ABSTRACT

Hydrophobins are low molecular weight proteins found ubiquitously in filamentous fungi. They are secreted as soluble monomers, but polymerize spontaneously at hydrophobic/hydrophilic interfaces to coat aerial structures such as conidia and fruiting bodies. Hydrophobins play multiple roles in fungal biology, ranging from conferring water resistance to fungal structures, to assisting the formation of aerial hyphae by reducing the surface tension of the growth medium, as well as mediating interactions between the fungus and its environment or host. Many hydrophobins polymerize into fibrillar assemblies (known as rodlets) that closely resemble amyloid fibrils, both in terms of structure and physical properties. In addition, the rodlets assemble laterally into monolayers that are amphipathic. Hydrophobin rodlets therefore represent an application of the amyloid structural scaffold by nature to serve

specific biological purposes, in contrast to the amyloid deposits that are commonly associated with disease states and protein misfolding. This chapter will focus on what is currently known about the sequence, structure, assembly mechanism, and physical properties of hydrophobin rodlets and discuss the diverse functions played by these fibrils in fungal biology and development.