The lichen symbiosis: Metabolites involved in lichenization

Project title and contents: Lichens are an intricate symbiosis between fungi and microalgae (in some cases, cyanobacteria can also be associated). As such, lichens are also one of the most successful examples of associations between rather dissimilar life-forms belonging to different "kingdoms of life". The very few lichen fossils found so far suggest that lichens were among the first organisms that colonised land about 600 million years ago. Still today, lichens are among the pioneers that colonise hostile environments, providing the basis for further plant and animal life. Interestingly, lichens produce a wide range of pharmaceutically active compounds, some of which have antibiotic and antiviral properties. The project "The lichen symbiosis: metabolites involved in lichenization" is dedicated to unravelling how free-living fungi and algae communicate with each other to form a lichen, and live together to the benefit of both. Hypotheses: We will explore if free-living algae release chemical compounds - some of which may be "plant hormones" - that can be recognized by fungi as a signal to grow together. Plant hormones control plant growth and development, but should not be confused with human hormones that have different chemical composition. We will first test if free-living alga and fungi release such "signalling" compounds, and if they are specific for lichen-forming alga. In the next step, we will test if a "cocktail" of the major compounds released by algae can attract fungi, and stimulate the formation of a lichen. In addition, it will be determined which genes change their activity when algae and fungi are close to each other, leading to the formation of a lichen. Methods: Initially, algae and fungi will be grown separately under sterile conditions in the laboratory. To identify the chemicals present in leachates produced by algae we will use state-of-the-art methods of "mass spectrometry" for molecular fingerprinting, such as those used by forensic scientists. We will then offer algal leachates and "hormone cocktails" to the fungi. In addition to mass spectrometry, we will use light microscopes (and electron microscopes) to see if the fungus responds to these substances by changing its shape and its metabolism, and eventually starts engulfing the algae to form a lichen. Novelty and innovation: Such "metabolite profiling" in conjunction with investigating gene activity has not been used on lichens so far, and it is not known if plant hormones play a role in the communication between the two partners. We will strive to identify the responsible chemical compounds for such "inter-kingdom signalling", providing in-depth insights into the basic requirements for lichen formation. Moreover, we may discover new hormones or molecules of potential interest for future biotechnological applications.