title: Spatially resolving the secretome within the mycelium of the cell factory Aspergillus niger.
abstract: Aspergillus niger is an important cell factory for the industrial production of enzymes. These enzymes are released into the culture medium, from which they can be easily isolated. Here, we determined with stable isotope dimethyl labeling the secretome of five concentric zones of 7-day-old xylose-grown colonies of A. niger that had either or not been treated with cycloheximide. As expected, cycloheximide blocked secretion of proteins at the periphery of the colony. Unexpectedly, protein release was increased by cycloheximide in the intermediate and central zones of the mycelium when compared to nontreated colonies. Electron microscopy indicated that this is due to partial degradation of the cell wall. In total, 124 proteins were identified in cycloheximide-treated colonies, of which 19 secreted proteins had not been identified before. Within the pool of 124 proteins, 53 secreted proteins were absent in nontreated colonies, and additionally, 35 proteins were released ≥4-fold in the central and subperipheral zones of cycloheximide-treated colonies when compared to nontreated colonies. The composition of the secretome in each of the five concentric zones differed. This study thus describes spatial release of proteins in A. niger, which is instrumental in understanding how fungi degrade complex substrates in nature.
authors.affiliation: Microbiology and Kluyver Centre for Genomics of Industrial Fermentation, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands.
authors.forename: Pauline
authors.initials: P
authors.lastname: Krijgsheld
authors.forename: A F Maarten
authors.initials: AF
authors.lastname: Altelaar
authors.forename: Harm
authors.initials: H
authors.lastname: Post
authors.forename: Jeffrey H
authors.initials: JH
authors.lastname: Ringrose
authors.forename: Wally H
authors.initials: WH
authors.lastname: Müller
authors.forename: Albert J R
authors.initials: AJ
authors.lastname: Heck
authors.forename: Han A B
authors.initials: HA
authors.lastname: Wösten
mesh_terms: D001234:Aspergillus niger / Q000187:drug effects / Q000378:metabolism*; D002473:Cell Wall / Q000187:drug effects / Q000378:metabolism; D003470:Culture Media / Q000378:metabolism; D003513:Cycloheximide / Q000494:pharmacology; D004591:Electrophoresis, Polyacrylamide Gel; D005656:Fungal Proteins / Q000302:isolation & purification* / Q000378:metabolism; D007553:Isotope Labeling; D046529:Microscopy, Electron, Transmission; D025282:Mycelium / Q000187:drug effects / Q000378:metabolism*; D014176:Protein Biosynthesis; D040901:Proteomics / Q000379:methods*; D055571:Secretory Pathway / Q000187:drug effects; D013997:Time Factors; D014994:Xylose / Q000378:metabolism
chemical_list: D003470:Culture Media; D005656:Fungal Proteins; D003513:Cycloheximide; D014994:Xylose