Characterizing the supercomplex association of photosynthetic complexes in cyanobacteria

The light reactions of photosynthesis occur in thylakoid membranes that are densely packed with a series of photosynthetic complexes. The lateral organization and close association of photosynthetic complexes in native thylakoid membranes are vital for efficient light harvesting and energy transduction. Recently, analysis of the interconnections between photosynthetic complexes to form supercomplexes has garnered great interest. In this work, we report a method integrating immunoprecipitation, mass spectrometry and atomic force microscopy to identify the inter-complex associations of photosynthetic complexes in thylakoid membranes from the cyanobacterium Synechococcus elongatus PCC 7942. We characterize the preferable associations between individual photosynthetic complexes and binding proteins involved in the complex–complex interfaces, permitting us to propose the structural models of photosynthetic complex associations that promote the formation of photosynthetic supercomplexes. We also identified other potential binding proteins with the photosynthetic complexes, suggesting the highly connecting networks associated with thylakoid membranes. This study provides mechanistic insight into the physical interconnections of photosynthetic complexes and potential partners, which are crucial for efficient energy transfer and physiological acclimatization of the photosynthetic apparatus. Advanced knowledge of the protein organization and interplay of the photosynthetic machinery will inform rational design and engineering of artificial photosynthetic systems to supercharge energy production.

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Probing the biogenesis pathway and dynamics of thylakoid membranes

Nature Communications ◽

10.1038/s41467-021-23680-1 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Tuomas Huokko ◽

Tao Ni ◽

Gregory F. Dykes ◽

Deborah M. Simpson ◽

Philip Brownridge ◽

...

Keyword(s):

Plasma Membrane ◽

Photosystem I ◽

Spatial Organization ◽

Electron Flux ◽

Protein Complexes ◽

Thylakoid Membranes ◽

Thylakoid Biogenesis ◽

Photosynthetic Complexes ◽

Photosynthetic Machinery ◽

Pcc 7942

AbstractHow thylakoid membranes are generated to form a metabolically active membrane network and how thylakoid membranes orchestrate the insertion and localization of protein complexes for efficient electron flux remain elusive. Here, we develop a method to modulate thylakoid biogenesis in the rod-shaped cyanobacterium Synechococcus elongatus PCC 7942 by modulating light intensity during cell growth, and probe the spatial-temporal stepwise biogenesis process of thylakoid membranes in cells. Our results reveal that the plasma membrane and regularly arranged concentric thylakoid layers have no physical connections. The newly synthesized thylakoid membrane fragments emerge between the plasma membrane and pre-existing thylakoids. Photosystem I monomers appear in the thylakoid membranes earlier than other mature photosystem assemblies, followed by generation of Photosystem I trimers and Photosystem II complexes. Redistribution of photosynthetic complexes during thylakoid biogenesis ensures establishment of the spatial organization of the functional thylakoid network. This study provides insights into the dynamic biogenesis process and maturation of the functional photosynthetic machinery.

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Atomic force microscopy visualizes mobility of photosynthetic proteins in grana thylakoid membranes

10.1101/426759 ◽

2018 ◽

Author(s):

Bibiana Onoa ◽

Shingo Fukuda ◽

Masakazu Iwai ◽

Carlos Bustamante ◽

Krishna K. Niyogi

Keyword(s):

High Speed ◽

Spinacia Oleracea ◽

Protein Complexes ◽

Rotational Diffusion ◽

Thylakoid Membranes ◽

Spatiotemporal Resolution ◽

Force Microscopy ◽

Photosynthetic Complexes ◽

Protein Density ◽

Photosynthetic Protein Complexes

ABSTRACTThylakoid membranes in chloroplasts contain photosynthetic protein complexes that convert light energy into chemical energy. Photosynthetic protein complexes are considered to undergo structural reorganization to maintain the efficiency of photochemical reactions. A detailed description of the mobility of photosynthetic complexes in real-time is necessary to understand how macromolecular organization of the membrane is altered by environmental fluctuations. Here, we used high-speed atomic force microscopy to visualize and characterize the in situ mobility of individual protein complexes in grana thylakoid membranes isolated from Spinacia oleracea. Our observations reveal that these membranes can harbor complexes with at least two distinctive classes of mobility. A large fraction of grana membranes contained proteins with quasi-static mobility, exhibiting molecular displacements smaller than 10 nm2. In the remaining fraction, the protein mobility is variable with molecular displacements of up to 100 nm2. This visualization at high-spatiotemporal resolution enabled us to estimate an average diffusion coefficient of ∼1 nm2 s-1. Interestingly, both confined and Brownian diffusion models could describe the protein mobility of the second group of membranes. We also provide the first direct evidence of rotational diffusion of photosynthetic complexes. The rotational diffusion of photosynthetic complexes could be an adaptive response to the high protein density in the membrane to guarantee the efficiency of electron transfer reactions. This characterization of the mobility of individual photosynthetic complexes in grana membranes establishes a foundation that could be adapted to study the dynamics of the complexes inside the intact and photosynthetically functional thylakoid membranes to be able to understand its structural responses to diverse environmental fluctuations.STATEMENT OF SIGNIFICANCEWe characterized the dynamics of individual photosynthetic protein complexes in grana thylakoid membranes from Spinacia oleracea by high-speed atomic microscopy (HS-AFM). Direct visualization at high spatiotemporal resolution unveils that the mobility of photosynthetic proteins is heterogeneous but governed by the confinement effect imposed by the high protein density in the thylakoid membrane. The photosynthetic complexes display rotational diffusion, which might be a consequence of the crowded environment in the membrane and a mechanism to sustain an efficient electron transfer chain.

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Observe Them in Their Native Habitat: Atomic Force Microscopy of Photosynthetic Complexes in Thylakoid Membranes

The Plant Cell ◽

10.1105/tpc.114.130161 ◽

2014 ◽

Vol 26 (7) ◽

pp. 2727-2727

Author(s):

Nancy R. Hofmann

Keyword(s):

Atomic Force Microscopy ◽

Thylakoid Membranes ◽

Force Microscopy ◽

Native Habitat ◽

Atomic Force ◽

Photosynthetic Complexes

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Complete Replacement of the Galactolipid Biosynthesis Pathway with a Plant-Type Pathway in the Cyanobacterium Synechococcus elongatus PCC 7942

Plant and Cell Physiology ◽

10.1093/pcp/pcaa090 ◽

2020 ◽

Vol 61 (9) ◽

pp. 1661-1668

Author(s):

Egi Tritya Apdila ◽

Shukumi Inoue ◽

Mie Shimojima ◽

Koichiro Awai

Keyword(s):

Chlorophyll Content ◽

Membrane Lipids ◽

Thylakoid Membranes ◽

Synechococcus Elongatus ◽

Biosynthesis Pathway ◽

Plant Type ◽

Complete Replacement ◽

Essential Components ◽

Synechococcus Elongatus Pcc 7942 ◽

Pcc 7942

Abstract Monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG) are the major components of thylakoid membranes and well-conserved from cyanobacteria to chloroplasts. However, cyanobacteria and chloroplasts synthesize these galactolipids using different pathways and enzymes, but they are believed to share a common ancestor. This fact implies that there was a replacement of the cyanobacterial galactolipid biosynthesis pathway during the evolution of a chloroplast. In this study, we first replaced the cyanobacterial MGDG biosynthesis pathway in a model cyanobacterium, Synechococcus elongatus PCC 7942, with the corresponding plant-type pathway. No obvious phenotype was observed under the optimum growth condition, and the content of membrane lipids was not largely altered in the transformants. We next replaced the cyanobacterial DGDG biosynthesis pathway with the corresponding plant-type pathway using the strain described above and isolated the strain harboring the replaced plant-type pathway instead of the whole galactolipid biosynthesis pathway. This transformant, SeGPT, can grow photoautotrophically, indicating that cyanobacterial galactolipid biosynthesis pathways can be functionally complemented by the corresponding plant-type pathways and that the lipid products MGDG and DGDG, and not biosynthesis pathways, are important. While SeGPT does not show strong growth retardation, the strain has low cellular chlorophyll content but it retained a similar oxygen evolution rate per chlorophyll content compared with the wild type. An increase in total membrane lipid content was observed in SeGPT, which was caused by a significant increase in DGDG content. SeGPT accumulated carotenoids from the xanthophyll groups. These results suggest that cyanobacteria have the capacity to accept other pathways to synthesize essential components of thylakoid membranes.

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Interplay between formation of photosynthetic complexes and expression of genes for iron–sulfur cluster assembly in Rhodobacter sphaeroides?

Photosynthesis Research ◽

10.1007/s11120-020-00789-w ◽

2020 ◽

Vol 147 (1) ◽

pp. 39-48

Author(s):

Xin Nie ◽

Andreas Jäger ◽

Janek Börner ◽

Gabriele Klug

Keyword(s):

Rhodobacter Sphaeroides ◽

Cluster Formation ◽

Rna Stability ◽

Photosynthetic Apparatus ◽

Growth Conditions ◽

Cluster Assembly ◽

Iron Sulfur Cluster ◽

Expression Of Genes ◽

Photosynthetic Complexes ◽

Photosynthesis Genes

AbstractFormation of photosynthetic complexes leads to a higher demand for Fe–S clusters. We hypothesized that in the facultative phototrophic alpha-proteobacterium Rhodobacter sphaeroides expression of the isc-suf operon for Fe–S cluster formation may be increased under conditions that promote formation of photosynthetic complexes and that, vice versa, lack of the IscR regulator may also affect photosynthesis gene expression. To test this hypothesis, we monitored the activities of the isc-suf sense and anti-sense promoters under different growth conditions and in mutants which are impaired in formation of photosynthetic complexes. We also tested expression of photosynthesis genes in a mutant lacking the IscR regulator. Our results are not in agreement with a co-regulation of the Isc-Suf system and the photosynthetic apparatus at level of transcription. We provide evidence that, coordination of the systems occurs at post-transcriptional levels. Increased levels of isc-suf mRNAs under conditions promoting formation of photosynthetic complexes are due to higher RNA stability.

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Growth and Characterization of (Tb,Yb) Co-Doping Sprayed ZnO Thin Films

Crystals ◽

10.3390/cryst10030169 ◽

2020 ◽

Vol 10 (3) ◽

pp. 169 ◽

Cited By ~ 1

Author(s):

A. El hat ◽

I. Chaki ◽

R. Essajai ◽

A. Mzerd ◽

G. Schmerber ◽

...

Keyword(s):

Thin Films ◽

Secondary Phase ◽

Hexagonal Wurtzite Structure ◽

Zno Thin Films ◽

Spray Pyrolysis Method ◽

Efficient Energy Transfer ◽

Force Microscopy ◽

Co Doping ◽

Glass Substrates ◽

Hall Effect Measurements

Structural, optical and electrical properties of (ytterbium/terbium) co-doped ZnO thin films deposited on glass substrates using the spray pyrolysis method were investigated. The films exhibited the hexagonal wurtzite structure with a preferential orientation along (002) direction. No secondary phase was observed in the X-ray diffraction detection limit. Atomic force microscopy (AFM) was performed and root means square roughness (RMS) of our samples decreased with terbium content. Photoluminescence measurements showed a luminescence band at 980 nm which is characteristic of Yb3+ transition between the electronic levels 2F5/2 to 2F7/2. This is experimental evidence for an efficient energy transfer from the ZnO matrix to Yb. Hall Effect measurements gave a low electrical resistivity value around 6.0 × 10−3 Ω.cm. Such characteristics make these films of interest to photovoltaic devices.

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When dendrimers are not better – rational design of nanolayers for high-performance organic electronic devices

Nanoscale ◽

10.1039/c8nr09241a ◽

2019 ◽

Vol 11 (10) ◽

pp. 4463-4470 ◽

Cited By ~ 1

Author(s):

Maxim A. Shcherbina ◽

Oleg V. Borshchev ◽

Alexandra P. Pleshkova ◽

Sergei A. Ponomarenko ◽

Sergei N. Chvalun

Keyword(s):

High Performance ◽

Rational Design ◽

Electronic Devices ◽

Carbosilane Dendrimers ◽

Scanning Calorimetry ◽

Organic Electronic Devices ◽

X Ray ◽

Force Microscopy ◽

X Ray Scattering ◽

Atomic Force

Several generations of carbosilane dendrimers with quaterthiophene end groups were studied by X-ray scattering, differential scanning calorimetry, polarizing optical and atomic force microscopy and molecular modelling.

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Effect of Membrane Fluidity on Photoinhibition of Isolated Thylakoids Membranes at Room and Low Temperature

Zeitschrift für Naturforschung C ◽

10.1515/znc-2001-5-609 ◽

2001 ◽

Vol 56 (5-6) ◽

pp. 369-374 ◽

Cited By ~ 4

Author(s):

Maya Velitchkova ◽

Antoaneta Popova ◽

Tzvetelina Markova

Keyword(s):

Low Temperature ◽

Membrane Fluidity ◽

Light Stress ◽

Photosynthetic Apparatus ◽

Chemical Properties ◽

Thylakoid Membranes ◽

High Light Intensity ◽

Photochemical Activity ◽

High Light ◽

Time Dependencies

The relationship between thylakoid membrane fluidity and the process of photoinhibition at room and low (4 °C) temperature was investigated. Two different membrane perturbing agents - cholesterol and benzylalcohol were applied to manipulate the fluidity of isolated pea thylakoids. The photochemical activity of photosystem I (PSI) and photosystem II (PSII), polarographically determined, were measured at high light intensity for different time of illumination at both temperatures. The exposure of cholesterol- and benzylalcohol-treated thylakoid membranes to high light intensities resulted in inhibition of both studied photochemical activities, being more pronounced for PSII compared to PSI. Time dependencies of inhibition of PSI and PSII electron transport rates for untreated and membranes with altered fluidity were determined at 20 °C and 4 °C. The effect is more pronounced for PSII activity during low-temperature photoinhibition. The data are discussed in terms of the determining role of physico-chemical properties of thylakoid membranes for the response of photosynthetic apparatus to light stress.

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