Abstract
Cellulose is recalcitrant to deconstruction to glucose for use in fermentation strategies for biofuels and chemicals derived from lignocellulose. In Neurospora crassa, the transcriptional regulator, CLR-2, is required for cellulolytic gene expression and cellulose deconstruction. To assess conservation and divergence of cellulase gene regulation between fungi from different ecological niches, we compared clr-2 function with its ortholog (clrB) in the distantly related species, Aspergillus nidulans. Transcriptional profiles induced by exposure to crystalline cellulose were similar in both species. Approximately 50% of the cellulose-responsive genes showed strict dependence on functional clr-2/clrB, with a subset of 28 genes encoding plant biomass degrading enzymes that were conserved between N. crassa and A. nidulans. Importantly, misexpression of clr-2 under noninducing conditions was sufficient to drive cellulase gene expression, secretion, and activity in N. crassa, to a level comparable to wild type exposed to Avicel. However, misexpression of clrB in A. nidulans was not sufficient to drive cellulase gene expression under noninducing conditions, although an increase in cellulase activity was observed under crystalline cellulose conditions. Manipulation of clr-2 orthologs among filamentous fungi may enable regulated cellulosic enzyme production in a wide array of culture conditions and host strains, potentially reducing costs associated with enzyme production for plant cell wall deconstruction. However, this functionality may require additional engineering in some species.
Highlights
Saprotrophic fungal species are major agents of plant decay in the environment (Kominkova et al 2000; Hieber and Gessner 2002), with influences on the global carbon cycle (Heimann and Reichstein 2008), local nutrient flows (Frey et al 2003), and the historic accumulation of fossil fuel deposits (Floudas et al 2012)
To elucidate the fungal potential for plant cell wall deconstruction and explore how environmental factors affect the production of enzymes mediating decay, we study regulatory mechanisms associated with cellulose degradation in two distantly related model filamentous fungi, Neurospora crassa and Aspergillus nidulans
To compare its Avicel regulon with that of N. crassa, A. nidulans wild-type strains were switched from a simple carbon source, glucose to Avicel, or no carbon source media; transcriptional profiles of the switched cultures were analyzed with RNA-seq
Summary
Saprotrophic fungal species are major agents of plant decay in the environment (Kominkova et al 2000; Hieber and Gessner 2002), with influences on the global carbon cycle (Heimann and Reichstein 2008), local nutrient flows (Frey et al 2003), and the historic accumulation of fossil fuel deposits (Floudas et al 2012). To elucidate the fungal potential for plant cell wall deconstruction and explore how environmental factors affect the production of enzymes mediating decay, we study regulatory mechanisms associated with cellulose degradation in two distantly related model filamentous fungi, Neurospora crassa and Aspergillus nidulans. We found that misexpression of clr-2 in N. crassa induced cellulase gene expression and activity under noninducing conditions and increased cellulase activity when the misexpression strain was exposed to crystalline cellulose To our knowledge, this is first report of that the manipulation of one gene can circumvent the dependence of inducers for cellulase production. Our experiments suggest that the manipulation of clr-2 orthologs among filamentous fungi holds great potential for the identification and characterization of new enzymes These studies will increase our understanding of mechanistic aspects of plant cell wall deconstruction and the development of optimal enzyme cocktails for cellulose degradation
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.
