Aspergillus nidulans protein kinase A plays an important role in cellulase production. Issue 1 (December 2015)

• Record Type: Journal Article
• Authors: Assis, Leandro; Ries, Laure; Savoldi, Marcela; Reis, Thaila; Brown, Neil; Goldman, Gustavo
• Is Part Of: Biotechnology for biofuels. Volume 8:Issue 1(2015)
• Page Start: 1
• Page End: 20
• Publication Date: 2015-12
• Subjects: Aspergillus nidulans -- Protein kinase A -- Carbon catabolite repression -- Glucose metabolism -- Cellulose; Biotechnology -- Periodicals; Biomass energy -- Periodicals; Energy-Generating Resources -- Periodicals; 662.88
• DOI: 10.1186/s13068-015-0401-1
• Languages: English
• ISSNs: 1754-6834

Abstract

Abstract Background The production of bioethanol from lignocellulosic feedstocks is dependent on lignocellulosic biomass degradation by hydrolytic enzymes. The main component of lignocellulose is cellulose and different types of organisms are able to secrete cellulases. The filamentous fungusAspergillus nidulans serves as a model organism to study cellulase production and the available tools allow exploring more in depth the mechanisms governing cellulase production and carbon catabolite repression. Results InA. nidulans, microarray data identified the cAMP-dependent protein kinase A (PkaA) as being involved in the transcriptional modulation and the production of lignocellulolytic enzymes in the presence of cellulose. Deletion ofpkaA resulted in increased hydrolytic enzyme secretion, but reduced growth in the presence of lignocellulosic components and various other carbon sources. Furthermore, genes involved in fungal development were increased in the ΔpkaA strain, probably leading to the increased hyphal branching as was observed in this strain. This would allow the secretion of higher amounts of proteins. In addition, the expression of SynA, encoding a V-SNARE synaptobrevin protein involved in secretion, was increased in theΔpkaA mutant. Deletion ofpkaA also resulted in the reduced nuclear localization of the carbon catabolite repressor CreA in the presence of glucose and in partial de-repression when grown on cellulose. PkaA is involved in the glucose signaling pathway as the absence of this protein resulted in reduced glucose uptake and lower hexokinase/glucokinase activity, directing the cell to starvation conditions. Genome-wide transcriptomics showed that the expression of genes encoding proteins involved in fatty acid metabolism, mitochondrial function and in the use of cell storages was increased. Conclusions This study shows that PkaA is involved in hydrolytic enzyme production inA. nidulans . It appears that this protein kinase blocks the glucose pathway, hence forcing the cell to change to starvation conditions, increasing hydrolytic enzyme secretion and inducing the usage of cellular storages. This work uncovered new regulatory avenues governing the tight interplay between the metabolic states of the cell, which are important for the production of hydrolytic enzymes targeting lignocellulosic biomass. Deletion ofpkaA resulted in a strain with increased hydrolytic enzyme secretion and reduced biomass formation.