The Experts below are selected from a list of 243 Experts worldwide ranked by ideXlab platform
Per-Åke Albertsson - One of the best experts on this subject based on the ideXlab platform.
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the constant proportion of Grana and stroma lamellae in plant chloroplasts
Physiologia Plantarum, 2004Co-Authors: Per-Åke Albertsson, Eva AndreassonAbstract:The relative proportion of stroma lamellae and Grana end membranes was determined from electron micrographs of 58 chloroplasts from 21 different plant species. The percentage of Grana end membranes varied between 1 and 21% of the total thylakoid membrane indicating a large variation in the size of Grana stacks. By contrast the stroma lamellae account for 20.3 +/- 2.5 (SD)% of the total thylakoid membrane. A plot of percentage stroma lamellae against percentage of Grana end membranes fits a straight line with a slope of zero showing that the proportion of stroma lamellae is independent of the size of the Grana stacks. That stroma lamellae account for about 20% of the thylakoid membrane is in agreement with fragmentation and separation analysis (Gadjieva et al. Biochim. Biophys. Acta 144: 92-100, 1999). Chloroplasts from spinach, grown under high or low light, were fragmented by sonication and separated by countercurrent distribution into two vesicle populations originating from Grana and stroma lamellae plus end membranes, respectively. The separation diagrams were very similar lending independent support for the notion that the proportion of stroma lamellae is constant. The results are discussed in relation to the composition and function of the chloroplast in plants grown under different environmental conditions, and in relation to a recent quantitative model for the thylakoid (Albertsson, Trends Plant Sci. 6: 349-354, 2001). (Less)
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quantification of photosystem i and ii in different parts of the thylakoid membrane from spinach
Biochimica et Biophysica Acta, 2004Co-Authors: Ravi Danielsson, Per-Åke Albertsson, Fikret Mamedov, Stenbjörn StyringAbstract:Abstract: Electron paramagnetic resonance (EPR) was used to quantify Photosystem I (PSI) and PSII in vesicles originating from a series of well-defined but different domains of the thylakoid membrane in spinach prepared by non-detergent techniques. Thylakoids from spinach were fragmented by sonication and separated by aqueous polymer two-phase partitioning into vesicles originating from Grana and stroma lamellae. The Grana vesicles were further sonicated and separated into two vesicle preparations originating from the Grana margins and the appressed domains of Grana (the Grana core), respectively. PSI and PSII were determined in the same samples from the maximal size of the EPR signal from P700(+) and Y-D(.), respectively. The following PSI/PSII ratios were found: thylakoids, 1.13; Grana vesicles, 0.43; Grana core, 0.25; Grana margins, 1.28; stroma lamellae 3.10. In a sub-fraction of the stroma lamellae, denoted Y-100, PSI was highly enriched and the PSI/PSII ratio was 13. The antenna size of the respective photosystems was calculated from the experimental data and the assumption that a PSII center in the stroma lamellae (PSIIbeta) has an antenna size of 100 Ch1. This gave the following results: PSI in Grana margins (PSIalpha) 300, PSI (PSIbeta) in stroma lamellae 214, PSII in Grana core (PSIIalpha) 280. The results suggest that PSI in Grana margins have two additional light-harvesting complex 11 (LHCII) trimers per reaction center compared to PSI in stroma lamellae, and that PSII in Grana has four LHCII trimers per monomer compared to PSII in stroma lamellae. Calculation of the total chlorophyll associated with PSI and PSII, respectively, suggests that more chlorophyll (about 10%) is associated with PSI than with PSII. (C) 2003 Elsevier B.V. All rights reserved. (Less)
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The constant proportion of Grana and stroma lamellae in plant chloroplasts.
Physiologia plantarum, 2004Co-Authors: Per-Åke Albertsson, Eva AndreassonAbstract:The relative proportion of stroma lamellae and Grana end membranes was determined from electron micrographs of 58 chloroplasts from 21 different plant species. The percentage of Grana end membranes varied between 1 and 21% of the total thylakoid membrane indicating a large variation in the size of Grana stacks. By contrast the stroma lamellae account for 20.3 +/- 2.5 (sd)% of the total thylakoid membrane. A plot of percentage stroma lamellae against percentage of Grana end membranes fits a straight line with a slope of zero showing that the proportion of stroma lamellae is independent of the size of the Grana stacks. That stroma lamellae account for about 20% of the thylakoid membrane is in agreement with fragmentation and separation analysis (Gadjieva et al. Biochim. Biophys. Acta 144: 92-100, 1999). Chloroplasts from spinach, grown under high or low light, were fragmented by sonication and separated by countercurrent distribution into two vesicle populations originating from Grana and stroma lamellae plus end membranes, respectively. The separation diagrams were very similar lending independent support for the notion that the proportion of stroma lamellae is constant. The results are discussed in relation to the composition and function of the chloroplast in plants grown under different environmental conditions, and in relation to a recent quantitative model for the thylakoid (Albertsson, Trends Plant Sci. 6: 349-354, 2001).
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Chloroplasts largely devoid of Grana stacks have full photosynthetic capability
Photosynthesis: Mechanisms and Effects, 1998Co-Authors: Lars Olof Björn, Fikret Mamedov, Stenbjörn Styring, Per-Åke AlbertssonAbstract:Thylakoids of most plants are spatially differentiated into stroma lamellae and Grana stacks. According to studies on the development of the thylakoid membrane, the stroma lamellae are formed first from the inner membrane of proplastids under light illumination and serve as precursors for the formation of Granal stacks which are built-up through multiple-stage development. Hitherto, the necessity of Grana-stack formation is not fully understood [1]. It has also been demonstrated that the membrane organization of chloroplasts is changeable, accompanying certain environmental stimuli during long-term acclimation of plants to the surroundings [2]. The ratio between the Grana stacks and the stroma lamellae in chloroplast therefore is a dynamic feature [2]. In this communication, it is reported that (I) Dimorphotheca pluvialis (DP), which originally grows at African desert areas has very poor membrane stacking in chloroplast but possesses a full photochemical capacit (II) Supplementary UV-B irradiation during plant growth causes remarkable increment in membrane stacking of the thylakoids isolated from this plant species.
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the structure and function of the chloroplast photosynthetic membrane a model for the domain organization
Photosynthesis Research, 1995Co-Authors: Per-Åke AlbertssonAbstract:Recent work on the domain organization of the thylakoid is reviewed and a model for the thylakoid of higher plants is presented. According to this model the thylakoid membrane is divided into three main domains: the stroma lamellae, the Grana margins and the Grana core (partitions). These have different biochemical compositions and have specialized functions. Linear electron transport occurs in the Grana while cyclic electron transport is restricted to the stroma lamellae. This model is based on the following results and considerations. (1) There is no good candidate for a long-range mobile redox carrier between PS II in the Grana and PS I in the stroma lamellae. The lateral diffusion of plastoquinone and plastocyanin is severely restricted by macromolecular crowding in the membrane and the lumen respectively. (2) There is an excess of 14±18% chlorophyll associated with PS I over that of PS II. This excess is assumed to be localized in the stroma lamellae where PS I drives cyclic electron transport. (3) For several plant species, the stroma lamellae account for 20±3% of the thylakoid membrane and the Grana (including the appressed regions, margins and end membranes) for the remaining 80%. The amount of stroma lamellae (20%) corresponds to the excess (14–18%) of chlorophyll associated with PS I. (4) The model predicts a quantum requirement of about 10 quanta per oxygen molecule evolved, which is in good agreement with experimentally observed values. (5) There are at least two pools of each of the following components: PS I, PS II, cytochrome bf complex, plastocyanin, ATP synthase and plastoquinone. One pool is in the Grana and the other in the stroma compartments. So far, it has been demonstrated that the PS I, PS II and cytochrome bf complexes each differ in their respective pools.
Helmut Kirchhoff - One of the best experts on this subject based on the ideXlab platform.
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Surface charge dynamics in photosynthetic membranes and the structural consequences
Nature Plants, 2017Co-Authors: Sujith Puthiyaveetil, Bart Van Oort, Helmut KirchhoffAbstract:The strict stacking of plant photosynthetic membranes into Granal structures plays a vital role in energy conversion. The molecular forces that lead to Grana stacking, however, are poorly understood. Here we evaluate the interplay between repulsive electrostatic ( F _el) and attractive van der Waals ( F _vdWaals) forces in Grana stacking. In contrast to previous reports, we find that the physicochemical balance between attractive and repulsive forces fully explains Grana stacking. Extending the force balance analysis to lateral interactions within the oxygen-evolving photosystem II (PSII)–light harvesting complex II (LHCII) supercomplex reveals that supercomplex stability is very sensitive to F _el changes. F _el is highly dynamic, increasing up to 1.7-fold on addition of negative charges by phosphorylation of Grana-hosted proteins. We show that this leads to specific destabilization of the supercomplex, and that changes in F _el have contrasting effects on vertical stacking and lateral intramembrane organization. This enables discrete biological control of these central structural features. It is shown that the balance of van der Waals and electrostatic forces can explain Grana stacking in chloroplasts. Electrostatic forces vary with phosphorylation of proteins, producing contrasting effects on stacking and intra-membrane organization.
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Significance of Protein Ordering in Grana Thylakoids for Light-Harvesting by Photosystem II and Protein Mobility
Advanced Topics in Science and Technology in China, 2013Co-Authors: Stefanie Tietz, Chris Kinzel, Robert Yarbrough, Helmut KirchhoffAbstract:Controlled by environmental factors, proteins in the Grana thylakoid subcompartment in chloroplasts can rearrange into highly ordered semicrystalline arrays. The functional implications of these arrays are analyzed by using an Arabidopsis fatty acid desaturase (fad5) mutant as a model system, which constitutively forms these crystalline structures in thylakoid membranes. Stoichiometric analysis of the fad5 thylakoid membranes reveal the existence of two membrane domains in Grana (domains with PSII crystals and LHCII-enriched domains). Probing the light-harvesting of PSII by chlorophyll fluorescence induction indicates a very efficient energy transfer between these domains in the mutant probably by transversal energy transfer across the aqueous stromal partition gap between adjacent Grana discs. Furthermore, the protein mobility in fad5 measured by fluorescence recovery after photobleaching is higher compared to WT plants. This gives evidence for a high protein mobility in LHCII-enriched Grana regions.
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Architectural switch in plant photosynthetic membranes induced by light stress
Proceedings of the National Academy of Sciences of the United States of America, 2012Co-Authors: Miroslava Herbstová, Stefanie Tietz, Christopher R. Kinzel, Maria V. Turkina, Helmut KirchhoffAbstract:Unavoidable side reactions of photosynthetic energy conversion can damage the water-splitting photosystem II (PSII) holocomplex embedded in the thylakoid membrane system inside chloroplasts. Plant survival is crucially dependent on an efficient molecular repair of damaged PSII realized by a multistep repair cycle. The PSII repair cycle requires a brisk lateral protein traffic between stacked Grana thylakoids and unstacked stroma lamellae that is challenged by the tight stacking and low protein mobility in Grana. We demonstrated that high light stress induced two main structural changes that work synergistically to improve the accessibility between damaged PSII in Grana and its repair machinery in stroma lamellae: lateral shrinkage of Grana diameter and increased protein mobility in Grana thylakoids. It follows that high light stress triggers an architectural switch of the thylakoid network that is advantageous for swift protein repair. Studies of the thylakoid kinase mutant stn8 and the double mutant stn7/8 demonstrate the central role of protein phosphorylation for the structural alterations. These findings are based on the elaboration of mathematical tools for analyzing confocal laser-scanning microscopic images to study changes in the sophisticated thylakoid architecture in intact protoplasts.
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dynamic control of protein diffusion within the Granal thylakoid lumen
Proceedings of the National Academy of Sciences of the United States of America, 2011Co-Authors: Helmut Kirchhoff, Miroslava Herbstová, Christopher Hall, Magnus Wood, Onie Tsabari, Reinat Nevo, Dana Charuvi, Eyal Shimoni, Ziv ReichAbstract:The machinery that conducts the light-driven reactions of oxygenic photosynthesis is hosted within specialized paired membranes called thylakoids. In higher plants, the thylakoids are segregated into two morphological and functional domains called Grana and stroma lamellae. A large fraction of the luminal volume of the Granal thylakoids is occupied by the oxygen-evolving complex of photosystem II. Electron microscopy data we obtained on dark- and light-adapted Arabidopsis thylakoids indicate that the Granal thylakoid lumen significantly expands in the light. Models generated for the organization of the oxygen-evolving complex within the Granal lumen predict that the light-induced expansion greatly alleviates restrictions imposed on protein diffusion in this compartment in the dark. Experiments monitoring the redox kinetics of the luminal electron carrier plastocyanin support this prediction. The impact of the increase in protein mobility within the Granal luminal compartment in the light on photosynthetic electron transport rates and processes associated with the repair of photodamaged photosystem II complexes is discussed.
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Efficient light harvesting by photosystem II requires an optimized protein packing density in Grana thylakoids.
The Journal of biological chemistry, 2010Co-Authors: Silvia Haferkamp, Winfried Haase, Andrew A. Pascal, Herbert Van Amerongen, Helmut KirchhoffAbstract:A recently developed technique for dilution of the naturally high protein packing density in isolated Grana membranes was applied to study the dependence of the light harvesting efficiency of photosystem (PS) II on macromolecular crowding. Slight dilution of the protein packing from 80% area fraction to the value found in intact Grana thylakoids (70%) leads to an improved functionality of PSII (increased antenna size, enhanced connectivity between reaction centers). Further dilution induces a functional disconnection of light-harvesting complex (LHC) II from PSII. It is concluded that efficient light harvesting by PSII requires an optimal protein packing density in Grana membranes that is close to 70%. We hypothesize that the decreased efficiency in overcrowded isolated Grana thylakoids is caused by excited state quenching in LHCII, which has previously been correlated with neoxanthin distortion. Resonance Raman spectroscopy confirms this increase in neoxanthin distortion in overcrowded Grana as compared with intact thylakoids. Furthermore, analysis of the changes in the antenna size in highly diluted membranes indicates a lipid-induced dissociation of up to two trimeric LHCII from PSII, leaving one trimer connected. This observation supports a hierarchy of LHCII-binding sites on PSII.
Eva Andreasson - One of the best experts on this subject based on the ideXlab platform.
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the constant proportion of Grana and stroma lamellae in plant chloroplasts
Physiologia Plantarum, 2004Co-Authors: Per-Åke Albertsson, Eva AndreassonAbstract:The relative proportion of stroma lamellae and Grana end membranes was determined from electron micrographs of 58 chloroplasts from 21 different plant species. The percentage of Grana end membranes varied between 1 and 21% of the total thylakoid membrane indicating a large variation in the size of Grana stacks. By contrast the stroma lamellae account for 20.3 +/- 2.5 (SD)% of the total thylakoid membrane. A plot of percentage stroma lamellae against percentage of Grana end membranes fits a straight line with a slope of zero showing that the proportion of stroma lamellae is independent of the size of the Grana stacks. That stroma lamellae account for about 20% of the thylakoid membrane is in agreement with fragmentation and separation analysis (Gadjieva et al. Biochim. Biophys. Acta 144: 92-100, 1999). Chloroplasts from spinach, grown under high or low light, were fragmented by sonication and separated by countercurrent distribution into two vesicle populations originating from Grana and stroma lamellae plus end membranes, respectively. The separation diagrams were very similar lending independent support for the notion that the proportion of stroma lamellae is constant. The results are discussed in relation to the composition and function of the chloroplast in plants grown under different environmental conditions, and in relation to a recent quantitative model for the thylakoid (Albertsson, Trends Plant Sci. 6: 349-354, 2001). (Less)
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The constant proportion of Grana and stroma lamellae in plant chloroplasts.
Physiologia plantarum, 2004Co-Authors: Per-Åke Albertsson, Eva AndreassonAbstract:The relative proportion of stroma lamellae and Grana end membranes was determined from electron micrographs of 58 chloroplasts from 21 different plant species. The percentage of Grana end membranes varied between 1 and 21% of the total thylakoid membrane indicating a large variation in the size of Grana stacks. By contrast the stroma lamellae account for 20.3 +/- 2.5 (sd)% of the total thylakoid membrane. A plot of percentage stroma lamellae against percentage of Grana end membranes fits a straight line with a slope of zero showing that the proportion of stroma lamellae is independent of the size of the Grana stacks. That stroma lamellae account for about 20% of the thylakoid membrane is in agreement with fragmentation and separation analysis (Gadjieva et al. Biochim. Biophys. Acta 144: 92-100, 1999). Chloroplasts from spinach, grown under high or low light, were fragmented by sonication and separated by countercurrent distribution into two vesicle populations originating from Grana and stroma lamellae plus end membranes, respectively. The separation diagrams were very similar lending independent support for the notion that the proportion of stroma lamellae is constant. The results are discussed in relation to the composition and function of the chloroplast in plants grown under different environmental conditions, and in relation to a recent quantitative model for the thylakoid (Albertsson, Trends Plant Sci. 6: 349-354, 2001).
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Localization of cytochrome f in the thylakoid membrane: evidence for multiple domains
Biochimica et Biophysica Acta (BBA) - Bioenergetics, 1991Co-Authors: Per-Åke Albertsson, Eva Andreasson, Per SvenssonAbstract:Abstract Thylakoids from spinach were fragmented by sonication and the viscles so obtained were separated into different populations by aqueous two-phase partitioning using the dextran-poly(ethylene glycol) system. The different vesicle populations were analyzed with respect to the concentrations of P700 and cytochrome. The P700 content varied between 0.93 (PS-II-enriched Grana vesicles named BS) and 4.85 (stroma membrane vesicles named Y100) mmol per mol chlorophyll. The cytochrome f content varied between 1.92 (vesicles originating from the Grana periphery, named 120S vesicles) and 3.12 (PS-II-enriched Grana vesicles named BS) mmol/mol chlorophyll. A plot of the P700 content against the cytochrome f content of the different vesicle populations was compared with hypothetical models of membrane vesicles. The results show that the thylakoid membrane consists of at least three different domains with respect to cytochrome f. These are suggested to be: (1) the stroma lamellae; (2) the core of the partition region of the Grana; and (3) a peripheral annulus of the Grana discs including the margins (and perhaps also the end membranes).
Conrad W. Mullineaux - One of the best experts on this subject based on the ideXlab platform.
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protein diffusion and macromolecular crowding in thylakoid membranes
Plant Physiology, 2008Co-Authors: Helmut Kirchhoff, Silvia Haferkamp, John F Allen, D B A Epstein, Conrad W. MullineauxAbstract:The photosynthetic light reactions of green plants are mediated by chlorophyll-binding protein complexes located in the thylakoid membranes within the chloroplasts. Thylakoid membranes have a complex structure, with lateral segregation of protein complexes into distinct membrane regions known as the Grana and the stroma lamellae. It has long been clear that some protein complexes can diffuse between the Grana and the stroma lamellae, and that this movement is important for processes including membrane biogenesis, regulation of light harvesting, and turnover and repair of the photosynthetic complexes. In the Grana membranes, diffusion may be problematic because the protein complexes are very densely packed (approximately 75% area occupation) and semicrystalline protein arrays are often observed. To date, direct measurements of protein diffusion in green plant thylakoids have been lacking. We have developed a form of fluorescence recovery after photobleaching that allows direct measurement of the diffusion of chlorophyll-protein complexes in isolated Grana membranes from Spinacia oleracea. We show that about 75% of fluorophores are immobile within our measuring period of a few minutes. We suggest that this immobility is due to a protein network covering a whole Grana disc. However, the remaining fraction is surprisingly mobile (diffusion coefficient 4.6 +/- 0.4 x 10(-11) cm(2) s(-1)), which suggests that it is associated with mobile proteins that exchange between the Grana and stroma lamellae within a few seconds. Manipulation of the protein-lipid ratio and the ionic strength of the buffer reveals the roles of macromolecular crowding and protein-protein interactions in restricting the mobility of Grana proteins.
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Function and evolution of Grana.
Trends in plant science, 2005Co-Authors: Conrad W. MullineauxAbstract:Chloroplasts are descended from cyanobacteria, and they retain many features of the cyanobacterial photosynthetic apparatus. However, land-plant chloroplasts have a strikingly different thylakoid membrane organization to that of cyanobacteria. Usually the two photosystems are laterally segregated; Photosystem II is concentrated in complex stacked-membrane structures known as Grana. The function of Grana has long been debated. Recent studies on membrane organization in chloroplasts, cyanobacteria and purple bacteria now offer a new perspective. I argue that Grana allow the presence of a large light-harvesting antenna for Photosystem II, without excessively restricting electron transport. Other organisms solve this problem in different ways. Land plants evolved from macroalgae that were adapted to high light conditions; they evolved Grana as a new solution to the problem of efficient photosynthesis in shade.
L. Andrew Staehelin - One of the best experts on this subject based on the ideXlab platform.
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A brief history of how microscopic studies led to the elucidation of the 3D architecture and macromolecular organization of higher plant thylakoids
Photosynthesis Research, 2020Co-Authors: L. Andrew Staehelin, Dominick J. PaolilloAbstract:Microscopic studies of chloroplasts can be traced back to the year 1678 when Antonie van Leeuwenhoek reported to the Royal Society in London that he saw green globules in grass leaf cells with his single-lens microscope. Since then, microscopic studies have continued to contribute critical insights into the complex architecture of chloroplast membranes and how their structure relates to function. This review is organized into three chronological sections: During the classic light microscope period (1678–1940), the development of improved microscopes led to the identification of green Grana, a colorless stroma, and a membrane envelope. More recent (1990–2020) chloroplast dynamic studies have benefited from laser confocal and 3D-structured illumination microscopy. The development of the transmission electron microscope (1940–2000) and thin sectioning techniques demonstrated that Grana consist of stacks of closely appressed Grana thylakoids interconnected by non-appressed stroma thylakoids. When the stroma thylakoids were shown to spiral around the Grana stacks as multiple right-handed helices, it was confirmed that the membranes of a chloroplast are all interconnected. Freeze-fracture and freeze-etch methods verified the helical nature of the stroma thylakoids, while also providing precise information on how the electron transport chain and ATP synthase complexes are non-randomly distributed between Grana and stroma membrane regions. The last section (2000–2020) focuses on the most recent discoveries made possible by atomic force microscopy of hydrated membranes, and electron tomography and cryo-electron tomography of cryofixed thylakoids. These investigations have provided novel insights into thylakoid architecture and plastoglobules (summarized in a new thylakoid model), while also producing molecular-scale views of Grana and stroma thylakoids in which individual functional complexes can be identified.
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Three-dimensional architecture of Grana and stroma thylakoids of higher plants as determined by electron tomography
Plant physiology, 2011Co-Authors: Jotham R. Austin, L. Andrew StaehelinAbstract:We have investigated the three-dimensional (3D) architecture of the thylakoid membranes of Arabidopsis (Arabidopsis thaliana), tobacco (Nicotiana tabacum), and spinach (Spinacia oleracea) with a resolution of approximately 7 nm by electron tomography of high-pressure-frozen/freeze-substituted intact chloroplasts. Higher-plant thylakoids are differentiated into two interconnected and functionally distinct domains, the photosystem II/light-harvesting complex II-enriched stacked Grana thylakoids and the photosystem I/ATP synthase-enriched, nonstacked stroma thylakoids. The Grana thylakoids are organized in the form of cylindrical stacks and are connected to the stroma thylakoids via tubular junctions. Our data confirm that the stroma thylakoids are wound around the Grana stacks in the form of multiple, right-handed helices at an angle of 20° to 25° as postulated by a helical thylakoid model. The junctional connections between the Grana and stroma thylakoids all have a slit-like architecture, but their size varies tremendously from approximately 15 × 30 nm to approximately 15 × 435 nm, which is approximately 5 times larger than seen in chemically fixed thylakoids. The variable slit length results in less periodicity in Grana/stroma thylakoid organization than proposed in the original helical model. The stroma thylakoids also exhibit considerable architectural variability, which is dependent, in part, on the number and the orientation of adjacent Grana stacks to which they are connected. Whereas some stroma thylakoids form solid, sheet-like bridges between adjacent Grana, others exhibit a branching geometry with small, more tubular sheet domains also connecting adjacent, parallel stroma thylakoids. We postulate that the tremendous variability in size of the junctional slits may reflect a novel, active role of junctional slits in the regulation of photosynthetic function. In particular, by controlling the size of junctional slits, plants could regulate the flow of ions and membrane molecules between Grana and stroma thylakoid membrane domains.
