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1
Hazan, Idit, Marisa Sepulveda-Becerra i Haoping Liu. "Hyphal Elongation Is Regulated Independently of Cell Cycle inCandida albicans". Molecular Biology of the Cell 13, nr 1 (styczeń 2002): 134–45. http://dx.doi.org/10.1091/mbc.01-03-0116.
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The mechanism for apical growth during hyphal morphogenesis inCandida albicans is unknown. Studies fromSaccharomyces cerevisiae indicate that cell morphogenesis may involve cell cycle regulation by cyclin-dependent kinase. To examine whether this is the mechanism for hyphal morphogenesis, the temporal appearance of different spindle pole body and spindle structures, the cell cycle-regulated rearrangements of the actin cytoskeleton, and the phosphorylation state of the conserved Tyr19 of Cdc28 during the cell cycle were compared and found to be similar between yeast and serum-induced hyphal apical cells. These data suggest that hyphal elongation is not mediated by altering cell cycle progression or through phosphorylation of Tyr19 of Cdc28. We have also shown that germ tubes can evaginate before spindle pole body duplication, chitin ring formation, and DNA replication. Similarly, tip-associated actin polarization in each hypha occurs before the events of the G1/S transition and persists throughout the cell cycle, whereas cell cycle-regulated actin assemblies come and go. We have also shown that cells in phases other than G1can be induced to form hyphae. Hyphae induced from G1cells have no constrictions, and the first chitin ring is positioned in the germ tube at various distances from the base. Hyphae induced from budded cells have a constriction and a chitin ring at the bud neck, beyond which the hyphae continue to elongate with no further constrictions. Our data suggest that hyphal elongation and cell cycle morphogenesis programs are uncoupled, and each contributes to different aspects of cell morphogenesis.
2
Kornitzer, Daniel. "Regulation of Candida albicans Hyphal Morphogenesis by Endogenous Signals". Journal of Fungi 5, nr 1 (28.02.2019): 21. http://dx.doi.org/10.3390/jof5010021.
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Candida albicans is a human commensal fungus that is able to assume several morphologies, including yeast, hyphal, and pseudohyphal. Under a range of conditions, C. albicans performs a regulated switch to the filamentous morphology, characterized by the emergence of a germ tube from the yeast cell, followed by a mold-like growth of branching hyphae. This transition from yeast to hyphal growth has attracted particular attention, as it has been linked to the virulence of C. albicans as an opportunistic human pathogen. Signal transduction pathways that mediate the induction of the hyphal transcription program upon the imposition of external stimuli have been extensively investigated. However, the hyphal morphogenesis transcription program can also be induced by internal cellular signals, such as inhibition of cell cycle progression, and conversely, the inhibition of hyphal extension can repress hyphal-specific gene expression, suggesting that endogenous cellular signals are able to modulate hyphal gene expression as well. Here we review recent developments in the regulation of the hyphal morphogenesis of C. albicans, with emphasis on endogenous morphogenetic signals.
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Lee, Hye-Jeong, Jong-Myeong Kim, Woo Kyu Kang, Heebum Yang i Jeong-Yoon Kim. "The NDR Kinase Cbk1 Downregulates the Transcriptional Repressor Nrg1 through the mRNA-Binding Protein Ssd1 in Candida albicans". Eukaryotic Cell 14, nr 7 (22.05.2015): 671–83. http://dx.doi.org/10.1128/ec.00016-15.
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ABSTRACT NDR (nuclear Dbf2-related) kinases are essential components for polarized morphogenesis, cytokinesis, cell proliferation, and apoptosis. The NDR kinase Cbk1 is required for the hyphal growth of Candida albicans ; however, the molecular functions of Cbk1 in hyphal morphogenesis are largely unknown. Here, we report that Cbk1 downregulates the transcriptional repressor Nrg1 through the mRNA-binding protein Ssd1, which has nine Cbk1 phosphorylation consensus motifs. We found that deletion of SSD1 partially suppressed the defective hyphal growth of the C. albicans cbk1 Δ/Δ mutant and that Ssd1 physically interacts with Cbk1. Cbk1 was required for Ssd1 localization to polarized growth sites. The phosphomimetic SSD1 allele ( ssd1-9E ) allowed the cbk1 Δ/Δ mutant to form short hyphae, and the phosphodeficient SSD1 allele ( ssd1-9A ) resulted in shorter hyphae than did the wild-type SSD1 allele, indicating that Ssd1 phosphorylation by Cbk1 is important for hyphal morphogenesis. Furthermore, we show that the transcriptional repressor Nrg1 does not disappear during hyphal initiation in the cbk1 Δ/Δ mutant but is completely absent in the cbk1 Δ/Δ ssd1 Δ/Δ double mutant. Deletion of SSD1 also increased Als3 expression and internalization of the cbk1 Δ/Δ mutant in the human embryonic kidney cell line HEK293T. Collectively, our results suggest that one of the functions of Cbk1 in the hyphal morphogenesis of C. albicans is to downregulate Nrg1 through Ssd1.
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Bartnicki-Garcia, S., D. D. Bartnicki i G. Gierz. "Determinants of fungal cell wall morphology: the vesicle supply center". Canadian Journal of Botany 73, S1 (31.12.1995): 372–78. http://dx.doi.org/10.1139/b95-271.
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Because fungal cell walls are shaped during construction, factors that regulate wall biogenesis must play a decisive role in morphogenesis. By delivering ingredients for wall formation in vesicles, fungi have a de facto mechanism to mold their own shape. The gradients in wall formation required for cell morphogenesis ensue from the pattern of vesicle discharge. A vesicle-based, mathematical model of fungal morphogenesis revealed that a relatively simple process could establish these gradients. The model and its underlying hyphoid equation assumes that wall-building vesicles emanate from a vesicle supply center (VSC). The VSC serves as an organizing center from which vesicles would move radially to the cell surface in all directions at random. VSC displacement is then an immediate cause of morphogenesis: a sustained linear displacement of the VSC would generate a polarized pattern of exocytosis required to make a hypha. The model predicts that the Spitzenkörper functions as a VSC. We have tested this prediction by analyzing instances where dislocations in Spitzenkörper position result in hyphal deformations. When the VSC was programmed to duplicate the movements of the Spitzenkörper before, during, and after a deformation, the resulting shapes mimicked closely the observed deformations. These correlations support the contention that the position and movement of the VSC determines the morphology of the fungal cell wall. The computer model has been refined to incorporate transverse random oscillations of the VSC to simulate more realistically the meandering shape of fungal hyphae. The model predicts that hyphal ring formation results from a sustained directional bias to the transverse oscillations of the Spitzenkörper. Key words: hyphal morphogenesis, Spitzenkörper, vesicle supply center, mathematical model, hyphoid equation, hyphal curvature.
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Naseem, Shamoon, Esteban Araya i James B. Konopka. "Hyphal growth inCandida albicansdoes not require induction of hyphal-specific gene expression". Molecular Biology of the Cell 26, nr 6 (15.03.2015): 1174–87. http://dx.doi.org/10.1091/mbc.e14-08-1312.
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Various stimuli, including N-acetylglucosamine (GlcNAc), induce the fungal pathogen Candida albicans to switch from budding to hyphal growth. Previous studies suggested that hyphal morphogenesis is stimulated by transcriptional induction of a set of genes that includes known virulence factors. To better understand hyphal development, we examined the role of GlcNAc metabolism using a triple mutant lacking the genes required to metabolize exogenous GlcNAc ( hxk1Δ nag1Δ dac1Δ). Surprisingly, at low ambient pH (∼pH 4), GlcNAc stimulated this mutant to form hyphae without obvious induction of hyphal genes. This indicates that GlcNAc can stimulate a separate signal to induce hyphae that is independent of transcriptional responses. Of interest, GlcNAc could induce the triple mutant to express hyphal genes when the medium was buffered to a higher pH (>pH 5), which normally occurs after GlcNAc catabolism. Catabolism of GlcNAc raises the ambient pH rather than acidifying it, as occurs after dextrose catabolism. This synergy between alkalinization and GlcNAc to induce hyphal genes involves the Rim101 pH-sensing pathway; GlcNAc induced rim101Δ and dfg16Δ mutants to form hyphae, but hyphal gene expression was partially defective. These results demonstrate that hyphal morphogenesis and gene expression can be regulated independently, which likely contributes to pathogenesis at different host sites.
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Moreno-Ruiz, Dubraska, Linda Salzmann, Mark Fricker, Susanne Zeilinger i Alexander Lichius. "Stress-Activated Protein Kinase Signalling Regulates Mycoparasitic Hyphal-Hyphal Interactions in Trichoderma atroviride". Journal of Fungi 7, nr 5 (6.05.2021): 365. http://dx.doi.org/10.3390/jof7050365.
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Trichoderma atroviride is a mycoparasitic fungus used as biological control agent against fungal plant pathogens. The recognition and appropriate morphogenetic responses to prey-derived signals are essential for successful mycoparasitism. We established microcolony confrontation assays using T. atroviride strains expressing cell division cycle 42 (Cdc42) and Ras-related C3 botulinum toxin substrate 1 (Rac1) interactive binding (CRIB) reporters to analyse morphogenetic changes and the dynamic displacement of localized GTPase activity during polarized tip growth. Microscopic analyses showed that Trichoderma experiences significant polarity stress when approaching its fungal preys. The perception of prey-derived signals is integrated via the guanosine triphosphatase (GTPase) and mitogen-activated protein kinase (MAPK) signalling network, and deletion of the MAP kinases Trichoderma MAPK 1 (Tmk1) and Tmk3 affected T. atroviride tip polarization, chemotropic growth, and contact-induced morphogenesis so severely that the establishment of mycoparasitism was highly inefficient to impossible. The responses varied depending on the prey species and the interaction stage, reflecting the high selectivity of the signalling process. Our data suggest that Tmk3 affects the polarity-stress adaptation process especially during the pre-contact phase, whereas Tmk1 regulates contact-induced morphogenesis at the early-contact phase. Neither Tmk1 nor Tmk3 loss-of-function could be fully compensated within the GTPase/MAPK signalling network underscoring the crucial importance of a sensitive polarized tip growth apparatus for successful mycoparasitism.
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Min, Kyunghun, Thomas F. Jannace, Haoyu Si, Krishna R. Veeramah, John D. Haley i James B. Konopka. "Integrative multi-omics profiling reveals cAMP-independent mechanisms regulating hyphal morphogenesis in Candida albicans". PLOS Pathogens 17, nr 8 (16.08.2021): e1009861. http://dx.doi.org/10.1371/journal.ppat.1009861.
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Microbial pathogens grow in a wide range of different morphologies that provide distinct advantages for virulence. In the fungal pathogen Candida albicans, adenylyl cyclase (Cyr1) is thought to be a master regulator of the switch to invasive hyphal morphogenesis and biofilm formation. However, faster growing cyr1Δ/Δ pseudorevertant (PR) mutants were identified that form hyphae in the absence of cAMP. Isolation of additional PR mutants revealed that their improved growth was due to loss of one copy of BCY1, the negative regulatory subunit of protein kinase A (PKA) from the left arm of chromosome 2. Furthermore, hyphal morphogenesis was improved in some of PR mutants by multigenic haploinsufficiency resulting from loss of large regions of the left arm of chromosome 2, including global transcriptional regulators. Interestingly, hyphal-associated genes were also induced in a manner that was independent of cAMP. This indicates that basal protein kinase A activity is an important prerequisite to induce hyphae, but activation of adenylyl cyclase is not needed. Instead, phosphoproteomic analysis indicated that the Cdc28 cyclin-dependent kinase and the casein kinase 1 family member Yck2 play key roles in promoting polarized growth. In addition, integrating transcriptomic and proteomic data reveals hyphal stimuli induce increased production of key transcription factors that contribute to polarized morphogenesis.
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Pulver, Rebecca, Timothy Heisel, Sara Gonia, Robert Robins, Jennifer Norton, Paula Haynes i Cheryl A. Gale. "Rsr1 Focuses Cdc42 Activity at Hyphal Tips and Promotes Maintenance of Hyphal Development in Candida albicans". Eukaryotic Cell 12, nr 4 (7.12.2012): 482–95. http://dx.doi.org/10.1128/ec.00294-12.
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ABSTRACTThe extremely elongated morphology of fungal hyphae is dependent on the cell's ability to assemble and maintain polarized growth machinery over multiple cell cycles. The different morphologies of the fungusCandida albicansmake it an excellent model organism in which to study the spatiotemporal requirements for constitutive polarized growth and the generation of different cell shapes. InC. albicans, deletion of the landmark protein Rsr1 causes defects in morphogenesis that are not predicted from study of the orthologous protein in the related yeastSaccharomyces cerevisiae, thus suggesting that Rsr1 has expanded functions during polarized growth inC. albicans. Here, we show that Rsr1 activity localizes to hyphal tips by the differential localization of the Rsr1 GTPase-activating protein (GAP), Bud2, and guanine nucleotide exchange factor (GEF), Bud5. In addition, we find that Rsr1 is needed to maintain the focused localization of hyphal polarity structures and proteins, including Bem1, a marker of the active GTP-bound form of the Rho GTPase, Cdc42. Further, our results indicate that tip-localized Cdc42 clusters are associated with the cell's ability to express a hyphal transcriptional program and that the ability to generate a focused Cdc42 cluster in early hyphae (germ tubes) is needed to maintain hyphal morphogenesis over time. We propose that inC. albicans, Rsr1 “fine-tunes” the distribution of Cdc42 activity and that self-organizing (Rsr1-independent) mechanisms of polarized growth are not sufficient to generate narrow cell shapes or to provide feedback to the transcriptional program during hyphal morphogenesis.
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Martin, Stephen W., i James B. Konopka. "Lipid Raft Polarization Contributes to Hyphal Growth in Candida albicans". Eukaryotic Cell 3, nr 3 (czerwiec 2004): 675–84. http://dx.doi.org/10.1128/ec.3.3.675-684.2004.
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ABSTRACT The polarization of sterol- and sphingolipid-enriched domains (lipid rafts) has been linked to morphogenesis and cell movement in diverse cell types. In the yeast Saccharomyces cerevisiae, a dramatic polarization of sterol-rich domains to the shmoo tip was observed in pheromone-induced cells (M. Bagnat and K. Simons, Proc. Natl. Acad. Sci. USA 99:14183-14188, 2002). We therefore examined whether plasma membrane lipid polarization contributes to the ability of the fungal pathogen Candida albicans to grow in a highly polarized manner to form hyphae. Interestingly, staining with filipin revealed that membrane sterols were highly polarized to the leading edge of growth during all stages of hyphal growth. Budding and pseudohyphal cells did not display polarized staining. Filipin staining was also enriched at septation sites in hyphae, where colocalization with septin proteins was observed, suggesting a role for the septins in forming a boundary domain. Actin appeared to play a role in sterol polarization and hyphal morphogenesis in that both were disrupted by low concentrations of latrunculin A that did not prevent budding. Furthermore, blocking either sphingolipid biosynthesis with myriocin or sterol biosynthesis with ketoconazole resulted in a loss of ergosterol polarization and caused abnormal hyphal morphogenesis, suggesting that lipid rafts are involved. Since hyphal growth is required for the full virulence of C. albicans, these results suggest that membrane polarization may contribute to the pathogenesis of this organism.
10
Bensen, Eric S., Scott G. Filler i Judith Berman. "A Forkhead Transcription Factor Is Important for True Hyphal as well as Yeast Morphogenesis in Candida albicans". Eukaryotic Cell 1, nr 5 (październik 2002): 787–98. http://dx.doi.org/10.1128/ec.1.5.787-798.2002.
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ABSTRACT Candida albicans is an important pathogen of immunocompromised patients which grows with true hyphal, pseudohyphal, and yeast morphologies. The dynamics of cell cycle progression are markedly different in true hyphal relative to pseudohyphal and yeast cells, including nuclear movement and septin ring positioning. In Saccharomyces cerevisiae, two forkhead transcription factors (ScFKH1 and ScFKH2) regulate the expression of B-cyclin genes. In both S. cerevisiae and Schizosaccharomyces pombe, forkhead transcription factors also influence morphogenesis. To explore the molecular mechanisms that connect C. albicans morphogenesis with cell cycle progression, we analyzed CaFKH2, the single homolog of S. cerevisiae FKH1/FKH2. C. albicans cells lacking CaFkh2p formed constitutive pseudohyphae under all yeast and hyphal growth conditions tested. Under hyphal growth conditions levels of hyphae-specific mRNAs were reduced, and under yeast growth conditions levels of several genes encoding proteins likely to be important for cell wall separation were reduced. Together these results imply that Fkh2p is required for the morphogenesis of true hyphal as well as yeast cells. Efg1p and Cph1p, two transcription factors that contribute to C. albicans hyphal growth, were not required for the pseudohyphal morphology of fkh2 mutants, implying that Fkh2p acts in pathways downstream of and/or parallel to Efg1p and Cph1p. In addition, cells lacking Fkh2p were unable to damage human epithelial or endothelial cells in vitro, suggesting that Fkh2p contributes to C. albicans virulence.
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Hausauer, Danielle L., Maryam Gerami-Nejad, Cassandra Kistler-Anderson i Cheryl A. Gale. "Hyphal Guidance and Invasive Growth in Candida albicans Require the Ras-Like GTPase Rsr1p and Its GTPase-Activating Protein Bud2p". Eukaryotic Cell 4, nr 7 (lipiec 2005): 1273–86. http://dx.doi.org/10.1128/ec.4.7.1273-1286.2005.
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ABSTRACT Candida albicans, the most prevalent fungal pathogen of humans, causes superficial mycoses, invasive mucosal infections, and disseminated systemic disease. Many studies have shown an intriguing association between C. albicans morphogenesis and the pathogenesis process. For example, hyphal cells have been observed to penetrate host epithelial cells at sites of wounds and between cell junctions. Ras- and Rho-type GTPases regulate many morphogenetic processes in eukaryotes, including polarity establishment, cell proliferation, and directed growth in response to extracellular stimuli. We found that the C. albicans Ras-like GTPase Rsr1p and its predicted GTPase-activating protein Bud2p localized to the cell cortex, at sites of incipient daughter cell growth, and provided landmarks for the positioning of daughter yeast cells and hyphal cell branches, similar to the paradigm in the model yeast Saccharomyces cerevisiae. However, in contrast to S. cerevisiae, CaRsr1p and CaBud2p were important for morphogenesis: C. albicans strains lacking Rsr1p or Bud2p had abnormal yeast and hyphal cell shapes and frequent bends and promiscuous branching along the hypha and were unable to invade agar. These defects were associated with abnormal actin patch polarization, unstable polarisome localization at hyphal tips, and mislocalized septin rings, consistent with the idea that GTP cycling of Rsr1p stabilizes the axis of polarity primarily to a single focus, thus ensuring normal cell shape and a focused direction of polarized growth. We conclude that the Rsr1p GTPase functions as a polarity landmark for hyphal guidance and may be an important mediator of extracellular signals during processes such as host invasion.
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Rittenour, William R., Haoyu Si i Steven D. Harris. "Hyphal morphogenesis in Aspergillus nidulans". Fungal Biology Reviews 23, nr 1-2 (luty 2009): 20–29. http://dx.doi.org/10.1016/j.fbr.2009.08.001.
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Harris, Steven D. "Hyphal morphogenesis: an evolutionary perspective". Fungal Biology 115, nr 6 (czerwiec 2011): 475–84. http://dx.doi.org/10.1016/j.funbio.2011.02.002.
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Loeb, Jonathan D. J., Marisa Sepulveda-Becerra, Idit Hazan i Haoping Liu. "A G1 Cyclin Is Necessary for Maintenance of Filamentous Growth in Candida albicans". Molecular and Cellular Biology 19, nr 6 (1.06.1999): 4019–27. http://dx.doi.org/10.1128/mcb.19.6.4019.
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ABSTRACT Candida albicans undergoes a dramatic morphological transition in response to various growth conditions. This ability to switch from a yeast form to a hyphal form is required for its pathogenicity. The intractability of Candida to traditional genetic approaches has hampered the study of the molecular mechanism governing this developmental switch. Our approach is to use the more genetically tractable yeast Saccharomyces cerevisiae to yield clues about the molecular control of filamentation for further studies in Candida. G1 cyclins Cln1 and Cln2 have been implicated in the control of morphogenesis in S. cerevisiae. We show that C. albicans CLN1(CaCLN1) has the same cell cycle-specific expression pattern as CLN1 and CLN2 of S. cerevisiae. To investigate whether G1 cyclins are similarly involved in the regulation of cell morphogenesis during the yeast-to-hypha transition of C. albicans, we mutatedCaCLN1. Cacln1/Cacln1 cells were found to be slower than wild-type cells in cell cycle progression. TheCacln1/Cacln1 mutants were also defective in hyphal colony formation on several solid media. Furthermore, while mutant strains developed germ tubes under several hypha-inducing conditions, they were unable to maintain the hyphal growth mode in a synthetic hypha-inducing liquid medium and were deficient in the expression of hypha-specific genes in this medium. Our results suggest that CaCln1 may coordinately regulate hyphal development with signal transduction pathways in response to various environmental cues.
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Peters, Brian M., Glen E. Palmer, Andrea K. Nash, Elizabeth A. Lilly, Paul L. Fidel i Mairi C. Noverr. "Fungal Morphogenetic Pathways Are Required for the Hallmark Inflammatory Response during Candida albicans Vaginitis". Infection and Immunity 82, nr 2 (11.11.2013): 532–43. http://dx.doi.org/10.1128/iai.01417-13.
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ABSTRACTVulvovaginal candidiasis, caused primarily byCandida albicans, presents significant health issues for women of childbearing age. As a polymorphic fungus, the ability ofC. albicansto switch between yeast and hyphal morphologies is considered its central virulence attribute. Armed with new criteria for defining vaginitis immunopathology, the purpose of this study was to determine whether the yeast-to-hypha transition is required for the hallmark inflammatory responses previously characterized during murine vaginitis. Kinetic analyses of vaginal infection withC. albicansin C57BL/6 mice demonstrated that fungal burdens remained constant throughout the observation period, while polymorphonuclear leukocyte (PMN), S100A8, and interleukin-1β levels obtained from vaginal lavage fluid increased by day 3 onward. Lactate dehydrogenase activity was also positively correlated with increased effectors of innate immunity. Additionally, immunodepletion of neutrophils in infected mice confirmed a nonprotective role for PMNs during vaginitis. Determination of the importance of fungal morphogenesis during vaginitis was addressed with a two-pronged approach. Intravaginal inoculation of mice withC. albicansstrains deleted for key transcriptional regulators (bcr1Δ/Δ,efg1Δ/Δ,cph1Δ/Δ, andefg1Δ/Δcph1Δ/Δ) controlling the yeast-to-hypha switch revealed a crucial role for morphogenetic signaling through the Efg1 and, to a lesser extent, the Bcr1 pathways in contributing to vaginitis immunopathology. Furthermore, overexpression of transcription factorsNRG1andUME6, to maintain yeast and hyphal morphologies, respectively, confirmed the importance of morphogenesis in generating innate immune responsesin vivo. These results highlight the yeast-to-hypha switch and the associated morphogenetic response as important virulence components for the immunopathogenesis ofCandidavaginitis, with implications for transition from benign colonization to symptomatic infection.
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Walther, A., i J. Wendland. "Polarized Hyphal Growth in Candida albicans Requires the Wiskott-Aldrich Syndrome Protein Homolog Wal1p". Eukaryotic Cell 3, nr 2 (kwiecień 2004): 471–82. http://dx.doi.org/10.1128/ec.3.2.471-482.2004.
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ABSTRACT The yeast-to-hypha transition is a key feature in the cell biology of the dimorphic human fungal pathogen Candida albicans. Reorganization of the actin cytoskeleton is required for this dimorphic switch in Candida. We show that C. albicans WAL1 mutants with both copies of the Wiskott-Aldrich syndrome protein (WASP) homolog deleted do not form hyphae under all inducing conditions tested. Growth of the wild-type and wal1 mutant strains was monitored by in vivo time-lapse microscopy both during yeast-like growth and under hypha-inducing conditions. Isotropic bud growth produced round wal1 cells and unusual mother cell growth. Defects in the organization of the actin cytoskeleton resulted in the random localization of actin patches. Furthermore, wal1 cells exhibited defects in the endocytosis of the lipophilic dye FM4-64, contained increased numbers of vacuoles compared to the wild type, and showed defects in bud site selection. Under hypha-inducing conditions wal1 cells were able to initiate polarized morphogenesis, which, however, resulted in the formation of pseudohyphal cells. Green fluorescent protein (GFP)-tagged Wal1p showed patch-like localization in emerging daughter cells during the yeast growth phase and at the hyphal tips under hypha-inducing conditions. Wal1p-GFP localization largely overlapped with that of actin. Our results demonstrate that Wal1p is required for the organization of the actin cytoskeleton and hyphal morphogenesis in C. albicans as well as for endocytosis and vacuole morphology.
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Boyce, Kylie J., i Alex Andrianopoulos. "Morphogenetic Circuitry Regulating Growth and Development in the Dimorphic Pathogen Penicillium marneffei". Eukaryotic Cell 12, nr 2 (30.11.2012): 154–60. http://dx.doi.org/10.1128/ec.00234-12.
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ABSTRACTPenicillium marneffeiis an emerging human-pathogenic fungus endemic to Southeast Asia. Like a number of other fungal pathogens,P. marneffeiexhibits temperature-dependent dimorphic growth and grows in two distinct cellular morphologies, hyphae at 25°C and yeast cells at 37°C. Hyphae can differentiate to produce the infectious agents, asexual spores (conidia), which are inhaled into the host lung, where they are phagocytosed by pulmonary alveolar macrophages. Within macrophages, conidia germinate into unicellular yeast cells, which divide by fission. This minireview focuses on the current understanding of the genes required for the morphogenetic control of conidial germination, hyphal growth, asexual development, and yeast morphogenesis inP. marneffei.
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Suryanarayanan, T. S., V. Muruganandam i G. Sampath. "Effect of Congo red on hyphal morphogenesis and sporulation of Botryodiplodia theobromae". Canadian Journal of Botany 65, nr 5 (1.05.1987): 815–16. http://dx.doi.org/10.1139/b87-110.
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The effect of Congo red, a dye which inhibits crystallization of cell wall polysaccharides, on hyphal differentiation and sporulation of Botryodiplodia theobromae Pat. was studied. The fungus has an obligate requirement for light to fruit in culture. The dye replaced the light requirement for formation of pycnidia. It also affected the structural integrity of the hyphal wall and the branching frequency of the hypha.
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Enjalbert, Brice, i Malcolm Whiteway. "Release from Quorum-Sensing Molecules Triggers Hyphal Formation during Candida albicans Resumption of Growth". Eukaryotic Cell 4, nr 7 (lipiec 2005): 1203–10. http://dx.doi.org/10.1128/ec.4.7.1203-1210.2005.
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ABSTRACT Candida albicans is a pathogenic fungus able to change morphology in response to variations in its growth environment. Simple inoculation of stationary cells into fresh medium at 37°C, without any other manipulations, appears to be a powerful but transient inducer of hyphal formation; this process also plays a significant role in classical serum induction of hyphal formation. The mechanism appears to involve the release of hyphal repression caused by quorum-sensing molecules in the growth medium of stationary-phase cells, and farnesol has a strong but incomplete role in this process. We used DNA microarray technology to study both the resumption of growth of Candida albicans cells and molecular regulation involving farnesol. Maintaining farnesol in the culture medium during the resumption of growth both delays and reduces the induction of hypha-related genes yet triggers expression of genes encoding drug efflux components. The persistence of farnesol also prevents the repression of histone genes during hyphal growth and affects the expression of putative or demonstrated morphogenesis-regulating cyclin genes, such as HGC1, CLN3, and PCL2. The results suggest a model explaining the triggering of hyphae in the host based on quorum-sensing molecules.
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Xu, Hongbin, Keith F. Chater, Zixin Deng i Meifeng Tao. "A Cellulose Synthase-Like Protein Involved in Hyphal Tip Growth and Morphological Differentiation in Streptomyces". Journal of Bacteriology 190, nr 14 (16.05.2008): 4971–78. http://dx.doi.org/10.1128/jb.01849-07.
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ABSTRACT Cellulose synthase and cellulose synthase-like proteins, responsible for synthesizing β-glucan-containing polysaccharides, play a fundamental role in cellular architectures, such as plant cell and tissue morphogenesis, bacterial biofilm formation, and fruiting-body development. However, the roles of the proteins involved in the developmental process are not well understood. Here, we report that a cellulose synthase-like protein (CslASc) in Streptomyces has a function in hyphal tip growth and morphological differentiation. The cslASc replacement mutant showed pleiotropic defects, including the severe delay of aerial-hyphal formation and altered cell wall morphology. Calcofluor white fluorescence analysis demonstrated that polysaccharide synthesis at hyphal tips was dependent on CslASc. cslASc was constitutively transcribed, and an enhanced green fluorescent protein-CslASc fusion protein was mostly located at the hyphal tips. An extract enriched in morphogenetic chaplin proteins promoted formation of aerial hyphae by the mutant. Furthermore, a two-hybrid experiment indicated that the glycosyltransferase domain of CslASc interacted with the tropomyosin-like polarity-determining DivIVA protein, suggesting that the tip-located DivIVA governed tip recruitment of the CslASc membrane protein. These results imply that the cellulose synthase-like protein couples extracellular and cytoskeletal components functioning in tip growth and cell development.
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Bockmühl, Dirk P., i Joachim F. Ernst. "A Potential Phosphorylation Site for an A-Type Kinase in the Efg1 Regulator Protein Contributes to Hyphal Morphogenesis of Candida albicans". Genetics 157, nr 4 (1.04.2001): 1523–30. http://dx.doi.org/10.1093/genetics/157.4.1523.
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Abstract Efg1p in the human fungal pathogen Candida albicans is a member of the conserved APSES class of proteins regulating morphogenetic processes in fungi. We have analyzed the importance for hyphal morphogenesis of a putative phosphorylation site for protein kinase A (PKA), threonine-206, within an Efg1p domain highly conserved among APSES proteins. Alanine substitution of T206, but not of the adjacent T207 and T208 residues, led to a block of hypha formation on solid and in liquid media, while a T206E exchange caused hyperfilamentation. The extent of the morphogenetic defect caused by the T206A mutation depended on hypha-induction conditions. Extragenous suppression of mutations in signaling components, including tpk2 and cek1 mutations, was achieved by wild-type- and T206E-, but not by the T206A-variant-encoding allele of EFG1. All muteins tested were produced at equal levels and at high production levels supported pseudohyphal formation. The results are consistent with a role of Efg1p as a central downstream component of a PKA-signaling pathway including Tpk2p or other PKA isoforms. Threonine-206 of Efg1p is essential as a putative phosphorylation target to promote hyphal induction by a subset of environmental cues.
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Chapa y Lazo, Bernardo, Steven Bates i Peter Sudbery. "The G1 Cyclin Cln3 Regulates Morphogenesis in Candida albicans". Eukaryotic Cell 4, nr 1 (styczeń 2005): 90–94. http://dx.doi.org/10.1128/ec.4.1.90-94.2005.
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ABSTRACT In Saccharomyces cerevisiae, the G1 cyclin Cln3 initiates the Start of a mitotic cell cycle in response to size and nutrient inputs. Loss of Cln3 delays but does not prevent Start, due to the eventual Cln3-independent transcription of CLN1 and CLN2. When unbudded cells of the human pathogen Candida albicans were depleted of the G1 cyclin Cln3 they increased in size but did not bud. Thus, unlike S. cerevisiae, Cln3 is essential for budding in C. albicans. However, eventually the large unbudded cells spontaneously produced filamentous forms. The morphology was growth medium dependent; on nutritionally poor medium the polarized outgrowths fulfilled the formal criteria for true hyphae. This state is stable, and continued growth leads to a hyphal mycelium, which invades the agar substratum. Interestingly, it is also required for normal hyphal development, as Cln3-depleted cells develop morphological abnormalities if challenged with hyphal inducing signals such as serum or neutral pH. Taken together, these results show that, in C. albicans, Cln3 has assumed a critical role in coordinating mitotic cell division with differentiation.
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Jung, Won Hee, i Lubomira I. Stateva. "The cAMP phosphodiesterase encoded by CaPDE2 is required for hyphal development in Candida albicans". Microbiology 149, nr 10 (1.10.2003): 2961–76. http://dx.doi.org/10.1099/mic.0.26517-0.
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The cAMP-dependent pathway, which regulates yeast-to-hypha morphogenesis in Candida albicans, is controlled by changes in cAMP levels determined by the processes of synthesis and hydrolysis. Both low- and high-affinity cAMP phosphodiesterases are encoded in the C. albicans genome. CaPDE2, encoding the high-affinity cAMP phosphodiesterase, has been cloned and shown to be toxic in Saccharomyces cerevisiae upon overexpression under pGAL1, but functional under the moderate pMET3. Deletion of CaPDE2 causes elevated cAMP levels and responsiveness to exogenous cAMP, higher sensitivity to heat shock, severe growth defects at 42 °C and highly reduced levels of EFG1 transcription. In vitro in hypha-inducing liquid medium CaPDE2, deletion prohibits normal hyphal, but not pseudohyphal growth. On solid medium capde2 mutants form aberrant hyphae, with fewer branches and almost no lateral buds, which are deficient in hypha-to-yeast reversion. The phenotypic defects of capde2 mutants show that the cAMP-dependent pathway plays specific roles in hyphal and pseudohyphal development, its regulatory role however, being greater in liquid than on solid medium in vitro. The increased expression of CaPDE2 after serum addition correlates well with a drop in cAMP levels following the initial rise in response to the hyphal inducer. These results suggest that Capde2p mediates a desensitization mechanism by lowering basal cAMP levels in response to environmental stimuli in C. albicans.
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Laundon, Davis, Nathan Chrismas, Glen Wheeler i Michael Cunliffe. "Chytrid rhizoid morphogenesis resembles hyphal development in multicellular fungi and is adaptive to resource availability". Proceedings of the Royal Society B: Biological Sciences 287, nr 1928 (10.06.2020): 20200433. http://dx.doi.org/10.1098/rspb.2020.0433.
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Key to the ecological prominence of fungi is their distinctive cell biology, our understanding of which has been principally based on dikaryan hyphal and yeast forms. The early-diverging Chytridiomycota (chytrids) are ecologically important and a significant component of fungal diversity, yet their cell biology remains poorly understood. Unlike dikaryan hyphae, chytrids typically attach to substrates and feed osmotrophically via anucleate rhizoids. The evolution of fungal hyphae appears to have occurred from rhizoid-bearing lineages and it has been hypothesized that a rhizoid-like structure was the precursor to multicellular hyphae. Here, we show in a unicellular chytrid, Rhizoclosmatium globosum , that rhizoid development exhibits striking similarities with dikaryan hyphae and is adaptive to resource availability. Rhizoid morphogenesis exhibits analogous patterns to hyphal growth and is controlled by β-glucan-dependent cell wall synthesis and actin polymerization. Chytrid rhizoids growing from individual cells also demonstrate adaptive morphological plasticity in response to resource availability, developing a searching phenotype when carbon starved and spatial differentiation when interacting with particulate organic matter. We demonstrate that the adaptive cell biology and associated developmental plasticity considered characteristic of hyphal fungi are shared more widely across the Kingdom Fungi and therefore could be conserved from their most recent common ancestor.
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Bauer, Yasmina, Philipp Knechtle, Jürgen Wendland, Hanspeter Helfer i Peter Philippsen. "A Ras-like GTPase Is Involved in Hyphal Growth Guidance in the Filamentous Fungus Ashbya gossypii". Molecular Biology of the Cell 15, nr 10 (październik 2004): 4622–32. http://dx.doi.org/10.1091/mbc.e04-02-0104.
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Characteristic features of morphogenesis in filamentous fungi are sustained polar growth at tips of hyphae and frequent initiation of novel growth sites (branches) along the extending hyphae. We have begun to study regulation of this process on the molecular level by using the model fungus Ashbya gossypii. We found that the A. gossypii Ras-like GTPase Rsr1p/Bud1p localizes to the tip region and that it is involved in apical polarization of the actin cytoskeleton, a determinant of growth direction. In the absence of RSR1/BUD1, hyphal growth was severely slowed down due to frequent phases of pausing of growth at the hyphal tip. During pausing events a hyphal tip marker, encoded by the polarisome component AgSPA2, disappeared from the tip as was shown by in vivo time-lapse fluorescence microscopy of green fluorescent protein-labeled AgSpa2p. Reoccurrence of AgSpa2p was required for the resumption of hyphal growth. In the Agrsr1/bud1Δ deletion mutant, resumption of growth occurred at the hyphal tip in a frequently uncoordinated manner to the previous axis of polarity. Additionally, hyphal filaments in the mutant developed aberrant branching sites by mislocalizing AgSpa2p thus distorting hyphal morphology. These results define AgRsr1p/Bud1p as a key regulator of hyphal growth guidance.
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Fuchs, Uta, Isabel Manns i Gero Steinberg. "Microtubules Are Dispensable for the Initial Pathogenic Development but Required for Long-Distance Hyphal Growth in the Corn Smut FungusUstilago maydis". Molecular Biology of the Cell 16, nr 6 (czerwiec 2005): 2746–58. http://dx.doi.org/10.1091/mbc.e05-03-0176.
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Fungal pathogenicity often involves a yeast-to-hypha transition, but the structural basis for this dimorphism is largely unknown. Here we analyze the role of the cytoskeleton in early steps of pathogenic development in the corn pathogen Ustilago maydis. On the plant yeast-like cells recognize each other, undergo a cell cycle arrest, and form long conjugation hyphae, which fuse and give rise to infectious filaments. F-actin is essential for polarized growth at all these stages and for cell-cell fusion. Furthermore, F-actin participates in pheromone secretion, but not perception. Although U. maydis contains prominent tubulin arrays, microtubules are neither required for cell-cell recognition, nor for cell-cell fusion, and have only minor roles in morphogenesis of yeast-like cells. Without microtubules hyphae are formed, albeit at 60% reduced elongation rates, but they reach only ∼50 μm in length and the nucleus fails to migrate into the hypha. A similar phenotype is found in dynein mutants that have a nuclear migration defect and stop hyphal elongation at ∼50 μm. These results demonstrate that microtubules are dispensable for polarized growth during morphological transition, but become essential in long-distance hyphal growth, which is probably due to their role in nuclear migration.
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Warenda, Amy J., i James B. Konopka. "Septin Function inCandida albicansMorphogenesis". Molecular Biology of the Cell 13, nr 8 (sierpień 2002): 2732–46. http://dx.doi.org/10.1091/mbc.e02-01-0013.
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The septin proteins function in the formation of septa, mating projections, and spores in Saccharomyces cerevisiae, as well as in cell division and other processes in animal cells. Candida albicans septins were examined in this study for their roles in morphogenesis of this multimorphic, opportunistically pathogenic fungus, which can range from round budding yeast to elongated hyphae. C. albicans green fluorescent protein labeled septin proteins localized to a tight ring at the bud and pseudohyphae necks and as a more diffuse array in emerging germ tubes of hyphae. Deletion analysis demonstrated that the C. albicans homologs of the S. cerevisiae CDC3 andCDC12 septins are essential for viability. In contrast, the C. albicans cdc10Δ and cdc11Δ mutants were viable but displayed conditional defects in cytokinesis, localization of cell wall chitin, and bud morphology. The mutant phenotypes were not identical, however, indicating that these septins carry out distinct functions. The viable septin mutants could be stimulated to undergo hyphal morphogenesis but formed hyphae with abnormal curvature, and they differed from wild type in the selection of sites for subsequent rounds of hyphal formation. Thecdc11Δ mutants were also defective for invasive growth when embedded in agar. These results further extend the known roles of the septins by demonstrating that they are essential for the proper morphogenesis of C. albicans during both budding and filamentous growth.
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Richard, Mathias, Raymundo Rosas Quijano, Samira Bezzate, Florence Bordon-Pallier i Claude Gaillardin. "Tagging Morphogenetic Genes by Insertional Mutagenesis in the Yeast Yarrowia lipolytica". Journal of Bacteriology 183, nr 10 (15.05.2001): 3098–107. http://dx.doi.org/10.1128/jb.183.10.3098-3107.2001.
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ABSTRACT The yeast Yarrowia lipolytica is distantly related to Saccharomyces cerevisiae, can be genetically modified, and can grow in both haploid and diploid states in either yeast, pseudomycelial, or mycelial forms, depending on environmental conditions. Previous results have indicated that the STEand RIM pathways, which mediate cellular switching in other dimorphic yeasts, are not required for Y. lipolytica morphogenesis. To identify the pathways involved in morphogenesis, we mutagenized a wild-type strain of Y. lipolytica with a Tn3 derivative. We isolated eight tagged mutants, entirely defective in hyphal formation, from a total of 40,000 mutants and identified seven genes homologous toS. cerevisiae CDC25, RAS2, BUD6, KEX2, GPI7, SNF5, andPPH21. We analyzed their abilities to invade agar and to form pseudomycelium or hyphae under inducing conditions and their sensitivity to temperature and to Calcofluor white. Chitin staining was used to detect defects in their cell walls. Our results indicate that a functional Ras-cyclic AMP pathway is required for the formation of hyphae in Y. lipolytica and that perturbations in the processing of extracellular, possibly parietal, proteins result in morphogenetic defects.
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González-Novo, Alberto, Jaime Correa-Bordes, Leticia Labrador, Miguel Sánchez, Carlos R. Vázquez de Aldana i Javier Jiménez. "Sep7 Is Essential to Modify Septin Ring Dynamics and Inhibit Cell Separation during Candida albicans Hyphal Growth". Molecular Biology of the Cell 19, nr 4 (kwiecień 2008): 1509–18. http://dx.doi.org/10.1091/mbc.e07-09-0876.
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When Candida albicans yeast cells receive the appropriate stimulus, they switch to hyphal growth, characterized by continuous apical elongation and the inhibition of cell separation. The molecular basis of this inhibition is poorly known, despite its crucial importance for hyphal development. In C. albicans, septins are important for hypha formation and virulence. Here, we used fluorescence recovery after photobleaching analysis to characterize the dynamics of septin rings during yeast and hyphal growth. On hyphal induction, septin rings are converted to a hyphal-specific state, characterized by the presence of a frozen core formed by Sep7/Shs1, Cdc3 and Cdc12, whereas Cdc10 is highly dynamic and oscillates between the ring and the cytoplasm. Conversion of septin rings to the hyphal-specific state inhibits the translocation of Cdc14 phosphatase, which controls cell separation, to the hyphal septum. Modification of septin ring dynamics during hyphal growth is dependent on Sep7 and the hyphal-specific cyclin Hgc1, which partially controls Sep7 phosphorylation status and protein levels. Our results reveal a link between the cell cycle machinery and septin cytoskeleton dynamics, which inhibits cell separation in the filaments and is essential for hyphal morphogenesis.
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Krishnamurthy, Shankarling, Armêl Plaine, Juliane Albert, Tulika Prasad, Rajendra Prasad i Joachim F. Ernst. "Dosage-dependent functions of fatty acid desaturase Ole1p in growth and morphogenesis of Candida albicans". Microbiology 150, nr 6 (1.06.2004): 1991–2003. http://dx.doi.org/10.1099/mic.0.27029-0.
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Conditions in the infected human host trigger virulence attributes of the fungal pathogen Candida albicans. Specific inducers and elevated temperatures lead to hyphal development or regulate chlamydospore development. To explore if these processes are affected by membrane lipids, an investigation of the functions of the Ole1 fatty acid desaturase (stearoyl-CoA desaturase) in C. albicans, which synthesizes oleic acid, was undertaken. A conditional strain expressing OLE1 from the regulatable MET3 promoter was unable to grow in repressing conditions, indicating that OLE1 is an essential gene. In contrast, a mutant lacking both alleles of OLE2, encoding a Ole1p homologue, was viable and had no apparent phenotypes. Partial repression of MET3p–OLE1 slightly lowered oleic acid levels and decreased membrane fluidity; these conditions permitted growth in the yeast form, but prevented hyphal development in aerobic conditions and blocked the formation of chlamydospores. In contrast, in hypoxic conditions, which trigger an alternative morphogenetic pathway, hyphal morphogenesis was unaffected. Because aerobic morphogenetic signalling and oleic acid biosynthesis require oxygen, it is proposed that oleic acid may function as a sensor activating specific morphogenetic pathways in normoxic conditions.
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Bauer, Janine, i Jürgen Wendland. "Candida albicans Sfl1 Suppresses Flocculation and Filamentation". Eukaryotic Cell 6, nr 10 (31.08.2007): 1736–44. http://dx.doi.org/10.1128/ec.00236-07.
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ABSTRACT Hyphal morphogenesis in Candida albicans is regulated by multiple pathways which act by either inducing or repressing filamentation. Most notably, Tup1, Nrg1, and Rfg1 are transcriptional repressors, while Efg1, Flo8, Cph1, and Czf1 can induce filamentation. Here, we present the functional analysis of CaSFL1, which encodes the C. albicans homolog of the Saccharomyces cerevisiae SFL1 (suppressor of flocculation) gene. Deletion of CaSFL1 results in flocculation (i.e., the formation of clumps) of yeast cells, which is most pronounced in minimal medium. The flocs contained hyphae already under noninducing conditions, and filamentation could be enhanced with hypha-inducing cues at 37°C. Expression of SFL1 in a heterozygous mutant under the control of the CaMET3 promoter was shown to complement these defects and allowed switching between wild-type and mutant phenotypes. Interestingly, increased expression of SFL1 using a MET3prom-SFL1 construct prior to the induction of filamentation completely blocked germ tube formation. To localize Sfl1 in vivo, we generated a SFL1-GFP fusion. Sfl1-green fluorescent protein was found in the nucleus in both yeast cells and, to a lesser extent, hyphal cells. Using reverse transcription-PCR, we find an increased expression of ALS1, ALS3, HWP1, ECE1, and also FLO8. Our results suggest that Sfl1 functions in the repression of flocculation and filamentation and thus represents a novel negative regulator of C. albicans morphogenesis.
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Martin, Stephen W., Lois M. Douglas i James B. Konopka. "Cell Cycle Dynamics and Quorum Sensing in Candida albicans Chlamydospores Are Distinct from Budding and Hyphal Growth". Eukaryotic Cell 4, nr 7 (lipiec 2005): 1191–202. http://dx.doi.org/10.1128/ec.4.7.1191-1202.2005.
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ABSTRACT The regulation of morphogenesis in the human fungal pathogen Candida albicans is under investigation to better understand how the switch between budding and hyphal growth is linked to virulence. Therefore, in this study we examined the ability of C. albicans to undergo a distinct type of morphogenesis to form large thick-walled chlamydospores whose role in infection is unclear, but they act as a resting form in other species. During chlamydospore morphogenesis, cells switch to filamentous growth and then develop elongated suspensor cells that give rise to chlamydospores. These filamentous cells were distinct from true hyphae in that they were wider and were not inhibited by the quorum-sensing factor farnesol. Instead, farnesol increased chlamydospore production, indicating that quorum sensing can also have a positive role. Nuclear division did not occur across the necks of chlamydospores, as it does in budding. Interestingly, nuclei divided within the suspensor cells, and then one daughter nucleus subsequently migrated into the chlamydospore. Septins were not detected near mitotic nuclei but were localized at chlamydospore necks. At later stages, septins localized throughout the chlamydospore plasma membrane and appeared to form long filamentous structures. Deletion of the CDC10 or CDC11 septins caused greater curvature of cells growing in a filamentous manner and morphological defects in suspensor cells and chlamydospores. These studies identify aspects of chlamydospore morphogenesis that are distinct from bud and hyphal morphogenesis.
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Finley, Kenneth R., i Judith Berman. "Microtubules in Candida albicans Hyphae Drive Nuclear Dynamics and Connect Cell Cycle Progression to Morphogenesis". Eukaryotic Cell 4, nr 10 (październik 2005): 1697–711. http://dx.doi.org/10.1128/ec.4.10.1697-1711.2005.
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ABSTRACT Candida albicans is an opportunistic fungal pathogen whose virulence is related to its ability to switch between yeast, pseudohyphal, and true-hyphal morphologies. To ask how long-distance nuclear migration occurs in C. albicans hyphae, we identified the fundamental properties of nuclear movements and microtubule dynamics using time-lapse microscopy. In hyphae, nuclei migrate to, and divide across, the presumptive site of septation, which forms 10 to 15 μm distal to the basal cell. The mother nucleus returns to the basal cell, while the daughter nucleus reiterates the process. We used time-lapse microscopy to identify the mechanisms by which C. albicans nuclei move over long distances and are coordinated with hyphal morphology. We followed nuclear migration and spindle dynamics, as well as the time and position of septum specification, defined it as the presumptum, and established a chronology of nuclear, spindle, and morphological events. Analysis of microtubule dynamics revealed that premitotic forward nuclear migration is due to the repetitive sliding of astral microtubules along the cell cortex but that postmitotic forward and reverse nuclear migrations are due primarily to spindle elongation. Free microtubules exhibit cell cycle regulation; they are present during interphase and disappear at the time of spindle assembly. Finally, a growth defect in strains expressing Tub2-green fluorescent protein revealed a connection between hyphal elongation and the nuclear cell cycle that is coordinated by hyphal length and/or volume.
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Cánovas, David, Kylie J. Boyce i Alex Andrianopoulos. "The Fungal Type II Myosin in Penicillium marneffei, MyoB, Is Essential for Chitin Deposition at Nascent Septation Sites but Not Actin Localization". Eukaryotic Cell 10, nr 3 (3.12.2010): 302–12. http://dx.doi.org/10.1128/ec.00201-10.
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ABSTRACTCytokinesis is essential for proliferative growth but also plays equally important roles during morphogenesis and development. The human pathogenPenicillium marneffeiis capable of dimorphic switching in response to temperature, growing in a multicellular filamentous hyphal form at 25°C and in a unicellular yeast form at 37°C.P. marneffeialso undergoes asexual development at 25°C to produce multicellular differentiated conidiophores. Thus,P. marneffei exhibits cell division with and without cytokinesis and division by budding and fission, depending on the cell type. The type II myosin gene,myoB, fromP. marneffeiplays important roles in the morphogenesis of these cell types. Deletion ofmyoBleads to chitin deposition defects at sites of cell division without perturbing actin localization. In addition to aberrant hyphal cells, distinct conidiophore cell types are lacking due to malformed septa and nuclear division defects. At 37°C, deletion ofmyoBprevents uninucleate yeast cell formation, instead producing long filaments resembling hyphae at 25°C. The ΔmyoBcells also often lyse due to defects in cell wall biogenesis. Thus, MyoB is essential for correct morphogenesis of all cell types regardless of division mode (budding or fission) and defines differences between the different types of growth.
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Schmitz, Hans-Peter, Andreas Kaufmann, Michael Köhli, Pierre Philippe Laissue i Peter Philippsen. "From Function to Shape: A Novel Role of a Formin in Morphogenesis of the Fungus Ashbya gossypii". Molecular Biology of the Cell 17, nr 1 (styczeń 2006): 130–45. http://dx.doi.org/10.1091/mbc.e05-06-0479.
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Morphogenesis of filamentous ascomycetes includes continuously elongating hyphae, frequently emerging lateral branches, and, under certain circumstances, symmetrically dividing hyphal tips. We identified the formin AgBni1p of the model fungus Ashbya gossypii as an essential factor in these processes. AgBni1p is an essential protein apparently lacking functional overlaps with the two additional A. gossypii formins that are nonessential. Agbni1 null mutants fail to develop hyphae and instead expand to potato-shaped giant cells, which lack actin cables and thus tip-directed transport of secretory vesicles. Consistent with the essential role in hyphal development, AgBni1p locates to tips, but not to septa. The presence of a diaphanous autoregulatory domain (DAD) indicates that the activation of AgBni1p depends on Rho-type GTPases. Deletion of this domain, which should render AgBni1p constitutively active, completely changes the branching pattern of young hyphae. New axes of polarity are no longer established subapically (lateral branching) but by symmetric divisions of hyphal tips (tip splitting). In wild-type hyphae, tip splitting is induced much later and only at much higher elongation speed. When GTP-locked Rho-type GTPases were tested, only the young hyphae with mutated AgCdc42p split at their tips, similar to the DAD deletion mutant. Two-hybrid experiments confirmed that AgBni1p interacts with GTP-bound AgCdc42p. These data suggest a pathway for transforming one axis into two new axes of polar growth, in which an increased activation of AgBni1p by a pulse of activated AgCdc42p stimulates additional actin cable formation and tip-directed vesicle transport, thus enlarging and ultimately splitting the polarity site.
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Gutiérrez-Escribano, Pilar, Alberto González-Novo, M. Belén Suárez, Chang-Run Li, Yue Wang, Carlos R. Vázquez de Aldana i Jaime Correa-Bordes. "CDK-dependent phosphorylation of Mob2 is essential for hyphal development in Candida albicans". Molecular Biology of the Cell 22, nr 14 (15.07.2011): 2458–69. http://dx.doi.org/10.1091/mbc.e11-03-0205.
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Nuclear Dbf2-related (NDR) protein kinases are essential components of regulatory pathways involved in cell morphogenesis, cell cycle control, and viability in eukaryotic cells. For their activity and function, these kinases require interaction with Mob proteins. However, little is known about how the Mob proteins are regulated. In Candida albicans, the cyclin-dependent kinase (CDK) Cdc28 and the NDR kinase Cbk1 are required for hyphal growth. Here we demonstrate that Mob2, the Cbk1 activator, undergoes a Cdc28-dependent differential phosphorylation on hyphal induction. Mutations in the four CDK consensus sites in Mob2 to Ala significantly impaired hyphal development. The mutant cells produced short hyphae with enlarged tips that displayed an illicit activation of cell separation. We also show that Cdc28 phosphorylation of Mob2 is essential for the maintenance of polarisome components at hyphal tips but not at bud tips during yeast growth. Thus we have found a novel signaling pathway by which Cdc28 controls Cbk1 through the regulatory phosphorylation of Mob2, which is crucial for normal hyphal development.
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Kamilla, L., S. M. Mansor, S. Ramanathan i S. Sasidharan. "Effects of Clitoria ternatea Leaf Extract on Growth and Morphogenesis of Aspergillus niger". Microscopy and Microanalysis 15, nr 4 (3.07.2009): 366–72. http://dx.doi.org/10.1017/s1431927609090783.
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AbstractClitoria ternatea is known for its antimicrobial activity but the antifungal effects of leaf extract on growth and morphogenesis of Aspergillus niger have not been observed. The extract showed a favorable antifungal activity against A. niger with a minimum inhibition concentration 0.8 mg/mL and minimum fungicidal concentration 1.6 mg/mL, respectively. The leaf extract exhibited considerable antifungal activity against filamentous fungi in a dose-dependent manner with 0.4 mg/mL IC50 value on hyphal growth of A. niger. The main changes observed under scanning electron microscopy after C. ternatea extract treatment were loss of cytoplasm in fungal hyphae and the hyphal wall and its diameter became markedly thinner, distorted, and resulted in cell wall disruption. In addition, conidiophore alterations were also observed when A. niger was treated with C. ternatea leaf extract.
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Fortwendel, Jarrod R., Praveen R. Juvvadi, Luise E. Rogg, Yohannes G. Asfaw, Kimberlie A. Burns, Scott H. Randell i William J. Steinbach. "Plasma Membrane Localization Is Required for RasA-Mediated Polarized Morphogenesis and Virulence of Aspergillus fumigatus". Eukaryotic Cell 11, nr 8 (4.05.2012): 966–77. http://dx.doi.org/10.1128/ec.00091-12.
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ABSTRACT Ras is a highly conserved GTPase protein that is essential for proper polarized morphogenesis of filamentous fungi. Localization of Ras proteins to the plasma membrane and endomembranes through posttranslational addition of farnesyl and palmitoyl residues is an important mechanism through which cells provide specificity to Ras signal output. Although the Aspergillus fumigatus RasA protein is known to be a major regulator of growth and development, the membrane distribution of RasA during polarized morphogenesis and the role of properly localized Ras signaling in virulence of a pathogenic mold remain unknown. Here we demonstrate that Aspergillus fumigatus RasA localizes primarily to the plasma membrane of actively growing hyphae. We show that treatment with the palmitoylation inhibitor 2-bromopalmitate disrupts normal RasA plasma membrane association and decreases hyphal growth. Targeted mutations of the highly conserved RasA palmitoylation motif also mislocalized RasA from the plasma membrane and led to severe hyphal abnormalities, cell wall structural changes, and reduced virulence in murine invasive aspergillosis. Finally, we provide evidence that proper RasA localization is independent of the Ras palmitoyltransferase homolog, encoded by erfB , but requires the palmitoyltransferase complex subunit, encoded by erfD . Our results demonstrate that plasma membrane-associated RasA is critical for polarized morphogenesis, cell wall stability, and virulence in A. fumigatus .
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Seiler, Stephan, i Michael Plamann. "The Genetic Basis of Cellular Morphogenesis in the Filamentous FungusNeurospora crassa". Molecular Biology of the Cell 14, nr 11 (listopad 2003): 4352–64. http://dx.doi.org/10.1091/mbc.e02-07-0433.
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Cellular polarity is a fundamental property of every cell. Due to their extremely fast growth rate (≥1 μm/s) and their highly elongated form, filamentous fungi represent a prime example of polarized growth and are an attractive model for the analysis of fundamental mechanisms underlying cellular polarity. To identify the critical components that contribute to polarized growth, we developed a large-scale genetic screen for the isolation of conditional mutants defective in this process in the model fungus Neurospora crassa. Phenotypic analysis and complementation tests of ca. 950 mutants identified more than 100 complementation groups that define 21 distinct morphological classes. The phenotypes include polarity defects over the whole hypha, more specific defects localized to hyphal tips or subapical regions, and defects in branch formation and growth directionality. To begin converting this mutant collection into meaningful biological information, we identified the defective genes in 45 mutants covering all phenotypic classes. These genes encode novel proteins as well as proteins which 1) regulate the actin or microtubule cytoskeleton, 2) are kinases or components of signal transduction pathways, 3) are part of the secretory pathway, or 4) have functions in cell wall formation or membrane biosynthesis. These findings highlight the dynamic nature of a fungal hypha and establish a molecular model for studies of hyphal growth and polarity.
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Wu, Qindong, Tanya M. Sandrock, B. Gillian Turgeon, Olen C. Yoder, Stefan G. Wirsel i James R. Aist. "A Fungal Kinesin Required for Organelle Motility, Hyphal Growth, and Morphogenesis". Molecular Biology of the Cell 9, nr 1 (styczeń 1998): 89–101. http://dx.doi.org/10.1091/mbc.9.1.89.
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A gene (NhKIN1) encoding a kinesin was cloned fromNectria haematococca genomic DNA by polymerase chain reaction amplification, using primers corresponding to conserved regions of known kinesin-encoding genes. Sequence analysis showed thatNhKIN1 belongs to the subfamily of conventional kinesins and is distinct from any of the currently designated kinesin-related protein subfamilies. Deletion of NhKIN1 by transformation-mediated homologous recombination caused several dramatic phenotypes: a 50% reduction in colony growth rate, helical or wavy hyphae with reduced diameter, and subcellular abnormalities including withdrawal of mitochondria from the growing hyphal apex and reduction in the size of the Spitzenkörper, an apical aggregate of secretory vesicles. The effects on mitochondria and Spitzenkörper were not due to altered microtubule distribution, as microtubules were abundant throughout the length of hyphal tip cells of the mutant. The rate of spindle elongation during anaphase B of mitosis was reduced 11%, but the rate was not significantly different from that of wild type. This lack of a substantial mitotic phenotype is consistent with the primary role of the conventional kinesins in organelle motility rather than mitosis. Our results provide further evidence that the microtubule-based motility mechanism has a direct role in apical transport of secretory vesicles and the first evidence for its role in apical transport of mitochondria in a filamentous fungus. They also include a unique demonstration that a microtubule-based motor protein is essential for normal positioning of the Spitzenkörper, thus providing a new insight into the cellular basis for the aberrant hyphal morphology.
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Diéguez-Uribeondo, Javier, Gerhard Gierz i Salomon Bartnicki-Garcı́a. "Image analysis of hyphal morphogenesis in Saprolegniaceae (Oomycetes)". Fungal Genetics and Biology 41, nr 3 (marzec 2004): 293–307. http://dx.doi.org/10.1016/j.fgb.2003.10.012.
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Li, Yandong, Chang Su, Xuming Mao, Fang Cao i Jiangye Chen. "Roles of Candida albicans Sfl1 in Hyphal Development". Eukaryotic Cell 6, nr 11 (22.08.2007): 2112–21. http://dx.doi.org/10.1128/ec.00199-07.
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ABSTRACT The ability to switch between different morphological forms is an important feature of Candida albicans and is relevant to its pathogenesis. Many conserved positive and negative transcription factors are involved in morphogenetic regulation of the two dimorphic fungi Candida albicans and Saccharomyces cerevisiae. In S. cerevisiae, the transcriptional repressor Sfl1 and the activator Flo8 function antagonistically in invasive and filamentous growth. We have previously reported that Candida albicans Flo8 is a transcription factor essential for hyphal development and virulence in C. albicans. To determine whether a similar negative factor exists in C. albicans, we identified Candida albicans Sfl1 as a functional homolog of the S. cerevisiae sfl1 mutant. Sfl1 is a negative regulator of hyphal development in C. albicans. Deletion of C. albicans SFL1 enhanced filamentous growth and hypha-specific gene expression in several media and at several growth temperatures. Overexpression of the SFL1 led to a significant reduction of filament formation. Both deletion and overexpression of the SFL1 attenuated virulence of C. albicans in a mouse model. Deleting FLO8 in an sfl1/sfl1 mutant completely blocked hyphal development in various growth conditions examined, suggesting that C. albicans Sfl1 may act as a negative regulator of filamentous growth by antagonizing Flo8 functions. We suggest that, similar to the case for S. cerevisiae, a combination of dual control by activation and repression of Flo8 and Sfl1 may contribute to the fine regulatory network in C. albicans morphogenesis responding to different environmental cues.
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Gow, N. A. R., B. Hube, D. A. Bailey, D. A. Schofield, C. Munro, R. K. Swoboda, G. Bertram i in. "Genes associated with dimorphism and virulence of Candida albicans". Canadian Journal of Botany 73, S1 (31.12.1995): 335–42. http://dx.doi.org/10.1139/b95-264.
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Strategies for the analysis of a range of Candida albicans genes, whose expression is regulated during the yeast to hyphal transition (dimorphism), including genes encoding putative virulence factors, are reviewed. To help discriminate among genes whose products were the cause or consequence of dimorphism, temporal changes in the levels of the mRNAs of these and other genes were examined by northern analysis. The mRNA levels of most genes that were examined increased or decreased, transiently or persistently indicating complex alterations in gene expression during morphogenesis. Genes encoding four glycolytic enzymes were regulated transcriptionally during dimorphism but control experiments indicated no direct correlation with germ tube formation. Two chitin synthase genes (CHS2 and CHS3) and three aspartyl proteinase genes (SAP4–SAP6) were transcribed preferentially in the hyphal form, but in these cases hypha-specific expression was shown to be strain dependent or medium dependent, respectively. A gene, HYR1 (for hyphal regulation), was isolated and found to exhibit strict hypha-specific expression in a range of strains under a range of culture conditions. The ura-blaster protocol was used to generate disruptions in CHS2, CHS1, and HSP90 (for heat-shock protein). The homozygous CHS2 disruption did not affect the kinetics of germ-tube formation markedly but resulted in hyphae with a reduced chitin content. In contrast, homozygous null mutations in CHS1 and HSP90 were apparently lethal because no homozygous null strains were isolated after integrative transformation of heterozygous mutants. The analysis of candidate genes for dimorphism and virulence of C. albicans through northern analysis and gene disruption should facilitate an understanding of these processes at the molecular level. Key words: Candida, dimorphism, gene regulation, virulence.
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Harris, Steven D., Amy F. Hofmann, Hugo W. Tedford i Maurice P. Lee. "Identification and Characterization of Genes Required for Hyphal Morphogenesis in the Filamentous Fungus Aspergillus nidulans". Genetics 151, nr 3 (1.03.1999): 1015–25. http://dx.doi.org/10.1093/genetics/151.3.1015.
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Abstract In the filamentous fungus Aspergillus nidulans, germination of an asexual conidiospore results in the formation of a hyphal cell. A key feature of spore germination is the switch from isotropic spore expansion to polarized apical growth. Here, temperature-sensitive mutations are used to characterize the roles of five genes (sepA, hypA, podB-podD) in the establishment and maintenance of hyphal polarity. Evidence that suggests that the hypA, podB, and sepA genes are required for multiple aspects of hyphal morphogenesis is presented. Notably, podB and sepA are needed for organization of the cytoskeleton at sites of polarized growth. In contrast, podC and podD encode proteins that appear to be specifically required for the establishment of hyphal polarity during spore germination. The role of sepA and the pod genes in controlling the spatial pattern of polarized morphogenesis in germinating spores is also described. Results obtained from these experiments indicate that the normal pattern of germ-tube emergence is dependent upon the integrity of the actin cytoskeleton.
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Nadeem, Sayyada Ghufrana, i Aiman Pirzada. "Nutritional and environmental factors affecting the morphogenesis of Candida albicans: A key to virulence". Brazilian Journal of Biological Sciences 5, nr 10 (2018): 311–27. http://dx.doi.org/10.21472/bjbs.051011.
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Candida albicans is an opportunistic fungal pathogen that plays an important role in the early part of infectious process by extravagating and disseminating to the target organs, whereas hyphal forms appear to be required for the mortality resulting from a deep-seated infection. C. albicans morphogenesis is regulated by numerous environmental cues and other signaling pathways. We investigated the morphogenesis in C. albicans in the presence of serum at different temperatures (20 oC, 30 oC and 37 oC). C. albicans were also grown in simple growth medium 'SDB' and subsequently cultured from Fetal bovine serum and Soybeans dextrose broth (SDB) on Sabouraud dextrose agar, Yeast extract potato dextrose agar and Spider medium. The combination of serum and temperature is excellent at promoting the yeast to mycelial conversion and it also induces the expression of hyphal specific genes. Our results demonstrate that the combination of serum and each temperature provides a distinct proportion of blastospores, budding yeast cells, germ tube, pseudohyphae and true hyphal cells. Remarkable change in colonial pattern between the cells cultured after incubating in serum and the cells cultured after incubating in SDB was observed in SDA in contrast with YEPD and Spider medium. On most solid media, colonies of C. albicans are composed of three types of cells: budding yeast, pseudohyphae and hyphae. All three forms are also found in infected tissues, and the transition between these forms is a key for pathogenesis.
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Zheng, Xinde, Yanming Wang i Yue Wang. "Hgc1, a novel hypha-specific G1 cyclin-related protein regulates Candida albicans hyphal morphogenesis". EMBO Journal 23, nr 8 (8.04.2004): 1845–56. http://dx.doi.org/10.1038/sj.emboj.7600195.
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McKenzie, C. G. J., U. Koser, L. E. Lewis, J. M. Bain, H. M. Mora-Montes, R. N. Barker, N. A. R. Gow i L. P. Erwig. "Contribution of Candida albicans Cell Wall Components to Recognition by and Escape from Murine Macrophages". Infection and Immunity 78, nr 4 (1.02.2010): 1650–58. http://dx.doi.org/10.1128/iai.00001-10.
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ABSTRACT The pathogenicity of the opportunistic human fungal pathogen Candida albicans depends on its ability to escape destruction by the host immune system. Using mutant strains that are defective in cell surface glycosylation, cell wall protein synthesis, and yeast-hypha morphogenesis, we have investigated three important aspects of C. albicans innate immune interactions: phagocytosis by primary macrophages and macrophage cell lines, hyphal formation within macrophage phagosomes, and the ability to escape from and kill macrophages. We show that cell wall glycosylation is critically important for the recognition and ingestion of C. albicans by macrophages. Phagocytosis was significantly reduced for mutants deficient in phosphomannan biosynthesis (mmn4Δ, pmr1Δ, and mnt3 mnt5Δ), whereas O- and N-linked mannan defects (mnt1Δ mnt2Δ and mns1Δ) were associated with increased ingestion, compared to the parent wild-type strains and genetically complemented controls. In contrast, macrophage uptake of mutants deficient in cell wall proteins such as adhesins (ece1Δ, hwp1Δ, and als3Δ) and yeast-locked mutants (clb2Δ, hgc1Δ, cph1Δ, efg1Δ, and efg1Δ cph1Δ), was similar to that observed for wild-type C. albicans. Killing of macrophages was abrogated in hypha-deficient strains, significantly reduced in all glycosylation mutants, and comparable to wild type in cell wall protein mutants. The diminished ability of glycosylation mutants to kill macrophages was not a consequence of impaired hyphal formation within macrophage phagosomes. Therefore, cell wall composition and the ability to undergo yeast-hypha morphogenesis are critical determinants of the macrophage's ability to ingest and process C. albicans.
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Carlisle, Patricia L., i David Kadosh. "Candida albicans Ume6, a Filament-Specific Transcriptional Regulator, Directs Hyphal Growth via a Pathway Involving Hgc1 Cyclin-Related Protein". Eukaryotic Cell 9, nr 9 (23.07.2010): 1320–28. http://dx.doi.org/10.1128/ec.00046-10.
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ABSTRACT The ability of Candida albicans, the most common human fungal pathogen, to transition from yeast to hyphae is essential for pathogenicity. While a variety of transcription factors important for filamentation have been identified and characterized, links between transcriptional regulators of C. albicans morphogenesis and molecular mechanisms that drive hyphal growth are not well defined. We have previously observed that constitutive expression of UME6, which encodes a filament-specific transcriptional regulator, is sufficient to direct hyphal growth in the absence of filament-inducing conditions. Here we show that HGC1, encoding a cyclin-related protein necessary for hyphal growth under filament-inducing conditions, is specifically important for agar invasion, hyphal extension, and formation of true septa in response to constitutive UME6 expression under non-filament-inducing conditions. HGC1-dependent inactivation of Rga2, a Cdc42 GTPase activating protein (GAP), also appears to be important for these processes. In response to filament-inducing conditions, HGC1 is induced prior to UME6 although UME6 controls the level and duration of HGC1 expression, which are likely to be important for hyphal extension. Interestingly, an epistasis analysis suggests that UME6 and HGC1 play distinct roles during early filament formation. These findings establish a link between a key regulator of filamentation and a downstream mechanism important for hyphal formation. In addition, this study demonstrates that a strain expressing constitutive high levels of UME6 provides a powerful strategy to specifically dissect downstream mechanisms important for hyphal development in the absence of complex filament-inducing conditions.
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de Billerbeck, Virginia G., Christine G. Roques, Jean-Marie Bessière, Jean-Louis Fonvieille i Robert Dargent. "Effects of Cymbopogon nardus (L.) W. Watson essential oil on the growth and morphogenesis of Aspergillus niger". Canadian Journal of Microbiology 47, nr 1 (1.01.2001): 9–17. http://dx.doi.org/10.1139/w00-117.
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The growth inhibitory effect of Cymbopogon nardus (L.) W. Watson var. nardus essential oil on Aspergillus niger (Van Tieghem) mycelium was determined on agar medium. The mycelium growth was completely inhibited at 800 mg/L. This concentration was found to be lethal under the test conditions. Essential oil at 400 mg/L caused growth inhibition of 80% after 4 days of incubation, and a delay in conidiation of 4 days compared with the control. Microscopic observations were carried out to determine the ultrastructural modifications of A. niger hyphae after treatment with C. nardus essential oil. The main change observed by transmission electron microscopy concerned the hyphal diameter and the hyphal wall, which appeared markedly thinner. These modifications in cytological structure might be caused by the interference of the essential oil with the enzymes responsible for wall synthesis which disturb normal growth. Moreover, the essential oil caused plasma membrane disruption and mitochondrial structure disorganization. The findings thus indicate the possibility of exploiting Cymbopogon nardus essential oil as an effective inhibitor of biodegrading and storage-contaminating fungi.Key words: essential oil, antifungal agent, hyphal ultrastructure, cell wall, scanning electron microscopy, transmission electron microscopy.
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Li, Lifang, Chengda Zhang i James B. Konopka. "A Candida albicans Temperature-Sensitivecdc12-6Mutant Identifies Roles for Septins in Selection of Sites of Germ Tube Formation and Hyphal Morphogenesis". Eukaryotic Cell 11, nr 10 (10.08.2012): 1210–18. http://dx.doi.org/10.1128/ec.00216-12.
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ABSTRACTSeptins were identified for their role in septation inSaccharomyces cerevisiaeand were subsequently implicated in other morphogenic processes. To study septins inCandida albicanshyphal morphogenesis, a temperature-sensitive mutation was created that altered the C terminus of the essential Cdc12 septin. Thecdc12-6cells grew well at room temperature, but at 37°C they displayed expected defects in septation, nuclear localization, and bud morphogenesis. Although serum stimulated thecdc12-6cells at 37°C to form germ tube outgrowths, the mutant could not maintain polarized hyphal growth and instead formed chains of elongated cell compartments. Serum also stimulated thecdc12-6mutant to induce a hyphal reporter gene (HWP1-GFP) and a characteristic zone of filipin staining at the leading edge of growth. Interestingly,cdc12-6cells shifted to 37°C in the absence of serum gradually displayed enriched filipin staining at the tip, which may be due to the altered cell cycle regulation. A striking difference from the wild type was that thecdc12-6cells frequently formed a second germ tube in close proximity to the first. The mutant cells also failed to form the diffuse band of septins at the base of germ tubes and hyphae, indicating that this septin band plays a role in preventing proximal formation of germ tubes in a manner analogous to bud site selection. These studies demonstrate that not only are septins important for cytokinesis, but they also promote polarized morphogenesis and selection of germ tube sites that may help disseminate an infection in host tissues.