scholarly journals SO, a Protein Involved in Hyphal Fusion in Neurospora crassa, Localizes to Septal Plugs

2006 ◽  
Vol 6 (1) ◽  
pp. 84-94 ◽  
Author(s):  
André Fleiβner ◽  
N. Louise Glass
Keyword(s):  
Cell Death ◽  
Neurospora Crassa ◽  
Colony Development ◽  
Independent Manner ◽  
Hyphal Fusion ◽  
Filamentous Ascomycete ◽  
Sealing Material ◽  
Woronin Body ◽  
Local Injury ◽  
Extensive Damage

ABSTRACT The colony of a filamentous ascomycete fungus typically grows as a multinucleate syncytium. While this syncytial organization has developmental advantages, it bears the risk of extensive damage caused by local injury of hyphae. Loss of cytoplasm in injured hyphae is restricted by the fast and efficient sealing of the central pores of hyphal crosswalls, or septa, by a peroxisome-derived organelle called the Woronin body. The formation of septal plugs is also associated with development and leads to separation of certain parts of the colony. Septal plugs associated with developmental processes or aging hyphae typically occur by the accumulation of sealing material. Here we report that in Neurospora crassa, a protein necessary for hyphal fusion and proper colony development called SO (SOFT) localizes to septal plugs. In response to injury, SO accumulates at the septal plug in a Woronin body-independent manner. However, the presence of the Woronin body affects the speed of accumulation of SO at the septal pore. We determined that SO contributes to, but is not essential for, septal plugging. SO accumulation was also observed at septal plugs formed during hyphal aging and during programmed cell death mediated by genetic differences at heterokaryon incompatibility (het) loci.

scholarly journals VIB-1 Is Required for Expression of Genes Necessary for Programmed Cell Death in Neurospora crassa

2006 ◽  
Vol 5 (12) ◽  
pp. 2161-2173 ◽  
Author(s):  
Karine Dementhon ◽  
Gopal Iyer ◽  
N. Louise Glass
Keyword(s):  
Cell Death ◽  
Programmed Cell Death ◽  
Neurospora Crassa ◽  
Filamentous Fungi ◽  
Somatic Growth ◽  
Genetic Differences ◽  
Extracellular Proteases ◽  
Hyphal Fusion ◽  
Expression Of Genes ◽  
Nonself Recognition

ABSTRACT Nonself recognition during somatic growth is an essential and ubiquitous phenomenon in both prokaryotic and eukaryotic species. In filamentous fungi, nonself recognition is also important during vegetative growth. Hyphal fusion between genetically dissimilar individuals results in rejection of heterokaryon formation and in programmed cell death of the fusion compartment. In filamentous fungi, such as Neurospora crassa, nonself recognition and heterokaryon incompatibility (HI) are regulated by genetic differences at het loci. In N. crassa, mutations at the vib-1 locus suppress nonself recognition and HI mediated by genetic differences at het-c/pin-c, mat, and un-24/het-6. vib-1 is a homolog of Saccharomyces cerevisiae NDT80, which is a transcriptional activator of genes during meiosis. For this study, we determined that vib-1 encodes a nuclear protein and showed that VIB-1 localization varies during asexual reproduction and during HI. vib-1 is required for the expression of genes involved in nonself recognition and HI, including pin-c, tol, and het-6; all of these genes encode proteins containing a HET domain. vib-1 is also required for the production of downstream effectors associated with HI, including the production of extracellular proteases upon carbon and nitrogen starvation. Our data support a model in which mechanisms associated with starvation and nonself recognition/HI are interconnected. VIB-1 is a major regulator of responses to nitrogen and carbon starvation and is essential for the expression of genes involved in nonself recognition and death in N. crassa.

scholarly journals The so Locus Is Required for Vegetative Cell Fusion and Postfertilization Events in Neurospora crassa

2005 ◽  
Vol 4 (5) ◽  
pp. 920-930 ◽  
Author(s):  
André Fleißner ◽  
Sovan Sarkar ◽  
David J. Jacobson ◽  
M. Gabriela Roca ◽  
Nick D. Read ◽  
...  
Keyword(s):  
Neurospora Crassa ◽  
Cell Fusion ◽  
Protein Interactions ◽  
Cell Communication ◽  
Model Organism ◽  
Female Sterility ◽  
Wild Type ◽  
Hyphal Fusion ◽  
Filamentous Ascomycete ◽  
Ascomycete Yeast

ABSTRACT The process of cell fusion is a basic developmental feature found in most eukaryotic organisms. In filamentous fungi, cell fusion events play an important role during both vegetative growth and sexual reproduction. We employ the model organism Neurospora crassa to dissect the mechanisms of cell fusion and cell-cell communication involved in fusion processes. In this study, we characterized a mutant with a mutation in the gene so, which exhibits defects in cell fusion. The so mutant has a pleiotropic phenotype, including shortened aerial hyphae, an altered conidiation pattern, and female sterility. Using light microscopy and heterokaryon tests, the so mutant was shown to possess defects in germling and hyphal fusion. Although so produces conidial anastomosis tubes, so germlings did not home toward wild-type germlings nor were wild-type germlings attracted to so germlings. We employed a trichogyne attraction and fusion assay to determine whether the female sterility of the so mutant is caused by impaired communication or fusion failure between mating partners. so showed no defects in attraction or fusion between mating partners, indicating that so is specific for vegetative hyphal fusion and/or associated communication events. The so gene encodes a protein of unknown function, but which contains a WW domain; WW domains are predicted to be involved in protein-protein interactions. Database searches showed that so was conserved in the genomes of filamentous ascomycete fungi but was absent in ascomycete yeast and basidiomycete species.

scholarly journals Role of a Mitogen-Activated Protein Kinase Pathway during Conidial Germination and Hyphal Fusion in Neurospora crassa

2004 ◽  
Vol 3 (2) ◽  
pp. 348-358 ◽  
Author(s):  
Amita Pandey ◽  
M. Gabriela Roca ◽  
Nick D. Read ◽  
N. Louise Glass
Keyword(s):  
Map Kinase ◽  
Neurospora Crassa ◽  
Conidial Germination ◽  
Colony Development ◽  
Phenotypic Traits ◽  
Hyphal Fusion ◽  
Mitogen Activated Protein ◽  
Map Kinase Pathways ◽  
Map Kinase Kinase Kinase ◽  
Map Kinase Kinase

ABSTRACT Mitogen-activated protein (MAP) kinase signaling pathways are ubiquitous and evolutionarily conserved in eukaryotic organisms. MAP kinase pathways are composed of a MAP kinase, a MAP kinase kinase, and a MAP kinase kinase kinase; activation is regulated by sequential phosphorylation. Components of three MAP kinase pathways have been identified by genome sequence analysis in the filamentous fungus Neurospora crassa. One of the predicted MAP kinases in N. crassa, MAK-2, shows similarity to Fus3p and Kss1p of Saccharomyces cerevisiae, which are involved in sexual reproduction and filamentation, respectively. In this study, we show that an N. crassa mutant disrupted in mak-2 exhibits a pleiotropic phenotype: derepressed conidiation, shortened aerial hyphae, lack of vegetative hyphal fusion, female sterility, and autonomous ascospore lethality. We assessed the phosphorylation of MAK-2 during conidial germination and early colony development. Peak levels of MAK-2 phosphorylation were most closely associated with germ tube elongation, branching, and hyphal fusion events between conidial germlings. A MAP kinase kinase kinase (NRC-1) is the predicted product of N. crassa nrc-1 locus and is a homologue of STE11 in S. cerevisiae. An nrc-1 mutant shares many of the same phenotypic traits as the mak-2 mutant and, in particular, is a hyphal fusion mutant. We show that MAK-2 phosphorylation during early colony development is dependent upon the presence of NRC-1 and postulate that phosphorylation of MAK-2 is required for hyphal fusion events that occur during conidial germination.

scholarly journals Transcriptional profiling and functional analysis of heterokaryon incompatibility in Neurospora crassa reveals that reactive oxygen species, but not metacaspases, are associated with programmed cell death

Microbiology ◽  
2009 ◽  
Vol 155 (12) ◽  
pp. 3957-3970 ◽  
Author(s):  
Elizabeth Hutchison ◽  
Sarah Brown ◽  
Chaoguang Tian ◽  
N. Louise Glass
Keyword(s):  
Reactive Oxygen Species ◽  
Cell Death ◽  
Programmed Cell Death ◽  
Neurospora Crassa ◽  
Fungal Infections ◽  
Reactive Oxygen ◽  
Oxygen Species ◽  
Hyphal Fusion ◽  
Heterokaryon Incompatibility ◽  
Nonself Recognition

Heterokaryon incompatibility (HI) is a nonself recognition phenomenon occurring in filamentous fungi that is important for limiting resource plundering and restricting viral transfer between strains. Nonself recognition and HI occurs during hyphal fusion between strains that differ at het loci. If two strains undergo hyphal fusion, but differ in allelic specificity at a het locus, the fusion cell is compartmentalized and undergoes a rapid programmed cell death (PCD). Incompatible heterokaryons show a macroscopic phenotype of slow growth and diminished conidiation, and a microscopic phenotype of hyphal compartmentation and cell death. To understand processes associated with HI and PCD, we used whole-genome microarrays for Neurospora crassa to assess transcriptional differences associated with induction of HI mediated by differences in het-c pin-c haplotype. Our data show that HI is a dynamic and transcriptionally active process. The production of reactive oxygen species is implicated in the execution of HI and PCD in N. crassa, as are several genes involved in phosphatidylinositol and calcium signalling pathways. However, genes encoding mammalian homologues of caspases or apoptosis-inducing factor (AIF) are not required for HI or programmed cell death. These data indicate that PCD during HI occurs via a novel and possibly fungal-specific mechanism, making this pathway an attractive drug target for control of fungal infections.

scholarly journals Programmed Cell Death in Neurospora crassa

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
A. Pedro Gonçalves ◽  
Arnaldo Videira
Keyword(s):  
Hydrogen Peroxide ◽  
Cell Death ◽  
Programmed Cell Death ◽  
Neurospora Crassa ◽  
Filamentous Fungus ◽  
Mammalian Cells ◽  
Model Organism ◽  
Chemical Induction ◽  
Hyphal Fusion ◽  
Heterokaryon Incompatibility

Programmed cell death has been studied for decades in mammalian cells, but simpler organisms, including prokaryotes, plants, and fungi, also undergo regulated forms of cell death. We highlight the usefulness of the filamentous fungus Neurospora crassa as a model organism for the study of programmed cell death. In N. crassa, cell death can be triggered genetically due to hyphal fusion between individuals with different allelic specificities at het loci, in a process called “heterokaryon incompatibility.” Chemical induction of cell death can also be achieved upon exposure to death-inducing agents like staurosporine, phytosphingosine, or hydrogen peroxide. A summary of the recent advances made by our and other groups on the discovery of the mechanisms and mediators underlying the process of cell death in N. crassa is presented.

scholarly journals Discovery of fungal surface NADases predominantly present in pathogenic species

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Øyvind Strømland ◽  
Juha P. Kallio ◽  
Annica Pschibul ◽  
Renate H. Skoge ◽  
Hulda M. Harðardóttir ◽  
...  
Keyword(s):  
Cell Death ◽  
Aspergillus Fumigatus ◽  
Neurospora Crassa ◽  
Binding Site ◽  
Host Cell ◽  
Nicotinamide Adenine Dinucleotide ◽  
Catalytic Mechanism ◽  
Pathogenic Species ◽  
X Ray ◽  
Cellular Bioenergetics

AbstractNicotinamide adenine dinucleotide (NAD) is a key molecule in cellular bioenergetics and signalling. Various bacterial pathogens release NADase enzymes into the host cell that deplete the host’s NAD+ pool, thereby causing rapid cell death. Here, we report the identification of NADases on the surface of fungi such as the pathogen Aspergillus fumigatus and the saprophyte Neurospora crassa. The enzymes harbour a tuberculosis necrotizing toxin (TNT) domain and are predominately present in pathogenic species. The 1.6 Å X-ray structure of the homodimeric A. fumigatus protein reveals unique properties including N-linked glycosylation and a Ca2+-binding site whose occupancy regulates activity. The structure in complex with a substrate analogue suggests a catalytic mechanism that is distinct from those of known NADases, ADP-ribosyl cyclases and transferases. We propose that fungal NADases may convey advantages during interaction with the host or competing microorganisms.

scholarly journals Cell Biology of Conidial Anastomosis Tubes in Neurospora crassa

2005 ◽  
Vol 4 (5) ◽  
pp. 911-919 ◽  
Author(s):  
M. Gabriela Roca ◽  
Jochen Arlt ◽  
Chris E. Jeffree ◽  
Nick D. Read
Keyword(s):  
Neurospora Crassa ◽  
Optical Tweezers ◽  
Cell Biology ◽  
Transmembrane Protein ◽  
Mitogen Activated Protein Kinase ◽  
Cellular Element ◽  
Hyphal Fusion ◽  
Self Recognition ◽  
Mitogen Activated Protein ◽  
Germ Tubes

ABSTRACT Although hyphal fusion has been well documented in mature colonies of filamentous fungi, it has been little studied during colony establishment. Here we show that specialized hyphae, called conidial anastomosis tubes (CATs), are produced by all types of conidia and by conidial germ tubes of Neurospora crassa. The CAT is shown to be a cellular element that is morphologically and physiologically distinct from a germ tube and under separate genetic control. In contrast to germ tubes, CATs are thinner, shorter, lack branches, exhibit determinate growth, and home toward each other. Evidence for an extracellular CAT inducer derived from conidia was obtained because CAT formation was reduced at low conidial concentrations. A cr-1 mutant lacking cyclic AMP (cAMP) produced CATs, indicating that the inducer is not cAMP. Evidence that the transduction of the CAT inducer signal involves a putative transmembrane protein (HAM-2) and the MAK-2 and NRC-1 proteins of a mitogen-activated protein kinase signaling pathway was obtained because ham-2, mak-2, and nrc-1 mutants lacked CATs. Optical tweezers were used in a novel experimental assay to micromanipulate whole conidia and germlings to analyze chemoattraction between CATs during homing. Strains of the same and opposite mating type were shown to home toward each other. The cr-1 mutant also underwent normal homing, indicating that cAMP is not the chemoattractant. ham-2, mak-2, and nrc-1 macroconidia did not attract CATs of the wild type. Fusion between CATs of opposite mating types was partially inhibited, providing evidence of non-self-recognition prior to fusion. Microtubules and nuclei passed through fused CATs.

scholarly journals Extracellular calcium triggers unique transcriptional programs and modulates staurosporine-induced cell death in Neurospora crassa

2014 ◽  
Vol 1 (9) ◽  
pp. 289-302 ◽  
Author(s):  
Pedro Goncalves ◽  
◽  
Joao Monteiro ◽  
Chiara Lucchi ◽  
David Kowbel ◽  
...  
Keyword(s):  
Cell Death ◽  
Neurospora Crassa ◽  
Extracellular Calcium

scholarly journals The ham-2 Locus, Encoding a Putative Transmembrane Protein, Is Required for Hyphal Fusion in Neurospora crassa

Genetics ◽  
2002 ◽  
Vol 160 (1) ◽  
pp. 169-180
Author(s):  
Qijun Xiang ◽  
Carolyn Rasmussen ◽  
N Louise Glass
Keyword(s):  
Neurospora Crassa ◽  
Somatic Cell ◽  
Molecular Mechanism ◽  
Cell Fusion ◽  
Deletion Mutant ◽  
Transmembrane Protein ◽  
Wild Type ◽  
Vegetative Incompatibility ◽  
Hyphal Fusion ◽  
Aerial Hyphae

Abstract Somatic cell fusion is common during organogenesis in multicellular eukaryotes, although the molecular mechanism of cell fusion is poorly understood. In filamentous fungi, somatic cell fusion occurs during vegetative growth. Filamentous fungi grow as multinucleate hyphal tubes that undergo frequent hyphal fusion (anastomosis) during colony expansion, resulting in the formation of a hyphal network. The molecular mechanism of the hyphal fusion process and the role of networked hyphae in the growth and development of these organisms are unexplored questions. We use the filamentous fungus Neurospora crassa as a model to study the molecular mechanism of hyphal fusion. In this study, we identified a deletion mutant that was restricted in its ability to undergo both self-hyphal fusion and fusion with a different individual to form a heterokaryon. This deletion mutant displayed pleiotropic defects, including shortened aerial hyphae, altered conidiation pattern, female sterility, slow growth rate, lack of hyphal fusion, and suppression of vegetative incompatibility. Complementation with a single open reading frame (ORF) within the deletion region in this mutant restored near wild-type growth rates, female fertility, aerial hyphae formation, and hyphal fusion, but not vegetative incompatibility and wild-type conidiation pattern. This ORF, which we named ham-2 (for hyphal anastomosis), encodes a putative transmembrane protein that is highly conserved, but of unknown function among eukaryotes.

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