title: d-Xylose concentration-dependent hydrolase expression profiles and the function of CreA and XlnR in Aspergillus niger.
abstract: Aspergillus niger is an important organism for the production of industrial enzymes such as hemicellulases and pectinases. The xylan-backbone monomer, d-xylose, is an inducing substance for the coordinate expression of a large number of polysaccharide-degrading enzymes. In this study, the responses of 22 genes to low (1 mM) and high (50 mM) d-xylose concentrations were investigated. These 22 genes encode enzymes that function as xylan backbone-degrading enzymes, accessory enzymes, cellulose-degrading enzymes, or enzymes involved in the pentose catabolic pathway in A. niger. Notably, genes encoding enzymes that have a similar function (e.g., xylan backbone degradation) respond in a similar manner to different concentrations of d-xylose. Although low d-xylose concentrations provoke the greatest change in transcript levels, in particular, for hemicellulase-encoding genes, transcript formation in the presence of high concentrations of d-xylose was also observed. Interestingly, a high d-xylose concentration is favorable for certain groups of genes. Furthermore, the repressing influence of CreA on the transcription and transcript levels of a subset of these genes was observed regardless of whether a low or high concentration of d-xylose was used. Interestingly, the decrease in transcript levels of certain genes on high d-xylose concentrations is not reflected by the transcript level of their activator, XlnR. Regardless of the d-xylose concentration applied and whether CreA was functional, xlnR was constitutively expressed at a low level.
authors.affiliation: Fungal Systems Biology, Laboratory of Systems and Synthetic Biology, Wageningen University, Wageningen, The Netherlands.
authors.forename: Astrid R
authors.initials: AR
authors.lastname: Mach-Aigner
authors.forename: Jimmy
authors.initials: J
authors.lastname: Omony
authors.forename: Birgit
authors.initials: B
authors.lastname: Jovanovic
authors.forename: Anton J B
authors.initials: AJ
authors.lastname: van Boxtel
authors.forename: Leo H
authors.initials: LH
authors.lastname: de Graaff
mesh_terms: D001234:Aspergillus niger / Q000201:enzymology* / Q000378:metabolism*; D005656:Fungal Proteins / Q000378:metabolism*; D020869:Gene Expression Profiling; D015971:Gene Expression Regulation, Enzymologic; D015966:Gene Expression Regulation, Fungal; D006867:Hydrolases / Q000378:metabolism*; D012097:Repressor Proteins / Q000378:metabolism*; D015534:Trans-Activators / Q000378:metabolism*; D014994:Xylose / Q000378:metabolism*
chemical_list: D005656:Fungal Proteins; D012097:Repressor Proteins; D015534:Trans-Activators; C115443:XlnR protein, Aspergillus; D014994:Xylose; D006867:Hydrolases