CHEMICAL CROSS-TALK IN MYCOPARASITIC INTERACTIONS-ChemTalk

Fungi are rich sources of secondary metabolites (SMs), small bioactive molecules of medicinal and agricultural importance, that as well contribute to fundamental cellular processes like defense, communication with other (micro-) organisms, or virulence in pathogenic interactions. This is also true for Trichoderma mycoparasites, fungi that are able to attack and parasitize other fungi. However, most genes that are involved in SM production are not expressed when the fungus is cultivated in the lab under standard cultivation conditions but only when exogenous chemical cues are present. This project aims at elucidating the role of chemical cross-talk in triggering metabolite production and in mediating the interaction between two fungi, the mycoparasite Trichoderma atroviride and the plant pathogen Botrytis cinerea (grey mold). We will develop and employ a novel integrative approach for detection and spatial localization of small molecules produced and exchanged between two fungi. They will be studied in both interacting fungi at various cellular levels by applying a combination of cutting-edge technologies that is unparalleled in the field. The tailor-made integration of mass spectrometric imaging, high resolution metabolomics, live cell imaging, and gene expression analysis will provide novel insight into the complex fungus-fungus interaction and the identity and role of small molecules therein.

This research project explored how the plant-beneficial fungus Trichoderma atroviride and the plant pathogen Botrytis cinerea (grey mold disease) interact with each other by exchanging chemical signals. These signals, called specialized metabolites, are small molecules that fungi use to communicate, defend themselves, or attack others. The goal was to understand how these chemical signals work and to discover new ones that could be useful for agriculture or medicine. Fungi produce many useful compounds, like antibiotics, but they don't always make these compounds in the lab. To encourage both fungi to produce these hidden chemicals, they were cultivated together, mimicking their natural environment and it was tested how specific chemicals from one fungus affected the other. By doing this, we wanted to uncover new compounds and understand how fungi "talk" to each other. Key Findings We found that the amount and type of chemicals produced by T. atroviride depend on light conditions. Growing the fungus in reduced light or darkness increased the production of certain useful compounds, including one called 6-pentyl--pyrone (6-PP), which has antifungal and plant growth-promoting properties. The team further discovered the specific gene (pks1) responsible for 6-PP biosynthesis. When pks1 was removed, T. atroviride stopped producing 6-PP and became less effective at fighting B. cinerea. The phytopathogen B. cinerea was shown to break down 6-PP produced by T. atroviride and use it for its own energy revealing that fungi not only produce chemical signals but also respond to and metabolize the signals from others, creating a complex chemical "conversation." Why Does This Matter? This research helps us understand how fungi interact and compete in nature. In future, it could lead to better crop protection by improving the plant-beneficial effects of T. atroviride, a natural way to fight plant diseases caused by B. cinerea. Applying such biocontrol agents is a sustainable approach for managing plant diseases without relying on harmful chemicals. In addition, the obtained results may pave to way to finding new chemicals with potential uses in agriculture, medicine, or industry. In summary, this project has advanced our understanding of fungal interactions and opened up new possibilities for harnessing the power of fungi to address agricultural and environmental challenges. The interdisciplinary team revealed how fungi communicate through chemicals and opened the door to discovering new, useful compounds for a variety of applications.