Plants comprise many asymptomatic fungal endophytes with potential roles of plant protection against abiotic and biotic stresses. Endophytes communicate with their host plant, with other endophytes and with invading pathogens but their language remains largely unknown. This work aims at understanding the chemical communication and physiological interactions between the fungal endophyte Paraconiothyrium variabile and the phytopathogen Fusarium oxysporum. Oxylipins, common means of communication, such as 13-hydroperoxy-9,11-octadecadienoic acid (13-HPODE), had been shown in our earlier studies to be overproduced during dual culture between the two fungal antagonists. On the other hand, the mycotoxin beauvericin was reduced in the interaction zone. The present work addresses the mechanisms underlying these changes. Hydroperoxy oxylipins are produced by lipoxygenases and P. variabile contains two lipoxygenase genes (pvlox1 and pvlox2), whereas pvlox2, but not pvlox1, is specifically up regulated during the interaction and none of the F. oxysporum lox genes vary. Heterologous expression of pvlox2 in yeast shows that the corresponding enzyme PVLOX2 produces 13-HPODE and, therefore, is most likely at the origin of the overproduced 13-HPODE during the interaction. Compellingly, beauvericin synthase gene beas expression is induced and beauvericin amounts increase in F. oxysporum mycelium when in contact with P. variabile. 13-HPODE, however, does not affect beas gene expression. Beauvericin, indeed, inhibits P. variabile growth, which counteracts and biotransforms the mycotoxin leading to reduced amounts in the interaction zone which allows further expansion of the endophyte. In order to study the interaction between the protagonists in planta, we set up an in vitro tripartite interaction assay, including the model plant Arabidopsis thaliana. F. oxysporum rapidly kills A. thaliana plants, whereas P. variabile provides up to 85% reduction of plant death if present before pathogen attack. Future studies will shed light on the protection mechanisms and the role of oxylipins and beauvericin degradation herein with the long-term aim of using endophytes in plant protection.

中文翻译：

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内生菌 Paraconiothyrium v​​ariabile 和植物病原体尖孢镰刀菌之间的分子串扰 - 在相互作用过程中调节脂氧化酶活性和白僵菌素的产生。

植物包含许多无症状的内生真菌，具有植物保护抵抗非生物和生物胁迫的潜在作用。内生菌与寄主植物、其他内生菌和入侵的病原体进行交流，但它们的语言在很大程度上仍然未知。这项工作旨在了解真菌内生菌 Paraconiothyrium v​​ariabile 和植物病原体尖孢镰刀菌之间的化学通讯和生理相互作用。Oxylipins 是一种常见的交流方式，例如 13-氢过氧-9,11-十八碳二烯酸 (13-HPODE)，在我们早期的研究中已被证明在两种真菌拮抗剂的双重培养过程中会过度产生。另一方面，在相互作用区减少了霉菌毒素白僵菌素。目前的工作解决了这些变化背后的机制。氢过氧 oxylipins 由脂氧合酶产生，P. variabile 包含两个脂氧合酶基因（pvlox1 和 pvlox2），而 pvlox2，但不是 pvlox1，在相互作用过程中被特异性上调，并且 F. oxysporum lox 基因都没有变化。pvlox2 在酵母中的异源表达表明相应的酶 PVLOX2 产生 13-HPODE，因此很可能是相互作用过程中过量产生的 13-HPODE 的起源。令人信服的是，当与 P.variabile 接触时，尖孢镰刀菌菌丝体中的白僵菌素合成酶基因 beas 表达被诱导，并且白僵菌素的量增加。然而，13-HPODE 不影响 beas 基因表达。白僵菌素确实抑制了变异疟原虫的生长，它抵消和生物转化真菌毒素，导致相互作用区中的数量减少，从而允许内生菌进一步扩展。为了研究植物中的主角之间的相互作用，我们建立了体外三方相互作用试验，包括模型植物拟南芥。F. oxysporum 迅速杀死拟南芥植物，而 P. variabile 如果在病原体攻击之前存在，则可将植物死亡减少多达 85%。未来的研究将阐明保护机制以及 oxylipins 和白僵菌素降解的作用，长期目标是在植物保护中使用内生菌。oxysporum 迅速杀死拟南芥植物，而 P. variabile 如果在病原体攻击之前存在，则可将植物死亡减少多达 85%。未来的研究将阐明保护机制以及 oxylipins 和白僵菌素降解的作用，长期目标是在植物保护中使用内生菌。oxysporum 迅速杀死拟南芥植物，而 P. variabile 如果在病原体攻击之前存在，则可将植物死亡减少多达 85%。未来的研究将阐明保护机制以及 oxylipins 和白僵菌素降解的作用，长期目标是在植物保护中使用内生菌。