Exudate production : a detoxification strategy of wood decaying fungi

International audienceEven often observed, the exudate production in fungi remains mainly unstudied. During growth on oak wood, the white-rot fungus Trametes versicolor produces droplets of a red-brown liquid, this phenomenom being observed with nine studied strains. One of these strains secretes a similar exudate on rich medium even in the absence of wood. This secretion seems to be linked to the formation of special fungal structures involved in the production of extracellular enzymes. A proteomic study revealed that the protein content of the exudate is indeed closely related to extracellular enzymatic systems secreted by Trametes versicolor during oak degradation. It contains in particular enzymes involved in aromatic compounds oxidation such as Dye peroxidase, versatile and manganese peroxidases and also various carbohydrate-active enzymes. The proteomic studies revealed also the presence of a detoxification system involving glutathione related systems. In addition, a transcriptomic approach showed that this process is linked to induction of genes involved in intracellular degradation and detoxification of wood extractives and reactive oxygen species. From these observations, we propose that such exudate production by pioneer wood colonizers such as Trametes versicolor could be a way for facilitating extraction, concentration and degradation of wood extractives and other potential toxic by-products produced during the wood degradation oxidative process