Systems approaches to predict the functions of glycoside hydrolases during the life cycle of Aspergillus niger using developmental mutants ∆brlA and ∆flbA

Jolanda M van Munster, Benjamin M Nitsche, Michiel Akeroyd, Lubbert Dijkhuizen, Marc J E C van der Maarel, Arthur F J Ram

Research output: Contribution to journalArticlepeer-review

13 Citations (Scopus)

Abstract

BACKGROUND: The filamentous fungus Aspergillus niger encounters carbon starvation in nature as well as during industrial fermentations. In response, regulatory networks initiate and control autolysis and sporulation. Carbohydrate-active enzymes play an important role in these processes, for example by modifying cell walls during spore cell wall biogenesis or in cell wall degradation connected to autolysis.

RESULTS: In this study, we used developmental mutants (ΔflbA and ΔbrlA) which are characterized by an aconidial phenotype when grown on a plate, but also in bioreactor-controlled submerged cultivations during carbon starvation. By comparing the transcriptomes, proteomes, enzyme activities and the fungal cell wall compositions of a wild type A. niger strain and these developmental mutants during carbon starvation, a global overview of the function of carbohydrate-active enzymes is provided. Seven genes encoding carbohydrate-active enzymes, including cfcA, were expressed during starvation in all strains; they may encode enzymes involved in cell wall recycling. Genes expressed in the wild-type during starvation, but not in the developmental mutants are likely involved in conidiogenesis. Eighteen of such genes were identified, including characterized sporulation-specific chitinases and An15g02350, member of the recently identified carbohydrate-active enzyme family AA11. Eight of the eighteen genes were also expressed, independent of FlbA or BrlA, in vegetative mycelium, indicating that they also have a role during vegetative growth. The ΔflbA strain had a reduced specific growth rate, an increased chitin content of the cell wall and specific expression of genes that are induced in response to cell wall stress, indicating that integrity of the cell wall of strain ΔflbA is reduced.

CONCLUSION: The combination of the developmental mutants ΔflbA and ΔbrlA resulted in the identification of enzymes involved in cell wall recycling and sporulation-specific cell wall modification, which contributes to understanding cell wall remodeling mechanisms during development.

Original languageEnglish
Article numbere0116269
JournalPLoS ONE
Volume10
Issue number1
Early online date28 Jan 2015
DOIs
Publication statusFirst published - 28 Jan 2015
Externally publishedYes

Keywords

  • Aspergillus niger/genetics
  • Bioreactors
  • Carbohydrates/chemistry
  • Cell Wall/chemistry
  • Fermentation
  • Fungal Proteins/genetics
  • Gene Deletion
  • Gene Expression Profiling
  • Gene Expression Regulation, Fungal
  • Glycogen/metabolism
  • Glycoside Hydrolases/genetics
  • Hydrolysis
  • Mutation
  • Phenotype
  • Proteome
  • Transcriptome

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