Has been implicated in the pathogenicity of this fungus on ELM. Accumulates at, and plugs intercellular openings in the xylem, or interacts with host parenchyma cells, thereby enhancing respiration and electrolyte loss. Strain P1 is a non-aggressive isolate, while strain MH75 is an aggressive isolate. Belongs to the cerato-ulmin hydrophobin family.