Epigenetics of Filamentous Fungi
Epigenetic phenomena are defined by reversible heritable changes in gene expression in the absence of changes in DNA sequence. These include, among others, DNA methylation, position effects, RNA silencing systems, and centromere location. The term epigenetics is now also more loosely applied to describe gene regulation via change in chromatin structure, even though such changes are not necessarily heritable (e.g., they may occur in terminally differentiated cells). The filamentous fungi, in particular Neurospora crassa, have provided fundamental advances in many of the areas mentioned above. Notably, they share silencing systems that are conserved in higher eukaryotes, for instance RNA interference (RNAi) and DNA methylation. Much can be learned about general mechanisms for these phenomena by comparative biology, for which fungi are especially useful. This is because they are relatively simple organisms with small genomes that often lack redundancy, and they are amenable to rapid genetic manipulations, biochemistry and cytology. At the same time, the manipulation of chromatin structure in fungi promises to unlock previously untapped biochemical potential, for instance in the production of secondary metabolites. In this chapter, a review will be provided of previously conducted studies, notably those reported during the past two years. Areas of research will also be suggested where more depth – or indeed any study – is required to make use of the full potential of filamentous fungi as model organisms.