The ectomycorrhizospheric habitat contains a diverse pool of organisms, including the host plant, mycorrhizal fungi, and other rhizospheric microorganisms. Different signaling molecules may influence the ectomycorrhizal symbiosis. Here, we investigated the potential of the basidiomycete Tricholoma vaccinum to produce communication molecules for the interaction with its coniferous host, Norway spruce (Picea abies). We focused on the production of volatile organic compounds and phytohormones in axenic T. vaccinum cultures, identified the potential biosynthesis genes, and investigated their expression by RNA-Seq analyses. T. vaccinum released volatiles not usually associated with fungi, like limonene and β-barbatene, and geosmin. Using stable isotope labeling, the biosynthesis of geosmin was elucidated. The geosmin biosynthesis gene ges1 of T. vaccinum was identified, and up-regulation was scored during mycorrhiza, while a different regulation was seen with mycorrhizosphere bacteria. The fungus also released the volatile phytohormone ethylene and excreted salicylic and abscisic acid as well as jasmonates into the medium. The tree excreted the auxin, indole-3-acetic acid, and its biosynthesis intermediate, indole-3-acetamide, as well as salicylic acid with its root exudates. These compounds could be shown for the first time in exudates as well as in soil of a natural ectomycorrhizospheric habitat. The effects of phytohormones present in the mycorrhizosphere on hyphal branching of T. vaccinum were assessed. Salicylic and abscisic acid changed hyphal branching in a concentration-dependent manner. Since extensive branching is important for mycorrhiza establishment, a well-balanced level of mycorrhizospheric phytohormones is necessary. The regulation thus can be expected to contribute to an interkingdom language.

外生菌根生境包含多种生物，包括宿主植物，菌根真菌和其他根际微生物。不同的信号分子可能会影响外生菌根共生。在这里，我们调查了担子菌Tricholoma vaccinum产生与其与其具针叶寄主挪威云杉（Picea abies）相互作用的通讯分子的潜力。我们着重研究了在无性T.vaccinum培养物中挥发性有机化合物和植物激素的产生，鉴定了潜在的生物合成基因，并通过RNA-Seq分析研究了它们的表达。痘苗释放通常不与真菌相关的挥发物，例如柠檬烯和β-巴巴烯，以及土臭味素。使用稳定的同位素标记，阐明了土臭素的生物合成。牛痘菌的土臭素生物合成基因ges1 。菌根被鉴定出来，并在菌根期间上调，而菌根根细菌则有不同的调节。真菌还释放出挥发性植物激素乙烯，并向培养基中排出水杨酸和脱落酸以及茉莉酸盐。该树排出了生长素，吲哚-3-乙酸及其生物合成中间体吲哚-3-乙酰胺以及水杨酸及其根系分泌物。这些化合物可在渗出液以及天然外生菌根生境的土壤中首次显示。菌根根中存在的植物激素对牛痘菌菌丝分支的影响被评估。水杨酸和脱落酸以浓度依赖性方式改变菌丝分支。由于广泛的分支对于菌根的建立很重要，因此，菌根根植物激素的平衡水平是必要的。因此，可以预期该规则有助于交流语言。