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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 -
International Journal of Molecular... Jul 2022The light-sensitive (LS) albino tea plant grows albinic shoots lacking chlorophylls (Chls) under high-light (HL) conditions, and the albinic shoots re-green under low...
The light-sensitive (LS) albino tea plant grows albinic shoots lacking chlorophylls (Chls) under high-light (HL) conditions, and the albinic shoots re-green under low light (LL) conditions. The albinic shoots contain a high level of amino acids and are preferential materials for processing quality green tea. The young plants of the albino tea cultivars are difficult to be cultivated owing to lacking Chls. The mechanisms of the tea leaf bleaching and re-greening are unknown. We detected the activity and composition of photosystem II (PSII) subunits in LS albino tea cultivar "Huangjinya" (HJY), with a normal green-leaf cultivar "Jinxuan" (JX) as control so as to find the relationship of PSII impairment to the albino phenotype in tea. The PSII of HJY is more vulnerable to HL-stress than JX. HL-induced degradation of PSII subunits CP43, CP47, PsbP, PsbR. and light-harvest chlorophyll-protein complexes led to the exposure and degradation of D1 and D2, in which partial fragments of the degraded subunits were crosslinked to form larger aggregates. Two copies of subunits PsbO, psbN, and Lhcb1 were expressed in response to HL stress. The cDNA sequencing of CP43 shows that there is no difference in sequences of PsbC cDNA and putative amino acids of CP43 between HJY and JX. The de novo synthesis and/or repair of PSII subunits is considered to be involved in the impairment of PSII complexes, and the latter played a predominant role in the albino phenotype in the LS albino tea plant.
Topics: Amino Acids; Camellia sinensis; Chlorophyll; DNA, Complementary; Photosystem II Protein Complex
PubMed: 35955658
DOI: 10.3390/ijms23158522 -
Biochimica Et Biophysica Acta.... Aug 2023Light induced photosystem (PS)II photoinhibition inactivates and irreversibly damages the reaction center protein(s) but the light harvesting complexes continue the...
Light induced photosystem (PS)II photoinhibition inactivates and irreversibly damages the reaction center protein(s) but the light harvesting complexes continue the collection of light energy. Here we addressed the consequences of such a situation on thylakoid light harvesting and electron transfer reactions. For this purpose, Arabidopsis thaliana leaves were subjected to investigation of the function and regulation of the photosynthetic machinery after a distinct portion of PSII centers had experienced photoinhibition in the presence and absence of Lincomycin (Lin), a commonly used agent to block the repair of damaged PSII centers. In the absence of Lin, photoinhibition increased the relative excitation of PSII and decreased NPQ, together enhancing the electron transfer from still functional PSII centers to PSI. In contrast, in the presence of Lin, PSII photoinhibition increased the relative excitation of PSI and led to strong oxidation of the electron transfer chain. We hypothesize that plants are able to minimize the detrimental effects of high-light illumination on PSII by modulating the energy and electron transfer, but lose such a capability if the repair cycle is arrested. It is further hypothesized that dynamic regulation of the LHCII system has a pivotal role in the control of excitation energy transfer upon PSII damage and repair cycle to maintain the photosynthesis safe and efficient.
Topics: Photosystem II Protein Complex; Thylakoids; Photosynthesis; Electron Transport; Arabidopsis
PubMed: 37100340
DOI: 10.1016/j.bbabio.2023.148978 -
Plant Physiology Aug 2020Light is a key environmental cue regulating photomorphogenesis and photosynthesis in plants. However, the molecular mechanisms underlying the interaction between light...
Light is a key environmental cue regulating photomorphogenesis and photosynthesis in plants. However, the molecular mechanisms underlying the interaction between light signaling pathways and photosystem function are unknown. Here, we show that various monochromatic wavelengths of light cooperate to regulate PSII function in Arabidopsis (). The photoreceptors cryptochromes and phytochromes modulate the expression of HIGH CHLOROPHYLL FLUORESCENCE173 (HCF173), which is required for PSII biogenesis by regulating PSII core protein D1 synthesis mediated by the transcription factor ELONGATED HYPOCOTYL5 (HY5). HY5 directly binds to the ACGT-containing element ACE motif and cis-element present in the promoter and regulates its activity. PSII activity was decreased significantly in mutants under various monochromatic wavelengths of light. Interestingly, we demonstrate that HY5 also directly regulates the expression of the genes associated with PSII assembly and repair, including , , , etc., which is required for the functional maintenance of PSII under photodamaging conditions. Moreover, deficiency of broadly decreases the accumulation of other photosystem proteins besides PSII proteins. Thus, our study reveals an important role of light signaling in both biogenesis and functional regulation of the photosystem and provides insight into the link between light signaling and photosynthesis in land plants.
Topics: Arabidopsis; Arabidopsis Proteins; Gene Expression Regulation, Plant; Light Signal Transduction; Photosynthesis; Photosystem II Protein Complex; Protein Binding; Transcription Factors
PubMed: 32439719
DOI: 10.1104/pp.20.00200 -
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 -
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 -
The Journal of General and Applied... Feb 2024Although n-butanol (BuOH) is an ideal fuel because of its superior physical properties, it has toxicity to microbes. Previously, a Synechococcus elongatus PCC 7942...
Although n-butanol (BuOH) is an ideal fuel because of its superior physical properties, it has toxicity to microbes. Previously, a Synechococcus elongatus PCC 7942 derivative strain that produces BuOH from CO was developed by introducing six heterologous genes (BUOH-SE strain). To identify the bottleneck in BuOH production, the effects of BuOH production and its toxicity on central metabolism and the photosystem were investigated. Parental (WT) and BUOH-SE strains were cultured under autotrophic conditions. Consistent with the results of a previous study, BuOH production was observed only in the BUOH-SE strain. Isotopically non-stationary C-metabolic flux analysis revealed that the CO fixation rate was much larger than the BuOH production rate in the BUOH-SE strain (1.70 vs 0.03 mmol gDCW h), implying that the carbon flow for BuOH biosynthesis was less affected by the entire flux distribution. No large difference was observed in the flux of metabolism between the WT and BUOH-SE strains. Contrastingly, in the photosystem, the chlorophyll content and maximum O evolution rate per dry cell weight of the BUOH-SE strain were decreased to 81% and 43% of the WT strain, respectively. Target proteome analysis revealed that the amounts of some proteins related to antennae (ApcA, ApcD, ApcE, and CpcC), photosystem II (PsbB, PsbU, and Psb28-2), and cytochrome bf complex (PetB and PetC) in photosystems decreased in the BUOH-SE strain. The activation of photosynthesis would be a novel approach for further enhancing BuOH production in S. elongatus PCC 7942.
Topics: 1-Butanol; Proteome; Cytochrome b6f Complex; Carbon Dioxide; Photosynthesis; Butanols
PubMed: 36935115
DOI: 10.2323/jgam.2023.03.002 -
BMC Biology Dec 2022Despite a global prevalence of photosynthetic organisms in the ocean's mesophotic zone (30-200+ m depth), the mechanisms that enable photosynthesis to proceed in this...
BACKGROUND
Despite a global prevalence of photosynthetic organisms in the ocean's mesophotic zone (30-200+ m depth), the mechanisms that enable photosynthesis to proceed in this low light environment are poorly defined. Red coralline algae are the deepest known marine benthic macroalgae - here we investigated the light harvesting mechanism and mesophotic acclimatory response of the red coralline alga Lithothamnion glaciale.
RESULTS
Following initial absorption by phycourobilin and phycoerythrobilin in phycoerythrin, energy was transferred from the phycobilisome to photosystems I and II within 120 ps. This enabled delivery of 94% of excitations to reaction centres. Low light intensity, and to a lesser extent a mesophotic spectrum, caused significant acclimatory change in chromophores and biliproteins, including a 10% increase in phycoerythrin light harvesting capacity and a 20% reduction in chlorophyll-a concentration and photon requirements for photosystems I and II. The rate of energy transfer remained consistent across experimental treatments, indicating an acclimatory response that maintains energy transfer.
CONCLUSIONS
Our results demonstrate that responsive light harvesting by phycobilisomes and photosystem functional acclimation are key to red algal success in the mesophotic zone.
Topics: Phycoerythrin; Phycobilisomes; Photosynthesis; Light; Rhodophyta; Photosystem I Protein Complex
PubMed: 36575464
DOI: 10.1186/s12915-022-01480-3