Although the role of fungal alkaloids in protecting grasses associated with Epichloë fungal endophytes has been extensively documented, the effects of the symbiont on the host plant’s immune responses have received little attention. We propose that, in addition to producing protective alkaloids, endophytes enhance plant immunity against chewing insects by promoting endogenous defense responses mediated by the jasmonic acid (JA) pathway. We advance a model that integrates this dual effect of endophytes on plant defenses and test its predictions by means of a standard meta-analysis. This analysis supports a role of Epichloë endophytes in boosting JA-mediated plant defenses. We discuss the ecological scenarios where this effect of endophytes on plant defenses would be most beneficial for increasing plant fitness.

尽管真菌生物碱在保护与Epichloë真菌内生菌相关的草中的作用已得到广泛的文献记载，但共生体对宿主植物免疫反应的影响却鲜为人知。我们建议，除产生保护性生物碱外，内生菌还可以通过促进茉莉酸（JA）途径介导的内源性防御反应来增强植物对咀嚼昆虫的免疫力。我们提出了一个模型，该模型整合了内生菌对植物防御的双重作用，并通过标准的荟萃分析测试了其预测。该分析支持了埃皮克洛的角色内生菌增强JA介导的植物防御能力。我们讨论了生态场景，其中内生菌对植物防御的影响将最有利于提高植物适应性。