What we (still don't) know about wood-degrading fungi: an overview of threats and utilization potentials

Wood, being one of the most abundant materials on Earth, is a hierarchically structured lignocellulosic biocomposite that has evolved to resist decomposition by other organisms. While lignin is thought to have evolved in the Devonian (~ 400-390 Ma), leading to the deposition of vast coal reserves in the Carboniferous (~ 360-299 Ma), a diverse group of fungi evolved around that time to precisely break through this barrier and use it as carbon source. The emerging "wood-degrading fungi" since then play a fundamental role in global nutrient cycling, carbon flow, and material turnover. The significance of wood-degrading fungi lies both in their applicability thanks to their enzyme systems, transporters, and metabolites, and in their being threats to forests, wood products, and health. This duality is similar, albeit maybe less known to the public, than the one in the food industry, where fungi have both useful applications (e.g., in food coloring, food fermentation, and as protein sources) and risks (e.g., through mycotoxins). Moreover, studies on fungal colonization and substrate attack in connection with fungal degradation in the built environment have expanded our mechanistic understanding of their natural behavior. In the present mini-review, we provide an overview of the mechanisms by which fungi degrade wood and discuss both the threats to living trees and wood products associated with wood-degrading fungi as well as their potential for added value in the bioeconomy. We furthermore aim to highlight important macroscopic and microscopic aspects to provide an integrative view of the mechanisms involved, including data retrieved by genomic and literature meta-analyses. This mini-review integrates insights from the literature with exploratory analyses of diverse databases to provide a holistic view of wood-degrading fungi, supporting future perspectives and a multidimensional understanding of these organisms.