bluuebunny/crossref_metadata_2025 huggingface dataset:
Population biology of the chestnut blight fungus,Cryphonectria parasitica
Authors: Milgroom Michael G.
Published: May 2008

Interest in the population biology of the chestnut blight fungus Cryphonectria parasitica has been motivated largely by the potential for biological control of chestnut blight with fungal viruses that cause hypovirulence. Earlier studies gave valuable insights into the correlation between diversity of vegetative compatibility groups and transmission of hypovirulence viruses. However, inferences about evolutionary processes affecting populations were not possible because vegetative compatibility groups are not genetically defined. Using restriction fragment length polymorphism markers, however, progress has been made in studying the origin of C. parasitica in North America, gene flow among populations, dispersal within populations, and recombination and the mating system. Cryphonectria parasitica populations in North America are genetically more similar to populations in Japan than in China, which is consistent with previous speculations that this fungus was introduced from Japan. Populations in China and Japan are quite different, suggesting little or no gene flow between these areas. Restricted gene flow and genetic drift are probably the dominant evolutionary forces shaping North American populations, with approximately 20% of gene diversity due to differences among populations (GST = 0.20). Two populations of C. parasitica in Michigan and one population in Italy are primarily clonal in structure. In contrast, sexual reproduction appears to be common in populations in eastern North America, although most of these populations deviate significantly from random mating. Deviations from random mating are most likely due to self-fertilization (uniparental inbreeding), restricted dispersal of male gametes, and mating between individuals that are more closely related genetically than would be expected by chance (biparental inbreeding). Aggregations of similar genotypes in space suggest that populations of C. parasitica may be structured into genetic neighborhoods by restricted dispersal. Future research efforts in this system will explore isolation by distance and address questions of hypovirulence virus coevolution with its fungal host. Key words: Cryphonectria parasitica, Endothia parasitica, chestnut blight, genetic neighbourhoods, inbreeding.
Genetic regulation of mating and dimorphism in Ustilago maydis
Authors: Bölker Michael , Genin Stéphane , Lehmler Christiane , Kahmann Regine
Published: May 2008

During its life cycle the phytopathogenic fungus Ustilago maydis adopts two different morphological forms. The haploid sporidia grow yeastlike and are nonpathogenic, the dikaryon grows filamentous and is able to infect corn plants. Cell fusion, pathogenicity, and dimorphism are under the control of two unlinked mating type loci, a and b. The a locus encodes a pheromone-based cell-recognition system and the b locus codes for two homeodomain proteins. Filamentous growth is dependent on the autocrine stimulation of the pheromone response pathway and on the presence of two nonidentical b alleles. We have identified genes whose expression is strictly limited to the filamentous phase and that are candidates for direct or indirect regulation by a and b. We also describe the development of a systematic screen for mutants that are affected in filamentous growth and (or) in pathogenicity. Key words: dimorphism, pheromones, homeodomain proteins, differential gene expression.
Gene expression inMucordimorphism
Authors: Orlowski Michael
Published: May 2008

An ongoing dialectic has concerned the relative importance of differential gene expression versus the pattern of new wall deposition in Mucor dimorphism. Numerous physiological processes and enzyme activities have been observed in flux during morphogenesis, but a causal link to dimorphism has been infrequently demonstrated. Very few of the proteins that are conspicuous in two-dimensional polyacrylamide gel electrophoresis are specific to cell morphology or significantly change in amount during morphogenesis. Cyclic AMP, putrescine, S-adenosylmethionine, and enzymes governing their intracellular concentrations show patterns of change that consistently correlate with morphogenesis. The expression of RAS proteins and translation elongation factor-1α activity during morphogenesis are regulated at the level of transcription and post-translational methylation, respectively. Wall chemistry is very similar in both morphologies, but wall deposition is isodiametric in yeasts and vectorial in hyphae. Electron microscopy shows patterns of apparent exocytosis that are generalized in the former and apical in the latter. Research on other dimorphic fungi, including Saccharomyces cerevisiae, suggests an involvement of cytoskeletal proteins and a family of GTP-linked protein kinases in directing polar growth. Some of these elements, which may be controlled quite distal from the genes encoding them, have been demonstrated in Mucor spp., while others are the subject of ongoing investigations. Key words: Mucor, dimorphism, morphogenesis, gene expression, yeasts, hyphae.
Genes associated with dimorphism and virulence ofCandida albicans
Authors: Gow N. A. R. , Hube B. , Bailey D. A. , Schofield D. A. , Munro C. , Swoboda R. K. , Bertram G. , Westwater C. , Broadbent I. , Smith R. J. , Gooday G. W. , Brown A. J. P.
Published: May 2008

Strategies for the analysis of a range of Candida albicans genes, whose expression is regulated during the yeast to hyphal transition (dimorphism), including genes encoding putative virulence factors, are reviewed. To help discriminate among genes whose products were the cause or consequence of dimorphism, temporal changes in the levels of the mRNAs of these and other genes were examined by northern analysis. The mRNA levels of most genes that were examined increased or decreased, transiently or persistently indicating complex alterations in gene expression during morphogenesis. Genes encoding four glycolytic enzymes were regulated transcriptionally during dimorphism but control experiments indicated no direct correlation with germ tube formation. Two chitin synthase genes (CHS2 and CHS3) and three aspartyl proteinase genes (SAP4–SAP6) were transcribed preferentially in the hyphal form, but in these cases hypha-specific expression was shown to be strain dependent or medium dependent, respectively. A gene, HYR1 (for hyphal regulation), was isolated and found to exhibit strict hypha-specific expression in a range of strains under a range of culture conditions. The ura-blaster protocol was used to generate disruptions in CHS2, CHS1, and HSP90 (for heat-shock protein). The homozygous CHS2 disruption did not affect the kinetics of germ-tube formation markedly but resulted in hyphae with a reduced chitin content. In contrast, homozygous null mutations in CHS1 and HSP90 were apparently lethal because no homozygous null strains were isolated after integrative transformation of heterozygous mutants. The analysis of candidate genes for dimorphism and virulence of C. albicans through northern analysis and gene disruption should facilitate an understanding of these processes at the molecular level. Key words: Candida, dimorphism, gene regulation, virulence.
Protein targeting and degradation in the yeast vacuole
Authors: Chiang Hui-Ling
Published: May 2008

Protein degradation is an essential process in cells. Degradation of intracellular proteins increases when cells are starved of nutrients. Lysosomes are responsible for the enhanced protein degradation during starvation. To understand the degradation process that occurs in lysosomes, we studied the catabolite inactivation of fructose-1,6-bisphosphatase (FBPase) in Saccharomyces cerevisiae. Fructose-1,6-bisphosphatase, a key enzyme in the gluconeogenesis pathway, is induced when cells are starved of glucose and is degraded when cells are replenished with glucose. We have shown that catabolite inactivation of FBPase is mediated by a selective import of the enzyme into the vacuole (yeast lysosome) for degradation. Glucose-induced degradation of FBPase serves to regulate metabolism to prevent the energy futile cycle. In addition to FBPase, we have also demonstrated that peroxisomes, which are important in the oxidation of fatty acids, are delivered to the vacuole for degradation in response to glucose. Furthermore, the galactose transporter, which is induced when cells are grown in galactose, is internalized and delivered to the vacuole for degradation when cells are transferred to glucose. Key words: protein degradation, yeast vacuole, catabolite inactivation, fructose-1,6-bisphosphatase, galactose permease, autophagic vacuole.
γ-Tubulin and the fungal microtubule cytoskeleton
Authors: Oakley Berl R.
Published: May 2008

γ-Tubulin is present in phylogenetically diverse eukaryotes. It is a component of microtubule organizing centers such as the spindle pole bodies of fungi. In Aspergillus nidulans and Schizosaccharomyces pombe, it is essential for nuclear division, and, thus, for viability. In A. nidulans, nuclei carrying a γ-tubulin disruption can be maintained in heterokaryons, and the phenotypes caused by the disruption can be determined in uninucleate spores produced by the heterokaryons. Experiments with heterokaryons created in strains with mutations that allow synchronization of the cell cycle reveal that γ-tubulin is not required for the transition from the G1phase of the cell cycle through S phase to G2, nor for the entry into mitosis as judged by chromosomal condensation. It is, however, required for the formation of the mitotic spindle and for the successful completion of mitosis. Staining with the MPM-2 monoclonal antibody reveals that spindle pole body replication occurs in the absence of functional γ-tubulin. Finally, human γ-tubulin functions in fission yeast, and this indicates that γ-tubulin has similar functions in widely divergent organisms. Key words: tubulin, microtubule, spindle pole body, microtubule organizing center.
What forces drive cell wall expansion?
Authors: Harold Franklin M. , Harold Ruth L. , Money Nicholas P.
Published: May 2008

Fungal hyphae characteristically extend at the apex, by the localized deposition of new cell wall and plasma membrane. That entails the performance of work and raises the question, what forces drive hyphal extension in the face of surface cohesion and external resistance? Conventional wisdom credits turgor, i.e., hydrostatic pressure, with driving the tip forward and shaping it by plastic deformation. An experimental test of this hypothesis became possible with the discovery that the oomycetes Achlya bisexualis and Saprolegnia ferax do not regulate turgor. When the osmotic pressure of the medium is raised by the addition of sucrose or other osmolytes, the organisms produce a more plastic wall and continue to grow. Saprolegnia ferax produces near-normal hyphae in the absence of any measurable turgor. Responses to variations in the composition of the medium and to a range of inhibitors indicate that the processes responsible for growth are the same in normal hyphae (4 bars; 1 bar = 100 kPa) and in turgorless ones. Our observations imply that hyphal extension in oomycetes has much in common with pseudopod extension in animal cells, in that polymerization of the actin meshwork in the apical region plays an indispensable role. In the extreme case, when turgor is essentially zero and the wall is most plastic, actin polymerization may contribute substantially to the driving force for extension. But when turgor is high and the wall rigid, hydrostatic pressure is likely to be required to stress the wall, allowing it to expand and admit new wall material. Key words: hyphae, turgor, actin, apical growth, tip growth, cell wall.
Cell wall growth and protein secretion in fungi
Authors: Sietsma J. H. , Wösten H. A. B. , Wessels J. G. H.
Published: May 2008

Secretion of proteins is a vital process in fungi. Because hyphal walls form a diffusion barrier for proteins, a mechanism different from diffusion probably exist to transport proteins across the wall. In Schizophyllum commune, evidence has been obtained for synthesis at the hyphal apex of wall components, 1,3-β-glucan and chitin, as separate components. These become subapically cross-linked by formation of covalent and noncovalent bonds, producing a rigid wall (steady-state wall growth). Because the wall at the apex apparently grows by apposition of plastic wall material, proteins excreted at the apex may pass the wall by being carried with the flow of wall material (bulk flow), making pores in the wall less important than previously thought. A large portion of excreted proteins leaves hyphae at the growing apices, another portion is retained by the wall and slowly released from the mature wall into the environment. Among proteins that can be permanently retained by the wall are the hydrophobins that self-assemble at the outer wall surface when confronted with a hydrophilic–hydrophobic interface. They were shown to mediate both the emergence of aerial hyphae and the attachment of hyphae to hydrophobic substrates. Key words: hyphal wall, secretion of proteins, hydrophobins, aerial hyphae, apical growth, hyphal adhesion, wall growth.
Septum formation inAspergillus nidulans
Authors: Momany Michelle , Morrell Jennifer L. , Harris Steven D. , Hamer John E.
Published: May 2008

We are investigating septation in Aspergillus nidulans. We have shown that septum formation is dependent on the third nuclear division and actin is involved in this process. We have also characterized nine temperature-sensitive septation (sep) mutants. On the basis of our analysis we have divided these mutants into three phenotypic classes. We are uncovering the order of events in the septation pathway by analysis of double mutants constructed with different pairs of sep mutants. The sepB gene has been cloned and sequenced. Homology with the Saccharomyces cerevisiae CTF4 gene and the phenotype of the sepB mutant support a role in monitoring the fidelity of chromosome transmission. We are also investigating the role of the asp genes (Aspergillus septins). Three asp genes were identified by homology with the S. cerevisiae septins. aspB has been cloned, sequenced, and fused to a biotinylated tag for antibody production. Antibody production and localization studies are now underway. Because septation requires the integration of several cellular processes, our studies should give insight into the cell cycle, cell wall biosnythesis and development of A. nidulans. Key words: septation, cytokinesis, Aspergillus nidulans.
Convergent insights into mechanisms determining disease and resistance response in plant–fungal interactions
Authors: Johal G. S. , Gray J. , Gruis D. , Briggs S. P.
Published: May 2008

In this review, an attempt has been made to scrutinize mechanisms controlling disease or resistance from the perspective of biological forces and constraints affecting co-evolution of a fungal pathogen with its plant host. We reckon that plants are naturally resistant to almost all potentially pathogenic organisms. Defense mechanisms responsible for this default resistance, also termed nonhost or general resistance, are many and include both physical and chemical factors triggered rapidly in response to attempted infection. Pathogenic organisms have to contend with these mechanisms before they can succeed in colonizing a plant. It appears that two different strategies, biotrophic and necrotrophic, have evolved in fungi for this purpose. In the former, defenses are not allowed to be triggered, and in the latter these mechanisms are suppressed or nullified. Consequently, two different kinds of resistance mechanisms have evolved in plants. Against biotrophs, resistance genes function to ensure that normal plant defenses are triggered in time to keep the plant resistant to the pathogen. Against necrotrophs, resistance genes operate to negate the key pathogenic strategy of the invader. Further evolution between the host and the pathogen, and hence durability of a disease resistance gene, is governed by the importance of the fungal target of a disease resistance gene in plant pathogenesis. Key words: disease resistance, plant–fungal interaction, plant pathogenesis, gene-for-gene interaction, defense mechanisms.
Molecular aspects of avirulence genes of the tomato pathogenCladosporium fulvum
Authors: Wit Pierre J. G. M. de , Joosten Matthieu H. A. J. , Honée Guy , Vossen Paul J. M. J. , Cozijnsen Ton J. , Kooman-Gersmann Miriam , Vogelsang Ralph
Published: May 2008

Host genotype specificity in interactions between biotrophic fungal pathogens and plants in most cases complies with the gene-for-gene model. Success or failure of infection is determined by the absence or presence of complementary genes, avirulence and resistance genes, in the pathogen and the host plant, respectively. Resistance, expressed by the induction of a hypersensitive response followed by other defence responses in the host, is envisaged to be based on recognition of the pathogen, mediated through direct interaction between products of avirulence genes of the pathogen (the so-called race-specific elicitors) and receptors in the host plant, the putative products of resistance genes. The interaction between the biotrophic fungus Cladosporium fulvum and its only host, tomato, is a model system to study fungus–plant gene-for-gene relationships. Here we review research on isolation, characterization, and biological function of two race-specific elicitors AVR4 and AVR9 of C. fulvum and cloning and regulation of their encoding genes. Key words: avirulence genes, race-specific elicitors, resistance genes, hypersensitive response, host defense responses.
Elicitor-binding proteins and signal transduction in the activation of a phytoalexin defense response
Authors: Ebel Jürgen , Feger Markus , Kissel Ulrich , Mithöfer Axel , Waldmüller Tom , Bhagwat Arvind A. , Cosio Eric G.
Published: May 2008

Inducible plant defenses against potential pathogens are thought to be activated by signal compounds released during early stages of the infection process. In the incompatible interaction between soybean (Glycine max L.) and the oomycete Phytophthora megasperma f.sp. glycinea (= Phytophthora sojae) a rapid, localized phytoalexin response is activated at the level of transcription. The phytoalexin response is also stimulated in various soybean tissues, including cultured cells, following treatment with an elicitor derived from the cell walls of the fungus. The best characterized elicitors of P. megasperma for soybean are the branched (1→3)- and (1→6)-linked β-glucans, structural polysaccharides of the hyphal walls. The glucans are naturally released during the early stages of germination of the fungal cysts in a host-independent manner. Cyclic β-glucans of Bradyrhizobium japonicum USDA 110, a symbiont of soybean, arc not active in inducing phytoalexin production in soybean. When tested in combination, B. japonicum β-glucans inhibited stimulation of phytoalexin accumulation by the fungal glucans. Surface-localized glucan-binding proteins exist in soybean cells that display high affinity and specificity for the fungal β-glucans, including an elicitor-active hepta-β-glucoside fragment derived from the polysaccharide, suggesting that elicitor action involves a transmembrane signalling process. The main component of the soybean β-glucan binding sites appears to be a 70-kDa protein. Hepta-β-glucoside binding sites exist in several other legumes, such as bean (Phaseolus vulgaris L.), pea (Pisum sativum L.), and lupine (Lupinus albus L.). The signalling process initiated by the β-glucan elicitor, which leads to the activation of the phytoalexin defense response in soybean, involves changes in the permeability of the plasma membrane to Ca2+and H+. Chloride channel antagonists are more efficient than calcium channel antagonists in inhibiting both the phytoalexin response and the inducible ion fluxes. The results present evidence that the observed permeability changes of the plasma membrane are primary events in the transduction of the elicitor signal(s) by the challenged soybean cells. Key words: soybean (Glycine max), Phytophthora megasperma f.sp. glycinea, β-glucan elicitor, elicitor-binding proteins, phytoalexins, Ca2+.
Fungal gene expression during ectomycorrhiza formation
Authors: Martin F. , Laurent P. , Carvalho D. de , Burgess T. , Murphy P. , Nehls U. , Tagu D.
Published: May 2008

Ectomycorrhiza development involves the differentiation of structurally specialized fungal tissues (e.g., mantle and Hartig net) and an interface between symbionts. Polypeptides presenting a preferential, up-, or down-regulated synthesis have been characterized in several developing ectomycorrhizal associations. Their spatial and temporal expressions have been characterized by cell fractionation, two-dimensional polyacrylamide gel electrophoresis, and immunochemical assays in the Eucalyptus spp. – Pisolithus tinctorius mycorrhizas. These studies have emphasized the importance of fungal cell wall polypeptides during the early stages of the ectomycorrhizal interaction. The increased synthesis of 30- to 32-kDa acidic polypeptides, together with the decreased accumulation of a prominent 95-kDa mannoprotein provided evidence for major alterations of Pisolithus tinctorius cell walls during mycorrhiza formation. Differential cDNA library screening and shotgun cDNA sequencing were used to clone symbiosis-regulated fungal genes. Several abundant transcripts showed a significant amino acid sequence similarity to a family of secreted morphogenetic fungal proteins, the so-called hydrophobic. In P. tinctorius, the content of hydrophobin transcripts is high in aerial hyphae and during the ectomycorrhizal sheath formation. Alteration of cell walls and the extracellular matrix is therefore a key event in the ectomycorrhiza development. An understanding of the molecular mechanisms that underlies the temporal and spatial control of genes and proteins involved in the development of the symbiotic interface is now within reach, as more sophisticated techniques of molecular and genetic analysis are applied to the mycorrhizal interactions. Key words: cell walls, ectomycorrhiza, ectomycorrhizins, fungal development, hydrophobins, symbiosis-regulated polypeptides.
Cell growth and pigment production in suspension cultures of a mycobiont isolated from the lichen Cladonia cristaiella
Authors: Yamamoto Y. , Kinoshita Y. , Kurokawa T. , Yoshimura I. , Ahmadjian V. , Yamada Y.
Published: May 2008

This is the first study on the factors that affect cell growth and the production of secondary metabolites of a lichen mycobiont in liquid culture. An ascospore-derived strain of Cladonia cristatella mycobiont accumulated and excreted red pigments into a liquid medium. Growth of the mycobiont was increased by using liquid Lilly–Barnett medium containing 16% (w/v) sucrose as a carbon source, 0.2% (w/v) L-glutamine as a nitrogen source, and 0.2% (w/v) polypeptone, adjusting pH to 5.0 before autoclaving, and incubating cultures at 20 °C. Pigment production by the mycobiont was increased by using liquid Lilly–Barnett medium containing 4% (w/v) sucrose as a carbon source, 0.2% (w/v) L-asparagine as a nitrogen source, and 0.2% (w/v) malt extract, adjusting pH to 5.0 before autoclaving and incubating cultures at 20 °C. All acetone extracts under any cultural conditions yielded similar HPLC chromatograms. We proved no relationship between cell growth and secondary metabolism based on the nutritional factors in the cultured C. cristatella mycobiont. Key words: lichen, suspension culture, Cladonia cristatella mycobiont, red pigment, production, and growth factor.
Early interactions during powdery mildew infection
Authors: Carver T. L. W. , Ingerson-Morris S. M. , Thomas B. J. , Zeyen R. J.
Published: May 2008

Within minutes of spore deposition, enzymes including cutinase are released by conidia of Erysiphe graminis; these may prepare the infection court and facilitate subsequent fungal development. Germination follows with emergence of the primary germ tube, which contacts the host leaf. Extracellular material is secreted beneath the primary germ tube, which adheres to the leaf. The primary germ tube forms a penetration peg that breaches the host surface and gains access to host cell components including water. The primary germ tube also recognises factor(s) present in the host surface, and this stimulates elongation of the second-formed germ tube. The elongated second tube in turn responds to host surface factor(s) by differentiating an appressorium. Extracellular material, secreted beneath the growing appressorial germ tube, is laid down thickly around the appressorial lobe. An inner ring of extracellular material can often be seen surrounding penetration pores revealed by the removal of primary germ tubes and appressoria. The chemistry of the extracellular material is unknown, but in addition to adhesive properties recent studies show that a monoclonal antibody that recognises purified cutinase and, possibly, hemicellulases, binds to secretions from conidia, primary germ tubes, and appressoria. External factors can also influence germling development. Although light has little effect on the early stages of germling development, it has a profound effect in delaying the formation of haustoria by apparently mature appressoria. Understanding the control of early pathogen development could indicate avenues for genetic engineering and breeding for disease-resistant plants. Key words: Erysiphe graminis, powdery mildew, primary germ tube (PGT), appressoria, extracellular material.
Secretion and endocytosis at the interface of plants and fungi
Authors: Mendgen K. , Bachem U. , Stark-Urnau M. , Xu H.
Published: May 2008

Secretion products and the uptake of material from the outside of the protoplasts of plants and microbes may influence the mutual interaction in host–parasite systems. Organelles involved in secretion by rust fungi have been characterized using immuno-electron microscopy. Proteins with the C-terminal histidine – aspartic acid – glutamic acid – leucine tetrapeptide (HDEL) signal sequence accumulated in tubular vesicular complexes of the ER in the parasitic phase of the fungi. The tubular complexes were differentiated from smooth cisternae that probably correspond to the Golgi equivalent. In the plant, material was secreted into the papilla and at the same time, endocytosis of 1, 3-β-glucans by clathrin-coated vesicles occurred at the penetration site of the monokaryotic appressorium. During further development of monokaryotic haustoria, different wall layers were produced around these haustoria. Components of those layers were plant cell wall constituents most of which were also detected in the Golgi apparatus. One layer was rich in callose, which is supposed to be synthesized at the plasma membrane. Obviously, endo- and exo-cytosis occur permanently by host and parasite during fungal development within the plant. Key words: Uromyces, Golgi, secretion, endocytosis, high-pressure freezing, Saccharomyces, Vigna sinensis, Vicia faba.
Integration of morphological and molecular data sets in estimating fungal phytogenies
Authors: Lutzoni François , Vilgalys Rytas
Published: May 2008

To provide a clearer picture of fungal species relationships, increased efforts are being made to include both molecular and morphological data sets in phylogenetic studies. This general practice in systematics has raised many unresolved questions and controversies regarding how to best integrate the phylogenetic information revealed by morphological and molecular characters. This is because phylogenetic trees derived using different data sets are rarely identical. Such discrepancies can be due to sampling error, to the use of an inappropriate evolutionary model for a given data set, or to different phylogenetic histories between the organisms and the molecule. Methods have been developed recently to test for heterogeneity among data sets, although none of these methods have been subjected to simulation studies. In this paper we compare three tests: a protocol described by Rodrigo et al., an adapted version of Faith's T-PTP test, and Kishino and Hasegawa's likelihood test. These tests were empirically compared using seven lichenized and nonlichenized Omphalina species and the related species Arrhenia lobata (Basidiomycota, Agaricales) for which nrDNA large subunit sequences and morphological data were gathered. The results of these three tests were inconsistent, Rodrigo's test being the only one suggesting that the two data sets could be combined. One of the three most parsimonious trees obtained from the combined data set with eight species is totally congruent with the relationships among the same eight species in an analysis restricted to the same portion of the nrDNA large subunit but extended to 26 species of Omphalina and related genera. Therefore, the results from phylogenetic analyses of this large molecular data set converged on one of the three most parsimonious topologies generated by the combined data set analysis. This topology was not recovered from either data set when analysed separately. This suggests that Rodrigo's homogeneity test might be better suited than the two other tests for determining if trees obtained from different data sets are sampling statistics of the same phylogenetic history. Key words: data sets heterogeneity, homogeneity test, lichen phylogeny, Omphalina, ribosomal DNA.
From 18S ribosomal sequence data to evolution of morphology among the fungi
Authors: Berbee Mary L. , Taylor John W.
Published: May 2008

From ribosomal DNA sequence data we can estimate ascomycete relationships, the time of divergence of major ascomycete lineages, and the history of morphological evolutionary change. Groups long accepted by mycologists such as the filamentous ascomycetes with fruiting bodies, (the plectomycetes and pyrenomycetes) are supported by 18S rDNA sequence data. After generating a phylogenetic tree showing relationships, the geological time of divergence of major fungal lineages may be estimated, inferring elapsed time using the calibrated percent substitutions between sequences. Determining the pathway of evolution of morphological characters is more difficult than inferring the relationships among these taxa. To establish the history of morphological evolution, we need accurate trees receiving strong support from our data set. We also need taxa with the intermediate characters to reveal the sequence of events in morphological evolution. Soon, however, we may be able to take a more direct approach to evolution of morphological characters, sequencing the genes that code for the character. Key words: fungus evolution, ascomycete phylogeny.
Molecules and morphology in basidiomycete phylogeny
Authors: McLaughlin D. J. , Berres M. E. , Szabo L. J.
Published: May 2008

To obtain an understanding of the relationships of the basidiomycetes, especially those with horizontally partitioned metabasidia, and of the evolution of structural characters, members of nine orders and an additional four genera of simple-septate fungi (Auriculariales sensu lato) were studied using cladistic analysis of light microscopic and ultrastructural characters. Comparisons were made with the nucleotide sequence from the 5′ end of the nuclear large subunit ribosomal RNA gene analyzed with several algorithms, including parsimony and maximum likelihood. Analyses of both morphological and molecular characters support similar phylogenetic conclusions, but polarization of some morphological characters was difficult without guidance from molecular data. The Uredinales are shown to be an advanced taxon arising from the simple-septate Auriculariales sensu lato, and some characters that they share with the ascomycetes result from convergent evolution. The simple-septate Auriculariales consists of more than one clade, and the related gasteroid Pachnocybe ferruginea possesses numerous derived light microscopic characters, including holobasidia. Key words: basidiomycetes, character evolution, cladistics, molecular evolution, phylogeny.
Searching for homologous ultrastructural characters in zoosporic fungi
Authors: Powell Martha J. , Blackwell Will H.
Published: May 2008

One aim of ultrastructural studies of motile cells of Oomycetes and Chytridiomycetes, two groups of organisms recognized to have evolved along distinct lineages, has been to compile data bases of characters for reconstruction of phylogenetic hypotheses. Because little is known about the ontogeny, composition, and function of many structures that might be useful, assuming homology owing to similarity in ultrastructural form is problematic. In this paper we explore approaches to elucidating homologies between single membrane bounded organelles in zoospores. We use K-bodies of Oomycete zoospores as an example of an organelle for which ontogenic studies have revealed that certain morphological forms are analogous to other forms. Results of these studies demonstrate that as a morphological character K-body structure can be valuable among subgroups of Oomycetes, but convergence in structure makes it unreliable as a comparative character across the class. Although comparative morphology as an avenue to understanding phylogeny is sometimes challenged, this approach can provide valuable insights into processes involved in organellar evolution. Key words: Chytridiomycetes, Oomycetes, organelles, systematics, ultrastructure, zoospores.
The application of spore surface features in defining taxonomic versus ecological groupings in oomycete fungi
Authors: Beakes G. W. , Burr A. W. , Wood S. E. , Hardham A. R.
Published: May 2008

The origin and structure of cyst surface components in oomycete fungi are described in relation to evaluating their use as taxonomic markers. The ontogeny, biochemistry, and morphological variations in the populations of peripheral vesicles that occur in the zoospores of members of the Peronosporomycetidae and Saprolegniomycetidae, which are discharged upon encystment to give rise to spore surface components, are reviewed. The use of the ornamentation of the cyst coat to define genera within the Saprolegniomycetidae and as an indicator of geographical and host-specific clones within a species of Saprolegnia are reviewed. The cyst coat of the fish pathogen Saprolegnia parasitica shows considerable morphological diversity that appears to be independent of the geographic origin of isolates. There is an indication that a group of isolates with variable, relatively short, spines form a separate clone from those with larger hooped bundles. The monoclonal antibody probes that have been generated to spore surface components of Saprolegnia parasitica, Pythiwn aphanidermatum, and Phytophthora cinnamomi are summarized and their use in defining taxonomic groups reviewed. The antibodies show different levels of specificity ranging from isolate- to order-specific reactions. The degree of specificity can be influenced in some cases by the immunoassay method used. These studies indicate that surface structures and molecules provide extremely versatile and valuable markers for use in oomycete taxonomy and phylogeny. Key words: Saprolegnia, Phytophthora, Achlya, oomycete, zoospore, cysts, ultrastructure, monoclonal antibodies, taxonomy.
Phylogeny in the genus Penicillium: a morphologist's perspective
Authors: Pitt J. I.
Published: May 2008

Great advances have taken place in our understanding of the taxonomy of Penicillium and its teleomorphs in the past 15 years. Physiological and biochemical techniques, applied in conjunction with morphology, have enabled the taxonomy of this difficult genus to approach consensus. Such information, plus existing molecular data, have been used here to construct a hypothetical phylogeny. The proposed phylogeny is based on a number of postulates, including the following: (i) evolution has proceeded from holomorph to strict anamorph; (ii) an intermediate stage exists, the sclerotigenic anamorph; (iii) Eupenicillium and Talaromyces, the Penicillium holomorphs, are of separate (though related) origin; (iv) species in Penicillium have arisen on multiple occasions from these holomorphic genera; and (v) evolution among Penicillium species is away from floccose growth and sparsely produced penicilli, away from irregular penicilli, and away from the soil habitat. Physiologically, evolution is towards growth at low temperature and low water activity and towards mycotoxin production. These and other criteria have been used to construct a hypothetical phylogeny of the major species in Talaromyces, Eupenicillium, and Penicillium, which is offered as a framework for future molecular studies. Key words: Penicillium phylogeny, taxonomy, evolution.
Secondary metabolites and systematic arrangement within the Xylariaceae
Authors: Whalley A. J. S. , Edwards R. L.
Published: May 2008

The Xylariaceae is a large family (Xylariales, Ascomycotina) of 36 or more genera. Secondary metabolites produced by representatives from at least one third of these genera have now been isolated and identified. The major compounds, which are produced in static culture, can be grouped as dihydroisocoumarins, punctaporonins, cytochalasins, butyrolactones and succinic acid derivatives. The distribution of these and other chemicals identified has been used in conjunction with traditional taxonomic characters in an attempt to develop a better understanding of natural relationships within the family. Chemical data obtained to date indicates that there are at least two major divisions within the family. It also provides additional evidence in support of a number of intergeneric associations. Individual species can often be recognised on the basis of exclusive metabolite profiles. The significance of these data and how they relate to current taxonomic views about the Xylariaceae is critically reviewed. Key words: Xylariaceae, chemotaxonomy, fungal secondary metabolites.
Ascomal evolution of filamentous ascomycetes: evidence from molecular data
Authors: Spatafora Joseph W.
Published: May 2008

Phylogenetic analyses of nucleotide data from partial sequences (1150 bp) of the small subunit ribosomal DNA (SSU rDNA) were performed on 30 taxa representing several orders of Hymenoascomycetes and Loculoascomycetes. These analyses detected four major groups of filamentous ascomycetes: group 1, pyrenomycetes (Hypocreales, Microascales, Diaporthales, Sordariales) and loculoascomycetes (Pleosporales); group 2, operculate discomycetes (Pezizales); group 3, inoperculate discomycetes (Geoglossaceae); and group 4, plectomycetes (Eurotiales, Onygenales) and loculoascomycetes (Chaetothyriales). Well-supported clades, which correspond to groupings based on ascomal morphology, were resolved; however, the monophyly of the classes Hymenoascomycetes and Loculoascomycetes was rejected. The placement of the root on the filamentous ascomycete ingroup proved more problematic than resolving the ingroup relationships. Three alternative rooting possibilities, which were identified in suboptimal parsimony trees, were not significantly less likely in maximum likelihood ratio tests. Nonetheless, the most likely topology obtained from fastDNAml was identical to the most parsimonious tree. Key words: filamentous ascomycetes, Hymenoascomycetes, Loculoascomycetes, parsimony, maximum likelihood, ribosomal DNA.
Contributions of mating studies to mushroom systematics
Authors: Petersen Ronald H.
Published: May 2008

Three general topics are included. First, a summary of knowledge of mating systems in several genera is furnished, with discussion concerning individual species. Second, the consequence of mating studies in expansion or contraction of numbers of accepted names is discussed. Inherent in this topic is the species concept to be used by the systematis. Third, guidelines for establishment of standard batteries of tester strains are outlined, using Pleurotus as an example. Key words: mating systems, Agaricales, Pleurotus, systematics.
Corticioid fungi: a cladistic study of a paraphyletic group
Authors: Parmasto Erast
Published: May 2008

Cladistic analyses were used to assess monophyly for genera of corticioid fungi (Hymenomycetes, Basidiomycota). Based on parsimony analysis, many genera were found to be paraphyletic; to recognize only monophyletic taxa, 50 genera have been synonymized and 142 presumably monophyletic genera retained for further analysis. Over 12 000 equally parsimonious trees are possible for the 142 taxa. Although consensus trees leave much of the phylogeny unresolved, more than 10 monophyletic groups can be distinguished based on 95% majority-rule consensus, including the families Atheliaceae, Botryobasidiaceae, Hericiaceae (syn.: Gloeocystidiellaceae), Peniophoraceae (syn.: Stereaceae), Schizophyllaceae (syn.: Meruliaceae) and Xenasmataceae. The use of representative species in cladistic analysis is not recommended. To avoid the use of paraphyletic genera (and unnecessary nomenclatural changes), robust taxonomic systems are needed which avoid unnecessary splitting. Key words: fungal taxonomy, Hymenomycetes, Corticiaceae, classification.
Two lipases from Candida antarctica: cloning and expression in Aspergillus oryzae
Authors: Høegh Inge , Patkar Shamkant , Halkier Torben , Hansen Mogens T.
Published: May 2008

The basidiomycetous yeast Candida antarctica expresses two lipases that possess widely different properties. The genes LIPA and LIPB encoding both lipases were cloned and sequenced. Both lipases were secreted efficiently from Aspergillus oryzae transformed with lipase expression plasmids. N-Glycosylation was slightly more extensive in the heterologously expressed enzymes than in those purified from C. antarctica, but the enzymatic characteristics were retained. Both enzymes are encoded as preproenzymes. Proteolytic processing of the primary translation product was efficient in A. oryzae and resulted in the same N-terminals as in C. antarctica. Modifications or deletions of the propeptide of lipase component B did not prevent efficient secretion of active lipase from A. oryzae. Alternative proteolytic processing of the modified propeptides was detected. Key words: Lipase, Candida, cloning, Aspergillus, expression, propeptide.
Protein production by the filamentous fungus Trichoderma reesei: secretion of active antibody molecules
Authors: Nyyssönen Eini , Keränen Sirkka , Penttilä Merja , Demolder Jan , Contreras Roland
Published: May 2008

Trichoderma reesei is used by industry for production of plant material hydrolysing enzymes, especially cellulases. The fungus has excellent production and secretion capacity. The major cellulase cellobiohydrolase I (CBHI) represents half of the protein secreted and is encoded by a single copy gene. The strong cbh1 promoter and other promoters regulated in a different manner are available for protein production. The potential of the fungus in foreign protein production has been demonstrated by the expression of chymosin, interleukin-6, and laccase. Antibodies and their engineered forms have numerous applications. The capacity of Trichoderma to produce different forms of antibodies such as Fab molecules under the cbh1 promoter was analysed. When light chain was produced alone the secreted yields were very low but could be increased by introducing the heavy-Fd chain into the fungus. When the heavy-Fd chain was fused to the C-terminus of the CBHI core-linker region, production of secreted Fab's was increased about 50-fold. The amount of immunologically active CBHI – Fab molecules was about 150 mg/L in the medium in a fermenter cultivation. The released Fab molecules were authentic in their immunological properties demonstrating functional assembly of the light and heavy chains. The antibody part can be released from the CBHI fusion by an unidentified fungal protease or Kex2. The beneficial role of CBHI could be explained by more efficient transcription, ER entry or folding, or passage through the secretory pathway in general. Key words: heterologous expression, fusion protein, CBHI, Fab, single chain antibody.
Secondary metabolites with nematicidal and antimicrobial activity from nematophagous fungi and Ascomycetes
Authors: Anke H. , Stadler M. , Mayer A. , Sterner O.
Published: May 2008

Screening of nematode-trapping fungi for antimicrobial and nematicidal activities gave three new antimicrobial metabolites from cultures of five Arthrobotrys strains. The compounds exhibited no nematicidal activities towards Caenorhabditis elegans and Meloidogyne incognita. From trap-forming submerged cultures of Arthrobotrys conoides, linoleic acid was isolated as a nematicidal principle. Its production increased with the number of traps formed in both Arthrobotrys oligospora and Arthrobotrys conoides. Nematoctonus robustus and Nematoctonus concurrens produced pleurotin, dihydropleurotinic acid, and leucopleurotin, metabolites previously isolated from cultures of Hohenbuehelia species, suggesting that the same biosynthetic pathways function in both the teleomorph and anamorph. Several strains of Ascomycetes had nematicidal activities; linoleic acid was responsible for the activity in cultures of a Chlorosplenium species, 14-epicochlioquinone B in cultures of Neobulgaria pura, and two naphthalenes derived from the melanin biosynthetic pathway in Daldinia concentrica. 5-Pentyl-2-furaldehyde, previously known as a metabolite from a Basidiomycete, was produced by an unidentified Australian Ascomycete. More than 30 mostly new metabolites have been isolated from cultures of Lachnum papyraceum, many being chlorinated. Under different conditions the fungus incorporated bromine instead of chlorine. Key words: nematophagous fungi, natural nematicides, linoleic acid, chlorinated secondary metabolites.
New isolation methods and polymerase chain reaction strain discrimination techniques for natural products screening programs
Authors: Okuda Toru , Yanagisawa Mieko , Fujimori Fumihiro , Nishizuka Yuri , Takehana Yuki , Sugiyama Masato
Published: May 2008

A new isolation method of fungi was established by using the Percoll density gradient centrifugation. We found that the difference in the specific gravity allowed us to separate mixtures of fungal spores of Aspergillus, Fusarium, Listeromyces, Penicillium, and Trichoderma. When this technique was applied to soil samples, a wider variety of fungi were isolated compared with those obtained from an ordinary serial dilution method. For screening purposes, it is necessary to eliminate redundant strains from the strains initially isolated. For the efficient discrimination of strains, the random amplified polymorphic DNA (RAPD) method was applied. The establishment of a standard method for RAPD enabled us to minimize the deviation of Rf values between gels to less than 0.03. Conversion of the Rf values to binary matrices provided a matrix data that could be analyzed statistically. Based on the RAPD, it was possible to select genetically distinct fungal strains within a species. Key words: fingerprinting, isolation method, microbial screening, PCR, Percoll density gradient, RAPD.