Understanding the molecular traits of multi-organismic communication in beneficial tree-microbe associations

• Applicants: Professor Dr. J. Philipp Benz; Professor Dr. Jörg-Peter Schnitzler, since 11/2022
• Subject Area: Plant Physiology ; Organismic Interactions, Chemical Ecology and Microbiomes of Plant Systems
• Term: since 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 445525687

In natural environments, plants and fungi do not live in isolation but are in continuous interaction with each other. Communication processes between them are vital for the fate of their interactions. These occur through signaling compounds such as fungal- and root-derived sugars or volatile organic compounds (VOCs). Plant VOCs are well known to be involved e.g. in deterring herbivores or attracting predators, but recently more evidence highlights the importance of VOCs also in rhizosphere ecology. Most studies so far, however, have concentrated on bilateral systems, thereby neglecting the complexities of more natural, multi-organismic scenarios. Therefore, questions such as how additional partners might change the communication, and which the mechanistic changes are – particularly in the establishment state, are far from being understood. The overall aim of the present proposal is to decipher the VOC- and carbohydrate-mediated communication of a woody host plant (Populus x canescens) in association with per se plant-beneficial fungi represented by Trichoderma harzianum and the ecto-mycorrhiza Laccaria bicolor. The chosen tripartite interaction is highly relevant since the partners are all very common, share habitats, and similar interactions will frequently occur in the wild. However, due to the biocontrol ability of Trichoderma and the associated fungal antagonism, the fate of the interaction is completely unpredictable so far, making the interaction an excellent model to study inter-species communication between symbiosis and parasitism. The first goal is to achieve a detailed overview regarding the pathways and molecular factors involved in the inter-species communication and recognition in the early establishment phase of the system on a whole-genome level. Candidates and factors known to be involved will subsequently be studied by the analysis of corresponding mutants in Trichoderma. Moreover, to understand the VOC-based communication of the individual partners, we will analyze the volatile profiles over the establishment state of the relationship. Recently, it was shown that poplar, upon detection of fungal VOCs, adjust its redox balance and root architecture. Thus, the plant internal signaling upon perceiving VOCs from the mutualistic partner(s) will be further deciphered. Moreover, only little is known about the response of filamentous fungi to root volatiles. To this end, we will study the physiological and transcriptional response of Trichoderma upon exposure to poplar- and Laccaria-derived volatiles. Potential applications for the knowledge gained through this project are improved concepts for reforestation or phytoremediation of contaminated sites using combinations of woody plants and plant-beneficial fungi. Importantly, the current association of groups with profound expertise in fungal and plant molecular biology and physiology is unique and perfectly tailored to the challenges of this project.

• DFG Programme: Research Grants
• Ehemalige Antragstellerin: Dr. Maaria Rosenkranz, until 11/2022