Evolution of lignin decomposition systems in fungi

Lignin represents the second most abundant biopolymer of the plant cell wall. Among microorganisms, fungi are the most efficient lignin decomposers. The discovery of ligninolysis by fungi could have altered the ancient carbon cycle at the global scale and it is still one of the processes that determine carbon sequestration and soil formation. Understanding the evolution of ligninolytic systems represents a great challenge because lignin decomposition relies on complex gene networks, for which we have only fragmented information. Moreover, not all fungi can break down lignin and among ligninolytic fungi, there is enormous variation in ligninolytic efficiency, which has not been documented extensively. Genomic sequences offer an extraordinary opportunity to understand evolutionary processes. Here, we present the contribution of fungal comparative genomics to the evolution of ligninolytic systems in fungi and we conclude with a series of questions that remain to be answered.