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The Plant Journal : For Cell and... Aug 2022Chlorophyll (Chl) is made up of the tetrapyrrole chlorophyllide and phytol, a diterpenoid alcohol. The photosynthetic protein complexes utilize Chl for light harvesting...
Chlorophyll (Chl) is made up of the tetrapyrrole chlorophyllide and phytol, a diterpenoid alcohol. The photosynthetic protein complexes utilize Chl for light harvesting to produce biochemical energy for plant development. However, excess light and adverse environmental conditions facilitate generation of reactive oxygen species, which damage photosystems I and II (PSI and PSII) and induce their turnover. During this process, Chl is released, and is thought to be recycled via dephytylation and rephytylation. We previously demonstrated that Chl recycling in Arabidopsis under heat stress is mediated by the enzymes chlorophyll dephytylase 1 (CLD1) and chlorophyll synthase (CHLG) using chlg and cld1 mutants. Here, we show that the mutants with high CLD1/CHLG ratio, by different combinations of chlg-1 (a knock-down mutant) and the hyperactive cld1-1 alleles, develop necrotic leaves when grown under long- and short-day, but not continuous light conditions, owing to the accumulation of chlorophyllide in the dark. Combination of chlg-1 with cld1-4 (a knock-out mutant) leads to reduced chlorophyllide accumulation and necrosis. The operation of CLD1 and CHLG as a Chl salvage pathway was also explored in the context of Chl recycling during the turnover of Chl-binding proteins of the two photosystems. CLD1 was found to interact with CHLG and the light-harvesting complex-like proteins OHP1 and LIL3, implying that auxiliary factors are required for this process.
Topics: Arabidopsis; Chlorophyll; Chlorophyllides; Light; Photosynthesis; Photosystem I Protein Complex; Photosystem II Protein Complex
PubMed: 35694901
DOI: 10.1111/tpj.15865 -
Biochimica Et Biophysica Acta.... Oct 2020Cyanobacteria can rapidly regulate the relative activity of their photosynthetic complexes photosystem I and II (PSI and PSII) in response to changes in the illumination...
Cyanobacteria can rapidly regulate the relative activity of their photosynthetic complexes photosystem I and II (PSI and PSII) in response to changes in the illumination conditions. This process is known as state transitions. If PSI is preferentially excited, they go to state I whereas state II is induced either after preferential excitation of PSII or after dark adaptation. Different underlying mechanisms have been proposed in literature, in particular i) reversible shuttling of the external antenna complexes, the phycobilisomes, between PSI and PSII, ii) reversible spillover of excitation energy from PSII to PSI, iii) a combination of both and, iv) increased excited-state quenching of the PSII core in state II. Here we investigated wild-type and mutant strains of Synechococcus sp. PCC 7942 and Synechocystis sp. PCC 6803 using time-resolved fluorescence spectroscopy at room temperature. Our observations support model iv, meaning that increased excited-state quenching of the PSII core occurs in state II thereby balancing the photochemistry of photosystems I and II.
Topics: Photosystem I Protein Complex; Photosystem II Protein Complex; Phycobilisomes; Phycocyanin; Spectrometry, Fluorescence; Synechococcus; Synechocystis; Temperature; Time Factors
PubMed: 32619427
DOI: 10.1016/j.bbabio.2020.148255 -
Bio-protocol Sep 2021Photosynthesis is the main process by which sunlight is harvested and converted into chemical energy and has been a focal point of fundamental research in plant biology...
Photosynthesis is the main process by which sunlight is harvested and converted into chemical energy and has been a focal point of fundamental research in plant biology for decades. In higher plants, the process takes place in the thylakoid membranes where the two photosystems (PSI and PSII) are located. In the past few decades, the evolution of biophysical and biochemical techniques allowed detailed studies of the thylakoid organization and the interaction between protein complexes and cofactors. These studies have mainly focused on model plants, such as , pea, spinach, and tobacco, which are grown in climate chambers even though significant differences between indoor and outdoor growth conditions are present. In this manuscript, we present a new mild-solubilization procedure for use with "fragile" samples such as thylakoids from conifers growing outdoors. Here, the solubilization protocol is optimized with two detergents in two species, namely Norway spruce () and Scots pine (). We have optimized the isolation and characterization of PSI and PSII multimeric mega- and super-complexes in a close-to-native condition by Blue-Native gel electrophoresis. Eventually, our protocol will not only help in the characterization of photosynthetic complexes from conifers but also in understanding winter adaptation.
PubMed: 34604449
DOI: 10.21769/BioProtoc.4144 -
Biochimica Et Biophysica Acta.... Jul 2017Nannochloropsis spp. are algae with high potential for biotechnological applications due to their capacity to accumulate lipids. However, little is known about their... (Comparative Study)
Comparative Study
Nannochloropsis spp. are algae with high potential for biotechnological applications due to their capacity to accumulate lipids. However, little is known about their photosynthetic apparatus and acclimation/photoprotective strategies. In this work, we studied the mechanisms of non-photochemical quenching (NPQ), the fast response to high light stress, in Nannochloropsis gaditana by "locking" the cells in six different states during quenching activation and relaxation. Combining biochemical analysis with time-resolved fluorescence spectroscopy, we correlated each NPQ state with the presence of two well-known NPQ components: de-epoxidized xanthophylls and stress-related antenna proteins (LHCXs). We demonstrated that after exposure to strong light, the rapid quenching that takes place in the antennas of both photosystems was associated with the presence of LHCXs. At later stages, quenching occurs mainly in the antennas of PSII and correlates with the amount of de-epoxidised xanthophylls. We also observed changes in the distribution of excitation energy between photosystems, which suggests redistribution of excitation between photosystems as part of the photo-protective strategy. A multistep model for NPQ induction and relaxation in N. gaditana is discussed.
Topics: Algal Proteins; Fluorescence; Light; Light-Harvesting Protein Complexes; Photosystem I Protein Complex; Photosystem II Protein Complex; Radiation Tolerance; Spectrometry, Fluorescence; Stramenopiles; Xanthophylls
PubMed: 28499880
DOI: 10.1016/j.bbabio.2017.05.003 -
Nature Communications Mar 2012Photosynthesis is a sustainable process that converts light energy into chemical energy. Substantial research efforts are directed towards the application of the...
Photosynthesis is a sustainable process that converts light energy into chemical energy. Substantial research efforts are directed towards the application of the photosynthetic reaction centres, photosystems I and II, as active components for the light-induced generation of electrical power or fuel products. Nonetheless, no integrated photo-bioelectrochemical device that produces electrical power, upon irradiation of an aqueous solution that includes two inter-connected electrodes is known. Here we report the assembly of photobiofuel cells that generate electricity upon irradiation of biomaterial-functionalized electrodes in aqueous solutions. The cells are composed of electrically contacted photosystem II-functionalized photoanodes and an electrically wired bilirubin oxidase/carbon nanotubes-modified cathode. Illumination of the photoanodes yields the oxidation of water to O(2) and the transfer of electrons through the external circuit to the cathode, where O(2) is re-reduced to water.
Topics: Benzoquinones; Bioelectric Energy Sources; Cyanobacteria; Electricity; Electrodes; Light; Nanotubes, Carbon; Oxidation-Reduction; Oxidoreductases Acting on CH-CH Group Donors; Photosynthesis; Photosystem II Protein Complex; Polymers
PubMed: 22415833
DOI: 10.1038/ncomms1741 -
FEBS Letters Jan 2012The half-life times of photosystem I and II proteins were determined using (15)N-labeling and mass spectrometry. The half-life times (30-75h for photosystem I components...
The half-life times of photosystem I and II proteins were determined using (15)N-labeling and mass spectrometry. The half-life times (30-75h for photosystem I components and <1-11h for the large photosystem II proteins) were similar when proteins were isolated from monomeric vs. oligomeric complexes on Blue-Native gels, suggesting that the two forms of both photosystems can interchange on a timescale of <1h or that only one form of each photosystem exists in thylakoids in vivo. The half-life times of proteins associated with either photosystem generally were unaffected by the absence of Small Cab-like proteins.
Topics: Cells, Cultured; Cyanobacteria; Half-Life; Multiprotein Complexes; Photosynthetic Reaction Center Complex Proteins; Photosystem I Protein Complex; Photosystem II Protein Complex; Proteolysis; Synechocystis; Time Factors
PubMed: 22197103
DOI: 10.1016/j.febslet.2011.12.010 -
The Journal of Biological Chemistry Sep 2008We have investigated the photosynthetic properties of Acaryochloris marina, a cyanobacterium distinguished by having a high level of chlorophyll d, which has its...
We have investigated the photosynthetic properties of Acaryochloris marina, a cyanobacterium distinguished by having a high level of chlorophyll d, which has its absorption bands shifted to the red when compared with chlorophyll a. Despite this unusual pigment content, the overall rate and thermodynamics of the photosynthetic electron flow are similar to those of chlorophyll a-containing species. The midpoint potential of both cytochrome f and the primary electron donor of photosystem I (P(740)) were found to be unchanged with respect to those prevailing in organisms having chlorophyll a, being 345 and 425 mV, respectively. Thus, contrary to previous reports (Hu, Q., Miyashita, H., Iwasaki, I. I., Kurano, N., Miyachi, S., Iwaki, M., and Itoh, S. (1998) Proc. Natl. Acad. Sci. U. S. A. 95, 13319-13323), the midpoint potential of the electron donor P(740) has not been tuned to compensate for the decrease in excitonic energy in A. marina and to maintain the reducing power of photosystem I. We argue that this is a weaker constraint on the engineering of the oxygenic photosynthetic electron transfer chain than preserving the driving force for plastoquinol oxidation by P(740), via the cytochrome b(6)f complex. We further show that there is no restriction in the diffusion of the soluble electron carrier between cytochrome b(6)f and photosystem I in A. marina, at variance with plants. This difference probably reflects the simplified ultrastructure of the thylakoids of this organism, where no segregation into grana and stroma lamellae is observed. Nevertheless, chlorophyll fluorescence measurements suggest that there is energy transfer between adjacent photosystem II complexes but not from photosystem II to photosystem I, indicating spatial separation between the two photosystems.
Topics: Biochemistry; Chlorophyll; Cyanobacteria; Cytochrome b6f Complex; Electrons; Kinetics; Light; Models, Biological; Oxidation-Reduction; Photosystem I Protein Complex; Spectrometry, Fluorescence; Thermodynamics; Thylakoids; Time Factors
PubMed: 18635535
DOI: 10.1074/jbc.M803047200 -
Plants (Basel, Switzerland) Apr 2023Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) is the rate-limiting enzyme for photosynthesis. Rubisco activase (RCA) can regulate the Rubisco activation...
Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) is the rate-limiting enzyme for photosynthesis. Rubisco activase (RCA) can regulate the Rubisco activation state, influencing Rubisco activity and photosynthetic rate. We obtained transgenic maize plants that overproduced rice () and evaluated photosynthesis in these plants by measuring gas exchange, energy conversion efficiencies in photosystem (PS) I and PSII, and Rubisco activity and activation state. The lines showed significantly higher initial Rubisco activity and activation state, net photosynthetic rate, and PSII photochemical quantum yield than wild-type plants. These results suggest that overexpression can promote maize photosynthesis by increasing the Rubisco activation state.
PubMed: 37111838
DOI: 10.3390/plants12081614 -
The Plant Journal : For Cell and... Jan 2022In this Perspective article, we describe the visions of the PhotoRedesign consortium funded by the European Research Council of how to enhance photosynthesis. The light...
In this Perspective article, we describe the visions of the PhotoRedesign consortium funded by the European Research Council of how to enhance photosynthesis. The light reactions of photosynthesis in individual phototrophic species use only a fraction of the solar spectrum, and high light intensities can impair and even damage the process. In consequence, expanding the solar spectrum and enhancing the overall energy capacity of the process, while developing resilience to stresses imposed by high light intensities, could have a strong positive impact on food and energy production. So far, the complexity of the photosynthetic machinery has largely prevented improvements by conventional approaches. Therefore, there is an urgent need to develop concepts to redesign the light-harvesting and photochemical capacity of photosynthesis, as well as to establish new model systems and toolkits for the next generation of photosynthesis researchers. The overall objective of PhotoRedesign is to reconfigure the photosynthetic light reactions so they can harvest and safely convert energy from an expanded solar spectrum. To this end, a variety of synthetic biology approaches, including de novo design, will combine the attributes of photosystems from different photoautotrophic model organisms, namely the purple bacterium Rhodobacter sphaeroides, the cyanobacterium Synechocystis sp. PCC 6803 and the plant Arabidopsis thaliana. In parallel, adaptive laboratory evolution will be applied to improve the capacity of reimagined organisms to cope with enhanced input of solar energy, particularly in high and fluctuating light.
Topics: Arabidopsis; Directed Molecular Evolution; Light; Photosynthesis; Photosystem I Protein Complex; Photosystem II Protein Complex; Rhodobacter sphaeroides; Synechocystis; Synthetic Biology
PubMed: 34709696
DOI: 10.1111/tpj.15552 -
Proceedings of the National Academy of... Mar 2019Photosynthetic organisms prevent oxidative stress from light energy absorbed in excess through several photoprotective mechanisms. A major component is thermal...
Photosynthetic organisms prevent oxidative stress from light energy absorbed in excess through several photoprotective mechanisms. A major component is thermal dissipation of chlorophyll singlet excited states and is called nonphotochemical quenching (NPQ). NPQ is catalyzed in green algae by protein subunits called LHCSRs (Light Harvesting Complex Stress Related), homologous to the Light Harvesting Complexes (LHC), constituting the antenna system of both photosystem I (PSI) and PSII. We investigated the role of LHCSR1 and LHCSR3 in NPQ activation to verify whether these proteins are involved in thermal dissipation of PSI excitation energy, in addition to their well-known effect on PSII. To this aim, we measured the fluorescence emitted at 77 K by whole cells in a quenched or unquenched state, using green fluorescence protein as the internal standard. We show that NPQ activation by high light treatment in leads to energy quenching in both PSI and PSII antenna systems. By analyzing quenching properties of mutants affected on the expression of LHCSR1 or LHCSR3 gene products and/or state 1-state 2 transitions or zeaxanthin accumulation, namely, , , , , -complemented and , we showed that PSI undergoes NPQ through quenching of the associated LHCII antenna. This quenching event is fast-reversible on switching the light off, is mainly related to LHCSR3 activity, and is dependent on thylakoid luminal pH. Moreover, PSI quenching could also be observed in the absence of zeaxanthin or STT7 kinase activity.
Topics: Algal Proteins; Chlamydomonas reinhardtii; Chlorophyll; Light-Harvesting Protein Complexes; Luminescent Proteins; Photosynthesis; Photosystem I Protein Complex; Photosystem II Protein Complex; Protein Kinases; Temperature; Zeaxanthins
PubMed: 30782831
DOI: 10.1073/pnas.1809812116