Experimental Mycology最新文献

Reid, B., Morris, B. M., and Gow, N. A. R. 1995. Calcium-dependent, genus-specific, autoaggregation of zoospores of phytopathogenic fungi. Experimental Mycology , 19, 202-213. Dense populations of zoospores of Phytophthora palmivora , Pythium catenulatum, and Pythium dissotocum formed multicell clumps, or autoaggregates. Autoaggregation was the result of active taxis and was shown to be density-dependent, calcium-requiring, and influenced by pH. In addition, autoaggregation appeared to be species-specific, since aggregates of Ph. palmivora did not attract zoospores of three Pythium species and aggregates of Py. catenulatum did not attract Ph. palmivora zoospores. Aggregation centers generated a calcium ion gradient and induced chemotropic growth of germ tubes emerging from zoospore cysts. Autoaggregation also functions to enhance zoospore accumulation at plant root surfaces, thereby increasing inoculum potential for infection. In the absence of roots, autoaggregation may enhance zoospore population survival.

Navarro, E., Sandmann, G., and Torres-Martı́nez, S. 1995. Mutants of the carotenoid biosynthetic pathway of Mucor circinelloides. Experimental Mycology 19, 186-190. We have isolated and characterized a number of mutants affected in the biosynthesis of β-carotene in the fungus Mucor circinelloides. Mutants were obtained after mutagenesis with N -methyl-N-nitro-N-nitrosoguanidine or ultraviolet radiation. Carotene analysis and determination of in vitro activity for synthesis of prenyl pyrophosphates confirm that we have obtained mutants for all enzymatic steps from farnesyl pyrophosphate to β-carotene and regulatory mutants affecting total production of carotenes and light regulation.

Chen, W., Shearer, C. A., and Klopp, J. 1995. Phylogenetic ordinal placement based on rDNA sequences of the freshwater genera Ophioceras and Pseudohalonectria. Experimental Mycology 19, 191-201, The ordinal placement of two closely related freshwater genera, Ophioceras and Pseudohalonectria , was assessed by using phylogenetic analysis of morphological characters, partial sequences of the large subunit ribosomal DNA and restriction site variations in the internal transcribed spacer (ITS). The two genera have some morphological features that are used to define taxa in both the Sordariales and Diaporthales, and, hence, their phylogenetic relationships are unclear. Equally weighted analyses of thirty-eight morphological characters produced unresolved phylogenetic trees and unequivocal conclusions could not be drawn based on the morphological data. The polymcrase chain reaction-amplified ITS region was variable in length between the two genera and restriction sites in the ITS region were determined. Analysis of variation in restriction sites in the ITS region placed Ophioceras and Pseudohalonectria in one clade with taxa sampled from Sordariales. About 350 basepairs of DNA sequence from the 5′ end of the large subunit rDNA were also determined. In phylogenetic analysis of the sequence data with Hypocrea lutea and Nectria cinnabarina as outgroups, Ophioceras and Pseudohalonectria showed a closer relationship to Neurospora crassa , Schizothecium sp., and Sordaria fimicola of the Sordariales than to Cryphonectria parasitica and Endothia gyrosa of the Diaporthales.

Appel, D. J., and Gordon, T. R. 1995. Intraspecific variation within populations of Fusarium oxysporum based on RFLP analysis of the intergenic spacer region of the rDNA. Experimental Mycology 19, 120-128. Fifty-six isolates of Fusarium oxysporum, including F. oxysporum f. sp. melonis and nonpathogenic strains, were chosen from a larger collection to represent diversity in vegetative compatibility groups (VCGs), mitochondrial DNA (mtDNA) haplotype, geographic distribution, and virulence. Using PCR, a 2.6-kb fragment including the intergenic spacer (IGS) region of the ribosomal DNA was amplified from each isolate. The enzymes EcoRI, Sau 3A, Cfo1, and Ava1I, cut this fragment differentially, revealing 5, 6, 6, and 7 patterns, respectively. Among the 56 isolates, a total of 13 unique IGS haplotypes was identified. Among most F. o. melonis isolates. IGS haplotype correlated with VCG and mtDNA haplotype, but did not differentiate among races. However, a race 1 isolate found in VCG 0131 shared virulence, mtDNA, and IGS haplotypes characteristic of VCG 0134; this isolate may represent a conversion in VCG from 0134 to 0131. Four nonpathogens shared the pathogen vegetative compatibility phenotypes. One race 1,2 isolate associated with VCG 0134 shared both IGS haplotype and VCG with a nonpathogen, but these isolates did not share the same mtDNA haplotype. Another nonpathogenic isolate shared mtDNA and IGS haplotypes with pathogen group 0131 and may simply be an avirulent mutant of a pathogenic strain. For the other two nonpathogenic isolates, vegetative compatibility indicated a close relationship to the pathogen, but differences in both mtDNA and IGS haplotype suggest otherwise. Overall, the IGS haplotype was more variable among the nonpathogenic F. oxysporum VCGs among which 12 of the 13 IGS haplotypes were found. Nonpathogenic isolates that shared a common mtDNA haplotype, but were associated with different VCGs, often had different IGS haplotypes.

Bachem, U., and Mendgen, K. 1995. ER subcompartments in a plant parasitic fungus and in baker's yeast: Differential distribution of lumenal proteins. Experimental Mycology 19, 137-152. His-Asp-Glu-Leu (HDEL)-bearing proteins were quantified in different endoplasmic reticulum (ER) subcompartments of Saccharomyces cerevisiae and the plant parasite Uromyces viciae-fabae by immuno-electron microscopy (immuno-EM). In both fungi, the immunogold labeling of these proteins within the ER was three times greater than within the nuclear envelope. In U. viciae-fabae, the ER in germinating uredospores differed from the ER in fungal structures produced within the plant, e.g., haustoria. In haustoria, the cisternal ER differentiated large tubular-vesicular complexes (TVC). TVC contained higher levels of HDEL-bearing proteins than ordinary ER cisternae. ELISA readings also indicated an increased concentration of these proteins in isolated haustoria compared to germinating uredospores. In S. cerevisiae, the ER was differentiated into cortical and internal regions. Immuno-EM revealed that labeling of the binding protein (BiP) was lower in the ER of the cell cortex. Heat shock increased BiP signals, but the relative distribution within the ER did not change. Our results suggest that ER subcompartments can be differentiated by immunogold labeling of proteins with a retention signal. In special cases, such as in the parasitic phase of rust fungi, these proteins accumulate to higher levels in ER subcompartments, probably as a response to plant-induced stress.

Schaap, P. J., de Groot, P. W. J., Müller, Y., van Griensven, L. J. L. D., and Visser, J. 1995. Molecular cloning and sequence of the cytoplasmic ribosomal protein S15a gene from Agaricus bisporus. Experimental Mycology 19, 160-162. We have isolated an Agaricus bisporus cDNA which encodes an open reading frame of 130 amino acids. A comparison with the Genbank database shows that the deduced amino acid sequence of this open reading frame is highly homologous to the small subunit ribosomal proteins S15a of Brassica napus and Drosophila melanogaster and to the small subunit ribosomal proteins S24 of Strongylocentrotus purpuratus and Saccharomyces cerevisiae .

Pireaux, J-C., Hayani-Obeidou, W., Chalot, M., Botton, B., and Dizengremel, P. 1995. Mitochondria in the white-rot fungus Phanerochaete chrysosporium: Purification and evidence for a mitochondrial isoform of aspartate aminotransferase. Experimental Mycology 19: 91-100. A very high specific aspartate aminotransferase activity was found in young Phanerochaete chrysosporium cultures. In order to obtain more information about the localization of aspartate aminotransferase, mitochondria were isolated and purified. The purification gradient showed two mitochondrial fractions. Mitochondria localized near the top of the gradient were severely damaged, whereas mitochondria aggregated at the bottom part were largely intact (91 and 94% intactness for outer and inner membrane, respectively). The highest oxidation rates were obtained with succinate and NADH as substrates. Malate oxidation was improved by exogenous NAD⁺ while NADPH oxidation was partially Ca²⁺ dependent. All these oxidations were correctly coupled to the phosphorylation. Experiments using standard respiratory chain inhibitors indicate that, in P. chrysosporium mitochondria, the alternative pathway was present, but not engaged. On nondenaturing uniform polyacrylamide gels, four aspartate aminotransferase isoforms were detected, one being localized in the mitochondrial matrix. On nondenaturing polyacrylamide gradient gels, the nonmitochondrial isoforms had similar electrophoretic mobilities with a molecular mass estimated at 110 kDa, while the mitochondrial isoform had a molecular mass of about 160 kDa.

Bartnicki-Garcia, S. Bartnicki, D. D., Gierz, G., López-Franco, R., and Bracker, C. E. 1995. Evidence that Spitzenkörper behavior determines the shape of a fungal hypha; A test of the hyphoid model. Experimental Mycology 19, 153-159. Hyphae of the fungus Rhizoctonia solani have a characteristic Spitzenkörper in their growing tips and a cell shape described by the mathematical hyphoid equation. A mild disturbance of hyphae growing in a slide culture chamber on a microscope stage caused the Spitzenkörper to move away from its usual position next to the apical pole and wander briefly inside the apical dome. Hyphal elongation rate declined abruptly, and the apex became rounded and increased in diameter. As the Spitzenkörper migrated back to its polar position, rapid cell elongation resumed, and the contour of the growing hyphal tip returned to the typical hyphoid shape. The brief dislocation of the Spitzenkörper left a permanent bulge in the hyphal profile. This morphogenetic sequence was mimicked by computer simulation, based on the hyphoid equation which relates the generation of hyphal shape to the linear displacement of a vesicle supply center (VSC). The VSC was programmed to retrace the observed movements of the Spitzenkörper during the above sequence. The resulting similarity of shape between real and computer-simulated cells reinforces the mathematical prediction that the Spitzenkörper acts as a VSC and that its continuous linear advancement generates a typical hyphal tube with the characteristic hyphoid shape. Accordingly, the hyphoid model and its VSC concept provide a plausible hypothesis to explain the cellular basis of polarized growth of fungal hyphae.

Staben, C. 1995. Resistance to azole drugs in Neurospora crassa. Experimental Mycology 19: 163-165. Neurospora crassa was susceptible to azole drugs: ketoconazole (MIC 1 μg/ml), fluconazole (MIC 5 μg/ml), and SCH39304 (MIC 5 μg/ml). Mutants of N. crassa resistant to ketoconazole were selected and genetically characterized. The seven characterized resistance mutations represented at least four genetic loci. Some mutants, but not all, were also resistant to fluconazole and to SCH39304.

Ghazali, M., Rodier, M.-H., el Moudni, B., Quellard, N., Jacquemin, J.-L. 1995. Detection of myosin immunoanalogue in the yeast Candida albicans. Experimental Mycology 19: 101-110. Detection and localization of myosin immunoanalogue protein in the yeast Candida albicans were achieved by immunoblotting, indirect immunofluorescence assay, and immunoelectron microscopy. A polypeptide with an M_r about 110,000, from cytosolic extract and insoluble fraction in the corresponding membrane pellet, was reacted with polyclonal and monoclonal antibodies raised against vertebrate muscle myosin. This protein was located by immunofluorescence and immunoelectron microscopy in the cell cortex along the plasmalemma, in the cytoplasm, and in the septum corresponding to bud scar region situated between the yeast-mother cell and the bud.