Functional role of phyllosphere fungi in litter decomposition in response to land use

欧洲山毛榉是中欧最重要、研究最深入的树种之一。像所有的树木一样，它拥有种类繁多的内生真菌。然而，由于环境因素的多样性，内生真菌的群落结构目前还知之甚少。此外，内生真菌在生态系统过程中的功能多样性和生态作用，如碳和氮循环，几乎是显而易见的。然而，最近的研究表明，相当一部分内生群落也存在于凋落物中，并具有降解枯死植物物质的酶能力。在这里，我们致力于揭示山毛榉内生真菌的生物地理格局、季节动态和对土地利用的依赖性，它们在凋落物退化中的作用，以及在两种生境(活叶和腐叶)上定居的真菌的生活周期。特别是，我们测试了这一假设的含义，即通过促进具有增强防御能力的树木个体，营林栽培有利于建立宿主或生境适应的内生真菌，这种真菌比适应程度较低的真菌更有效地分解落叶，从而对营养循环做出更大的贡献。生物多样性探索实验室的设计为解开这种复杂的联系提供了宝贵的先决条件。除了来自合作小组的现有环境背景数据外，还将持续监测叶片生理和生物化学，为最终讨论评估的分子数据提供基础。DNA和RNA衍生标记的下一代测序(NGS)将针对探索性设计所代表的区域、环境和土地利用梯度，评估内生和凋落物降解真菌群落结构和活动的季节动态。落叶层中的转录酶也将通过NGS进行分析，以确定真菌群落实际表达的分解酶编码基因。潜在的过程和驱动因素将在实验室实验中详细讨论，其中将在分解过程中评估温度制度和凋落物质量对不同山毛榉-叶-内生真菌基因表达谱的影响。该项目将提供一个巨大的数据库，除了宿主植物的生理和生化特征外，还将从分子上表征探索实验室中的山毛榉-内生真菌和凋落物降解真菌群落。特别是，元转录数据有可能揭示模式并提出远远超出所述假设的假设，特别是通过作为模拟营养循环和物种相互作用的基础。因此，假设驱动的方法将得到数据驱动的研究的补充，我们认为这将对未来关于生态系统过程的研究产生重大影响，而不仅仅是在生物多样性探索中。

The European Beech (Fagus sylvatica) is one of the most important and best studied trees in Central Europe. As all trees, it hosts an immense diversity of endophytic fungi. However, community structure of endophytic fungi is poorly understood, mostly due to the multiplicity of environmental factors involved. Furthermore, the functional diversity and ecological role of endophytic fungi in ecosystem processes, such as carbon and nitrogen cycling, is all but clear. Recent studies, however, showed that a considerable fraction of the endophytic community is also present in litter and has the enzymatic capabilities to degrade dead plant material. Here, we strive for unravelling biogeographical patterns, seasonal dynamics and land-use-dependency of beech-endophyllous fungi, their role in leaf-litter degradation and the life cycles of fungi colonizing the two habitats (living and decaying leaves). In particular, we test the implications of the hypothesis that by promoting tree individuals with enhanced defence capabilities, silviculture favours the establishment of host or habitat adapted endophytic fungi, which decompose leaf-litter more efficiently than less adapted fungi, thus contributing more significantly to the nutrient cycles.The design of the biodiversity exploratories provides an invaluable prerequisite for unravelling such complex connections. In addition to the available environmental background data from collaborating groups, leaf physiology and biochemistry will be consistently monitored to provide the basis for conclusively discussing the assessed molecular data. Next Generation Sequencing (NGS) of DNA- and RNA-derived markers will assess seasonal dynamics in community structure and activity profiles of endophytic and leaf-litter degrading fungi against regional, environmental and land-use gradients represented by the exploratory design. Metatranscriptomes in leaf-litter will be also analysed by NGS, to identify decomposition enzyme coding genes actually expressed by the fungal community. The underlying processes and driving factors will be addressed in detail in laboratory experiments, in which the impact of temperature regimes and litter quality on gene expression profiles of different beech-leaf-endophytic fungi, will be assessed during decomposition. The project will provide an immense data pool, molecularly characterising beech-endophyllous and litter degrading fungal communities in the exploratories, in addition to the physiological and biochemical characterisation of the host plants. In particular the metatranscriptomic data have the potential to reveal patterns and initiate hypotheses far beyond the addressed hypotheses, especially by serving as a basis for modelling nutrient cycles and species interactions. Accordingly, the hypothesis-driven approach will be complemented by data-driven research, which we assume to have a major impact on future studies on ecosystem processes, not only in the biodiversity-exploratories.