bluuebunny/crossref_metadata_2025 huggingface dataset:
Sphingosine-related mycotoxins in plant and animal diseases
Authors: Gilchrist David G. , Bostock Richard M. , Wang Hong
Published: May 2008

The AAL-toxins and fumonisins are a group of chemically related phytotoxic congeners produced by Alternaria alternata f. sp. lycopersici and Fusarium moniliforme, respectively, that also are widespread mycotoxins with important health implications. These mycotoxins, which bear a structural relationship to the sphingoid base, sphingosine, also incite maladies in animals ranging from neoplasms to renal, neural, and hepatic necrosis. A. alternata f. sp. lycopersici causes the Alternaria stem canker disease in tomatoes, while F. moniliforme causes pink ear rot of maize and is associated with post-harvest contamination of many different food staples. These toxins are potent inhibitors of ceramide synthase in plants and animals. Sphingoid bases are mediators of signal transduction leading to neoplasms and necrosis in animals. Significant inhibition of ceramide synthase in microsomal preparations of tomato occurs at 20 nM with an I50in the range of 35–40 nM for both AAL-toxin, TA, and fumonisin, FB1. In plants, specific alterations of physiological processes associated with cellular response to these toxins appears to be required for cell death. A net decrease in sucrose influx to treated leaves occurs within 4 h of AAL-toxin treatment. Untreated leaves of toxin-resistant and -sensitive isolines of tomato show significant differences in sucrose transport capacity. Exogenous application of sucrose transport inhibitors mimicked AAL-toxin symptoms and enhanced cell death in susceptible lines of tomato. Conversely, the accumulation of the ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACQ occurred in 1 h and increased rapidly during the next 6 h after exposure to AAL-toxin. ACC accumulation is followed by a burst in ethylene within 12 h. Application of specific inhibitors of ethylene synthesis or ethylene action results in a decrease in toxin-induced cell death. These toxins appear to be useful tools for defining biochemical and molecular features common to induced cell death in both plants and animals. Key words: AAL-toxins, fumonisins, mycotoxins, host-selective toxins, Alternaria stem canker, Alternaria alternata, Fusarium moniliforme.
Plant disease resistance genes: unravelling how they work
Authors: Hammond-Kosack Kim E. , Jones Jonathan D. G.
Published: May 2008

Resistance (R) genes confer on a plant the ability to defend itself following microbial attack. Each R gene exhibits an extreme specificity of action and is only effective against a microbe that has the corresponding functional avirulence (Avr) gene. This article reviews the strategies and experimental approaches deployed to understand the molecular events underlying the specificity of action of various tomato Cf resistance genes that results in incompatibility to the fungal pathogen Cladosporium fulvum. Topics covered include the clustering of Cf genes, the biology of Cf-dependent incompatibility, the map-based and transposon tagging approaches used to clone the Cf-2 and Cf-9 genes, respectively, identification by mutagenesis of other plant loci required for full Cf-9 mediated resistance, the expression of a functional Avr9 gene in planta and its lethal consequences to Cf-9 containing plants, the physiological and molecular host responses to C. fulvum and AVR elicitor challenges and some genetic approaches to ascertain the crucial components of the defense response. Key words: Cladosporium fulvum, Lycopersicon esculentum, tomato leaf mold, Cf resistance genes, fungal avirulence genes, plant defense responses.
Plant cell wall reinforcement in the disease-resistance response: molecular composition and regulation
Authors: Matern Ulrich , Grimmig Bernhard , Kneusel Richard Edward
Published: May 2008

The disease-resistance response of plant cells is composed of a multitude of biochemical events, and the activation of one of these, the phenylpropanoid metabolism, is pivotal for the survival of cells under stress conditions. The basic features of this facet of the disease-resistance response are beginning to be unraveled in model plant cell culture systems. These studies revealed a novel, alternative pathway for the synthesis of cell wall bound hydroxycinnamoyl esters and lignin. The investigations have, therefore, set the stage for a detailed analysis of the induction process that includes fast, posttranslational activation mechanisms as well as de novo enzyme synthesis. The biosynthesis of phenolic compounds destined for the cell wall is considered to reach far beyond the mere physical strengthening of the cells and includes additional functions, e.g., the release of antimycotic hydroxybenzaldehydes, which are vital for stress compensation. Key words: elicitor-induced phenylpropanoids, cell wall reinforcement, hydroxycinnamoyl esters, lignin, caffeoyl-CoA-specific 3-O-methyltransferase, disease resistance response, parsley (Petroselinum crispum) cell cultures.
Detoxification of phytoanticipins and phytoalexins by phytopathogenic fungi
Authors: VanEtten Hans D. , Sandrock Robert W. , Wasmann Catherine C. , Soby Scott D. , McCluskey Kevin , Wang Ping
Published: May 2008

Most plants synthesize antimicrobial compounds as part of normal plant development (i.e., phytoanticipins) or synthesize such compounds de novo when challenged by microorganisms (i.e., phytoalexins). The presumed role of these plant antibiotics is to protect the plant from disease. However, many phytopathogenic fungi have enzymes that can detoxify the phytoanticipins or phytoalexins produced by their host. This may be a means that these pathogens have evolved to circumvent resistance mechanisms based on the production of plant antibiotics. Many of the phytoanticipin- and phytoalexin-detoxifying enzymes produced by phytopathogenic fungi have biochemical and regulatory properties that would indicate the phytoanticipins and phytoalexins produced by their host are their normal substrates. In addition, their activity, enzymatic products, or transcripts can be detected in infected plant tissue suggesting that they are functioning in planta during pathogenesis. Specific mutations have been made by transformation-mediated gene-disruption procedures that eliminate the ability of Gaeumannomyces graminis var. avenae, Gloeocercospora sorghi, and Nectria haematococca to detoxify the phytoanticipins or phytoalexins produced by their hosts. The effect of these mutations on pathogenicity indicates a requirement for detoxifying enzymes in G. graminis var. avenae but not in G. sorghi or N. haematococca. Key words: disease resistance, pathogenicity mechanisms, isoflavonoids, saponins, cyanide.
Changes in carbon partitioning or allocation due to ectomycorrhiza formation: biochemical evidence
Authors: Hampp R. , Schaeffer C. , Wallenda T. , Stülten C. , Johann P. , Einig W.
Published: May 2008

Based on the in vitro synthesis of ectomycorrhizas between spruce seedlings and different fungal partners we assessed biochemical parameters connected to the regulation of both formation and utilization of sucrose. Mycorrhization of 4-month-old seedlings resulted in an increase of the activity of sucrose phosphate synthase, a key enzyme in the cytosolic formation of sucrose in source leaves. In parallel, the concentration of fructose 2, 6-bisphosphate (F26BP), a potent inhibitor of fructose 1, 6-bisphosphatase (FBPase), was decreased in needles. Both changes indicate an increased capacity for sucrose formation in mycorrhizal seedlings. To examine the fate of sucrose in the root, we compared transport properties of protoplasts from mycorrhiza-forming fungi (Amanita muscaria, Cenococcum geophilum) with apoplastic sucrose metabolism. Protoplasts from A. muscaria preferentially took up glucose (KM, 1.25 mM; Vmax, 18 pmol/(106 protoplasts∙min)), while sucrose was not transported. This is in accordance with the restriction of invertase activity (sucrose hydrolysis) to the host tissue. A distinction of different zones of symbiotic interaction (analysis of 0.5-mm-wide sections from the tip towards the base of single Picea abies – A. muscaria mycorrhizas) showed a decrease of sucrose in the zones exhibiting the highest fungal proportion (ergosterol), which was paralleled by a concomitant increase in trehalose. In addition, these zones of symbiotic interaction were characterized by high levels of F26BP (up to 1.8 pmol/mg dry weight), which exceeded those resulting from a mere addition of the levels contained in the single partners. An assay of potentially F26BP stimulated enzymes (phosphofructokinase (PFK), PPi-dependent fructose-6-phosphate phosphotransferase (PFP)) revealed that in fungal extracts PFK was stimulated by F26BP while in host tissue it was PFP. This partner-specific difference in stimulation by F26BP could play a pivotal role in creating the strong sink activity in mycorrhizal roots. Possible implications on the partner-specific regulation of glycolysis are discussed. Key words: carbon allocation, ectomycorrhizal symbiosis, fructose 2, 6-bisphosphate, hexose transport, regulation of glycolysis, sucrose metabolism.
Development, regeneration, and parasitic interactions between the lichens Fulgensia bracteata and Toninia caeruleonigricans
Authors: Ott Sieglinde , Meier Thomas , Jahns Hans Martin
Published: May 2008

A possible source of Trebouxia algae for lichens are the thalli of lichens that are attacked by another mycobiont that captures the algae for its own symbiotic use. Such a process is described for Fulgensia bracteata living in parasitic association with Toninia caeruleonigricans. The development of the thalli of Toninia and the parasitic attack of Fulgensia are analysed in detail. The infection of Toninia is achieved by ascospores and can be demonstrated by the presence of secondary lichen substances typical for Fulgensia, which occur in infected thalli of Toninia. Fulgensia also overgrows other lichens, but these thalli are not invaded. The special abilities of Toninia and various methods for distribution and regeneration compensate for the parasitism and the association remains stable. The ecology of the small developmental stages of Toninia and Fulgensia shows important differences. Key words: Fulgensia, Toninia, Trebouxia development, parasitism, ecology.
The chemical ecology of lichen mycoparasites: a review
Authors: Lawrey James D.
Published: May 2008

Lichenicolous fungi colonize lichens to form a variety of biotrophic associations, and while some 300 genera and 1000 species have been recognized, almost nothing is known about their biology. The lichenicolous habit is an unusual one because lichens produce a variety of antibiotic secondary metabolites that are assumed to protect them from parasitic attack. This may explain why lichens are rarely parasitized in nature while nonlichen-forming Ascomycetes are frequently and extensively parasitized. Recent field and laboratory studies of lichen parasites from a number of fungal groups indicate that chemistry is indeed involved in these interactions. These results indicate that (i) lichenicolous taxa are better able to degrade lichens than related nonlichenicolous taxa, (ii) lichen parasites are generally tolerant of lichen secondary metabolites, (iii) this tolerance seems to be based in part on the ability of cell wall degrading enzymes of parasites to remain active in the presence of these lichen secondary metabolites, and (iv) the host preferences of some lichen parasites reflect these tolerances. Therefore, it appears likely that lichenicolous fungi, which have presumably had lengthy coevolutionary histories with lichens, have evolved a unique mode of nutrition that is based in part on an ability to tolerate lichen defense compounds. Key words: Hobsonia, lichens, lichenicolous fungi, Nectria, parasites.
Signal exchange between higher plants and rust fungi
Authors: Heath Michèle C.
Published: May 2008

The rust fungi appear to have evolved a sophisticated complex of molecular interactions with their host plants that govern both plant resistance and susceptibility. It is suggested that many of these interactions relate to the maintenance and effective exploitation of biotrophy, and that host specificity and the obligacy of parasitism are a consequence of the resulting interactive molecular control of plant and fungal activities. For the dikaryon, plant signals are required for locating stomata and the formation of infection structures, haustorial mother cells, and haustoria. Host susceptibility to both the monokaryon and the dikaryon appears to involve the suppression of defensive secretory processes, the induction of cellular alterations in invaded cells, and, for the dikaryon at least, changes in nutrient translocation. Parasite-specific resistance involves cultivar-specific fungal signals (elicitors) of defense responses such as cell death and callose deposition. The nature of, and evidence for, the signals involved in these interactions are reviewed. Key words: biotrophy, elicitors, rust fungi, signal exchange.
Differentiation and cell wall degrading enzymes in the obligately biotrophic rust fungus Uromyces viciae-fabae
Authors: Deising Holger , Rauscher Martina , Haug Marc , Heiler Stefan
Published: May 2008

Rust fungi differentiate a series of complex infection structures to infect their host plants. Artificial membranes providing a signal for the induction of infection structure differentiation have been used to study events taking place during early stages of host–pathogen interaction. During the prepenetration phase, serine esterases, one of which shows cutinase activity, appear to be important for adhesion of uredospores of Uromyces viciae-fabae to the plant cuticle. When the fungus grows through the stomatal opening, chitin deacetylase activity increases drastically. The role of this enzyme in masking and preventing degradation of fungal structures by plant chitinases is discussed. Different isoforms of protease, cellulase, and pectin methylesterases (PME) are formed when the fungus enters the intercellular space, and synthesis of polygalacturonate lyase (PL) coincides with formation of haustorial mother cells. Based on the physicochemical and catalytic properties of these cell wall degrading enzymes a model is presented that explains highly localized breaching of plant cell walls by obligate biotrophs. cDNAs corresponding to genes activated during late stages of infection structure differentiation of Uromyces viciae-fabae have been isolated by differential hybridization. The transcripts of the genes designated rif16 and rif21 occur when haustorial mother cells are formed, and the corresponding gene products may thus be important for successful infection. Key words: adhesion, cell wall degrading enzymes, chitin deacetylase, infection structure differentiation, penetration process, rif genes.
Sexual reproduction in thePeronosporomycetes(chromistan fungi)
Authors: Dick Michael W.
Published: May 2008

An overview of sexual reproduction in the Peronosporomycetes leads to the recognition of constant features and variable traits. Variation in characters is accorded different weighting depending on its use for taxonomic identification or phylogenetic systematics. The phylogenetic significance of features of gametangial morphogenesis, such as vacuolation and the patterns of nuclear meioses and abortions, can be related to morphological characters such as the persistence of periplasm and oogonial and oospore wall deposition. The cellular reorganization occurring in the oogonium and oospores, particularly in relation to the possible functions of the dense body vesicle system and the glucan, phosphate, and lipid oospore reserves, may be critical for the internal morphology of the mature oospore and its function. Such differences are valuable for morphometric analysis, which lends itself to new identification procedures. The ecological implications of these differences in the production of oogonia and oospores are considered; sexual reproduction (its frequency or absence) may be crucial for successful life-history strategies in biodiversity. Key words: meiosis, karyogamy, syngamy, morphogenesis, morphometry, wall membranes.
Classical morphology in zygomycete taxonomy
Authors: Benny Gerald L.
Published: May 2008

Classification of Zygomycetes has evolved with the description of new taxa and the rediscovery and redescription of known species. Taxonomy of orders in Zygomycetes is based on the morphology of the spore forming structures, sporangia and (or) sporangiola, or merosporangia. Some organisms produce only zygospores, azygospores, chlamydospores, or a combination of these structures. The occurrence and morphology of any of the aforementioned structures and others (e.g., stolons and rhizoids, apophyses, branching pattern, fertile vesicles) are used to ascertain the phylogenetic relationships in Mucorales. Our understanding of the morphology, development, and phylogeny of Zygomycetes has been enhanced by using microscopic observations and cladistic analysis of data sets derived both from small subunit rDNA and morphology. Many morphological characters (e.g., trophocyst, yeast cell formation) still appear to be reliable phylogenetic indicators while others (e.g., spore morphology) are too variable. The value of zygospore morphology is reduced because the sexual spore has never been reported for many taxa. Many characters used to circumscribe mucoralean families probably do not indicate relationships but still are useful in identification. Sporangiola should be considered indistinct from sporangia. Key words: cladistics, morphology, Mucorales, phylogeny, sporangia, sporangiola.
Eumycetozoans and molecular systematics
Authors: Spiegel F. W. , Lee S. B. , Rusk S. A.
Published: May 2008

Eumycetozoans, the myxomycetes, protostelids, and dictyostelids, were first hypothesized to be a monophyletic group by L.S. Olive, who suggested that the primitive members of the group were similar to some of the extant protostelids. A review of morphological evidence supporting some aspects of this hypothesis is presented along with explicit explanations of the shortcomings of morphological data as tests of other aspects. For the hypothesis to be supported, modified, or rejected, data from other areas such as the sequences of the nuclear ribosomal small subunit genes (SSrDNA) will have to be used. Presently, sequences for this gene are known only from Physarum polycephalum and Dictyostelium discoideum. These two slime molds are treated as separate, deep clades in the grand eukaryote phylogenies derived from the sequences of SSrDNA. That is, each species represents an independent lineage that diverged early in the history of the eukaryotes. Insufficient taxon sampling may account for the molecular trees which suggest that the dictyostelids and myxomycetes are not members of a monophyletic group. We have begun to examine the SSrDNA sequence in the protostelid Protostelium mycophaga. Preliminary phylogenetic reconstructions using 11 eukaryotic outgroups suggest that the protostelids, myxomycetes, and dictyostelids are members of a single monophyletic group which may be most closely related to the Chromista. It is interesting that these results coincide with earlier phylogenetic hypotheses based on the morphological characters of these slime molds. Key words: dictyostelids, myxomycetes, protostelids, ribosomal DNA, slime molds.
Making the Deuteromycota redundant: a practical integration of mitosporic and meiosporic fungi
Authors: Taylor John W.
Published: May 2008

A practical approach to combining mitosporic and meiosporic fungi in one classification is described. The taxonomic data base used with the computer retrieval system Entrez for searching both GenBank and MEDLINE has been revised to conservatively place mitosporic fungi in the appropriate meiosporic taxon, thereby making the Deuteromycota redundant. As more data are available, it will be possible to move mitosporic taxa adjacent to their closest meiosporic relatives at the genus level. Placing mitosporic individuals in meiosporic species, however, is unlikely to be practical in most cases. Key words: Deuteromycota, fungi imperfecti, Entrez, fungal phylogeny, GenBank, fungal classification.
Structure and function of mating type genes inCochliobolusspp. and asexual fungi
Authors: Turgeon B. Gillian , Sharon Amir , Wirsel Stefan , Yamaguchi Kenichi , Christiansen Solveig K. , Yoder Olen C.
Published: May 2008

Mating type (MAT) genes of Cochliobolus heterostrophus have homologs in other heterothallic Cochliobolus spp., in homothallic Cochliobolus spp., and in asexual fungi thought to be taxonomically related to Cochliobolus (e.g., Bipolaris spp.). To examine the cause of asexuality in B. sacchari, its homolog of C. heterostrophus MAT-2 was cloned. The B. sacchari sequence was 98% identical to that of C. heterostrophus MAT-2, the gene conferred homothallism when expressed in a C. heterostrophus MAT-1 strain, and transgenic strains mated with C. heterostrophus MAT-1. Thus the cause of asexuality in B. sacchari is not absence or lack of a functional MAT gene. When the C. heterostrophus MAT genes were expressed in B. sacchari, however, no sexual development occurred, suggesting that this asexual fungus lacks an attribute, other than the mating type gene, which is required for mating. Although cloned MAT genes function upon transformation into recipient strains, they do not confer full fertility. When an homologous or heterologous (e.g., from C. carbonum, C. victoriae, or B. sacchari) MAT gene is transferred into a C. heterostrophus strain of opposite mating type, the strain can self and cross to tester strains of either mating type. However, any transgenic strain carrying both a resident MAT gene and an homologous or heterologous MAT transgene develops normal perithecia but few ascospores in a cross that requires function of the transgene. To determine if the resident MAT gene interferes with function of the transgene, the MAT locus was deleted from the genome of C. heterostrophus and then replaced with the MAT gene of C. heterostrophus, C. carbonum, C. victoriae, or B. sacchari. Interference was eliminated and abundant ascospores were formed when the four transgenic strains were crossed to C. heterostrophus strains of opposite mating type. Key words: asexual fungi, DNA-binding proteins, heterologous expression, transformation.
DNA and ascomycete systematics
Authors: Eriksson Ove E.
Published: May 2008

Present knowledge of different types of RNAs as phylogenetic markers among the fungi is discussed, and examples of phylogenetically informative 18S rRNA signature sequences are given. Such signatures give phylogenetic information that is not provided by parsimony or distance analyses of longer gene sequences. A single signature cannot be used as a decisive criterion for defining taxa, but signature sequences give invaluable hints on phylogenetic relationships and can be included in data matrices as morphological criteria when using parsimony analysis. Key words: DNA, ascomycete phylogeny, signature sequences.
Ultrastructure and taxonomy of the aquatic ascomycetous order Halosphaeriales
Authors: Jones E. B. G.
Published: May 2008

The nomenclatural status of genera of the Halosphaeriaceae (Halosphaeriales, Ascomycotina) is reviewed and a key to the genera is presented. Ten types of ascospore appendage ontogeny in species of the Halosphaeriaceae have been demonstrated at the ultrastructural level and are redescribed and discussed. The family currently comprises 42 genera (with 4 new genera to be erected) with 132 species. Key words: marine Ascomycotina, ascospore appendage ontogeny, evolution, ultrastructure.
Production of foreign proteins in the yeast Pichia pastoris
Authors: Cregg James M. , Higgins David R.
Published: May 2008

The methanol-utilizing yeast Pichia pastoris has been developed as a host system for the production of heterologous proteins of commercial interest. An industrial yeast selected for efficient growth on methanol for biomass generation, P. pastoris is readily grown on defined medium in continuous culture at high volume and density. A unique feature of the expression system is the promoter employed to drive heterologous gene expression, which is derived from the methanol-regulated alcohol oxidase I gene (AOX1) of P. pastoris, one of the most efficient and tightly regulated promoters known. The strength of the AOX1 promoter results in high expression levels in strains harboring only a single integrated copy of a foreign-gene expression cassette. Levels may often be further enhanced through the integration of multiple cassette copies into the P. pastoris genome and strategies to construct and select multicopy cassette strains have been devised. The system is particularly attractive for the secretion of foreign-gene products. Because P. pastoris endogenous protein secretion levels are low, foreign secreted proteins often appear to be virtually the only proteins in the culture broth, a major advantage in processing and purification. Key words: heterologous gene expression, methylotrophic yeast, Pichia pastoris, secretion, glycosylation.
New fungal metabolites as potential antihypercholesterolemics and anticancer agents
Authors: Huang Leeyuan , Lingham Russell B. , Harris Guy H. , Singh Sheo B. , Dufresne Claude , Nallin-Omstead Mary , Bills Gerald F. , Mojena Marina , Sanchez Manuel , Karkas John D. , Gibbs Jackson B. , Clapp Wendy H. , Meinz Maria S. , Silverman Keith C. , Bergstrom James D.
Published: May 2008

Several potent inhibitors of squalence synthetase have been discovered. Zaragozic acid A is produced by several fungi; zaragozic acid B is produced by several strains of Sporormiella intermedia; zaragozic acids C, E, and F are produced by Leptodontidium elatius; zaragozic acids D and D2 are produced by Amauroascus niger. L-731,120 and L-731,128 are minor components and coproduced with zaragozic acids A and B, respectively. Viridiofungins A, B, and C are produced by Trichoderma viride. Viridiofungin A is also produced by an unidentified sterile fungus. Several of the zaragozic acids are also potent inhibitors of farnesyl-protein transferase (FPTase). Inhibitors of FPTase may act as potential anticancer drugs. Chaetomellic acids A and B are produced by a fungus, Chaetomella acutiseta, while fusidienol is produced by Fusidium griseum. All three compounds are potent inhibitors of FPTase. Our experiences suggest that many novel inhibitors of both squalene synthase and FPTase are produced within a diverse phylogenetic array of filamentous fungi. Several of the zaragozic acids are potent inhibitors of both FPTase and squalene synthases. This is consistent with our observations that zaragozic acids and chaetomellic acids share some structural similarity. Key words: natural inhibitors, squalene synthase, farnesyl-protein transferase.
From molecular genetics and secondary metabolism to molecular metabolites and secondary genetics
Authors: Bennett J. W.
Published: May 2008

Secondary metabolites constitute a huge array of low molecular weight natural products that cannot be easily defined. Largely produced by bacteria, fungi, and green plants, they tend to be synthesized after active growth has ceased, in families of similar compounds, often at the same time as species-specific morphological characters become apparent. Although, in many cases, the function that the secondary metabolite performs in the producing organism is unknown, the bioactivity of these compounds has been exploited since prehistoric times as drugs, poisons, food flavoring agents, and so forth. In fungi, the polyketide family is the largest known group of secondary metabolite compounds. Polyketides are synthesized from acetate by a mechanism analogous to fatty acid biosynthesis but involving changes in oxidation level and stereochemistry during the chain-elongation process. The fungal polyketide biosynthetic pathways for aflatoxin and patulin have emerged as model systems. The use of blocked mutants has been an essential part of the research approach for both pathways. Molecular methods of studying fungal secondary metabolites were first used with penicillin and cephalosporin, both of which are amino acid derived. Most of the basic molecular work on polyketides was done with streptomycete-derived compounds; however, enough fungal data are now available to compare fungal and streptomycete polyketide synthases, as well as to map the genes involved in a number of polyketide pathways from both groups. The traditional dogma, derived from classical genetics, that genes for fungal pathways are unlinked, has been overturned. In addition, cloning of structural genes facilitates the formation of hybrid molecules, and we are on the brink of understanding certain regulatory functions. Key words: fungal metabolism, secondary metabolism, polyketide, β-lactam, product discovery.
Selection and breeding of shiitake strains resistant to Trichoderma spp.
Authors: Tokimoto Keisuke , Komatsu Mitsuo
Published: May 2008

Bedlogs of shiitake, Lentinula edodes (Berk.) Pegler, are often attacked by Trichoderma spp. such as T. harzianum Rifai and T. polysporum Rifai, which produce antifungal substances and mycolytic enzymes. However, shiitake is more or less able to reject Trichoderma attacks. Shiitake cultures possess at least five straight-chain alcohols with double and triple bonds, which act as antifungal substances. Trichoderma inoculation tests for shiitake cultures showed that the resistance of shiitake in a wood-powder medium correlated positively with that in bedlogs when T. harzianum was used. Screening assays using the wood-powder medium showed some highly resistant and susceptible strains among 164 different wild shiitake strains. Monokaryons derived from basidiospores of a highly resistant strain, TMI-407, had high rejecting abilities compared with those from a susceptible strain, TMI-1161. Crossing between monokaryons from the two strains revealed that resistance was dominant. In general, these resistant mycelia produced much more antifungal substances than did susceptible mycelia. Key words: Lentinula edodes, shiitake, mushroom cultivation, resistance to Trichoderma spp., selection method, antagonism.
Breeding of edible fungi with emphasis on the variability among French genetic resources ofAgaricus bisporus
Authors: Callac P.
Published: May 2008

Our laboratory (INRA) has developed breeding programs for several species of edible fungi. For example, "sporeless" strains were obtained by mutagenesis for Pleurotus ostreatus and Pleurotus pulmonarius, a hybrid strain of Lepista nuda has been marketed, and genetic variability has been studied in Tuber melanosporum. At present, the largest program concerns Agaricus bisporus, for which a collection of about 200 French isolates from 44 sites has been gathered. High genetic polymorphism appeared even within each site. Nine genetically different isolates from the same site were studied in experimental culture. Variability was observed for color of the cap, susceptibility to bacterial blotch, and the elevated basidial spore number trait. A single isolate, Bs 261, gave sporocarps having a majority of tetrasporic basidia, and spores which, for the most part, were homokaryotic. This strain was interfertile with typical bisporic strains. The resulting hybrids were either bisporic or tetrasporic, according to which homokaryon of Bs 261 was used. More investigations will be necessary to understand the presence of a rare tetrasporic strain in a bisporic population and also to study the relationship between Bs 261 and the tetrasporic strains of the previously described A. bisporus var. burnettii. Key words: edible fungi, Agaricus bisporus, genetic resources, breeding, basidial spore number, tetrasporic trait.
Conservation and management of natural populations of edible fungi
Authors: Arnolds Eef
Published: May 2008

The importance of private and commercial harvest of wild edible mushrooms in Europe and North America is briefly outlined. Possible negative effects of harvesting on the production of sporocarps are discussed. There is no evidence that picking of mushrooms is harmful for subsequent fruiting, except in some cases where mycelia are destroyed. Changes in frequency of edible mushrooms in Europe are described with special emphasis on The Netherlands. The occurrence of edible species on Red Lists of threatened fungi in Europe is discussed. The decline of many ectomycorrhizal species is supposed to be mainly caused by environmental pollution. Relations between harvesting of edible mushrooms, forest management and nature conservation are indicated. Key words: edible mushrooms, mushroom picking, decline of fungi, forest management.
Expression of virulence factors inCandida albicans
Authors: White Theodore C. , Köhler Gerwald A. , Miyasaki Shelley H. , Agabian Nina
Published: May 2008

Virulence in the pathogenic yeast Candida albicans involves the interplay of many complex developmentally and environmentally regulated properties. Morphological and developmental changes such as the yeast–hyphae transition and switch phenotypes identified as colony morphologies result in the differential expression of a variety of cell properties that may include (i) secreted aspartyl proteinase (Sap) enzymatic activity that is now known to be the product of at least seven distinct genes, (ii) azole resistance that can be the result of altered expression of the target enzyme, lanosterol demethylase, or active efflux of azole drugs from the cells that may be facilitated by multidrug resistance genes (MDR genes), and (iii) a variety of Candida antigens that are recognized by patient antisera, including mannoproteins, glycolytic enzymes (especially enolase), heat shock proteins (especially Hsp90), and several Sap isoenzymes. As the details of these systems are elucidated, it becomes important to characterize the interactions between these factors that can lead to pathogenesis. The patterns of expression for genes associated with azole resistance, Sap activity, and potential antigens have been determined during the yeast–hyphae transition and between cell types in the white–opaque switch system of strain WO-1. The results suggest that genes involved in azole resistance and genes encoding potential antigens are not grossly affected by the yeast–hyphae transition or by switching between white and opaque colony morphologies. However, SAP gene expression is strictly controlled by these cell types. Key words: Candida, virulence, proteinase, azole, antigens, switch.
Comparative analysis of the in vivo and in vitro metabolites produced by the entomopathogen Beauveria bassiana
Authors: Boucias D. G. , Mazet I. , Pendland J. , Hung S. Y.
Published: May 2008

Beauveria bassiana, like other insect mycopathogens, has evolved mechanisms to penetrate the insect exoskeleton via germ tubes and to replicate in the host hemocoel. Our initial studies have shown that biologically active metabolites released in the hemolymph during the vegetative growth phase of B. bassiana disrupt the host immune response and metamorphosis. These components cause an immediate reduction in filopodial-producing hemocytes and an increase in the level of serum phenoloxidase. Radiolabeling of tissues explanted from healthy versus infected larvae has demonstrated both the induction and repression of polypeptides in B. bassiana infected hemolymph. None of the polypeptides detected with 35S pulse labeling were responsible for the cytotoxic and insecticidal activities detected in infected hemolymph. Western blots of SDS gels containing chromatographic fractions from healthy and infected sera probed with both antibodies against B. bassiana cell homogenates and culture filtrates contained a complex of antigens. The results of lectin labeling and sodium periodate treatments suggested that carbohydrates were the major epitopes being recognized by both monoclonal and polyclonal probes. Key words: insect mycopathogen, Beauveria bassiana, fungal metabolites, entomopathogen, Spodoptera exigua.
Role of cutinase in the invasion of plants
Authors: Köller Wolfram , Yao Chenglin , Trial Frances , Parker D. M.
Published: May 2008

Cutin as the polymeric component of plant cuticles has to be breached during the direct penetration of plant surfaces by invading fungal pathogens. Several lines of evidence had suggested that cutinases produced under saprophytic growth conditions with cutin as sole carbon source were also involved in the penetration of host surfaces during plant infection. However, retained pathogenicity of cutinase gene disrupted mutants of Magnaporthe grisea and Nectria haematococca was not in support of the model. The controversial involvement of cutinase in plant infection was investigated with Alternaria brassicicola. The fungus produced two cutinase isozymes during saprophytic growth on cutin. The disruption of the single gene CUTAB1 abolished the expression of both isozymes and gene-disrupted transformants lost their trait of utilizing cutin as saprophytic carbon source. However, small amounts of two serine esterases with cutinolytic activities and molecular masses of 31 and 19 kDa continued to be secreted into the extracellular fluid. These two esterases were also expressed on leaves of cabbage during host invasion. In contrast, the two cutinase isozymes expressed by the wild-type strain under saprophytic conditions were not detected on host surfaces. The results indicate that different cutinase isozymes are expressed during saprophytic and parasitic stages of the fungus. Key words: cutinase, cuticle penetration, Alternaria brassicicola, plant infection, saprophyte.
The hematoregulatory peptide, SK&F 107647, in combination with antifungal therapy in murineCandida albicansinfections
Authors: DeMarsh Peter L. , Sucoloski Scott K. , Frey Carrie L. , Pelus Louis M. , Bhatnagar Pradip K. , Koltin Yigal , Actor Paul , Pettaway Stephen R.
Published: May 2008

SK&F 107647, a novel synthetic low molecular weight peptide, has been shown to be a potent hematoregulatory agent. We have previously demonstrated that SK&F 107647 administration can prolong survival in both immunosuppressed and normal mice challenged with the opportunistic fungal pathogen Candida albicans. Additionally, we have determined the effect of prophylactic SK&F 107647 treatment combined with conventional antifungal therapy on the survival of mice challenged with a lethal dose of C. albicans. Prophylactic treatment with SK&F 107647 or therapeutic treatment with the antifungals fluconazole or amphotericin B significantly increased the survival rates of immunosuppressed mice challenged with a lethal dose of C. albicans. However, the combination of SK&F 107647 treatment followed by antifungal therapy resulted in statistically significant increases in survival over that observed with either therapy alone. These results indicated that the hematoregulatory factor(s) elicited by SK&F 107647 enhance the survival of mice treated with conventional therapies in a model of experimental systemic candidiasis. Key words: SK&F 107647, Candida albicans, hematoregulatory, fluconazole, amphotericin B.
Origins and significance of genetic and epigenetic instability in mycelial systems
Authors: Rayner Alan D. M. , Ramsdale Mark , Watkins Zac R.
Published: May 2008

Fungal mycelia can alter their organizational pattern in such ways as to produce alternative phenotypes. The latter allow mycelia to explore for, assimilate, conserve, and redistribute resources in spatially and temporally heterogeneous niches. It is suggested that mycelia produce alternative phenotypes by operating as nonlinear (feedback regulated), hydrodynamic systems with indefinitely expandable (indeterminate) boundaries. As such, mycelia can vary the resistances of hyphal envelopes to deformation and passage of molecules, and of hyphal interiors to displacement of contents, in accord with fortuitous local circumstances. Within the mycelial protoplasm are populations of nuclei and mitochondria. If disparate in genetic content or expression, these organelles can form diverse and unstable relationships that both influence and are influenced by metabolic processes affecting the hydraulic resistances of hyphae. Some of these processes may be autocatalytic, involving the generation, association and dissociation of free radicals and reactive oxygen species. Once initiated, such processes are beyond immediate genetic control. Fungal mycelia therefore epitomize the complex interplays between adaptive (genetic) and nonadaptive (organizational) processes that regulate the short term versatility and long term evolutionary divergence of indeterminate systems. Key words: epigenetics, mycelial development, networks, niche, nonlinearity, speciation.
Fungal competition
Authors: Shearer C. A.
Published: May 2008

Competition among fungal species isolated from a variety of habitats and substrates has been demonstrated frequently with laboratory studies. In some competitive interactions in culture, production of antifungal antibiotics by antagonistic fungi has been reported. Less well known is the extent to which competitive interactions occur in fungal communities in nature, the importance of competition in determining fungal community structure, and whether antifungal antibiotics are important in such interactions. Most field studies of fungal communities have been descriptive. Although such studies provide evidence of pattern in community structure, they do not demonstrate the occurrence of competition. Recent experimental field studies, in which the proportions of interacting fungal species were manipulated, provide more compelling evidence that interspecific competition does occur in nature. Knowledge about the extent of fungal competition in nature and its role in structuring fungal communities would be greatly improved if more of the following kinds of studies were undertaken: (i) experimental field studies involving manipulations of fungal species in a variety of habitats, (ii) comparative field and laboratory studies of the same fungal species, (iii) experimental field studies involving more than two fungal species, (iv) experimental and comparative studies throughout a range of environmental conditions, and (v) field experiments using both antibiotic- and nonantibiotic-producing fungal strains and (or) species. Key words: fungi, competition, community structure, antibiotics.
Biology and ecology of mycoparasitism
Authors: Jeffries Peter
Published: May 2008

The term mycoparasitism applies strictly to those relationships in which one living fungus acts as a nutrient source for another, but fungicolous relationships may also be included in which nutrient exchange has not been shown. Fungicolous fungi have a constant but indeterminate association with another fungus, and it can be difficult to demonstrate a true parasitic relationship. Mycoparasitic relationships can be necrotrophic or biotrophic, and can be classified on the basis of the host–parasite interface as contact necrotrophs, invasive necrotrophs, haustorial biotrophs, intracellular biotrophs, or fusion biotrophs depending on the intimacy of the relationship. In natural ecosystems, it is proposed that mycoparasitic relationships play an important role in the development of fungal communities. Two specific examples have been chosen to illustrate the general principles of mycoparasitism: the necrotrophic invasion of spores of arbuscular mycorrhizal fungi and the biotrophic invasion of mucoralean hosts by haustorial mycoparasites. Key words: mycoparasitism, fungicolous fungi, arbuscular mycorrhizal fungi, fungal ecology.
Nutrient cycling in different terrestrial ecosystems in relation to fungi
Authors: Dighton John
Published: May 2008

Comparisons are made between nutrient cycling systems of arctic tundra, temperate forest, tropical forest, grassland, arable, and desert ecosystems. Detailed nutrient budgets are not given, but general differences between ecosystems are discussed primarily in relation to the role of soil fungi. General discussion reviews the impact of anthropogenic factors, including land management, pollution, and climate change on the role of fungi in nutrient cycling. Areas where further research is needed to complete our understanding of the functional aspects of fungi and nutrient cycling are highlighted and some of the techniques that may be employed are discussed. Key words: nutrient cycling, ecosystems, fungi.
Contrasting Trophic Level Interactions in Lake St. George and Haynes Lake (Ontario, Canada)
Authors: Lafontaine Nathalie , McQueen Donald J.
Published: May 2008

Two small, adjacent kettle lakes in southern Ontario were sampled during spring and summer 1987. The data comprised weekly samples of zooplankton and water chemistry, monthly diel assessments of the densities of pelagic fish and zooplankton found at 1-m depth intervals in the water column, and an annual mark and recapture assessment of the entire fish population. The two lakes had very different community structures. Haynes Lake was characterized by high piscivore numbers, few planktivores, a relatively large assemblage of large bodied zooplankton, low chlorophyll a concentrations, and clear water. Lake St. George had a lower piscivore to planktivore ratio, smaller zooplankton, more chlorophyll a, and murkier water. Comparisons of trophic level biomasses for the two lakes suggested that in both communities, the relationships between piscivores and planktivores and between planktivores and zooplankton were strongly correlated with predator abundances. In the more oligotrophy community (Haynes Lake) this influence extended weakly to the phytoplankton, but in the more eutrophic system, little of the variability in chlorophyll a with respect to total phosphorus could be explained by total zooplankton (or Daphnia) abundance. This suggests that for freshwater pelagic communities, top-down effects may be stronger in more oligotrophic systems.
Effect of Temperature, Season, and Fish Size on Acute Lethality of Suspended Sediments to Coho Salmon (Oncorhynchus kisutch)
Authors: Servizi James A. , Martens Dennis W.
Published: May 2008

Tolerance of underyearling coho salmon (Oncorhynchus kisutch) to Fraser River suspended sediments (SS) at 7 °C was independent of season of the year. However, coho of 0.52 g (4.0 cm) possessed only 35% of the tolerance of larger specimens. Tolerance to SS was temperature dependent, with 96-h LC50 at 1 and 18 °C being 47 and 33%, respectively, of the value at 7 °C. Tolerance was further reduced among underyearling coho which were later found to have a viral kidney infection. Cough reflex, oxygen transfer, oxygen saturation levels, metabolic rates, and capacity to do work all probably affect the relationship between SS tolerance and temperature.
Evaluation of Alternative Models of the Coastal Migration of Adult Fraser River Sockeye Salmon (Oncorhynchus nerka)
Authors: Pascual Miguel A. , Quinn Thomas P.
Published: May 2008

A set of stochastic discrete step models of individual fish movement was developed to investigate the efficiency of compass orientation as a migratory mechanism in the coastal homeward migration of Fraser River sockeye salmon (Oncorhynchus nerka). Ultrasonic tracking data provided empirical values for the required parameters. Alternative movement models were validated by comparing the results of Monte Carlo simulations and known features of sockeye migration: general aspect of individual trajectories, timing, success in reaching the goal, and spatial occurrence. The effect of different headings and directional precisions on the probability of success in reaching the goal were considered. The more complex models captured the essence of observed movement patterns, but the number of fish getting to the goal was lower than expected. Many "modeled" fish were lost in the complex web of channels and inlets characteristic of this area. We conclude that the preference of a compass direction is not a sufficient mechanism to explain the observed migratory behavior of Fraser River sockeye salmon in coastal areas. Other mechanisms, such as negative kinetic responses to water from nonnatal rivers or short-term learning, may prevent the fish from being trapped in complex areas.