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1.
Nat Commun ; 13(1): 4045, 2022 Jul 13.
Artigo em Inglês | MEDLINE | ID: mdl-35831297

RESUMO

The conversion of light energy to chemical energy by photosynthesis requires the concerted action of large protein complexes in the thylakoid membrane. Recent work has provided fundamental insights into the three-dimensional structure of these complexes, but how they are assembled from hundreds of parts remains poorly understood. Particularly little is known about the biogenesis of the cytochrome b6f complex (Cytb6f), the redox-coupling complex that interconnects the two photosystems. Here we report the identification of a factor that guides the assembly of Cytb6f in thylakoids of chloroplasts. The protein, DE-ETIOLATION-INDUCED PROTEIN 1 (DEIP1), resides in the thylakoid membrane and is essential for photoautotrophic growth. Knock-out mutants show a specific loss of Cytb6f, and are defective in complex assembly. We demonstrate that DEIP1 interacts with the two cytochrome subunits of the complex, PetA and PetB, and mediates the assembly of intermediates in Cytb6f biogenesis. The identification of DEIP1 provides an entry point into the study of the assembly pathway of a crucial complex in photosynthetic electron transfer.


Assuntos
Arabidopsis , Complexo Citocromos b6f , Arabidopsis/genética , Arabidopsis/metabolismo , Complexo Citocromos b6f/genética , Complexo Citocromos b6f/metabolismo , Citocromos b/metabolismo , Estiolamento , Fotossíntese , Tilacoides/metabolismo
2.
Nat Plants ; 8(7): 840-855, 2022 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-35798975

RESUMO

Non-photochemical quenching (NPQ) plays an important role for phototrophs in decreasing photo-oxidative damage. qH is a sustained form of NPQ and depends on the plastid lipocalin (LCNP). A thylakoid membrane-anchored protein SUPPRESSOR OF QUENCHING1 (SOQ1) prevents qH formation by inhibiting LCNP. SOQ1 suppresses qH with its lumen-located thioredoxin (Trx)-like and NHL domains. Here we report structural data, genetic modification and biochemical characterization of Arabidopsis SOQ1 lumenal domains. Our results show that the Trx-like and NHL domains are associated together, with the cysteine motif located at their interface. Residue E859, required for SOQ1 function, is pivotal for maintaining the Trx-NHL association. Importantly, the C-terminal region of SOQ1 forms an independent ß-stranded domain that has structural homology to the N-terminal domain of bacterial disulfide bond protein D and is essential for negative regulation of qH. Furthermore, SOQ1 is susceptible to cleavage at the loops connecting the neighbouring lumenal domains both in vitro and in vivo, which could be a regulatory process for its suppression function of qH.


Assuntos
Proteínas de Arabidopsis , Arabidopsis , Arabidopsis/metabolismo , Proteínas de Arabidopsis/metabolismo , Plastídeos/metabolismo , Tilacoides/metabolismo
3.
Biochim Biophys Acta Bioenerg ; 1863(7): 148589, 2022 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-35779585

RESUMO

In diatoms, light-harvesting processes take place in a specific group of proteins, called fucoxanthin chlorophyll a/c proteins (FCP). This group includes many members and represents the major characteristic of the diatom photosynthetic apparatus, with specific pigments bound (chlorophyll c, fucoxanthin, diadino- and diatoxanthin besides chlorophyll a). In thylakoids, FCP and photosystems (PS) form multimeric supercomplexes. In this study, we compared the biochemical properties of PS supercomplexes isolated from Thalassiosira pseudonana cells grown under low light or high light conditions, respectively. High light acclimation changed the molecular features of the PS and their ratio in thylakoids. In PSII, no obvious changes in polypeptide composition were observed, whereas for PSI changes in one specific group of FCP proteins were detected. As reported before, the amount of xanthophyll cycle pigments and their de-epoxidation ratio was increased in PSI under HL. In PSII, however, no additional xanthophyll cycle pigments occurred, but the de-epoxidation ratio was increased as well. This comparison suggests how mechanisms of photoprotection might take place within and in the proximity of the PS, which gives new insights into the capacity of diatoms to adapt to different conditions and in different environments.


Assuntos
Diatomáceas , Clorofila A/metabolismo , Diatomáceas/metabolismo , Tilacoides/metabolismo , Xantofilas/metabolismo
4.
J Phys Chem Lett ; 13(24): 5683-5691, 2022 Jun 23.
Artigo em Inglês | MEDLINE | ID: mdl-35709359

RESUMO

The major photosystem II light-harvesting antenna (LHCII) is the most abundant membrane protein in nature and plays an indispensable role in light harvesting and photoprotection in the plant thylakoid. Here, we show that "pseudothylakoid characteristics" can be observed in artificial LHCII membranes. In our proteoliposomal system, at high LHCII densities, the liposomes become stacked, mimicking the in vivo thylakoid grana membranes. Furthermore, an unexpected, unstructured emission peak at ∼730 nm appears, similar in appearance to photosystem I emission, but with a clear excimeric character that has never been previously reported. These states correlate with the increasing density of LHCII in the membrane and a decrease in its average fluorescence lifetime. The appearance of these low-energy states can also occur in natural plant membrane structures, which has unique consequences for the interpretation of the spectroscopic and physiological properties of the photosynthetic membrane.


Assuntos
Complexos de Proteínas Captadores de Luz , Tilacoides , Complexos de Proteínas Captadores de Luz/química , Complexo de Proteína do Fotossistema I/química , Complexo de Proteína do Fotossistema II/metabolismo , Proteolipídeos
5.
Sci Rep ; 12(1): 10982, 2022 Jun 29.
Artigo em Inglês | MEDLINE | ID: mdl-35768472

RESUMO

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.


Assuntos
Proteínas de Arabidopsis , Arabidopsis , Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Luz , Oxirredução , Fotossíntese/fisiologia , Complexo de Proteína do Fotossistema I/metabolismo , Complexo de Proteína do Fotossistema II/metabolismo , Proteômica , Tilacoides/metabolismo
6.
Plant Physiol Biochem ; 185: 144-154, 2022 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-35696889

RESUMO

High temperature can induce a substantial adverse effect on plant photosynthesis. This study addressed the impact of moderately high temperature (35 °C) on photosynthetic efficiency and thylakoid membrane organization in Pisum sativum. The Chl a fluorescence curves showed a significant change, indicating a reduction in photosynthetic efficiency when pea plants were exposed to moderate high-temperature stress. The pulse-amplitude modulation measurements showed decreased non-photochemical quenching while the non-regulated energy dissipation increased in treated compared to control and recovery plants. Both parameters indicated that the photosystem (PS)II was prone to temperature stress. The PSI donor side limitation increased in treated and recovery plants compared to control, suggesting the donor side of PSI is hampered in moderate-high temperature. Further, the PSI acceptor side increased in recovery plants compared to control, suggesting that the cyclic electron transport is repressed after temperature treatment but revert back to normal in recovery conditions. Also, the content of photoprotective carotenoid pigments like lutein and xanthophylls increased in temperature-treated leaves. These results indicate the alteration of macro-organization of thylakoid membranes under moderately elevated temperature, whereas supercomplexes restored to the control levels under recovery conditions. Further, the light harvesting complex (LHC)II trimers, and monomers were significantly decreased in temperature-treated plants. Furthermore, the amount of PSII reaction center proteins D1, D2, PsbO, and Cyt b6 was reduced under moderate temperature, whereas the content of LHC proteins of PSI was stable. These observations suggest that moderately high temperature can alter supercomplexes, which leads to change in the pigment-protein organization.


Assuntos
Ervilhas , Tilacoides , Clorofila/metabolismo , Complexos de Proteínas Captadores de Luz/metabolismo , Ervilhas/metabolismo , Fotossíntese , Complexo de Proteína do Fotossistema I/metabolismo , Complexo de Proteína do Fotossistema II/metabolismo , Folhas de Planta/metabolismo , Temperatura , Tilacoides/metabolismo
7.
Biochem J ; 479(13): 1487-1503, 2022 07 15.
Artigo em Inglês | MEDLINE | ID: mdl-35726684

RESUMO

In oxygenic photosynthesis, the cytochrome b6f (cytb6f) complex links the linear electron transfer (LET) reactions occurring at photosystems I and II and generates a transmembrane proton gradient via the Q-cycle. In addition to this central role in LET, cytb6f also participates in a range of processes including cyclic electron transfer (CET), state transitions and photosynthetic control. Many of the regulatory roles of cytb6f are facilitated by auxiliary proteins that differ depending upon the species, yet because of their weak and transient nature the structural details of these interactions remain unknown. An apparent key player in the regulatory balance between LET and CET in cyanobacteria is PetP, a ∼10 kDa protein that is also found in red algae but not in green algae and plants. Here, we used cryogenic electron microscopy to determine the structure of the Synechocystis sp. PCC 6803 cytb6f complex in the presence and absence of PetP. Our structures show that PetP interacts with the cytoplasmic side of cytb6f, displacing the C-terminus of the PetG subunit and shielding the C-terminus of cytochrome b6, which binds the heme cn cofactor that is suggested to mediate CET. The structures also highlight key differences in the mode of plastoquinone binding between cyanobacterial and plant cytb6f complexes, which we suggest may reflect the unique combination of photosynthetic and respiratory electron transfer in cyanobacterial thylakoid membranes. The structure of cytb6f from a model cyanobacterial species amenable to genetic engineering will enhance future site-directed mutagenesis studies of structure-function relationships in this crucial ET complex.


Assuntos
Complexo Citocromos b6f , Synechocystis , Microscopia Crioeletrônica , Complexo Citocromos b6f/química , Complexo Citocromos b6f/metabolismo , Complexo Citocromos b6f/fisiologia , Transporte de Elétrons/fisiologia , Fotossíntese , Synechocystis/metabolismo , Synechocystis/fisiologia , Tilacoides/genética , Tilacoides/metabolismo
8.
Microb Cell Fact ; 21(1): 94, 2022 May 28.
Artigo em Inglês | MEDLINE | ID: mdl-35643504

RESUMO

BACKGROUND: NADPH is used as a reductant in various biosynthetic reactions. Cell-free bio-systems have gained considerable attention owing to their high energy utilization and time efficiency. Efforts have been made to continuously supply reducing power to the reaction mixture in a cyclical manner. The thylakoid membrane (TM) is a promising molecular energy generator, producing NADPH under light. Thus, TM sustainability is of major relevance for its in vitro utilization. RESULTS: Over 70% of TMs prepared from Synechocystis sp. PCC6803 existed in a sealed vesicular structure, with the F1 complex of ATP synthase facing outward (right-side-out), producing NADPH and ATP under light. The NADPH generation activity of TM increased approximately two-fold with the addition of carbonyl cyanide-p-(trifluoromethoxy) phenylhydrazone (FCCP) or removal of the F1 complex using EDTA. Thus, the uncoupling of proton translocation from the electron transport chain or proton leakage through the Fo complex resulted in greater NADPH generation. Biosilicified TM retained more than 80% of its NADPH generation activity after a week at 30°C in the dark. However, activity declined sharply to below 30% after two days in light. The introduction of engineered water-forming NADPH oxidase (Noxm) to keep the electron transport chain of TM working resulted in the improved sustainability of NADPH generation activity in a ratio (Noxm to TM)-dependent manner, which correlated with the decrease of singlet oxygen generation. Removal of reactive oxygen species (ROS) by catalase further highlighted the sustainable NADPH generation activity of up to 80% in two days under light. CONCLUSION: Reducing power generated by light energy has to be consumed for TM sustainability. Otherwise, TM can generate singlet oxygen, causing oxidative damage. Thus, TMs should be kept in the dark when not in use. Although NADPH generation activity by TM can be extended via silica encapsulation, further removal of hydrogen peroxide results in an improvement of TM sustainability. Therefore, as long as ROS formation by TM in light is properly handled, it can be used as a promising source of reducing power for in vitro biochemical reactions.


Assuntos
Synechocystis , Trifosfato de Adenosina , NADP , Prótons , Espécies Reativas de Oxigênio , Oxigênio Singlete , Tilacoides
9.
ACS Appl Mater Interfaces ; 14(19): 22216-22224, 2022 May 18.
Artigo em Inglês | MEDLINE | ID: mdl-35511069

RESUMO

The light-dependent reactions of photosynthesis use light energy to generate photoelectrons traveling through the thylakoid membranes (TMs). Extracting the photoelectrons from the TMs to form bioanodes can have various applications. Most studies focus on modifying the electrode materials to increase the collected photocurrent. Seldom studies have investigated how the orientation of the TMs influences photocurrent collection. In addition, the formation of reactive oxygen species (ROS) during photosynthesis is a challenge for stable photocurrent generation. Here, we enhanced the photoelectron transfer from the TMs to electrodes by depositing expanded thylakoids as planar supported membranes onto an electrode. The high contact area between the external electrodes and TMs per unit mass of thylakoid allows the thylakoid to more effectively transfer electrons to the electrodes, thereby reducing the free electrons available for the ROS generation. We expanded the naturally stacked thylakoids into liposomes through osmotic pressure and dropcasted them onto an Au electrode. The electrochemical impedance measurement showed that the supported membrane bioanode formed by the expanded liposomes had a lower photoelectron transfer resistance. Additionally, we observed that the expanded TM bioanode provided a higher photocurrent and was more durable to air/water interfacial tension. These results suggest that the effective contact between the expanded TM and electrodes can lead to more efficient electron transfer and increase the system robustness. The photo fuel cell (PFC) made by the expanded TM bioanode had a higher open-circuit voltage than the one made by the stacked TM bioanode. Interestingly, we found that PFCs made of high-load TM bioanodes had fast photocurrent decay under continuous operation at high cell voltages. The poor contact of large numbers of TMs with the electrodes at the high-load TM bioanodes could cause more ROS accumulation and therefore decreased the operational stability, supporting the importance of effective contact between TMs and the electrodes.


Assuntos
Elétrons , Tilacoides , Eletrodos , Transporte de Elétrons , Lipossomos/metabolismo , Espécies Reativas de Oxigênio/metabolismo
10.
J Phys Chem Lett ; 13(19): 4263-4271, 2022 May 19.
Artigo em Inglês | MEDLINE | ID: mdl-35522529

RESUMO

We measure the two-dimensional electronic spectra of the LHCII(M)-CP29-CP24 complex in photosystem II (PSII) and provide the first study of the ultrafast excitation energy transfer (EET) processes of an asymmetric and native light-harvesting assembly of the antenna of PSII. With comparisons to LHCII, we observe faster energy equilibrations in the intermediate levels of the LHCII(M)-CP29-CP24 complex at 662 and 670 nm. Notably, the putative "bottleneck" states in LHCII exhibit faster effective dynamics in the LHCII(M)-CP24-CP29 complex, with the average lifetime shortening from 2.5 ps in LHCII to 1.2 ps in the bigger assembly. The observations are supported by high-level structure-based calculations, and the accelerated dynamics can be attributed to the structural change of LHCII(M) in the bigger complex. This study shows that the biological functioning structures of the complexes are important to understand the overall EET dynamics of the PSII supercomplex.


Assuntos
Complexos de Proteínas Captadores de Luz , Complexo de Proteína do Fotossistema II , Transferência de Energia , Complexos de Proteínas Captadores de Luz/química , Complexo de Proteína do Fotossistema II/metabolismo , Plantas/metabolismo , Tilacoides
11.
Nat Commun ; 13(1): 2505, 2022 05 06.
Artigo em Inglês | MEDLINE | ID: mdl-35523970

RESUMO

In the light reaction of plant photosynthesis, modulation of electron transport chain reactions is important to maintain the efficiency of photosynthesis under a broad range of light intensities. VCCN1 was recently identified as a voltage-gated chloride channel residing in the thylakoid membrane, where it plays a key role in photoreaction tuning to avoid the generation of reactive oxygen species (ROS). Here, we present the cryo-EM structures of Malus domestica VCCN1 (MdVCCN1) in nanodiscs and detergent at 2.7 Å and 3.0 Å resolutions, respectively, and the structure-based electrophysiological analyses. VCCN1 structurally resembles its animal homolog, bestrophin, a Ca2+-gated anion channel. However, unlike bestrophin channels, VCCN1 lacks the Ca2+-binding motif but instead contains an N-terminal charged helix that is anchored to the lipid membrane through an additional amphipathic helix. Electrophysiological experiments demonstrate that these structural elements are essential for the channel activity, thus revealing the distinct activation mechanism of VCCN1.


Assuntos
Canais de Cloreto , Tilacoides , Animais , Bestrofinas/metabolismo , Canais de Cloreto/metabolismo , Microscopia Crioeletrônica , Fotossíntese/fisiologia , Tilacoides/metabolismo
12.
Plant Physiol ; 189(3): 1204-1219, 2022 06 27.
Artigo em Inglês | MEDLINE | ID: mdl-35512089

RESUMO

Photosynthetic light-harvesting antennae are pigment-binding proteins that perform one of the most fundamental tasks on Earth, capturing light and transferring energy that enables life in our biosphere. Adaptation to different light environments led to the evolution of an astonishing diversity of light-harvesting systems. At the same time, several strategies have been developed to optimize the light energy input into photosynthetic membranes in response to fluctuating conditions. The basic feature of these prompt responses is the dynamic nature of antenna complexes, whose function readily adapts to the light available. High-resolution microscopy and spectroscopic studies on membrane dynamics demonstrate the crosstalk between antennae and other thylakoid membrane components. With the increased understanding of light-harvesting mechanisms and their regulation, efforts are focusing on the development of sustainable processes for effective conversion of sunlight into functional bio-products. The major challenge in this approach lies in the application of fundamental discoveries in light-harvesting systems for the improvement of plant or algal photosynthesis. Here, we underline some of the latest fundamental discoveries on the molecular mechanisms and regulation of light harvesting that can potentially be exploited for the optimization of photosynthesis.


Assuntos
Complexos de Proteínas Captadores de Luz , Fotossíntese , Adaptação Fisiológica , Complexos de Proteínas Captadores de Luz/metabolismo , Fotossíntese/fisiologia , Plantas/metabolismo , Tilacoides/metabolismo
13.
Commun Biol ; 5(1): 460, 2022 05 13.
Artigo em Inglês | MEDLINE | ID: mdl-35562408

RESUMO

Different intensities of high temperatures affect the growth of photosynthetic cells in nature. To elucidate the underlying mechanisms, we cultivated the unicellular green alga Chlamydomonas reinhardtii under highly controlled photobioreactor conditions and revealed systems-wide shared and unique responses to 24-hour moderate (35°C) and acute (40°C) high temperatures and subsequent recovery at 25°C. We identified previously overlooked unique elements in response to moderate high temperature. Heat at 35°C transiently arrested the cell cycle followed by partial synchronization, up-regulated transcripts/proteins involved in gluconeogenesis/glyoxylate-cycle for carbon uptake and promoted growth. But 40°C disrupted cell division and growth. Both high temperatures induced photoprotection, while 40°C distorted thylakoid/pyrenoid ultrastructure, affected the carbon concentrating mechanism, and decreased photosynthetic efficiency. We demonstrated increased transcript/protein correlation during both heat treatments and hypothesize reduced post-transcriptional regulation during heat may help efficiently coordinate thermotolerance mechanisms. During recovery after both heat treatments, especially 40°C, transcripts/proteins related to DNA synthesis increased while those involved in photosynthetic light reactions decreased. We propose down-regulating photosynthetic light reactions during DNA replication benefits cell cycle resumption by reducing ROS production. Our results provide potential targets to increase thermotolerance in algae and crops.


Assuntos
Chlamydomonas reinhardtii , Carbono/metabolismo , Chlamydomonas reinhardtii/genética , Temperatura Alta , Plantas/metabolismo , Temperatura , Tilacoides/metabolismo
14.
Int J Mol Sci ; 23(9)2022 Apr 20.
Artigo em Inglês | MEDLINE | ID: mdl-35562922

RESUMO

Reversible phosphorylation of photosystem II light harvesting complexes (LHCII) is a well-established protective mechanism enabling efficient response to changing light conditions. However, changes in LHCII phosphorylation were also observed in response to abiotic stress regardless of photoperiod. This study aimed to investigate the impact of dark-chilling on LHCII phosphorylation pattern in chilling-tolerant Arabidopsis thaliana and to check whether the disturbed LHCII phosphorylation process will impact the response of Arabidopsis to the dark-chilling conditions. We analyzed the pattern of LHCII phosphorylation, the organization of chlorophyll-protein complexes, and the level of chilling tolerance by combining biochemical and spectroscopy techniques under dark-chilling and dark conditions in Arabidopsis mutants with disrupted LHCII phosphorylation. Our results show that during dark-chilling, LHCII phosphorylation decreased in all examined plant lines and that no significant differences in dark-chilling response were registered in tested lines. Interestingly, after 24 h of darkness, a high increase in LHCII phosphorylation was observed, co-occurring with a significant FV/FM parameter decrease. The highest drop of FV/FM was detected in the stn7-1 line-mutant, where the LHCII is not phosphorylated, due to the lack of STN7 kinase. Our results imply that STN7 kinase activity is important for mitigating the adverse effects of prolonged darkness.


Assuntos
Proteínas de Arabidopsis , Arabidopsis , Arabidopsis/metabolismo , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Escuridão , Luz , Complexos de Proteínas Captadores de Luz/genética , Complexos de Proteínas Captadores de Luz/metabolismo , Fosforilação , Complexo de Proteína do Fotossistema II/genética , Complexo de Proteína do Fotossistema II/metabolismo , Proteínas Serina-Treonina Quinases , Tilacoides/metabolismo
15.
Toxins (Basel) ; 14(5)2022 04 27.
Artigo em Inglês | MEDLINE | ID: mdl-35622553

RESUMO

A survey on the occurrence of ochratoxin A (OTA) and sterigmatocystin (STC) in grated cheese products obtained from hard grana-type cheeses was carried out, where 107 grated products were collected in retail outlets and analysed. OTA and STC were found in 48.6% and 94.4% of the samples, in a range from <LOD to 25.05 µg kg-1 and from <LOD to 6.87 µg kg-1, respectively. STC was detected in all the OTA-contaminated samples. The OTA and STC occurrence in cheese is due to environmental contamination during ripening, leading to fungal growth and mycotoxin production on the cheese surface. This statement was confirmed by analysing the surface of 16 hard grana cheese rinds, which resulted contaminated by both OTA and STC, with concentration ranging from 3 to 370 µg kg-1. This finding demonstrates that rind inclusion increases the mycotoxin concentration in grated cheeses. The mycotoxin level significantly decreased from the surface (0-1.5 mm) to inner parts of cheese rinds (1.5-4.5 mm). Industrial wheel-cleaning techniques can represent a useful treatment to reduce both toxins in grated cheese products.


Assuntos
Queijo , Ocratoxinas , Queijo/microbiologia , Ocratoxinas/análise , Esterigmatocistina/análise , Tilacoides/química
17.
J Exp Bot ; 73(9): 2721-2734, 2022 05 13.
Artigo em Inglês | MEDLINE | ID: mdl-35560194

RESUMO

The appearance of oxygenic photosynthesis in cyanobacteria is a major event in evolution. It had an irreversible impact on the Earth, promoting the Great Oxygenation Event (GOE) ~2.4 billion years ago. Ancient cyanobacteria predating the GOE were Gloeobacter-type cells lacking thylakoids, which hosted photosystems in their cytoplasmic membrane. The driver of the GOE was proposed to be the transition from unicellular to filamentous cyanobacteria. However, the appearance of thylakoids expanded the photosynthetic surface to such an extent that it introduced a multiplier effect, which would be more coherent with an impact on the atmosphere. Primitive thylakoids self-organize as concentric parietal uninterrupted multilayers. There is no robust evidence for an origin of thylakoids via a vesicular-based scenario. This review reports studies supporting that hexagonal II-forming glucolipids and galactolipids at the periphery of the cytosolic membrane could be turned, within nanoseconds and without any external source of energy, into membrane multilayers. Comparison of lipid biosynthetic pathways shows that ancient cyanobacteria contained only one anionic lamellar-forming lipid, phosphatidylglycerol. The acquisition of sulfoquinovosyldiacylglycerol biosynthesis correlates with thylakoid emergence, possibly enabling sufficient provision of anionic lipids to trigger a hexagonal II-to-lamellar phase transition. With this non-vesicular lipid-phase transition, a framework is also available to re-examine the role of companion proteins in thylakoid biogenesis.


Assuntos
Cianobactérias , Tilacoides , Cianobactérias/metabolismo , Galactolipídeos/metabolismo , Fotossíntese , Tilacoides/metabolismo
18.
J Exp Bot ; 73(9): 2735-2750, 2022 05 13.
Artigo em Inglês | MEDLINE | ID: mdl-35560200

RESUMO

In the thylakoid membrane of cyanobacteria and chloroplasts, many proteins involved in photosynthesis are associated with or integrated into the fluid bilayer matrix formed by four unique glycerolipid classes, monogalactosyldiacylglycerol, digalactosyldiacylglycerol, sulfoquinovosyldiacylglycerol, and phosphatidylglycerol. Biochemical and molecular genetic studies have revealed that these glycerolipids play essential roles not only in the formation of thylakoid lipid bilayers but also in the assembly and functions of photosynthetic complexes. Moreover, considerable advances in structural biology have identified a number of lipid molecules within the photosynthetic complexes such as PSI and PSII. These data have provided important insights into the association of lipids with protein subunits in photosynthetic complexes and the distribution of lipids in the thylakoid membrane. Here, we summarize recent high-resolution observations of lipid molecules in the structures of photosynthetic complexes from plants, algae, and cyanobacteria, and evaluate the distribution of lipids among photosynthetic protein complexes and thylakoid lipid bilayers. By integrating the structural information into the findings from biochemical and molecular genetic studies, we highlight the conserved and differentiated roles of lipids in the assembly and functions of photosynthetic complexes among plants, algae, and cyanobacteria.


Assuntos
Cianobactérias , Complexo de Proteínas do Centro de Reação Fotossintética , Cianobactérias/metabolismo , Bicamadas Lipídicas/metabolismo , Fotossíntese/genética , Complexo de Proteínas do Centro de Reação Fotossintética/metabolismo , Tilacoides/metabolismo
19.
J Exp Bot ; 73(9): 2751-2764, 2022 05 13.
Artigo em Inglês | MEDLINE | ID: mdl-35560204

RESUMO

Fibrillins (FBNs) are a family of genes in cyanobacteria, algae, and plants. The proteins they encode possess a lipid-binding motif, exist in various types of plastids, and are associated with lipid bodies called plastoglobules, implicating them in lipid metabolism. FBNs present in the thylakoid and stroma are involved in the storage, transport, and synthesis of lipid molecules for photoprotective functions against high-light stress. In this review, the diversity of subplastid locations in the evolution of FBNs, regulation of FBNs expression by various stresses, and the role of FBNs in plastid lipid metabolism are comprehensively summarized and directions for future research are discussed.


Assuntos
Plastídeos , Tilacoides , Fibrilinas/metabolismo , Lipídeos/análise , Plantas/genética , Plastídeos/metabolismo , Tilacoides/metabolismo
20.
Int J Mol Sci ; 23(7)2022 Mar 26.
Artigo em Inglês | MEDLINE | ID: mdl-35408985

RESUMO

Most C4 plants that naturally occur in tropical or subtropical climates, in high light environments, had to evolve a series of adaptations of photosynthesis that allowed them to grow under these conditions. In this review, we summarize mechanisms that ensure the balancing of energy distribution, counteract photoinhibition, and allow the dissipation of excess light energy. They secure effective electron transport in light reactions of photosynthesis, which will lead to the production of NADPH and ATP. Furthermore, a higher content of the cyclic electron transport components and an increase in ATP production are observed, which is necessary for the metabolism of C4 for effective assimilation of CO2. Most of the data are provided by studies of the genus Flaveria, where species belonging to different metabolic subtypes and intermediate forms between C3 and C4 are present. All described mechanisms that function in mesophyll and bundle sheath chloroplasts, into which photosynthetic reactions are divided, may differ in metabolic subtypes as a result of the different organization of thylakoid membranes, as well as the different demand for ATP and NADPH. This indicates that C4 plants have plasticity in the utilization of pathways in which efficient use and dissipation of excitation energy are realized.


Assuntos
Fotossíntese , Tilacoides , Trifosfato de Adenosina/metabolismo , Dióxido de Carbono/metabolismo , Luz , NADP/metabolismo , Folhas de Planta/metabolismo , Plantas/metabolismo , Tilacoides/metabolismo
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