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：

---

Hordedane 二萜类植物抗毒素限制禾谷镰刀菌感染，但增强 Bipolaris sorokiniana 在大麦根系的定植


植物免疫是一个多层次的过程，包括识别病原体的模式或效应子以引发防御反应。这些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了大麦根与真菌病原体 （） 和 （） 之间的相互作用。我们确定 hordedanes，一组以前未描述的具有抗菌特性的拉布丹相关二萜类化合物，是这些相互作用的关键参与者。大麦根被 600 kb 基因簇感染并引发 hordedane 合成。酵母中生物合成途径的异源重建并产生了几种麦粒烯，包括功能装饰最丰富的产品之一 19-β-羟基-麦麦三烯酸 （19-OH-HTA）。该簇的二萜合酶基因中的大麦突变体无法产生大麦，但出乎意料地显示出定植减少。相比之下，大麦和小麦的另一种真菌病原体的定植在完全缺乏 hordedanes 的突变体中高出 4 倍。因此，19-OH-HTA 可增强 的发芽和生长，而抑制其他病原真菌，包括 。显微镜和转录组学数据分析表明，麦粒龙会延迟 的坏死营养期。综上所述，这些结果表明，适应性病原体（例如）可以破坏植物代谢防御以促进根定植。