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At least 19 recordsLinked to original sources
PubMed1992

L-696,474, a novel cytochalasin as an inhibitor of HIV-1 protease. I. The producing organism and its fermentation.

A novel cytochalasin, L-696,474, (18-dehydroxy cytochalasin H) that inhibits HIV-1 protease was discovered in fermentations of a bark-inhabiting Ascomycete, Hypoxylon fragiforme. The product was first identified from extracts of an agar medium. Fermentation studies on a number of media indicated that the product can be made on several solid and liquid media. Optimum production was obtained from growth in a complex medium composed of glycerol, glucose, citrate, Ardamine, soybean meal, tomato paste, and inorganic salts. Other Hypoxylon spp., related species of Xylariales, and other fungi known to produce cytochalasins, were also surveyed for their ability to make L-696,474. Only one other Hypoxylon fragiforme isolate was found to make this novel cytochalasin; none of the other cultures surveyed made L-696,474 or any other compounds which inhibit HIV-1 protease.

Ascomycota↗
PubMed1990

Self-splicing of the mobile group II intron of the filamentous fungus Podospora anserina (COI I1) in vitro.

The first intron of the mitochondrial gene coding for cytochrome oxidase subunit I (COI I1) of Podospora anserina can undergo self-splicing in vitro at high concentrations of NH4Cl or KCl. Under these conditions cleavage at the 5' splice junction takes place without branch formation probably via hydrolysis by water or OH- and the intron is released in a linear form. In vitro transcripts that contain mutated introns with large deletions in nonconserved domain IV comprising greater than 50% of the intronic sequence display a more efficient splicing reaction and, surprisingly, 5' cleavage via transesterification and lariat formation is re-established to a low degree under NH4Cl. In contrast to the self-splicing group II introns aI5 gamma and bI1 from yeast mitochondria cleavage at the 3' splice site of the Podospora intron is reduced and cleavage by hydrolysis in trans (i.e. exon reopening) is almost completely suppressed. Both observations could be interpreted as a result of unfavourable spatial conformations of the intron that (i) lead to a steric hindrance of the 5' exon to attack the 3' splice site in cis and (ii) block intron-dependent cleavage reaction of the ligated exons in trans. Alternatively, the possibility that a weak overall interaction of the postulated exon- with the corresponding intron-binding sites (EBS-IBS pairings) is responsible for the remarkable differences to the self-splicing reaction of other group II introns is discussed.

Ascomycota↗
PubMed1991

Virus-like genetic organization and expression strategy for a double-stranded RNA genetic element associated with biological control of chestnut blight.

The complete nucleotide sequence of the largest double-stranded (ds) RNA present in hypovirulent strain EP713 of the chestnut blight pathogen, Cryphonectria parasitica, was determined and the predicted genetic organization was confirmed by translational mapping analysis. The deduced RNA sequence was 12 712 bp in length, excluding the terminal poly(A):poly(U) homopolymer domain. The strand terminating with 3'-poly(A) contained two contiguous large open reading frames (ORF A and ORF B) beginning at nucleotide residues 496-498 and extending to nucleotide positions 11 859-11 861. The junction between ORF A and ORF B consisted of the sequence 5'-UAAUG-3', where UAA served as the termination codon for ORF A and AUG was the 5'-proximal initiation codon within ORF B. ORF A (622 codons in length, excluding the termination codon) was recently shown to encode two polypeptides, p29 and p40, which were generated from a nascent polyprotein by an autocatalytic event mediated by p29 (Choi et al., 1991). A similar autocatalytic event was observed during in vitro translation of ORF B (3165 codons in length) resulting in the release of a 48 kd polypeptide from the amino-terminal portion of the ORF B-encoded polyprotein. These results are discussed in terms of the opportunities they provide for elucidating the molecular basis of transmissible hypovirulence and possible origins of hypovirulence-associated dsRNAs.

Amino Acid Sequence↗
PubMed1991

The contribution of defective RNAs to the complexity of viral-encoded double-stranded RNA populations present in hypovirulent strains of the chestnut blight fungus Cryphonectria parasitica.

Hypovirulent strain EP713 of the chestnut blight fungus Cryphonectria (Endothia) parasitica harbors a family of viral encoded double-stranded (ds) RNAs thought to be responsible for the hypovirulence phenotype. These include L-dsRNA, described in the accompanying paper (Shapira et al., 1991); several prominent species in the estimated size range of 8 to 10 kb, referred to here as M-dsRNAs; and several smaller species designated S-dsRNAs which range in size from approximately 0.6 to 1.7 kb. The characterization of the M- and S-dsRNA species is the subject of this report. Results from polymerase chain reaction mapping and molecular hybridization analysis indicate that the M- and S-dsRNA species are internally deleted forms of L-dsRNA. Three different S-dsRNA species were cloned and sequenced. Each species contained a single deletion breakpoint and retained either 149, 155 or 156 bp of the terminus corresponding to the 5'-end of the coding strand and 440, 447 or 449 bp of the other terminus. Two of the S-dsRNA species contained, within the boundaries of the breakpoint, additional sequence information consisting of 42 bp or 95 bp that appeared to be unrelated to the L-dsRNA sequence. These results demonstrate that defective RNAs contribute significantly to the complexity of dsRNA populations found in hypovirulent strains of C. parasitica and provide a first approximation of the location of cis-acting signals involved in their replication.

Base Sequence↗
PubMed1992

A viral gene confers hypovirulence-associated traits to the chestnut blight fungus.

A viral double-stranded (ds)RNA associated with reduced virulence (hypovirulence) and the accompanying biological control of the chestnut blight fungus, Cryphonectria parasitica, was shown recently to contain two contiguous coding domains designated ORF A and ORF B. We report here that transformation of an isogenic virulent, dsRNA-free C. parasitica strain with a cDNA copy of ORF A conferred traits similar to those exhibited by the dsRNA-containing hypovirulent strain: characteristics included reduced pigmentation, reduced laccase accumulation and suppressed conidiation. However virulence was not reduced, indicating an apparent uncoupling of associated traits from hypovirulence. These results establish a direct cause and effect relationship between a viral dsRNA genetic element present in a hypovirulent C. parasitica strain and specific phenotypic traits. They demonstrate further that these traits are not the result of a general reaction of the fungus to the presence of the replicating viral RNA, but are caused by a specific viral coding domain.

Genes, Viral↗
PubMed1977

X-ray analysis and circular dichroism of the acid protease from Endothia parasitica and chymosin.

The structure of an acid proteinase from Endothia parasitica has been solved by x-ray diffraction using multiple isomorphous replacement. A 3 A resolution map was interpreted in terms of a bilobal structure with a long 25 A cleft. The secondary structure is mostly distorted beta-sheet. The circular dichroism was measured and model curves for different secondary structures were fitted by least squares indicating a large component of beta-structure. The structure was seen to be homologous with that of the acid proteinase from R. Chinensis and hence with pepsin and chymosin. A rotation function against diffraction data from chymosin crystals confirm confirm this and suggested an approach to the solution of this structure.

Ascomycota↗
PubMed1977

The phenol oxidases of the ascomycete Podospora anserina. XII. Affinity of laccases II and III to substrates with different substitution patterns.

For the low molecular weight laccases II and III of Podospora anserina the kinetic parameters Michaelis constant (KM) and maximum reaction velocity (V) were determined polarographically under pH optimum conditions for representative substrates of different substitution patterns. Laccase II showed two peaks in its pH optimum curve, each with a different substrate specificity, indicating structural differences to laccase III which exhibits only one broad peak. Under optimum conditions the affinities of various substrates are determined by their substitution patterns: high affinity for simple o- and p-diphenols, low affinity for m-henols. The maximal velocity remains largely uninfluenced. This study of the effect of substitution on substrate utilization leads to the assumption that there is no specific reactive site for m-phenols in either laccase. Oxidation of m-phenols, however, takes only place at high pH values.

Ascomycota↗
PubMed1976

Microbial degradation of the thiolcarbamate herbicide, diallate, in soils and by pure cultures of soil microorganisms.

The disappearance of the herbicide, Avadex (40% diallate), from five agricultural soils (differing in either pH, carbon content, or nitrogen content), incubated under sterile and non-sterile conditions, was followed for a period of 20 weeks. Avadex was rapidly lost from microbiologically active soils, with over 50% of the applied (2.5 ppm) dosage disappearing within four weeks; losses from sterile soils were much slower with recoveries of over 50% after 20 weeks. Incubation of soil with Avadex to which 14C-labeled diallate had been added resulted in rapid formation of 14CO2 from microbiologically active samples and only very slow 14CO2 formation from sterile samples. Substantial quantities of radioactivity were retained as unextractable residues in both sterile and non-sterile soils after senven days incubation. From these data it was concluded that the disappearance of the herbicide from non-sterile soils was mainly due to microbial degradation and to binding of diallate or its metabolites as residues to undefined soil components. Losses from sterile soils were attributed to both binding of residues and to a slow chemical degradation. Avadex degradation by pure cultures was studied using representative fungi isolated from the five soils. Of the fungi tested, Phoma eupyrena, Penicillium janthinellum, and Trichoderma harzianium coudl degrade at least 20% of the applied (2.5 ppm) herbicide after ten days incubation. Degradation of Avadex in soil cultures of T. harzianum was found to be slower than degradation in liquid nutrient cultures.

Biodegradation, Environmental↗
PubMed1979

Microorganisms in the rhizosphere of wheat colonized by the fungus Gaeumannomyces graminis var. tritici.

The population of microorganisms in wheat rhizosphere changed in the presence of the fungus Gaeumannomyces graminis var. tritici causing the take-all of wheat. In the majority of cases when the soil was artificially contaminated by the fungus, both the number of bacteria in the rhizosphere and the bacteria/fungi ratio temporarily increased. At the beginning bacteria growing in the presence of NH4+ predominated, later bacteria utilizing organic N-substances prevailed. Pseudomonas fluorescens and the related species colonized the rhizosphere and the soil to a greater extent in the presence of G. graminis. The wheat rhizosphere with G. graminis was found to contain a higher level of the slime-producing bacterium Agrobacterium spp.; this microorganism occurred on hyphal surfaces (in hyphosphere) of both G. graminis growing in soil and Mucor spp. Changes in microbial populations in the wheat rhizosphere during the first stage of colonization by G. graminis can be partly explained by a simultaneous rhizosphere colonization by microorganisms which accompany this fungus in soil. In the period of increase in the number of bacteria in rhizosphere a temporary stimulation of wheat growth was observed.

Actinomycetales↗
PubMed1979

Effect of bacterial polysaccharides on the growth of Gaeumannomyces graminis var. tritici and wheat roots.

Agrobacterium sp. and related species which in the soil and in the rhizosphere of wheat accompany the fungus Gaemannomyces graminis var. tritici and cause take-all of the wheat roots produced polysaccharides in pure cultures (glucans, mannoglucans and galactomannoglucans). These polysaccharides were utilized better by the mycelium of G. graminis than glucose and polysaccharides of plant origin that occurred on the surface of wheat roots (the so-called mucigel). At lower concentrations these bacterial polysaccharides stimulated growth of wheat roots, higher concentrations (more than 0.1%) were inhibitory. Bacteria inoculated on the surface of wheat first inhibited and then stimulated the development of the plants and their growth. Changes in the growth rate of wheat, the rhizosphere of which was colonized by bacteria simultaneously with the fungus G. graminis and also some changes in the course of the disease of wheat roots caused by the fungus can be explained by the inhibitory or stimulatory effect of polysaccharides of accompanying bacteria.

Ascomycota↗
PubMed1979

Four-fold structural repeat in the acid proteases.

The observation that the acid proteases contain two structurally equivalent lobes related by a dyad through the active centre has been extended to show that in endothiapepsin each lobe contains two similar halves related by a further local dyad. In lobe 1 22 pairs of alpha-carbons are equivalent with a root mean square deviation of 1.92 A. In lobe 2 17 pairs match within 2.31 A. Convergent evolution or gene quadruplication may have occurred.

Amino Acid Sequence↗