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Plants (Basel, Switzerland) Mar 2023Photosynthesis constitutes the only known natural process that captures the solar energy to convert carbon dioxide and water into biomass. The primary reactions of... (Review)
Review
Photosynthesis constitutes the only known natural process that captures the solar energy to convert carbon dioxide and water into biomass. The primary reactions of photosynthesis are catalyzed by the photosystem II (PSII) and photosystem I (PSI) complexes. Both photosystems associate with antennae complexes whose main function is to increase the light-harvesting capability of the core. In order to maintain optimal photosynthetic activity under a constantly changing natural light environment, plants and green algae regulate the absorbed photo-excitation energy between PSI and PSII through processes known as state transitions. State transitions represent a short-term light adaptation mechanism for balancing the energy distribution between the two photosystems by relocating light-harvesting complex II (LHCII) proteins. The preferential excitation of PSII (state 2) results in the activation of a chloroplast kinase which in turn phosphorylates LHCII, a process followed by the release of phosphorylated LHCII from PSII and its migration to PSI, thus forming the PSI-LHCI-LHCII supercomplex. The process is reversible, as LHCII is dephosphorylated and returns to PSII under the preferential excitation of PSI. In recent years, high-resolution structures of the PSI-LHCI-LHCII supercomplex from plants and green algae were reported. These structural data provide detailed information on the interacting patterns of phosphorylated LHCII with PSI and on the pigment arrangement in the supercomplex, which is critical for constructing the excitation energy transfer pathways and for a deeper understanding of the molecular mechanism of state transitions progress. In this review, we focus on the structural data of the state 2 supercomplex from plants and green algae and discuss the current state of knowledge concerning the interactions between antenna and the PSI core and the potential energy transfer pathways in these supercomplexes.
PubMed: 36904032
DOI: 10.3390/plants12051173 -
MSphere Aug 2021Photosynthetic and their descendants are the only known organisms capable of oxygenic photosynthesis. Their metabolism permanently changed the Earth's surface and the...
Photosynthetic and their descendants are the only known organisms capable of oxygenic photosynthesis. Their metabolism permanently changed the Earth's surface and the evolutionary trajectory of life, but little is known about their evolutionary history. Genomes of the , an order of deeply divergent photosynthetic , may hold clues about the evolutionary process. However, there are only three published genomes within this order, and it is difficult to make broad inferences based on such little data. Here, I describe five species within the retrieved from publicly available databases and examine their photosynthetic gene content and the environments in which genomes and 16S rRNA gene sequences are found. The contain reduced photosystems and inhabit cold, wet-rock, and low-light environments. They are likely present in low abundances due to their low growth rate. Future searches for should target these environments, and samples should be deeply sequenced to capture the low-abundance taxa. Publicly available databases contain undescribed taxa within the . However, searching through all available data with current methods is computationally expensive. Therefore, new methods must be developed to search for these and other evolutionarily important taxa. Once identified, these novel photosynthetic will help illuminate the origin and evolution of oxygenic photosynthesis. Early branching photosynthetic such as the may provide clues into the evolutionary history of oxygenic photosynthesis, but there are few genomes or cultured taxa from this order. Five new metagenome-assembled genomes suggest that members of the all contain reduced photosystems and lack genes associated with thylakoids and circadian rhythms. Their distribution suggests that they may thrive in environments that are marginal for other species, including wet-rock and cold environments. These traits may aid in the discovery and cultivation of novel species in this clade.
Topics: Cyanobacteria; Databases, Nucleic Acid; Oxygen; Photosynthesis; Phylogeny; RNA, Ribosomal, 16S
PubMed: 34287010
DOI: 10.1128/mSphere.00061-21 -
The Journal of Biological Chemistry Oct 2020An intriguing molecular architecture called the "semi-crystalline photosystem II (PSII) array" has been observed in the thylakoid membranes in vascular plants. It is an...
An intriguing molecular architecture called the "semi-crystalline photosystem II (PSII) array" has been observed in the thylakoid membranes in vascular plants. It is an array of PSII-light-harvesting complex II (LHCII) supercomplexes that only appears in low light, but its functional role has not been clarified. Here, we identified PSII-LHCII supercomplexes in their monomeric and multimeric forms in low light-acclimated spinach leaves and prepared them using sucrose-density gradient ultracentrifugation in the presence of amphipol A8-35. When the leaves were acclimated to high light, only the monomeric forms were present, suggesting that the multimeric forms represent a structural adaptation to low light and that disaggregation of the PSII-LHCII supercomplex represents an adaptation to high light. Single-particle EM revealed that the multimeric PSII-LHCII supercomplexes are composed of two ("megacomplex") or three ("arraycomplex") units of PSII-LHCII supercomplexes, which likely constitute a fraction of the semi-crystalline PSII array. Further characterization with fluorescence analysis revealed that multimeric forms have a higher light-harvesting capability but a lower thermal dissipation capability than the monomeric form. These findings suggest that the configurational conversion of PSII-LHCII supercomplexes may serve as a structural basis for acclimation of plants to environmental light.
Topics: Acclimatization; Chlamydomonas reinhardtii; Light; Light-Harvesting Protein Complexes; Photosystem II Protein Complex; Plant Leaves; Protein Conformation; Protein Multimerization; Thylakoids
PubMed: 32561642
DOI: 10.1074/jbc.RA120.014198 -
Biochemical Society Transactions Dec 2020The emergence of the oxygen-evolving photosystem two complex over 2.6 billion years ago represented the 'big bang of evolution' on planet Earth. It allowed phototrophic... (Review)
Review
The emergence of the oxygen-evolving photosystem two complex over 2.6 billion years ago represented the 'big bang of evolution' on planet Earth. It allowed phototrophic organisms to use sun light as an energy source to extract electrons and protons from water, and concomitantly release oxygen. Oxygenic photosynthesis not only created an aerobic atmosphere but also removed CO2 to produce the organic molecules that make up the current global biomass and fossil fuel. In addition, it paved the way for animal life. Today extensive burning of fossil fuels is reversing the results of photosynthesis through billions of years, rapidly releasing CO2 back into the atmosphere and consequently increasing the temperature of the planet. There is an urgent need to develop new sustainable energy sources, but the choice is not obvious. My approach to this problem has been to unravel the blueprint of photosystem II (PSII) and to develop an 'Artificial Leaf' technology. A significant step with respect to that mission was achieved at Imperial College when we could conclude from X-ray diffraction of PSII crystals, that the water-splitting catalytic centre consists of a unique Mn3Ca2+O4 cubane structure with a fourth dangler Mn oxo-bonded to the cubane. Here I use this and more recent structures to discuss the mechanism of water splitting and O-O bond formation. Furthermore, I will address how this information can be used to design novel water-splitting catalysts and highlight recent progress in this direction. My conviction is 'if plants can do it, we can do it - after all it is all about chemistry'.
Topics: Animals; Biomass; Carbon Dioxide; Catalysis; Climate Change; Global Warming; Humans; Hydrogen; Oxidation-Reduction; Oxygen; Photosynthesis; Photosystem II Protein Complex; Plant Leaves; Plants; Solar Energy; Sunlight; Water
PubMed: 33242067
DOI: 10.1042/BST20200758 -
Plant Physiology May 2022Linear electron flow (LEF) and cyclic electron flow (CEF) compete for light-driven electrons transferred from the acceptor side of photosystem I (PSI). Under anoxic...
Linear electron flow (LEF) and cyclic electron flow (CEF) compete for light-driven electrons transferred from the acceptor side of photosystem I (PSI). Under anoxic conditions, such highly reducing electrons also could be used for hydrogen (H2) production via electron transfer between ferredoxin and hydrogenase in the green alga Chlamydomonas reinhardtii. Partitioning between LEF and CEF is regulated through PROTON-GRADIENT REGULATION5 (PGR5). There is evidence that partitioning of electrons also could be mediated via PSI remodeling processes. This plasticity is linked to the dynamics of PSI-associated light-harvesting proteins (LHCAs) LHCA2 and LHCA9. These two unique light-harvesting proteins are distinct from all other LHCAs because they are loosely bound at the PSAL pole. Here, we investigated photosynthetic electron transfer and H2 production in single, double, and triple mutants deficient in PGR5, LHCA2, and LHCA9. Our data indicate that lhca2 and lhca9 mutants are efficient in photosynthetic electron transfer, that LHCA2 impacts the pgr5 phenotype, and that pgr5/lhca2 is a potent H2 photo-producer. In addition, pgr5/lhca2 and pgr5/lhca9 mutants displayed substantially different H2 photo-production kinetics. This indicates that the absence of LHCA2 or LHCA9 impacts H2 photo-production independently, despite both being attached at the PSAL pole, pointing to distinct regulatory capacities.
Topics: Electron Transport; Electrons; Hydrogen; Photosynthesis; Photosystem I Protein Complex; Protons; Tumor Necrosis Factor Ligand Superfamily Member 14
PubMed: 35157085
DOI: 10.1093/plphys/kiac055 -
International Journal of Molecular... Feb 2023The present study shows the effect of salinity on the functions of thylakoid membranes from two hybrid lines of : x and x , grown in a Hoagland solution with two NaCl...
Impact of Salinity on the Energy Transfer between Pigment-Protein Complexes in Photosynthetic Apparatus, Functions of the Oxygen-Evolving Complex and Photochemical Activities of Photosystem II and Photosystem I in Two Lines.
The present study shows the effect of salinity on the functions of thylakoid membranes from two hybrid lines of : x and x , grown in a Hoagland solution with two NaCl concentrations (100 and 150 mM) and different exposure times (10 and 25 days). We observed inhibition of the photochemical activities of photosystem I (DCPIH → MV) and photosystem II (HO → BQ) only after the short treatment (10 days) with the higher NaCl concentration. Data also revealed alterations in the energy transfer between pigment-protein complexes (fluorescence emission ratios F/F and FF), the kinetic parameters of the oxygen-evolving reactions (initial S-S state distribution, misses (α), double hits (β) and blocked centers (S)). Moreover, the experimental results showed that after prolonged treatment with NaCl x adapted to the higher concentration of NaCl (150 mM), while this concentration is lethal for x . This study demonstrated the relationship between the salt-induced inhibition of the photochemistry of both photosystems and the salt-induced changes in the energy transfer between the pigment-protein complexes and the alterations in the Mn cluster of the oxygen-evolving complex under salt stress.
Topics: Photosystem II Protein Complex; Thylakoids; Photosystem I Protein Complex; Salinity; Sodium Chloride; Photosynthesis; Energy Transfer; Oxygen; Chlorophyll
PubMed: 36834517
DOI: 10.3390/ijms24043108 -
Nature May 2023Photosynthesis fuels life on Earth by storing solar energy in chemical form. Today's oxygen-rich atmosphere has resulted from the splitting of water at the protein-bound...
Photosynthesis fuels life on Earth by storing solar energy in chemical form. Today's oxygen-rich atmosphere has resulted from the splitting of water at the protein-bound manganese cluster of photosystem II during photosynthesis. Formation of molecular oxygen starts from a state with four accumulated electron holes, the S state-which was postulated half a century ago and remains largely uncharacterized. Here we resolve this key stage of photosynthetic O formation and its crucial mechanistic role. We tracked 230,000 excitation cycles of dark-adapted photosystems with microsecond infrared spectroscopy. Combining these results with computational chemistry reveals that a crucial proton vacancy is initally created through gated sidechain deprotonation. Subsequently, a reactive oxygen radical is formed in a single-electron, multi-proton transfer event. This is the slowest step in photosynthetic O formation, with a moderate energetic barrier and marked entropic slowdown. We identify the S state as the oxygen-radical state; its formation is followed by fast O-O bonding and O release. In conjunction with previous breakthroughs in experimental and computational investigations, a compelling atomistic picture of photosynthetic O formation emerges. Our results provide insights into a biological process that is likely to have occurred unchanged for the past three billion years, which we expect to support the knowledge-based design of artificial water-splitting systems.
Topics: Electrons; Oxidation-Reduction; Oxygen; Photosynthesis; Photosystem II Protein Complex; Protons; Water
PubMed: 37138082
DOI: 10.1038/s41586-023-06008-5 -
International Journal of Molecular... Mar 2024Photosystem I (PSI) is one of the two main pigment-protein complexes where the primary steps of oxygenic photosynthesis take place. This review describes low-temperature... (Review)
Review
Photosystem I (PSI) is one of the two main pigment-protein complexes where the primary steps of oxygenic photosynthesis take place. This review describes low-temperature frequency-domain experiments (absorption, emission, circular dichroism, resonant and non-resonant hole-burned spectra) and modeling efforts reported for PSI in recent years. In particular, we focus on the spectral hole-burning studies, which are not as common in photosynthesis research as the time-domain spectroscopies. Experimental and modeling data obtained for trimeric cyanobacterial Photosystem I (PSI), PSI mutants, and PSI-IsiA supercomplexes are analyzed to provide a more comprehensive understanding of their excitonic structure and excitation energy transfer (EET) processes. Detailed information on the excitonic structure of photosynthetic complexes is essential to determine the structure-function relationship. We will focus on the so-called "red antenna states" of cyanobacterial PSI, as these states play an important role in photochemical processes and EET pathways. The high-resolution data and modeling studies presented here provide additional information on the energetics of the lowest energy states and their chlorophyll (Chl) compositions, as well as the EET pathways and how they are altered by mutations. We present evidence that the low-energy traps observed in PSI are excitonically coupled states with significant charge-transfer (CT) character. The analysis presented for various optical spectra of PSI and PSI-IsiA supercomplexes allowed us to make inferences about EET from the IsiA ring to the PSI core and demonstrate that the number of entry points varies between sample preparations studied by different groups. In our most recent samples, there most likely are three entry points for EET from the IsiA ring per the PSI core monomer, with two of these entry points likely being located next to each other. Therefore, there are nine entry points from the IsiA ring to the PSI trimer. We anticipate that the data discussed below will stimulate further research in this area, providing even more insight into the structure-based models of these important cyanobacterial photosystems.
Topics: Photosystem I Protein Complex; Circular Dichroism; Energy Transfer; Chlorophyll; Cold Temperature
PubMed: 38612659
DOI: 10.3390/ijms25073850 -
Molecules (Basel, Switzerland) Oct 2021Single-walled carbon nanotubes (SWCNT) have recently been attracting the attention of plant biologists as a prospective tool for modulation of photosynthesis in higher...
Polymer-Modified Single-Walled Carbon Nanotubes Affect Photosystem II Photochemistry, Intersystem Electron Transport Carriers and Photosystem I End Acceptors in Pea Plants.
Single-walled carbon nanotubes (SWCNT) have recently been attracting the attention of plant biologists as a prospective tool for modulation of photosynthesis in higher plants. However, the exact mode of action of SWCNT on the photosynthetic electron transport chain remains unknown. In this work, we examined the effect of foliar application of polymer-grafted SWCNT on the donor side of photosystem II, the intersystem electron transfer chain and the acceptor side of photosystem I. Analysis of the induction curves of chlorophyll fluorescence via JIP test and construction of differential curves revealed that SWCNT concentrations up to 100 mg/L did not affect the photosynthetic electron transport chain. SWCNT concentration of 300 mg/L had no effect on the photosystem II donor side but provoked inactivation of photosystem II reaction centres and slowed down the reduction of the plastoquinone pool and the photosystem I end acceptors. Changes in the modulated reflection at 820 nm, too, indicated slower re-reduction of photosystem I reaction centres in SWCNT-treated leaves. We conclude that SWCNT are likely to be able to divert electrons from the photosynthetic electron transport chain at the level of photosystem I end acceptors and plastoquinone pool in vivo. Further research is needed to unequivocally prove if the observed effects are due to specific interaction between SWCNT and the photosynthetic apparatus.
Topics: Chlorophyll; Electron Transport; Fluorescence; Nanotubes, Carbon; Pisum sativum; Photosystem I Protein Complex; Photosystem II Protein Complex; Plant Leaves; Polymers
PubMed: 34641502
DOI: 10.3390/molecules26195958 -
Frontiers in Plant Science 2022
PubMed: 35498689
DOI: 10.3389/fpls.2022.871623