Novel hydrophobins from Trichoderma define a new hydrophobin subclass: protein properties, evolution, regulation and processing.

Hydrophobins are small proteins, characterised by the presence of eight positionally conserved cysteine residues, and are present in all filamentous asco- and basidiomycetes. They are found on the outer surfaces of cell walls of hyphae and conidia, where they mediate interactions between the fungus and the environment. Hydrophobins are conventionally grouped into two classes (class I and II) according to their solubility in solvents, hydropathy profiles and spacing between the conserved cysteines. Here we describe a novel set of hydrophobins from Trichoderma spp. that deviate from this classification in their hydropathy, cysteine spacing and protein surface pattern. Phylogenetic analysis shows that they form separate clades within ascomycete class I hydrophobins. Using T. atroviride as a model, the novel hydrophobins were found to be expressed under conditions of glucose limitation and to be regulated by differential splicing.