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At least 271 records · Page 15Linked to original sources
PubMed1998

The ipiO gene of Phytophthora infestans is highly expressed in invading hyphae during infection.

The expression of the in planta-induced gene ipiO of the potato late blight pathogen Phytophthora infestans was analyzed during various developmental stages of its life cycle. ipiO mRNA was detected in zoospores, cysts, germinating cysts, and young mycelia, but not in sporangia or in old mycelia grown in vitro. ipiO is not only expressed in stages prior to infection but also during colonization of potato and tomato leaves. In disease lesions, ipiO mRNA was detected in the water-soaked area and the healthy-looking plant tissue surrounding it. In contrast, ipiO mRNA was not found in necrotized tissue or in sporulating areas of a lesion. To determine more precisely the location and time of ipiO gene expression in planta, cytological assays were performed using a P. infestans transformant expressing a transcriptional fusion between the ipiO1 promoter and the beta-glucuronidase (GUS) reporter gene. GUS staining was found specifically in the subapical and vacuolated area of tips of invading hyphae. The histochemical GUS assays demonstrate that ipiO is expressed during biotrophic stages of the disease cycle.

Blotting, Northern↗
PubMedDate not supplied

In pursuit of the whole hypha.

We know organisms first of all by their forms. Rabbit and carrot, Neurospora, and Paramecium represent particular shapes and structures, patterns in space and time. Each pattern integrates innumerable molecules into a coherent whole, reproduces itself from one generation to the next, and may persist in this manner for millions of years. In this lecture, I shall discuss efforts to render a dynamic and causal account of biological morphogenesis, using fungal hyphae as a concrete exemplar. Molecular structures and interactions are necessary but not sufficient to specify patterns on a scale three to five orders of magnitude larger. The search for alternatives leads to the importation of the concept of dynamic fields, exemplified by the proposal of Bartnicki-Garcia and Gierz that apical growth and morphogenesis report the operation of a mobile vesicle-supply center. Application of field theories to biological morphogenesis is still at an early stage, but is necessary in order to resolve the paradoxical relationship between genes and form.

Cell Wall↗
PubMed2000

Septum position is marked at the tip of Aspergillus nidulans hyphae.

Aspergillus nidulans hyphae have long tip cells that are separated from short basal cells by septa. Basal cells average 40 microm long with three or four nuclei. Septation follows parasynchronous mitoses in the tip cell and seems to occur at premarked sites, but how these sites are established is unclear. A. nidulans strains with the hypA1 mutation are wildtype at 28 degrees C but if shifted to 42 degrees C, their tip cells insert septa with a wildtype spacing, apparently triggered by an aberrant mitosis. Tip cell septa are trilamellar, like wildtype, but lack a central pore. Like wildtype, tip cell septation requires a minimum cell size and is inhibited by actin and microtubule poisons. In a hypA1 background, tip cell septation is blocked by nim (never in mitosis) mutants, but not by bim (blocked in mitosis) mutants. Future septation sites appear to be established during tip growth, before their activation in basal regions.

Aspergillus nidulans↗
PubMed1993

Automatic evaluation of antifungal volatile compounds on the basis of the dynamic growth process of a single hypha.

An automatic analysing system was developed and employed for the evaluation of antifungal activity of volatile compounds in the gas phase. Aspergillus niger was inoculated on agar medium in the reaction vessel. The reaction vessel was incubated at 28 degrees C for 24 h and then a volatile compound was introduced into the vessel either in a batch or flow manner. The antifungal activity of the respective compounds estimated in situ was expressed by the dynamic response parameters of a single hypha. All volatiles tested in the present system inhibited hyphal growth, except linalyl acetate: Limone and geraniol were the most inhibitory. In contrast, linalyl acetate promoted hyphal growth. By definition of the parameters, the fungicidal and fungistatic effects could be distinguished.

Antifungal Agents↗
PubMed1980

Small forms and hyphae of paracoccidioides brasiliensis in human tissue.

A 53 year-old man had a three-year recurrent respiratory infection. No fungi was detected in sputum examinations. Immunodiffusion test with paracoccidiodin revealed two precipitin bands. Very small forms and hyphae of a fungus were seen on silver methenamine stained serial sections from lung's lesion. P. brasiliensis was identified on the basis of the rare multibudding small forms.

Fungi↗
PubMed1977

Antifungal antibiotic of the Basidiomycete Oudemansiella mucida. III. Nuclei in the hyphae of mono- and dikaryons.

Nuclear ratios were studied in terminal and subterminal cells of various mycelia of the basidiomycete Oudemansiella mucida, the producer of the antifungal antibiotic mucidin (MuciderminR Spofa). The dikaryon, the monokaryon, and the mucidin-producing strain that had been cultivated for a long time under submerged conditions were compared. Dedikaryotization was found to have taken place in the producing strain. The originally dikaryotic culture with characteristic clamp connections on the mycelium and with two nuclei in every hyphal cell lost permanently the clamp connections, probably owing to continuous intense agitation. The hyphae contained solely mononuclear cells. Mating with a compatible monokaryon yielded a dikaryon capable of normal fructification.

Antifungal Agents↗
PubMed1999

Comparison of chitin content in the apical and distal parts of fungal hyphae in Basidiobolus ranarum, Neurospora crassa and Coprinus sterquilinus.

Primary cell wall is synthesized in the growth zone of hyphal apex in fungi and rigidified during maturation along the newly formed hypha. Cross-linking of cell-wall components and self-assembly of individual polysaccharide chains into microfibrils are supposed to be involved in the rigidification process. We determined the relative chitin content in the cell wall of hyphal tips and distal walls of three fungal species and demonstrated a general increase in relative chitin content in mature cell walls. Thus, this increase can be supposed to raise cell-wall rigidity as the principal role of chitin in the determination of cell-wall rigidity is beyond doubt.

Cell Wall↗
PubMed1993

A quantitative radiometric assay to measure mammalian cell binding to hyphae of Candida albicans.

A rapid and reproducible assay has been developed to measure the capacity of lymphocytes to bind to Candida albicans. Lymphocytes that bound to C. albicans were either the large granular lymphocyte cell line, YT, or interleukin-2 activated lymphocytes. Lymphocyte binding was assessed as the associated radioactivity of 51Cr-labeled lymphocytes with preformed hyphae. The assay was sensitive to detection of 0.6 lymphocytes/one hyphal form at one half maximal lymphocyte binding capacity. The assay correlated well with direct microscopic assessment of lymphocyte binding to C. albicans and provided quantitative radiometric data. Although the assay was developed for the assessment of lymphocyte adhesion to C. albicans, it can be used to measure binding of other mammalian cells (e.g., polymorphonuclear leukocytes) to this fungus. In addition, the assay may be used to identify molecules involved in the adhesion of lymphocytes and other mammalian cells to C. albicans.

Animals↗
PubMed1992

The carboxypeptidase Y-encoding gene from Candida albicans and its transcription during yeast-to-hyphae conversion.

We have cloned and sequenced the gene (CPY1) encoding the carboxypeptidase Y (CPY) of Candida albicans. The gene contains an open reading frame comprising 542 amino acids (aa) with an M(r) of 61,104. The aa sequence shows 74% identity to the mature CPY aa sequence from Saccharomyces cerevisiae. The putative pre (signal) and pro sequences at the N terminus of the C. albicans protein, however, show significant divergence from the corresponding prepro sequence of the S. cerevisiae protein. Southern analysis of C. albicans genomic DNA suggested the presence of only one CPY-encoding gene. Northern analysis during yeast-to-hyphae conversion suggested that the CPY1 gene is transiently down-regulated on a transcriptional level during the early events of this developmental switch.

Amino Acid Sequence↗
PubMedDate not supplied

Existence of ornamentations on macroconidia and hyphae of Epidermophyton floccosum.

The surface features of cell walls of several recent clinical isolates of Epidermophyton floccosum were examined by scanning electron microscopy. Macroconidia from each of our isolates displayed excrescences on the wall which were similar in their location and in their substructural appearance. We believe these irregularities sufficiently developed to regard them as true wall ornamentations. Comparisons were made with wall features of the macroconidia of Microsporum persicolor. In some cases, our Epidermophyton isolates possessed warty as well as secondary smooth spiral hyphae. The demonstration of these structures in recent isolates might imply that some sexual activity persists so that discovery of a teleomorph(s) for the genus Epidermophyton may yet be forthcoming.

Cell Wall↗
PubMed1999

Histochemical and ultrastructural characterization of vacuoles and spherosomes as components of the lytic system in hyphae of the fungus Botrytis cinerea.

An integrated approach to acid phosphatase (EC 3.1.3.2) histochemistry by the azo-dye and lead-capture ('Gomori') methods in phosphate-starved hyphae of the fungus Botrytis cinerea revealed strikingly different patterns of localization of activity staining. Reaction product formed with the azo-dye method was found in numerous small organelles (<0.5 microm diameter), which also accumulated the lipophilic dye Nile Red and mislocalized the formazan indicating mitochondrial succinate dehydrogenase activity. Such small organelles were stained only weakly and sporadically with the lead-capture method; instead, lead phosphate deposits were produced mainly in large vacuoles (up to 2.5 microm diam.), similar to those accumulating the vital dye Neutral Red. Additionally, acid phosphatase activity was detected in apical secretory vesicles with the lead-capture method but not with the azo-dye method. Ultrastructural studies by transmission electron microscopy confirmed the presence of large vacuoles which showed evidence of autophagic activity, and of small moderately osmiophilic organelles. The latter are considered to be spherosomes rather than lysosomes because of their weak reaction with the lead-capture method and their high lipid content. It is suggested that their apparently strong reaction with the azo-dye method is caused partly by false localization due to the lipophilic nature of the reaction product.

Acid Phosphatase↗
PubMed1998

Increased nuclear traffic chaos in hyphae of Aspergillus nidulans: molecular characterization of apsB and in vivo observation of nuclear behaviour.

Filamentous fungi are model microorganisms for studying nuclear migration in eukaryotic cells. Two genes, apsA and apsB (=anucleate primary sterigmata), were identified in Aspergillus nidulans that affect nuclear distribution in hyphae and specifically block conidiophore development at the metula stage when mutant. Here we describe the cloning, sequencing and molecular analysis of apsB. The gene encodes a 121 kDa coiled-coil, hydrophilic protein that was localized in the cytoplasm. No protein-protein interaction was detected between ApsB and ApsA, a membrane-associated, previously identified protein. An apsB null mutant was characterized by video epifluorescence microscopy using strains that express green fluorescent protein (GFP) in nuclei. With this novel approach, we have discovered a new mutant phenotype and have found that nuclei display an increased chaotic movement in older hyphal compartments that results in clustering and an uneven distribution of these organelles. These results suggest a regulatory role of ApsB in nuclear migration.

Amino Acid Sequence↗
PubMed2002

Dynamic distribution of BIMG(PP1) in living hyphae of Aspergillus indicates a novel role in septum formation.

Mutation of bimG, the major protein phosphatase 1 gene in Aspergillus nidulans, causes multiple cell cycle and hyphal growth defects that are associated with overphosphorylation of subcellular components. We have used functional translational fusions with the green fluorescent protein (GFP) to show that BIMG has at least four discrete locations within growing hyphae. Three of these locations, the hyphal tip, the spindle pole body and the nucleus, correlate with previously known requirements for bimG(PP1) in mitosis and hyphal growth and are highly dynamic. BIMG-GFP in the hyphal tip seemed to be associated with the plasma membrane and formed a collar of fluorescence within the apical dome. The distribution of nuclear BIMG-GFP varied depending on nutritional conditions; on poor medium, it concentrated more in the nucleolus than in the nucleoplasm, whereas on rich medium, it was more evenly distributed between the two nuclear regions. The association of BIMG-GFP with developing septa was transient, and we present evidence that BIMG phosphatase plays a direct role in septum formation, distinct from its role in mitosis. We conclude that, by being physically present at several sites, the BIMG phosphatase has roles in multiple cellular processes.

Aspergillus nidulans↗
PubMed2001

Identification of a novel genetically controlled step in mycorrhizal colonization: plant resistance to infection by fungal spores but not extra-radical hyphae.

Vesicular arbuscular mycorrhizal fungi infect plants by means of both spores and vegetative hyphae at early stages of symbiosis. Using 2500 M2 fast-neutron-mutagenized seeds of the miniature tomato (Lycopersicon esculentum) cultivar, Micro-Tom, we isolated a mutant, M161, that is able to resist colonization in the presence of Glomus intraradices spores. The myc(-) phenotype of the mutant was stable for nine generations, and found to segregate as a single Mendelian recessive locus. The mutant exhibited morphological and growth-pattern characteristics similar to those of wild-type plants. Alterations of light intensity and day/night temperatures did not eliminate the myc(-) characteristic. Resistance to mycorrhizal fungal infection and colonization was also evident following inoculation with the fungi Glomus mosseae and Gigaspora margarita. Normal colonization of M161 was evident when mutant plants were grown together with arbuscular mycorrhizal-inoculated wild-type plants in the same growth medium. During evaluation of the pre-infection stages in the mutant rhizosphere, spore germination and appressoria formation of G. intraradices were lower by 45 and 70%, respectively, than the rates obtained with wild-type plants. These results reveal a novel, genetically controlled step in the arbuscular mycorrhizal colonization process, governed by at least one gene, which significantly reduces key steps in pre-mycorrhizal infection stages.

Fungi↗
PubMed2003

Relating foliar dehydration tolerance of mycorrhizal Phaseolus vulgaris to soil and root colonization by hyphae.

Mycorrhizal symbiosis can modify plant response to drying soil, but little is known about the relative contribution of soil vs. root hyphal colonization to drought resistance of mycorrhizal plants. Foliar dehydration tolerance, characterized as leaf and soil water potential at the end of a lethal drying episode, was measured in bean plants (Phaseolus vulgaris) colonized by Glomus intraradices or by a mix of arbuscular mycorrhizal fungi collected from a semi-arid grassland. Path analysis modeling was used to evaluate how colonization rates and other variables affected these lethal values. Of several plant and soil characteristics tested, variation in dehydration tolerance was best explained by soil hyphal density. Soil hyphal colonization had larger direct and total effects on both lethal leaf water potential and soil water potential than did root hyphal colonization, root density, soil aggregation, soil glomalin concentration, leaf phosphorus concentration or leaf osmotic potential. Plants colonized by the semi-arid mix of mycorrhizal fungi had lower lethal leaf water potential and soil water potential than plants colonized by G. intraradices. Our findings support the assertion that external, soil hyphae may play an important role in mycorrhizal influence on the water relations of host plants.

Disasters↗
PubMed1986

Identification of sialic acids on the cell surface of hyphae and conidia of the human pathogen Fonsecaea pedrosoi.

Sialic acids were characterized on the cell surface of conidia and hyphae of Fonsecaea pedrosoi, one of the agents of chromoblastomycosis. Neuraminidase-treated conidia had a reduced negative electrophoretic mobility and, in comparison with untreated cells, bound fewer particles of colloidal iron hydroxide and of cationized ferritin. Sialic acid residues in conidia are linked to galactopyranosyl units as indicated by the increased reactivity of neuraminidase-treated cells with peanut agglutinin. N-acetylneuraminic acid was the only derivative found in the mycelium whereas conidia contained both N-glycolyl- and N-acetylneuraminic acids.

Agglutination Tests↗
PubMed1997

Mechanisms and target sites of damage in killing of Candida albicans hyphae by human polymorphonuclear neutrophils.

Target sites of fungal cell damage were studied to define mechanisms of neutrophil-mediated killing of Candida albicans hyphae. Neutrophils induced hyphal cell wall damage, as evidenced by release of cell wall glycoproteins and confocal microscopic changes. Damage occurred in the presence of neutrophil granule extracts and did not require oxidants. However, oxidation of hyphal surface glycoproteins correlated strongly with parallel increments in fungicidal activity, suggesting that oxidants did contribute to maximal cell wall damage. Neutrophil oxidants also induced hyphal DNA fragmentation, primarily single-strand breakage, as shown by increased electrophoretic migration after nuclease-S1 DNA digestion at single-strand break sites. The onset of damage to hyphal cell walls and DNA preceded detectable neutrophil-mediated fungicidal effects. Likewise, hyphal amino acid and nucleotide turnover as well as ATP initially rose, then declined as lethal effects became detectable. Thus, preceding detectable fungal cell death, neutrophil oxidative and oxygen-independent mechanisms damaged defined targets.

Adenosine Triphosphate↗