The long-term maintenance of a resistance polymorphism through diffuse interactions.
The long-term maintenance of a resistance polymorphism through diffuse interactions.
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DOI：
10.1038/nature13439
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发表时间：
2014-08-28
期刊：
影响因子：
64.8
通讯作者：
Bergelson J
中科院分区：
文献类型：
--
作者：
Karasov TL;Kniskern JM;Gao L;DeYoung BJ;Ding J;Dubiella U;Lastra RO;Nallu S;Roux F;Innes RW;Barrett LG;Hudson RR;Bergelson J
植物抗病基因是植物防御病原体的重要组成部分。虽然R基因在农业环境中通常不能提供持久的抗性，但它们在自然界中经常作为长寿的平衡多态性而存在。标准理论解释了这种多态性的维持是通过在一个紧密共同进化的宿主-病原体对中的抗性和毒力的成本和收益的平衡来实现的。然而，许多植物-病原体相互作用缺乏这种特异性。是否，以及如何，平衡的多态性保持在广泛相互作用的物种是未知的。在这里，我们确定了拟南芥及其兼性植物病原菌，假单胞菌的自然相互作用的R基因和效应对。由R基因RPS 5编码的蛋白质识别AvrPphB同源物（AvrPphB 2），并表现出平衡的多态性，该多态性已维持了200万年以上（参考文献）。与古老的平衡多态性的存在相一致，当植物感染携带avrPphB 2的P. lingae时，R基因赋予益处，但在没有感染的情况下也产生很大的成本。RPS 5等位基因在全球种群中保持在中等频率，表明抗性的普遍选择。然而，携带avrPphB的P. dingae的存在可能不足以解释RPS 5多态性。首先，avrPphB同源物在A. thaliana.第二，AvrPphB仅在很少情况下赋予P. erichingae对A. thaliana.相反，我们发现证据表明，RPS 5的选择涉及多个非同源效应子和多个病原体物种。这些结果和相关模型表明，A.拟南芥的基因组可能不是通过涉及单个共同进化的R基因和效应子对的紧密耦合相互作用来维持的。更有可能的是，稳定的多态性是通过复杂和扩散的社区范围内的相互作用来维持的。
Plant resistance (R) genes are a crucial component in plant defence against pathogens. Although R genes often fail to provide durable resistance in an agricultural context, they frequently persist as long-lived balanced polymorphisms in nature. Standard theory explains the maintenance of such polymorphisms through a balance of the costs and benefits of resistance and virulence in a tightly coevolving host–pathogen pair. However, many plant–pathogen interactions lack such specificity. Whether, and how, balanced polymorphisms are maintained in diffusely interacting species is unknown. Here we identify anaturally interacting R gene and effector pair in Arabidopsis thaliana and its facultative plant pathogen, Pseudomonas syringae. The protein encoded by the R gene RPS5 recognizes an AvrPphB homologue (AvrPphB2) and exhibits a balanced polymorphism that has been maintained for over 2 million years (ref.). Consistent with the presence of an ancient balanced polymorphism, the R gene confers a benefit when plants are infected with P. syringae carrying avrPphB2 but also incurs a large cost in the absence of infection. RPS5 alleles are maintained at intermediate frequencies in populations globally, suggesting ubiquitous selection for resistance. However, the presence of P. syringae carrying avrPphB is probably insufficient to explain the RPS5 polymorphism. First, avrPphB homologues occur at very low frequencies in P. syringae populations on A. thaliana. Second, AvrPphB only rarely confers a virulence benefit to P. syringae on A. thaliana. Instead, we find evidence that selection for RPS5 involves multiple non-homologous effectors and multiple pathogen species. These results and an associated model suggest that the R gene polymorphism in A. thaliana may not be maintained through a tightly coupled interaction involving a single coevolved R gene and effector pair. More likely, the stable polymorphism is maintained through complex and diffuse community-wide interactions.