Hydrophobins RolA and HypB from Aspergillus oryzae function on the surface of conidia and aerial hyphae, respectively

Hydrophobins are low-molecular-weight amphiphilic proteins found in filamentous fungi. In this study, we focused on two Aspergillus oryzae hydrophobins, whose biological functions were unclear. We found that hydrophobins RolA and HypB are highly expressed. We created strains with disruption of one of the respective genes, ΔrolA and ΔhypB, and examined their phenotypes under various stress conditions. The two strains had different phenotypes under stress conditions that affected the cell wall surface function. Self-assembled structures on the conidial surface were absent in the ΔrolA strain, whereas specific structures on the surface of aerial hyphae were absent in the ΔhypB strain. Colony hydrophobicity was lower in the ΔhypB strain than in the control CNT strain, whereas conidial surface hydrophobicity was lower in the ΔrolA strain than in the control CNT strain. These findings indicate that RolA and HypB share similar functions on the cell surface, but RolA functions mainly on the conidial surface, whereas HypB functions mainly on the surface of aerial hyphae.