Monoplastidy in spermatogenesis of Lycopodium obscurum

1994 ◽  
Vol 72 (10) ◽  
pp. 1436-1444 ◽  
Author(s):  
Karen Sue Renzaglia ◽  
Angel R. Maden ◽  
Jeffrey G. Duckett ◽  
Dean P. Whittier
Keyword(s):  
Endoplasmic Reticulum ◽  
Key Words ◽  
Mother Cell ◽  
Annulate Lamellae ◽  
Microtubule Organizing Center ◽  
Microtubule Organizing Centers ◽  
Cell Divisions ◽  
Organizing Center ◽  
Spindle Microtubules ◽  
Spindle Development

Unlike Lycopodium laterale, which is polyplastidic during spermatogenesis, Lycopodium obscurum exhibits monoplastidy beginning in the early proliferative stages of antheridial development. Previous cell generations are polyplastidic and plastid fusion involving connective cylinders establishes the monoplastidic condition. Plastid and nuclear divisions are coordinated in L. obscurum with the plastids positioned at opposite poles prior to spindle development. Unlike monoplastidic cell divisions with morphogenetic plastid migration and polarity in other lycophytes, mosses, and hornworts, however, the spindles in L. obscurum do not originate from the plastid envelopes but from endoplasmic reticulum positioned against the plastid. In the final divisions, spindle microtubules emanate from structurally defined microtubule organizing centers that develop between the plastids and nucleus. Preceding the appearance of centrioles in the spermatid mother cell, the centrosomes comprise electron-dense granular matrices with associated vesicles and endoplasmic reticulum. Among archegoniate microtubule organizing centers, the discrete acentriolar centrosomes of Lycopodium most closely resemble the microtubule organizing centers in moss spore development and the polar organizer of liverwort mitosis. Key words: annulate lamellae, centrosome, Lycopodium, microtubule organizing center, monoplastidy, plastid dividing ring.

scholarly journals Centrosomal and Non-Centrosomal Microtubule-Organizing Centers (MTOCs) in Drosophila melanogaster

Cells ◽  
2018 ◽  
Vol 7 (9) ◽  
pp. 121 ◽  
Author(s):  
Marisa Tillery ◽  
Caitlyn Blake-Hedges ◽  
Yiming Zheng ◽  
Rebecca Buchwalter ◽  
Timothy Megraw
Keyword(s):  
Current Knowledge ◽  
Cell Types ◽  
Wing Disc ◽  
Early Embryo ◽  
Microtubule Organizing Center ◽  
Drosophila Development ◽  
Functional Roles ◽  
Animal Development ◽  
Microtubule Organizing Centers ◽  
Organizing Center

The centrosome is the best-understood microtubule-organizing center (MTOC) and is essential in particular cell types and at specific stages during Drosophila development. The centrosome is not required zygotically for mitosis or to achieve full animal development. Nevertheless, centrosomes are essential maternally during cleavage cycles in the early embryo, for male meiotic divisions, for efficient division of epithelial cells in the imaginal wing disc, and for cilium/flagellum assembly in sensory neurons and spermatozoa. Importantly, asymmetric and polarized division of stem cells is regulated by centrosomes and by the asymmetric regulation of their microtubule (MT) assembly activity. More recently, the components and functions of a variety of non-centrosomal microtubule-organizing centers (ncMTOCs) have begun to be elucidated. Throughout Drosophila development, a wide variety of unique ncMTOCs form in epithelial and non-epithelial cell types at an assortment of subcellular locations. Some of these cell types also utilize the centrosomal MTOC, while others rely exclusively on ncMTOCs. The impressive variety of ncMTOCs being discovered provides novel insight into the diverse functions of MTOCs in cells and tissues. This review highlights our current knowledge of the composition, assembly, and functional roles of centrosomal and non-centrosomal MTOCs in Drosophila.

scholarly journals Ultrastructural immunocytochemical localization of calmodulin in cultured cells.

1983 ◽  
Vol 31 (4) ◽  
pp. 445-461 ◽  
Author(s):  
M C Willingham ◽  
J Wehland ◽  
C B Klee ◽  
N D Richert ◽  
A V Rutherford ◽  
...  
Keyword(s):  
Cultured Cells ◽  
Performic Acid ◽  
Microtubule Organizing Center ◽  
Interphase Cells ◽  
Organizing Center ◽  
Late Telophase ◽  
Cytoplasmic Microtubules ◽  
Spindle Microtubules ◽  
And Function ◽  
Fibroblastic Cells

Using an antibody prepared against performic acid-treated calmodulin, we have localized calmodulin in cultured fibroblastic cells by immunofluorescence and immunoelectron microscopy. In interphase cells, calmodulin was found to be diffusely distributed throughout the cytosol. An increased amount of calmodulin was found in the pericentriolar region of interphase cells. No significant aggregation of calmodulin was found in association with microfilaments, peripheral cytoplasmic microtubules or clathrin-coated structures. Calmodulin was present in moderate amounts in microvilli, ruffles, and zeiotic blebs of the cell surface. In motitic cells, calmodulin was found concentrated in the pericentriolar region, and appeared to concentrate along radiating spindle microtubules proximal to the centrioles. Redistribution of calmodulin was seen between early and late telophase, in which the pericentriolar pattern of calmodulin in early telophase shifted to an aggregation on the intercellular bridge, with a large part of the midbody portion of the bridge being devoid of calmodulin. These results show that calmodulin is distributed throughout the cytosol, but is markedly concentrated in the region of the microtubule organizing center in interphase cells, as well as in elements of the mitotic spindle apparatus. This distribution suggests that calmodulin has a regulatory role in the organization and function of microtubules during interphase, as well as during mitosis.

Cytological variation in zoospores of Spizellomyces (Chytridiomycetes)

1984 ◽  
Vol 62 (6) ◽  
pp. 1202-1208 ◽  
Author(s):  
Donald J. S. Barr
Keyword(s):  
Endoplasmic Reticulum ◽  
Microtubule Organizing Center ◽  
Fibrillar Material ◽  
Organizing Center ◽  
Cytological Features ◽  
Cytological Characteristics

The principal cytological features and their variations are described in zoospores of 38 isolates belonging to seven species of Spizellomyces. This genus is distinguished from others in the Spizellomycetaceae by the orientation of the microtubules and the position of the nucleus relative to the kinetosome in the zoospore. Microtubules run apparently at random into the cytoplasm from a microtubule-organizing center (spur) on one side of the kinetosome. The nucleus is anteriorly or centrally positioned with a heel-like process extending to near the proximal face of the kinetosome, or it can be posteriorly positioned and elongate with one end close to the kinetosome. Differences between species are reflected by the position and shape of the nucleus, the extent of the endoplasmic reticulum which in some species circumscribes lipid globules, the presence or absence of an apparent connection by fibrillar material between the kinetosome and a nonfunctional centriole, and the morphology of the microtubule-organizing center. The zoospores of Spizellomyces punctatus (Koch) D. Barr, S. plurigibbosus (D. Barr) D. Barr, and S. palustris (Gaertner) D. Barr are cytologically similar, but those of S. acuminatus (D. Barr) D. Barr, S. dolichospermus D. Barr, S. lactosolyticus D. Barr and S. pseudodichotomus (Umphlett) D. Barr each have one or more distinctive characteristic. Spizellomyces dolichospermus and S. pseudodichotomus also have some cytological characteristics in common with the genus Kochiomyces.

scholarly journals The centriolar satellite protein Cfap53/Ccdc11 facilitates the formation of the first zygotic microtubule organizing center in the zebrafish embryo

2020 ◽  
Author(s):  
Sven Willekers ◽  
Federico Tessadori ◽  
Babet van der Vaart ◽  
Heiko Henning ◽  
Riccardo Stucchi ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Danio Rerio ◽  
Mitotic Spindle ◽  
Sperm Cell ◽  
Zebrafish Embryo ◽  
Animal Species ◽  
Microtubule Organizing Center ◽  
Microtubule Network ◽  
Cell Divisions ◽  
Organizing Center

AbstractIn embryos from most animal species a zygotic centrosome is assembled by the centriole derived from the sperm cell and pericentriolar proteins present in the oocyte. This zygotic centrosome acts as a microtubule organizing center (MTOC) to assemble the mitotic spindle in the first and all subsequent cell divisions. As MTOC formation has been studied mainly in adult cells, very little is known about the formation of the first zygotic MTOC. Here we find that zebrafish (Danio rerio) embryos lacking maternal or paternal Cfap53, a centriolar satellite protein, arrest during the first cell cycle due to a failure in proper formation of the mitotic spindle. During the first cell cycle Cfap53 co-localizes with γ-tubulin and other centrosomal and centriolar satellite proteins to the very large MTOC. Furthermore, we find that γ-tubulin localization to the MTOC is impaired in the absence of Cfap53 or when the microtubule network is disrupted. Based on these results we propose a model in which maternal and paternal Cfap53 participates in the organization of the first zygotic MTOC of the embryo. Once the zygotic MTOC is formed, Cfap53 is dispensable for MTOC formation and integrity in subsequent cell divisions.

scholarly journals Interconversion of metaphase and interphase microtubule arrays, as studied by the injection of centrosomes and nuclei into Xenopus eggs.

1984 ◽  
Vol 98 (5) ◽  
pp. 1730-1745 ◽  
Author(s):  
E Karsenti ◽  
J Newport ◽  
R Hubble ◽  
M Kirschner
Keyword(s):  
Electron Microscopy ◽  
Mitotic Spindle ◽  
Microtubule Organizing Center ◽  
Designed Experiments ◽  
Microtubule Organizing Centers ◽  
Organizing Center ◽  
Subsequent Activation

We have designed experiments that distinguish centrosomal , nuclear, and cytoplasmic contributions to the assembly of the mitotic spindle. Mammalian centrosomes acting as microtubule-organizing centers were assayed by injection into Xenopus eggs either in a metaphase or an interphase state. Injection of partially purified centrosomes into interphase eggs induced the formation of extensive asters. Although centrosomes injected into unactivated eggs (metaphase) did not form asters, inhibition of centrosomes is not irreversible in metaphase cytoplasm: subsequent activation caused aster formation. When cytoskeletons containing nuclei and centrosomes were injected into the metaphase cytoplasm, they produced spindle-like structures with clearly defined poles. Electron microscopy revealed centrioles with nucleated microtubules. However, injection of nuclei prepared from karyoplasts that were devoid of centrosomes produced anastral microtubule arrays around condensing chromatin. Co-injection of karyoplast nuclei with centrosomes reconstituted the formation of spindle-like structures with well-defined poles. We conclude from these experiments that in mitosis, the centrosome acts as a microtubule-organizing center only in the proximity of the nucleus or chromatin, whereas in interphase it functions independently. The general implications of these results for the interconversion of metaphase and interphase microtubule arrays in all cells are discussed.

Ultrastructure of the Gaertneriomyces zoospore (Spizellomycetales, Chytridiomycetes)

1981 ◽  
Vol 59 (1) ◽  
pp. 83-90 ◽  
Author(s):  
Donald J. S. Barr
Keyword(s):  
Endoplasmic Reticulum ◽  
New Order ◽  
Microtubule Organizing Center ◽  
Organizing Center

The zoospore type is described for Gaertneriomyces, a genus in the new order Spizellomycetales, Chytridiomycetes. The nucleus lies in the posterior of the zoospore and it has a basal concavity. The kinetosome and nonfunctional centriole are located just distally to the concavity. Microtubulules radiate in the cytoplasm from a presumed microtubule organizing center consisting of two short, electron-opaque bars attached to the kinetosome. Mitochondria are predominantly in the posterior, and aggregates of lipid globules in the anterior of the zoospore. Microbodies are morphologically associated with the lipid and endoplasmic reticulum. They are also found along the sides of the nucleus and near the mitochondria.

Annulate lamellae in spermatogenous cells of Lycopodium obscurum

1995 ◽  
Vol 73 (4) ◽  
pp. 552-556
Author(s):  
John R. Palisano ◽  
Karen Sue Renzaglia ◽  
Angel Renee Maden ◽  
Dean P. Whittier
Keyword(s):  
Endoplasmic Reticulum ◽  
Key Words ◽  
Cross Section ◽  
Plant Tissue ◽  
Cell Lineage ◽  
Annulate Lamellae ◽  
Nuclear Pores ◽  
Spatial Associations ◽  
First Time ◽  
Spermatogenous Cells

The existence of annulate lamellae is detailed for the first time in the ultrastructure of a plant flagellated cell lineage. In early spermatogenous cells of Lycopodium obscurum, annulate lamellae are abundant and located adjacent to either the nucleus or plastid. Individual organelles consist of 1–11 parallel cisternae bearing tightly compacted pores that are similar in size and substructure to nuclear pores. In cross section, the pores measure 95–130 nm in diameter. Frequently, endoplasmic reticulum is continuous with the annulate lamellae cisternae. The existence of annulate lamellae in Lycopodium extends the known distribution of these organelles to rapidly proliferating spermatogenous tissue of seedless plants. Moreover, spatial associations between annulate lamellae and plastids are reported for the first time in any plant tissue. Key words: Annulate lamellae, Lycopodium, plastid, "pteridophyte," spermatogenesis, ultrastructure.

scholarly journals Regulation of Blos1 by IRE1 prevents the accumulation of Huntingtin protein aggregates

2021 ◽  
Author(s):  
Donghwi Bae ◽  
Rachel Elizabeth Jones ◽  
Julie Hollien
Keyword(s):  
Endoplasmic Reticulum ◽  
Cell Death ◽  
Huntington's Disease ◽  
Cultured Cells ◽  
Protein Aggregates ◽  
Mutant Huntingtin ◽  
Microtubule Organizing Center ◽  
Huntingtin Protein ◽  
Late Endosomes ◽  
Organizing Center

Huntington's Disease is characterized by accumulation of the aggregation-prone mutant Huntingtin (mHTT) protein. Here, we show that expression of mHTT in mouse cultured cells activates IRE1, the transmembrane sensor of stress in the endoplasmic reticulum, leading to degradation of the Blos1 mRNA and repositioning of lysosomes and late endosomes toward the microtubule organizing center. Overriding Blos1 degradation results in accumulation of larger mHTT aggregates and increased cell death. Although mHTT is degraded by macroautophagy when highly expressed, we show that prior to the formation of large aggregates, mHTT is degraded via an ESCRT-dependent, endosomal microautophagy pathway. This pathway is enhanced by Blos1 degradation and appears to protect cells from a toxic, less aggregated form of mHTT.

Morphology and zoospore ultrastructure of Lacustromyces hiemalis gen. et sp.nov. (Chytridiales)

1993 ◽  
Vol 71 (3) ◽  
pp. 414-425 ◽  
Author(s):  
Joyce E. Longcore
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Key Words ◽  
Microtubule Organizing Center ◽  
Baseline Study ◽  
Zoosporic Fungus ◽  
Lipid Globule ◽  
Transmission Electron ◽  
Organizing Center ◽  
Thin Walled

As part of a baseline study of chytridiomycete fungi in two Maine lakes, a polycentric, chitinophilic, and heretofore undescribed zoosporic fungus was found. The tubular thallus of Lacustromyces hiemalis gen. et sp.nov. has intercalary thin-walled zoosporangia, has thick-walled resistant sporangia, and does not grow at temperatures greater than 23 °C. Transmission electron microscopy revealed that its zoospores are a variant of the chytridialean type. The microbody – lipid globule complex is of a previously undescribed type, lacking a rumposome or other membrane cisterna and consisting of multiple lipid globules enclosed in a microbody that extends towards the kinetosome. Three kinds of microtubule roots arise near the kinetosome, a root leading to the microbody, a ribosomal root, and a microtubule organizing center that gives rise to microtubules that extend singly into the cytoplasm. Key words: Chytridiales, fungus, Lacustromyces, lake, ultrastructure, zoospore.

scholarly journals The Msd1–Wdr8–Pkl1 complex anchors microtubule minus ends to fission yeast spindle pole bodies

2015 ◽  
Vol 209 (4) ◽  
pp. 549-562 ◽  
Author(s):  
Masashi Yukawa ◽  
Chiho Ikebe ◽  
Takashi Toda
Keyword(s):  
Fission Yeast ◽  
Critical Role ◽  
Spindle Pole Body ◽  
Spindle Pole ◽  
Microtubule Organizing Center ◽  
Spatiotemporal Regulation ◽  
Spindle Pole Bodies ◽  
Organizing Center ◽  
Spindle Microtubules ◽  
Insight Into

The minus ends of spindle microtubules are anchored to a microtubule-organizing center. The conserved Msd1/SSX2IP proteins are localized to the spindle pole body (SPB) and the centrosome in fission yeast and humans, respectively, and play a critical role in microtubule anchoring. In this paper, we show that fission yeast Msd1 forms a ternary complex with another conserved protein, Wdr8, and the minus end–directed Pkl1/kinesin-14. Individual deletion mutants displayed the identical spindle-protrusion phenotypes. Msd1 and Wdr8 were delivered by Pkl1 to mitotic SPBs, where Pkl1 was tethered through Msd1–Wdr8. The spindle-anchoring defect imposed by msd1/wdr8/pkl1 deletions was suppressed by a mutation of the plus end–directed Cut7/kinesin-5, which was shown to be mutual. Intriguingly, Pkl1 motor activity was not required for its anchoring role once targeted to the SPB. Therefore, spindle anchoring through Msd1–Wdr8–Pkl1 is crucial for balancing the Cut7/kinesin-5–mediated outward force at the SPB. Our analysis provides mechanistic insight into the spatiotemporal regulation of two opposing kinesins to ensure mitotic spindle bipolarity.

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