Induction of Genes Encoding Plant Cell Wall-Degrading Carbohydrate-Active Enzymes by Lignocellulose-Derived Monosaccharides and Cellobiose in the White-Rot Fungus Dichomitus squalens

Abstract

Fungi can decompose plant biomass into small oligo- and monosaccharides to be used as carbon sources. Some of these small molecules may induce metabolic pathways and the production of extracellular enzymes targeted for degradation of plant cell wall polymers. Despite extensive studies in ascomycete fungi, little is known about the nature of inducers for the lignocellulolytic systems of basidiomycetes. In this study, we analyzed six sugars known to induce the expression of lignocellulolytic genes in ascomycetes for their role as inducers in the basidiomycete white-rot fungus using a transcriptomic approach. This identified cellobiose and l-rhamnose as the main inducers of cellulolytic and pectinolytic genes, respectively, of Our results also identified differences in gene expression patterns between dikaryotic and monokaryotic strains of cultivated on plant biomass-derived monosaccharides and the disaccharide cellobiose. This suggests that despite conservation of the induction between these two genetic forms of, the fine-tuning in the gene regulation of lignocellulose conversion is differently organized in these strains. Wood-decomposing basidiomycete fungi have a major role in the global carbon cycle and are promising candidates for lignocellulosic biorefinery applications. However, information on which components trigger enzyme production is currently lacking, which is crucial for the efficient use of these fungi in biotechnology. In this study, transcriptomes of the white-rot fungus from plant biomass-derived monosaccharide and cellobiose cultures were studied to identify compounds that induce the expression of genes involved in plant biomass degradation.

The White-Rot Basidiomycete Dichomitus squalens Shows Highly Specific Transcriptional Response to Lignocellulose-Related Aromatic Compounds

“…In this study, we used genome-wide transcriptomic analysis to provide the first systematic insight into conversion of various lignocellulose-related aromatic compounds by the well-studied white-rot fungus D. squalens (Dong et al, 2014; Rytioja et al, 2015, 2017; Casado López et al, 2017; Daly et al, 2018). While previous works have applied high-throughput RNA sequencing (RNA-seq) to identify upregulated transcripts from D. squalens cultivated on various lignocellulosic substrates (Rytioja et al, 2017; Daly et al, 2018) and lignocellulose-derived monomeric sugars (Casado López et al, 2018), providing novel insights into plant biomass degrading machinery and transcriptional response in this fungus, its molecular response to lignocellulose-derived aromatic compounds has not been studied so far. However, the potential of D. squalens for diverse aromatic conversions has been indicated (Daly et al, 2018; Marinović et al, 2018), but more detailed studies are needed to advance our understanding of these processes before assessing their potential in biotechnological applications.…”

Dichomitus squalens partially tailors its molecular responses to the composition of solid wood

“…Small molecule inducers other than those derived from mannan or xylan could be inducing the MCs and XCs in different wood types participating in regulation of gene expression. We recently reported cellobiose as a potent inducer of a broad range of CAZymes, including XCs and MCs, in the same strain of D. squalens (Casado López et al ., ). Cellobiose, which is released during degradation of cellulose, was detected in the exo‐metabolomics (Supporting Information Table S5).…”

Draft Genome Sequences of Three Monokaryotic Isolates of the White-Rot Basidiomycete Fungus Dichomitus squalens

“…It is mainly found on softwoods (2, 3) and has an extensive repertoire of lignocellulose-degrading enzymes (4–6). Two of the genome-sequenced monokaryons, CBS463.89 and CBS464.89, are derived from the well-studied Polish dikaryon FBCC312 (CBS432.34) (4, 6–11), while OM18370.1 is derived from the Finnish dikaryon OM18370 (CBS139088).…”