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PubMed2000

Purification and characterization of a new member of the laccase family from the white-rot basidiomycete Coriolus hirsutus.

Laccase produced by Coriolus hirsutus was purified to electrophoretic homogeneity by acetone precipitation, DEAE Sepharose CL-6B, Sephacryl S-200 HR, Hitrap SP, and Mono S chromatography. The purification was 14.5-fold with an overall yield of 32.3%. The enzyme is a monomeric glycoprotein with 11% carbohydrate content, an isoelectric point of 7.4, and a molecular mass of 73 kDa. The N-terminal amino acid sequence showed low homology to those of the laccases of other white-rot basidiomycetes. Spectroscopic analyses revealed a typical laccase active site in the C. hirsutus enzyme, as all three Cu centers were identified. The absorption spectrum showed a type 1 signal at around 600 nm and a type 3 signal near 330 nm. Type 3 Cu showed fluorescence emission near 418 nm and an excitation maximum at 332 nm. The EPR spectrum yielded parameters for the type 1 and type 2 Cu of gII = 2.191 and AII = 0.0097 cm(-1), and gII = 2.222 and AII = 0.0198 cm(-1), respectively. The highest rate of 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonate) oxidation for the enzyme was reached at 45 degrees C, and the pH optima of the enzyme varied and was substrate dependent in the range of 2.5 to 4.0. The enzyme oxidized a variety of the usual laccase substrates, including lignin-related phenols and had highest affinity toward guaiacol. Under standard assay conditions, the apparent Km value of the enzyme toward guaiacol was 10.9 microM. The enzyme catalyzed single electron transfer via the phenoxy radical as an intermediate and was completely inhibited by L-cysteine and sodium azide but not by EDTA.

Amino Acid Sequence↗

PubMed2002

Purification and characterization of isocitrate lyase from the wood-destroying basidiomycete Fomitopsis palustris grown on glucose.

Isocitrate lyase (EC 4.1.3.1), a key enzyme in the glyoxylate cycle, was purified 76-fold with 23% yield as an electrophoretically homogeneous protein from the wood-destroying basidiomycete Fomitopsis palustris grown on glucose. The native enzyme has a molecular mass of 186 kDa, consisting of three identical subunits of 60 kDa. The K(m) for DL-isocitrate was found to be 1.6 mM at the optimum pH (7.0). The enzyme required Mg(2+) (K(m) 92 microM) and sulfhydryl compounds for optimal activity. The enzyme activity was strongly inhibited by oxalate and itaconate with a K(i) of 37 and 68 microM, respectively. The inhibition by the glycolysis and tricarboxylic acid cycle intermediates and related compounds suggested that the isocitrate lyase was a regulatory enzyme playing a crucial role in the fungal growth.

Basidiomycota↗

PubMed1999

A two-component tetrachlorohydroquinone reductive dehalogenase system from the lignin-degrading basidiomycete Phanerochaete chrysosporium.

Tetrachloro-1,4-hydroquinone (TClHQ) is an intermediate in the degradation of pentachlorophenol by the lignin-degrading basidiomycete Phanerochaete chrysosporium. Two enzymes required for the reductive dehalogenation of TClHQ to trichlorohydroquinone (TrClHQ) were identified in cell-free extracts of P. chrysosporium. In the presence of GSH, a membrane-bound enzyme converted TClHQ to the glutathionyl conjugate of TrClHQ (GS-TrClHQ). This membrane-bound glutathione transferase was specific for GSH as a cosubstrate. In the second step of the reductive dehalogenation reaction, a soluble enzyme fraction converted GS-TrClHQ to TrClHQ in the presence of GSH, cysteine, or dithiothreitol. Thus, this second enzyme appears to be a GS-conjugate reductase. These two enzyme fractions, working in tandem, also reductively dehalogenated TrClHQ and 2,6-dichlorohydroquinone, which are intermediates in the degradation of chlorophenols by this organism.

Cell Fractionation↗

PubMed2000

Characterization of interaction of C- and N-terminal domains in LIM15/DMC1 and RAD51 from a basidiomycetes, Coprinus cinereus.

Both LIM15/DMC1 and RAD51 are thought to be essential for meiosis in which homologous chromosomes pair and recombine. The primary purpose of the present study was to investigate the homotypic and heterotypic interactions among their terminal domains. We prepared cDNAs and recombinant proteins of the full-length, N-terminal, and the C-terminal domains of LIM15/DMC1 (CoLIM15) and RAD51 (CoRAD51) from the basidiomycete Coprinus cinereus. In both two-hybrid assay in vivo and pull-down assay in vitro, either CoLim15 or CoRad51 interacted homotypically between the C-terminal domains, respectively, but no heterotypic interaction was observed between CoLim15 and CoRad51. The N-terminal domain of CoLim15 bound to ssDNA and dsDNA, while the C-terminal domain of CoRad51 appeared to interact weakly with ssDNA. Based on these results, the interaction among the strand-exchange proteins and meiosis was discussed.

Cell Cycle Proteins↗

PubMed2001

The Gal/GalNAc-specific lectin from the plant pathogenic basidiomycete Rhizoctonia solani is a member of the ricin-B family.

The lectin isolated from the phytopathogenic basidiomycete Rhizoctonia solani (RSA) is a homodimer of two noncovalently associated monomers of 15.5 kDa. RSA is a basic protein (pI > 9) which consists mainly of beta-sheets. A presumed relationship with ricin-B is supported by the sequence similarity between the N-terminus of RSA and the N-terminal subdomain of ricin-B. Hydrophobic cluster analysis confirms that the N-terminus of both proteins has a comparable folding. RSA exhibits specificity towards Gal/GalNAc whereby the hydroxyls at the C3', C4', and C6' positions of the pyranose ring play a key role in the interaction with simple sugars. The carbohydrate-binding site of RSA apparently accommodates only a single sugar unit. Our results demonstrate an obvious evolutionary relationship between some fungal and plant lectins, but also provide evidence for the occurrence of a lectin consisting of subunits corresponding to a single subdomain of ricin-B.

Acetylgalactosamine↗

PubMed1994

Gravitropism of the basidiomycete Flammulina velutipes: morphological and physiological aspects of the graviresponse.

The fruiting body of the basidiomycete Flammulina velutipes shows a distinct negative gravitropic response. Maturing fruiting bodies in the rapid elongation phase become graviresponsive with basidiospore differentiation. Lateral gravistimulation by horizontal arrangement of the fruiting body results in unilateral growth regulation. Elongation in the upper Stipe side decreases to 40% during gravitropic reorientation of the fruiting body. Overshooting of the gravitropic response during reorientation is precisely regulated. The graviresponsiveness is concentrated to the apical area of the stipe, the transition zone between pileus and stipe, which features a prominent elongation capability. The small size and low vacuolization of the transition zone hyphae compared with differentiated basal stipe hyphae correspond with this physiological function on the light and electron microscopical levels. Curvature experiments using intact and explanted fruiting bodies demonstrated the graviperceptive role of the transition zone. The excision of various amounts of pilear tissue, even the disruption of the whole pileus, had no severe effect on gravitropic curvature, until the transition zone was damaged. Removal of the transition zone resulted in a dramatic loss of graviresponse, whereas the decrease of elongation was less drastic.

Basidiomycota↗

PubMed1999

Regulation of dikaryon-expressed genes by FRT1 in the basidiomycete Schizophyllum commune.

The gene FRT1 has previously been shown to induce homokaryotic fruiting in transformation recipients of the basidiomycete Schizophyllum commune. In this paper, we demonstrate by gene disruption experiments that FRT1 is dispensable for dikaryotic fruiting. Nonfruiting homokaryotic FRT1 disruptant strains exhibited enhanced aerial growth of mycelia compared to wild type. Introduction of a functional FRT1 allele into the disruptant restored the wild-type colony morphology. Transcript abundance of the dikaryon-expressed SC1 and SC4 hydrophobin genes and the SC7 gene were greatly elevated in homokaryotic FRT1 disruptant strains. Growth of the disruptant strains under continuous light was found to inhibit the elevation of SC1 and SC4 transcript levels, but not of SC7 mRNA. These data suggest that the role of FRT1 in vegetatively growing homokaryons is to act as a negative regulator of dikaryon-expressed genes.

Alleles↗

PubMed1999

Ligand recognition in multiallelic pheromone receptors from the basidiomycete Schizophyllum commune studied in yeast.

The homobasidiomycete Schizophyllum commune encodes a multiallelic pheromone receptor system that distinguishes more than 20 nonself from at least 2 self pheromones. The well-investigated pheromone response system of the yeast Saccharomyces cerevisiae was used to link the FUS1::lacZ reporter system to the heterologous pheromone receptors from S. commune. To investigate yeast G-protein binding, the unchanged heterologous receptor was compared to constructs carrying an exchange of the 3rd cytoplasmatic loop for the Ste2 sequence. A better coupling could be achieved with the altered constructs. In order to examine activation by single pheromones, an artificial peptide based on the sequence of a new putative pheromone gene, bap2(1), in the Balpha2 mating-type locus encoding the shortest pheromone found so far in fungal mating types was used. Thus, we have reassembled the pheromone recognition of the basidiomycete S. commune and constructed a system ideal for specificity analysis in the yeast S. cerevisiae.

Amino Acid Sequence↗

PubMedDate not supplied

Cell wall proteins of the ectomycorrhizal basidiomycete Pisolithus tinctorius: identification, function, and expression in symbiosis.

Specific cell-cell and cell-substrate interactions direct the growth of ectomycorrhizal fungi to their host root targets. These elaborate mechanisms lead to the differentiation of distinct multihyphal structures, the mantle, and the Hartig net. In the ectomycorrhizal basidiomycete Pisolithus tinctorius, the use of two-dimensional gel electrophoresis, immunocytochemical microscopy, and RNA blot analysis has demonstrated the differential expression of cell wall proteins (CWPs), such as hydrophobins, adhesins, and mannoproteins, during symbiotic interaction. In other fungi, these CWPs have been suggested to play a role in hyphae aggregation, intracellular signaling cascades, and cytoskeletal changes. The recent cloning of the genes for several of these CWPs in P. tinctorius allows us to address their function in symbiosis. This review summarizes our knowledge of CWPs in P. tinctorius and considers parallels with other biotrophic fungi as a possible framework for future work.

Amino Acid Sequence↗

PubMed2000

Chimeric pheromone receptors in the basidiomycete Schizophyllum commune.

The pheromone receptor system of the basidiomycete Schizophyllum commune is capable of ligand discrimination to confer mating specificity. The pheromone receptors of the B alpha locus were investigated for ligand discrimination in a strategy of domain swapping experiments. Several altered phenotypes of chimeric receptors have been found. These include constitutive pheromone receptors which need no ligand for activation of the downstream cascade of events. In addition, receptors still dependent on ligand were identified that had altered pheromone activation profiles, including promiscuous receptors that are activated by pheromones of all nine specificities, including the former self. In addition, highly discriminative receptors were created which are activated by only two of the eight non-self-specificities. The chimeric receptors identify the last third of the receptor as the determinant for B alpha 1 specificity, whereas B alpha 2 specificity resides in noncontiguous domains covering the first and middle parts of the receptor molecule.

Amino Acid Sequence↗

PubMed2001

Isolation, characterization, and expression patterns of a DMC1 homolog from the basidiomycete Pleurotus ostreatus.

Here we describe the isolation of a Pleurotus ostreatus gene PoDMC1. The predicted amino acid sequence of the oyster mushroom gene is 62% identical to the yeast DMC1 and 60% identical to human DMC1. The highest degree of amino acid identity (88%), however, was shown with Coprinus CoLIM15, a DMC1 homolog recently found in Coprinus cinereus. The exact matching of sizes and positions of most introns in both basidiomycete genes underlines the close relationship between these DMC1 orthologs. The RecA homolog DMC1 from yeast and its orthologs from other species have been reported to be meiosis specific and essential for sporulation. Here we show that PoDMC1 is exclusively expressed in the lamellae/basidiospore fraction of fruit bodies and not in somatic cells of fruiting bodies or in vegetative mycelium. Furthermore, the gene is not expressed in the lamellae/basidiospore fraction of a nonsporulating mutant of P. ostreatus. Since one of the major problems in cultivating the oyster mushroom is the abundant sporulation that causes allergic reactions in man, PoDMC1 could be an important target gene in constructing sporeless Pleurotus strains.

Amino Acid Sequence↗

PubMed2002

Hydrophobins DGH1, DGH2, and DGH3 in the lichen-forming basidiomycete Dictyonema glabratum.

Dictyonema glabratum is a lichen-forming basidiomycete whose symbiotic phenotype shares similarities to both lichens and its non-lichen-forming relatives. In the photobiont layer of D. glabratum intercellular gas-filled spaces are present even when the lichen is water-saturated. The walls of hyphae lining air cavities are covered by a hydrophobic, rodlet-patterned layer, assumed to be formed by hydrophobins. Hot SDS-insoluble, but trifluoroacetic acid-soluble lichen cell wall extracts contained seven proteins. The N-terminal sequence of the most abundant 14-kDa protein was used to carry out cDNA cloning by RT-PCR. The deduced amino acid sequence of the amplified fragment encoded a class I hydrophobin, called DGH1. The cDNA sequence encoding the signal peptide was cloned by RACE-PCR, which also coamplified cDNA fragments encoding two additional class I hydrophobins, DGH2 and DGH3. The three proteins share 54 to 66% amino acid identity. The D. glabratum hydrophobin extract containing either all proteins or primarily DGH1 self-assembled and formed a rodlet mosaic similar to the one observed in situ. Concentration of the protein extract was shown to influence the length of the self-assembled rodlets.

Amino Acid Sequence↗

PubMed1998

Production of a novel pyranose 2-oxidase by basidiomycete Trametes multicolor.

During a screening for the enzyme pyranose 2-oxidase (P2O) which has a great potential as a biocatalyst for carbohydrate transformations, Trametes multicolor was identified as a promising, not-yet-described producer of this particular enzyme activity. Furthermore, it was found in this screening that the enzyme frequently occurs in basidiomycetes. Intracellular P2O was produced in a growth-associated manner by T. multicolor during growth on various substrates, including mono-, oligo-, and polysaccharides. Highest levels of this enzyme activity were formed when lactose or whey were used as substrates. Peptones from casein and other casein hydrolysates were found to be the most favorable nitrogen sources for the formation of P2O. By applying an appropriate feeding strategy for the substrate lactose, which ensured an elevated concentration of the carbon source during the entire cultivation, levels of P2O activity obtained in laboratory fermentations, as well as the productivity of these bioprocess experiments, could be enhanced more than 2.5-fold.

Basidiomycota↗

PubMed1993

Bending of DNA segments with Saccharomyces cerevisiae autonomously replicating sequence activity, isolated from basidiomycete mitochondrial linear plasmids.

Previous studies have indicated that DNA bending is a general structural feature of sequences (ARSs) from cellular DNAs of yeasts and nuclear and mitochondrial genomic DNAs of other eukaryotes that are capable of autonomous replication in Saccharomyces cerevisiae. Here we showed that bending activity is also tightly associated with S. cerevisiae ARS function of segments cloned from mitochondrial linear DNA plasmids of the basidiomycetes Pleurotus ostreatus and Lentinus edodes. Two plasmids, designated pLPO2-like (9.4 kb), and pLPO3 (6.6 kb) were isolated from a strain of P. ostreatus. A 1029 bp fragment with high-level ARS activity was cloned from pLPO3 and it contained one ARS consensus sequence (A/T)TTTAT(A/G)TTT(A/T) indispensable for activity and seven dispersed ARS consensus-like (10/11 match) sequences. A discrete bent DNA region was found to lie around 500 bp upstream from the ARS consensus sequence (T-rich strand). Removal of the bent DNA region impaired ARS function. DNA bending was also implicated in the ARS function associated with a 1430 bp fragment containing three consecutive ARS consensus sequences which had been cloned from the L. edodes plasmid pLLE1 (11.0 kb): the three consecutive ARSs responsible for high-level ARS function occurred in, and immediately adjacent to, a bent DNA region. A clear difference exists between the two plasmid-derived ARS fragments with respect to the distance between the bent DNA region and the ARS consensus sequence(s).

Base Sequence↗

PubMed1993

Isolation and transformation of uracil auxotrophs of the lignin-degrading basidiomycete Phanerochaete chrysosporium.

Uracil auxotrophs of Phanerochaete chrysosporium were isolated using 5-fluoroorotate resistance as a selection scheme. The ura3 auxotrophs deficient in orotidylate decarboxylase and ura5 auxotrophs deficient in orotate phosphoribosyl transferase were characterized by enzyme assays and complementation tests. The ura5 auxotrophs were transformed to prototrophy with the ura5 gene from the ascomycete Podospora anserina. The ura3 auxotrophs were transformed to prototrophy with the ura3 gene from the basidiomycete Schizophyllum commune. The P. chrysosporium ura3 gene was isolated from a lambda EMBL3 genomic library using the S. commune ura3 gene as a probe. A 6.6-kb fragment incorporating the ura3 gene was subcloned into Bluescript SK+(pURA3.1) and used to transform P. chrysosporium ura3 auxotrophic strains. The pURA3.1 insert was mapped for restriction sites and the approximate location of the ura3 gene within the insert was determined. Double auxotrophic strains were transformed with either of two marker genes and the resulting single auxotrophic strains were crossed to demonstrate genetic recombination between two nuclei of identical genetic background.

Ascomycota↗

PubMed1992

Genetic transformation of the symbiotic basidiomycete fungus Hebeloma cylindrosporum.

The pAN7.1 plasmid containing the E. coli hygromycin B phosphotransferase gene was used to transform protoplasts of the ectomycorrhizal fungus Hebeloma cylindrosporum. Hygromycin-resistant transformants were selected at a frequency of one to five per micrograms of transforming DNA. Southern blot analyses revealed multiple copy integration of the transforming plasmid into the genome. The selection system was used to introduce other genes of interest by co-transformation. Two plasmids, one containing tryptophan biosynthesis genes and the other the NADP-glutamate dehydrogenase gene from the saprophytic basidiomycete Coprinus cinereus, were successfully introduced into the H. cylindrosporum genome with up to 70% efficiency of co-transformation. The hygromycin resistance phenotype was stably maintained during growth of transformants on hygromycin-free medium. All transformants retained their ability to form mycorrhizae with the habitual host plant Pinus pinaster, making them suitable for future physiological studies.

Basidiomycota↗

PubMed1980

Absence of short-period repetitive-sequence interspersion in the basidiomycete Schizophyllum commune.

Reassociation kinetics and electron microscopy were used to examine the organization of DNA sequences in the Basidiomycete Schizophyllum commune. Short-period interspersion of repetitive and unique sequences is absent from the DNA of this wood-rotting fungus. Instead, repetitive sequences are found predominantly in several, perhaps 16, clusters averaging 225 kilobases in length. The results of this study, the first concerning a fungus in the important fungal Class Basidiomycetidae, are discussed in relation to: sequence organization in three other species of true fungi, fungal evolution and the regulation of gene expression.

Agaricales↗

PubMed1989

Leucosporidium fellii sp. nov., a basidiomycetous yeast that degrades L(+)-tartaric acid.

A new species of basidiomycetous yeast Leucosporidium fellii was isolated from soil in Portugal on a selective L(+)-tartaric acid medium. This yeast is self-sporulating but forms dikaryotic hyphae with clamp connections and is presumably homothallic. It differs from the type strain of Leucosporidium scottii in its life cycle, assimilation pattern and guanine-cytosine content and from the other described Leucosporidium species by additional characteristics.

Basidiomycota↗