Localization of gamma-tubulin in interphase and mitotic cells of a unicellular eukaryote, Giardia intestinalis

Nohýnková, Eva; Dráber, Pavel; Reischig, Josef; Kulda, Jaroslav

doi:10.1078/0171-9335-00066

Cited by 51 publications

(35 citation statements)

References 38 publications

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“…We predict that careful analysis of ␥-tubulin in the intermediate stages of mitosis as outlined in our study would reveal ␥-tubulin as part of the spindle-pole complex. In a recent study, ␥-tubulin localization was detected at basal bodies both before and after nuclear division, although spindles were not directly observed (Nohynkova et al, 2000). We found that a second basal body is found at the periphery of the spindle-pole region, peripheral to the focused spindle microtubules (Fig.…”

Section: Evidence For Kinetochore Microtubules In Chromosome Segregationmentioning

confidence: 93%

Three-dimensional analysis of mitosis and cytokinesis in the binucleate parasiteGiardia intestinalis

Sagolla

Dawson

Mancuso

et al. 2006

Journal of Cell Science

115

141

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In the binucleate parasite Giardia intestinalis, two diploid nuclei and essential cytoskeletal structures including eight flagella are duplicated and partitioned into two daughter cells during cell division. The mechanisms of mitosis and cytokinesis in the binucleate parasite Giardia are poorly resolved, yet have important implications for the maintenance of genetic heterozygosity. To articulate the mechanism of mitosis and the plane of cell division, we used three-dimensional deconvolution microscopy of each stage of mitosis to monitor the spatial relationships of conserved cytological markers to the mitotic spindles, the centromeres and the spindle poles. Using both light- and transmission electron microscopy, we determined that Giardia has a semi-open mitosis with two extranuclear spindles that access chromatin through polar openings in the nuclear membranes. In prophase, the nuclei migrate to the cell midline, followed by lateral chromosome segregation in anaphase. Taxol treatment results in lagging chromosomes and half-spindles. Our analysis supports a nuclear migration model of mitosis with lateral chromosome segregation in the left-right axis and cytokinesis along the longitudinal plane (perpendicular to the spindles), ensuring that each daughter inherits one copy of each parental nucleus with mirror image symmetry. Fluorescence in situ hybridization (FISH) to an episomal plasmid confirms that the nuclei remain separate and are inherited with mirror image symmetry.

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Section: Evidence For Kinetochore Microtubules In Chromosome Segregationmentioning

confidence: 93%

Three-dimensional analysis of mitosis and cytokinesis in the binucleate parasiteGiardia intestinalis

Sagolla

Dawson

Mancuso

et al. 2006

Journal of Cell Science

115

141

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“…For immunofluorescence, a method described previously was used (28). The cells attached to a glass coverslip forming a bottom of the anaerobic chamber were fixed with ice-cold methanol (at Ϫ20°C for 5 min), permeabilized with ice-cold acetone (at Ϫ20°C for next 5 min), and air dried.…”

Section: Methodsmentioning

confidence: 99%

Cell Division of Giardia intestinalis : Flagellar Developmental Cycle Involves Transformation and Exchange of Flagella between Mastigonts of a Diplomonad Cell

2006

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Giardia intestinalis is a binucleated diplomonad possessing four pairs of flagella of distinct location and function. Its pathogenic potential depends on the integrity of a complex microtubular cytoskeleton that undergoes a profound but poorly understood reorganization during cell division. We examined the cell division of G. intestinalis with the aid of light and electron microscopy and immunofluorescence methods and present here new observations on the reorganization of the flagellar apparatus in the dividing Giardia. Our results demonstrated the presence of a flagellar maturation process during which the flagella migrate, assume different position, and transform to different flagellar types in progeny until their maturation is completed. For each newly assembled flagellum it takes three cell cycles to become mature. The mature flagellum of Giardia is the caudal one that possesses a privileged basal body at which the microtubules of the adhesive disk nucleate. In contrast to generally accepted assumption that each of the two diplomonad mastigonts develops separately, we found that they are developmentally linked, exchanging their cytoskeletal components at the early phase of mitosis. The presence of the flagellar maturation process in a metamonad protist Giardia suggests that the basal body or centriole maturation is a universal phenomenon that may represent one of the core processes in a eukaryotic cell.The flagella of eukaryotic protists undergo a remarkable morphogenetic transformation called flagellar developmental cycle, whereby a flagellum passes through a maturation process before assuming its final position in the cell. In contrast to nucleus and some other organelles, which complete their development in a single cell cycle, it is now evident that in many groups of protists flagella require more than one cell cycle to mature (2,26). In this respect, the behavior of flagellar structures in unicellular eukaryotes closely resembles that of centrioles in animal cells (3,25).On division of a flagellate, each daughter cell receives one half of parent flagella and/or basal bodies, while the other half arise de novo. This semiconservative distribution has been known for a long time (reviewed in reference 14). However, until a pioneering study of Melkonian et al. (24) it was not clear how unicellular protists maintain the structural and functional heterogeneity of their flagellar apparatus during division. The observations of Melkonian et al. (24) on the biflagellate heterokont green alga Nephroselmis olivacea provided the first evidence that the heterogeneous flagellar apparatus is conserved in progeny through transformation of a flagellar type during cell division and that a newly formed flagellum requires more than one cell cycle to complete its development. The flagellar transformation has been later found in other groups of unicellular algae (reviewed in reference 2) and in representatives of other taxonomic groups of flagellated freeliving protists (reviewed in reference 26). There are, however, several m...

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“…By mining the Giardia genome database for cyclin homologs (Reiner et al, 2008), several genes have been identified as candidates for a mitotic cyclin on the basis of sequence similarity. Each cell contains two diploid nuclei that are replicated concurrently (Bernander et al, 2001;Sagolla et al, 2006), and then simultaneously segregated to opposite poles of the cell by two separate spindles, prior to cytokinesis (Nohýnkova et al, 2000;Sagolla et al, 2006). Thus, the cell cycle in Giardia has G1, S, G2 and M phases similar to other eukaryotes.…”

Section: Introductionmentioning

confidence: 99%

The Giardia cell cycle progresses independently of the Anaphase Promoting Complex

Gourguechon

Holt

Cande

2013

Journal of Cell Science

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SummaryMost cell cycle regulation research has been conducted in model organisms representing a very small part of the eukaryotic domain. The highly divergent human pathogen Giardia intestinalis is ideal for studying the conservation of eukaryotic pathways. Although Giardia has many cell cycle regulatory components, its genome lacks all anaphase-promoting complex (APC) components. In the present study, we show that a single mitotic cyclin in Giardia is essential for progression into mitosis. Strikingly, Giardia cyclin B lacks the conserved N-terminal motif required for timely degradation mediated by the APC and ubiquitin conjugation. Expression of Giardia cyclin B in fission yeast is toxic, leading to a prophase arrest, and this toxicity is suppressed by the addition of a fission yeast degradation motif. Cyclin B is degraded during mitosis in Giardia cells, but this degradation appears to be independent of the ubiquitination pathway. Other putative APC substrates, aurora and polo-like kinases, also show no evidence of ubiquitination. This is the first example of mitosis not regulated by the APC and might reflect an evolutionary ancient form of cell cycle regulation.

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Localization of gamma-tubulin in interphase and mitotic cells of a unicellular eukaryote, Giardia intestinalis

Cited by 51 publications

References 38 publications

Three-dimensional analysis of mitosis and cytokinesis in the binucleate parasiteGiardia intestinalis

Three-dimensional analysis of mitosis and cytokinesis in the binucleate parasiteGiardia intestinalis

Cell Division of Giardia intestinalis : Flagellar Developmental Cycle Involves Transformation and Exchange of Flagella between Mastigonts of a Diplomonad Cell

The Giardia cell cycle progresses independently of the Anaphase Promoting Complex

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