PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Neurospora crassa”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources
PubMed1976

Genetic and metabolic regulation of purine base transport in Neurospora crassa.

Neurospora crassa can utilize various purine bases such as xanthine or uric acid and their catabolic products as a nitrogen source. The early purine catabolic enzymes in this organism are regulated by induction and by ammonium repression. Studies were undertaken to investigate purine base transport and its regulation in Neurospora. The results of competition experiments with uric acid and xanthine transport strongly suggest that uric acid and xanthine share a common transport system. It was also shown that the common transport system for uric acid and xanthine is distinct from a second transport system shared by hypoxanthine, adenine and guanine, and apparently also distinct from the transport system(s) for adenosine, cytosine and uracil. Regulation of the uric acid-xanthine transport system and the hypoxanthine-adenine-guanine transport system was studied. The results reveal that the uric acid-xanthine transport system is regulated by ammonium repression, but does not require uric acid induction. Neither ammonium repression nor uric acid induction controls the hypoxanthine-adenine-guanine transport system. A gene, designated amr, which is believed to be a positive regulatory gene for nitrogen metabolism of Neurospora crassa, was found to dramatically affect both the uric acid-xanthine transport system and the hypoxanthine-adenine-guanine transport system. A model for the action of the amr locus as a positive regulatory gene and for the interaction between the amr gene product and its recognition sites will be discussed.

Binding, Competitive↗
PubMed1986

Genetic and biochemical identification of the glutamate synthase structural gene in Neurospora crassa.

Neurospora crassa cells require glutamate synthase activity for growth under ammonium-limiting conditions. Despite the physiological importance of glutamate synthase, little is known about the genetics of its expression. To identify the glutamate synthase structural gene, we isolated three new mutants lacking this activity. All mutations are recessive to the wild-type allele and belong to the same complementation group as the previously described en(am)-2 (C24) mutation. Two lines of evidence indicate that en(am)-2 is the structural gene for glutamate synthase in N. crassa. The en(am)-2+ gene shows a gene dosage effect on enzyme activity, and some mutants lacking glutamate synthase activity have cross-reacting material. These data suggest that the mutations are located in the structural gene for N. crassa glutamate synthase.

Alleles↗
PubMed1993

Cloning of the gene for glutamate decarboxylase and its expression during conidiation in Neurospora crassa.

Neurospora crassa glutamate decarboxylase (GAD) is produced during conidiation and stored in dormant conidia. Polyclonal antibody was generated to GAD that had been purified to homogeneity. The anti-GAD antibody was specific for N. crassa GAD and inhibited GAD activity. The level of GAD protein decreased during conidial germination, indicating that GAD was degraded during this phase of development. The anti-GAD antibody was used to isolate a cDNA clone of GAD from a lambda ZAP cDNA expression library. Escherichia coli containing a plasmid with the cDNA insert produced GAD activity. The cDNA clone contained a 2.6 kbp insert and hybridized to a 2.6 kb mRNA species from conidiating cultures of N. crassa. GAD mRNA was not present in vegetative hyphae. In conidiating cultures, GAD mRNA was first detected when conidia began to appear. The level of GAD mRNA increased as conidiation progressed. This is the first example of the cloning of an enzyme that is regulated at the level of mRNA during the asexual developmental cycle of N. crassa.

Antibodies↗
PubMed1988

Putrescine and spermidine control degradation and synthesis of ornithine decarboxylase in Neurospora crassa.

Neurospora crassa mycelia, when starved for polyamines, have 50-70-fold more ornithine decarboxylase activity and enzyme protein than unstarved mycelia. Using isotopic labeling and immunoprecipitation, we determined the half-life and the synthetic rate of the enzyme in mycelia differing in the rates of synthesis of putrescine, the product of ornithine decarboxylase, and spermidine, the main end-product of the polyamine pathway. When the pathway was blocked between putrescine and spermidine, ornithine decarboxylase synthesis rose 4-5-fold, regardless of the accumulation of putrescine. This indicates that spermidine is a specific signal for the repression of enzyme synthesis. When both putrescine and spermidine synthesis were reduced, the half-life of the enzyme rapidly increased 10-fold. The presence of either putrescine or spermidine restored the normal enzyme half-life of 55 min. Tests for an ornithine decarboxylase inhibitory protein ("antizyme") were negative. The regulatory mechanisms activated by putrescine and spermidine account for most or all of the regulatory amplitude of this enzyme in N. crassa.

Cyclohexylamines↗
PubMed1999

Microconidia of Neurospora crassa.

Neurospora crassa produces two types of vegetative spores-relatively small numbers of uninucleate microconidia and very large numbers of multinucleate macroconidia (blastoconidia and arthroconidia). The microconidia can function either as spermatia (male gametes) or as asexual reproductive structures or both. In nature they probably function exclusively in fertilization of protoperithecia. The environmental conditions favoring their formation and the pattern of their development are quite distinct from those of macroconidia. Mutants of N. crassa have been isolated in which macroconidiation is selectively blocked without affecting microconidiation, showing that these two types of conidial differentiation involve distinct developmental pathways. Unlike microconidia of some related ascomycetes, those of Neurospora are capable of germination, providing viable uninucleate haploid cells which are desired in several types of investigations. A technique of selectively removing macroconidia from culture initiated on cellophane overlying agar medium allows pure microconidia to be obtained even from the wild-type strains of Neurospora. The conditional microcyclic strain, mcm, allows either macroconidia or microconidia to be obtained at will, depending on the conditions of culture. The new methods of obtaining pure microconidia from normal laboratory strains will make it quick and easy to purify heterokaryotic transformants following introduction of DNA into multinucleate protoplasts. Moreover, these methods allow the detection of genetic variability that remains hidden within an individual fungus and the estimation of the frequency of nuclear types in laboratory-constructed heterokaryons. The discovery, function, and development of microconidia are described and their research applications are discussed in this review.

Culture Media↗
PubMed1975

Characterization of 5.8S ribosomal ribonucleic acid in Neurospora crassa.

Neurospora crassa ribosomes contain a species of ribonucleic acid (RNA) of molecular weight 54,000, similar to 5.8S ribosomal RNA previously described for other eukaryotic organisms. The 5.8S RNA from N. crassa was found to be released by heat treatment at 60 C from 25S ribosomal RNA but not from 18S ribosomal RNA. The base composition of N. crassa 5.8S RNA was similar to that of 5.8S RNA from Saccharomyces cerevisiae, but differed from animal 5.8S RNA. During the course of this study, it was discovered that N. crassa 25S ribosomal RNA had a number of internal cleavages that may exist in vivo.

Cytidine↗
PubMed1990

Mode of action of glycogen branching enzyme from Neurospora crassa.

Neurospora crassa branching enzyme [EC 2.4.1.18] acted on potato amylopectin or amylose to convert them to highly branched glycogen-type molecules which consisted of unit chains of six glucose units. The enzyme also acted on the amylopectin beta-limit dextrin, indicating that the enzyme acted on internal glucose chains as well as outer chains. By the combined action of N. crassa glycogen synthase [EC 2.4.1.11] and the branching enzyme, a glycogen-type molecule was formed from UDP-glucose. In the presence of primer glycogen, the glucose transfer reaction was accelerated by the addition of branching enzyme. On the other hand, the glucose transfer reaction by glycogen synthase did not occur without primers. When the branching enzyme was added, the glucose transfer occurred after a short time lag. This recovery of the glucose transfer reaction did not occur upon addition of the inactivated branching enzyme. The structure of the product formed by the combined action of the two enzymes was different from that of the intact N. crassa glycogen with respect to the distribution patterns of the unit chains.

1,4-alpha-Glucan Branching Enzyme↗
PubMed2003

The genome sequence of the filamentous fungus Neurospora crassa.

Neurospora crassa is a central organism in the history of twentieth-century genetics, biochemistry and molecular biology. Here, we report a high-quality draft sequence of the N. crassa genome. The approximately 40-megabase genome encodes about 10,000 protein-coding genes--more than twice as many as in the fission yeast Schizosaccharomyces pombe and only about 25% fewer than in the fruitfly Drosophila melanogaster. Analysis of the gene set yields insights into unexpected aspects of Neurospora biology including the identification of genes potentially associated with red light photobiology, genes implicated in secondary metabolism, and important differences in Ca2+ signalling as compared with plants and animals. Neurospora possesses the widest array of genome defence mechanisms known for any eukaryotic organism, including a process unique to fungi called repeat-induced point mutation (RIP). Genome analysis suggests that RIP has had a profound impact on genome evolution, greatly slowing the creation of new genes through genomic duplication and resulting in a genome with an unusually low proportion of closely related genes.

Calcium Signaling↗
PubMed1988

Ferricrocin functions as the main intracellular iron-storage compound in mycelia of Neurospora crassa.

Neurospora crassa produces several structurally distinct siderophores: coprogen, ferricrocin, ferrichrome C and some minor unknown compounds. Under conditions of iron starvation, desferricoprogen is the major extracellular siderophore whereas desferriferricrocin and desferriferichrome C are predominantly found intracellularly. Mössbauer spectroscopic analyses revealed that coprogen-bound iron is rapidly released after uptake in mycelia of the wild-type N. crassa 74A. The major intracellular target of iron distribution is desferriferricrocin. No ferritin-like iron pools could be detected. Ferricrocin functions as the main intracellular iron-storage peptide in mycelia of N. crassa. After uptake of ferricrocin in both the wild-type N. crassa 74A and the siderophore-free mutant N. crassa arg-5 ota aga, surprisingly little metabolization (11%) could be observed. Since ferricrocin is the main iron-storage compound in spores of N. crassa, we suggest that ferricrocin is stored in mycelia for inclusion into conidiospores.

Biological Transport, Active↗
PubMed1978

Nitrogen source regulates glutamine synthetase mRNA levels in Neurospora crassa.

Neurospora crassa glutamine synthetase mRNA was measured by its capacity to direct the synthesis of the specific protein in a cell-free system derived from rabbit reticulocytes. N. crassa cultures grown on glutamate as the sole nitrogen source had higher mRNA activities than did those grown on glutamine. The differences were about 10-fold when polysomal RNA was used for translation and about 5-fold when either total cellular RNA or polyadenylic acid-enriched cellular RNA was used. These data indicate that in exponentially growing N. crassa, the nitrogen source regulates glutamine synthetase by adjusting specific mRNA levels.

Cell-Free System↗
PubMed2004

A pheromone receptor gene, pre-1, is essential for mating type-specific directional growth and fusion of trichogynes and female fertility in Neurospora crassa.

Neurospora crassa is a heterothallic filamentous fungus with two mating types, mat a and mat A. Its mating involves differentiation of female reproductive structures (protoperithecia) and chemotropic growth of female-specific hyphae (trichogynes) towards a cell of the opposite mating type in a pheromone-mediated process. In this study, we characterize the pre-1 gene, encoding a predicted G-protein-coupled receptor with sequence similarity to fungal pheromone receptors. pre-1 is most highly expressed in mat A strains under mating conditions, but low levels can also be detected in mat a strains. Analysis of pre-1 deletion mutants showed that loss of pre-1 does not greatly affect vegetative growth, heterokaryon formation or male fertility in either mating type. Protoperithecia from Deltapre-1 mat A mutants do not undergo fertilization; this defect largely stems from an inability of their trichogynes to recognize and fuse with mat a cells. Previous work has demonstrated that the Galpha subunit, GNA-1, and the Gbeta protein, GNB-1, are essential for female fertility in N. crassa. Trichogynes of Deltagna-1 and Deltagnb-1 mutants displayed severe defects in growth towards and fusion with male cells, similar to that of Deltapre-1 mat A strains. However, the female sterility defect of the Deltapre-1 mat A mutant could not be complemented by constitutive activation of gna-1, suggesting additional layers of regulation. We propose that PRE-1 is a pheromone receptor coupled to GNA-1 that is essential for the mating of mat A strains as females, consistent with a role in launching the pheromone response pathway in N. crassa.

Fungal Proteins↗
PubMed1996

Metabolism of ricinoleate by Neurospora crassa.

Neurospora crassa is a potential expression system for evaluating fatty-acid-modifying genes from plants producing uncommon fatty acids. One such gene encodes the hydroxylase that converts oleate to ricinoleate, a fatty acid with important industrial uses. To develop this expression system, it is critical to evaluate the metabolism and physiological effects of the expected novel fatty acid(s). We therefore examined effects of ricinoleate on lipid biosynthesis and growth of N. crassa. Ricinoleate inhibited growth and reduced levels of phospholipids and 2-hydroxy fatty acids in glycolipids, but led to increased lipid accumulation on a mass basis. To evaluate incorporation and metabolism of ricinoleate, we followed the fate 14 microM-3mM [1-14C]ricinoleate. The fate of the [14C]ricinoleate was concentration-dependent. At higher concentrations, ricinoleate was principally incorporated into triacylglycerols. At lower concentrations, ricinoleate was principally metabolized to other compounds. Thus, N. crassa transformants expressing the hydroxylase gene can be detected if the level of hydroxylase expression allows both growth and ricinoleate accumulation.

Fatty Acids↗
PubMed2007

Roles of putative His-to-Asp signaling modules HPT-1 and RRG-2, on viability and sensitivity to osmotic and oxidative stresses in Neurospora crassa.

Neurospora crassa has a putative histidine phosphotransfer protein (HPT-1) that transfers signals from 11 histidine kinases to two putative response regulators (RRG-1 and RRG-2) in its histidine-to-aspartate phosphorelay system. The hpt-1 gene was successfully disrupted in the os-2 (MAP kinase gene) mutant, but not in the wild-type strain in this study. Crossing the resultant hpt-1; os-2 mutants with the wild-type or os-1 (histidine kinase gene) mutant strains produced no progeny with hpt-1 or os-1; hpt-1 mutation, strongly suggesting that hpt-1 is essential for growth unless downstream OS-2 is inactivated. hpt-1 mutation partially recovered the osmotic sensitivity of os-2 mutants, implying the involvement of yeast Skn7-like RRG-2 in osmoregulation. However, the rrg-2 disruption did not change the osmotic sensitivity of the wild-type strain and the os-2 mutant, suggesting that rrg-2 did not participate in the osmoregulation. Both rrg-2 and os-2 single mutation slightly increased sensitivity to t-butyl hydroperoxide, and rrg-2 and hpt-1 mutations increased the os-2 mutant's sensitivity. Although OS-1 is considered as a positive regulator of OS-2 MAP kinase, our results suggested that HPT-1 negatively regulated downstream MAP kinase cascade, and that OS-2 and RRG-2 probably participate independently in the oxidative stress response in N. crassa.

Amino Acid Motifs↗
PubMed1995

Resistance to azole drugs in Neurospora crassa.

Neurospora crassa was susceptible to azole drugs: ketoconazole (MIC 1 microgram/ml), fluconazole (MIC 5 micrograms/ml), and SCH39304 (MIC 5 micrograms/ml). Mutants of N. crassa resistant to ketoconazole were selected and genetically characterized. The seven characterized resistance mutations represented at least four genetic loci. Some mutants, but not all, were also resistant to fluconazole and to SCH39304.

Antifungal Agents↗
PubMed1982

Regulation of L-amino acid oxidase and of D-amino acid oxidase in Neurospora crassa.

Neurospora crassa possesses an inducible L-amino acid oxidase that is expressed only when cells are derepressed for nitrogen in the presence of an amino acid. Enzyme synthesis requires both induction by an amino acid and simultaneous nitrogen catabolite derepression. Carbon limition in the presence of an amino acid does not permit induction of L-amino acid oxidase. The nit-2 gene is a major regulatory locus which is believed to mediate nitrogen catabolite repression in Neurospora. Mutants of nit-2 are repressed for L-amino acid oxidase activity under conditions which lead to good enzyme induction in wild type and nit-2 revertants. The loss of the enzyme in nit-2 mutants does not result from inducer exclusion, which suggests that the nit-2 gene product has a direct role in controlling the expression of this enzyme. Substantial amounts of L-amino acid oxidase were detected in the growth medium as well as in cell extracts of the wild type strain. Biochemical data indicates that the intracellular and the extracellular L-amino acid oxidases are identical. Inhibitors of protein and of RNA synthesis block accumulation of L-amino acid oxidase, suggesting that enzyme expression is controlled at the level of transcription. D-amino acid oxidase can be detected in cell extracts of Neurospora grown in the presence of a D-amino acid. The enzyme is present in cys-3 mutants and is not repressed by high concentrations of sulfate or nitrogen indicating that D-amino acid oxidase is not a member of the sulfur or nitrogen regulatory circuits of this organism.

Amino Acid Oxidoreductases↗
PubMed1986

Genetical and molecular analyses of qa-2 transformants in Neurospora crassa.

Neurospora crassa qa-2+ transformants from five different donor DNA clones were analyzed by genetical and molecular techniques. None of the 32 transformants have the qa-2+ DNA replacing the qa-2- gene in linkage group VII. In one transformant, the qa-2+ DNA was inserted adjacent to the qa-2- gene. Thirty-one transformants have the qa-2+ inserts at sites not linked, or not closely linked, to the qa-2 locus in LG VII. Plasmid sequences were integrated along with the qa-2+ gene in 28 transformants. In the unlinked duplication-type transformants, catabolic dehydroquinase (the qa-2+ gene product) was induced at 5-100% of the wild-type-induced enzyme activity, with 24 transformants in the 5-80% range. The reduced levels of enzyme activity may be due to "position effects" of sequences adjacent to the integration site either in the N. crassa genomic DNA or in the flanking plasmid (pBR322 or pBR325) sequences. Unexpected gene conversion-like events, in which a qa-2+ gene was changed to qa-2-, were observed in tetrads from intercrosses between unlinked duplication-type transformants and in selfings of such transformants.

Cloning, Molecular↗
PubMed1973

Aryl sulfatase in ascospores of Neurospora crassa.

Neurospora crassa ascospores normally do not contain aryl sulfatase even when formed under conditions of sulfur limitation. However, when one of the parental strains is the nonrepressible mutant scon(c), the resulting (mixed) ascospores contain significant levels of aryl sulfatase even when formed under conditions of sulfur abundance.

Cell-Free System↗