Grapevine trunk diseases (GTDs) affect grape production and reduce vineyard longevity worldwide. Since the causative fungi also occur in asymptomatic trunks, we address disease outbreak in terms of altered chemical communication between host and endophyte. Here, we identified four chemically similar secondary metabolites secreted by the GTD-associated fungus Eutypa lata to analyse their modes of action in a grapevine cell culture of Vitis rupestris, where microtubules were tagged by GFP. Treatment with the metabolite eutypine activated defence responses, evident from extracellular alkalinisation and induction of defence genes. Eutypinol, instead, eliminated microtubules, in contrast to the other three compounds. Furthermore, we evaluated the effect of four corresponding chemical analogues of these compounds, sharing the phenolic but lacking the alkyne moiety. These analogues were able to induce similar defence responses in V. rupestris cells, albeit at reduced amplitude. Since closely related moieties differing only in details of the side groups at the phenolic ring differ significantly with respect to the response of the host cell, we propose that these fungal compounds act through a specific binding site at the membrane of grapevine cells. We corroborate this specificity by combination experiments, where the eutypine and the eutypinol analogues behave competitively with respect to the elicited responses. In summary, Eutypa lata secretes compounds that elicit host defence in a specific manner by interfering with early events of immunity signalling. This supports the notion that a real understanding of GTDs has to address inter-organismic chemical communication.

中文翻译：

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Eutypa lata 的真菌诱导剂 eutypine 通过其酚侧链激活基础免疫

葡萄树干病害 (GTDs) 影响葡萄生产并缩短全球葡萄园的寿命。由于致病真菌也出现在无症状的树干中，我们通过改变宿主和内生菌之间的化学通讯来解决疾病爆发。在这里，我们鉴定了 GTD 相关真菌 Eutypa lata 分泌的四种化学相似的次级代谢物，以分析它们在葡萄树细胞培养物中的作用模式，其中微管被 GFP 标记。用代谢物eutypine治疗激活防御反应，从细胞外碱化和防御基因的诱导中可以看出。相反，与其他三种化合物相比，Eutypinol 消除了微管。此外，我们评估了这些化合物的四种相应化学类似物的作用，共享酚类但缺少炔烃部分。这些类似物能够在 V. rupestris 细胞中诱导类似的防御反应，尽管幅度降低。由于密切相关的部分仅在酚环侧基的细节上有所不同，因此在宿主细胞的反应方面存在显着差异，我们建议这些真菌化合物通过葡萄树细胞膜上的特定结合位点起作用。我们通过组合实验证实了这种特异性，其中 eutypine 和 eutypinol 类似物在引发反应方面表现出竞争性。总之，Eutypa lata 分泌的化合物通过干扰免疫信号传导的早期事件以特定方式引发宿主防御。