Why do fungi oxidize their cell wall carbohydrates?

Objective

The fungal cell wall (FCW) is the primary interface between the fungal cell and its surrounding. This statement applies to all types of fungi, regardless of whether they live in symbiosis, cause disease, or decompose organic matter. As smart architects, fungi have found ways to evolve the chemical composition of this wall (made mostly of carbohydrates) to thrive and constantly adapt to various environmental factors. To date, to which extent, how and what for the FCW is modified remains largely unknown. I hypothesize that fungi use “carbohydrate oxidases” (CarbOx) to cleave and/or functionalize their FCW carbohydrates, thereby altering their physico-chemical properties to fulfil diverse putative functions. In the FOX project, I will aim at unravelling the diversity and biological functions of FCW-active CarbOx. Here, using approaches at the interface between enzymology and microbiology, I propose to decipher the biological functions of pre-identified FCW-active CarbOx in a model filamentous fungus. Then, using an ad hoc methodology integrating in muro detection of oxidized carbohydrates, proteomics and computational modelling, we will draw a comprehensive portrait of FCW carbohydrate oxidation events and pinpoint responsible CarbOx. Building on these insights and methods, we will build experimentally-supported models to probe and test the occurence of these oxidative mechanisms across the fungal kingdom. By unravelling and providing a comprehensive understanding of the oxidative chemistry and function of CarbOx during FCW remodelling, my research will lay the conceptual and practical foundations of FCW oxidative enzymology. Given the involvement of fungi in a myriad of life-sustaining and threatening processes, as well as in industrial bioprocesses, I anticipate that FOX will have wide-ranging implications for the health, agriculture and biotechnology sectors.