Plants possess a sophisticated hormone-signaling system, which includes salicylic acid (SA) and jasmonic acid (JA), to defend themselves from herbivores. In addition, this immune system is modulated by nonpathogenic microbes that live asymptomatically within intercellular spaces of host grasses. We investigated the resistance triggered by defense hormones, and that provided by endophyte Epichloë gansuensis against aphid Rhopalosiphum padi, and how the endophyte regulates this tripartite interaction. We detected that endophyte-induced plant tolerance to the aphid feeding and exogenous SA increased plant shoot biomass, root biomass, plant length, and chlorophyll content. Endophyte colonization induces the WRKY54 factor that overrides negative effects on plant growth and possibly suppresses SA accumulation. In addition, the endophyte promotes a level of JA that is antagonistic to the SA pathway. By disabling the SA mechanism for herbivore-mediated plant growth inhibition, the endophyte induces plant tolerance to herbivory.

植物拥有复杂的激素信号系统，其中包括水杨酸 (SA) 和茉莉酸 (JA)，以保护自己免受食草动物的侵害。此外，这种免疫系统受到无症状生活在宿主草细胞间隙内的非病原微生物的调节。我们研究了防御激素引发的抗性，以及内生菌Epichloë gansuensis对蚜虫Rhopalosiphum padi提供的抗性，以及内生菌如何调节这种三方相互作用。我们检测到内生菌诱导的植物对蚜虫取食和外源 SA 的耐受性增加了植物地上部生物量、根生物量、植物长度和叶绿素含量。内生菌定植诱导 WRKY54 因子，该因子可以抵消对植物生长的负面影响，并可能抑制 SA 积累。此外，内生菌促进了与 SA 途径拮抗的 JA 水平。通过禁用草食动物介导的植物生长抑制的 SA 机制，内生菌诱导植物对食草动物的耐受性。