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Photochemical & Photobiological... Nov 2023Chlamydomonas (C.) reinhardtii metabolomic changes in cyclic electron flow-dependent mutants are still unknown. Here, we used mass spectrometric analysis to monitor the...
Chlamydomonas (C.) reinhardtii metabolomic changes in cyclic electron flow-dependent mutants are still unknown. Here, we used mass spectrometric analysis to monitor the changes in metabolite levels in wild-type, cyclic electron-deficient mutants pgrl1 and pgr5 grown under high-light stress. A total of 55 metabolites were detected using GC-MS analysis. High-light stress-induced selective anaplerotic amino acids in pgr5. In addition, pgr5 showed enhancement in carbohydrate, polyamine, and polyol metabolism by 2.5-fold under high light. In response to high light, pgr5 triggers an increase in several metabolites involved in regulating osmotic pressure. Among these metabolites are glycerol pathway compounds such as glycerol-3-phosphate and glyceryl-glycoside, which increase significantly by 1.55 and 3.07 times, respectively. In addition, pgr5 also enhanced proline and putrescine levels by 2.6- and 1.36-fold under high light. On the other hand, pgrl1-induced metabolites, such as alanine and serine, are crucial for photorespiration when subjected to high-light stress. We also observed a significant increase in levels of polyols and glycerol by 1.37- and 2.97-fold in pgrl1 under high-light stress. Both correlation network studies and KEGG pathway enrichment analysis revealed that metabolites related to several biological pathways, such as amino acid, carbohydrate, TCA cycle, and fatty acid metabolism, were positively correlated in pgrl1 and pgr5 under high-light stress conditions. The relative mRNA expression levels of genes related to the TCA cycle, including PDC3, ACH1, OGD2, OGD3, IDH3, and MDH4, were significantly upregulated in pgrl1 and pgr5 under HL. In pgr5, the MDH1 level was significantly increased, while ACS1, ACS3, IDH2, and IDH3 levels were reduced considerably in pgrl1 under high-light stress. The current study demonstrates both pgr5 and prgl1 showed a differential defense response to high-light stress at the primary metabolites and mRNA expression level, which can be added to the existing knowledge to explore molecular regulatory responses of prg5 and pgrl1 to high-light stress.
Topics: Electron Transport; Photosystem I Protein Complex; Chlamydomonas reinhardtii; Glycerol; Photosynthesis; RNA, Messenger; Light
PubMed: 37751074
DOI: 10.1007/s43630-023-00478-2 -
Biochimica Et Biophysica Acta.... Nov 2023Phycobilisomes (PBSs), which are huge pigment-protein complexes displaying distinctive color variations, bind to photosystem cores for excitation-energy transfer. It is...
Phycobilisomes (PBSs), which are huge pigment-protein complexes displaying distinctive color variations, bind to photosystem cores for excitation-energy transfer. It is known that isolation of supercomplexes consisting of PBSs and photosystem I (PSI) or PBSs and photosystem II is challenging due to weak interactions between PBSs and the photosystem cores. In this study, we succeeded in purifying PSI-monomer-PBS and PSI-dimer-PBS supercomplexes from the cyanobacterium Anabaena sp. PCC 7120 grown under iron-deficient conditions by anion-exchange chromatography, followed by trehalose density gradient centrifugation. The absorption spectra of the two types of supercomplexes showed apparent bands originating from PBSs, and their fluorescence-emission spectra exhibited characteristic peaks of PBSs. Two-dimensional blue-native (BN)/SDS-PAGE of the two samples showed a band of CpcL, which is a linker protein of PBS, in addition to PsaA/B. Since interactions of PBSs with PSI are easily dissociated during BN-PAGE using thylakoids from this cyanobacterium grown under iron-replete conditions, it is suggested that iron deficiency for Anabaena induces tight association of CpcL with PSI, resulting in the formation of PSI-monomer-PBS and PSI-dimer-PBS supercomplexes. Based on these findings, we discuss interactions of PBSs with PSI in Anabaena.
Topics: Photosystem I Protein Complex; Thylakoids; Anabaena; Photosystem II Protein Complex; Cyanobacteria; Phycobilisomes; Iron
PubMed: 37321385
DOI: 10.1016/j.bbabio.2023.148993 -
Chemosphere Oct 2023Nitrogen pollution and pesticides such as photosystem II (PSII) inhibitor herbicides have several detrimental impacts on coral reefs, including breakdown of the...
Individual and combined effects of herbicide prometryn and nitrate enrichment at environmentally relevant concentrations on photosynthesis, oxidative stress, and endosymbiont community diversity of coral Acropora hyacinthus.
Nitrogen pollution and pesticides such as photosystem II (PSII) inhibitor herbicides have several detrimental impacts on coral reefs, including breakdown of the symbiosis between host corals and photosynthetic symbionts. Although nitrogen and PSII herbicide pollution separately cause coral bleaching, the combined effects of these stressors at environmentally relevant concentrations on corals have not been assessed. Here, we report the combined effects of nitrate enrichment and PSII herbicide (prometryn) exposure on photosynthesis, oxidative status and endosymbiont community diversity of the reef-building coral Acropora hyacinthus. Coral fragments were exposed in a mesocosm system to nitrate enrichment (9 μmol/L) and two prometryn concentrations (1 and 5 μg/L). The results showed that sustained prometryn exposure in combination with nitrate enrichment stress had significant detrimental impacts on photosynthetic apparatus [the maximum quantum efficiency of photosystem II (Fv/Fm), nonphotochemical quenching (NPQ) and oxidative status in the short term. Nevertheless, the adaptive mechanism of corals allowed the normal physiological state to be recovered following 1 μg/L prometryn and 9 μmol/L nitrate enrichment individual exposure. Moreover, exposure for 9 days was insufficient to trigger a shift in Symbiodiniaceae community. Most importantly, the negative impact of exposure to the combined environmental concentrations of 1 μg/L prometryn and 9 μmol/L nitrate enrichment was found to be significantly greater on the Fv/Fm, quantum yield of non-regulated energy dissipation [Y(NO)], NPQ, and oxidative status of corals compared to the impact of individual stressors. Our results show that interactions between prometryn stress and nitrate enrichment have a synergistic impact on the photosynthetic and oxidative stress responses of corals. This study provides valuable insights into combined effects of nitrate enrichment and PSII herbicides pollution for coral's physiology. Environmental concentrations of PSII herbicides may be more harmful to photosystems and antioxidant systems of corals under nitrate enrichment stress. Thus, future research and management of seawater quality stressors should consider combined impacts on corals rather than just the impacts of individual stressors alone.
Topics: Animals; Anthozoa; Prometryne; Nitrates; Hyacinthus; Herbicides; Photosystem II Protein Complex; Coral Reefs; Photosynthesis; Oxidative Stress; Symbiosis
PubMed: 37543226
DOI: 10.1016/j.chemosphere.2023.139729 -
Current Biology : CB Oct 2023Warnowiid dinoflagellates contain a highly complex camera-eye-like structure called the ocelloid that is composed of different organelles resembling parts of metazoan...
Warnowiid dinoflagellates contain a highly complex camera-eye-like structure called the ocelloid that is composed of different organelles resembling parts of metazoan eyes, including a modified plastid that serves as the retinal body. The overall structure of the ocelloid has been investigated by microscopy; because warnowiids are not in culture and are rare in nature, we know little about their function. Here, we generate single-cell transcriptomes from 18 warnowiid cells collected directly from the marine environment representing all 4 known genera and 1 previously undescribed genus, as well as 8 cells from a related lineage, the polykrikoids. Phylogenomic analyses show that photosynthesis was independently lost twice in warnowiids. Interestingly, the non-photosynthetic taxa still express a variety of photosynthesis-related proteins. Nematodinium and Warnowia (known or suspected to be photosynthetic) unsurprisingly express a full complement of photosynthetic pathway components. However, non-photosynthetic genera with ocelloids were also found to express light-harvesting complexes, photosystem I, photosynthetic electron transport (PET), cytochrome bf, and, in Erythropsidinium, plastid ATPase, representing all major complexes except photosystem II and the Calvin cycle. This suggests that the non-photosynthetic retinal body has retained a reduced but still substantial photosynthetic apparatus that perhaps functions using cyclic electron flow (CEF). This may support ATP synthesis in a reduced capacity, but it is also possible that the photosystem has been co-opted to function as a light-driven proton pump at the heart of the sensory mechanism within the complex architecture of ocelloids.
PubMed: 37703877
DOI: 10.1016/j.cub.2023.08.052 -
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 -
Chembiochem : a European Journal of... Jul 2023Photosynthetic organisms like plants, algae, and cyanobacteria use light for the regeneration of dihydronicotinamide dinucleotide phosphate (NADPH). The process starts...
Photosynthetic organisms like plants, algae, and cyanobacteria use light for the regeneration of dihydronicotinamide dinucleotide phosphate (NADPH). The process starts with the light-driven oxidation of water by photosystem II (PSII) and the released electrons are transferred via the cytochrome b f complex towards photosystem I (PSI). This membrane protein complex is responsible for the light-driven reduction of the soluble electron mediator ferredoxin (Fd), which passes the electrons to ferredoxin NADP reductase (FNR). Finally, NADPH is regenerated by FNR at the end of the electron transfer chain. In this study, we established a clickable fusion system for in vitro NADPH regeneration with PSI-Fd and PSI-Fd-FNR, respectively. For this, we fused immunity protein 7 (Im7) to the C-terminus of the PSI-PsaE subunit in the cyanobacterium Synechocystis sp. PCC 6803. Furthermore, colicin DNase E7 (E7) fusion chimeras of Fd and FNR with varying linker domains were expressed in Escherichia coli. Isolated Im7-PSI was coupled with the E7-Fd or E7-Fd-FNR fusion proteins through high-affinity binding of the E7/Im7 protein pair. The corresponding complexes were tested for NADPH regeneration capacity in comparison to the free protein systems demonstrating the general applicability of the strategy.
Topics: NADP; Photosystem I Protein Complex; Ferredoxin-NADP Reductase; Ferredoxins; Electron Transport; Synechocystis
PubMed: 37093822
DOI: 10.1002/cbic.202300025 -
Cells Jan 2024CAH3 is the only carbonic anhydrase (CA) present in the thylakoid lumen of the green algae . The monomer of the enzyme has a molecular weight of ~29.5 kDa with high CA... (Review)
Review
CAH3 is the only carbonic anhydrase (CA) present in the thylakoid lumen of the green algae . The monomer of the enzyme has a molecular weight of ~29.5 kDa with high CA activity. Through its dehydration activity, CAH3 can be involved either in the carbon-concentrating mechanism supplying CO for RuBisCO in the pyrenoid or in supporting the maximal photosynthetic activity of photosystem II (PSII) by accelerating the removal of protons from the active center of the water-oxidizing complex. Both proposed roles are considered in this review, together with a description of the enzymatic parameters of native and recombinant CAH3, the crystal structure of the protein, and the possible use of lumenal CA as a tool for increasing biomass production in higher plants. The identified involvement of lumenal CAH3 in the function of PSII is still unique among green algae and higher plants and can be used to understand the mechanism(s) of the functional interconnection between PSII and the proposed CA(s) of the thylakoid lumen in other organisms.
Topics: Biomass; Carbonic Anhydrases; Chlamydomonas reinhardtii; Plastids; Thylakoids
PubMed: 38247801
DOI: 10.3390/cells13020109 -
Photosynthesis Research Dec 2023Organic bilayers or amorphous silica films of a few nanometer thickness featuring embedded molecular wires offer opportunities for chemically separating while at the... (Review)
Review
Organic bilayers or amorphous silica films of a few nanometer thickness featuring embedded molecular wires offer opportunities for chemically separating while at the same time electronically connecting photo- or electrocatalytic components. Such ultrathin membranes enable the integration of components for which direct coupling is not sufficiently efficient or stable. Photoelectrocatalytic systems for the generation or utilization of renewable energy are among the most prominent ones for which ultrathin separation layers open up new approaches for component integration for improving efficiency. Recent advances in the assembly and spectroscopic, microscopic, and photoelectrochemical characterization have enabled the systematic optimization of the structure, energetics, and density of embedded molecular wires for maximum charge transfer efficiency. The progress enables interfacial designs for the nanoscale integration of the incompatible oxidation and reduction catalysis environments of artificial photosystems and of microbial (or biomolecular)-abiotic systems for renewable energy.
PubMed: 38108928
DOI: 10.1007/s11120-023-01061-7 -
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 -
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