scholarly journals The Plastid of Toxoplasma gondii Is Divided by Association with the Centrosomes

2000 ◽  
Vol 151 (7) ◽  
pp. 1423-1434 ◽  
Author(s):  
Boris Striepen ◽  
Michael J. Crawford ◽  
Michael K. Shaw ◽  
Lewis G. Tilney ◽  
Frank Seeber ◽  
...  
Keyword(s):  
Cell Division ◽  
Toxoplasma Gondii ◽  
Genetic Manipulation ◽  
Fluorescent Proteins ◽  
Recombinant Expression ◽  
Molecular Genetic ◽  
Time Lapse ◽  
Microtubule Organization ◽  
Apicomplexan Parasites ◽  
Daughter Cells

Apicomplexan parasites harbor a single nonphotosynthetic plastid, the apicoplast, which is essential for parasite survival. Exploiting Toxoplasma gondii as an accessible system for cell biological analysis and molecular genetic manipulation, we have studied how these parasites ensure that the plastid and its 35-kb circular genome are faithfully segregated during cell division. Parasite organelles were labeled by recombinant expression of fluorescent proteins targeted to the plastid and the nucleus, and time-lapse video microscopy was used to image labeled organelles throughout the cell cycle. Apicoplast division is tightly associated with nuclear and cell division and is characterized by an elongated, dumbbell-shaped intermediate. The plastid genome is divided early in this process, associating with the ends of the elongated organelle. A centrin-specific antibody demonstrates that the ends of dividing apicoplast are closely linked to the centrosomes. Treatment with dinitroaniline herbicides (which disrupt microtubule organization) leads to the formation of multiple spindles and large reticulate plastids studded with centrosomes. The mitotic spindle and the pellicle of the forming daughter cells appear to generate the force required for apicoplast division in Toxoplasma gondii. These observations are discussed in the context of autonomous and FtsZ-dependent division of plastids in plants and algae.

scholarly journals Toxoplasma gondii myosins B/C

2001 ◽  
Vol 155 (4) ◽  
pp. 613-624 ◽  
Author(s):  
Frédéric Delbac ◽  
Astrid Sänger ◽  
Eva M. Neuhaus ◽  
Rolf Stratmann ◽  
James W. Ajioka ◽  
...  
Keyword(s):  
Cell Division ◽  
Toxoplasma Gondii ◽  
Daughter Cell ◽  
Gliding Motility ◽  
Apicomplexan Parasites ◽  
Daughter Cells ◽  
Membrane Complex ◽  
Alternatively Spliced ◽  
Butanedione Monoxime ◽  
Inner Membrane Complex

In apicomplexan parasites, actin-disrupting drugs and the inhibitor of myosin heavy chain ATPase, 2,3-butanedione monoxime, have been shown to interfere with host cell invasion by inhibiting parasite gliding motility. We report here that the actomyosin system of Toxoplasma gondii also contributes to the process of cell division by ensuring accurate budding of daughter cells. T. gondii myosins B and C are encoded by alternatively spliced mRNAs and differ only in their COOH-terminal tails. MyoB and MyoC showed distinct subcellular localizations and dissimilar solubilities, which were conferred by their tails. MyoC is the first marker selectively concentrated at the anterior and posterior polar rings of the inner membrane complex, structures that play a key role in cell shape integrity during daughter cell biogenesis. When transiently expressed, MyoB, MyoC, as well as the common motor domain lacking the tail did not distribute evenly between daughter cells, suggesting some impairment in proper segregation. Stable overexpression of MyoB caused a significant defect in parasite cell division, leading to the formation of extensive residual bodies, a substantial delay in replication, and loss of acute virulence in mice. Altogether, these observations suggest that MyoB/C products play a role in proper daughter cell budding and separation.

scholarly journals A Novel Actin-Related Protein Is Associated with Daughter Cell Formation in Toxoplasma gondii

2008 ◽  
Vol 7 (9) ◽  
pp. 1500-1512 ◽  
Author(s):  
Jennifer L. Gordon ◽  
Wandy L. Beatty ◽  
L. David Sibley
Keyword(s):  
Cell Division ◽  
Toxoplasma Gondii ◽  
Daughter Cell ◽  
Cell Formation ◽  
The Body ◽  
Apicomplexan Parasites ◽  
Daughter Cells ◽  
Membrane Complex ◽  
Transport Vesicles ◽  
Inner Membrane Complex

ABSTRACT Cell division in Toxoplasma gondii occurs by an unusual budding mechanism termed endodyogeny, during which twin daughters are formed within the body of the mother cell. Cytokinesis begins with the coordinated assembly of the inner membrane complex (IMC), which surrounds the growing daughter cells. The IMC is compiled of both flattened membrane cisternae and subpellicular filaments composed of articulin-like proteins attached to underlying singlet microtubules. While proteins that comprise the elongating IMC have been described, little is known about its initial formation. Using Toxoplasma as a model system, we demonstrate that actin-like protein 1 (ALP1) is partially redistributed to the IMC at early stages in its formation. Immunoelectron microscopy localized ALP1 to a discrete region of the nuclear envelope, on transport vesicles, and on the nascent IMC of the daughter cells prior to the arrival of proteins such as IMC-1. The overexpression of ALP1 under the control of a strong constitutive promoter disrupted the formation of the daughter cell IMC, leading to delayed growth and defects in nuclear and apicoplast segregation. Collectively, these data suggest that ALP1 participates in the formation of daughter cell membranes during cell division in apicomplexan parasites.

scholarly journals Cytokinesis and Midzone Microtubule Organization inCaenorhabditis elegans Require the Kinesin-like Protein ZEN-4

1998 ◽  
Vol 9 (8) ◽  
pp. 2037-2049 ◽  
Author(s):  
William B. Raich ◽  
Adrienne N. Moran ◽  
Joel H. Rothman ◽  
Jeff Hardin
Keyword(s):  
Cell Division ◽  
Null Allele ◽  
Time Lapse ◽  
Equatorial Region ◽  
Microtubule Organization ◽  
Dividing Cells ◽  
Spindle Midzone ◽  
Cross Links ◽  
Complete Cell

Members of the MKLP1 subfamily of kinesin motor proteins localize to the equatorial region of the spindle midzone and are capable of bundling antiparallel microtubules in vitro. Despite these intriguing characteristics, it is unclear what role these kinesins play in dividing cells, particularly within the context of a developing embryo. Here, we report the identification of a null allele ofzen-4, an MKLP1 homologue in the nematodeCaenorhabditis elegans, and demonstrate that ZEN-4 is essential for cytokinesis. Embryos deprived of ZEN-4 form multinucleate single-celled embryos as they continue to cycle through mitosis but fail to complete cell division. Initiation of the cytokinetic furrow occurs at the normal time and place, but furrow propagation halts prematurely. Time-lapse recordings and microtubule staining reveal that the cytokinesis defect is preceded by the dissociation of the midzone microtubules. We show that ZEN-4 protein localizes to the spindle midzone during anaphase and persists at the midbody region throughout cytokinesis. We propose that ZEN-4 directly cross-links the midzone microtubules and suggest that these microtubules are required for the completion of cytokinesis.

scholarly journals Changes in the Min Oscillation Pattern before and after Cell Birth

2010 ◽  
Vol 192 (16) ◽  
pp. 4134-4142 ◽  
Author(s):  
Jennifer R. Juarez ◽  
William Margolin
Keyword(s):  
Cell Division ◽  
Fluorescent Protein ◽  
Time Lapse ◽  
The Other ◽  
Cell Pole ◽  
Daughter Cells ◽  
Division Site ◽  
Before And After ◽  
Dividing Cells ◽  
Green Fluorescent

ABSTRACT The Min system regulates the positioning of the cell division site in many bacteria. In Escherichia coli, MinD migrates rapidly from one cell pole to the other. In conjunction with MinC, MinD helps to prevent unwanted FtsZ rings from assembling at the poles and to stabilize their positioning at midcell. Using time-lapse microscopy of growing and dividing cells expressing a gfp-minD fusion, we show that green fluorescent protein (GFP)-MinD often paused at midcell in addition to at the poles, and the frequency of midcell pausing increased as cells grew longer and cell division approached. At later stages of septum formation, GFP-MinD often paused specifically on only one side of the septum, followed by migration to the other side of the septum or to a cell pole. About the time of septum closure, this irregular pattern often switched to a transient double pole-to-pole oscillation in the daughter cells, which ultimately became a stable double oscillation. The splitting of a single MinD zone into two depends on the developing septum and is a potential mechanism to explain how MinD is distributed equitably to both daughter cells. Septal pausing of GFP-MinD did not require MinC, suggesting that MinC-FtsZ interactions do not drive MinD-septal interactions, and instead MinD recognizes a specific geometric, lipid, and/or protein target at the developing septum. Finally, we observed regular end-to-end oscillation over very short distances along the long axes of minicells, supporting the importance of geometry in MinD localization.

scholarly journals Daughter Cell Assembly in the Protozoan ParasiteToxoplasma gondii

2002 ◽  
Vol 13 (2) ◽  
pp. 593-606 ◽  
Author(s):  
Ke Hu ◽  
Tara Mann ◽  
Boris Striepen ◽  
Con J. M. Beckers ◽  
David S. Roos ◽  
...  
Keyword(s):  
Cell Division ◽  
Fluorescent Protein ◽  
Molecular Genetic ◽  
Inner Membrane ◽  
Apicomplexan Parasites ◽  
Membrane Complex ◽  
Ideal System ◽  
Animal Pathogens ◽  
Inner Membrane Complex

The phylum Apicomplexa includes thousands of species of obligate intracellular parasites, many of which are significant human and/or animal pathogens. Parasites in this phylum replicate by assembling daughters within the mother, using a cytoskeletal and membranous scaffolding termed the inner membrane complex. Most apicomplexan parasites, including Plasmodium sp. (which cause malaria), package many daughters within a single mother during mitosis, whereas Toxoplasma gondii typically packages only two. The comparatively simple pattern of T. gondii cell division, combined with its molecular genetic and cell biological accessibility, makes this an ideal system to study parasite cell division. A recombinant fusion between the fluorescent protein reporter YFP and the inner membrane complex protein IMC1 has been exploited to examine daughter scaffold formation in T. gondii.Time-lapse video microscopy permits the entire cell cycle of these parasites to be visualized in vivo. In addition to replication via endodyogeny (packaging two parasites at a time), T. gondii is also capable of forming multiple daughters, suggesting fundamental similarities between cell division in T. gondii and other apicomplexan parasites.

scholarly journals TgAP2IX-5 is a key transcriptional regulator of the asexual cell cycle division in Toxoplasma gondii

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Asma S. Khelifa ◽  
Cecilia Guillen Sanchez ◽  
Kevin M. Lesage ◽  
Ludovic Huot ◽  
Thomas Mouveaux ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Toxoplasma Gondii ◽  
Molecular Mechanisms ◽  
Developmental Pathways ◽  
Limiting Factor ◽  
Specific Cell ◽  
Master Regulator ◽  
Apicomplexan Parasites ◽  
Daughter Cells ◽  
Expression Program

AbstractApicomplexan parasites have evolved efficient and distinctive strategies for intracellular replication where the timing of emergence of the daughter cells (budding) is a decisive element. However, the molecular mechanisms that provide the proper timing of parasite budding remain unknown. Using Toxoplasma gondii as a model Apicomplexan, we identified a master regulator that controls the timing of the budding process. We show that an ApiAP2 transcription factor, TgAP2IX-5, controls cell cycle events downstream of centrosome duplication. TgAP2IX-5 binds to the promoter of hundreds of genes and controls the activation of the budding-specific cell cycle expression program. TgAP2IX-5 regulates the expression of specific transcription factors that are necessary for the completion of the budding cycle. Moreover, TgAP2IX-5 acts as a limiting factor that ensures that asexual proliferation continues by promoting the inhibition of the differentiation pathway. Therefore, TgAP2IX-5 is a master regulator that controls both cell cycle and developmental pathways.

scholarly journals Escape from mitotic catastrophe by actin-dependent nuclear displacement in fission yeast

2020 ◽  
Author(s):  
Masashi Yukawa ◽  
Yasuhiro Teratani ◽  
Takashi Toda
Keyword(s):  
Cell Division ◽  
Fission Yeast ◽  
Time Lapse ◽  
Mitotic Catastrophe ◽  
Nuclear Movement ◽  
Nuclear Positioning ◽  
Cell Axis ◽  
Cellular Processes ◽  
Daughter Cells ◽  
Actin Cables

SUMMARYProper nuclear positioning is essential for the execution of a wide variety of cellular processes in eukaryotic cells (Gundersen and Worman, 2013; Kopf et al., 2020; Lele et al., 2018). In proliferating mitotic cells, nuclear positioning is crucial for successful cell division. The bipolar spindle, which pulls sister chromatids towards two opposite poles, needs to assemble in the geometrical center of the cell. This ensures symmetrical positioning of the two nuclei that are reformed upon mitotic exit, by which two daughter cells inherit the identical set of the chromosomes upon cytokinesis. In fission yeast, the nucleus is positioned in the cell center during interphase; cytoplasmic microtubules interact with both the nucleus and the cell tips, thereby retaining the nucleus in the medial position of the cell (Daga et al., 2006; Tran et al., 2001). By contrast, how the nucleus is positioned during mitosis remains elusive. Here we show that several cell-cycle mutants that arrest in mitosis all displace the nucleus towards one end of the cell axis. Intriguingly, the actin cytoskeleton, not the microtubule counterpart, is responsible for the asymmetric movement of the nucleus. Time-lapse live imaging indicates that mitosis-specific F-actin cables interact with the nuclear membrane, thereby possibly generating an asymmetrical pushing force. In addition, constriction of the actomyosin ring further promotes nuclear displacement. This nuclear movement is beneficial, because if the nuclei were retained in the cell center, subsequent cell division would impose the lethal cut phenotype (Hirano et al., 1986; Yanagida, 1998), in which chromosomes are intersected by the contractile actin ring and the septum. Thus, fission yeast escapes from mitotic catastrophe by means of actin-dependent nuclear movement.

scholarly journals Structural and Functional Insights into the Microtubule Organizing Centers of Toxoplasma gondii and Plasmodium spp.

2021 ◽  
Vol 9 (12) ◽  
pp. 2503
Author(s):  
Ramiro Tomasina ◽  
Fabiana C. González ◽  
Maria E. Francia
Keyword(s):  
Cell Division ◽  
Toxoplasma Gondii ◽  
Large Body ◽  
Plasmodium Species ◽  
Single Species ◽  
Sexual Life ◽  
Cellular Functions ◽  
Microtubule Organization ◽  
Microtubule Organizing Centers ◽  
Causative Agents

Microtubule organizing centers (MTOCs) perform critical cellular tasks by nucleating, stabilizing, and anchoring microtubule’s minus ends. These capacities impact tremendously a wide array of cellular functions ranging from ascribing cell shape to orchestrating cell division and generating motile structures, among others. The phylum Apicomplexa comprises over 6000 single-celled obligate intracellular parasitic species. Many of the apicomplexan are well known pathogens such as Toxoplasma gondii and the Plasmodium species, causative agents of toxoplasmosis and malaria, respectively. Microtubule organization in these parasites is critical for organizing the cortical cytoskeleton, enabling host cell penetration and the positioning of large organelles, driving cell division and directing the formation of flagella in sexual life stages. Apicomplexans are a prime example of MTOC diversity displaying multiple functional and structural MTOCs combinations within a single species. This diversity can only be fully understood in light of each organism’s specific MT nucleation requirements and their evolutionary history. Insight into apicomplexan MTOCs had traditionally been limited to classical ultrastructural work by transmission electron microscopy. However, in the past few years, a large body of molecular insight has emerged. In this work we describe the latest insights into nuclear MTOC biology in two major human and animal disease causing Apicomplexans: Toxoplasma gondii and Plasmodium spp.

scholarly journals Sas4 links basal bodies to cell division via Hippo signaling

2020 ◽  
Vol 219 (8) ◽  
Author(s):  
Marisa D. Ruehle ◽  
Alexander J. Stemm-Wolf ◽  
Chad G. Pearson
Keyword(s):  
Cell Division ◽  
Signaling Pathway ◽  
Cortical Microtubule ◽  
Cell Cortex ◽  
Basal Bodies ◽  
Hippo Signaling ◽  
Microtubule Organization ◽  
Hippo Signaling Pathway ◽  
Daughter Cells ◽  
Striated Fiber

Basal bodies (BBs) are macromolecular complexes required for the formation and cortical positioning of cilia. Both BB assembly and DNA replication are tightly coordinated with the cell cycle to ensure their accurate segregation and propagation to daughter cells, but the mechanisms ensuring coordination are unclear. The Tetrahymena Sas4/CPAP protein is enriched at assembling BBs, localizing to the core BB structure and to the base of BB-appendage microtubules and striated fiber. Sas4 is necessary for BB assembly and cortical microtubule organization, and Sas4 loss disrupts cell division furrow positioning and DNA segregation. The Hippo signaling pathway is known to regulate cell division furrow position, and Hippo molecules localize to BBs and BB-appendages. We find that Sas4 loss disrupts localization of the Hippo activator, Mob1, suggesting that Sas4 mediates Hippo activity by promoting scaffolds for Mob1 localization to the cell cortex. Thus, Sas4 links BBs with an ancient signaling pathway known to promote the accurate and symmetric segregation of the genome.

scholarly journals Polarized endosome dynamics engage cytoplasmic Par-3 that recruits dynein during asymmetric cell division

2021 ◽  
Vol 7 (24) ◽  
pp. eabg1244
Author(s):  
Xiang Zhao ◽  
Jason Q. Garcia ◽  
Kai Tong ◽  
Xingye Chen ◽  
Bin Yang ◽  
...  
Keyword(s):  
Cell Division ◽  
Notch Signaling ◽  
Radial Glia ◽  
Asymmetric Cell Division ◽  
Protein Complexes ◽  
Time Lapse ◽  
Daughter Cells ◽  
Dynein Motor ◽  
Time Lapse Imaging

In the developing embryos, the cortical polarity regulator Par-3 is critical for establishing Notch signaling asymmetry between daughter cells during asymmetric cell division (ACD). How cortically localized Par-3 establishes asymmetric Notch activity in the nucleus is not understood. Here, using in vivo time-lapse imaging of mitotic radial glia progenitors in the developing zebrafish forebrain, we uncover that during horizontal ACD along the anteroposterior embryonic axis, endosomes containing the Notch ligand DeltaD (Dld) move toward the cleavage plane and preferentially segregate into the posterior (subsequently basal) Notchhi daughter. This asymmetric segregation requires the activity of Par-3 and dynein motor complex. Using label retention expansion microscopy, we further detect Par-3 in the cytosol colocalizing the dynein light intermediate chain 1 (Dlic1) onto Dld endosomes. Par-3, Dlic1, and Dld are associated in protein complexes in vivo. Our data reveal an unanticipated mechanism by which cytoplasmic Par-3 directly polarizes Notch signaling components during ACD.

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