Regulation of the glaA gene of Aspergillus niger

Fowler, Timothy; Berka, Randy M.; Ward, Michael P.

doi:10.1007/bf00327025

Cited by 99 publications

(57 citation statements)

References 18 publications

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“…7(a, b) that much more glucoamylase (about 30 times) was produced on maltodextrin as limiting carbon source than on xylose. This was expected, since maltodextrin highly induces the expression of the glaA gene, while xylose strongly represses it (Fowler et al, 1990). Overproduction of glucoamylase by transformant Bl could be clearly observed when maltodextrin was used as sole carbon source.…”

Section: Growth and Glucoamylase Production In The Recycling Fermentermentioning

confidence: 82%

Growth and product formation in chemostat and recycling cultures by Aspergillus niger N402 and a glucoamylase overproducing transformant, provided with multiple copies of the glaA gene

Schrickx

Krave

Verdoes³

et al. 1993

Journal of General Microbiology

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Continuous and recycling cultures were carried out with Aspergillus niger N402 wild-type and a glucoamylase overproducing transformant to investigate growth and product formation characteristics. In shake flask cultures, the amount of glucoamylase produced by the transformant was about five times more than by the wild-type strain. In contrast with these results, a twofold overproduction was found in glucose-limited continuous cultures, while no overproduction was found under maltodextin-limitation. Two regions of specific growth rates could be distinguished, one at specific growth rates lower (domain I) and one at specific growth rates higher than 0.12 h-' (domain 11). In domain I changes in mycelium morphology and conidia formation were observed. It has been concluded that maintenance requirements are dependent on the specific growth rate over the whole range of measured growth rates. The deviation in linearity in the linear equation of substrate utilization, caused by this phenomenon, should be considered when continuous cultures with filamentous fungi are performed. In recycling cultures, xylose as limiting carbon source repressed glucoamylase production very strongly. Under maltodextrinlimitation a fivefold overproduction was found. After about 150 h, the total amount of glucoamylase produced was still increasing, while total amount of product, measured as carbon, remained constant. After this time no increase in the amount of biomass formed was observed. These results suggest autolysis and cryptic growth taking place in a recycling fermenter and cell death rate equalling growth rate.

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Section: Growth and Glucoamylase Production In The Recycling Fermentermentioning

confidence: 82%

Growth and product formation in chemostat and recycling cultures by Aspergillus niger N402 and a glucoamylase overproducing transformant, provided with multiple copies of the glaA gene

Schrickx

Krave

Verdoes³

et al. 1993

Journal of General Microbiology

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“…Using overlap extension techniques (24), precise fusions were obtained between the Aspergillus niger glucoamylase secretion signal (6,16) and the cDNA coding region of mature GLOX (27) (Fig. 1).…”

Section: Methodsmentioning

confidence: 99%

Phanerochaete chrysosporium glyoxal oxidase is encoded by two allelic variants: structure, genomic organization, and heterologous expression of glx1 and glx2

et al. 1995

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A cDNA clone (glx-2c) encoding glyoxal oxidase (GLOX) was isolated from a Phanerochaete chrysosporium gt11 library, and its nucleotide sequence was shown to be distinct from that of the previously described clone glx-1c (P. J. Kersten and D. Cullen, Proc. Natl. Acad. Sci. USA 90:7411-7413, 1993). Genomic clones corresponding to both cDNAs were also isolated and sequenced. Overall nucleotide sequence identity was 98%, and the predicted proteins differed by a single residue: Lys-3087Thr-308. Analyses of parental dikaryotic strain BKM-F-1767 and homokaryotic progeny firmly established allelism for these structural variants. Southern blots of pulsed-field gels localized the GLOX gene (glx) to a dimorphic chromosome separate from the peroxidase and cellobiohydrolase genes of P. chrysosporium. Controlled expression of active GLOX was obtained from Aspergillus nidulans transformants when glx-1c was fused to the promoter and secretion signal of the A. niger glucoamylase gene. The GLOX isozyme corresponding to glx-2c was also efficiently secreted by A. nidulans following site-specific mutagenesis of the expression vector at codon 308 of glx-1c.The white rot fungus Phanerochaete chrysosporium has been extensively studied for its lignin-degrading ability (29). P. chrysosporium secretes three known classes of extracellular enzymes under ligninolytic (secondary metabolic) conditions in defined glucose media: glyoxal oxidase (GLOX), lignin peroxidases (LiPs), and manganese peroxidases (MnPs). GLOX is a source of the extracellular H 2 O 2 that is required for the oxidations catalyzed by the ligninolytic peroxidases. In nutrientlimited P. chrysosporium cultures, the 68-kDa glycoprotein appears as two isozyme forms of pI 4.7 and 4.9. The purification, physical characteristics, and kinetics of GLOX have been reported (26,28).Multiple roles for GLOX in lignocellulose degradation by Phanerochaete spp. are suggested by several lines of evidence. In addition to the obvious function of peroxide supply, modulation of GLOX activity in vitro supports a role in extracellular regulation of ligninolytic activity in vivo. Purified GLOX is inactive unless activated by a coupled peroxidase system including both peroxidase and peroxidase substrate. The molecular basis for this extracellular regulation has not been elucidated. Furthermore, GLOX substrate production in vivo is likely to involve multiple metabolic pathways. Substrates for purified GLOX include formaldehyde, acetaldehyde, glycolaldehyde, glyoxal, glyoxylic acid, dihydroxyacetone, glyceraldehyde, and methylglyoxal. Both glyoxal and methylglyoxal have been detected in ligninolytic cultures, but the derivation and the full complement of physiological substrates from carbohydrate metabolism are still under investigation. Interestingly, products produced by lignin peroxidase activity on lignin model compounds are also substrates for GLOX; an efficient sequence of oxidations (glycolaldehyde to glyoxal to glyoxylate to oxalate) is catalyzed (23). This finding suggests that ligninolysis ca...

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“…This promoter is repressed on xylose but induced on maltose (Fowler et al ., 1990). As a control, sGFP was placed under control of the constitutive gpdA promoter.…”

Section: Glaa Is Differentially Expressed In the Exploration Zone Of mentioning

confidence: 99%

Hyphal differentiation in the exploring mycelium of Aspergillus niger

Vinck

Terlou

Pestman

et al. 2005

Molecular Microbiology

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SummaryMycelial fungi play a central role in element cycling in nature by degrading dead organic material such as wood. Fungal colonization of a substrate starts with the invasion of exploring hyphae. These hyphae secrete enzymes that convert the organic material into small molecules that can be taken up by the fungus to serve as nutrients. Using green fluorescent protein (GFP) as a reporter, we show for the first time that exploring hyphae of Aspergillus niger differentiate with respect to enzyme secretion; some strongly express the glucoamylase gene glaA , while others hardly express it at all. When a cytoplasmic GFP was used, 27% of the exploring hyphae of a 5-day-old colony belonged to the low expressing hyphae. By fusing GFP to glucoamylase and by introducing an ER retention signal, this number increased to 50%. This difference is due to cytoplasmic streaming of the reporter in the former case, as was shown by using a photo-activatable GFP. Our findings indicate that a fungal mycelium is highly differentiated, especially when taking into account that hyphae in the exploration zone were exposed to the same nutritional conditions.

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Regulation of the glaA gene of Aspergillus niger

Cited by 99 publications

References 18 publications

Growth and product formation in chemostat and recycling cultures by Aspergillus niger N402 and a glucoamylase overproducing transformant, provided with multiple copies of the glaA gene

Growth and product formation in chemostat and recycling cultures by Aspergillus niger N402 and a glucoamylase overproducing transformant, provided with multiple copies of the glaA gene

Phanerochaete chrysosporium glyoxal oxidase is encoded by two allelic variants: structure, genomic organization, and heterologous expression of glx1 and glx2

Hyphal differentiation in the exploring mycelium of Aspergillus niger

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