title: Database mining and transcriptional analysis of genes encoding inulin-modifying enzymes of Aspergillus niger.
abstract: As a soil fungus, Aspergillus niger can metabolize a wide variety of carbon sources, employing sets of enzymes able to degrade plant-derived polysaccharides. In this study the genome sequence of A. niger strain CBS 513.88 was surveyed, to analyse the gene/enzyme network involved in utilization of the plant storage polymer inulin, and of sucrose, the substrate for inulin synthesis in plants. In addition to three known activities, encoded by the genes suc1 (invertase activity; designated sucA), inuE (exo-inulinase activity) and inuA/inuB (endo-inulinase activity), two new putative invertase-like proteins were identified. These two putative proteins lack N-terminal signal sequences and therefore are expected to be intracellular enzymes. One of these two genes, designated sucB, is expressed at a low level, and its expression is up-regulated when A. niger is grown on sucrose- or inulin-containing media. Transcriptional analysis of the genes encoding the sucrose- (sucA) and inulin-hydrolysing enzymes (inuA and inuE) indicated that they are similarly regulated and all strongly induced on sucrose and inulin. Analysis of a DeltacreA mutant strain of A. niger revealed that expression of the extracellular inulinolytic enzymes is under control of the catabolite repressor CreA. Expression of the inulinolytic enzymes was not induced by fructose, not even in the DeltacreA background, indicating that fructose did not act as an inducer. Evidence is provided that sucrose, or a sucrose-derived intermediate, but not fructose, acts as an inducer for the expression of inulinolytic genes in A. niger.
authors.affiliation: Institute of Biology Leiden, Leiden University, Fungal Genetics Research Group, Wassenaarseweg 64, 2333 AL Leiden, The Netherlands.
authors.forename: Xiao-Lian
authors.initials: XL
authors.lastname: Yuan
authors.affiliation: Centre for Carbohydrate Bioprocessing TNO-University of Groningen, Kerklaan 30, 9751 NN Haren, The Netherlands.|Department of Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute (GBB), University of Groningen, Kerklaan 30, 9751 NN Haren, The Netherlands.
authors.forename: Coenie
authors.initials: C
authors.lastname: Goosen
authors.affiliation: Microbiology, Fungal Genomics Group, Wageningen University, Dreijenlaan 2, 6703 HA Wageningen, The Netherlands.
authors.forename: Harrie
authors.initials: H
authors.lastname: Kools
authors.affiliation: TNO Quality of Life, Business Unit Innovative Ingredients and Products, Rouaanstraat 27, 9723 CC Groningen, The Netherlands.|Centre for Carbohydrate Bioprocessing TNO-University of Groningen, Kerklaan 30, 9751 NN Haren, The Netherlands.
authors.forename: Marc J E C
authors.initials: MJEC
authors.lastname: van der Maarel
authors.affiliation: Institute of Biology Leiden, Leiden University, Fungal Genetics Research Group, Wassenaarseweg 64, 2333 AL Leiden, The Netherlands.
authors.forename: Cees A M J J
authors.initials: CAMJJ
authors.lastname: van den Hondel
authors.affiliation: Centre for Carbohydrate Bioprocessing TNO-University of Groningen, Kerklaan 30, 9751 NN Haren, The Netherlands.|Department of Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute (GBB), University of Groningen, Kerklaan 30, 9751 NN Haren, The Netherlands.
authors.forename: Lubbert
authors.initials: L
authors.lastname: Dijkhuizen
authors.affiliation: TNO Quality of Life, Business Unit Microbiology, Utrechtseweg 48, 3500 AJ Zeist, The Netherlands.|Institute of Biology Leiden, Leiden University, Fungal Genetics Research Group, Wassenaarseweg 64, 2333 AL Leiden, The Netherlands.
authors.forename: Arthur F J
authors.initials: AFJ
authors.lastname: Ram
mesh_terms: D001234:Aspergillus niger / Q000201:enzymology* / Q000235:genetics* / Q000378:metabolism; D015152:Blotting, Northern; D019295:Computational Biology; D004271:DNA, Fungal / Q000737:chemistry / Q000235:genetics; D005632:Fructose; D015966:Gene Expression Regulation, Fungal; D016681:Genome, Fungal; D007444:Inulin / Q000378:metabolism*; D008969:Molecular Sequence Data; D010802:Phylogeny; D021382:Protein Sorting Signals / Q000235:genetics; D012331:RNA, Fungal / Q000032:analysis / Q000235:genetics; D012333:RNA, Messenger / Q000032:analysis / Q000235:genetics; D017386:Sequence Homology, Amino Acid; D013395:Sucrose / Q000378:metabolism; D014158:Transcription, Genetic; D043324:beta-Fructofuranosidase / Q000235:genetics*
chemical_list: D004271:DNA, Fungal; D021382:Protein Sorting Signals; D012331:RNA, Fungal; D012333:RNA, Messenger; D005632:Fructose; D013395:Sucrose; D007444:Inulin; D043324:beta-Fructofuranosidase