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Khosravi C, Battaglia E, Kun RS, Dalhuijsen S, Visser J, Aguilar-Pontes MV, Zhou M, Heyman HM, Kim YM, Baker SE, de Vries RP. Blocking hexose entry into glycolysis activates alternative metabolic conversion of these sugars and upregulates pentose metabolism in Aspergillus nidulans. BMC Genomics 2018; 19:214. [PMID: 29566661 PMCID: PMC5863803 DOI: 10.1186/s12864-018-4609-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2017] [Accepted: 03/19/2018] [Indexed: 11/11/2022] Open
Abstract
Background Plant biomass is the most abundant carbon source for many fungal species. In the biobased industry fungi, are used to produce lignocellulolytic enzymes to degrade agricultural waste biomass. Here we evaluated if it would be possible to create an Aspergillus nidulans strain that releases, but does not metabolize hexoses from plant biomass. For this purpose, metabolic mutants were generated that were impaired in glycolysis, by using hexokinase (hxkA) and glucokinase (glkA) negative strains. To prevent repression of enzyme production due to the hexose accumulation, strains were generated that combined these mutations with a deletion in creA, the repressor involved in regulating preferential use of different carbon catabolic pathways. Results Phenotypic analysis revealed reduced growth for the hxkA1 glkA4 mutant on wheat bran. However, hexoses did not accumulate during growth of the mutants on wheat bran, suggesting that glucose metabolism is re-routed towards alternative carbon catabolic pathways. The creAΔ4 mutation in combination with preventing initial phosphorylation in glycolysis resulted in better growth than the hxkA/glkA mutant and an increased expression of pentose catabolic and pentose phosphate pathway genes. This indicates that the reduced ability to use hexoses as carbon sources created a shift towards the pentose fraction of wheat bran as a major carbon source to support growth. Conclusion Blocking the direct entry of hexoses to glycolysis activates alternative metabolic conversion of these sugars in A. nidulans during growth on plant biomass, but also upregulates conversion of other sugars, such as pentoses. Electronic supplementary material The online version of this article (10.1186/s12864-018-4609-x) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Claire Khosravi
- Fungal Physiology, Westerdijk Fungal Biodiversity Institute & Fungal Molecular Physiology, Utrecht University, Uppsalalaan 8, 3584, CT, Utrecht, The Netherlands
| | - Evy Battaglia
- Fungal Physiology, Westerdijk Fungal Biodiversity Institute & Fungal Molecular Physiology, Utrecht University, Uppsalalaan 8, 3584, CT, Utrecht, The Netherlands
| | - Roland S Kun
- Fungal Physiology, Westerdijk Fungal Biodiversity Institute & Fungal Molecular Physiology, Utrecht University, Uppsalalaan 8, 3584, CT, Utrecht, The Netherlands
| | - Sacha Dalhuijsen
- Microbiology, Utrecht University, Padualaan 8, 3584, CH, Utrecht, The Netherlands
| | - Jaap Visser
- Fungal Physiology, Westerdijk Fungal Biodiversity Institute & Fungal Molecular Physiology, Utrecht University, Uppsalalaan 8, 3584, CT, Utrecht, The Netherlands.,Fungal Genetics and Technology Consultancy, P.O. Box 396, 6700, AJ, Wageningen, The Netherlands
| | - María Victoria Aguilar-Pontes
- Fungal Physiology, Westerdijk Fungal Biodiversity Institute & Fungal Molecular Physiology, Utrecht University, Uppsalalaan 8, 3584, CT, Utrecht, The Netherlands
| | - Miaomiao Zhou
- Fungal Physiology, Westerdijk Fungal Biodiversity Institute & Fungal Molecular Physiology, Utrecht University, Uppsalalaan 8, 3584, CT, Utrecht, The Netherlands
| | - Heino M Heyman
- Earth and Biological Sciences Directorate, Pacific Northwest National Laboratory, Richland, WA, USA
| | - Young-Mo Kim
- Earth and Biological Sciences Directorate, Pacific Northwest National Laboratory, Richland, WA, USA
| | - Scott E Baker
- Earth and Biological Sciences Directorate, Pacific Northwest National Laboratory, Richland, WA, USA
| | - Ronald P de Vries
- Fungal Physiology, Westerdijk Fungal Biodiversity Institute & Fungal Molecular Physiology, Utrecht University, Uppsalalaan 8, 3584, CT, Utrecht, The Netherlands. .,Microbiology, Utrecht University, Padualaan 8, 3584, CH, Utrecht, The Netherlands.
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2
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Pérez EA, Fernández FJ, Fierro F, Mejía A, Marcos AT, Martín JF, Barrios-González J. Yeast HXK2 gene reverts glucose regulation mutation of penicillin biosynthesis in P. chrysogenum. Braz J Microbiol 2014; 45:873-83. [PMID: 25477921 PMCID: PMC4204972 DOI: 10.1590/s1517-83822014000300017] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2012] [Accepted: 03/14/2014] [Indexed: 11/25/2022] Open
Abstract
The mutant Penicillium chrysogenum strain dogR5, derived from strain AS-P-78, does not respond to glucose regulation of penicillin biosynthesis and β-galactosidase, and is partially deficient in D-glucose phosphorilating activity. We have transformed strain dogR5 with the (hexokinase) hxk2 gene from Saccharomyces cerevisiae. Transformants recovered glucose control of penicillin biosynthesis in different degrees, and acquired a hexokinase (fructose phosphorylating) activity absent in strains AS- P-78 and dogR5. Interestingly, they also recovered glucose regulation of β-galactosidase. On the other hand, glucokinase activity was affected in different ways in the transformants; one of which showed a lower activity than the parental dogR5, but normal glucose regulation of penicillin biosynthesis. Our results show that Penicillium chrysogenum AS-P-78 and dogR5 strains lack hexokinase, and suggest that an enzyme with glucokinase activity is involved in glucose regulation of penicillin biosynthesis and β-galactosidase, thus signaling glucose in both primary and secondary metabolism; however, catalytic and signaling activities seem to be independent.
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Affiliation(s)
- Edmundo A. Pérez
- Laboratorio de Ingeniería Genética y Metabolitos SecundariosDepartamento de BiotecnologíaUniversidad Autónoma MetropolitanaMexico D.F.MexicoLaboratorio de Ingeniería Genética y Metabolitos Secundarios, Departamento de Biotecnología, Universidad Autónoma Metropolitana, Mexico D.F., Mexico.
| | - Francisco J. Fernández
- Laboratorio de Ingeniería Genética y Metabolitos SecundariosDepartamento de BiotecnologíaUniversidad Autónoma MetropolitanaMexico D.F.MexicoLaboratorio de Ingeniería Genética y Metabolitos Secundarios, Departamento de Biotecnología, Universidad Autónoma Metropolitana, Mexico D.F., Mexico.
| | - Francisco Fierro
- Laboratorio de Ingeniería Genética y Metabolitos SecundariosDepartamento de BiotecnologíaUniversidad Autónoma MetropolitanaMexico D.F.MexicoLaboratorio de Ingeniería Genética y Metabolitos Secundarios, Departamento de Biotecnología, Universidad Autónoma Metropolitana, Mexico D.F., Mexico.
| | - Armando Mejía
- Laboratorio de Ingeniería Genética y Metabolitos SecundariosDepartamento de BiotecnologíaUniversidad Autónoma MetropolitanaMexico D.F.MexicoLaboratorio de Ingeniería Genética y Metabolitos Secundarios, Departamento de Biotecnología, Universidad Autónoma Metropolitana, Mexico D.F., Mexico.
| | - Ana T. Marcos
- Instituto de Biotecnología de LeónLeónSpainInstituto de Biotecnología de León, León, Spain.
| | - Juan F. Martín
- Instituto de Biotecnología de LeónLeónSpainInstituto de Biotecnología de León, León, Spain.
- Área de MicrobiologíaFacultad de Ciencias Biológicas y AmbientalesUniversidad de LeónLeónSpainÁrea de Microbiología, Facultad de Ciencias Biológicas y Ambientales, Universidad de León, León, Spain.
| | - Javier Barrios-González
- Laboratorio de Ingeniería Genética y Metabolitos SecundariosDepartamento de BiotecnologíaUniversidad Autónoma MetropolitanaMexico D.F.MexicoLaboratorio de Ingeniería Genética y Metabolitos Secundarios, Departamento de Biotecnología, Universidad Autónoma Metropolitana, Mexico D.F., Mexico.
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Sun J, Glass NL. Identification of the CRE-1 cellulolytic regulon in Neurospora crassa. PLoS One 2011; 6:e25654. [PMID: 21980519 PMCID: PMC3183063 DOI: 10.1371/journal.pone.0025654] [Citation(s) in RCA: 125] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2011] [Accepted: 09/09/2011] [Indexed: 12/15/2022] Open
Abstract
BACKGROUND In filamentous ascomycete fungi, the utilization of alternate carbon sources is influenced by the zinc finger transcription factor CreA/CRE-1, which encodes a carbon catabolite repressor protein homologous to Mig1 from Saccharomyces cerevisiae. In Neurospora crassa, deletion of cre-1 results in increased secretion of amylase and β-galactosidase. METHODOLOGY/PRINCIPAL FINDINGS Here we show that a strain carrying a deletion of cre-1 has increased cellulolytic activity and increased expression of cellulolytic genes during growth on crystalline cellulose (Avicel). Constitutive expression of cre-1 complements the phenotype of a N. crassa Δcre-1 strain grown on Avicel, and also results in stronger repression of cellulolytic protein secretion and enzyme activity. We determined the CRE-1 regulon by investigating the secretome and transcriptome of a Δcre-1 strain as compared to wild type when grown on Avicel versus minimal medium. Chromatin immunoprecipitation-PCR of putative target genes showed that CRE-1 binds to only some adjacent 5'-SYGGRG-3' motifs, consistent with previous findings in other fungi, and suggests that unidentified additional regulatory factors affect CRE-1 binding to promoter regions. Characterization of 30 mutants containing deletions in genes whose expression level increased in a Δcre-1 strain under cellulolytic conditions identified novel genes that affect cellulase activity and protein secretion. CONCLUSIONS/SIGNIFICANCE Our data provide comprehensive information on the CRE-1 regulon in N. crassa and contribute to deciphering the global role of carbon catabolite repression in filamentous ascomycete fungi during plant cell wall deconstruction.
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Affiliation(s)
- Jianping Sun
- Department of Plant and Microbial Biology, University of California, Berkeley, California, United States of America
| | - N. Louise Glass
- Department of Plant and Microbial Biology, University of California, Berkeley, California, United States of America
- * E-mail:
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García J, Torres N. Mathematical modelling and assessment of the pH homeostasis mechanisms in Aspergillus niger while in citric acid producing conditions. J Theor Biol 2011; 282:23-35. [DOI: 10.1016/j.jtbi.2011.04.028] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2010] [Revised: 04/16/2011] [Accepted: 04/23/2011] [Indexed: 11/29/2022]
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Max B, Salgado JM, Rodríguez N, Cortés S, Converti A, Domínguez JM. Biotechnological production of citric acid. Braz J Microbiol 2010; 41:862-75. [PMID: 24031566 PMCID: PMC3769771 DOI: 10.1590/s1517-83822010000400005] [Citation(s) in RCA: 101] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2010] [Accepted: 05/24/2010] [Indexed: 11/22/2022] Open
Abstract
This work provides a review about the biotechnological production of citric acid starting from the physicochemical properties and industrial applications, mainly in the food and pharmaceutical sectors. Several factors affecting citric acid fermentation are discussed, including carbon source, nitrogen and phosphate limitations, pH of culture medium, aeration, trace elements and morphology of the fungus. Special attention is paid to the fundamentals of biochemistry and accumulation of citric acid. Technologies employed at industrial scale such as surface or submerged cultures, mainly employing Aspergillus niger, and processes carried out with Yarrowia lipolytica, as well as the technology for recovering the product are also described. Finally, this review summarizes the use of orange peels and other by-products as feedstocks for the bioproduction of citric acid.
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Affiliation(s)
- Belén Max
- Department of Chemical Engineering, Sciences Faculty, University of Vigo (Campus Ourense), As Lagoas s/n, 32004 Ourense, Spain
| | - José Manuel Salgado
- Department of Chemical Engineering, Sciences Faculty, University of Vigo (Campus Ourense), As Lagoas s/n, 32004 Ourense, Spain
| | - Noelia Rodríguez
- Department of Chemical Engineering, Sciences Faculty, University of Vigo (Campus Ourense), As Lagoas s/n, 32004 Ourense, Spain
| | - Sandra Cortés
- Department of Chemical Engineering, Sciences Faculty, University of Vigo (Campus Ourense), As Lagoas s/n, 32004 Ourense, Spain
| | - Attilio Converti
- Laboratory of Agro-food Biotechnology, CITI-Tecnópole, Parque Tecnológico de Galicia, San Cibrao das Viñas, Ourense, Spain
| | - José Manuel Domínguez
- Department of Chemical Engineering, Sciences Faculty, University of Vigo (Campus Ourense), As Lagoas s/n, 32004 Ourense, Spain
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Aspergillus fumigatus catalytic glucokinase and hexokinase: expression analysis and importance for germination, growth, and conidiation. EUKARYOTIC CELL 2010; 9:1120-35. [PMID: 20453072 DOI: 10.1128/ec.00362-09] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Fungi contain several hexokinases, which are involved either in sugar phosphorylation or in carbon source sensing. Glucose and fructose phosphorylations appear to rely exclusively on glucokinase and hexokinase. Here, we characterized the catalytic glucokinase and hexokinase from the opportunistic human pathogen Aspergillus fumigatus and showed that both enzymes display different biochemical properties and play different roles during growth and development. Glucokinase efficiently activates glucose and mannose but activates fructose only to a minor extent. Hexokinase showed a high efficiency for fructose activation but also activated glucose and mannose. Transcript and activity determinations revealed high levels of glucokinase in resting conidia, whereas hexokinase was associated mainly with the mycelium. Consequentially, a glucokinase mutant showed delayed germination at low glucose concentrations, whereas colony growth was not overly affected. The deletion of hexokinase had only a minor impact on germination but reduced colony growth, especially on sugar-containing media. Transcript determinations from infected mouse lungs revealed the expression of both genes, indicating a contribution to virulence. Interestingly, a double-deletion mutant showed impaired growth not only on sugars but also on nonfermentable nutrients, and growth on gluconeogenic carbon sources was strongly suppressed in the presence of glucose. Furthermore, the glkA hxkA deletion affected cell wall integrity, implying that both enzymes contribute to the cell wall composition. Additionally, the absence of either enzyme deregulated carbon catabolite repression since mutants displayed an induction of isocitrate lyase activity during growth on glucose-ethanol medium. Therefore, both enzymes seem to be required for balancing carbon flux in A. fumigatus and are indispensable for growth under all nutritional conditions.
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Rui O, Hahn M. The Botrytis cinerea hexokinase, Hxk1, but not the glucokinase, Glk1, is required for normal growth and sugar metabolism, and for pathogenicity on fruits. Microbiology (Reading) 2007; 153:2791-2802. [PMID: 17660443 DOI: 10.1099/mic.0.2007/006338-0] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Hexose kinases play a central role in the initiation of sugar metabolism of living organisms and have also been implicated in carbon catabolite repression in yeasts and plants. In this study, the genes encoding glucokinase (Glk1) and hexokinase (Hxk1) from the plant-pathogenic ascomycete Botrytis cinerea were isolated and functionally characterized. Glk1-deficient mutants were indistinguishable from the wild-type in all growth parameters tested. In contrast, Deltahxk1 mutants lacking Hxk1 showed a pleiotropic growth defect. On artificial media, vegetative growth was retarded, and conidia formation strongly reduced. No or only marginal growth of Deltahxk1 mutants was observed when fructose, galactose, sucrose or sorbitol were used as carbon sources, and fructose inhibited growth of the mutant in the presence of other carbon sources. B. cinerea mutants containing hxk1 alleles with point mutations leading to enzymically inactive enzymes showed phenotypes similar to the Deltahxk1 disruption mutant, indicating that loss of hexose phosphorylation activity of Hxk1 is solely responsible for the pleiotropic growth defect. Virulence of the Deltahxk1 mutants was dependent on the plant tissue: on leaves, lesion formation was only slightly retarded compared to the wild-type, whereas only small lesions were formed on apples, strawberries and tomatoes. The low virulence of Deltahxk1 mutants on fruits was correlated with their high contents of sugars, in particular fructose. Heterologous expression of Hxk1 and Glk1 in yeast allowed their enzymic characterization, revealing kinetic properties similar to other fungal hexokinases and glucokinases. Both Deltaglk1 and Deltahxk1 mutants showed normal glucose repression of secreted lipase 1 activity, indicating that, in contrast to yeast, B. cinerea hexose kinases are not involved in carbon catabolite repression.
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Affiliation(s)
- Oliver Rui
- Phytopathology, Department of Biology, University of Kaiserslautern, 67653 Kaiserslautern, Germany
| | - Matthias Hahn
- Phytopathology, Department of Biology, University of Kaiserslautern, 67653 Kaiserslautern, Germany
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Papagianni M. Advances in citric acid fermentation by Aspergillus niger: biochemical aspects, membrane transport and modeling. Biotechnol Adv 2007; 25:244-63. [PMID: 17337335 DOI: 10.1016/j.biotechadv.2007.01.002] [Citation(s) in RCA: 226] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2006] [Revised: 01/11/2007] [Accepted: 01/11/2007] [Indexed: 11/18/2022]
Abstract
Citric acid is regarded as a metabolite of energy metabolism, of which the concentration will rise to appreciable amounts only under conditions of substantive metabolic imbalances. Citric acid fermentation conditions were established during the 1930s and 1940s, when the effects of various medium components were evaluated. The biochemical mechanism by which Aspergillus niger accumulates citric acid has continued to attract interest even though its commercial production by fermentation has been established for decades. Although extensive basic biochemical research has been carried out with A. niger, the understanding of the events relevant for citric acid accumulation is not completely understood. This review is focused on citric acid fermentation by A. niger. Emphasis is given to aspects of fermentation biochemistry, membrane transport in A. niger and modeling of the production process.
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Affiliation(s)
- Maria Papagianni
- Department of Hygiene and Technology of Food of Animal Origin, School of Veterinary Medicine, Aristotle University of Thessaloniki, Thessaloniki, Greece.
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Bernardo SMH, Gray KA, Todd RB, Cheetham BF, Katz ME. Characterization of regulatory non-catalytic hexokinases in Aspergillus nidulans. Mol Genet Genomics 2007; 277:519-32. [PMID: 17226029 DOI: 10.1007/s00438-006-0203-z] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2006] [Accepted: 12/12/2006] [Indexed: 11/30/2022]
Abstract
Hexokinases catalyse the first step in glucose metabolism and play a role in glucose sensing in mammals, plants and fungi. We describe a new class of hexokinases that appear to be solely regulatory in function. The Aspergillus nidulans hxkD gene (formerly named xprF) encodes a hexokinase-like protein. We constructed hxkDDelta gene disruption mutants which showed increased levels of extracellular protease in response to carbon starvation. The hxkDDelta mutations are not completely recessive, indicating that the level of the gene product is critical. Transcript levels of hxkD increase during carbon starvation and this response is not dependent on functional HxkD. A gene encoding a second atypical hexokinase (HxkC) was identified. The hxkCDelta gene disruption mutant exhibits a phenotype similar, but not identical, to hxkDDelta mutants. As with hxkD, mutations in hxkC are suppressed by loss-of-function mutations in xprG, which encodes a putative transcriptional activator involved in the response to nutrient limitation. We show that GFP-tagged HxkD was found only in nuclei suggesting a regulatory role for HxkD. GFP-tagged HxkC was associated with mitochondria. Homologs of hxkC and hxkD are conserved in multi-cellular fungi. Genes encoding atypical hexokinases are present in many genome sequence databases. Thus, non-catalytic hexokinases may be widespread.
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Affiliation(s)
- Stella M H Bernardo
- Molecular and Cellular Biology, University of New England, Armidale, NSW, Australia
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Fast response filter module with plug flow of filtrate for on-line sampling from submerged cultures of filamentous fungi. Anal Chim Acta 2004. [DOI: 10.1016/j.aca.2003.12.065] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Flipphi M, van de Vondervoort PJI, Ruijter GJG, Visser J, Arst HN, Felenbok B. Onset of carbon catabolite repression in Aspergillus nidulans. Parallel involvement of hexokinase and glucokinase in sugar signaling. J Biol Chem 2003; 278:11849-57. [PMID: 12519784 DOI: 10.1074/jbc.m209443200] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The role of hexose phosphorylating enzymes in the signaling of carbon catabolite repression was investigated in the filamentous fungus Aspergillus nidulans. A d-fructose non-utilizing, hexokinase-deficient (hxkA1, formerly designated frA1) strain was utilized to obtain new mutants lacking either glucokinase (glkA4) or both hexose kinases (hxkA1/glkA4). d-Glucose and d-fructose phosphorylation is completely abolished in the double mutant, which consequently cannot grow on either sugar. The glucokinase single mutant exhibits no nutritional deficiencies. Three repressible diagnostic systems, ethanol utilization (alcA and alcR genes), xylan degradation (xlnA), and acetate catabolism (facA), were analyzed in these hexose kinase mutants at the transcript level. Transcriptional repression by d-glucose is fully retained in the two single kinase mutants, whereas the hexokinase mutant is partially derepressed for d-fructose. Thus, hexokinase A and glucokinase A compensate each other for carbon catabolite repression by d-glucose in the single mutants. In contrast, both d-glucose and d-fructose repression are severely impaired for all three diagnostic systems in the double mutant. Unlike the situation in Saccharomyces cerevisiae, the hexose phosphorylating enzymes play parallel roles in glucose repression in A. nidulans.
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Affiliation(s)
- Michel Flipphi
- Institut de Génétique et Microbiologie, CNRS Unité Mixte de Recherche 8621, Université Paris-Sud XI, Centre d'Orsay, Bâtiment 409, F-91405 Orsay Cedex, France
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Kramarenko T, Karp H, Järviste A, Alamäe T. Sugar repression in the methylotrophic yeast Hansenula polymorpha studied by using hexokinase-negative, glucokinase-negative and double kinase-negative mutants. Folia Microbiol (Praha) 2001; 45:521-9. [PMID: 11501418 DOI: 10.1007/bf02818721] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
Two glucose-phosphorylating enzymes, a hexokinase phosphorylating both glucose and fructose, and a glucose-specific glucokinase were electrophoretically separated in the methylotrophic yeast Hansenula polymorpha. Hexokinase-negative, glucokinase-negative and double kinase-negative mutants were isolated in H. polymorpha by using mutagenesis, selection and genetic crosses. Regulation of synthesis of the sugar-repressed alcohol oxidase, catalase and maltase was studied in different hexose kinase mutants. In the wild type and in mutants possessing either hexokinase or glucokinase, glucose repressed the synthesis of maltase, alcohol oxidase and catalase. Glucose repression of alcohol oxidase and catalase was abolished in mutants lacking both glucose-phosphorylating enzymes (i.e. in double kinase-negative mutants). Thus, glucose repression in H. polymorpha cells requires a glucose-phosphorylating enzyme, either hexokinase or glucokinase. The presence of fructose-phosphorylating hexokinase in the cell was specifically needed for fructose repression of alcohol oxidase, catalase and maltase. Hence, glucose or fructose has to be phosphorylated in order to cause repression of the synthesis of these enzymes in H. polymorpha suggesting that sugar repression in this yeast therefore relies on the catalytic activity of hexose kinases.
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Affiliation(s)
- T Kramarenko
- Department of Genetics, Institute of Molecular and Cell Biology, University of Tartu, 51010 Tartu, Estonia
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Fillinger S, Chaveroche MK, van Dijck P, de Vries R, Ruijter G, Thevelein J, d'Enfert C. Trehalose is required for the acquisition of tolerance to a variety of stresses in the filamentous fungus Aspergillus nidulans. MICROBIOLOGY (READING, ENGLAND) 2001; 147:1851-1862. [PMID: 11429462 DOI: 10.1099/00221287-147-7-1851] [Citation(s) in RCA: 148] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Trehalose is a non-reducing disaccharide found at high concentrations in Aspergillus nidulans conidia and rapidly degraded upon induction of conidial germination. Furthermore, trehalose is accumulated in response to a heat shock or to an oxidative shock. The authors have characterized the A. nidulans tpsA gene encoding trehalose-6-phosphate synthase, which catalyses the first step in trehalose biosynthesis. Expression of tpsA in a Saccharomyces cerevisiae tps1 mutant revealed that the tpsA gene product is a functional equivalent of the yeast Tps1 trehalose-6-phosphate synthase. The A. nidulans tpsA-null mutant does not produce trehalose during conidiation or in response to various stress conditions. While germlings of the tpsA mutant show an increased sensitivity to moderate stress conditions (growth at 45 degrees C or in the presence of 2 mM H(2)O(2)), they display a response to severe stress (60 min at 50 degrees C or in the presence of 100 mM H(2)O(2)) similar to that of wild-type germlings. Furthermore, conidia of the tpsA mutant show a rapid loss of viability upon storage. These results are consistent with a role of trehalose in the acquisition of stress tolerance. Inactivation of the tpsA gene also results in increased steady-state levels of sugar phosphates but does not prevent growth on rapidly metabolizable carbon sources (glucose, fructose) as seen in Saccharomyces cerevisiae. This suggests that trehalose 6-phosphate is a physiological inhibitor of hexokinase but that this control is not essential for proper glycolytic flux in A. nidulans. Interestingly, tpsA transcription is not induced in response to heat shock or during conidiation, indicating that trehalose accumulation is probably due to a post-translational activation process of the trehalose 6-phosphate synthase.
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Affiliation(s)
- Sabine Fillinger
- Unité Microbiologie et Environnement, Institut Pasteur, 25 rue du Docteur Roux, 75724 Paris Cedex 15, France1
| | - Marie-Kim Chaveroche
- Unité Microbiologie et Environnement, Institut Pasteur, 25 rue du Docteur Roux, 75724 Paris Cedex 15, France1
| | - Patrick van Dijck
- Flanders Interuniversity Institute for Biotechnology, VIB and Laboratory of Molecular Cell Biology, Katholieke Universiteit Leuven, Kardinaal Mercierlaan 92, B-3001 Leuven-Heverlee, Flanders, Belgium2
| | - Ronald de Vries
- Molecular Genetics of Industrial Micro-organisms, Wageningen University, Dreijenlaan 2, 6703HA Wageningen, The Netherlands3
| | - George Ruijter
- Molecular Genetics of Industrial Micro-organisms, Wageningen University, Dreijenlaan 2, 6703HA Wageningen, The Netherlands3
| | - Johan Thevelein
- Flanders Interuniversity Institute for Biotechnology, VIB and Laboratory of Molecular Cell Biology, Katholieke Universiteit Leuven, Kardinaal Mercierlaan 92, B-3001 Leuven-Heverlee, Flanders, Belgium2
| | - Christophe d'Enfert
- Unité Microbiologie et Environnement, Institut Pasteur, 25 rue du Docteur Roux, 75724 Paris Cedex 15, France1
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Aleksenko A, Nielsen ML, Clutterbuck AJ. Genetic and physical mapping of two centromere-proximal regions of chromosome IV in Aspergillus nidulans. Fungal Genet Biol 2001; 32:45-54. [PMID: 11277625 DOI: 10.1006/fgbi.2001.1251] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Chromosome IV is the smallest chromosome of Aspergillus nidulans. The centromere-proximal portion of the chromosome was mapped physically using overlapping clones of a cosmid genomic library. Two contiguous segments of a physical map, based on restriction mapping of cosmid clones, were generated, together covering more than 0.4 Mb DNA. A reverse genetic mapping approach was used to establish a correlation between physical and genetic maps; i.e., marker genes were integrated into physically mapped segments and subsequently mapped by mitotic and meiotic recombination. The resulting data, together with additional classical genetic mapping, lead to a substantial revision of the genetic map of the chromosome, including the position of the centromere. Comparison of physical and genetic maps indicates that meiotic recombination is low in subcentromeric DNA, its frequency being reduced from 1 crossover per 0.8 Mb to approximately 1 crossover per 5 Mb per meiosis. The portion of the chromosome containing the functional centromere was not mapped because repeat-rich regions hindered further chromosome walking. The size of the missing segment was estimated to be between 70 and 400 kb.
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Affiliation(s)
- A Aleksenko
- Center for Process Biotechnology, Technical University of Denmark, Lyngby, 2800, Denmark.
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Katz ME, Masoumi A, Burrows SR, Shirtliff CG, Cheetham BF. The Aspergillus nidulans xprF gene encodes a hexokinase-like protein involved in the regulation of extracellular proteases. Genetics 2000; 156:1559-71. [PMID: 11102357 PMCID: PMC1461378 DOI: 10.1093/genetics/156.4.1559] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The extracellular proteases of Aspergillus nidulans are produced in response to limitation of carbon, nitrogen, or sulfur, even in the absence of exogenous protein. Mutations in the A. nidulans xprF and xprG genes have been shown to result in elevated levels of extracellular protease in response to carbon limitation. The xprF gene was isolated and sequence analysis indicates that it encodes a 615-amino-acid protein, which represents a new type of fungal hexokinase or hexokinase-like protein. In addition to their catalytic role, hexokinases are thought to be involved in triggering carbon catabolite repression. Sequence analysis of the xprF1 and xprF2 alleles showed that both alleles contain nonsense mutations. No loss of glucose or fructose phosphorylating activity was detected in xprF1 or xprF2 mutants. There are two possible explanations for this observation: (1) the xprF gene may encode a minor hexokinase or (2) the xprF gene may encode a protein with no hexose phosphorylating activity. Genetic evidence suggests that the xprF and xprG genes are involved in the same regulatory pathway. Support for this hypothesis was provided by the identification of a new class of xprG(-) mutation that suppresses the xprF1 mutation and results in a protease-deficient phenotype.
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Affiliation(s)
- M E Katz
- Molecular and Cellular Biology Division, School of Biological Sciences, University of New England, Armidale, New South Wales 2351, Australia.
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Halford NG, Purcell PC, Hardie DG. Is hexokinase really a sugar sensor in plants? TRENDS IN PLANT SCIENCE 1999; 4:117-120. [PMID: 10322544 DOI: 10.1016/s1360-1385(99)01377-1] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
The molecular mechanisms by which plant cells sense sugar levels are not understood, but current models (adapted from models for sugar sensing in yeast) favour hexokinase as the primary sugar sensor. However, the hypothesis that yeast hexokinase has a signalling function has not been supported by more recent studies and the idea that hexokinase is involved in sugar sensing in plants has yet to be proven.
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Affiliation(s)
- NG Halford
- IACR-Long Ashton Research Station, Dept of Agricultural Sciences, University of Bristol, Long Ashton, Bristol, UK BS41 9AF
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Ebbole DJ. Carbon catabolite repression of gene expression and conidiation in Neurospora crassa. Fungal Genet Biol 1998; 25:15-21. [PMID: 9806802 DOI: 10.1006/fgbi.1998.1088] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
- D J Ebbole
- Department of Plant Pathology and Microbiology, Texas A&M University, College Station, Texas, 77843-2132, USA.
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Abstract
Glucose and related sugars repress the transcription of genes encoding enzymes required for the utilization of alternative carbon sources; some of these genes are also repressed by other sugars such as galactose, and the process is known as catabolite repression. The different sugars produce signals which modify the conformation of certain proteins that, in turn, directly or through a regulatory cascade affect the expression of the genes subject to catabolite repression. These genes are not all controlled by a single set of regulatory proteins, but there are different circuits of repression for different groups of genes. However, the protein kinase Snf1/Cat1 is shared by the various circuits and is therefore a central element in the regulatory process. Snf1 is not operative in the presence of glucose, and preliminary evidence suggests that Snf1 is in a dephosphorylated state under these conditions. However, the enzymes that phosphorylate and dephosphorylate Snf1 have not been identified, and it is not known how the presence of glucose may affect their activity. What has been established is that Snf1 remains active in mutants lacking either the proteins Grr1/Cat80 or Hxk2 or the Glc7 complex, which functions as a protein phosphatase. One of the main roles of Snf1 is to relieve repression by the Mig1 complex, but it is also required for the operation of transcription factors such as Adr1 and possibly other factors that are still unidentified. Although our knowledge of catabolite repression is still very incomplete, it is possible in certain cases to propose a partial model of the way in which the different elements involved in catabolite repression may be integrated.
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Affiliation(s)
- J M Gancedo
- Instituto de Investigaciones Biomédicas, Unidad de Bioquímica y Genética de Levaduras, CSIC, 28029 Madrid, Spain.
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