scholarly journals Centrin Scaffold in Chlamydomonas reinhardtii Revealed by Immunoelectron Microscopy

2005 ◽  
Vol 4 (7) ◽  
pp. 1253-1263 ◽  
Author(s):  
Stefan Geimer ◽  
Michael Melkonian
Keyword(s):  
Chlamydomonas Reinhardtii ◽  
Immunoelectron Microscopy ◽  
Basal Body ◽  
Flagellar Apparatus ◽  
Single Copy ◽  
Asymmetric Structure ◽  
Transitional Region ◽  
Ef Hand ◽  
Basal Apparatus ◽  
Postembedding Immunoelectron Microscopy

ABSTRACT In the flagellate green alga Chlamydomonas reinhardtii the Ca2+-binding EF-hand protein centrin is encoded by a single-copy gene. Previous studies have localized the protein to four distinct structures in the flagellar apparatus: the nucleus-basal body connector, the distal connecting fiber, the flagellar transitional region, and the axoneme. To explain the disjunctive distribution of centrin, the interaction of centrin with as yet unknown specific centrin-binding proteins has been implied. Here, we demonstrate using serial section postembedding immunoelectron microscopy of isolated cytoskeletons that centrin is located in additional structures (transitional fibers and basal body lumen) and that the centrin-containing structures of the basal apparatus are likely part of a continuous filamentous scaffold that extends from the nucleus to the flagellar bases. In addition, we show that centrin is located in the distal lumen of the basal body in a rotationally asymmetric structure, the V-shaped filament system. This novel centrin-containing structure has also been detected near the distal end of the probasal bodies. Taken together, these results suggest a role for a rotationally asymmetric centrin “seed” in the growth and development of the centrin scaffold following replication of the basal apparatus.

Cellular asymmetry in Chlamydomonas reinhardtii

1989 ◽  
Vol 94 (2) ◽  
pp. 273-285 ◽  
Author(s):  
J.A. Holmes ◽  
S.K. Dutcher
Keyword(s):  
Chlamydomonas Reinhardtii ◽  
Basal Body ◽  
Flagellar Apparatus ◽  
Spindle Pole ◽  
The Other ◽  
Unicellular Alga ◽  
Phototactic Behavior ◽  
Cellular Asymmetry ◽  
Asymmetric Fusion ◽  
Two Sides

Although largely bilaterally symmetric, the two sides of the unicellular alga Chlamydomonas reinhardtii can be distinguished by the location of the single eyespot. When viewed from the anterior end, the eyespot is always closer to one flagellum than the other, and located at an angle of approximately 45 degrees clockwise of the flagellar plane. This location correlates with the position of one of four acetylated microtubule bundles connected to the flagellar apparatus. Each basal body is attached to two of these microtubule rootlets. The rootlet that positions the eyespot is always attached to the same basal body, which is the daughter of the parental/daughter basal body pair. At mitosis, the replicated basal body pairs segregate in a precise orientation that maintains the asymmetry of the cell and results in mitotic poles that have an invariant handedness. The fusion of gametic cells during mating is also asymmetric. As a result of asymmetric, but different, locations of the plus and minus mating structures, mating preferentially results in quadriflagellate dikaryons with parallel flagellar pairs and both eyespots on the same side of the cell. This asymmetric fusion, as well as all the other asymmetries described, may be necessary for the proper phototactic behavior of these cells. The invariant handedness of the spindle pole, eyespot position, and mating structure position appears to be based on the inherent asymmetry of the basal body pair, providing an example of how an intracellular pattern can be determined and maintained.

scholarly journals FLAGELLAR MOTION AND FINE STRUCTURE OF THE FLAGELLAR APPARATUS IN CHLAMYDOMONAS

1967 ◽  
Vol 33 (3) ◽  
pp. 543-571 ◽  
Author(s):  
David L. Ringo
Keyword(s):  
Fine Structure ◽  
Flagellar Apparatus ◽  
Transitional Region ◽  
Basal Bodies ◽  
Striated Fiber ◽  
Basal Apparatus ◽  
Cilia And Flagella ◽  
Electron Microscopes ◽  
Shaped Pattern ◽  
Complex Arrangement

The biflagellate alga Chlamydomonas reinhardi was studied with the light and electron microscopes to determine the behavior of flagella in the living cell and the structure of the basal apparatus of the flagella. During normal forward swimming the flagella beat synchronously in the same plane, as in the human swimmer's breast stroke. The form of beat is like that of cilia. Occasionally cells swim backward with the flagella undulating and trailing the cell. Thus the same flagellar apparatus produces two types of motion. The central pair of fibers of both flagella appear to lie in the same plane, which coincides with the plane of beat. The two basal bodies lie in a V configuration and are joined at the top by a striated fiber and at the bottom by two smaller fibers. From the area between the basal bodies four bands of microtubules, each containing four tubules, radiate in an X-shaped pattern, diverge, and pass under the cell membrane. Details of the complex arrangement of tubules near the basal bodies are described. It seems probable that the connecting fibers and the microtubules play structural roles and thereby maintain the alignment of the flagellar apparatus. The relation of striated fibers and microtubules to cilia and flagella is reviewed, particularly in phytoflagellates and protozoa. Structures observed in the transitional region between the basal body and flagellar shaft are described and their occurrence is reviewed. Details of structure of the flagellar shaft and flagellar tip are described, and the latter is reviewed in detail.

Ultrastructure of the basal body apparatus in epidermal cells of a sponge larva (Aplysilla SP: Demospongiae)

1992 ◽  
Vol 50 (1) ◽  
pp. 928-929
Author(s):  
R.L. Pinto ◽  
R.M. Woollacott
Keyword(s):  
Sodium Bicarbonate ◽  
Epoxy Resin ◽  
Basal Body ◽  
Phosphate Buffer ◽  
Similar Data ◽  
Basal Apparatus ◽  
Striated Rootlet ◽  
The Common ◽  
Basal Foot ◽  
Sexually Mature

The basal body and its associated rootlet are the organelles responsible for anchoring the flagellum or cilium in the cytoplasm. Structurally, the common denominators of the basal apparatus are the basal body, a basal foot from which microtubules or microfilaments emanate, and a striated rootlet. A study of the basal apparatus from cells of the epidermis of a sponge larva was initiated to provide a comparison with similar data on adult sponges.Sexually mature colonies of Aplysillasp were collected from Keehi Lagoon Marina, Honolulu, Hawaii. Larvae were fixed in 2.5% glutaraldehyde and 0.14 M NaCl in 0.2 M Millonig’s phosphate buffer (pH 7.4). Specimens were postfixed in 1% OsO4 in 1.25% sodium bicarbonate (pH 7.2) and embedded in epoxy resin. The larva ofAplysilla sp was previously described (as Dendrilla cactus) based on live observations and SEM by Woollacott and Hadfield.

scholarly journals Phosphorylation of nuclear and flagellar basal apparatus proteins during flagellar regeneration in Chlamydomonas reinhardtii

1993 ◽  
Vol 122 (4) ◽  
pp. 877-886 ◽  
Author(s):  
JD Harper ◽  
MA Sanders ◽  
JL Salisbury
Keyword(s):  
Chlamydomonas Reinhardtii ◽  
Transcriptional Activation ◽  
Kinase Inhibitor ◽  
Nuclear Periphery ◽  
Immunoblot Analysis ◽  
Basal Region ◽  
Western Immunoblot ◽  
Flagellar Regeneration ◽  
Basal Apparatus ◽  
Western Immunoblot Analysis

The antiphosphoprotein monoclonal antibody MPM-2 was used to investigate protein phosphorylation during flagellar regeneration in Chlamydomonas reinhardtii. MPM-2 recognizes a phosphorylated epitope and detects several Chlamydomonas proteins by Western immunoblot analysis. Two MPM-2 reactive proteins (34 and 90 kD) increase in Western immunoblot intensity after flagellar excision and decrease in intensity during flagellar regeneration. Immunofluorescence and immunogold labeling revealed MPM-2 staining within the nucleus, especially towards the nuclear periphery, the flagellar basal apparatus, and the nucleus-basal body connector after flagellar excision. Comparison of MPM-2 reactivity in wild-type cells and in the mutant bald-2, which lacks functional basal bodies, demonstrates that the 34-kD protein is localized in the nucleus and the 90-kD protein is localized in the flagellar basal region. MPM-2 reactivity is observed in cells competent for flagellar regeneration. However, when cells were treated with the kinase inhibitor, staurosporine, MPM-2 reactivity did not increase after flagellar excision and flagellar regeneration was impaired. These observations suggest that phosphorylation of the 34- and 90-kD proteins may be important for flagellar regrowth. Possible roles for phosphorylation in flagellar regeneration include transcriptional activation and transport of flagellar precursors to the base of the growing flagella.

Basal Body and Flagellar Development During the Vegetative Cell Cycle and the Sexual Cycle of Chlamydomonas Reinhardii

1974 ◽  
Vol 16 (3) ◽  
pp. 529-556 ◽  
Author(s):  
T. CAVALIER-SMITH
Keyword(s):  
Basal Body ◽  
Vegetative Cell ◽  
Amorphous Material ◽  
Sexual Cycle ◽  
Transitional Region ◽  
Basal Bodies ◽  
Vegetative Cells ◽  
Chlamydomonas Reinhardii ◽  
Body Development ◽  
Microtubular Roots

Basal body development and flagellar regression and growth in the unicellular green alga Chlamydomonas reinhardii were studied by light and electron microscopy during the vegetative cell cycle in synchronous cultures and during the sexual life cycle. Flagella regress by gradual shortening prior to vegetative cell division and also a few hours after cell fusion in the sexual cycle. In vegetative cells basal bodies remain attached to the plasma membrane by their transitional fibres and do not act as centrioles at the spindle poles during division. In zygotes the basal bodies and associated microtubular roots and cross-striated connexions all dissolve, and by 6.5 h after mating all traces of flagellar apparatus and associated structures have disappeared. They remain absent for 6 days throughout zygospore maturation and then are reassembled during zygospore germination, after meiosis has begun. Basal body assembly in developing zygospores occurs close to the plasma membrane (in the absence of pre-existing basal bodies) via an intermediate stage consisting of nine single A-tubules surrounding a central ‘cartwheel’. Assembly is similar in vegetative cells (and occurs prior to cell division), except that new basal bodies are physically attached to old ones by amorphous material. In vegetative cells, amorphous disks, which may possibly be still earlier stages in basal-body development occur in the same location as 9-singlet developing basal bodies. After the 9-singlet structure is formed, B and C fibres are added and the basal body elongates to its mature length. Microtubular roots, striated connexions and flagella are then assembled. Both flagellar regression and growth are gradual and sequential, the transitional region at the base of the flagellum being formed first and broken down last. The presence of amorphous material at the tip of the axoneme of growing and regressing flagella suggests that the axoneme grows or shortens by the sequential assembly or disassembly at its tip. In homogenized cells basal bodies remain firmly attached to each other by their striated connexions. The flagellar transitional region, and parts of the membrane and of the 4 microtubular roots, also remain attached; so also do new developing basal bodies, if present. These structures are well preserved in homogenates and new fine-structural details can be seen. These results are discussed, and lend no support to the idea that basal bodies have genetic continuity. It is suggested that basal body development can be best understood if a distinction is made between the information needed to specify the structure of a basal body and that needed to specify its location and orientation.

In vitro effects of taxol on ciliogenesis in quail oviduct

1989 ◽  
Vol 92 (1) ◽  
pp. 9-20 ◽  
Author(s):  
E. Boisvieux-Ulrich ◽  
M.C. Laine ◽  
D. Sandoz
Keyword(s):  
Basal Body ◽  
In Situ Polymerization ◽  
Neck Region ◽  
Apical Part ◽  
Transitional Region ◽  
Basal Bodies ◽  
Apical Surface ◽  
In Vitro Effects

When induced by in vivo oestrogen stimulation, ciliogenesis continues in culture in vitro of quail oviduct implants. Ultrastructure of ciliogenic cells was compared after culture for 24 or 48 h in the presence or absence of 10(−5) M-taxol. Taxol, which promotes polymerization and stabilization of microtubules, disturbed ciliogenesis, but formation of basal bodies was unaffected by the drug. Conversely, their migration towards the apical surface seemed to be slowed down or blocked and axonemal doublets polymerized onto the distal end of cytoplasmic basal bodies. They elongated and often constituted a more or less complete axoneme, extending between organelles in various orientations. These axonemes, often abnormal, were not surrounded by a membrane, with the exception of the transitional or neck region between the basal body and axoneme. The formation of membrane in this area resulted from the binding of some vesicles to the anchoring fibres of the basal body. They fused in various numbers, occasionally forming a ring, at the site of the transitional region, and exhibited the characteristics of the ciliary necklace. The association of basal bodies with vesicles or with the plasma membrane appeared to be a necessary signal for in situ polymerization of axonemal doublets. In addition, taxol induced polymerization of numerous microtubules in the cytoplasm, especially in the apical part of the cell and in the Golgi area. This network of microtubules may prevent basal body migration.

The flagellar apparatus ofDunaliella: Isolation of basal body-flagellar root complex

PROTOPLASMA ◽  
1985 ◽  
Vol 127 (1-2) ◽  
pp. 82-92 ◽  
Author(s):  
Francelyne Marano ◽  
Angelica Santa-Maria ◽  
Sushila Krishnawamy
Keyword(s):  
Basal Body ◽  
Flagellar Apparatus
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