短期适应性。在这个时间尺度上的适应将证明表型可塑性对特异性的贡献。我们发现，无论最近的传代史如何，各品系的感染性都是稳定的，这表明在短期内感染结果是由遗传背景决定的。第二，我们研究了两个宿主克隆和两个寄生品系的长期进化。在该实验中，多枝假单胞菌品系有可能进化出对宿主基因型（克隆）的适应，在该宿主基因型（克隆）中，它们被连续传代，这使得我们能够测试特异性的遗传组分。在两个传代品系中出现了实质性差异：一个寄生虫品系在其生长的宿主克隆上获得了感染性，但在另一个宿主基因型上失去了感染性（该品系进化出特异性），而另一个寄生虫品系在两个宿主克隆上进化出更高的感染性。我们在连续传代实验中使用的两种宿主基因型进行杂交，并发现了导致抗性变异的宿主基因数量很少的证据。总之，我们的研究结果表明，多枝假单胞菌特异性是一个稳定的遗传性状，它可以迅速进化，它是由少数基因在宿主中控制。这些发现与细菌与其宿主之间快速持续的军备竞赛的想法一致。
Specificity in parasitic interactions can be defined by host genotypes that are resistant to only a subset of parasite genotypes and parasite genotypes that are infective on a subset of host genotypes. It is not always clear if specificity is determined by the genotypes of the interactors, or if phenotypic plasticity (sometimes called acclimation) plays a larger role. Coevolutionary outcomes critically depend on the pervasiveness of genetic interactions. We studied specificity using the bacterial parasite Pasteuria ramosa and its crustacean host Daphnia magna. First, we tested for short-term adaptation of P. ramosa lines that had been rapidly shifted among different host genotypes. Adaptation at this time-scale would demonstrate the contribution of phenotypic plasticity to specificity. We found that infectivity was stable across lines irrespective of recent passage history, indicating that in the short term infection outcomes are fixed by genetic backgrounds. Second, we studied longer-term evolution with two host clones and two parasite lines. In this experiment, P. ramosa lines had the possibility to evolve adaptations to the host genotype (clone) in which they were serially passaged, which allowed us to test for a genetic component to specificity. Substantial differences arose in the two passaged lines: one parasite line gained infectivity on the host clone it was grown on, but it lost infectivity on the other host genotype (this line evolved specificity), while the other parasite line evolved higher infectivity on both host clones. We crossed the two host genotypes used in the serial passage experiment and found evidence that the number of host genes that underlies resistance variation is small. In sum, our results show that P. ramosa specificity is a stably inherited trait, it can evolve rapidly, and it is controlled by few genes in the host. These findings are consistent with the idea of a rapid, ongoing arms race between the bacterium and its host.