Abstract
Fungal plant cell wall degradation processes are governed by complex regulatory mechanisms, allowing the organisms to adapt their metabolic program with high specificity to the available substrates. While the uptake of representative plant cell wall mono- and disaccharides is known to induce specific transcriptional and translational responses, the processes related to early signal reception and transduction remain largely unknown. A fast and reversible way of signal transmission are post-translational protein modifications, such as phosphorylations, which could initiate rapid adaptations of the fungal metabolism to a new condition. To elucidate how changes in the initial substrate recognition phase of Neurospora crassa affect the global phosphorylation pattern, phospho-proteomics was performed after a short (2 min) induction period with several plant cell wall-related mono- and disaccharides. The MS/MS-based peptide analysis revealed large-scale substrate-specific protein phosphorylation and de-phosphorylations. Using the proteins identified by MS/MS, a protein-protein-interaction (PPI) network was constructed. The variance in phosphorylation of a large number of kinases, phosphatases and transcription factors indicate the participation of many known signaling pathways, including circadian responses, two-component regulatory systems, MAP kinases as well as the cAMP-dependent and heterotrimeric G-protein pathways. Adenylate cyclase, a key component of the cAMP pathway, was identified as a potential hub for carbon source-specific differential protein interactions. In addition, four phosphorylated F-Box proteins were identified, two of which, Fbx-19 and Fbx-22, were found to be involved in carbon catabolite repression responses. Overall, these results provide unprecedented and detailed insights into a so far less well known stage of the fungal response to environmental cues and allow to better elucidate the molecular mechanisms of sensory perception and signal transduction during plant cell wall degradation.
Highlights
Fungi are cell factories with important functions for the bioeconomy since they often exhibit superior metabolic and secretory capabilities compared to bacterial and yeast-based production systems (Meyer et al, 2016)
To identify the extent of initial protein phosphorylations upon exposure to new carbon sources, we performed switch experiments, in which sucrose pre-grown N. crassa was first starved for 30 min and incubated for 2 min with monoand disaccharides that are known to act as signaling molecules for plant cell wall-related polysaccharides
This short retention period was deliberately chosen to allow N. crassa to take up inducer molecules, but ensure that the proteome does not have time to significantly change, so that all measured differences are due to post-translational changes as a reaction to nutrient availability and not due to changes in enzyme abundances
Summary
Fungi are cell factories with important functions for the bioeconomy since they often exhibit superior metabolic and secretory capabilities compared to bacterial and yeast-based production systems (Meyer et al, 2016). In the case of fungal utilization of complex plant biomass, the specific perception of the individual plant cell wall components is a necessary pre-requisite to adapt enzyme production and intracellular metabolism. These recognition reactions trigger a sophisticated series of intracellular signaling cascades in order to control and coordinate the cellular response. The resulting monomeric and/or small oligomeric soluble sugars are transferred into the cell via membrane-embedded transporters These sugars (or their metabolic derivatives) can function as signaling molecules that activate signal cascades to promote specific metabolic adaptations (see e.g., Glass et al, 2013 and references therein). The signaling reactions that occur between the first substrate contact and the gene activation by transcription factors are poorly described, making it difficult to predict good targets for strain engineering
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
