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Takeshita N. Control of Actin and Calcium for Chitin Synthase Delivery to the Hyphal Tip of Aspergillus. Curr Top Microbiol Immunol 2019; 425:113-129. [PMID: 31974757 DOI: 10.1007/82_2019_193] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Filamentous fungi are covered by a cell wall consisting mainly of chitin and glucan. The synthesis of chitin, a β-1,4-linked homopolymer of N-acetylglucosamine, is essential for hyphal morphogenesis. Fungal chitin synthases are integral membrane proteins that have been classified into seven classes. ChsB, a class III chitin synthase, is known to play a key role in hyphal tip growth and has been used here as a model to understand the cell biology of cell wall biosynthesis in Aspergillus nidulans. Chitin synthases are transported on secretory vesicles to the plasma membrane for new cell wall synthesis. Super-resolution localization imaging as a powerful biophysical approach indicated dynamics of the Spitzenkörper where spatiotemporally regulated exocytosis and cell extension, whereas high-speed pulse-chase imaging has revealed ChsB transport mechanism mediated by kinesin-1 and myosin-5. In addition, live imaging analysis showed correlations among intracellular Ca2+ levels, actin assembly, and exocytosis in growing hyphal tips. This suggests that pulsed Ca2+ influxes coordinate the temporal control of actin assembly and exocytosis, which results in stepwise cell extension. It is getting clear that turgor pressure and cell wall pressure are involved in the activation of Ca2+ channels for Ca2+ oscillation and cell extension. Here the cell wall synthesis and tip growth meet again.
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Affiliation(s)
- Norio Takeshita
- Microbiology Research Center for Sustainability (MiCS), Faculty of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Japan.
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2
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Serrano A, Illgen J, Brandt U, Thieme N, Letz A, Lichius A, Read ND, Fleißner A. Spatio-temporal MAPK dynamics mediate cell behavior coordination during fungal somatic cell fusion. J Cell Sci 2018; 131:jcs.213462. [PMID: 29592970 DOI: 10.1242/jcs.213462] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2017] [Accepted: 03/20/2018] [Indexed: 01/17/2023] Open
Abstract
Mitogen-activated protein kinases (MAPKs) are conserved regulators of proliferation, differentiation and adaptation in eukaryotic cells. Their activity often involves changes in their subcellular localization, indicating an important role for these spatio-temporal dynamics in signal transmission. A striking model illustrating these dynamics is somatic cell fusion in Neurospora crassa Germinating spores of this fungus rapidly alternate between signal sending and receiving, thereby establishing a cell-cell dialog, which involves the alternating membrane recruitment of the MAPK MAK-2 in both fusion partners. Here, we show that the dynamic translocation of MAK-2 is essential for coordinating the behavior of the fusion partners before physical contact. The activation and function of the kinase strongly correlate with its subcellular localization, indicating a crucial contribution of the MAPK dynamics in establishing regulatory feedback loops, which establish the oscillatory signaling mode. In addition, we provide evidence that MAK-2 not only contributes to cell-cell communication, but also mediates cell-cell fusion. The MAK-2 dynamics significantly differ between these two processes, suggesting a role for the MAPK in switching of the cellular program between communication and fusion.
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Affiliation(s)
- Antonio Serrano
- Institut für Genetik, Technische Universität Braunschweig, Spielmannstraße 7, 38106 Braunschweig, Germany
| | - Julia Illgen
- Institut für Genetik, Technische Universität Braunschweig, Spielmannstraße 7, 38106 Braunschweig, Germany
| | - Ulrike Brandt
- Institut für Genetik, Technische Universität Braunschweig, Spielmannstraße 7, 38106 Braunschweig, Germany
| | - Nils Thieme
- Institut für Genetik, Technische Universität Braunschweig, Spielmannstraße 7, 38106 Braunschweig, Germany
| | - Anja Letz
- Institut für Genetik, Technische Universität Braunschweig, Spielmannstraße 7, 38106 Braunschweig, Germany
| | - Alexander Lichius
- Institute of Microbiology, University of Innsbruck, 6020 Innsbruck, Austria
| | - Nick D Read
- Manchester Fungal Infection Group, Division of Infection, Immunity and Respiratory Medicine, University of Manchester, Manchester M13 9NT, UK
| | - André Fleißner
- Institut für Genetik, Technische Universität Braunschweig, Spielmannstraße 7, 38106 Braunschweig, Germany
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3
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Aharoni-Kats L, Zelinger E, Chen S, Yarden O. Altering Neurospora crassa MOB2A exposes its functions in development and affects its interaction with the NDR kinase COT1. Mol Microbiol 2018; 108:641-660. [PMID: 29600559 DOI: 10.1111/mmi.13954] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/15/2018] [Indexed: 12/30/2022]
Abstract
The Neurospora crassa Mps One Binder (MOB) proteins MOB2A and MOB2B physically interact with the Nuclear Dbf2 Related (NDR) kinase COT1 and have been shown to have overlapping functions in various aspects of asexual development. Here, we identified two N. crassa MOB2A residues, Tyr117 and Tyr119, which are potentially phosphorylated. Using phosphomimetic mob-2a mutants we have been able to establish that apart from their previously described roles, MOB2A/B are involved in additional developmental processes. Enhanced conidial germination, accompanied by conidial agglutination, in the phosphomimetic mutants indicated that MOB2A is a negative regulator of germination. Thick-section imaging of perithecia revealed slow maturation and a lack of asci alignment in the mutant strains demonstrating a role for MOB2A in sexual development. We demonstrate that even though MOB2A and MOB2B have some overlapping functions, MOB2B cannot compensate for the roles MOB2A has in conidiation and germination. Altering Tyr residues 117 and 119 impaired the physical interactions between MOB2A and COT1, most likely contributing to some of the observed effects. As cot-1 and the phosphomimetic mutants share an extragenic suppressor (gul-1), we concluded that at least some of the effects imposed by altering Tyr117 and Tyr119 are mediated by the NDR kinase.
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Affiliation(s)
- Liran Aharoni-Kats
- Department of Plant Pathology and Microbiology, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot 7610000, Israel
| | - Einat Zelinger
- Centre for Scientific Imaging, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot 7610000, Israel
| | - She Chen
- Proteomics Centre, The National Institute of Biological Sciences, Beijing 102206, China
| | - Oded Yarden
- Department of Plant Pathology and Microbiology, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot 7610000, Israel
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4
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Oscillatory fungal cell growth. Fungal Genet Biol 2017; 110:10-14. [PMID: 29229585 DOI: 10.1016/j.fgb.2017.12.002] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2017] [Revised: 11/26/2017] [Accepted: 12/06/2017] [Indexed: 12/20/2022]
Abstract
Cells are dynamic systems, the state of which undergoes constant alteration that results in morphological changes and movement. Many dynamic cellular processes that appear continuous are driven by underlying mechanisms that oscillate with distinct periods. For example eukaryotic cells do not grow continuously, but rather by pulsed extension of the periphery. Stepwise cell extension at the hyphal tips of several filamentous fungi was discovered 20 years ago, but only a few molecular details of the mechanism have been clarified since then. A recent study has provided evidence for correlations among intracellular Ca2+ levels, actin assembly, exocytosis and cell extension in growing hyphal tips. This suggests that pulsed Ca2+ influxes coordinate the temporal control of actin assembly and exocytosis, which results in stepwise cell extension. The coordinated oscillation of these machineries are likely to be ubiquitous among all eukaryotes. Indeed, intracellular Ca2+ levels and/or actin polymerization oscillate in mammalian and plant cells. This review summarizes the mechanisms of oscillation in several systems.
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Zhao X, Spraker JE, Bok JW, Velk T, He ZM, Keller NP. A Cellular Fusion Cascade Regulated by LaeA Is Required for Sclerotial Development in Aspergillus flavus. Front Microbiol 2017; 8:1925. [PMID: 29051754 PMCID: PMC5633613 DOI: 10.3389/fmicb.2017.01925] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2017] [Accepted: 09/21/2017] [Indexed: 11/13/2022] Open
Abstract
Aspergillus flavus is a saprophytic soil fungus that poses a serious threat worldwide as it contaminates many food and feed crops with the carcinogenic mycotoxin called aflatoxin. This pathogen persists as sclerotia in the soil which enables fungal survival in harsh environmental conditions. Sclerotia formation by A. flavus depends on successful cell communication and hyphal fusion events. Loss of LaeA, a conserved developmental regulator in fungi, abolishes sclerotia formation in this species whereas overexpression (OE) of laeA results in enhanced sclerotia production. Here we demonstrate that sclerotia loss and inability to form heterokaryons in A. flavusΔlaeA is mediated by homologs of the Neurospora crassa ham (hyphal anastomosis) genes termed hamE-I in A. flavus. LaeA positively regulates ham gene expression and deletion of hamF, G, H, or I phenocopies ΔlaeA as demonstrated by heterokaryon and sclerotia loss and reduced aflatoxin synthesis and virulence of these mutants. Deletion of hamE showed a less severe phenotype. hamE-I homologs are positively regulated by the clock controlled transcription factor ADV-1 in N. crassa. Similarly, the ADV-1 homolog NosA regulates hamE-I expression in A. flavus, is required for sclerotial development and is itself positively regulated by LaeA. We speculate that a putative LaeA>NosA>fusion cascade underlies the previously described circadian clock regulation of sclerotia production in A. flavus.
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Affiliation(s)
- Xixi Zhao
- School of Life Sciences, Sun Yat-sen University, Guangzhou, China.,Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, WI, United States
| | - Joseph E Spraker
- Department of Plant Pathology, University of Wisconsin-Madison, Madison, WI, United States
| | - Jin Woo Bok
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, WI, United States
| | - Thomas Velk
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, WI, United States
| | - Zhu-Mei He
- School of Life Sciences, Sun Yat-sen University, Guangzhou, China
| | - Nancy P Keller
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, WI, United States.,Department of Bacteriology, University of Wisconsin-Madison, Madison, WI, United States
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