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Transcriptional landscape of Myceliophthora thermophila responding to soluble starch and the role of regulator AmyR on polysaccharide degradation

ABSTRACT: Thermophilic fungus Myceliophthora thermophila with great capacity for polysaccharides degradation is attractive to be engineered into a cell factory to produce chemicals and biofuels directly from renewable polysaccharides such as starch. Understanding the molecular mechanism of starch degradation of the fungi would be helpful. To date, there has been no transcriptome analysis on starch in thermophilic fungi. In this study, we performed the transcriptomic profile of M. thermophila responding to soluble starch, and a 342-gene set was identified as “starch regulon”, including the major amylolytic enzyme (Mycth_72393), which was verified thereafter as the most important such hydrolase for starch degradation in this fungus. Moreover, the function of key amylolytic enzyme regulator AmyR in M. thermophila was evaluated by analyzing the performance of its deletion mutant using our CRISPR/Cas9 system, which showed significantly decreased amylase activity and poor growth on starch. Additionally, deletion of amyR led to resistance to carbon catabolite repression (CCR) and enhanced cellulases production. Our study provides an insight into understanding the molecular basis of starch degradation in this thermophilic fungus, and will accelerate the fungal strain rational engineering for starch-based biochemical production.

ORGANISM(S): Thermothelomyces thermophilus

PROVIDER: GSE110062 | GEO | 2021/02/02

REPOSITORIES: GEO

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Project description:Plant biomass holds tremendous potential as a renewable feedstock in the production of biofuels and biochemicals. The effective co-utilization of the main components cellulose and hemicellulose in plant lignocellulose is critical to the economic viability of lignocellulosic biorefineries. Here, we found that the thermophilic cellulolytic fungi Myceliophthora thermophila can utilize cellulose and hemicellulose synchronously. To investigate the underlying molecular mechanisms, we firstly checked the soluble carbohydrate of the culture using plant biomass (corncob) as sole carbon source and revealed the presence of various oligosaccharides including cellodextrin and xylodextrin, both intracellularly and extracellularly in the cultures, in addition to glucose or xylose. Based on these, intracellular oligosaccharide metabolism was proposed and confirmed by identification of cellodextrin and xylodextrin metabolism pathway. Furthermore, sugar consumption assay showed that contrasting with synchronous utilization of mixed cello-/xylo-dextrin, the inhibition effect of glucose for the metabolism of xylose and cello-/xylo-dextrin exists in this fungus, suggesting Carbon Catabolite Repression (CCR) is largely avoided at the form of oligosaccharides. Transporter MtCDT-2 showing preference to xylobiose and the tolerance of cellobiose inhibition also helps to bypass metabolic inhibition. Finally, the expression of cellulase and hemicellulase genes, were found orthogonal induction by cellobiose/Avicel and xylobiose/xylan, which conferred the ability of the strain to synchronously utilize cellulose and hemicellulose. Taken together, the orthogonal oligosaccharide catabolic pathway in this fungus establishes the molecular basis for the synchronous utilization of cellulose and hemicellulose, which sheds new light on understanding the plant biomass degradation by fungi and provides alternative paradigm for development of lignocellulose biorefinery such as consolidated bioprocessing in the future.

Dataset Information

Transcriptional landscape of Myceliophthora thermophila responding to soluble starch and the role of regulator AmyR on polysaccharide degradation

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