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Aspergillus niger RhaR, a regulator involved in L-rhamnose release and catabolism

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Author: Gruben, B.S. · Zhou, M. · Wiebenga, A. · Ballering, J. · Overkamp, K.M. · Punt, P.J. · Vries, R.P. de
Type:article
Date:2014
Source:Applied Microbiology and Biotechnology, 12, 98, 5531-5540
Identifier: 513327
doi: doi:10.1007/s00253-014-5607-9
Keywords: Biology · Aspergillus niger · L-rhamnose catabolism · L-rhamnose release · Pectin degradation · Transcriptional regulation · Aspergillus · Encoding (symbols) · Industrial applications · Metabolism · Down-regulation · Filamentous fungi · L-rhamnose · Regulatory genes · Rhamnogalacturonan-I · Small reduction · Gene encoding · Galacturonic acid · Pectin · Pectin lyase · Polygalacturonase · Rhamnose · Biodegradation · Catabolism · Enzyme activity · Genome · Growth rate · Amino acid sequence · Carbohydrate metabolism · Carbon source · DNA flanking region · Fungal gene · Fungal genome · Fungal strain · Fungus culture · Fungus growth · Gene expression · Gene identification · Gene inactivation · Microarray analysis · Mycelium · Nonhuman · Orthology · Regulator gene · RhaR gene · Transcription regulation · Fungi · Food and Nutrition · Healthy Living · Life · MSB - Microbiology and Systems Biology · ELSS - Earth, Life and Social Sciences

Abstract

The genome of the filamentous fungus Aspergillus niger is rich in genes encoding pectinases, a broad class of enzymes that have been extensively studied due to their use in industrial applications. The sequencing of the A. niger genome provided more knowledge concerning the individual pectinolytic genes, but little is known about the regulatory genes involved in pectin degradation. Understanding regulation of the pectinolytic genes provides a tool to optimize the production of pectinases in this industrially important fungus. This study describes the identification and characterization of one of the activators of pectinase-encoding genes, RhaR. Inactivation of the gene encoding this regulator resulted in down-regulation of genes involved in the release of L-rhamnose from the pectin substructure rhamnogalacturonan I, as well as catabolism of this monosaccharide. The rhaR disruptant was unable to grow on L-rhamnose, but only a small reduction in growth on pectin was observed. This is likely caused by the presence of a second, so far unknown regulator that responds to the presence of D-galacturonic acid. © 2014 Springer-Verlag. Chemicals/CAS: galacturonic acid, 14982-50-4, 685-73-4; pectin, 9000-69-5; pectin lyase, 9033-35-6; polygalacturonase, 9023-92-1, 9032-75-1; rhamnose, 10485-94-6, 3615-41-6