The effect of the carbon source on ammonium regulation in Aspergillus nidulans

1974 ◽  
Vol 128 (1) ◽  
pp. 95-98 ◽  
Author(s):  
J. R. Kinghorn ◽  
J. A. Pateman
Keyword(s):  
Carbon Source ◽  
Aspergillus Nidulans ◽  
Ammonium Regulation

scholarly journals Regulation ofAspergillus nidulansCreA-Mediated Catabolite Repression by the F-Box Proteins Fbx23 and Fbx47

mBio ◽  
2018 ◽  
Vol 9 (3) ◽  
Author(s):  
Leandro José de Assis ◽  
Mevlut Ulas ◽  
Laure Nicolas Annick Ries ◽  
Nadia Ali Mohamed El Ramli ◽  
Ozlem Sarikaya-Bayram ◽  
...  
Keyword(s):  
Carbon Source ◽  
Aspergillus Nidulans ◽  
Ubiquitin Ligase ◽  
Catabolite Repression ◽  
Carbon Catabolite Repression ◽  
26S Proteasome ◽  
Xylanase Production ◽  
Content Type ◽  
Regulatory Pathways ◽  
Ubiquitin Ligase Complex

ABSTRACTThe attachment of one or more ubiquitin molecules by SCF (Skp–Cullin–F-box) complexes to protein substrates targets them for subsequent degradation by the 26S proteasome, allowing the control of numerous cellular processes. Glucose-mediated signaling and subsequent carbon catabolite repression (CCR) are processes relying on the functional regulation of target proteins, ultimately controlling the utilization of this carbon source. In the filamentous fungusAspergillus nidulans, CCR is mediated by the transcription factor CreA, which modulates the expression of genes encoding biotechnologically relevant enzymes. Although CreA-mediated repression of target genes has been extensively studied, less is known about the regulatory pathways governing CCR and this work aimed at further unravelling these events. The Fbx23 F-box protein was identified as being involved in CCR and the Δfbx23mutant presented impaired xylanase production under repressing (glucose) and derepressing (xylan) conditions. Mass spectrometry showed that Fbx23 is part of an SCF ubiquitin ligase complex that is bridged via the GskA protein kinase to the CreA-SsnF-RcoA repressor complex, resulting in the degradation of the latter under derepressing conditions. Upon the addition of glucose, CreA dissociates from the ubiquitin ligase complex and is transported into the nucleus. Furthermore, casein kinase is important for CreA function during glucose signaling, although the exact role of phosphorylation in CCR remains to be determined. In summary, this study unraveled novel mechanistic details underlying CreA-mediated CCR and provided a solid basis for studying additional factors involved in carbon source utilization which could prove useful for biotechnological applications.IMPORTANCEThe production of biofuels from plant biomass has gained interest in recent years as an environmentally friendly alternative to production from petroleum-based energy sources. Filamentous fungi, which naturally thrive on decaying plant matter, are of particular interest for this process due to their ability to secrete enzymes required for the deconstruction of lignocellulosic material. A major drawback in fungal hydrolytic enzyme production is the repression of the corresponding genes in the presence of glucose, a process known as carbon catabolite repression (CCR). This report provides previously unknown mechanistic insights into CCR through elucidating part of the protein-protein interaction regulatory system that governs the CreA transcriptional regulator in the reference organismAspergillus nidulansin the presence of glucose and the biotechnologically relevant plant polysaccharide xylan.

scholarly journals Regulation of the acuF Gene, Encoding Phosphoenolpyruvate Carboxykinase in the Filamentous Fungus Aspergillus nidulans

2002 ◽  
Vol 184 (1) ◽  
pp. 183-190 ◽  
Author(s):  
Michael J. Hynes ◽  
Oliver W. Draht ◽  
Meryl A. Davis
Keyword(s):  
Carbon Source ◽  
Aspergillus Nidulans ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Carbon Sources ◽  
Tca Cycle ◽  
Northern Blotting ◽  
Gene Encoding ◽  
The Tca Cycle ◽  
Key Enzyme ◽  
Acetate Utilization

ABSTRACT Phosphoenolpyruvate carboxykinase (PEPCK) is a key enzyme required for gluconeogenesis when microorganisms grow on carbon sources metabolized via the tricarboxylic acid (TCA) cycle. Aspergillus nidulans acuF mutants isolated by their inability to use acetate as a carbon source specifically lack PEPCK. The acuF gene has been cloned and shown to encode a protein with high similarity to PEPCK from bacteria, plants, and fungi. The regulation of acuF expression has been studied by Northern blotting and by the construction of lacZ fusion reporters. Induction by acetate is abolished in mutants unable to metabolize acetate via the TCA cycle, and induction by amino acids metabolized via 2-oxoglutarate is lost in mutants unable to form 2-oxoglutarate. Induction by acetate and proline is not additive, consistent with a single mechanism of induction. Malate and succinate result in induction, and it is proposed that PEPCK is controlled by a novel mechanism of induction by a TCA cycle intermediate or derivative, thereby allowing gluconeogenesis to occur during growth on any carbon source metabolized via the TCA cycle. It has been shown that the facB gene, which mediates acetate induction of enzymes specifically required for acetate utilization, is not directly involved in PEPCK induction. This is in contrast to Saccharomyces cerevisiae, where Cat8p and Sip4p, homologs of FacB, regulate PEPCK as well as the expression of other genes necessary for growth on nonfermentable carbon sources in response to the carbon source present. This difference in the control of gluconeogenesis reflects the ability of A. nidulans and other filamentous fungi to use a wide variety of carbon sources in comparison with S. cerevisiae. The acuF gene was also found to be subject to activation by the CCAAT binding protein AnCF, a protein homologous to the S. cerevisiae Hap complex and the mammalian NFY complex.

scholarly journals Ras GTPase-Activating Protein Regulation of Actin Cytoskeleton and Hyphal Polarity in Aspergillus nidulans

2007 ◽  
Vol 7 (1) ◽  
pp. 141-153 ◽  
Author(s):  
Laura Harispe ◽  
Cecilia Portela ◽  
Claudio Scazzocchio ◽  
Miguel A. Peñalva ◽  
Lisette Gorfinkiel
Keyword(s):  
Carbon Source ◽  
Actin Cytoskeleton ◽  
Aspergillus Nidulans ◽  
Fluorescent Protein ◽  
Protein Domain ◽  
Ras Signaling ◽  
Wild Type ◽  
Gtpase Activating Protein ◽  
Ras Gtpase ◽  
Polarity Establishment

ABSTRACT Aspergillus nidulans gapA1, a mutation leading to compact, fluffy colonies and delayed polarity establishment, maps to a gene encoding a Ras GTPase-activating protein. Domain organization and phylogenetic analyses strongly indicate that GapA regulates one or more “true” Ras proteins. A gapAΔ strain is viable. gapA colonies are more compact than gapA1 colonies and show reduced conidiation. gapAΔ strains have abnormal conidiophores, characterized by the absence of one of the two layers of sterigmata seen in the wild type. gapA transcript levels are very low in conidia but increase during germination and reach their maximum at a time coincident with germ tube emergence. Elevated levels persist in hyphae. In germinating conidiospores, gapAΔ disrupts the normal coupling of isotropic growth, polarity establishment, and mitosis, resulting in a highly heterogeneous cell population, including malformed germlings and a class of giant cells with no germ tubes and a multitude of nuclei. Unlike wild-type conidia, gapAΔ conidia germinate without a carbon source. Giant multinucleated spores and carbon source-independent germination have been reported in strains carrying a rasA dominant active allele, indicating that GapA downregulates RasA. gapAΔ cells show a polarity maintenance defect characterized by apical swelling and subapical branching. The strongly polarized wild-type F-actin distribution is lost in gapAΔ cells. As GapA-green fluorescent protein shows cortical localization with strong predominance at the hyphal tips, we propose that GapA-mediated downregulation of Ras signaling at the plasma membrane of these tips is involved in the polarization of the actin cytoskeleton that is required for hyphal growth and, possibly, for asexual morphogenesis.

scholarly journals Ammonium Regulation in Aspergillus nidulans

1973 ◽  
Vol 114 (3) ◽  
pp. 943-950 ◽  
Author(s):  
J. A. Pateman ◽  
J. R. Kinghorn ◽  
Etta Dunn ◽  
E. Forbes
Keyword(s):  
Aspergillus Nidulans ◽  
Ammonium Regulation

scholarly journals Generation and Phenotypic Characterization of Aspergillus nidulans Methylisocitrate Lyase Deletion Mutants: Methylisocitrate Inhibits Growth and Conidiation

2005 ◽  
Vol 71 (9) ◽  
pp. 5465-5475 ◽  
Author(s):  
Matthias Brock
Keyword(s):  
Carbon Source ◽  
Aspergillus Nidulans ◽  
Isocitrate Dehydrogenase ◽  
Genomic Sequence ◽  
Competitive Inhibition ◽  
Carbon Sources ◽  
Inhibitory Effect ◽  
Phenotypic Characterization ◽  
Deletion Mutants ◽  
Main Carbon Source

ABSTRACT Propionate is a very abundant carbon source in soil, and many microorganisms are able to use this as the sole carbon source. Nevertheless, propionate not only serves as a carbon source for filamentous fungi but also acts as a preservative when added to glucose containing media. To solve this contradiction between carbon source and preservative effect, propionate metabolism of Aspergillus nidulans was studied and revealed the methylcitrate cycle as the responsible pathway. Methylisocitrate lyase is one of the key enzymes of that cycle. It catalyzes the cleavage of methylisocitrate into succinate and pyruvate and completes the α-oxidation of propionate. Previously, methylisocitrate lyase was shown to be highly specific for the substrate (2R,3S)-2-methylisocitrate. Here, the identification of the genomic sequence of the corresponding gene and the generation of deletion mutants is reported. Deletion mutants did not grow on propionate as sole carbon and energy source and were severely inhibited during growth on alternative carbon sources, when propionate was present. The strongest inhibitory effect was observed, when glycerol was the main carbon source, followed by glucose and acetate. In addition, asexual conidiation was strongly impaired in the presence of propionate. These effects might be caused by competitive inhibition of the NADP-dependent isocitrate dehydrogenase, because the Ki of (2R,3S)-2-methylisocitrate, the product of the methylcitrate cycle, on NADP-dependent isocitrate dehydrogenase was determined as 1.55 μM. Other isomers had no effect on enzymatic activity. Therefore, methylisocitrate was identified as a potential toxic compound for cellular metabolism.

Phosphatidylinositol phospholipase C mediates carbon sensing and vegetative nuclear duplication rates in Aspergillus nidulans

2011 ◽  
Vol 57 (7) ◽  
pp. 611-616 ◽  
Author(s):  
Ana Paula de Figueiredo Conte Vanzela ◽  
Suraia Said ◽  
Rolf Alexander Prade
Keyword(s):  
Molecular Weight ◽  
Carbon Source ◽  
Phospholipase C ◽  
Aspergillus Nidulans ◽  
Nuclear Division ◽  
Deficient Mutant ◽  
Wild Type ◽  
Pectinolytic Enzymes ◽  
In The Wild ◽  
Phosphatidylinositol Phospholipase C

In this work, we disrupted one of three putative phosphatidylinositol phospholipase C genes of Aspergillus nidulans and studied its effect on carbon source sensing linked to vegetative mitotic nuclear division. We showed that glucose does not affect nuclear division rates during early vegetative conidial germination (6–7 h) in either the wild type or the plcA-deficient mutant. Only after 8 h of cultivation on glucose did the mutant strain present some decrease in nuclear duplication. However, decreased nuclear division rates were observed in the wild type when cultivated in media amended with polypectate, whereas our plcA-deficient mutant did not show slow nuclear duplication rates when grown on this carbon source, even though it requires induction and secretion of multiple pectinolytic enzymes to be metabolized. Thus, plcA appears to be directly linked to high-molecular-weight carbon source sensing.

scholarly journals The Effects of the Carbon Source on Glutamate Dehydrogenase Activities in Aspergillus nidulans

Microbiology ◽  
2000 ◽  
Vol 81 (1) ◽  
pp. 165-170 ◽  
Author(s):  
M. J. Hynes
Keyword(s):  
Protein Synthesis ◽  
Carbon Source ◽  
Glutamate Dehydrogenase ◽  
Aspergillus Nidulans ◽  
Nitrogen Metabolism ◽  
Wild Type Strain ◽  
Protein Synthesis Inhibitors ◽  
Carbon And Nitrogen ◽  
Glutamate Dehydrogenase Activity ◽  
Carbon And Nitrogen Metabolism

The NADP-specific glutamate dehydrogenase (NADP-GDH) activity of Aspergillus nidulans was rapidly lost from cultures starved for a carbon source. This loss of NADP-GDH was blocked by protein synthesis inhibitors. Glutamate repressed NADP-GDH but did not cause rapid loss of activity. Since NADP-GDH is involved in the participation of ammonium in the regulation of nitrogen metabolism, the loss of NADP-GDH activity accompanying carbon starvation may be important in the interaction between carbon and nitrogen metabolism. Increased NAD specific glutamate dehydrogenase activity (NAD-GDH) was observed when mycelium was transferred to medium lacking glucose. The increase in NAD-GDH activity was greatest when glutamate was present. Protein synthesis inhibitors did not prevent this increase in activity. Two mutants, amdT102 and amdT19, which are altered in regulation of nitrogen metabolism, are similar to the wild-type strain with regard to regulation of NADP-GDH and NAD-GDH.

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