Regulation of Pathogenic Spore Germination by CgRac1 in the Fungal Plant Pathogen Colletotrichum gloeosporioides

ABSTRACT Colletotrichum gloeosporioides is a facultative plant pathogen: it can live as a saprophyte on dead organic matter or as a pathogen on a host plant. Different patterns of conidial germination have been recognized under saprophytic and pathogenic conditions, which also determine later development. Here we describe the role of CgRac1 in regulating pathogenic germination. The hallmark of pathogenic germination is unilateral formation of a single germ tube following the first cell division. However, transgenic strains expressing a constitutively active CgRac1 (CA-CgRac1) displayed simultaneous formation of two germ tubes, with nuclei continuing to divide in both cells after the first cell division. CA-CgRac1 also caused various other abnormalities, including difficulties in establishing and maintaining cell polarity, reduced conidial and hyphal adhesion, and formation of immature appressoria. Consequently, CA-CgRac1 isolates were completely nonpathogenic. Localization studies with cyan fluorescent protein (CFP)-CgRac1 fusion protein showed that the CgRac1 protein is abundant in conidia and in hyphal tips. Although the CFP signal was equally distributed in both cells of a germinating conidium, reactive oxygen species accumulated only in the cell that produced a germ tube, indicating that CgRac1 was active only in the germinating cell. Collectively, our results show that CgRac1 is a major regulator of asymmetric development and that it is involved in the regulation of both morphogenesis and nuclear division. Modification of CgRac1 activity disrupts the morphogenetic program and prevents fungal infection.

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The Septin AspB in Aspergillus nidulans Forms Bars and Filaments and Plays Roles in Growth Emergence and Conidiation

Eukaryotic Cell ◽

10.1128/ec.05164-11 ◽

2012 ◽

Vol 11 (3) ◽

pp. 311-323 ◽

Cited By ~ 44

Author(s):

Yainitza Hernández-Rodríguez ◽

Susan Hastings ◽

Michelle Momany

Keyword(s):

Aspergillus Nidulans ◽

Filamentous Fungi ◽

Germ Tube ◽

Fluorescent Protein ◽

Early Growth ◽

Content Type ◽

Green Fluorescent ◽

And Function ◽

Cytoskeletal Elements ◽

Germ Tubes

ABSTRACTIn yeast, septins form rings at the mother-bud neck and function as diffusion barriers. In animals, septins form filaments that can colocalize with other cytoskeletal elements. In the filamentous fungusAspergillus nidulansthere are five septin genes,aspA(an ortholog ofSaccharomyces cerevisiae CDC11),aspB(an ortholog ofS. cerevisiae CDC3),aspC(an ortholog ofS. cerevisiae CDC12),aspD(an ortholog ofS. cerevisiae CDC10), andaspE(found only in filamentous fungi). TheaspBgene was previously reported to be the most highly expressedAspergillus nidulansseptin and to be essential. Using improved gene targeting techniques, we found that deletion ofaspBis not lethal but results in delayed septation, increased emergence of germ tubes and branches, and greatly reduced conidiation. We also found that AspB-green fluorescent protein (GFP) localizes as rings and collars at septa, branches, and emerging layers of the conidiophore and as bars and filaments in conidia and hyphae. Bars are found in dormant and isotropically expanding conidia and in subapical nongrowing regions of hyphae and display fast movements. Filaments form as the germ tube emerges, localize to hyphal and branch tips, and display slower movements. All visible AspB-GFP structures are retained inΔaspDand lost inΔaspAandΔaspCstrains. Interestingly, in theΔaspEmutant, AspB-GFP rings, bars, and filaments are visible in early growth, but AspB-GFP rods and filaments disappear after septum formation. AspE orthologs are only found in filamentous fungi, suggesting that this class of septins might be required for stability of septin bars and filaments in highly polar cells.

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Bacteriophage SP01 Gene Product 56 Inhibits Bacillus subtilis Cell Division by Interacting with FtsL and Disrupting Pbp2B and FtsW Recruitment

Journal of Bacteriology ◽

10.1128/jb.00463-20 ◽

2020 ◽

Vol 203 (2) ◽

pp. e00463-20

Author(s):

Amit Bhambhani ◽

Isabella Iadicicco ◽

Jules Lee ◽

Syed Ahmed ◽

Max Belfatto ◽

...

Keyword(s):

Cell Wall ◽

Bacillus Subtilis ◽

Cell Division ◽

Gene Product ◽

Fluorescent Protein ◽

Lytic Bacteriophage ◽

Cell Wall Synthesis ◽

Content Type ◽

Ftsz Ring ◽

Green Fluorescent

ABSTRACTPrevious work identified gene product 56 (gp56), encoded by the lytic bacteriophage SP01, as being responsible for inhibition of Bacillus subtilis cell division during its infection. Assembly of the essential tubulin-like protein FtsZ into a ring-shaped structure at the nascent site of cytokinesis determines the timing and position of division in most bacteria. This FtsZ ring serves as a scaffold for recruitment of other proteins into a mature division-competent structure permitting membrane constriction and septal cell wall synthesis. Here, we show that expression of the predicted 9.3-kDa gp56 of SP01 inhibits later stages of B. subtilis cell division without altering FtsZ ring assembly. Green fluorescent protein-tagged gp56 localizes to the membrane at the site of division. While its localization does not interfere with recruitment of early division proteins, gp56 interferes with the recruitment of late division proteins, including Pbp2b and FtsW. Imaging of cells with specific division components deleted or depleted and two-hybrid analyses suggest that gp56 localization and activity depend on its interaction with FtsL. Together, these data support a model in which gp56 interacts with a central part of the division machinery to disrupt late recruitment of the division proteins involved in septal cell wall synthesis.IMPORTANCE Studies over the past decades have identified bacteriophage-encoded factors that interfere with host cell shape or cytokinesis during viral infection. The phage factors causing cell filamentation that have been investigated to date all act by targeting FtsZ, the conserved prokaryotic tubulin homolog that composes the cytokinetic ring in most bacteria and some groups of archaea. However, the mechanisms of several phage factors that inhibit cytokinesis, including gp56 of bacteriophage SP01 of Bacillus subtilis, remain unexplored. Here, we show that, unlike other published examples of phage inhibition of cytokinesis, gp56 blocks B. subtilis cell division without targeting FtsZ. Rather, it utilizes the assembled FtsZ cytokinetic ring to localize to the division machinery and to block recruitment of proteins needed for septal cell wall synthesis.

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Landscape of Resistance-Nodulation-Cell Division (RND)-Type Efflux Pumps in Enterobacter cloacae Complex

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.02840-15 ◽

2016 ◽

Vol 60 (4) ◽

pp. 2373-2382 ◽

Cited By ~ 19

Author(s):

François Guérin ◽

Claire Lallement ◽

Christophe Isnard ◽

Anne Dhalluin ◽

Vincent Cattoir ◽

...

Keyword(s):

Cell Division ◽

Antimicrobial Resistance ◽

Galleria Mellonella ◽

Acquired Resistance ◽

Enterobacter Cloacae ◽

Efflux Pumps ◽

Wild Type ◽

Content Type ◽

Active Efflux

ABSTRACTIn Gram-negative bacteria, the active efflux is an important mechanism of antimicrobial resistance, but little is known about theEnterobacter cloacaecomplex (ECC). It is mediated primarily by pumps belonging to the RND (resistance-nodulation-cell division) family, and only AcrB, part of the AcrAB-TolC tripartite system, was characterized in ECC. However, detailed genome sequence analysis of the strainE. cloacaesubsp.cloacaeATCC 13047 revealed to us that 10 other genes putatively coded for RND-type transporters. We then characterized the role of all of these candidates by construction of corresponding deletion mutants, which were tested for their antimicrobial susceptibility to 36 compounds, their virulence in the invertebrateGalleria mellonellamodel of infection, and their ability to form biofilm. Only the ΔacrBmutant displayed significantly different phenotypes compared to that of the wild-type strain: 4- to 32-fold decrease of MICs of several antibiotics, antiseptics, and dyes, increased production of biofilm, and attenuated virulence inG. mellonella. In order to identify specific substrates of each pump, we individually expressed intransall operons containing an RND pump-encoding gene into the ΔacrBhypersusceptible strain. We showed that three other RND-type efflux systems (ECL_00053-00055, ECL_01758-01759, and ECL_02124-02125) were able to partially restore the wild-type phenotype and to superadd to and even enlarge the broad range of antimicrobial resistance. This is the first global study assessing the role of all RND efflux pumps chromosomally encoded by the ECC, which confirms the major role of AcrB in both pathogenicity and resistance and the potential involvement of other RND-type members in acquired resistance.

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Neurospora crassa NKIN2, a Kinesin-3 Motor, Transports Early Endosomes and Is Required for Polarized Growth

Eukaryotic Cell ◽

10.1128/ec.00081-13 ◽

2013 ◽

Vol 12 (7) ◽

pp. 1020-1032 ◽

Cited By ~ 29

Author(s):

Constanze Seidel ◽

Sergio David Moreno-Velásquez ◽

Meritxell Riquelme ◽

Reinhard Fischer

Keyword(s):

Neurospora Crassa ◽

Fluorescent Protein ◽

Early Endosome ◽

Mechanical Forces ◽

Structural Components ◽

Content Type ◽

Early Endosomes ◽

Polarized Cells ◽

Green Fluorescent

ABSTRACT Biological motors are molecular nanomachines, which convert chemical energy into mechanical forces. The combination of mechanoenzymes with structural components, such as the cytoskeleton, enables eukaryotic cells to overcome entropy, generate molecular gradients, and establish polarity. Hyphae of filamentous fungi are among the most polarized cells, and polarity defects are most obvious. Here, we studied the role of the kinesin-3 motor, NKIN2, in Neurospora crassa . We found that NKIN2 localizes as fast-moving spots in the cytoplasm of mature hyphae. To test whether the spots represented early endosomes, the Rab5 GTPase YPT52 was used as an endosomal marker. NKIN2 colocalized with YPT52. Deletion of nkin2 caused strongly reduced endosomal movement. Combined, these results confirm the involvement of NKIN2 in early endosome transport. Introduction of a rigor mutation into NKIN2 labeled with green fluorescent protein (GFP) resulted in decoration of microtubules. Interestingly, NKIN2 rigor was associated with a subpopulation of microtubules, as had been shown earlier for the Aspergillus nidulans orthologue UncA. Other kinesins did not show this specificity.

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F-Actin Dynamics in Neurospora crassa

Eukaryotic Cell ◽

10.1128/ec.00253-09 ◽

2010 ◽

Vol 9 (4) ◽

pp. 547-557 ◽

Cited By ~ 107

Author(s):

Adokiye Berepiki ◽

Alexander Lichius ◽

Jun-Ya Shoji ◽

Jens Tilsner ◽

Nick D. Read

Keyword(s):

Neurospora Crassa ◽

Live Cell Imaging ◽

Cell Imaging ◽

Fluorescent Protein ◽

Live Cell ◽

Actin Dynamics ◽

Actin Binding ◽

Content Type ◽

Actin Cables ◽

Germ Tubes

ABSTRACT This study demonstrates the utility of Lifeact for the investigation of actin dynamics in Neurospora crassa and also represents the first report of simultaneous live-cell imaging of the actin and microtubule cytoskeletons in filamentous fungi. Lifeact is a 17-amino-acid peptide derived from the nonessential Saccharomyces cerevisiae actin-binding protein Abp140p. Fused to green fluorescent protein (GFP) or red fluorescent protein (TagRFP), Lifeact allowed live-cell imaging of actin patches, cables, and rings in N. crassa without interfering with cellular functions. Actin cables and patches localized to sites of active growth during the establishment and maintenance of cell polarity in germ tubes and conidial anastomosis tubes (CATs). Recurrent phases of formation and retrograde movement of complex arrays of actin cables were observed at growing tips of germ tubes and CATs. Two populations of actin patches exhibiting slow and fast movement were distinguished, and rapid (1.2 μm/s) saltatory transport of patches along cables was observed. Actin cables accumulated and subsequently condensed into actin rings associated with septum formation. F-actin organization was markedly different in the tip regions of mature hyphae and in germ tubes. Only mature hyphae displayed a subapical collar of actin patches and a concentration of F-actin within the core of the Spitzenkörper. Coexpression of Lifeact-TagRFP and β-tubulin–GFP revealed distinct but interrelated localization patterns of F-actin and microtubules during the initiation and maintenance of tip growth.

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Functional Characterization of a New Member of the Cdk9 Family in Aspergillus nidulans

Eukaryotic Cell ◽

10.1128/ec.00384-09 ◽

2010 ◽

Vol 9 (12) ◽

pp. 1901-1912 ◽

Cited By ~ 5

Author(s):

Friederike Bathe ◽

Claudia Kempf ◽

Stephen A. Osmani ◽

Aysha H. Osmani ◽

Sabrina Hettinger ◽

...

Keyword(s):

Aspergillus Nidulans ◽

Fluorescent Protein ◽

Transcription Elongation ◽

Functional Characterization ◽

Asexual Development ◽

Full Spectrum ◽

Content Type ◽

Essential Components

ABSTRACT Cdk9-like kinases in complex with T-type cyclins are essential components of the eukaryotic transcription elongation machinery. The full spectrum of Cdk9/cyclin T targets, as well as the specific consequences of phosphorylations, is still largely undefined. We identify and characterize here a Cdk9 kinase (PtkA) in the filamentous ascomycete Aspergillus nidulans. Deletion of ptkA had a lethal effect in later stages of vegetative growth and completely impeded asexual development. Overexpression of ptkA affected directionality of polarized growth and the initiation of new branching sites. A green fluorescent protein-tagged PtkA version localized inside the nucleus during interphase, supporting a role of PtkA in transcription elongation, as observed in other organisms. We also identified a putative cyclin T homolog, PchA, in the A. nidulans genome and confirmed its interaction with PtkA in vivo. Surprisingly, the Pcl-like cyclin PclA, previously described to be involved in asexual development, was also found to interact with PtkA, indicating a possible role of PtkA in linking transcriptional activity with development and/or morphogenesis in A. nidulans. This is the first report of a Cdk9 kinase interacting with a Pcl-like cyclin, revealing interesting new aspects about the involvement of this Cdk-subfamily in differential gene expression.

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Visualization of Periplasmic and Cytoplasmic Proteins with a Self-Labeling Protein Tag

Journal of Bacteriology ◽

10.1128/jb.00864-15 ◽

2016 ◽

Vol 198 (7) ◽

pp. 1035-1043 ◽

Cited By ~ 35

Author(s):

Na Ke ◽

Dirk Landgraf ◽

Johan Paulsson ◽

Mehmet Berkmen

Keyword(s):

Escherichia Coli ◽

Fluorescent Protein ◽

Fluorescent Proteins ◽

Living Cells ◽

Functional Protein ◽

Content Type ◽

Additional Tool

ABSTRACTThe use of fluorescent and luminescent proteins in visualizing proteins has become a powerful tool in understanding molecular and cellular processes within living organisms. This success has resulted in an ever-increasing demand for new and more versatile protein-labeling tools that permit light-based detection of proteins within living cells. In this report, we present data supporting the use of the self-labeling HaloTag protein as a light-emitting reporter for protein fusions within the model prokaryoteEscherichia coli. We show that functional protein fusions of the HaloTag can be detected bothin vivoandin vitrowhen expressed within the cytoplasmic or periplasmic compartments ofE. coli. The capacity to visually detect proteins localized in various prokaryotic compartments expands today's molecular biologist toolbox and paves the path to new applications.IMPORTANCEVisualizing proteins microscopically within living cells is important for understanding both the biology of cells and the role of proteins within living cells. Currently, the most common tool is green fluorescent protein (GFP). However, fluorescent proteins such as GFP have many limitations; therefore, the field of molecular biology is always in need of new tools to visualize proteins. In this paper, we demonstrate, for the first time, the use of HaloTag to visualize proteins in two different compartments within the model prokaryoteEscherichia coli. The use of HaloTag as an additional tool to visualize proteins within prokaryotes increases our capacity to ask about and understand the role of proteins within living cells.

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Cell division in Aspergillus

Journal of Cell Science ◽

10.1242/jcs.103.3.599 ◽

1992 ◽

Vol 103 (3) ◽

pp. 599-611 ◽

Cited By ~ 3

Author(s):

J.H. Doonan

Keyword(s):

Cell Division ◽

Aspergillus Nidulans ◽

Molecular Analysis ◽

Filamentous Fungus ◽

Nuclear Division ◽

Mutational Analysis ◽

Cytoskeletal Proteins ◽

Nuclear Movement ◽

Cellular Analysis

Amenable to sophisticated genetic and molecular analysis, the simple filamentous fungus Aspergillus nidulans has provided some novel insights into the mechanisms and regulation of cell division. Mutational analysis has identified over fifty genes necessary for nuclear division, nuclear movement and cytokinesis. Molecular and cellular analysis of these mutants has led to the discovery of novel components of the cytoskeleton as well as to clarifying the role of established cytoskeletal proteins. Mutations leading to defects in the kinases (i.e. p34cdc2) and phosphatases (i.e. cdc25 and PP1), which are known to regulate mitosis in other eukaryotes, have been identified in Aspergillus. Additional, as yet novel, mitotic regulatory molecules, encoded by the nimA and bimE genes, have also been discovered in Aspergillus.

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Pachytene arrest and other meiotic effects of the start mutations in Saccharomyces cerevisiae.

Genetics ◽

10.1093/genetics/123.1.29 ◽

1989 ◽

Vol 123 (1) ◽

pp. 29-43 ◽

Cited By ~ 1

Author(s):

E O Shuster ◽

B Byers

Keyword(s):

Cell Division ◽

Nuclear Division ◽

Spindle Pole Body ◽

Mitotic Cell ◽

Spindle Pole ◽

Mitotic Cell Cycle ◽

Chromosomal Dna ◽

Pole Body ◽

Vegetative Cycle

Abstract Mutations in the Start class of cell division cycle genes (CDC28, CDC36 and CDC39) define the point in the G1 phase of the vegetative cycle at which the cell becomes committed to completing another round of cell division. Genetic, cytological and biochemical data demonstrate that these mutations cause meiotic cells to become arrested at pachytene following completion of both chromosomal DNA replication and spindle pole body (SPB) duplication. In contrast these mutations have previously been found to cause arrest of the mitotic cell cycle prior to either of these landmark events, so the role of the Start genes in these events during vegetative growth must be indirect. Our observations are consistent with the hypothesis that CDC28, CDC36 and CDC39 are required for irreversible commitment to nuclear division in both the mitotic and meiotic pathways. CDC28 was additionally found to be required for the SPB separation that precedes spindle formation in preparation for the second meiotic division. Cytological and genetic analyses of this requirement revealed both that such separation may fail independently at either SPB and that ascospore formation can proceed independently of SPB separation.

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Peptidoglycan Synthesis Machinery in Agrobacterium tumefaciens During Unipolar Growth and Cell Division

mBio ◽

10.1128/mbio.01219-14 ◽

2014 ◽

Vol 5 (3) ◽

Cited By ~ 38

Author(s):

Todd A. Cameron ◽

James Anderson-Furgeson ◽

John R. Zupan ◽

Justin J. Zik ◽

Patricia C. Zambryski

Keyword(s):

Cell Division ◽

Agrobacterium Tumefaciens ◽

Fluorescent Protein ◽

Polar Growth ◽

Growth Strategies ◽

Cell Width ◽

Content Type ◽

E Coli ◽

Cell Compartments ◽

New Material

ABSTRACT The synthesis of peptidoglycan (PG) in bacteria is a crucial process controlling cell shape and vitality. In contrast to bacteria such as Escherichia coli that grow by dispersed lateral insertion of PG, little is known of the processes that direct polar PG synthesis in other bacteria such as the Rhizobiales. To better understand polar growth in the Rhizobiales Agrobacterium tumefaciens, we first surveyed its genome to identify homologs of (~70) well-known PG synthesis components. Since most of the canonical cell elongation components are absent from A. tumefaciens, we made fluorescent protein fusions to other putative PG synthesis components to assay their subcellular localization patterns. The cell division scaffolds FtsZ and FtsA, PBP1a, and a Rhizobiales- and Rhodobacterales-specific l,d-transpeptidase (LDT) all associate with the elongating cell pole. All four proteins also localize to the septum during cell division. Examination of the dimensions of growing cells revealed that new cell compartments gradually increase in width as they grow in length. This increase in cell width is coincident with an expanded region of LDT-mediated PG synthesis activity, as measured directly through incorporation of exogenous d-amino acids. Thus, unipolar growth in the Rhizobiales is surprisingly dynamic and represents a significant departure from the canonical growth mechanism of E. coli and other well-studied bacilli. IMPORTANCE Many rod-shaped bacteria, including pathogens such as Brucella and Mycobacteriu, grow by adding new material to their cell poles, and yet the proteins and mechanisms contributing to this process are not yet well defined. The polarly growing plant pathogen Agrobacterium tumefaciens was used as a model bacterium to explore these polar growth mechanisms. The results obtained indicate that polar growth in this organism is facilitated by repurposed cell division components and an otherwise obscure class of alternative peptidoglycan transpeptidases (l,d-transpeptidases). This growth results in dynamically changing cell widths as the poles expand to maturity and contrasts with the tightly regulated cell widths characteristic of canonical rod-shaped growth. Furthermore, the abundance and/or activity of l,d-transpeptidases appears to associate with polar growth strategies, suggesting that these enzymes may serve as attractive targets for specifically inhibiting growth of Rhizobiales, Actinomycetales, and other polarly growing bacterial pathogens.

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