Abstract Although accumulating evidence indicates that tolerance is a plant defence strategy against pathogens as widespread as resistance, how plants evolve tolerance is poorly understood. Theory predicts that hosts will evolve to maximize tolerance or resistance, but not both. Remarkably, most experimental works failed in finding this trade-off. We tested the hypothesis that the evolution of tolerance to one virus is traded-off against tolerance to others, rather than against resistance and identified the associated mechanisms. To do so, we challenged eighteen Arabidopsis thaliana genotypes with Turnip mosaic virus (TuMV) and Cucumber mosaic virus (CMV). We characterized plant life-history trait modifications associated with reduced effects of TuMV and CMV on plant seed production (fecundity tolerance) and life period (mortality tolerance), both measured as a norm of reaction across viral loads (range tolerance). Also, we analysed resistance-tolerance and tolerance-tolerance trade-offs. Results indicate that tolerance to TuMV is associated with changes in the length of the pre-reproductive and reproductive periods, and tolerance to CMV with resource reallocation from growth to reproduction; and that tolerance to TuMV is traded-off against tolerance to CMV in a virulence-dependent manner. Thus, this work provides novel insights on the mechanisms of plant tolerance and highlights the importance of considering the combined effect of different pathogens to understand how plant defences evolve.

中文翻译：

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植物病毒相互作用中宿主对不同病原体的耐受性之间的权衡

摘要 尽管越来越多的证据表明耐受性是一种植物防御病原体的策略，与抗性一样普遍，但植物如何进化耐受性却知之甚少。理论预测宿主将进化以最大限度地提高耐受性或抵抗力，但不会两者兼而有之。值得注意的是，大多数实验工作都未能找到这种权衡。我们检验了对一种病毒的耐受性的进化与对其他病毒的耐受性而不是抗性进行权衡的假设，并确定了相关机制。为此，我们用芜菁花叶病毒 (TuMV) 和黄瓜花叶病毒 (CMV) 攻击了 18 个拟南芥基因型。我们表征了与 TuMV 和 CMV 对植物种子生产（生育耐受性）和生命周期（死亡率耐受性）的影响降低相关的植物生命史性状修改，两者都作为跨病毒载量的反应标准来衡量（范围耐受性）。此外，我们还分析了电阻耐受和耐受耐受的权衡。结果表明，对TuMV的耐受性与生殖前和生殖期长度的变化有关，对CMV的耐受性与资源从生长到生殖的重新分配有关；并且对 TuMV 的耐受性以毒力依赖的方式与对 CMV 的耐受性进行权衡。因此，这项工作提供了关于植物耐受机制的新见解，并强调了考虑不同病原体的联合作用以了解植物防御如何进化的重要性。结果表明，对TuMV的耐受性与生殖前和生殖期长度的变化有关，对CMV的耐受性与资源从生长到生殖的重新分配有关；并且对 TuMV 的耐受性以毒力依赖的方式与对 CMV 的耐受性进行权衡。因此，这项工作提供了关于植物耐受机制的新见解，并强调了考虑不同病原体的联合作用以了解植物防御如何进化的重要性。结果表明，对TuMV的耐受性与生殖前和生殖期长度的变化有关，对CMV的耐受性与资源从生长到生殖的重新分配有关；并且对 TuMV 的耐受性以毒力依赖的方式与对 CMV 的耐受性进行权衡。因此，这项工作提供了关于植物耐受机制的新见解，并强调了考虑不同病原体的联合作用以了解植物防御如何进化的重要性。