scholarly journals Bld10p, a novel protein essential for basal body assembly in Chlamydomonas

2004 ◽  
Vol 165 (5) ◽  
pp. 663-671 ◽  
Author(s):  
Kumi Matsuura ◽  
Paul A. Lefebvre ◽  
Ritsu Kamiya ◽  
Masafumi Hirono
Keyword(s):  
Basal Body ◽  
Cell Biology ◽  
Early Stage ◽  
Rotational Symmetry ◽  
Coiled Coil ◽  
Electron Microscopic Observation ◽  
Basal Bodies ◽  
Mitotic Spindles ◽  
Electron Microscopic ◽  
Cytoplasmic Microtubules

How centrioles and basal bodies assemble is a long-standing puzzle in cell biology. To address this problem, we analyzed a novel basal body-defective Chlamydomonas reinhardtii mutant isolated from a collection of flagella-less mutants. This mutant, bld10, displayed disorganized mitotic spindles and cytoplasmic microtubules, resulting in abnormal cell division and slow growth. Electron microscopic observation suggested that bld10 cells totally lack basal bodies. The product of the BLD10 gene (Bld10p) was found to be a novel coiled-coil protein of 170 kD. Immunoelectron microscopy localizes Bld10p to the cartwheel, a structure with ninefold rotational symmetry positioned near the proximal end of the basal bodies. Because the cartwheel forms the base from which the triplet microtubules elongate, we suggest that Bld10p plays an essential role in an early stage of basal body assembly. A viable mutant having such a severe basal body defect emphasizes the usefulness of Chlamydomonas in studying the mechanism of basal body/centriole assembly by using a variety of mutants.

scholarly journals The Vfl1 Protein in Chlamydomonas Localizes in a Rotationally Asymmetric Pattern at the Distal Ends of the Basal Bodies

2001 ◽  
Vol 153 (1) ◽  
pp. 63-74 ◽  
Author(s):  
Carolyn D. Silflow ◽  
Matthew LaVoie ◽  
Lai-Wa Tam ◽  
Susan Tousey ◽  
Mark Sanders ◽  
...  
Keyword(s):  
Basal Body ◽  
Rotational Symmetry ◽  
Coiled Coil ◽  
Mutant Phenotype ◽  
Basal Bodies ◽  
Repeat Sequences ◽  
Coiled Coil Domain ◽  
Cell Biol ◽  
Asymmetric Pattern ◽  
Rotational Orientation

In the unicellular alga Chlamydomonas, two anterior flagella are positioned with 180° rotational symmetry, such that the flagella beat with the effective strokes in opposite directions (Hoops, H.J., and G.B. Witman. 1983. J. Cell Biol. 97:902–908). The vfl1 mutation results in variable numbers and positioning of flagella and basal bodies (Adams, G.M.W., R.L. Wright, and J.W. Jarvik. 1985. J. Cell Biol. 100:955–964). Using a tagged allele, we cloned the VFL1 gene that encodes a protein of 128 kD with five leucine-rich repeat sequences near the NH2 terminus and a large α-helical–coiled coil domain at the COOH terminus. An epitope-tagged gene construct rescued the mutant phenotype and expressed a tagged protein (Vfl1p) that copurified with basal body flagellar apparatuses. Immunofluorescence experiments showed that Vfl1p localized with basal bodies and probasal bodies. Immunogold labeling localized Vfl1p inside the lumen of the basal body at the distal end. Distribution of gold particles was rotationally asymmetric, with most particles located near the doublet microtubules that face the opposite basal body. The mutant phenotype, together with the localization results, suggest that Vfl1p plays a role in establishing the correct rotational orientation of basal bodies. Vfl1p is the first reported molecular marker of the rotational asymmetry inherent to basal bodies.

scholarly journals A nucleus-basal body connector in Chlamydomonas reinhardtii that may function in basal body localization or segregation.

1985 ◽  
Vol 101 (5) ◽  
pp. 1903-1912 ◽  
Author(s):  
R L Wright ◽  
J Salisbury ◽  
J W Jarvik
Keyword(s):  
Chlamydomonas Reinhardtii ◽  
Basal Body ◽  
Nuclear Dna ◽  
Electron Microscopic Observation ◽  
Variable Number ◽  
Immunofluorescent Staining ◽  
Major Protein ◽  
Basal Bodies ◽  
Electron Microscopic ◽  
And Function

We have isolated a nucleus-basal body complex from Chlamydomonas reinhardtii. The complex is strongly immunoreactive to an antibody generated against a major protein constituent of isolated Tetraselmis striata flagellar roots (Salisbury, J. L., A. Baron, B. Surek, and M. Melkonian, J. Cell Biol., 99:962-970). Electrophoretic and immunoelectrophoretic analysis indicates that, like the Tetraselmis protein, the Chlamydomonas antigen consists of two acidic isoforms of approximately 20 kD. Indirect immunofluorescent staining of nucleus-basal body complexes reveals two major fibers in the connector region, one between each basal body and the nucleus. The nucleus is also strongly immunoreactive, with staining radiating around much of the nucleus from a region of greatest concentration at the connector pole. Calcium treatment causes shortening of the connector fibers and also movement of nuclear DNA towards the connector pole. Electron microscopic observation of negatively stained nucleus-basal body complexes reveals a cluster of approximately 6-nm filaments, suspected to represent the connector, between the basal bodies and nuclei. A mutant with a variable number of flagella, vfl-2-220, is defective with respect to the nucleus-basal body association. This observation encourages us to speculate that the nucleus-basal body union is important for accurate basal body localization within the cell and/or for accurate segregation of parental and daughter basal bodies at cell division. A physical association between nuclei and basal bodies or centrioles has been observed in a variety of algal, protozoan, and metazoan cells, although the nature of the association, in terms of both structure and function, has been obscure. We believe it likely that fibrous connectors homologous to those described here for Chlamydomonas are general features of centriole-bearing eucaryotic cells.

scholarly journals High-Resolution Petrographic Evidence Confirming Detrital and Biogenic Magnetites as Remanence Carriers for Zongpu Carbonates in the Gamba Area, South Tibet

2021 ◽  
Vol 9 ◽  
Author(s):  
Qian Zhao ◽  
Baochun Huang ◽  
Zhiyu Yi ◽  
Pengfei Xue
Keyword(s):  
High Resolution ◽  
Electron Backscatter Diffraction ◽  
Early Stage ◽  
Electron Microscopic Observation ◽  
Optical Microscope ◽  
Magnetic Minerals ◽  
Electron Microscopic ◽  
Magnetic Carriers ◽  
Magnetic Extraction ◽  
South Tibet

Paleocene carbonates from the Gamba area of South Tibet provide the largest paleomagnetic dataset for constraining the paleogeography of the India-Asia collision in the early stage. Previous studies argued that the characteristic remanences (ChRMs) obtained from this unit were remagnetized via orogenic fluids. This study carries out a high-resolution petrographic study on the Paleocene carbonates from Gamba aiming to test the nature of the ChRMs. Electron microscopic observation on magnetic extracts identified a large amount of detrital magnetite that are multi- to single domain in sizes and nanoscale biogenic magnetite. Minor framboidal iron oxides were also identified, which were previously interpreted as authigenic magnetite that substitutes pyrite. However, our scanning and transmission electron microscopic (SEM/TEM) observations, along with optical microscope and Raman spectrum investigations further suggest that these magnetic minerals are pigmentary hematite and goethite that are incapable of carrying a stable primary magnetization. We therefore argue that the ChRMs of the limestones from the Zongpu Formation in the Gamba area are carried by detrital and biogenic magnetites rather than authigenic magnetite. The paleomagnetic data from the Gamba area are interpreted as primary origin and can thus be used for tectonic reconstructions. We emphasize that magnetic extraction, integrated with advanced mineralogic studies (e.g., electron backscatter diffraction and electron diffraction) are effective approaches for investigating the origin of magnetic carriers in carbonate rocks.

scholarly journals HMGB1/RAGE axis mediates stress-induced RVLM neuroinflammation in mice via impairing mitophagy flux in microglia

2020 ◽  
Vol 17 (1) ◽  
Author(s):  
Shutian Zhang ◽  
Li Hu ◽  
Jialun Jiang ◽  
Hongji Li ◽  
Qin Wu ◽  
...  
Keyword(s):  
Early Stage ◽  
High Mobility ◽  
Electron Microscopic Observation ◽  
Ventrolateral Medulla ◽  
Electron Microscopic ◽  
Ph Change ◽  
Transmission Electron ◽  
Transmission Electron Microscopic Observation ◽  
M1 Polarization ◽  
Underlying Mechanisms

Abstract Background Microglial mediated neuroinflammation in the rostral ventrolateral medulla (RVLM) plays roles in the etiology of stress-induced hypertension (SIH). It was reported that autophagy influenced inflammation via immunophenotypic switching of microglia. High-mobility group box 1 (HMGB1) acts as a regulator of autophagy and initiates the production of proinflammatory cytokines (PICs), but the underlying mechanisms remain unclear. Methods The stressed mice were subjected to intermittent electric foot shocks plus noises administered for 2 h twice daily for 15 consecutive days. In mice, blood pressure (BP) and renal sympathetic nerve activity (RSNA) were monitored by noninvasive tail-cuff method and platinum-iridium electrodes placed respectively. Microinjection of siRNA-HMGB1 (siHMGB1) into the RVLM of mice to study the effect of HMGB1 on microglia M1 activation was done. mRFP-GFP-tandem fluorescent LC3 (tf-LC3) vectors were transfected into the RVLM to evaluate the process of autolysosome formation/autophagy flux. The expression of RAB7, lysosomal-associated membrane protein 1 (LAMP1), and lysosomal pH change were used to evaluate lysosomal function in microglia. Mitophagy was identified by transmission electron microscopic observation or by checking LC3 and MitoTracker colocalization under a confocal microscope. Results We showed chronic stress increased cytoplasmic translocations of HMGB1 and upregulation of its receptor RAGE expression in microglia. The mitochondria injury, oxidative stress, and M1 polarization were attenuated in the RVLM of stressed Cre-CX3CR1/RAGEfl/fl mice. The HMGB1/RAGE axis increased at the early stage of stress-induced mitophagy flux while impairing the late stages of mitophagy flux in microglia, as revealed by decreased GFP fluorescence quenching of GFP-RFP-LC3-II puncta and decreased colocalization of lysosomes with mitochondria. The expressions of RAB7 and LAMP1 were decreased in the stressed microglia, while knockout of RAGE reversed these effects and caused an increase in acidity of lysosomes. siHMGB1 in the RVLM resulted in BP lowering and RSNA decreasing in SIH mice. When the autophagy inducer, rapamycin, is used to facilitate the mitophagy flux, this treatment results in attenuated NF-κB activation and reduced PIC release in exogenous disulfide HMGB1 (ds-HMGB1)-stimulated microglia. Conclusions Collectively, we demonstrated that inhibition of the HMGB1/RAGE axis activation led to increased stress-induced mitophagy flux, hence reducing the activity of microglia-mediated neuroinflammation and consequently reduced the sympathetic vasoconstriction drive in the RVLM.

Coarsening of Cobalt Precipitates in Copper- Cobalt Alloys

1982 ◽  
Vol 21 ◽  
Author(s):  
T. Eguchi ◽  
Y. Tomokiyo ◽  
K. Oki ◽  
Y. Seno
Keyword(s):  
Aging Time ◽  
Ostwald Ripening ◽  
Volume Fraction ◽  
Early Stage ◽  
Electron Microscopic Observation ◽  
Rate Of Change ◽  
Cube Root ◽  
Electron Microscopic ◽  
The Mean ◽  
Co Alloys

ABSTRACTThe Ostwald ripening of precipitates in Cu-Co alloys was investigated by electron microscopic observation. The variation of the mean particle radius r, and the distribution of relative particle sizes, f(r/r) , were obtained as functions of the aging time at 873K . The shape of f(r/r)was rather sharp and symmetrical around r = T in the early stage. It became broad with the aging and was similar, in the late stage, to the theoretical distribution of Ardell. It appeared that the shape of f(r/r) depends on the volume fraction but the growth rate of F scarcely depends on it. The rate of change of r was proportional to the cube root of the aging time from the early stage of aging.

scholarly journals Drosophila chibby is required for basal body formation and ciliogenesis but not for Wg signaling

2012 ◽  
Vol 197 (2) ◽  
pp. 313-325 ◽  
Author(s):  
Camille Enjolras ◽  
Joëlle Thomas ◽  
Brigitte Chhin ◽  
Elisabeth Cortier ◽  
Jean-Luc Duteyrat ◽  
...  
Keyword(s):  
Wnt Signaling ◽  
Basal Body ◽  
Coiled Coil ◽  
Cell Types ◽  
Sensory Transduction ◽  
Basal Bodies ◽  
Neuronal Cilia ◽  
Complex Process ◽  
Specific Proteins ◽  
And Function

Centriole-to–basal body conversion, a complex process essential for ciliogenesis, involves the progressive addition of specific proteins to centrioles. CHIBBY (CBY) is a coiled-coil domain protein first described as interacting with β-catenin and involved in Wg-Int (WNT) signaling. We found that, in Drosophila melanogaster, CBY was exclusively expressed in cells that require functional basal bodies, i.e., sensory neurons and male germ cells. CBY was associated with the basal body transition zone (TZ) in these two cell types. Inactivation of cby led to defects in sensory transduction and in spermatogenesis. Loss of CBY resulted in altered ciliary trafficking into neuronal cilia, irregular deposition of proteins on spermatocyte basal bodies, and, consequently, distorted axonemal assembly. Importantly, cby1/1 flies did not show Wingless signaling defects. Hence, CBY is essential for normal basal body structure and function in Drosophila, potentially through effects on the TZ. The function of CBY in WNT signaling in vertebrates has either been acquired during vertebrate evolution or lost in Drosophila.

Ultrastructure and development of the flagellar apparatus and flagellar motion in the colonial graeen alga Astrephomene gubernaculifera

1983 ◽  
Vol 63 (1) ◽  
pp. 21-41
Author(s):  
H.J. Hoops ◽  
G.L. Floyd
Keyword(s):  
Basal Body ◽  
Rotational Symmetry ◽  
Amorphous Material ◽  
Flagellar Apparatus ◽  
The Other ◽  
Basal Bodies ◽  
Mature Cell ◽  
Embryonic Cleavage ◽  
Development Proceeds ◽  
Concurrent Events

Immediately following embryonic cleavage, the cells of Astrephomene have four equal-sized basal bodies, two of which are connected by a striated distal fibre and two striated proximal fibres. The four microtubular rootlets, which alternate between having 3/1 and 2 members, are arranged cruciately. The two basal bodies that are connected by the striated fibres then extend into flagella, while the two accessory basal bodies are now markedly shorter. At this stage the flagellar apparatus has 180 degrees rotational symmetry and is very similar to the flagellar apparatus of the unicellular Chlamydomonas and related algae. Development proceeds with a number of concurrent events. The basal bodies begin to separate at their proximal ends and become nearly parallel. Each striated proximal fibre detaches at one end from one of the basal bodies. Each half of the flagellar apparatus, which consists of a flagellum and attached basal body, an accessory basal body, two rootlets and a striated fibre (formerly one of the proximal striated fibres), rotates about 90 degrees, the two halves rotating in opposite directions. An electron-dense strut forms near one two-membered rootlet and grows past both basal bodies. During this time a fine, fibrous component appears between newly developed spade-like structures and associated amorphous material connected to each basal body. The basal bodies continue to separate as the distal fibre stretches and finally detaches from one of them. These processes result in the loss of the 180 degree rotational symmetry present in previous stages. Although the flagella continue to separate, there is no further reorganization of the components of the flagellar apparatus. In the mature cell of Astrephomene, the two flagella are inserted separately and are parallel. The four microtubular rootlets are no longer arranged cruciately. Three of the rootlets are nearly parallel, while the fourth is approximately perpendicular to the other three. A straited fibre connects each basal body to the underside of the strut. These fibres run in the direction of the effective stroke of the flagella and might be important either in anchoring the basal bodies or in the initiation of flagellar motion. Unlike the case in the unicellular Chlamydomonas, the two flagella beat in the same direction and in parallel planes. The flagella of a given cell may or may not beat in synchrony. The combination of this type of flagellar motion and the parallel, separate flagella appears to be suited to the motion of this colonial organism.

Anti-tubulin antibodies locate the blepharoplast during spermatogenesis in the fern Platyzoma microphyllum R.Br.: a correlated immunofluorescence and electron-microscopic study

1986 ◽  
Vol 81 (1) ◽  
pp. 243-265
Author(s):  
J.H. Doonan ◽  
C.W. Lloyd ◽  
J.G. Duckett
Keyword(s):  
Basal Body ◽  
De Novo ◽  
Spindle Pole ◽  
Electron Microscopic ◽  
Mitotic Apparatus ◽  
Strong Argument ◽  
Body Formation ◽  
Spindle Poles ◽  
Tubulin Antibodies ◽  
Cytoplasmic Microtubules

The discovery that the monoclonal anti-tubulin antibody YOL 1/34 recognizes a microtubule organizing centre, the blepharoplast (which arises de novo during the latter stages of spermatogenesis in the fern, Platyzoma microphyllum), has enabled us to follow it and associated microtubules throughout most of its ontogeny. By correlating electron-microscopic and immunofluorescence observations, YOL 1/34 is seen to stain the blepharoplast uniformly at a time when no microtubules are present within the organelle. Later, staining becomes intense at the surface, concomitant with the re-location of cylindrical channels to the periphery of the blepharoplast. During anaphase of the ultimate division of the spermatid mother cell the blepharoplast moves to the spindle poles and sharpens the otherwise barrel-shaped mitotic apparatus. Prior to this stage the blepharoplast is, however, off-centre and at variable positions around the poles. Later still, in the differentiating spermatids, the blepharoplast is the focus for radiating cytoplasmic microtubules that abut directly onto the electron-dense organelle, penetrating the ribosome-free halo. The three main conclusions are: that tubulin in a pre-microtubular form is associated with the cylindrical channels that arise de novo within the previously amorphous blepharoplast and act as a template in basal body formation; that the late appearance of the blepharoplast as a focus for the spindle poles during the final mitosis provides strong argument against its functioning during spindle pole initiation (despite its ability to sharpen the poles at anaphase); that the blepharoplast does seem to act as a microtubule organizing centre in the mitotically quiescent spermatid.

The ultrastructure of Ulothrix mucosa. II. The flagellar apparatus of the zoospore

1986 ◽  
Vol 64 (1) ◽  
pp. 166-176 ◽  
Author(s):  
G. M. Lokhorst ◽  
W. Star
Keyword(s):  
Basal Body ◽  
Spatial Configuration ◽  
Rotational Symmetry ◽  
Flagellar Apparatus ◽  
Taxonomic Status ◽  
Proximal Region ◽  
Basal Bodies ◽  
Serial Sectioning ◽  
Counterclockwise Direction ◽  
Microtubular Roots

The actual spatial configuration of the flagellar apparatus of the quadriflagellate zoospore of Ulothrix mucosa Thuret has been reconstructed by serial sectioning analysis. This apparatus shows an architecture quite similar to that found in related Ulvophyceae. Common characteristics are the differently leveled basal body pairs; the 180° rotational symmetry of the flagellar apparatus; the proximal overlap of the upper basal bodies which are displaced with respect to each other in the counterclockwise direction; terminal caps; four cruciately arranged microtubular roots (R2, R4); a distinctly striated distal connecting fibre that interconnects the upper basal bodies; and striated bands (SB1) that join the R4s to the lower basal bodies. Specific features are the arrangement of the R4 in a three over one configuration when entering the proximal region of the flagellar apparatus; the differently shaped proximal sheaths and their association with a proximal sheath connecting band; the presence of two system II fibres (rhizoplasts) which arise from the lower basal body pair; the striated bands (SB2) that connect the R2s to the lower basal bodies; the distinct striation of the system I fibre, which is not only intimately associated with the R2, but also with the R4 (not earlier reported for an ulvophycean alga); and, finally, the relevant displacement of the lower basal body pair in a counterclockwise direction of approximately half a basal body diameter. In light of these findings the taxonomic status of the Ulotrichales as well as of the Ulvophyceae is discussed.

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