title: D-Xylose as a repressor or inducer of xylanase expression in Hypocrea jecorina (Trichoderma reesei).
abstract: For Hypocrea jecorina (anamorph Trichoderma reesei), a filamentous fungus used for hydrolase production in different industries, it has been a long-term practice to use d-xylose as an inducing substance. We demonstrate in this study that the degree of xylanase-encoding gene induction strictly depends on the concentration of d-xylose, which was found to be optimal from 0.5 to 1 mM for 3 h of cultivation. At higher concentrations of d-xylose, a reduced level of xylanase gene expression was observed. In the present study, we also provide evidence that the d-xylose concentration-dependent induction is antagonized by carbon catabolite repressor 1. This repressor mediates its influence on d-xylose indirectly, by reducing the expression of xylanase regulator 1, the main activator of most hydrolase-encoding genes. Additionally, a direct influence of the repressor on xylanase 1 expression in the presence of d-xylose was found. Furthermore, we show that d-xylose reductase 1 is needed to metabolize d-xylose to achieve full induction of xylanase expression. Finally, a strain which expresses xylanase regulator 1 at a constant level was used to partially overcome the negative influence exerted by carbon catabolite repressor 1 on d-xylose.
authors.affiliation: Gene Technology, Department of Gene Technology and Applied Biochemistry, Institute of Chemical Engineering, TU Wien, Getreidemarkt 9/166/5/2, A-1060 Vienna, Austria.
authors.forename: Astrid R
authors.initials: AR
authors.lastname: Mach-Aigner
authors.forename: Marion E
authors.initials: ME
authors.lastname: Pucher
authors.forename: Robert L
authors.initials: RL
authors.lastname: Mach
mesh_terms: D000449:Aldehyde Reductase / Q000378:metabolism; D043364:Endo-1,4-beta Xylanases / Q000096:biosynthesis*; D005656:Fungal Proteins / Q000096:biosynthesis*; D015971:Gene Expression Regulation, Enzymologic; D015966:Gene Expression Regulation, Fungal; D035901:Hypocrea / Q000201:enzymology* / Q000378:metabolism; D008954:Models, Biological; D012097:Repressor Proteins / Q000378:metabolism; D014994:Xylose / Q000378:metabolism*
chemical_list: D005656:Fungal Proteins; D012097:Repressor Proteins; D014994:Xylose; D000449:Aldehyde Reductase; D043364:Endo-1,4-beta Xylanases