QUANTITATIVE PROTEOME PROFILING OF NEUROSPORA CRASSA REVEALS A CELLOBIOSE-DEPENDENT NETWORK COORDINATING LIGNOCELLULOLYTIC RESPONSES

Cellulose, particularly the major cellulolytic product cellobiose, can induce the production of enzymes associated with deconstruction of lignocellulose in filamentous fungi. However, the detailed mechanisms underlying this biotechnologically important process remain to be disclosed. Here, the proteome response to cellobiose, crystalline cellulose (Avicel), and carbon starvation of a Neurospora crassa triple β-glucosidase mutant were compared using tandem mass tag (TMT)-based proteome quantification. Improved quantification accuracy was achieved with synchronous precursor selection (SPS)-based MS3 technology compared to MS2 using a high resolution tribrid mass spectrometer. Exposure to carbon starvation, cellobiose or Avicel induced the production of cellulase and lytic polysaccharide monooxygenase enzymes in N. crassa, as well as a cellobionic acid transporter, indicating their functional roles in the early adaptation to plant cell wall. In particular, cellobiose specifically induced the production of proteins in the functional categories of protein processing and export as well as cell wall organization. The data presented here integrates the signaling pathway associated with cellobiose transporters CDT-1 and/or CDT-2 with the direct targets of the transcription factors CLR-1, CLR-2, and XLR-1, the unfolded protein response (UPR) mediated by Ire-1/Hac-1, as well as calcium homeostasis and cell wall organization. The cellobiose-dependent response network will be useful for rational strain improvement to facilitate the production of lignocellulases in filamentous fungi and plant biomass-based products.