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Son YE, Yu JH, Park HS. Regulators of the Asexual Life Cycle of Aspergillus nidulans. Cells 2023; 12:1544. [PMID: 37296664 PMCID: PMC10253035 DOI: 10.3390/cells12111544] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2023] [Revised: 06/01/2023] [Accepted: 06/02/2023] [Indexed: 06/12/2023] Open
Abstract
The genus Aspergillus, one of the most abundant airborne fungi, is classified into hundreds of species that affect humans, animals, and plants. Among these, Aspergillus nidulans, as a key model organism, has been extensively studied to understand the mechanisms governing growth and development, physiology, and gene regulation in fungi. A. nidulans primarily reproduces by forming millions of asexual spores known as conidia. The asexual life cycle of A. nidulans can be simply divided into growth and asexual development (conidiation). After a certain period of vegetative growth, some vegetative cells (hyphae) develop into specialized asexual structures called conidiophores. Each A. nidulans conidiophore is composed of a foot cell, stalk, vesicle, metulae, phialides, and 12,000 conidia. This vegetative-to-developmental transition requires the activity of various regulators including FLB proteins, BrlA, and AbaA. Asymmetric repetitive mitotic cell division of phialides results in the formation of immature conidia. Subsequent conidial maturation requires multiple regulators such as WetA, VosA, and VelB. Matured conidia maintain cellular integrity and long-term viability against various stresses and desiccation. Under appropriate conditions, the resting conidia germinate and form new colonies, and this process is governed by a myriad of regulators, such as CreA and SocA. To date, a plethora of regulators for each asexual developmental stage have been identified and investigated. This review summarizes our current understanding of the regulators of conidial formation, maturation, dormancy, and germination in A. nidulans.
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Affiliation(s)
- Ye-Eun Son
- Major in Food Biomaterials, School of Food Science and Biotechnology, Kyungpook National University, Daegu 41566, Republic of Korea;
| | - Jae-Hyuk Yu
- Department of Bacteriology, Food Research Institute, University of Wisconsin-Madison, Madison, WI 53706, USA;
| | - Hee-Soo Park
- Major in Food Biomaterials, School of Food Science and Biotechnology, Kyungpook National University, Daegu 41566, Republic of Korea;
- Department of Integrative Biology, Kyungpook National University, Daegu 41566, Republic of Korea
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Phenotype to genotype in Neurospora crassa: Association of the scumbo phenotype with mutations in the gene encoding ceramide C9-methyltransferase. CURRENT RESEARCH IN MICROBIAL SCIENCES 2022; 3:100117. [PMID: 35909622 PMCID: PMC9325734 DOI: 10.1016/j.crmicr.2022.100117] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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Hernández-González M, Bravo-Plaza I, de Los Ríos V, Pinar M, Pantazopoulou A, Peñalva MA. COPI localizes to the early Golgi in Aspergillus nidulans. Fungal Genet Biol 2018; 123:78-86. [PMID: 30550852 DOI: 10.1016/j.fgb.2018.12.003] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2018] [Revised: 12/07/2018] [Accepted: 12/08/2018] [Indexed: 01/21/2023]
Abstract
Coatomer-I (COPI) is a heteromeric protein coat that facilitates the budding of membranous carriers mediating Golgi-to-ER and intra-Golgi transport. While the structural features of COPI have been thoroughly investigated, its physiological role is insufficiently understood. Here we exploit the amenability of A. nidulans for studying intracellular traffic, taking up previous studies by Breakspear et al. (2007) with the α-COP/CopA subunit of COPI. Endogenously tagged α-COP/CopA largely localizes to SedVSed5 syntaxin-containing early Golgi cisterna, and acute inactivation of ER-to-Golgi traffic delocalizes COPI to a haze, consistent with the cisternal maturation model. In contrast, the Golgi localization of COPI is independent of the TGN regulators HypBSec7 and HypATrs120, implying that COPI budding predominates at the SedVSed5 early Golgi, with lesser contribution of the TGN. This finding agrees with the proposed role of COPI-mediated intra-Golgi retrograde traffic in driving cisternal maturation, which predicts that the capacity of the TGN to generate COPI carriers is low. The COPI early Golgi compartments intimately associates with Sec13-containing ER exit sites. Characterization of the heat-sensitive copA1ts (sodVIC1) mutation showed that it results in a single residue substitution in the ε-COP-binding Carboxyl-Terminal-Domain of α-COP that likely destabilizes its folding. However, we show that Golgi disorganization by copA1ts necessitates >150 min-long incubation at 42 °C. This weak subcellular phenotype makes it unsuitable for inactivating COPI traffic acutely for microscopy studies, and explains the aneuploidy-stabilizing role of the mutation at subrestrictive temperatures.
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Affiliation(s)
- Miguel Hernández-González
- Department of Cellular and Molecular Biology, Centro de Investigaciones Biológicas CSIC, Ramiro de Maeztu 9, Madrid 28040, Spain; Centre for Mechanochemical Cell Biology, Gibbet Hill Road, Warwick Medical School, University of Warwick, Coventry CV4 7AL, UK(1)
| | - Ignacio Bravo-Plaza
- Department of Cellular and Molecular Biology, Centro de Investigaciones Biológicas CSIC, Ramiro de Maeztu 9, Madrid 28040, Spain
| | - Vivian de Los Ríos
- Proteomics and Genomics Facility, Centro de Investigaciones Biológicas CSIC, Ramiro de Maeztu 9, Madrid 28040, Spain
| | - Mario Pinar
- Department of Cellular and Molecular Biology, Centro de Investigaciones Biológicas CSIC, Ramiro de Maeztu 9, Madrid 28040, Spain
| | - Areti Pantazopoulou
- Department of Cellular and Molecular Biology, Centro de Investigaciones Biológicas CSIC, Ramiro de Maeztu 9, Madrid 28040, Spain; Department of Molecular Genetics and Cell Biology, Biological Sciences Division, The University of Chicago, United States(1).
| | - Miguel A Peñalva
- Department of Cellular and Molecular Biology, Centro de Investigaciones Biológicas CSIC, Ramiro de Maeztu 9, Madrid 28040, Spain.
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Kang EH, Song EJ, Kook JH, Lee HH, Jeong BR, Park HM. Depletion of ε-COP in the COPI Vesicular Coat Reduces Cleistothecium Production in Aspergillus nidulans. MYCOBIOLOGY 2015; 43:31-36. [PMID: 25892912 PMCID: PMC4397377 DOI: 10.5941/myco.2015.43.1.31] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/22/2014] [Revised: 12/01/2014] [Accepted: 01/05/2015] [Indexed: 06/04/2023]
Abstract
We have previously isolated ε-COP, the α-COP interactor in COPI of Aspergillus nidulans, by yeast two-hybrid screening. To understand the function of ε-COP, the aneA (+) gene for ε-COP/AneA was deleted by homologous recombination using a gene-specific disruption cassette. Deletion of the ε-COP gene showed no detectable changes in vegetative growth or asexual development, but resulted in decrease in the production of the fruiting body, cleistothecium, under conditions favorable for sexual development. Unlike in the budding yeast Saccharomyces cerevisiae, in A. nidulans, over-expression of ε-COP did not rescue the thermo-sensitive growth defect of the α-COP mutant at 42℃. Together, these data show that ε-COP is not essential for viability, but it plays a role in fruiting body formation in A. nidulans.
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Affiliation(s)
- Eun-Hye Kang
- Department of Microbiology and Molecular Biology, College of Bioscience and Biotechnology, Chungnam National University, Daejeon 305-764, Korea
| | - Eun-Jung Song
- Department of Microbiology and Molecular Biology, College of Bioscience and Biotechnology, Chungnam National University, Daejeon 305-764, Korea
| | - Jun Ho Kook
- Department of Microbiology and Molecular Biology, College of Bioscience and Biotechnology, Chungnam National University, Daejeon 305-764, Korea
| | - Hwan-Hee Lee
- Department of Microbiology and Molecular Biology, College of Bioscience and Biotechnology, Chungnam National University, Daejeon 305-764, Korea
| | - Bo-Ri Jeong
- Department of Microbiology and Molecular Biology, College of Bioscience and Biotechnology, Chungnam National University, Daejeon 305-764, Korea
| | - Hee-Moon Park
- Department of Microbiology and Molecular Biology, College of Bioscience and Biotechnology, Chungnam National University, Daejeon 305-764, Korea
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Pinar M, Pantazopoulou A, Peñalva MA. Live-cell imaging of Aspergillus nidulans autophagy: RAB1 dependence, Golgi independence and ER involvement. Autophagy 2013; 9:1024-43. [PMID: 23722157 DOI: 10.4161/auto.24483] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
We exploited the amenability of the fungus Aspergillus nidulans to genetics and live-cell microscopy to investigate autophagy. Upon nitrogen starvation, GFP-Atg8-containing pre-autophagosomal puncta give rise to cup-shaped phagophores and circular (0.9-μm diameter) autophagosomes that disappear in the vicinity of the vacuoles after their shape becomes irregular and their GFP-Atg8 fluorescence decays. This 'autophagosome cycle' gives rise to characteristic cone-shaped traces in kymographs. Autophagy does not require endosome maturation or ESCRTs, as autophagosomes fuse with vacuoles directly in a RabS (homolog of Saccharomyces cerevisiae Ypt7 and mammalian RAB7; written hereafter as RabS(RAB7))-HOPS-(homotypic fusion and vacuole protein sorting complex)-dependent manner. However, by removing RabS(RAB7) or Vps41 (a component of the HOPS complex), we show that autophagosomes may still fuse, albeit inefficiently, with the endovacuolar system in a process almost certainly mediated by RabA(RAB5)/RabB(RAB5) (yeast Vps21 homologs)-CORVET (class C core vacuole/endosome tethering complex), because acute inactivation of HbrA/Vps33, a key component of HOPS and CORVET, completely precludes access of GFP-Atg8 to vacuoles without affecting autophagosome biogenesis. Using a FYVE 2-GFP probe and endosomal PtdIns3P-depleted cells, we imaged PtdIns3P on autophagic membranes. PtdIns3P present on autophagosomes decays at late stages of the cycle, preceding fusion with the vacuole. Autophagy does not require Golgi traffic, but it is crucially dependent on RabO(RAB1). TRAPPIII-specific factor AN7311 (yeast Trs85) localizes to the phagophore assembly site (PAS) and RabO(RAB1) localizes to phagophores and autophagosomes. The Golgi and autophagy roles of RabO(RAB1) are dissociable by mutation: rabO(A136D) hyphae show relatively normal secretion at 28°C but are completely blocked in autophagy. This finding and the lack of Golgi traffic involvement pointed to the ER as one potential source of membranes for autophagy. In agreement, autophagosomes form in close association with ring-shaped omegasome-like ER structures resembling those described in mammalian cells.
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Affiliation(s)
- Mario Pinar
- Centro de Investigaciones Biológicas (CSIC); Madrid, Spain
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Jackson-Hayes L, Hill TW, Loprete DM, Fay LM, Gordon BS, Nkashama SA, Patel RK, Sartain CV. Two GDP-mannose transporters contribute to hyphal form and cell wall integrity in Aspergillus nidulans. MICROBIOLOGY-SGM 2008; 154:2037-2047. [PMID: 18599832 DOI: 10.1099/mic.0.2008/017483-0] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
In order to identify novel genes affecting cell wall integrity, we have generated mutant strains of the filamentous fungus Aspergillus nidulans that show hypersensitivity to the chitin-binding agent Calcofluor White (CFW). Affected loci are designated cal loci. The phenotype of one of these alleles, calI11, also includes shortened hyphal compartments and increased density of branching in the absence of CFW, as well as reduced staining of cell walls by the lectin FITC-Concanavalin A (ConA), which has strong binding affinity for mannosyl residues. We have identified two A. nidulans genes (AN8848.3 and AN9298.3, designated gmtA and gmtB, respectively) that complement all aspects of the phenotype. Both genes show strong sequence similarity to GDP-mannose transporters (GMTs) of Saccharomyces and other yeasts. Sequencing of gmtA from the calI11 mutant strain reveals a G to C mutation at position 943, resulting in a predicted alanine to proline substitution at amino acid position 315 within a region that is highly conserved among other fungi. No mutations were observed in the mutant strain's allele of gmtB. Meiotic mapping demonstrated a recombination frequency of under 1 % between the calI locus and the phenA locus (located approximately 9.5 kb from AN8848.3), confirming that gmtA and calI are identical. A GmtA-GFP chimera exhibits a punctate distribution pattern, consistent with that shown by putative Golgi markers in A. nidulans. However, this distribution did not overlap with that of the putative Golgi equivalent marker CopA-monomeric red fluorescent protein (mRFP), which may indicate that the physically separated Golgi-equivalent organelles of A. nidulans represent physiologically distinct counterparts of the stacked cisternae of plants and animals. These findings demonstrate that gmtA and gmtB play roles in cell wall metabolism in A. nidulans similar to those previously reported for GMTs in yeasts.
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Affiliation(s)
| | - Terry W Hill
- Departments of Chemistry and Biology, Rhodes College, Memphis, TN 38112, USA
| | - Darlene M Loprete
- Departments of Chemistry and Biology, Rhodes College, Memphis, TN 38112, USA
| | - Lauren M Fay
- Departments of Chemistry and Biology, Rhodes College, Memphis, TN 38112, USA
| | - Barbara S Gordon
- Departments of Chemistry and Biology, Rhodes College, Memphis, TN 38112, USA
| | - Sonia A Nkashama
- Departments of Chemistry and Biology, Rhodes College, Memphis, TN 38112, USA
| | - Ravi K Patel
- Departments of Chemistry and Biology, Rhodes College, Memphis, TN 38112, USA
| | - Caroline V Sartain
- Departments of Chemistry and Biology, Rhodes College, Memphis, TN 38112, USA
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Aspergillus nidulans hypB encodes a Sec7-domain protein important for hyphal morphogenesis. Fungal Genet Biol 2008; 45:749-59. [DOI: 10.1016/j.fgb.2007.11.005] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2007] [Revised: 11/07/2007] [Accepted: 11/19/2007] [Indexed: 01/31/2023]
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Rapid tip-directed movement of Golgi equivalents in growing Aspergillus nidulans hyphae suggests a mechanism for delivery of growth-related materials. Microbiology (Reading) 2008; 154:1544-1553. [DOI: 10.1099/mic.0.2007/014811-0] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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Breakspear A, Langford KJ, Momany M, Assinder SJ. CopA:GFP localizes to putative Golgi equivalents in Aspergillus nidulans. FEMS Microbiol Lett 2008; 277:90-7. [PMID: 17986089 DOI: 10.1111/j.1574-6968.2007.00945.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
Abstract
The Golgi complex is a main component of the eukaryotic secretory system and functions to modify nascent proteins sent from the endoplasmic reticulum. Ultrastructural studies of filamentous fungi have shown Golgi to be individual smooth membrane cisternae that are referred to as Golgi equivalents or dictyosomes. The Aspergillus nidulans copA gene encodes a homolog of mammalian coat protein (alpha-COP), a constituent of the Golgi-localized COPI vesicle coat. Here, the localization of A. nidulansalpha-COP was examined in live cells using the reporter green fluorescent protein (GFP). CopA:GFP localized to putative Golgi equivalents that were concentrated at hyphal tips. The localization was disrupted by the fungal metabolite brefeldin A. To investigate the significance of the microtubule cytoskeleton in the localization of putative Golgi equivalents, the copA:gfp fusion was expressed in a temperature-sensitive dynein mutant. In addition, a wild-type strain expressing copA:gfp was treated with the microtubule-disrupting drug nocodazole. The results suggest that the microtubule cytoskeleton is not the primary mechanism of localizing putative Golgi equivalents in A. nidulans.
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Affiliation(s)
- Andrew Breakspear
- School of Biological Sciences, University of Wales, Bangor, Gwynedd, UK.
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Virag A, Lee MP, Si H, Harris SD. Regulation of hyphal morphogenesis by cdc42 and rac1 homologues in Aspergillus nidulans. Mol Microbiol 2007; 66:1579-96. [PMID: 18005099 DOI: 10.1111/j.1365-2958.2007.06021.x] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The ability of filamentous fungi to form hyphae requires the establishment and maintenance of a stable polarity axis. Based on studies in yeasts and animals, the GTPases Cdc42 and Rac1 are presumed to play a central role in organizing the morphogenetic machinery to enable axis formation and stabilization. Here, we report that Cdc42 (ModA) and Rac1 (RacA) share an overlapping function required for polarity establishment in Aspergillus nidulans. Nevertheless, Cdc42 appears to have a more important role in hyphal morphogenesis in that it alone is required for the timely formation of lateral branches. In addition, we provide genetic evidence suggesting that the polarisome components SepA and SpaA function downstream of Cdc42 in a pathway that may regulate microfilament formation. Finally, we show that microtubules become essential for the establishment of hyphal polarity when the function of either Cdc42 or SepA is compromised. Our results are consistent with the action of parallel Cdc42 and microtubule-based pathways in regulating the formation of a stable axis of hyphal polarity in A. nidulans.
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Affiliation(s)
- Aleksandra Virag
- Plant Science Initiative and Department of Plant Pathology, University of Nebraska, Lincoln, NE 68588-0660, USA
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Abstract
The formation of highly polarized hyphae that grow by apical extension is a defining feature of the filamentous fungi. High-resolution microscopy and mathematical modeling have revealed the importance of the cytoskeleton and the Spitzenkorper (an apical vesicle cluster) in hyphal morphogenesis. However, the underlying molecular mechanisms remain poorly characterized. In this review, the pathways and functions known to be involved in polarized hyphal growth are summarized. A central theme is the notion that the polarized growth of hyphae is more complex than in yeast, though similar sets of core pathways are likely utilized. In addition, a model for the establishment and maintenance of hyphal polarity is presented. Key features of the model include the idea that polarity establishment is a stochastic process that occurs independent of internal landmarks. Moreover, the stabilization of nascent polarity axes may be the critical step that permits the emergence of a new hypha.
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Affiliation(s)
- Steven D Harris
- Plant Science Initiative and Department of Plant Pathology, University of Nebraska, Lincoln, NE 68588, USA
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Harris SD, Momany M. Polarity in filamentous fungi: moving beyond the yeast paradigm. Fungal Genet Biol 2004; 41:391-400. [PMID: 14998522 DOI: 10.1016/j.fgb.2003.11.007] [Citation(s) in RCA: 132] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2003] [Accepted: 11/13/2003] [Indexed: 10/26/2022]
Abstract
Filamentous fungi grow by the polar extension of hyphae. This polar growth requires the specification of sites of germ tube or branch emergence, followed by the recruitment of the morphogenetic machinery to those sites for localized cell wall deposition. Researchers attempting to understand hyphal morphogenesis have relied upon the powerful paradigm of bud emergence in the yeast Saccharomyces cerevisiae. The yeast paradigm has provided a useful framework, however several features of hyphal morphogenesis, such as the ability to maintain multiple axes of polarity and an extremely rapid extension rate, cannot be explained by simple extrapolation from yeast models. We discuss recent polarity research from filamentous fungi focusing on the position of germ tube emergence, the relaying of positional information via RhoGTPase modules, and the recruitment of morphogenetic machinery components including cytoskeleton, polarisome and ARP2/3 complexes, and the vesicle trafficking system.
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Affiliation(s)
- Steven D Harris
- Plant Science Initiative and Department of Plant Pathology, University of Nebraska, Lincoln, NE, USA.
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Shi X, Sha Y, Kaminskyj S. Aspergillus nidulans hypA regulates morphogenesis through the secretion pathway. Fungal Genet Biol 2004; 41:75-88. [PMID: 14643261 DOI: 10.1016/j.fgb.2003.09.004] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Aspergillus nidulans hypA encodes a predicted 1474 amino acid, 161.9 kDa cytoplasmic peptide. Strains with hypA1 and hypA6 alleles are wild type at 28 degrees C but have wide, slow-growing hyphae and thick walls at 42 degrees C. hypA1 and hypA6 have identical genetic lesions. hypA1 and hypA6 restrictive phenotypes have statistically similar morphometry, and strains with either allele can conidiate at 42 degrees C. hypA deletion strains require osmotic support and have aberrant morphology, but produce viable spores at 28 degrees C. hypA has full-length orthologs in filamentous fungi and yeasts and a 200 amino acid region with similarity to sequences in plants and animals. The Saccharomyces cerevisiae hypA ortholog is TRS120, a regulatory subunit in the TRAPP II complex that mediates traffic through the Golgi equivalent. Enzyme secretion is reduced in hypA1 cells at 42 degrees C. Endomembranes and cytoplasmic actin arrays in hypA1 have weak polarity at 42 degrees C and cytoplasmic microtubules have reduced number and normal distribution.
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Affiliation(s)
- Xianzong Shi
- Department of Biology, University of Saskatchewan, SK, S7N 5E2 Saskatoon, Canada
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Seiler S, Plamann M. The genetic basis of cellular morphogenesis in the filamentous fungus Neurospora crassa. Mol Biol Cell 2003; 14:4352-64. [PMID: 12960438 PMCID: PMC266756 DOI: 10.1091/mbc.e02-07-0433] [Citation(s) in RCA: 160] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Cellular polarity is a fundamental property of every cell. Due to their extremely fast growth rate (>/=1 microm/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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Affiliation(s)
- Stephan Seiler
- Institut für Mikrobiologie und Genetik, Abteilung Molekulare Mikrobiologie, Universität Göttingen, D-37077 Göttingen, Germany.
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Shaw BD, Momany C, Momany M. Aspergillus nidulans swoF encodes an N-myristoyl transferase. EUKARYOTIC CELL 2002; 1:241-8. [PMID: 12455958 PMCID: PMC118038 DOI: 10.1128/ec.1.2.241-248.2002] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Polar growth is a fundamental process in filamentous fungi and is necessary for disease initiation in many pathogenic systems. Previously, swoF was identified in Aspergillus nidulans as a single-locus, temperature-sensitive (ts) mutant aberrant in both polarity establishment and polarity maintenance. The swoF gene was cloned by complementation of the ts phenotype and sequenced. The derived protein sequence had high identity with N-myristoyl transferases (NMTs) found in fungi, plants, and animals. In addition, wild-type growth at restrictive temperature was partially restored by the addition of myristic acid to the growth medium. Sequencing revealed that the mutation in swoF changes the conserved aspartic acid 369 to a tyrosine. The predicted A. nidulans SwoF protein, SwoFp, was homology modeled based on crystal structures of NMTs from Saccharomyces cerevisiae and Candida albicans. The D369Y swoF mutation is on the opposite face of the protein, distal to the myristoyl coenzyme A and peptide substrate binding sites. In wild-type NMTs, D369 appears to stabilize a structural beta-strand bend through two hydrogen bonds and an ionic interaction. These stabilizing bonds are abolished in the D369Y mutant. We hypothesize that a substrate of SwoFp must be myristoylated for proper polarity establishment and maintenance. The mutation prevents the proper function of SwoFp at restrictive temperature and thus blocks polar growth.
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Affiliation(s)
- Brian D Shaw
- Department of Botany, University of Georgia, Athens, Georgia 30602, USA
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Lee HH, Park JS, Chae SK, Maeng PJ, Park HM. Aspergillus nidulans sod(VI)C1 mutation causes defects in cell wall biogenesis and protein secretion. FEMS Microbiol Lett 2002; 208:253-7. [PMID: 11959445 DOI: 10.1111/j.1574-6968.2002.tb11090.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Growth at the restrictive temperature (42 degrees C) of Aspergillus nidulans B120, carrying the conditional-lethal mutation sod(VI)C1, was partially improved by the addition of 1.0 M sorbitol to the medium. The mutant grown at 42 degrees C, with osmotic stabilizer, showed abnormal hyphal morphology, a decrease in beta-1,3-glucan synthase activity as well as cell wall sugar content, but an increase in chitin synthase activity and N-acetyl-glucosamine content. The mutation also affected the secretion of extracellular protease. The temperature-dependent osmo-sensitive phenotype of a Saccharomyces cerevisiae alpha-COP mutation can be rescued by the A. nidulans sod(VI)C(+) gene. These results indicate that the sod(VI)C1 mutation affects proper processing of secretory proteins destined for the surface of cells or beyond.
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Affiliation(s)
- Hwan Hee Lee
- Department of Microbiology, College of Natural Sciences, Chungnam National University, Daejeon 305-764, South Korea
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Abstract
Fungi generally display either of two growth modes, yeast-like or filamentous, whereas dimorphic fungi, upon environmental stimuli, are able to switch between the yeast-like and the filamentous growth mode. Signal transduction pathways have been elucidated in the budding yeast Saccharomyces cerevisiae, establishing a morphogenetic network that links cell-cycle events with cellular morphogenesis. Recent molecular genetic studies in several filamentous fungal model systems revealed key components required for distinct steps from fungal spore germination to the maintenance of polar hyphal growth, mycelium formation, and nuclear division. This allows a mechanistic comparison of yeast-like and hyphal growth and the establishment of a core model morphogenetic network for filamentous growth including signaling via the cAMP pathway, Rho modules, and cell cycle kinases. Appreciating similarities between morphogenetic networks of the unicellular yeasts and the multicellular filamentous fungi will open new research directions, help in isolating the central network components, and ultimately pave the way to elucidate the central differences (of many) that distinguish, e.g., the growth mode of filamentous fungi from that of their yeast-like relatives, the role of cAMP signaling, and nuclear division.
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Affiliation(s)
- J Wendland
- Department of Microbiology, Friedrich-Schiller University, Jena, D-07745, Germany
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Khalaj V, Brookman JL, Robson GD. A study of the protein secretory pathway of Aspergillus niger using a glucoamylase-GFP fusion protein. Fungal Genet Biol 2001; 32:55-65. [PMID: 11277626 DOI: 10.1006/fgbi.2000.1245] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The effect of various treatments that block protein secretion was visualized in Aspergillus niger using a strain expressing a glucoamylase-GFP fusion protein. Cold shock caused the retention of the fusion protein in a reticulate network (ER) with brighter nodes that may represent Golgi bodies. Treatment of germlings with brefeldin A (BFA) also initially caused accumulation within the ER but prolonged exposure led to the formation and targeting of the fusion protein to vacuoles from the ER. Disruption of actin with cytochalasin A initially led to a faint diffuse accumulation and ultimately to the formation of aggregated bodies which were not vacuoles, suggesting that the actin cytoskeleton is important in secretory vesicle transport. Disruption of microtubules with nocodazole led to hyperbranching but did not cause intracellular accumulation, suggesting that microtubules play a role in directing vesicle transport rather than vesicle movement per se. Treatment of regenerating protoplasts confirmed that BFA and cytochalasin but not nocodazole inhibited protein secretion. When germlings were subjected to carbon starvation, vacuolation was rapidly initiated throughout the hyphae and GFP fluorescence was visible in some of the vacuoles, indicating retargeting of the fusion protein from the secretory pathway to the vacuoles.
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Affiliation(s)
- V Khalaj
- School of Biological Sciences, University of Manchester, 1.800 Stopford Building, Manchester, M13 9PT, United Kingdom
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The Aspergillus nidulans hfa mutations affect genomic stability and cause diverse defects in cell cycle progression and cellular morphogenesis. ACTA ACUST UNITED AC 2000. [DOI: 10.1017/s0953756200002847] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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Abstract
The knowledge base that will underpin the more efficient use of filamentous fungi as cell factories in food has increased during the past year in the areas of gene regulation, protein secretion, safety and synthesis of ingredients such as long-chain polyunsaturated fatty acids.
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Affiliation(s)
- D B Archer
- School of Life and Environmental Sciences, University of Nottingham, University Park, NG7 2RD, Nottingham, UK.
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