-
Frontiers in Plant Science 2023The need to acclimate to different environmental conditions is central to the evolution of cyanobacteria. Far-red light (FRL) photoacclimation, or FaRLiP, is an...
The need to acclimate to different environmental conditions is central to the evolution of cyanobacteria. Far-red light (FRL) photoacclimation, or FaRLiP, is an acclimation mechanism that enables certain cyanobacteria to use FRL to drive photosynthesis. During this process, a well-defined gene cluster is upregulated, resulting in changes to the photosystems that allow them to absorb FRL to perform photochemistry. Because FaRLiP is widespread, and because it exemplifies cyanobacterial adaptation mechanisms in nature, it is of interest to understand its molecular evolution. Here, we performed a phylogenetic analysis of the photosystem I subunits encoded in the FaRLiP gene cluster and analyzed the available structural data to predict ancestral characteristics of FRL-absorbing photosystem I. The analysis suggests that FRL-specific photosystem I subunits arose relatively late during the evolution of cyanobacteria when compared with some of the FRL-specific subunits of photosystem II, and that the order Nodosilineales, which include strains like and sp. PCC 7335, could have obtained FaRLiP via horizontal gene transfer. We show that the ancestral form of FRL-absorbing photosystem I contained three chlorophyll -binding sites in the PsaB2 subunit, and a rotated chlorophyll molecule in the A site of the electron transfer chain. Along with our previous study of photosystem II expressed during FaRLiP, these studies describe the molecular evolution of the photosystem complexes encoded by the FaRLiP gene cluster.
PubMed: 38053766
DOI: 10.3389/fpls.2023.1289199 -
Biological Research May 2017Acaryochloris marina is an oxygenic cyanobacterium that utilizes far-red light for photosynthesis. It has an expanded genome, which helps in its adaptability to the... (Review)
Review
Acaryochloris marina is an oxygenic cyanobacterium that utilizes far-red light for photosynthesis. It has an expanded genome, which helps in its adaptability to the environment, where it can survive on low energy photons. Its major light absorbing pigment is chlorophyll d and it has α-carotene as a major carotenoid. Light harvesting antenna includes the external phycobilin binding proteins, which are hexameric rods made of phycocyanin and allophycocyanins, while the small integral membrane bound chlorophyll binding proteins are also present. There is specific chlorophyll a molecule in both the reaction center of Photosystem I (PSI) and PSII, but majority of the reaction center consists of chlorophyll d. The composition of the PSII reaction center is debatable especially the role and position of chlorophyll a in it. Here we discuss the photosystems of this bacterium and its related biology.
Topics: Adaptation, Physiological; Chlorophyll; Cyanobacteria; Genome, Bacterial; Photosynthesis
PubMed: 28526061
DOI: 10.1186/s40659-017-0120-0 -
Current Opinion in Structural Biology Aug 2016Photosystem I (PSI) is one of the two photosystems in oxygenic photosynthesis, and absorbs light energy to generate reducing power for the reduction of NADP to NADPH... (Review)
Review
Photosystem I (PSI) is one of the two photosystems in oxygenic photosynthesis, and absorbs light energy to generate reducing power for the reduction of NADP to NADPH with a quantum efficiency close to 100%. The plant PSI core forms a supercomplex with light-harvesting complex I (LHCI) with a total molecular weight of over 600kDa. Recent X-ray structure analysis of the PSI-LHCI membrane-protein supercomplex has revealed detailed arrangement of the light-harvesting pigments and other cofactors especially within LHCI. Here we introduce the overall structure of the PSI-LHCI supercomplex, and then focus on the excited energy transfer (EET) pathways from LHCI to the PSI core and photoprotection mechanisms based on the structure obtained.
Topics: Energy Transfer; Light-Harvesting Protein Complexes; Photochemical Processes; Photosystem I Protein Complex; Plants
PubMed: 27131043
DOI: 10.1016/j.sbi.2016.04.004 -
The Plant Journal : For Cell and... May 2015Plants and algae have acquired the ability to acclimatize to ever-changing environments to survive. During photosynthesis, light energy is converted by several membrane... (Review)
Review
Plants and algae have acquired the ability to acclimatize to ever-changing environments to survive. During photosynthesis, light energy is converted by several membrane protein supercomplexes into electrochemical energy, which is eventually used to assimilate CO2 . The efficiency of photosynthesis is modulated by many environmental factors, including temperature, drought, CO2 concentration, and the quality and quantity of light. Recently, our understanding of such regulators of photosynthesis and the underlying molecular mechanisms has increased considerably. The photosynthetic supercomplexes undergo supramolecular reorganizations within a short time after receiving environmental cues. These reorganizations include state transitions that balance the excitation of the two photosystems: qE quenching, which thermally dissipates excess energy at the level of the light-harvesting antenna, and cyclic electron flow, which supplies the increased ATP demanded by CO2 assimilation and the pH gradient to activate qE quenching. This review focuses on the recent findings regarding the environmental regulation of photosynthesis in model organisms, paying particular attention to the unicellular green alga Chlamydomonas reinhardtii, which offer a glimpse into the dynamic behavior of photosynthetic machinery in nature.
Topics: Chlamydomonas reinhardtii; Electrons; Gene Expression Regulation, Plant; Light-Harvesting Protein Complexes; Models, Molecular; Photosynthesis; Photosystem I Protein Complex; Photosystem II Protein Complex; Xanthophylls
PubMed: 25702778
DOI: 10.1111/tpj.12805 -
European Journal of Biochemistry May 1996Photosystems I and II drive oxygenic photosynthesis. This requires biochemical systems with remarkable properties, allowing these membrane-bound pigment-protein... (Review)
Review
Photosystems I and II drive oxygenic photosynthesis. This requires biochemical systems with remarkable properties, allowing these membrane-bound pigment-protein complexes to oxidise water and produce NAD(P)H. The protein environment provides a scaffold in the membrane on which cofactors are placed at optimum distance and orientation, ensuring a rapid, efficient trapping and conversion of light energy. The polypeptide core also tunes the redox potentials of cofactors and provides for unidirectional progress of various reaction steps. The electron transfer pathways use a variety of inorganic and organic cofactors, including amino acids. This review sets out some of the current ideas and data on the cofactors and polypeptides of photosystems I and II.
Topics: Amino Acid Sequence; Bacterial Proteins; Electron Transport; Evolution, Molecular; Models, Molecular; Molecular Sequence Data; Oxygen; Photochemistry; Photosynthesis; Photosynthetic Reaction Center Complex Proteins; Photosystem I Protein Complex; Photosystem II Protein Complex; Plant Proteins; Protein Conformation; Sequence Homology, Amino Acid
PubMed: 8647094
DOI: 10.1111/j.1432-1033.1996.00519.x -
The New Phytologist Nov 2020Photosystems I and II are the central components of the solar energy conversion machinery in oxygenic photosynthesis. They are large functional units embedded in the... (Review)
Review
Photosystems I and II are the central components of the solar energy conversion machinery in oxygenic photosynthesis. They are large functional units embedded in the photosynthetic membranes, where they harvest light and use its energy to drive electrons from water to NADPH. Their composition and organization change in response to different environmental conditions, making these complexes dynamic units. Some of the interactions between subunits survive purification, resulting in the well-defined structures that were recently resolved by cryo-electron microscopy. Other interactions instead are weak, preventing the possibility of isolating and thus studying these complexes in vitro. This review focuses on these supercomplexes of vascular plants, which at the moment cannot be 'seen' but that represent functional units in vivo.
Topics: Cryoelectron Microscopy; Electrons; Light-Harvesting Protein Complexes; Oxygen; Photosynthesis; Photosystem I Protein Complex; Photosystem II Protein Complex
PubMed: 32562266
DOI: 10.1111/nph.16758 -
Photosynthesis Research Dec 2018The light-harvesting chlorophyll a/b binding proteins (LHCP) belong to a large family of membrane proteins. They form the antenna complexes of photosystem I and II and... (Review)
Review
The light-harvesting chlorophyll a/b binding proteins (LHCP) belong to a large family of membrane proteins. They form the antenna complexes of photosystem I and II and function in light absorption and transfer of the excitation energy to the photosystems. As nuclear-encoded proteins, the LHCPs are imported into the chloroplast and further targeted to their final destination-the thylakoid membrane. Due to their hydrophobicity, the formation of the so-called 'transit complex' in the stroma is important to prevent their aggregation in this aqueous environment. The posttranslational LHCP targeting mechanism is well regulated through the interaction of various soluble and membrane-associated protein components and includes several steps: the binding of the LHCP to the heterodimeric cpSRP43/cpSRP54 complex to form the soluble transit complex; the docking of the transit complex to the SRP receptor cpFtsY and the Alb3 translocase at the membrane followed by the release and integration of the LHCP into the thylakoid membrane in a GTP-dependent manner. This review summarizes the molecular mechanisms and dynamics behind the posttranslational LHCP targeting to the thylakoid membrane of Arabidopsis thaliana.
Topics: Light-Harvesting Protein Complexes; Plants; Protein Multimerization; Protein Transport; Signal Recognition Particle; Thylakoids
PubMed: 29956039
DOI: 10.1007/s11120-018-0544-6 -
Nature Communications Apr 2024Dinoflagellates are ecologically important and essential to corals and other cnidarians as phytosymbionts, but their photosystems had been underexplored. Recently,...
Dinoflagellates are ecologically important and essential to corals and other cnidarians as phytosymbionts, but their photosystems had been underexplored. Recently, photosystem I (PSI) of dinoflagellate sp. was structurally characterized using cryo-Electron Microscopy (cryo-EM). These analyses revealed a distinct organization of the PSI supercomplex, including two previously unidentified subunits, PsaT and PsaU, and shed light on interactions between light harvesting antenna proteins and the PSI core. These results have implications with respect to the evolution of dinoflagellates and their association with cnidarians.
Topics: Photosystem I Protein Complex; Photosynthesis; Chlorophyll; Dinoflagellida; Photosystem II Protein Complex; Light; Light-Harvesting Protein Complexes
PubMed: 38637576
DOI: 10.1038/s41467-024-47797-1 -
Ecotoxicology and Environmental Safety Jan 2023Lead (Pb) pollution in the soil sub-ecosystem has been a continuously growing problem due to economic development and ever-increasing anthropogenic activities across the...
Lead (Pb) pollution in the soil sub-ecosystem has been a continuously growing problem due to economic development and ever-increasing anthropogenic activities across the world. In this study, the photosynthetic performance and antioxidant capacity of Triticeae cereals (rye, wheat and triticale) were compared to assess the activities of antioxidants, the degree of oxidative damage, photochemical efficiency and the levels of photosynthetic proteins under Pb stress (0.5 mM, 1 mM and 2 mM Pb (NO)). Compared with triticale, Pb treatments imposed severe oxidative damage in rye and wheat. In addition, the highest activity of major antioxidant enzymes (SOD, POD, CAT, and GPX) was also found to be elevated. Triticale accumulated the highest Pb contents in roots. The concentration of mineral ions (Mg, Ca, and K) was also high in its leaves, compared with rye and wheat. Consistently, triticale showed higher photosynthetic activity under Pb stress. Immunoblotting of proteins revealed that rye and wheat have significantly lower levels of D1 (photosystem II subunit A, PsbA) and D2 (photosystem II subunit D, PsbD) proteins, while no obvious decrease was noticed in triticale. The amount of light-harvesting complex II b6 (Lhcb6; CP24) and light-harvesting complex II b5 (Lhcb5; CP26) was significantly increased in rye and wheat. However, the increase in PsbS (photosystem II subunit S) protein only occurred in wheat and triticale exposed to Pb treatment. Taken together, these findings demonstrate that triticale shows higher antioxidant capacity and photosynthetic efficiency than wheat and rye under Pb stress, suggesting that triticale has high tolerance to Pb and could be used as a heavy metal-tolerant plant.
Topics: Ecosystem; Lead; Photosystem II Protein Complex; Secale; Triticale; Triticum; Oxidative Stress; Soil Pollutants
PubMed: 36508799
DOI: 10.1016/j.ecoenv.2022.114356 -
Bioscience Reports Jan 2023Photosystem I (PSI) with its associated light-harvesting system is the most important generator of reducing power in photosynthesis. The PSI core complex is highly...
Photosystem I (PSI) with its associated light-harvesting system is the most important generator of reducing power in photosynthesis. The PSI core complex is highly conserved, whereas peripheral subunits as well as light-harvesting proteins (LHCI) reveal a dynamic plasticity. Moreover, in green alga, PSI-LHCI complexes are found as monomers, dimers, and state transition complexes, where two LHCII trimers are associated. Herein, we show light-dependent phosphorylation of PSI subunits PsaG and PsaH as well as Lhca6. Potential consequences of the dynamic phosphorylation of PsaG and PsaH are structurally analyzed and discussed in regard to the formation of the monomeric, dimeric, and LHCII-associated PSI-LHCI complexes.
Topics: Photosystem I Protein Complex; Phosphorylation; Light-Harvesting Protein Complexes; Chlamydomonas reinhardtii; Thylakoids
PubMed: 36477263
DOI: 10.1042/BSR20220369