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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 -
Journal of Photochemistry and... Aug 2014The reaction center-binding D1 protein of Photosystem II is damaged by excessive light, which leads to photoinhibition of Photosystem II. The damaged D1 protein is... (Review)
Review
The reaction center-binding D1 protein of Photosystem II is damaged by excessive light, which leads to photoinhibition of Photosystem II. The damaged D1 protein is removed immediately by specific proteases, and a metalloprotease FtsH located in the thylakoid membranes is involved in the proteolytic process. According to recent studies on the distribution and organization of the protein complexes/supercomplexes in the thylakoid membranes, the grana of higher plant chloroplasts are crowded with Photosystem II complexes and light-harvesting complexes. For the repair of the photodamaged D1 protein, the majority of the active hexameric FtsH proteases should be localized in close proximity to the Photosystem II complexes. The unstacking of the grana may increase the area of the grana margin and facilitate easier access of the FtsH proteases to the damaged D1 protein. These results suggest that the structural changes of the thylakoid membranes by light stress increase the mobility of the membrane proteins and support the quality control of Photosystem II.
Topics: Cyanobacteria; Metalloendopeptidases; Photosystem II Protein Complex; Spinacia oleracea; Stress, Physiological; Thylakoids
PubMed: 24725639
DOI: 10.1016/j.jphotobiol.2014.02.012 -
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 -
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 -
Postepy Biochemii Jun 2020The light phase of photosynthesis is a key energy process in higher plants. Its purpose is to convert light energy into chemical one stored in ATP and NADPH molecules,... (Review)
Review
The light phase of photosynthesis is a key energy process in higher plants. Its purpose is to convert light energy into chemical one stored in ATP and NADPH molecules, which are then used to assimilate CO2 and in numerous metabolic processes. Maintaining optimal photosynthesis performance requires strict regulation of thylakoid membranes organization and rapid response to changing environmental conditions. The main factor affecting photosynthesis is light, which, if applied in excessive amounts, leads to a slowdown in the process. Therefore, plants have developed many protective mechanisms regulating the light reactions of photosynthesis and operating at the level of light energy absorption, electron transport, and the distribution and use of reducing power. These include, among others: (i) non-photochemical energy quenching regulating the amount of excitation energy delivered to the photosystems; (ii) ‘state transition’ process redistributing excitation energy between photosystems; (iii) redundant electron transport pathways responsible for maintaining redox balance in chloroplasts. All these mechanisms, in combination with antioxidant systems, are designed to maintain the function of the photosynthetic apparatus in adverse growth conditions.
Topics: Chloroplasts; Electron Transport; Oxidation-Reduction; Photosynthesis; Plants
PubMed: 32700507
DOI: 10.18388/pb.2020_325 -
Biochimica Et Biophysica Acta.... Apr 2023Knowledge about the exact abundance and ratio of photosynthetic protein complexes in thylakoid membranes is central to understanding structure-function relationships in...
Knowledge about the exact abundance and ratio of photosynthetic protein complexes in thylakoid membranes is central to understanding structure-function relationships in energy conversion. Recent modeling approaches for studying light harvesting and electron transport reactions rely on quantitative information on the constituent complexes in thylakoid membranes. Over the last decades several quantitative methods have been established and refined, enabling precise stoichiometric information on the five main energy-converting building blocks in the thylakoid membrane: Light-harvesting complex II (LHCII), Photosystem II (PSII), Photosystem I (PSI), cytochrome bf complex (cyt bf complex), and ATPase. This paper summarizes a few quantitative spectroscopic and biochemical methods that are currently available for quantification of plant thylakoid protein complexes. Two new methods are presented for quantification of LHCII and the cyt bf complex, which agree well with established methods. In addition, recent improvements in mass spectrometry (MS) allow deeper compositional information on thylakoid membranes. The comparison between mass spectrometric and more classical protein quantification methods shows similar quantities of complexes, confirming the potential of thylakoid protein complex quantification by MS. The quantitative information on PSII, PSI, and LHCII reveal that about one third of LHCII must be associated with PSI for a balanced light energy absorption by the two photosystems.
Topics: Thylakoids; Cytochrome b6f Complex; Cytochromes b; Light-Harvesting Protein Complexes; Photosystem I Protein Complex; Plant Proteins
PubMed: 36442511
DOI: 10.1016/j.bbabio.2022.148945