Differential protein phosphorylation-dephosphorylation in response to carbon source in Ruminococcus flavefaciens FD-1

The Duality of the MAPK Signaling Pathway in the Control of Metabolic Processes and Cellulase Production in Trichoderma reesei

In this study, through global transcriptional analysis by RNA-Sequencing, we identified the main changes in gene expression that occurred in two functional mutants of the MAPK genes tmk1 and tmk2 in Trichoderma reesei during sugarcane bagasse degradation. We found that the proteins encoded by these genes regulated independent processes, sometimes in a cross-talk manner, to modulate gene expression in T. reesei. In the Δtmk2 strain, growth in sugarcane bagasse modulated the expression of genes involved in carbohydrate metabolism, cell growth and development, and G-protein-coupled receptor-mediated cell signaling. On the other hand, deletion of tmk1 led to decreased expression of the major genes for cellulases and xylanases. Furthermore, TMK1 found to be involved in the regulation of the expression of major facilitator superfamily transporters. Our results revealed that the MAPK signaling pathway in T. reesei regulates many important processes that allow the fungus to recognize, transport, and metabolize different carbon sources during plant cell wall degradation.

New Genomic Approaches to Enhance Biomass Degradation by the Industrial Fungus Trichoderma reesei

The filamentous fungi Trichoderma reesei is one of the most well-studied cellulolytic microorganisms. It is the most important fungus for the industrial production of enzymes to biomass deconstruction being widely used in the biotechnology industry, mainly in the production of biofuels. Here, we performed an analytic review of the holocellulolytic system presented by T. reesei as well as the transcriptional and signaling mechanisms involved with holocellulase expression in this fungus. We also discuss new perspectives about control of secretion and cellulase expression based on RNA-seq and functional characterization data of T. reesei growth in different carbon sources, which comprise glucose, cellulose, sophorose, and sugarcane bagasse.

ScaC, an adaptor protein carrying a novel cohesin that expands the dockerin-binding repertoire of the Ruminococcus flavefaciens 17 cellulosome

A new gene, designated scaC and encoding a protein carrying a single cohesin, was identified in the cellulolytic rumen anaerobe Ruminococcus flavefaciens 17 as part of a gene cluster that also codes for the cellulosome structural components ScaA and ScaB. Phylogenetic analysis showed that the sequence of the ScaC cohesin is distinct from the sequences of other cohesins, including the sequences of R. flavefaciens ScaA and ScaB. The scaC gene product also includes at its C terminus a dockerin module that closely resembles those found in R. flavefaciens enzymes that bind to the cohesins of the primary ScaA scaffoldin. The putative cohesin domain and the C-terminal dockerin module were cloned and overexpressed in Escherichia coli as His(6)-tagged products (ScaC-Coh and ScaC-Doc, respectively). Affinity probing of protein extracts of R. flavefaciens 17 separated in one-dimensional and two-dimensional gels with recombinant cohesins from ScaC and ScaA revealed that two distinct subsets of native proteins interact with ScaC-Coh and ScaA-Coh. Furthermore, ScaC-Coh failed to interact with the recombinant dockerin module from the enzyme EndB that is recognized by ScaA cohesins. On the other hand, ScaC-Doc was shown to interact specifically with the recombinant cohesin domain from ScaA, and the ScaA-Coh probe was shown to interact with a native 29-kDa protein spot identified as ScaC by matrix-assisted laser desorption ionization-time of flight mass spectrometry. These results suggest that ScaC plays the role of an adaptor scaffoldin that is bound to ScaA via the ScaC dockerin module, which, via the distinctive ScaC cohesin, expands the range of proteins that can bind to the ScaA-based enzyme complex.