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At least 253 records · Page 14Linked to original sources
PubMed2004

Cerato-platanin protein is located in the cell walls of ascospores, conidia and hyphae of Ceratocystis fimbriata f. sp. platani.

Cerato-platanin (CP), a protein of about 12.4 kDa from Ceratocystis fimbriata f. sp. platani (Cfp), accumulated in the mycelium and was located in the cell walls of Cfp ascospores, hyphae and conidia suggesting that this protein had a role in forming the fungal cell wall apart from the already known fact that it is secreted early in culture and elicits phytoalexin synthesis and/or plant cell death. The finding was obtained with three immunological techniques: a quantitative ELISA which determines the amount of CP in the mycelium, an immunofluorescence assay, and immunogold labelling to define the exact localization of CP in the Cfp cells.

Ascomycota↗
PubMed2005

Nuclear behavior in fungal hyphae.

A characteristic feature of fungal hypha is the presence of large number of nuclei in a common cytoplasmic environment. Where it has been examined, the coenocytic mycelium is commonly heterokaryotic. The nuclei cooperate, compete or combat. It is proposed that in addition to their classical role in heredity, supernumerary nuclei in filamentous fungi serve as store house for nitrogen and phosphorus in the form of DNA which is degraded by regulated autophagy. The breakdown products recycled, giving hyphal tips the capability of persistent extension and foraging in new areas.

Cell Division↗
PubMed2005

The diffusive vesicle supply center model for tip growth in fungal hyphae.

We propose the diffusive vesicle supply center model for tip growth in fungal hyphae. The model is based on the three-dimensional vesicle supply center (VSC) model [Gierz, G., Bartnicki-García, S., 2001. A three-dimensional model of fungal morphogenesis based on the vesicle supply center concept: J. Theor. Biol. 208, 151-164], but incorporates two aspects of a more realistic vesicle delivery mechanism: vesicle diffusion from the VSC and a finite rate constant for vesicle fusion with the cell membrane. We develop a framework to describe tip growth for a general class of models based on the vesicle supply center concept. Combining this with a method for calculating the steady state distribution of diffusive vesicles we iteratively solve for stationary cell shapes. These show a blunter tip than predicted by the original VSC model, which we attribute to increased forward-directed vesicle delivery via diffusion. The predicted distance between the VSC and the utmost tip of the cell is set by the ratio between the diffusion constant and the rate constant for vesicle exocytosis. Combined with the cell radius, these define the only dimensionless parameter for our model.

Cytoplasmic Vesicles↗
PubMed2005

Homologues of yeast polarity genes control the development of multinucleated hyphae in Ashbya gossypii.

A few years ago, A. gossypii became recognized as an attractive model to study the growth of long and multinucleated fungal cells (hyphae) because of its small genome, haploid nuclei, and efficient gene targeting methods. It is generally assumed that a better understanding of filamentous fungal growth will greatly stimulate the development of novel fungicides. The use of Ashbya gossypii as a model is particularly promising because of the high level of gene order conservation (synteny) between the genomes of A. gossypii and the yeast Saccharomyces cerevisiae. Thus, a similar set of genes seems to control the surprisingly different growth modes of these two organisms, which predicts that orthologous growth control genes might not play identical cellular roles in both systems. Analyzing the phenotypes of A. gossypii mutants lacking factors with known functions in yeast morphogenesis and nuclear dynamics confirm this hypothesis. Comparative genomics of both organisms also reveals rare examples of differences in the gene sets for some cellular processes, which as shown for phosphate homeostasis can be associated with differences in control levels.

Cell Polarity↗
PubMed2006

TLR2, but not TLR4, triggers cytokine production by murine cells in response to Candida albicans yeasts and hyphae.

Toll-like receptors (TLRs) function as sensors for infection that induce the activation of the immune responses. Recent studies have demonstrated a crucial involvement of TLRs in the recognition of fungal pathogens such as Candida albicans. Although both TLR2 and TLR4 have been implicated in the host interaction with C. albicans, their specific role during infection has not been unequivocally established, as conflicting results have been reported. In this review, we summarize and discuss our own and others' key findings about the specific role of TLR2 and TLR4 in murine resistance to candidiasis, and in triggering cytokine secretion by murine cells in response to C. albicans yeasts and hyphae.

Animals↗
PubMed2003

Does endocytosis occur in fungal hyphae?

The evidence and arguments for and against the occurrence of endocytosis in fungal hyphae are summarized. The balance of evidence is in favour of the existence of endocytosis. This is supported by an analysis of the recently sequenced Neurospora genome which strongly suggests that this fungus possesses the complex protein machinery required to conduct endocytosis.

Actins↗
PubMed2004

Hgc1, a novel hypha-specific G1 cyclin-related protein regulates Candida albicans hyphal morphogenesis.

The human fungal pathogen Candida albicans switches from yeast to hyphal growth when exposed to serum or phagocytosed. However, the importance of this morphological switch for virulence remains highly controversial due to the lack of a mutant that affects hyphal morphogenesis only. Although many genes specifically expressed in hyphal cells have been identified and shown to encode virulence factors, none is required for hyphal morphogenesis. Here we report the first hypha-specific gene identified, HGC1, which is essential for hyphal morphogenesis. Deletion of HGC1 abolished hyphal growth in all laboratory conditions tested and in the kidneys of systemically infected mice with markedly reduced virulence. HGC1 expression is co-regulated with other virulence genes such as HWP1 by the cAMP/protein kinase A signaling pathway and transcriptional repressor Tup1/Nrg1. Hgc1 is a G1 cyclin-related protein and co-precipitated with the cyclin-dependent kinase (Cdk) CaCdc28. It has recently emerged that cyclin/Cdk complexes promote other forms of polarized cell growth such as tumor cell migration and neurite outgrowth. C. albicans seems to have adapted a conserved strategy to control specifically hyphal morphogenesis.

Actins↗
PubMed2003

Selective effects of interleukin (IL)-15 on antifungal activity and IL-8 release by polymorphonuclear leukocytes in response to hyphae of Aspergillus species.

The effects of interleukin (IL)-15 on human polymorphonuclear leukocyte (PMNL) activity against Aspergillus fumigatus and Aspergillus flavus were investigated. Pretreatment with IL-15 for 2 h increased PMNL oxidative burst, as measured by superoxide anion (O(2)(-)) release in response to A. fumigatus (P<.05) but not to A. flavus. However, after 22-h, but not 2-h, treatment with IL-15, there was significant enhancement in PMNL-mediated hyphal damage to A. fumigatus. Furthermore, 22-h exposure to IL-15 mediated an enhanced release of IL-8 from PMNLs challenged with hyphae of A. fumigatus and A. flavus (P<.05). In contrast, IL-15 treatment did not affect the release of tumor necrosis factor-alpha from PMNLs. The selective time- and species-dependent enhancement of O(2)(-) production and hyphal damage, as well as its induction of IL-8 release, suggest that IL-15 may play an important role in the immunomodulation of host response to invasive aspergillosis.

Aspergillus↗
PubMed2006

Regulation of Cdc42 GTPase activity in the formation of hyphae in Candida albicans.

The human fungal pathogen Candida albicans can switch between yeast, pseudohyphal, and hyphal morphologies. To investigate whether the distinctive characteristics of hyphae are due to increased activity of the Cdc42 GTPase, strains lacking negative regulators of Cdc42 were constructed. Unexpectedly, the deletion of the Cdc42 Rho guanine dissociation inhibitor RDI1 resulted in reduced rather than enhanced polarized growth. However, when cells lacking both Cdc42 GTPase-activating proteins, encoded by RGA2 and BEM3, were grown under pseudohyphal-promoting conditions the bud was highly elongated and lacked a constriction at its base, so that its shape resembled a hyphal germ tube. Moreover, a Spitzenkörper was present at the bud tip, a band of disorganized septin was present at bud base, true septin rings formed within the bud, and nuclei migrated out of the mother cell before the first mitosis. These are all characteristic features of a hyphal germ tube. Intriguingly, we observed hyphal-specific phosphorylation of Rga2, suggesting a possible mechanism for Cdc42 activation during normal hyphal development. In contrast, expression of Cdc42(G12V), which is constitutively GTP bound because it lacks GTPase activity, resulted in swollen cells with prominent and stable septin bars. These results suggest the development of hyphal-specific characteristics is promoted by Cdc42-GTP in a process that also requires the intrinsic GTPase activity of Cdc42.

Alleles↗
PubMed2006

Morphogenetic surfactants and their role in the formation of aerial hyphae in Streptomyces coelicolor.

Withstanding environmental adversity and seeking optimal conditions for reproduction are basic requirements for the survival of all organisms. Filamentous bacteria of the genus Streptomyces produce a remarkable cell type called the aerial hyphae that is central to its ability to meet both of these challenges. Recent advances have brought about a major shift in our understanding of the cell surface proteins that play important roles in the generation of these cells. Here we review our current understanding of one of these groups of proteins, the morphogenetic surfactants, with emphasis on the SapB protein of Streptomyces coelicolor.

Alanine↗
PubMed2006

The WD-40 repeat protein PkwA of Thermomonospora curvata is associated with rapid growth and is localized in the tips of growing hyphae.

The PkwA protein of the thermophilic actinomycete Thermomonospora curvata has already been reported as the first instance of a WD-40 module-containing protein of prokaryotic origin. This protein is composed of an N-terminal eukaryotic-type protein kinase domain and of seven C-terminal WD-40 repeats. PkwA is a peripheral membrane protein that is linked to the early exponential growth phase of the bacterium. Its intracellular concentrations are extremely low. We have shown that the protein forms high molecular weight complexes and is localized mainly in the tips of the young Thermomonospora vegetative hyphae.

Actinomycetales↗
PubMed2002

The mold-specific MS8 gene is required for normal hypha formation in the dimorphic pathogenic fungus Histoplasma capsulatum.

The dimorphic fungus Histoplasma capsulatum is the etiologic agent of one of the most common systemic mycoses of humans, histoplasmosis. In the environment, H. capsulatum grows in a differentiated mold form and shifts to an undifferentiated yeast form after mold fragments or spores are inhaled. This mold-to-yeast shift is required for disease. Little is known about the molecular biology of dimorphism in Histoplasma, and most studies have been directed toward yeast-specific genes. While it is important to examine the role of genes upregulated in the yeast morphotype, genes which are silenced in the yeast (i.e., mold-specific genes) may also play a critical role in dimorphism. To begin to examine this hypothesis, we report here the first misexpression and knockout analysis of a mold-specific gene in Histoplasma. The strongly expressed MS8 gene encodes a predicted 21-kDa protein extremely rich in glycine and glutamine. Forced expression of MS8 driven by the TEF1 promoter in yeast did not alter the yeast morphology at 37 degrees C or mold formation at 25 degrees C. Yeast expressing MS8 did exhibit clumping in liquid medium and formed "sticky" colonies on agar plates. Allelic replacement of MS8 was accomplished by a positive-negative selection procedure. ms8 knockout mutants formed apparently normal yeast at 37 degrees C but gave rise to aberrant mycelia at 25 degrees C. The mold colonies of the knockouts were less than half as large as normal, had a granular surface, produced a dark-red pigment, and formed short hyphae which were 40% wider with a distinctive twisted "zig-zag" shape.

Amino Acid Sequence↗
PubMed2002

Disruption of the Candida albicans TPS2 gene encoding trehalose-6-phosphate phosphatase decreases infectivity without affecting hypha formation.

Deletion of trehalose-6-phosphate phosphatase, encoded by TPS2, in Saccharomyces cerevisiae results in accumulation of trehalose-6-phosphate (Tre6P) instead of trehalose under stress conditions. Since trehalose is an important stress protectant and Tre6P accumulation is toxic, we have investigated whether Tre6P phosphatase could be a useful target for antifungals in Candida albicans. We have cloned the C. albicans TPS2 (CaTPS2) gene and constructed heterozygous and homozygous deletion strains. As in S. cerevisiae, complete inactivation of Tre6P phosphatase in C. albicans results in 50-fold hyperaccumulation of Tre6P, thermosensitivity, and rapid death of the cells after a few hours at 44 degrees C. As opposed to inactivation of Tre6P synthase by deletion of CaTPS1, deletion of CaTPS2 does not affect hypha formation on a solid glucose-containing medium. In spite of this, virulence of the homozygous deletion mutant is strongly reduced in a mouse model of systemic infection. The pathogenicity of the heterozygous deletion mutant is similar to that of the wild-type strain. CaTPS2 is a new example of a gene not required for growth under standard conditions but required for pathogenicity in a host. Our results suggest that Tre6P phosphatase may serve as a potential target for antifungal drugs. Neither Tre6P phosphatase nor its substrate is present in mammals, and assay of the enzymes is simple and easily automated for high-throughput screening.

Amino Acid Sequence↗
PubMed2006

Killed Candida albicans yeasts and hyphae inhibit gamma interferon release by murine natural killer cells.

Killed yeasts and hyphae of Candida albicans inhibit gamma interferon secretion by highly purified murine NK cells in response to the Toll-like receptor ligands lipopolysaccharide and zymosan. This effect, which is also observed in the presence of NK-activating cytokines (interleukin-2 [IL-2], IL-12, and IL-15), may represent a novel mechanism of immune evasion that contributes to the virulence of C. albicans.

Animals↗
PubMed2002

Conserved serine/threonine kinase encoded by CBK1 regulates expression of several hypha-associated transcripts and genes encoding cell wall proteins in Candida albicans.

The opportunistic fungal pathogen, Candida albicans, is reported to have several potential virulence factors. A potentially significant factor is the ability to undergo morphological transition from yeast to hypha. This alteration of form is accompanied by many changes within the cell, including alterations in gene expression and cell wall composition. We have isolated a gene that encodes a highly conserved serine/threonine kinase that appears to be involved in the regulation of proteins associated with the cell wall. We have assigned the designation CBK1 (cell wall biosynthesis kinase 1) to this gene. Mutants lacking CBK1 form large aggregates of round cells under all growth conditions and lack the ability to undergo morphological differentiation. Additionally, these mutants show an altered pattern of expression of several transcripts encoding proteins associated with the cell wall. The results suggest that the kinase encoded by CBK1 plays a general role in the maintenance and alteration of the cell wall of C. albicans in all morphologies.

Candida albicans↗
PubMed2004

Farnesol, a morphogenetic autoregulatory substance in the dimorphic fungus Candida albicans, inhibits hyphae growth through suppression of a mitogen-activated protein kinase cascade.

Candida albicans grew in hyphal form in RPMI1640, however, addition of farnesol inhibited the formation. Farnesol did not affect the expression of mRNAs related to cAMP-EFG1 pathways. The mRNAs (HST7 and CPH1) in mitogen activated protein kinase (MAP) cascades were decreased in farnesol-treated cells, but CST20 was not. Furthermore, expression of general amino acid permease 1 (GAP1) was decreased by farnesol. We concluded that farnesol inhibits a MAP kinase cascades, and the suppression is a cause of interruption of hyphae formation.

Antifungal Agents↗
PubMed2004

Hyphae formation of Candida albicans is regulated by polyamines.

Candida albicans generally grows in hyphae form in RPMI1640 medium. However, addition of 1,4-diamino-2-butanone (DAB), a competitive inhibitor of ornithine decarboxylase, decreased the amount of polyamines in C. albicans, and induced the proliferation of the C. albicans yeast form. The expression of CYR1 mRNA was significantly inhibited by the addition of DAB compared with that of the control. The amount of intracellular cAMP was also decreased by the addition of DAB. A specific adenylate cyclase inhibitor, cis-N-[2-phenylcyclopentyl]-azacyclotridec-1-en-2-amine (MDL-12,330A) promoted the growth of the yeast form. These results indicated that polyamines exist upstream of the adenylate cyclase-cAMP signal pathway and regulate the transformation of C. albicans.

Candida albicans↗