scholarly journals Electron tomography of plant thylakoid membranes

2011 ◽  
Vol 62 (7) ◽  
pp. 2393-2402 ◽  
Author(s):  
B. Daum ◽  
W. Kuhlbrandt
Keyword(s):  
Electron Tomography ◽  
Thylakoid Membranes

scholarly journals Structural and functional analyses of photosystem II in the marine diatom Phaeodactylum tricornutum

2019 ◽  
Vol 116 (35) ◽  
pp. 17316-17322 ◽  
Author(s):  
Orly Levitan ◽  
Muyuan Chen ◽  
Xuyuan Kuang ◽  
Kuan Yu Cheong ◽  
Jennifer Jiang ◽  
...  
Keyword(s):  
Photosystem Ii ◽  
Spatial Organization ◽  
Higher Plants ◽  
Electron Tomography ◽  
Protein Complexes ◽  
Spatial Differentiation ◽  
Thylakoid Membranes ◽  
Marine Diatom ◽  
Red Algal ◽  
Antenna Proteins

A descendant of the red algal lineage, diatoms are unicellular eukaryotic algae characterized by thylakoid membranes that lack the spatial differentiation of stroma and grana stacks found in green algae and higher plants. While the photophysiology of diatoms has been studied extensively, very little is known about the spatial organization of the multimeric photosynthetic protein complexes within their thylakoid membranes. Here, using cryo-electron tomography, proteomics, and biophysical analyses, we elucidate the macromolecular composition, architecture, and spatial distribution of photosystem II complexes in diatom thylakoid membranes. Structural analyses reveal 2 distinct photosystem II populations: loose clusters of complexes associated with antenna proteins and compact 2D crystalline arrays of dimeric cores. Biophysical measurements reveal only 1 photosystem II functional absorption cross section, suggesting that only the former population is photosynthetically active. The tomographic data indicate that the arrays of photosystem II cores are physically separated from those associated with antenna proteins. We hypothesize that the islands of photosystem cores are repair stations, where photodamaged proteins can be replaced. Our results strongly imply convergent evolution between the red and the green photosynthetic lineages toward spatial segregation of dynamic, functional microdomains of photosystem II supercomplexes.

scholarly journals Three-Dimensional Organization of Higher-Plant Chloroplast Thylakoid Membranes Revealed by Electron Tomography

2005 ◽  
Vol 17 (9) ◽  
pp. 2580-2586 ◽  
Author(s):  
Eyal Shimoni ◽  
Ophir Rav-Hon ◽  
Itzhak Ohad ◽  
Vlad Brumfeld ◽  
Ziv Reich
Keyword(s):  
Electron Tomography ◽  
Three Dimensional ◽  
Thylakoid Membranes ◽  
Higher Plant ◽  
Plant Chloroplast

scholarly journals Charting the native architecture of Chlamydomonas thylakoid membranes with single-molecule precision

eLife ◽  
2020 ◽  
Vol 9 ◽  
Author(s):  
Wojciech Wietrzynski ◽  
Miroslava Schaffer ◽  
Dimitry Tegunov ◽  
Sahradha Albert ◽  
Atsuko Kanazawa ◽  
...  
Keyword(s):  
Single Molecule ◽  
Electron Tomography ◽  
Protein Complexes ◽  
Membrane Surface ◽  
Thylakoid Membranes ◽  
Surface Topology ◽  
Thylakoid Stacking ◽  
Molecular Forces ◽  
Photosynthetic Regulation ◽  
The Individual

Thylakoid membranes scaffold an assortment of large protein complexes that work together to harness the energy of light. It has been a longstanding challenge to visualize how the intricate thylakoid network organizes these protein complexes to finely tune the photosynthetic reactions. Previously, we used in situ cryo-electron tomography to reveal the native architecture of thylakoid membranes (Engel et al., 2015). Here, we leverage technical advances to resolve the individual protein complexes within these membranes. Combined with a new method to visualize membrane surface topology, we map the molecular landscapes of thylakoid membranes inside green algae cells. Our tomograms provide insights into the molecular forces that drive thylakoid stacking and reveal that photosystems I and II are strictly segregated at the borders between appressed and non-appressed membrane domains. This new approach to charting thylakoid topology lays the foundation for dissecting photosynthetic regulation at the level of single protein complexes within the cell.

Chloroplast Ultrastructure And Absorption Properties Of The Alga Phaeocystis Antarctica Karsten: A Qualitative Study Using Electron Tomography

1999 ◽  
Vol 5 (S2) ◽  
pp. 1258-1259
Author(s):  
Tiffany A. Moisan ◽  
Mark Ellisman ◽  
Gina Sosinsky
Keyword(s):  
Higher Plants ◽  
Electron Tomography ◽  
Spatial Relationship ◽  
Chloroplast Ultrastructure ◽  
Net Photosynthesis ◽  
Growth Conditions ◽  
Thylakoid Membranes ◽  
Light Limitation ◽  
Cell Diameter

Understanding the light-harvesting properties of algae and higher plants are a fundamental topic in photosynthesis research. Much oceanographic research has focused on characterizing the in vivo chlorophyll-specific absorption coefficient, a*ph (λ) in phytoplankton because it serves as an input variable for bio-optical modeling of photosynthesis using remote sensing instrumentation such as moorings, drifters, and satellites. Values of a*ph (λ) vary spectrally and the magnitude depends on accessory pigments, photo-protective pigments, and pigment packaging effects. Several studies have shown that the contribution of cellular characteristics to a*ph(λ) varies with growth conditions including temperature, light, and nutrients. It has been shown that a*ph (λ) values in Phaeocystis vary predictably at 4°C over light intensities under light limitation. Phaeocystis demonstrated significant pigment package effects that depended on single cell diameter and thylakoid membrane stacking. Using thick sections obtained from fixed and embedded cultures of colonial P. antarctica, we calculated tomographic reconstructions of individual chloroplasts under light-limiting conditions for net photosynthesis in order to gain an understanding of the continuity of thylakoid membranes and understand the spatial relationship between the pyrenoid, the starch containing organelle, and thylakoid membranes.

scholarly journals Charting the native architecture of thylakoid membranes with single-molecule precision

2019 ◽  
Author(s):  
Wojciech Wietrzynski ◽  
Miroslava Schaffer ◽  
Dimitry Tegunov ◽  
Sahradha Albert ◽  
Atsuko Kanazawa ◽  
...  
Keyword(s):  
Single Molecule ◽  
Electron Tomography ◽  
Protein Complexes ◽  
Membrane Surface ◽  
Thylakoid Membranes ◽  
Surface Topology ◽  
Thylakoid Stacking ◽  
Molecular Forces ◽  
Photosynthetic Regulation ◽  
Molecular Landscape

Thylakoid membranes scaffold an assortment of large protein complexes that work together to harness the energy of light to produce oxygen, NADPH, and ATP. It has been a longstanding challenge to visualize how the intricate thylakoid network organizes these protein complexes to finely tune the photosynthetic reactions. Using cryo-electron tomography to analyze membrane surface topology, we have mapped the native molecular landscape of thylakoid membranes within green algae cells. Our tomograms provide insights into the molecular forces that drive thylakoid stacking and reveal that photosystems I and II are strictly segregated at the borders between appressed and non-appressed membrane domains. This new approach to charting thylakoid topology lays the foundation for dissecting photosynthetic regulation at the level of single protein complexes within the cell.

Automated electron tomography: from data collection to image processing

1995 ◽  
Vol 53 ◽  
pp. 26-27
Author(s):  
Weiping Liu ◽  
Jennifer Fung ◽  
W.J. de Ruijter ◽  
Hans Chen ◽  
John W. Sedat ◽  
...  
Keyword(s):  
Image Processing ◽  
Data Collection ◽  
Structural Information ◽  
Imaging Technique ◽  
Electron Tomography ◽  
Ccd Camera ◽  
Automated Data Collection ◽  
Full Control ◽  
Transmission Electron ◽  
Amorphous Structures

Electron tomography is a technique where many projections of an object are collected from the transmission electron microscope (TEM), and are then used to reconstruct the object in its entirety, allowing internal structure to be viewed. As vital as is the 3-D structural information and with no other 3-D imaging technique to compete in its resolution range, electron tomography of amorphous structures has been exercised only sporadically over the last ten years. Its general lack of popularity can be attributed to the tediousness of the entire process starting from the data collection, image processing for reconstruction, and extending to the 3-D image analysis. We have been investing effort to automate all aspects of electron tomography. Our systems of data collection and tomographic image processing will be briefly described.To date, we have developed a second generation automated data collection system based on an SGI workstation (Fig. 1) (The previous version used a micro VAX). The computer takes full control of the microscope operations with its graphical menu driven environment. This is made possible by the direct digital recording of images using the CCD camera.

Practical electron tomography

1995 ◽  
Vol 53 ◽  
pp. 742-743
Author(s):  
C.L. Woodcock
Keyword(s):  
Electron Tomography ◽  
Tomographic Reconstruction ◽  
Three Dimensional ◽  
3D Shape ◽  
Computational Resources ◽  
Shape Of Particles

Despite the potential of the technique, electron tomography has yet to be widely used by biologists. This is in part related to the rather daunting list of equipment and expertise that are required. Thanks to continuing advances in theory and instrumentation, tomography is now more feasible for the non-specialist. One barrier that has essentially disappeared is the expense of computational resources. In view of this progress, it is time to give more attention to practical issues that need to be considered when embarking on a tomographic project. The following recommendations and comments are derived from experience gained during two long-term collaborative projects.Tomographic reconstruction results in a three dimensional description of an individual EM specimen, most commonly a section, and is therefore applicable to problems in which ultrastructural details within the thickness of the specimen are obscured in single micrographs. Information that can be recovered using tomography includes the 3D shape of particles, and the arrangement and dispostion of overlapping fibrous and membranous structures.

Three-Dimensional reconstruction of isolated centrosomes by automated electron tomography

1994 ◽  
Vol 52 ◽  
pp. 310-311
Author(s):  
M.B. Braunfeld ◽  
M. Moritz ◽  
B.M. Alberts ◽  
J.W. Sedat ◽  
D.A. Agard
Keyword(s):  
Electron Tomography ◽  
Three Dimensional ◽  
Vital Role ◽  
Complex Nature ◽  
Animal Cells ◽  
Microtubule Organizing Center ◽  
Nucleation Sites ◽  
Dimensional Reconstruction ◽  
Organizing Center ◽  
Resolution Model

In animal cells, the centrosome functions as the primary microtubule organizing center (MTOC). As such the centrosome plays a vital role in determining a cell's shape, migration, and perhaps most importantly, its division. Despite the obvious importance of this organelle little is known about centrosomal regulation, duplication, or how it nucleates microtubules. Furthermore, no high resolution model for centrosomal structure exists.We have used automated electron tomography, and reconstruction techniques in an attempt to better understand the complex nature of the centrosome. Additionally we hope to identify nucleation sites for microtubule growth.Centrosomes were isolated from early Drosophila embryos. Briefly, after large organelles and debris from homogenized embryos were pelleted, the resulting supernatant was separated on a sucrose velocity gradient. Fractions were collected and assayed for centrosome-mediated microtubule -nucleating activity by incubating with fluorescently-labeled tubulin subunits. The resulting microtubule asters were then spun onto coverslips and viewed by fluorescence microscopy.

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