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At least 145 records · Page 8Linked to original sources
PubMed1988

Transcellular ionic currents studied by intracellular potential recordings in Neurospora crassa hyphae. Transfer of energy from proximal to apical cells.

Membrane potentials, input resistances, and electric coupling in the apical parts of N. crassa growing hyphae were recorded with the aid of intracellular microelectrodes. It was revealed that the apical cells were always depolarized by 10 to 30 mV as compared to the adjacent proximal cells. The septal pore maintained an electrical resistance of 4 to 6 M omega. The calculated values of the endogenous electrical current passing through the septal pore varied between 0.5 and 1 nA. Electrical isolation of the apical cells resulted in their depolarization from 120-150 mV to 40-60 mV, characteristics of the membrane potential value of N. crassa adult hyphae with completely blocked electrogenic pumps. A simultaneous increase in the input resistance value from 15-20 M omega to 40-80 M omega was observed. The above data can be explained assuming that H+-ATPase activity was greatly lowered in the apical cells. Thus in the intact hyphae with electrically coupled cells energy is transferred from the proximal hyphal compartments to the apical ones.

Electric Conductivity↗
PubMed1989

The developmental fate of S. coelicolor hyphae depends upon a gene product homologous with the motility sigma factor of B. subtilis.

In the mycelial prokaryote S. coelicolor, whiG is a gene dispensable for growth but needed for the earliest stages of spore formation in aerial hyphae. Nucleotide sequencing indicates that whiG encodes an RNA polymerase sigma factor highly similar to the motility sigma factor (sigma 28) of B. subtilis. High copy number of an intact whiG gene caused sporulation in vegetative hyphae that are usually fated to lyse without sporulating. However, the introduction of many copies of a sigma 28-dependent promoter from B. subtilis into S. coelicolor reduced sporulation, suggesting partial sequestration of the whiG gene product by the foreign promoter sequences. We propose that the level of whiG sigma factor is crucial in determining the developmental fate of hyphae.

Amino Acid Sequence↗
PubMed1983

cAMP levels and in situ measurement of adenylate cyclase and cAMP phosphodiesterase activities during yeast-to-hyphae transition in the dimorphic fungus Mucor rouxii.

Intracellular levels of cAMP and specific activities of adenylate cyclase and cAMP phosphodiesterase were measured during yeast-to-hyphae transition in the dimorphic fungus M. rouxii. Enzymatic activities were measured in permeabilized cells under conditions preventing protein dephosphorylation and proteolysis. A two-fold decrease in intracellular cAMP levels occurred shortly after exposure of the yeast to air quite before morphological changes became evident. Morphogenesis to hyphae after exposure to air was inhibited by the addition of 10 mM dibutyryl cAMP to the culture medium, and the yeast morphology was maintained for at least 24 hours. The decrease in cAMP levels that occurs shortly after exposure of yeast culture to air was mainly accounted for by variations in the state of activation of cAMP phosphodiesterase while the specific activity of adenylate cyclase did not vary significantly during yeast-to-hyphae transition.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed2000

Mapping the growth of fungal hyphae: orthogonal cell wall expansion during tip growth and the role of turgor.

By computer-enhanced videomicroscopy, we mapped the trajectory of external and internal cell surface markers in growing fungal hyphae to determine the pattern of cell wall expansion during apical growth. Carbon particles (India ink) were chosen as external markers for tip expansion of Rhizoctonia solani hyphae. Irregularities in the growing apical walls of R. solani served as internal markers. Marker movement was traced in captured frames from the videotaped sequences. External and internal markers both followed orthogonal trajectories; i.e., they moved perpendicular to the cell surface regardless of their initial position in the hyphal apex. We found no evidence that the tip rotates during elongation. The discovery that the cell wall of a growing hypha expands orthogonally has major repercussions on two fronts: 1) It supports the long-held view that turgor pressure is the main force driving cell wall expansion. 2) It provides crucial information to complete the mathematical derivation of a three-dimensional model of hyphal morphogenesis based on the vesicle supply center concept. In three dimensions, the vesicle gradient generated by the vesicle supply center is insufficient to explain shape; it is also necessary to know the manner in which the existing surface is displaced during wall expansion.

Biophysical Phenomena↗
PubMed2000

Rad6p represses yeast-hypha morphogenesis in the human fungal pathogen Candida albicans.

Rad6p plays important roles in post-replication DNA repair, chromatin organization, gene silencing and meiosis. In this study, we show that Rad6p also regulates yeast-hypha morphogenesis in the human pathogen Candida albicans. CaRAD6 gene and cDNAs were isolated and characterized revealing that the gene carries two 5'-proximal introns. CaRad6p shows a high degree of sequence similarity to Rad6 proteins from fungi to man (60-83% identity), and it suppresses the UV sensitivity and lack of induced mutagenesis displayed by a Saccharomyces cerevisiae rad6 mutant. In C. albicans, CaRAD6 expression is induced in response to UV, and CaRad6p depletion confers UV sensitivity, confirming that Rad6p serves a role in protecting this fungus against UV damage. CaRAD6 overexpression inhibits hyphal development, whereas CaRad6p depletion enhances hyphal growth. Also, CaRAD6 mRNA levels decrease during the yeast-hypha transition. These effects are dependent on Efg1p, but not Cph1p, indicating that CaRad6p acts specifically through the Efg1p morphogenetic signalling pathway to repress yeast-hypha morphogenesis.

Amino Acid Sequence↗
PubMed1999

PR-1 protein inhibits the differentiation of rust infection hyphae in leaves of acquired resistant broad bean.

Treatment of broad bean leaves with salicylic acid (SA) or 2, 6-dichloro-isonicotinic acid (DCINA) induces resistance against the rust fungus Uromyces fabae resulting in reduced rust pustule density. Light-microscopy studies showed that in induced resistant plants the rust fungus is inhibited immediately after penetration through the stomatal pore. The differentiation of infection structures growing within the intercellular space of the leaf, i.e. infection hyphae and haustorial mother cells, is inhibited. Furthermore, low-temperature scanning electron microscopy studies of freeze fractures revealed protrusions at the tips of infection hyphae growing in induced resistant broad bean leaves. Treatment of in vitro-differentiating rust infection structures with intercellular fluids (IFs) from induced resistant plants confirmed that the fungus is sensitive towards an apoplastic anti-fungal activity only after having formed appressoria. Other legume rusts such as U. vignae and U. appendiculatus were likewise inhibited in the presence of IF from SA-treated broad bean leaves. Heterologous antibodies were used to study changes in the extracellular pathogenesis-related (PR) protein pattern after resistance induction. Western blots indicated that chitinases and beta-1,3-glucanases were present in both induced and control plants. In contrast, PR-1 proteins were newly synthesized in response to SA or DCINA application. The major induced PR-1 protein was purified and exhibited strong differentiation-inhibiting activity towards U. fabae infection structures. We conclude that the inhibition of rust infection hyphae in acquired resistant broad bean plants is mainly due to the anti-fungal activity of this induced basic PR-1 protein.

Antifungal Agents↗
PubMed1988

Transcellular proton current in Achlya bisexualis hyphae: relationship to polarized growth.

Growing hyphae of Achlya bisexualis drive an electric current through themselves, such that positive charge flows into the apical region (the anterior 300 micron) and exits distally along the hyphal trunk. They also generate a gradient of extracellular pH, such that the medium surrounding the apex is slightly alkaline whereas that along the hyphal trunk is acid. To explore the genesis of these gradients and their relationship to polarized extension, we examined the effects of changes in the composition of the growth medium. The transcellular electric current was most pronounced in medium rich in amino acids. In leaner medium, containing limited amounts of amino acids or none at all, the current was attenuated or absent. We interpret the results to mean that inward current represents H+/amino acid symport, mediated by porters that are preferentially localized in the apical region. Apical alkalinity may be due to ammonia production. Outward current, and perhaps also the generation of metabolic acid, reflects the distribution of the H+-ATPase, which is excluded from the apex but is abundant along the hyphal trunk. Thanks to the spatial segregation of transport functions, protons characteristically flow into the apical region. However, since hyphae grow apically and at the same rate despite wide variations in current pattern, the flow of electric charge through the hyphae cannot be required to polarize extension or to localize the tip.

Amino Acids↗
PubMed1991

Intrahyphal hyphae in corneal tissue from a case of keratitis due to Lasiodiplodia theobromae.

Lasiodiplodia theobromae, a recognized plant pathogen, was isolated in culture from a case of human mycotic keratitis. Chemotherapy with a variety of azoles was unsuccessful and the lesion was removed surgically. Electron microscopy of thin sections of the excised corneal tissue revealed several examples of intrahyphal hyphae, a unique process described previously in in vitro cultures of various zoopathogenic fungi. We believe this to be the first report of the presence of intrahyphal hyphae in parasitized animal or human tissue. The demonstration of this process in vivo is thought to be consistent with the hypothesis that intrahyphal hyphae might represent an attempt by the invading fungus to survive in an otherwise unfavourable environment.

Cornea↗
PubMed1986

Selectivity to K+ and Na+ of protoplast fractions isolated from different regions of Aspergillus nidulans hyphae.

The selectivity to K+ and Na+ of protoplast samples representing cytoplasm isolated from different regions of the hyphal filament of Aspergillus nidulans was investigated. Concentrations of both ions contained in successive protoplast fractions were measured. During lytic digestion, protoplasts were released first from apical regions and subsequently from progressively older regions of hyphae. A low K+/Na+ ratio was found in protoplasts containing primarily apical cytoplasm and a high K+/Na+ ratio was found in protoplasts originating from older regions of hyphae. The ratios were the same whether MgSO4 or mannitol was used as stabilizer. Absolute concentrations of both ions were higher in protoplasts of apical origin. Protoplasts stabilized in mannitol lost more ions than those stabilized in MgSO4 over an 8 h incubation period. Na+ losses were higher from apical protoplasts whereas K+ losses were higher from protoplasts liberated from older regions of hyphae. The addition of divalent metal cations (1.5 mM-Mn2+ or Mg2+) reduced losses of Na+ from protoplasts but did not affect loss of K+. Data obtained using protoplast samples were related to those obtained for intact mycelium. Absolute losses of both ions from mycelium were lower than for protoplasts but when compared on a protein basis the data suggested that protoplasts possess properties similar to those of intact mycelium in terms of K+ and Na+ selectivity.

Aspergillus nidulans↗
PubMed1997

A Candida albicans RAS-related gene (CaRSR1) is involved in budding, cell morphogenesis and hypha development.

Candida albicans, the most important human fungal pathogen, is a dimorphic fungus that can grow either as a yeast or as a hyphal form in response to medium conditions. A RAS-related C. albicans gene (CaRSR1) was isolated as a suppressor of a cdc24ts bud-emergence mutation of the baker's yeast, Saccharomyces cerevisiae. The deduced protein encoded by CaRSR1 is 248 amino acids long and 56% identical to that encoded by the S. cerevisiae RSR1 (BUD1) gene. Disruption of CaRSR1 in C. albicans indicated that CaRSR1 is involved in both yeast and hypha development. In the yeast phase, CaRSR1 is required for normal (polar) bud site selection and is involved in cell morphogenesis; in the yeast-mycelial transition it is involved in germ tube emergence; and in the development of the hyphae it is involved in cell elongation. The disruption of CaRSR1 leads to reduced virulence in both heterozygote and homozygote disruptants in a dose-dependent manner. The reduced virulence can be attributed to the reduced germination and shorter hyphae resulting from the disruption of CaRSR1.

Amino Acid Sequence↗
PubMed1976

Acid phosphatase activity in the wild-type and B-mutant hyphae of Schizophyllum commune.

In the wild-type and B-mutant hyphae of Schizophyllum commune, acid phosphatase activity was found in association with vacuoles, lipid bodies, and endoplasmic reticulum. Small granules containing acid phosphatase also occurred in mitochondria and along the nuclear envelope. Both ultrastructural and biochemical studies indicated greater acid phosphatase activity in the B-mutant than in the wild-type hyphae, which suggests that the mutation in the B incompatibility factor increases the production of the acid phosphatase in the mutant hyphae.

Acid Phosphatase↗
PubMed1996

hymA (hypha-like metulae), a new developmental mutant of Aspergillus nidulans.

Asexual fruiting body development in Aspergillus nidulans requires a precise spatial and temporal coordinated expression of many genes. Insertional mutagenesis was used to isolate and characterize a new mutant of A. nidulans in which hyphal growth was slightly reduced and conidiophore development was specifically blocked at the metula stage. In contrast to the uninucleate metulae of the wild-type, in the mutant these structures were elongated, multinucleate and septate. Further differentiation and production of phialides by a budding-like process was not observed. The mutant metulae thus resembled hyphae rather than metulae and the gene was therefore named hypha-like metulae (hymA). The hymA gene was mapped to linkage group VI. The integrated vector was rescued with border sequences from the integration site. The border sequences were used to isolate a cosmid from a wild-type library which was subcloned to a 5 kb fragment able to complement the mutation in trans. This fragment encoded a 1.8 kb transcript expressed in hyphae and throughout development. It is proposed that hymA is involved in budding processes, and is required for the formation of metulae and for their further differentiation.

Aspergillus nidulans↗
PubMed2006

Rad52 depletion in Candida albicans triggers both the DNA-damage checkpoint and filamentation accompanied by but independent of expression of hypha-specific genes.

We have analysed the effect of RAD52 deletion in several aspects of the cell biology of Candida albicans. Cultures of rad52Delta strains exhibited slow growth and contained abundant cells with a filamentous morphology. Filamentation with polarization of actin patches was accompanied by the induction of the hypha-specific genes (HSG) ECE1, HWP1 and HGC1. However, filament formation occurred in the absence of the transcription factors Efg1 and Cph1, even though disruption of EFG1 prevented expression of HSG. Therefore, expression of HSG genes accompanies but is dispensable for rad52Delta filamentation. However, deletion of adenylate cyclase severely impaired filamentation, this effect being largely reverted by the addition of exogenous cAMP. Filaments resembled elongated pseudohyphae, but some of them looked like true hyphae. Following depletion of Rad52, many cells arrested at the G2/M phase of the cell cycle with a single nucleus suggesting the early induction of the DNA-damage checkpoint. Filaments formed later, preferentially from G2/M cells. The filamentation process was accompanied by the uncoupling of several landmark events of the cell cycle and was partially dependent on the action of the cell cycle modulator Swe1. Hyphae were still induced by serum, but a large number of rad52 cells myceliated in G2/M.

Actin Cytoskeleton↗
PubMed1997

The formation of hyphae of Candida albicans induced by cyclodextrins.

Hyphal growth of Candida albicans was observed when yeast was cultured at 27 degrees C in liquid media containing 1% Tripcasine and 1.8% cyclodextrins (alpha, beta, and gamma respectively). Tripcasine as the sole nitrogen source did not induce the formation of hyphae of C. albicans, but cyclodextrins, especially CD-beta, were able to induce yeast-mycelial transition. In the TCD-beta media 25-30% septate hyphae form was observed. This study indicates the existence of an uptake system for CDs in C. albicans, provided these compounds are linearised in the medium. The CDs are inducers of hyphae and they may enter the C. albicans cells as linear oligosaccharids.

Candida albicans↗
PubMed1998

Characterization of an Aspergillus nidulans mutant with abnormal distribution of nuclei in hyphae, metulae, phialides and conidia.

The V10 deteriorated variant of Aspergillus nidulans has hyphae, metulae, phialides and conidia with abnormal nuclear distributions. The alterations observed were: increase in the number of nuclei in hyphae, metulae and phialides, presence of anucleate, uninucleate and multinucleate conidia, abnormal vegetative growth and defection conidiation. When 0.5 M NaCl was added to the medium, an increase in the number of conidia was observed but their morphology and number of nuclei were not modified. The gene responsible for these alterations was named anuA1. The anuA1 gene is located on linkage group VII and is possibly involved in nuclear migration to hyphae, metulae, phialides and conidia.

Aspergillus nidulans↗
PubMed2001

Changes in glycogen and trehalose content of Streptomyces brasiliensis hyphae during growth in liquid cultures under sporulating and non-sporulating conditions.

Streptomyces brasiliensis ATCC 23727 showed extensive sporulation when cultured in a liquid medium containing galactose and glutamic acid as carbon and nitrogen sources. Under such conditions, glycogen and trehalose are accumulated in the hyphae coinciding with spore formation. The results reported here suggest that glycogen accumulated in sporogenic hyphae is converted into trehalose during the final period of spore maturation. Glycogen is also accumulated in the hyphae when S. brasiliensis is cultured under conditions which did not support sporulation. Under such conditions, however, glycogen degradation is not accompanied by accumulation of trehalose. This suggest that the conversion of glycogen into trehalose might be a sporulation-specific event in streptomycetes.

Glycogen↗
PubMed2001

Expressed genes in the extraradical hyphae of an arbuscular mycorrhizal fungus, Glomus intraradices, in the symbiotic phase.

To collect extraradical hyphae of arbuscular mycorrhizal (AM) fungi for RNA isolation, a PVDF membrane was laid on the hyphal compartment of a two-compartment culture system of transformed carrot hairy roots and Glomus intraradices. Extraradical hyphae free from host tissue were easily collected, and their RNA was rapidly extracted with a modified acid guanidinium thiocyanate-phenol-chloroform method. A 3'-RACE (rapid amplification of cDNA ends) of a known gene indicated that this protocol enabled the isolation of mRNA molecules as small as 2.3 kb. The cDNA libraries of an AM fungus from the aseptic extraradical hyphae in a symbiotic state were constructed for the first time. Three-fourth of 150 ESTs (expressed sequence tags) indicated low or no similarities to known sequences from other organisms.

DNA, Complementary↗
PubMed2006

Posaconazole enhances the activity of amphotericin B against Aspergillus hyphae in vitro.

The MICs and fractional inhibitory concentrations of posaconazole (POS) and voriconazole (VRZ), alone and in combination with amphotericin B (AMB), for the conidia and hyphae of 100 Aspergillus isolates were evaluated. POS-AMB had more synergistic activity against hyphae (75% of isolates) than VRZ-AMB (37%) and significantly more synergistic activity against hyphae than against conidia (12%).

Amphotericin B↗