Plant volatiles play a major role in plant–insect interactions as defense compounds or attractants for insect herbivores. Recent studies have shown that endophytic fungi are also able to produce volatiles and this raises the question of whether these fungal volatiles influence plant–insect interactions. Here, we qualitatively investigated the volatiles released from 13 endophytic fungal species isolated from leaves of mature black poplar (Populus nigra) trees. The volatile blends of these endophytes grown on agar medium consist of typical fungal compounds, including aliphatic alcohols, ketones and esters, the aromatic alcohol 2-phenylethanol and various sesquiterpenes. Some of the compounds were previously reported as constituents of the poplar volatile blend. For one endophyte, a species of Cladosporium, we isolated and characterized two sesquiterpene synthases that can produce a number of mono- and sesquiterpenes like (E)-β-ocimene and (E)-β-caryophyllene, compounds that are dominant components of the herbivore-induced volatile bouquet of black poplar trees. As several of the fungus-derived volatiles like 2-phenylethanol, 3-methyl-1-butanol and the sesquiterpene (E)-β-caryophyllene, are known to play a role in direct and indirect plant defense, the emission of volatiles from endophytic microbial species should be considered in future studies investigating tree-insect interactions.

中文翻译：

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黑杨树叶定植内生真菌的挥发分排放和生物合成

植物挥发物作为昆虫食草动物的防御化合物或引诱剂，在植物-昆虫相互作用中发挥着重要作用。最近的研究表明，内生真菌也能够产生挥发物，这就提出了这些真菌挥发物是否影响植物-昆虫相互作用的问题。在这里，我们定性地研究了从成熟黑杨 ( Populus nigra ) 树的叶子中分离出的 13 种内生真菌物种释放的挥发物。在琼脂培养基上生长的这些内生菌的挥发性混合物由典型的真菌化合物组成，包括脂肪醇、酮和酯、芳香醇 2-苯基乙醇和各种倍半萜。一些化合物以前被报告为杨树挥发性混合物的成分。对于一种内生菌，一种枝孢菌，我们分离并表征了两种倍半萜合酶，它们可以产生许多单萜和倍半萜，如 ( E )-β-罗勒烯和 ( E )-β-石竹烯，这些化合物是草食动物引起的黑杨树挥发性花束。由于几种真菌衍生的挥发物，如 2-苯基乙醇、3-甲基-1-丁醇和倍半萜 ( E )-β-石竹烯，已知在直接和间接植物防御中发挥作用，内生植物的挥发物排放在未来调查树-昆虫相互作用的研究中应考虑微生物种类。