Oxidative Damage Control during Decay of Wood by Brown Rot Fungus Using Oxygen Radicals

Wood is one of the largest pools of carbon on Earth, and its decomposition is dominated in most systems by fungi. Wood-degrading fungi specialize in extracting sugars bound within lignin, either by removing lignin first (white rot) or by using Fenton-generated reactive oxygen species (ROS) to “loosen” wood cell walls, enabling selective sugar extraction (brown rot). Although white rot lignin-degrading pathways are well characterized, there are many uncertainties in brown rot fungal mechanisms. Our study addressed a key uncertainty in how brown rot fungi deploy ROS without damaging themselves or the enzymes they secrete. In addition to revealing differentially expressed genes to promote ROS generation only in early decay, our study revealed three spatial control mechanisms to avoid/tolerate ROS: (i) constraining Fenton reactant concentrations (H 2 O 2 , Fe 2+ ), (ii) quenching ROS via antioxidants, and (iii) secreting ROS-tolerant enzymes. These results not only offer insight into natural decomposition pathways but also generate targets for biotechnological development.