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Plants (Basel, Switzerland) Mar 2021A significant increase in atmospheric CO concentration and associated climate aridization and soil salinity are factors affecting the growth, development, productivity,...
A significant increase in atmospheric CO concentration and associated climate aridization and soil salinity are factors affecting the growth, development, productivity, and stress responses of plants. In this study, the effect of ambient (400 ppm) and elevated (800 ppm) CO concentrations were evaluated on the C xero-halophyte treated with moderate salinity (200 mM NaCl) and polyethylene glycol (PEG)-induced osmotic stress. Our results indicated that plants grown at elevated CO concentration had different responses to osmotic stress and salinity. The synergistic effect of elevated CO and osmotic stress increased proline accumulation, but elevated CO did not mitigate the negative effects of osmotic stress on dark respiration intensity and photosystem II (PSII) efficiency. This indicates a stressful state, which is accompanied by a decrease in the efficiency of light reactions of photosynthesis and significant dissipative respiratory losses, thereby resulting in growth inhibition. Plants grown at elevated CO concentration and salinity showed high Na and proline contents, high water-use efficiency and time required to reach the maximum P700 oxidation level (PSI), and low dark respiration. Maintaining stable water balance, the efficient functioning of cyclic transport of PSI, and the reduction of dissipation costs contributed to an increase in dry shoot biomass (2-fold, compared with salinity at 400 ppm CO). The obtained experimental data and PCA showed that elevated CO concentration improved the physiological parameters of under salinity.
PubMed: 33807685
DOI: 10.3390/plants10030491 -
Nature Communications Dec 2023Phycobilisomes (PBS) are antenna megacomplexes that transfer energy to photosystems II and I in thylakoids. PBS likely evolved from a basic, inefficient form into the...
Phycobilisomes (PBS) are antenna megacomplexes that transfer energy to photosystems II and I in thylakoids. PBS likely evolved from a basic, inefficient form into the predominant hemidiscoidal shape with radiating peripheral rods. However, it has been challenging to test this hypothesis because ancestral species are generally inaccessible. Here we use spectroscopy and cryo-electron microscopy to reveal a structure of a "paddle-shaped" PBS from a thylakoid-free cyanobacterium that likely retains ancestral traits. This PBS lacks rods and specialized ApcD and ApcF subunits, indicating relict characteristics. Other features include linkers connecting two chains of five phycocyanin hexamers (CpcN) and two core subdomains (ApcH), resulting in a paddle-shaped configuration. Energy transfer calculations demonstrate that chains are less efficient than rods. These features may nevertheless have increased light absorption by elongating PBS before multilayered thylakoids with hemidiscoidal PBS evolved. Our results provide insights into the evolution and diversification of light-harvesting strategies before the origin of thylakoids.
Topics: Thylakoids; Phycobilisomes; Cryoelectron Microscopy; Photosystem I Protein Complex; Bacterial Proteins; Cyanobacteria
PubMed: 38049400
DOI: 10.1038/s41467-023-43646-9 -
Biphasic effects of typical chlorinated organophosphorus flame retardants on Microcystis aeruginosa.Ecotoxicology and Environmental Safety Aug 2022The potential accumulation of chlorinated organophosphorus flame retardants (Cl-OPFRs) in aquatic environments sparked interest in studying the effects of Cl-OPFRs on...
The potential accumulation of chlorinated organophosphorus flame retardants (Cl-OPFRs) in aquatic environments sparked interest in studying the effects of Cl-OPFRs on cyanobacterial blooms. In this work, two common Cl-OPFRs, tris(1,3-dichloro-2-propyl) phosphate (TDCPP) and tris(2-chloroethyl) phosphate (TCEP), induced dose-dependent biphasic effect on bloom-forming M. aeruginosa. The hormetic response to low-dose Cl-OPFRs was associated with the upregulation of the type I NADH dehydrogenase (NDH-1) complex and its mediated cyclic electron transfer (CET) pathway, as reflected by a transient post-illumination increase in chlorophyll fluorescence, the dark reduction of P700 and the change of NDH-1-related gene expression. The increased CET activity and carotenoid content jointly reduced the intracellular ROS production, facilitating cyanobacterial growth. Conversely, a higher concentration of both Cl-OPFRs induced severe inhibition of growth and photosynthetic oxygen-evolving activity through an imbalance between PSII and PSI. Toxic-dose Cl-OPFRs inhibited state transition and fixed cells into the State I with a higher PSII/PSI ratio, as indicated by chlorophyll fluorescence induction, 77 K fluorescence emission spectra and photosystem stoichiometry. The elevated PSII/PSI ratio created an imbalance between the two photosystems and eventually lead to ROS overproduction, which generate adverse effects on cell growth. This work provides important insights into the hormetic mechanism of Cl-OPFRs on Microcystis aeruginosa and their potential roles in harmful cyanobacteria blooms.
Topics: Chlorophyll; Flame Retardants; Microcystis; Organophosphates; Organophosphorus Compounds; Phosphates; Reactive Oxygen Species
PubMed: 36068742
DOI: 10.1016/j.ecoenv.2022.113813 -
Frontiers in Plant Science 2020Recruitment of HO as the final donor of electrons for light-governed reactions in photosynthesis has been an utmost breakthrough, bursting the evolution of life and... (Review)
Review
Recruitment of HO as the final donor of electrons for light-governed reactions in photosynthesis has been an utmost breakthrough, bursting the evolution of life and leading to the accumulation of O molecules in the atmosphere. O molecule has a great potential to accept electrons from the components of the photosynthetic electron transfer chain (PETC) (so-called the Mehler reaction). Here we overview the Mehler reaction mechanisms, specifying the changes in the structure of the PETC of oxygenic phototrophs that probably had occurred as the result of evolutionary pressure to minimize the electron flow to O. These changes are warranted by the fact that the efficient electron flow to O would decrease the quantum yield of photosynthesis. Moreover, the reduction of O leads to the formation of reactive oxygen species (ROS), namely, the superoxide anion radical and hydrogen peroxide, which cause oxidative stress to plant cells if they are accumulated at a significant amount. From another side, hydrogen peroxide acts as a signaling molecule. We particularly zoom in into the role of photosystem I (PSI) and the plastoquinone (PQ) pool in the Mehler reaction.
PubMed: 32231675
DOI: 10.3389/fpls.2020.00211 -
Structure of Photosystem I Supercomplex Isolated from a Cytochrome b6f Temperature-Sensitive Mutant.Biomolecules Mar 2023The unicellular green alga, , has been widely used as a model system to study photosynthesis. Its possibility to generate and analyze specific mutants has made it an...
The unicellular green alga, , has been widely used as a model system to study photosynthesis. Its possibility to generate and analyze specific mutants has made it an excellent tool for mechanistic and biogenesis studies. Using negative selection of ultraviolet (UV) irradiation-mutated cells, we isolated a mutant (TSP9) with a single amino acid mutation in the Rieske protein of the cytochrome b6f complex. The W143R mutation in the petC gene resulted in total loss of cytochrome b6f complex function at the non-permissive temperature of 37 °C and recovery at the permissive temperature of 25 °C. We then isolated photosystem I (PSI) and photosystem II (PSII) supercomplexes from cells grown at the non-permissive temperature and determined the PSI structure with high-resolution cryogenic electron microscopy. There were several structural alterations compared with the structures obtained from wild-type cells. Our structural data suggest that the mutant responded by excluding the Lhca2, Lhca9, PsaL, and PsaH subunits. This structural alteration prevents state two transition, where LHCII migrates from PSII to bind to the PSI complex. We propose this as a possible response mechanism triggered by the TSP9 phenotype at the non-permissive temperature.
Topics: Photosystem I Protein Complex; Chlamydomonas reinhardtii; Cytochrome b6f Complex; Temperature; Light-Harvesting Protein Complexes; Photosystem II Protein Complex
PubMed: 36979472
DOI: 10.3390/biom13030537 -
Nature Communications Mar 2022Photosystem I (PSI) is one of the two photosystems functioning in light-energy harvesting, transfer, and electron transfer in photosynthesis. However, the...
Photosystem I (PSI) is one of the two photosystems functioning in light-energy harvesting, transfer, and electron transfer in photosynthesis. However, the oligomerization state of PSI is variable among photosynthetic organisms. We present a 3.8-Å resolution cryo-electron microscopic structure of tetrameric PSI isolated from the glaucophyte alga Cyanophora paradoxa, which reveals differences with PSI from other organisms in subunit composition and organization. The PSI tetramer is organized in a dimer of dimers with a C2 symmetry. Unlike cyanobacterial PSI tetramers, two of the four monomers are rotated around 90°, resulting in a completely different pattern of monomer-monomer interactions. Excitation-energy transfer among chlorophylls differs significantly between Cyanophora and cyanobacterial PSI tetramers. These structural and spectroscopic features reveal characteristic interactions and excitation-energy transfer in the Cyanophora PSI tetramer, suggesting that the Cyanophora PSI could represent a turning point in the evolution of PSI from prokaryotes to eukaryotes.
Topics: Chlorophyll; Cyanobacteria; Cyanophora; Energy Transfer; Photosystem I Protein Complex
PubMed: 35354806
DOI: 10.1038/s41467-022-29303-7 -
Life (Basel, Switzerland) Feb 2015Marine Synechococcus and Prochlorococcus are picocyanobacteria predominating in subtropical, oligotrophic marine environments, a niche predicted to expand with climate...
Marine Synechococcus and Prochlorococcus are picocyanobacteria predominating in subtropical, oligotrophic marine environments, a niche predicted to expand with climate change. When grown under common low light conditions Synechococcus WH 8102 and Prochlorococcus MED 4 show similar Cytochrome b6f and Photosystem I contents normalized to Photosystem II content, while Prochlorococcus MIT 9313 has twice the Cytochrome b6f content and four times the Photosystem I content of the other strains. Interestingly, the Prochlorococcus strains contain only one third to one half of the RUBISCO catalytic subunits compared to the marine Synechococcus strain. The maximum Photosystem II electron transport rates were similar for the two Prochlorococcus strains but higher for the marine Synechococcus strain. Photosystem II electron transport capacity is highly correlated to the molar ratio of RUBISCO active sites to Photosystem II but not to the ratio of cytochrome b6f to Photosystem II, nor to the ratio of Photosystem I: Photosystem II. Thus, the catalytic capacity for the rate-limiting step of carbon fixation, the ultimate electron sink, appears to limit electron transport rates. The high abundance of Cytochrome b6f and Photosystem I in MIT 9313, combined with the slower flow of electrons away from Photosystem II and the relatively low level of RUBISCO, are consistent with cyclic electron flow around Photosystem I in this strain.
PubMed: 25658887
DOI: 10.3390/life5010403 -
Biophysical Reviews Aug 2022Secondary metabolites of bacteria are regulatory molecules that act as "info-chemicals" that control some metabolic processes in the cells of microorganisms. These... (Review)
Review
Secondary metabolites of bacteria are regulatory molecules that act as "info-chemicals" that control some metabolic processes in the cells of microorganisms. These molecules provide the function of bacteria communication in microbial communities. As primary producers of organic matter in the biosphere, microalgae play a central ecological role in various ecosystems. Photosynthesis is a central process in microalgae cells, and it is exposed to various biotic and abiotic factors. Various secondary metabolites of bacteria confer a noticeable regulatory effect on photosynthesis in microalgae cells. The main purpose of this review is to highlight recent experimental results that demonstrate the impact of several types of common bacterial metabolites (volatile organic compounds, non-protein amino acids, and peptides) on photosynthetic activity in cells of microalgae. The use of these molecules as herbicides can be of great importance both for practical applications and for basic research.
PubMed: 36124259
DOI: 10.1007/s12551-022-00981-3 -
International Journal of Molecular... May 2024Photosynthesis, as the primary source of energy for all life forms, plays a crucial role in maintaining the global balance of energy, entropy, and enthalpy in living... (Review)
Review
Photosynthesis, as the primary source of energy for all life forms, plays a crucial role in maintaining the global balance of energy, entropy, and enthalpy in living organisms. Among its various building blocks, photosystem I (PSI) is responsible for light-driven electron transfer, crucial for generating cellular reducing power. PSI acts as a light-driven plastocyanin-ferredoxin oxidoreductase and is situated in the thylakoid membranes of cyanobacteria and the chloroplasts of eukaryotic photosynthetic organisms. Comprehending the structure and function of the photosynthetic machinery is essential for understanding its mode of action. New insights are offered into the structure and function of PSI and its associated light-harvesting proteins, with a specific focus on the remarkable structural conservation of the core complex and high plasticity of the peripheral light-harvesting complexes.
Topics: Photosystem I Protein Complex; Photosynthesis; Light-Harvesting Protein Complexes; Cyanobacteria; Models, Molecular; Electron Transport
PubMed: 38791114
DOI: 10.3390/ijms25105073 -
Frontiers in Plant Science 2022Iron is a cofactor of photosystems and electron carriers in the photosynthetic electron transport chain. Low concentrations of dissolved iron are, therefore, the...
Iron is a cofactor of photosystems and electron carriers in the photosynthetic electron transport chain. Low concentrations of dissolved iron are, therefore, the predominant factor that limits the growth of phototrophs in large parts of the open sea like the Southern Ocean and the North Pacific, resulting in "high nutrient-low chlorophyll" (HNLC) areas. Diatoms are among the most abundant microalgae in HNLC zones. Besides efficient iron uptake mechanisms, efficient photoprotection might be one of the key traits enabling them to outcompete other algae in HNLC regions. In diatoms, Lhcx proteins play a crucial role in one of the main photoprotective mechanisms, the energy-dependent fluorescence quenching (qE). The expression of Lhcx proteins is strongly influenced by various environmental triggers. We show that Lhcx2 responds specifically and in a very sensitive manner to iron limitation in the diatom on the same timescale as the known iron-regulated genes and By comparing Lhcx2 knockout lines with wild type cells, we reveal that a strongly increased qE under iron limitation is based on the upregulation of Lhcx2. Other observed iron acclimation phenotypes in include a massively reduced chlorophyll content/cell, a changed ratio of light harvesting and photoprotective pigments per chlorophyll , a decreased amount of photosystem II and photosystem I cores, an increased functional photosystem II absorption cross section, and decoupled antenna complexes. HO formation at photosystem I induced by high light is lowered in iron-limited cells, while the amount of total reactive oxygen species is rather increased. Our data indicate a possible reduction in singlet oxygen by Lhcx2-based qE, while the other iron acclimation phenotype parameters monitored are not affected by the amount of Lhcx2 and qE.
PubMed: 35371185
DOI: 10.3389/fpls.2022.841058