Secretion of proteins in filamentous fungi

Arman Vinck, Han Wösten

Fungal hyphae may have a considerable length. Yet, hyphal growth and protein secretion occur in the hyphal tip in the most apical region of up to several micrometers (under lab conditions) . The fungal hypha is thus a highly polarized system. Fungal hyphae and their branches are compartmentalised by simple or complex septa. These septa are porous and allow (free) passage of nutrients, cell components or organelles. Thus, the cytoplasm within a fungal mycelium seems to be a continuous system .

Despite the intriguing polarity and the fact that the secretion capacity of filamentous fungi is used for the industrial production of proteins, hardly anything is known about the mechanisms that underlie this process. We are studying which part of the hypha supports the secretion of proteins. Until now it is not known where transcription and translation of respectively the genes and the mRNA of secreted proteins occurs. It may be that these processes are concentrated near the tip. Alternatively, subapical zones of the fungal hyphae are involved, requiring long distance transport of the mRNA and or the secreted proteins.

As model systems we study glucoamylase secretion in the ascomycete Aspergillus nigerand SC3 secretion in the basidiomycete Schizophyllum commune.