Plant immunity is a multilayered process that includes recognition of patterns or effectors from pathogens to elicit defense responses. These include the induction of a cocktail of defense metabolites that typically restrict pathogen virulence. Here, we investigate the interaction between barley roots and the fungal pathogens () and () at the metabolite level. We identify hordedanes, a previously undescribed set of labdane-related diterpenoids with antimicrobial properties, as critical players in these interactions. Infection of barley roots by and elicits hordedane synthesis from a 600-kb gene cluster. Heterologous reconstruction of the biosynthesis pathway in yeast and produced several hordedanes, including one of the most functionally decorated products 19-β-hydroxy-hordetrienoic acid (19-OH-HTA). Barley mutants in the diterpene synthase genes of this cluster are unable to produce hordedanes but, unexpectedly, show reduced colonization. By contrast, colonization by , another fungal pathogen of barley and wheat, is 4-fold higher in the mutants completely lacking hordedanes. Accordingly, 19-OH-HTA enhances both germination and growth of , whereas it inhibits other pathogenic fungi, including . Analysis of microscopy and transcriptomics data suggest that hordedanes delay the necrotrophic phase of . Taken together, these results show that adapted pathogens such as can subvert plant metabolic defenses to facilitate root colonization.

中文翻译：

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大麦烷二萜类植物抗毒素可限制禾谷镰刀菌感染，但可增强大麦根部的 Bipolaris sorokiniana 定植


植物免疫是一个多层过程，包括识别病原体的模式或效应器以引发防御反应。其中包括诱导通常限制病原体毒力的防御代谢物混合物。在这里，我们在代谢物水平上研究大麦根与真菌病原体 () 和 () 之间的相互作用。我们确定大麦烷是一组先前未描述的具有抗菌特性的与拉丹丹相关的二萜类化合物，是这些相互作用中的关键参与者。通过 600 kb 基因簇感染大麦根并引发大麦烷合成。异源重建酵母中的生物合成途径并产生了几种大麦烷，包括功能性最强的修饰产物之一19-β-羟基-大麦三烯酸（19-OH-HTA）。该簇二萜合酶基因中的大麦突变体无法产生大麦烷，但出乎意料的是，其定殖减少。相比之下，大麦和小麦的另一种真菌病原体 的定殖在完全缺乏大麦烷的突变体中高出 4 倍。因此，19-OH-HTA 可以促进 的发芽和生长，同时抑制其他病原真菌，包括 。显微镜和转录组学数据的分析表明，大麦烷延迟了 的坏死营养期。总而言之，这些结果表明，适应的病原体可以破坏植物的代谢防御，以促进根部定植。