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Biochimica Et Biophysica Acta.... Apr 2020Photosynthesis is a fundamental biological process involving the conversion of solar energy into chemical energy. The initial photochemical and photophysical events of... (Comparative Study)
Comparative Study Review
Photosynthesis is a fundamental biological process involving the conversion of solar energy into chemical energy. The initial photochemical and photophysical events of photosynthesis are mediated by photosystem II (PSII) and photosystem I (PSI). Both PSII and PSI are multi-subunit supramolecular machineries composed of a core complex and a peripheral antenna system. The antenna system serves to capture light energy and transfer it to the core efficiently. Both PSII and PSI in the green lineage (plants and green algae) and PSI in red algae have an antenna system comprising a series of chlorophyll- and carotenoid-binding membrane proteins belonging to the light-harvesting complex (LHC) superfamily, including LHCII and LHCI. However, the antenna size and subunit composition vary considerably in the two photosystems from diverse organisms. On the basis of the plant and algal LHCII and LHCI structures that have been solved by X-ray crystallography and single-particle cryo-electron microscopy we review the detailed structural features and characteristic pigment properties of these LHCs in PSII and PSI. This article is part of a Special Issue entitled Light harvesting, edited by Dr. Roberta Croce.
Topics: Amino Acid Sequence; Apoproteins; Chlamydomonas reinhardtii; Chlorophyll; Light-Harvesting Protein Complexes; Models, Molecular; Photosystem I Protein Complex; Photosystem II Protein Complex; Protein Subunits; Rhodophyta
PubMed: 31229568
DOI: 10.1016/j.bbabio.2019.06.010 -
Scientific Reports Jun 2022Plant growth under spectrally-enriched low light conditions leads to adjustment in the relative abundance of the two photosystems in an acclimatory response known as...
Plant growth under spectrally-enriched low light conditions leads to adjustment in the relative abundance of the two photosystems in an acclimatory response known as photosystem stoichiometry adjustment. Adjustment of photosystem stoichiometry improves the quantum efficiency of photosynthesis but how this process perceives light quality changes and how photosystem amount is regulated remain largely unknown. By using a label-free quantitative mass spectrometry approach in Arabidopsis here we show that photosystem stoichiometry adjustment is primarily driven by the regulation of photosystem I content and that this forms the major thylakoid proteomic response under light quality. Using light and redox signaling mutants, we further show that the light quality-responsive accumulation of photosystem I gene transcripts and proteins requires phytochrome B photoreceptor but not plastoquinone redox signaling as previously suggested. In far-red light, the increased acceptor side limitation might deplete active photosystem I pool, further contributing to the adjustment of photosystem stoichiometry.
Topics: Arabidopsis; Arabidopsis Proteins; Light; Oxidation-Reduction; Photosynthesis; Photosystem I Protein Complex; Photosystem II Protein Complex; Proteomics; Thylakoids
PubMed: 35768472
DOI: 10.1038/s41598-022-14967-4 -
Nature Mar 2023Photosystems II and I (PSII, PSI) are the reaction centre-containing complexes driving the light reactions of photosynthesis; PSII performs light-driven water oxidation...
Photosystems II and I (PSII, PSI) are the reaction centre-containing complexes driving the light reactions of photosynthesis; PSII performs light-driven water oxidation and PSI further photo-energizes harvested electrons. The impressive efficiencies of the photosystems have motivated extensive biological, artificial and biohybrid approaches to 're-wire' photosynthesis for higher biomass-conversion efficiencies and new reaction pathways, such as H evolution or CO fixation. Previous approaches focused on charge extraction at terminal electron acceptors of the photosystems. Electron extraction at earlier steps, perhaps immediately from photoexcited reaction centres, would enable greater thermodynamic gains; however, this was believed impossible with reaction centres buried at least 4 nm within the photosystems. Here, we demonstrate, using in vivo ultrafast transient absorption (TA) spectroscopy, extraction of electrons directly from photoexcited PSI and PSII at early points (several picoseconds post-photo-excitation) with live cyanobacterial cells or isolated photosystems, and exogenous electron mediators such as 2,6-dichloro-1,4-benzoquinone (DCBQ) and methyl viologen. We postulate that these mediators oxidize peripheral chlorophyll pigments participating in highly delocalized charge-transfer states after initial photo-excitation. Our results challenge previous models that the photoexcited reaction centres are insulated within the photosystem protein scaffold, opening new avenues to study and re-wire photosynthesis for biotechnologies and semi-artificial photosynthesis.
Topics: Chlorophyll; Oxidation-Reduction; Photosynthesis; Photosystem I Protein Complex; Photosystem II Protein Complex; Time Factors; Carbon Cycle; Carbon Dioxide; Hydrogen; Cyanobacteria; Electrons; Thermodynamics
PubMed: 36949188
DOI: 10.1038/s41586-023-05763-9 -
Photosynthesis Research May 2022These special issues of photosynthesis research present papers documenting progress in revealing the many aspects of photosystem 2, a unique, one-of-a-kind complex... (Review)
Review
These special issues of photosynthesis research present papers documenting progress in revealing the many aspects of photosystem 2, a unique, one-of-a-kind complex system that can reduce a plastoquinone to a plastoquinol on every second flash of light and oxidize 2 HO to an O on every fourth flash. This overview is a brief personal assessment of the progress observed by the author over a four-decade research career, including a discussion of some remaining unsolved issues. It will come as no surprise to readers that there are remaining questions given the complexity of PS2, and the efforts that have been needed so far to uncover its secrets. In fact, most readers will have their own lists of outstanding questions.
Topics: Oxidation-Reduction; Oxygen; Photosynthesis; Photosystem II Protein Complex; Plastoquinone; Thylakoids
PubMed: 35294671
DOI: 10.1007/s11120-022-00910-1 -
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 -
Trends in Genetics : TIG Mar 2021Cyanobacterial genomes encode several isoforms of the D1 (PsbA) subunit of Photosystem II (PSII). The distinct regulation of each isoform ensures adaptation under... (Review)
Review
Cyanobacterial genomes encode several isoforms of the D1 (PsbA) subunit of Photosystem II (PSII). The distinct regulation of each isoform ensures adaptation under changing environmental conditions. Uncovering the missing elements of signal transduction pathways and psbA gene expression could open new avenues in engineering programs of cyanobacterial strains.
Topics: Amino Acid Sequence; Cyanobacteria; Gene Expression Regulation, Bacterial; Genome, Bacterial; Photosystem II Protein Complex; Protein Isoforms; Signal Transduction
PubMed: 32977998
DOI: 10.1016/j.tig.2020.08.018 -
The New Phytologist May 2022Paulinella represents the only known case of an independent primary plastid endosymbiosis, outside Archaeplastida, that occurred c. 120 (million years ago) Ma. These...
Paulinella represents the only known case of an independent primary plastid endosymbiosis, outside Archaeplastida, that occurred c. 120 (million years ago) Ma. These photoautotrophs grow very slowly in replete culture medium with a doubling time of 6-7 d at optimal low light, and are highly sensitive to photodamage under moderate light levels. We used genomic and biophysical methods to investigate the extreme slow growth rate and light sensitivity of Paulinella, which are key to photosymbiont integration. All photosystem II (PSII) genes except psb28-2 and all cytochrome b f complex genes except petM and petL are present in Paulinella micropora KR01 (hereafter, KR01). Biophysical measurements of the water oxidation complex, variable chlorophyll fluorescence, and photosynthesis-irradiance curves show no obvious evidence of PSII impairment. Analysis of photoacclimation under high-light suggests that although KR01 can perform charge separation, it lacks photoprotection mechanisms present in cyanobacteria. We hypothesize that Paulinella species are restricted to low light environments because they are deficient in mitigating the formation of reactive oxygen species formed within the photosystems under peak solar intensities. The finding that many photoprotection genes have been lost or transferred to the host-genome during endosymbiont genome reduction, and may lack light-regulation, is consistent with this hypothesis.
Topics: Amoeba; Chromatophores; Light; Photosynthesis; Photosystem II Protein Complex; Phylogeny
PubMed: 35211975
DOI: 10.1111/nph.18052 -
Nature Communications Mar 2022Cyclophilins, or immunophilins, are proteins found in many organisms including bacteria, plants and humans. Most of them display peptidyl-prolyl cis-trans isomerase...
Cyclophilins, or immunophilins, are proteins found in many organisms including bacteria, plants and humans. Most of them display peptidyl-prolyl cis-trans isomerase activity, and play roles as chaperones or in signal transduction. Here, we show that cyclophilin anaCyp40 from the cyanobacterium Anabaena sp. PCC 7120 is enzymatically active, and seems to be involved in general stress responses and in assembly of photosynthetic complexes. The protein is associated with the thylakoid membrane and interacts with phycobilisome and photosystem components. Knockdown of anacyp40 leads to growth defects under high-salt and high-light conditions, and reduced energy transfer from phycobilisomes to photosystems. Elucidation of the anaCyp40 crystal structure at 1.2-Å resolution reveals an N-terminal helical domain with similarity to PsbQ components of plant photosystem II, and a C-terminal cyclophilin domain with a substrate-binding site. The anaCyp40 structure is distinct from that of other multi-domain cyclophilins (such as Arabidopsis thaliana Cyp38), and presents features that are absent in single-domain cyclophilins.
Topics: Cyanobacteria; Cyclophilins; Humans; Photosystem II Protein Complex; Phycobilisomes; Thylakoids
PubMed: 35354803
DOI: 10.1038/s41467-022-29211-w -
International Journal of Molecular... Jan 2023Eukaryotic photosynthesis originated in the course of evolution as a result of the uptake of some unstored cyanobacterium and its transformation to chloroplasts by an... (Review)
Review
Eukaryotic photosynthesis originated in the course of evolution as a result of the uptake of some unstored cyanobacterium and its transformation to chloroplasts by an ancestral heterotrophic eukaryotic cell. The pigment apparatus of Archaeplastida and other algal phyla that emerged later turned out to be arranged in the same way. Pigment-protein complexes of photosystem I (PS I) and photosystem II (PS II) are characterized by uniform structures, while the light-harvesting antennae have undergone a series of changes. The phycobilisome (PBS) antenna present in cyanobacteria was replaced by Chl - or Chl -containing pigment-protein complexes in most groups of photosynthetics. In the form of PBS or phycobiliprotein aggregates, it was inherited by members of Cyanophyta, Cryptophyta, red algae, and photosynthetic amoebae. Supramolecular organization and architectural modifications of phycobiliprotein antennae in various algal phyla in line with the endosymbiotic theory of chloroplast origin are the subject of this review.
Topics: Phycobilisomes; Phycobiliproteins; Symbiosis; Oxygen; Photosynthesis; Cyanobacteria; Photosystem II Protein Complex; Photosystem I Protein Complex; Chlorophyll
PubMed: 36768613
DOI: 10.3390/ijms24032290 -
Plant & Cell Physiology Oct 2021Photosynthesis is the process conducted by plants and algae to capture photons and store their energy in chemical forms. The light-harvesting, excitation transfer,... (Review)
Review
Photosynthesis is the process conducted by plants and algae to capture photons and store their energy in chemical forms. The light-harvesting, excitation transfer, charge separation and electron transfer in photosystem II (PSII) are the critical initial reactions of photosynthesis and thereby largely determine its overall efficiency. In this review, we outline the rapidly accumulating knowledge about the architectures and assemblies of plant and green algal PSII-light harvesting complex II (LHCII) supercomplexes, with a particular focus on new insights provided by the recent high-resolution cryo-electron microscopy map of the supercomplexes from a green alga Chlamydomonas reinhardtii. We make pair-wise comparative analyses between the supercomplexes from plants and green algae to gain insights about the evolution of the PSII-LHCII supercomplexes involving the peripheral small PSII subunits that might have been acquired during the evolution and about the energy transfer pathways that define their light-harvesting and photoprotective properties.
Topics: Chlorophyta; Energy Transfer; Evolution, Molecular; Light-Harvesting Protein Complexes; Photosystem II Protein Complex; Plants; Protein Structure, Tertiary
PubMed: 34038564
DOI: 10.1093/pcp/pcab072