Experimental Mycology最新文献

Redkar, R. J., Locy. R. D., and Singh, N. K. 1995. Biosynthetic pathways of glycerol accumulation under salt stress in Aspergillus nidulans. Experimental Mycology 19, 241-246. A culture of Aspergillus nidulans (FGSC 359) was gradually adapted for growth in media containing up to 2 M NaCl or was exposed to a salt shock with 2 M NaCl. The intracellular glycerol level increased by about 7.9-fold in salt-adapted and 2.4-fold in salt-shocked cultures when compared to the unadapted culture. The biosynthetic pathway involved in the accumulation of glycerol was investigated under long-term salt adaptation and short-term salt shock. Glycerol 3-phosphate dehydrogenase (EC 1.1.1.8) was induced 1.4-fold in salt-shocked but not in salt-adapted cultures. An alternate enzymatic pathway involving glycerol dehydrogenase (NADP⁺-dependent) utilizing dihydroxyacetone (DHA) and/or DL-glyceraldehyde (DL-GAD) was induced by NaCl. DHA-dependent glycerol dehydrogenase activity was induced about 6.3-fold in salt adapted and 1.35-fold in salt-shocked cultures, while DL-GAD-dependent activity was induced about 6.1-fold in salt-adapted and 1.2-fold in salt shocked cultures. However, the level of glycerol dehydrogenase activity with DL-GAD as substrate was 7% of the DHA-dependent activity. We conclude that a salt-inducible NADP⁺-dependent glycerol dehydrogenase activity electrophoretically indistinguishable from previously described glycerol dehydrogenase I results in glycerol accumulation in salt-stressed A. nidulans.

Kempken, F., Schreiner, C., Schörgendorfer, K., and Kück, U. 1995. A unique repeated DNA sequence in the cyclosporin-producing strain of Tolypocladium inflatum (ATCC 34921). Experimental Mycology 19, 305-313. Recombinant λ clones containing repeated DNA sequences were isolated from the cyclosporin A-producing fungus Tolypocladium inflatum (ATCC 34921) by differential hybridization with total fungal DNA and rDNA probes. From this survey 1% of the λ clones appeared to contain repeated sequences. Subsequent analysis led to the identification of a dispersed repetitive DNA element. It was named CPA element (cyclosporin production associated) and appears to be strain specific, since it is absent from other related strains or fungi. Hybridization with chromosomal restriction fragments indicates an equal distribution of the CPA element in the genome. The copy number was estimated to be between 20 and 30 per haploid genome. Sequence analysis of a 0.9-kb XhoI fragment from three copies of the CPA element revealed strong conservation of this sequence among all copies. A 200-bp region exhibits similarities to a repeated sequence from Zea diploperennis. The use of this DNA sequence as a molecular marker for identification of this cyclosporin-producing strain ATCC 34921 is discussed as is the relevance of repeated DNA sequences for rearrangements of fungal karyotypes.

Fernández, Murray, P., and Passeron, S. 1995. The soluble aminopeptidase system from Saccobolus platensis. Characterization of a new glutamate aminopeptidase. Experimental Mycology 19, 214-222. The aminopeptidase pattern from the fungus Saccobolus platensis was investigated by ion-exchange chromatography fractionation of the soluble proteins. The chromogenic p-nitroanilide derivatives of nine different amino acids were used as substrates. Apart from the previously characterized major alanine aminopeptidase (P. Fernádez Murray, A. Samela, and S. Passeron, 1992. Exp. Mycol. 16, 279-290), two new minor aminopeptidase activities were found: one mainly a proline aminopeptidase and a second highly specific for the hydrolysis of the chromogenic derivative of glutamate. This last activity was subjected to ammonium sulfate fractionation and successive phenyl-Sepharose, DEAE-Sephacel, and Sephacryl S-200 HR column chromatography. A highly purified enzyme fraction was obtained. This new glutamate aminopeptidase had a molecular weight of 22 kDa and an optimum pH range of 7.2-8.0 and was inhibited by o-phenanthroline and bestatin.

Délye, C., Corio-Costet, M.-F., and Laigret, F. 1995. A RAPD assay for strain typing of the biotrophic grape powdery mildew fungus Uncinula necator using DNA extracted from the mycelium. Experimental Mycology 19, 234-237. We describe, for the first time, a RAPD assay using DNA extracted from the mycelium of a powdery mildew fungus, Uncinula necator, a pathogen of grape. No contamination by plant DNA was observed, and the resulting patterns were fully repetitive. RAPD profiles were unchanged when using two different DNA polymerases or three different thermocyclers. Thirteen strains were tested for amplification, using 95 primers. Only 4% of the amplified fragments were polymorphic. Cluster analysis revealed that the strains from the same geographical origin had the higher genetic similarity, suggesting a short-range dissemination of U. necator. This RAPD assay was also successfully applied to the grape downy mildew fungus, Plasmopara viticola, indicating that it can be used for other fungi which cannot be grown on artificial media.

Xia, J. Q. and Correll, J. C. 1995. Examination of mitotic stability and hybridization potential between two genetically distinct haplotypes of Magnaporthe grisea. Experimental Mycology 19, 171-177. MGR586 DNA fingerprinting was used to examine the mitotic stability and hybridization potential of two genetically distinct haplotypes of Magnaporthe grisea under laboratory conditions. Two isolates representing a haplotype in each of two different MGR586 DNA-fingerprinting groups (A and D) commonly found on rice in Arkansas, were grown singly or in coculture on solid medium, liquid medium, or on coinoculated rice leaves. A total of 355 monoconidial cultures were recovered at various times and examined for their MGR586 DNA fingerprints. The majority of the isolates of the two MGR586 DNA haplotypes remained stable over the 162-to 171-day study period. However, 16 isolates recovered belonged to one of seven nonparental haplotypes identified; the DNA fingerprints of these haplotypes differed by only 1-5% from the parental haplotypes. Of 97 isolates recovered from solid medium, a single nonparental haplotype was identified from the coculture treatment after 171 days. Of the 200 isolates recovered from liquid medium, 15 were nonparental types and represented seven different haplotypes. Of these, a single nonparental isolate was recovered from the parental haplotype D isolate grown singly after 67 days. The other 14 nonparental isolates were recovered from the coculture treatment; 3 were recovered after 38 days, 4 after 67 days, and 7 after 162 days. Thus, the nonparental variants were recovered much more frequently from the cocultured treatment. The appearance of the nonparental haplotypes may be due to hybridization between the two haplotypes. However, other factors such as a higher mutation in coculture cannot be ruled out as a possible explanation for these data. All isolates recovered from a lesion from coinoculated rice leaves were one haplotype. The data indicate that there was competition in both artificial media and host tissue between the two MGR586 haplotypes.

Bunyard, B. A., Nicholson, M. S. and Royse, D. J. 1995. Phylogenetic resolution of Morchella, Verpa, and Disciotis [Pezizales: Morchellaceae] based on restriction enzyme analysis of the 28S ribosomal RNA gene. Experimental Mycology 19, 223-233. The large subunit (28S) of the ribosomal DNA repeat of Morchella, Verpa, and Disciotis and a closely related genus (Gyromitra) was enzymatically amplified via the polymerase chain reaction. Restriction fragment length polymorphisms were found among the lines investigated and used to infer phylogenetic relationships. More variability was observed toward the 5′ end than toward the 3′ end of the 28S rRNA gene. The RFLP data were used to assemble a phylogenetic tree for the taxonomic group. Based on the RFLP data three black Morchella species isolates differed by approximately 0.5, 1.0, and 1.5%, respectively, from all other isolates in the Morchellaceae examined in this study. Gyromitra gigas , used as an outgroup, had approximately 6.2% difference from all members of the Morchellaceae. In some cases more genetic variation was observed intraspecifically than between putative species. Additionally, the hypothesis that Morchella is composed of only a few (possibly three) polymorphic species was supported by our findings.

Molloy, C., Shepherd, M. G., and Sullivan, P. A. 1995. Differential extraction of N-acetylglucosaminidase and trehalase from the cell envelope of Candida albicans. Experimental Mycology 19, 178-185. Dithiothreitol (DTT) extraction of N-acetylglucosaminidase and trehalase from intact Candida albicans ATCC 10261 cells was monitored as an index of cell envelope porosity during N-acetylglucosamine-induced morphogenesis. Trehalase, which is secreted into the cell envelope during starvation and bud-formation, displayed similar extraction kinetics in starved, germ tube-forming, and bud-forming cells, indicating that the mother cell wall remains largely unchanged during morphogenic outgrowth and that the porosity of bud and mother cell walls is similar. N-acetylglucosaminidase, which is secreted specifically during morphogenesis, was released eightfold more rapidly from germ tube-forming than bud-forming cells, reflecting major differences in porosity between bud and germ tube. In addition, by assaying DTT extracts and extracted cell residues, it was found that the total extracellular N -acetylglucosaminidase activity increased 2- to 2.5-fold during DTT treatment. Thus, DTT unmasks a cryptic form of N-acetylglucosaminidase. The cryptic activity was associated with the cell wall fraction.