Molecular and cellular basis of infection-related dimorphism in Zymoseptoria tritici

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Crop-infecting fungi are a major threat to the global food security. In fact, losses of wheat, rice, and maize to fungal pathogens, per year, is the same as the annual spend by US Department of Homeland Security - some 60 billion US dollars. Fungi are kept under control by treatment with anti-fungal chemicals. However, as fast growing microbes, fungi adapt to become resistant to fungicide treatments, and so we need to develop new fungicides all the time. This requires an in-depth knowledge of the invasion strategies of fungal pathogens.In this project, we focus on the number-one wheat pathogen in Europe, Zymoseptoria tritici, the causative agent of Septoria tritici blotch in wheat. The fungus lives on debris in the field, where it grows as a small "yeast-like" structure. However, rain-splash can transport this spore onto the leaf surface. Here, the fungus undergoes a change in growth and forms an elongated string of cells, the hypha, which expands at the tip and invades the plant leaf. Published data and our preliminary results clearly demonstrate that this "dimorphic switch" is an essential of infection of the plant by the fungus. Thus, understanding the process of the yeast-to-hypha transition is important to develop novel antifungal chemistries. Despite its importance for wheat infection, our knowledge of the requirements for dimorphic switching in Z. tritici is fragmentary. This project aims to understand the processes underlying host invasion by the fungus and to identify pathways and requirement within the fungus that control the dimorphic switching. We will undertake this work by genetic screening, identifying protein-protein interactions, live cell imaging in the plant and observing the fungal cell itself during its transition from a yeast to a hypha. Moreover, we collaborate with a company that provides a novel antifungal product and investigate the way by which fungicide inhibits infection of wheat by Z. tritici. It is important to reiterate that the dimorphic switch occurs very early in the fungal infection process, at a time when the fungi are most accessible to fungicide treatment. Disabling the process could therefore result in a new generation of "preventive" fungicides that are able to act on STB before the fungus has damaged its host plant , wheat.