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1.
Plant Physiol ; 187(2): 931-946, 2021 Oct 05.
Artigo em Inglês | MEDLINE | ID: mdl-34608952

RESUMO

Light is the ultimate source of energy for photosynthetic organisms, but respiration is fundamental for supporting metabolism during the night or in heterotrophic tissues. In this work, we isolated Physcomitrella (Physcomitrium patens) plants with altered respiration by inactivating Complex I (CI) of the mitochondrial electron transport chain by independently targeting on two essential subunits. Inactivation of CI caused a strong growth impairment even in fully autotrophic conditions in tissues where all cells are photosynthetically active, demonstrating that respiration is essential for photosynthesis. CI mutants showed alterations in the stoichiometry of respiratory complexes while the composition of photosynthetic apparatus was substantially unaffected. CI mutants showed altered photosynthesis with high activity of both Photosystems I and II, likely the result of high chloroplast ATPase activity that led to smaller ΔpH formation across thylakoid membranes, decreasing photosynthetic control on cytochrome b6f in CI mutants. These results demonstrate that alteration of respiratory activity directly impacts photosynthesis in P. patens and that metabolic interaction between organelles is essential in their ability to use light energy for growth.

2.
Cells ; 10(9)2021 09 09.
Artigo em Inglês | MEDLINE | ID: mdl-34572012

RESUMO

In Part I, by using 31P-NMR spectroscopy, we have shown that isolated granum and stroma thylakoid membranes (TMs), in addition to the bilayer, display two isotropic phases and an inverted hexagonal (HII) phase; saturation transfer experiments and selective effects of lipase and thermal treatments have shown that these phases arise from distinct, yet interconnectable structural entities. To obtain information on the functional roles and origin of the different lipid phases, here we performed spectroscopic measurements and inspected the ultrastructure of these TM fragments. Circular dichroism, 77 K fluorescence emission spectroscopy, and variable chlorophyll-a fluorescence measurements revealed only minor lipase- or thermally induced changes in the photosynthetic machinery. Electrochromic absorbance transients showed that the TM fragments were re-sealed, and the vesicles largely retained their impermeabilities after lipase treatments-in line with the low susceptibility of the bilayer against the same treatment, as reflected by our 31P-NMR spectroscopy. Signatures of HII-phase could not be discerned with small-angle X-ray scattering-but traces of HII structures, without long-range order, were found by freeze-fracture electron microscopy (FF-EM) and cryo-electron tomography (CET). EM and CET images also revealed the presence of small vesicles and fusion of membrane particles, which might account for one of the isotropic phases. Interaction of VDE (violaxanthin de-epoxidase, detected by Western blot technique in both membrane fragments) with TM lipids might account for the other isotropic phase. In general, non-bilayer lipids are proposed to play role in the self-assembly of the highly organized yet dynamic TM network in chloroplasts.


Assuntos
Lipídeos/genética , Tilacoides/genética , Dicroísmo Circular/métodos , Espectroscopia de Ressonância Magnética/métodos , Microscopia Eletrônica/métodos , Fotossíntese/genética
3.
Physiol Plant ; 173(3): 805-817, 2021 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-34171145

RESUMO

Eukaryotic algae are photosynthetic organisms capable of exploiting sunlight to fix carbon dioxide into biomass with highly variable genetic and metabolic features. Information on algae metabolism from different species is inhomogeneous and, while green algae are, in general, more characterized, information on red algae is relatively scarce despite their relevant position in eukaryotic algae diversity. Within red algae, the best-known species are extremophiles or multicellular, while information on mesophilic unicellular organisms is still lacunose. Here, we investigate the photosynthetic properties of a recently isolated seawater unicellular mesophilic red alga, Dixoniella giordanoi. Upon exposure to different illuminations, D. giordanoi shows the ability to acclimate, modulate chlorophyll content, and re-organize thylakoid membranes. Phycobilisome content is also largely regulated, leading to almost complete disassembly of this antenna system in cells grown under intense illumination. Despite the absence of a light-induced xanthophyll cycle, cells accumulate zeaxanthin upon prolonged exposure to strong light, likely contributing to photoprotection. D. giordanoi cells show the ability to perform cyclic electron transport that is enhanced under strong illumination, likely contributing to the protection of Photosystem I from over-reduction and enabling cells to survive PSII photoinhibition without negative impact on growth.


Assuntos
Complexo de Proteína do Fotossistema II , Rodófitas , Aclimatação , Clorofila , Luz , Fotossíntese , Complexo de Proteína do Fotossistema II/metabolismo , Rodófitas/metabolismo
4.
Nat Commun ; 12(1): 679, 2021 01 29.
Artigo em Inglês | MEDLINE | ID: mdl-33514722

RESUMO

Diverse algae of the red lineage possess chlorophyll a-binding proteins termed LHCR, comprising the PSI light-harvesting system, which represent an ancient antenna form that evolved in red algae and was acquired through secondary endosymbiosis. However, the function and regulation of LHCR complexes remain obscure. Here we describe isolation of a Nannochloropsis oceanica LHCR mutant, named hlr1, which exhibits a greater tolerance to high-light (HL) stress compared to the wild type. We show that increased tolerance to HL of the mutant can be attributed to alterations in PSI, making it less prone to ROS production, thereby limiting oxidative damage and favoring growth in HL. HLR1 deficiency attenuates PSI light-harvesting capacity and growth of the mutant under light-limiting conditions. We conclude that HLR1, a member of a conserved and broadly distributed clade of LHCR proteins, plays a pivotal role in a dynamic balancing act between photoprotection and efficient light harvesting for photosynthesis.


Assuntos
Adaptação Fisiológica/genética , Proteínas de Ligação à Clorofila/metabolismo , Luz/efeitos adversos , Complexo de Proteína do Fotossistema I/metabolismo , Estramenópilas/fisiologia , Adaptação Fisiológica/efeitos da radiação , Clorofila A/metabolismo , Proteínas de Ligação à Clorofila/genética , Proteínas de Ligação à Clorofila/isolamento & purificação , Mutação , Fotossíntese/genética , Fotossíntese/efeitos da radiação , Complexo de Proteína do Fotossistema I/genética , Estramenópilas/efeitos da radiação
5.
New Phytol ; 230(3): 1258-1272, 2021 05.
Artigo em Inglês | MEDLINE | ID: mdl-33421132

RESUMO

CRISPR-Cas9 has proven to be highly valuable for genome editing in plants, including the model plant Physcomitrium patens. However, the fact that most of the editing events produced using the native Cas9 nuclease correspond to small insertions and deletions is a limitation. CRISPR-Cas9 base editors enable targeted mutation of single nucleotides in eukaryotic genomes and therefore overcome this limitation. Here, we report two programmable base-editing systems to induce precise cytosine or adenine conversions in P. patens. Using cytosine or adenine base editors, site-specific single-base mutations can be achieved with an efficiency up to 55%, without off-target mutations. Using the APT gene as a reporter of editing, we could show that both base editors can be used in simplex or multiplex, allowing for the production of protein variants with multiple amino-acid changes. Finally, we set up a co-editing selection system, named selecting modification of APRT to report gene targeting (SMART), allowing up to 90% efficiency site-specific base editing in P. patens. These two base editors will facilitate gene functional analysis in P. patens, allowing for site-specific editing of a given base through single sgRNA base editing or for in planta evolution of a given gene through the production of randomly mutagenised variants using multiple sgRNA base editing.


Assuntos
Bryopsida , Bryopsida/genética , Sistemas CRISPR-Cas/genética , Repetições Palindrômicas Curtas Agrupadas e Regularmente Espaçadas , Edição de Genes , Mutagênese Sítio-Dirigida
6.
Biophys J ; 120(2): 270-283, 2021 01 19.
Artigo em Inglês | MEDLINE | ID: mdl-33285116

RESUMO

Photosynthetic light-harvesting complexes (LHCs) of higher plants, moss, and green algae can undergo dynamic conformational transitions, which have been correlated to their ability to adapt to fluctuations in the light environment. Herein, we demonstrate the application of solid-state NMR spectroscopy on native, heterogeneous thylakoid membranes of Chlamydomonas reinhardtii (Cr) and on Cr light-harvesting complex II (LHCII) in thylakoid lipid bilayers to detect LHCII conformational dynamics in its native membrane environment. We show that membrane-reconstituted LHCII contains selective sites that undergo fast, large-amplitude motions, including the phytol tails of two chlorophylls. Protein plasticity is also observed in the N-terminal stromal loop and in protein fragments facing the lumen, involving sites that stabilize the xanthophyll-cycle carotenoid violaxanthin and the two luteins. The results report on the intrinsic flexibility of LHCII pigment-protein complexes in a membrane environment, revealing putative sites for conformational switching. In thylakoid membranes, fast dynamics of protein and pigment sites is significantly reduced, which suggests that in their native organelle membranes, LHCII complexes are locked in specific conformational states.


Assuntos
Chlamydomonas reinhardtii , Tilacoides , Chlamydomonas reinhardtii/metabolismo , Clorofila , Complexos de Proteínas Captadores de Luz/metabolismo , Fotossíntese , Complexo de Proteína do Fotossistema II/metabolismo , Tilacoides/metabolismo
7.
Bioresour Technol ; 320(Pt B): 124379, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-33189041

RESUMO

Poly-ß-hydroxybutyrate (PHB) is a biodegradable biopolymer that may replace fossil-based plastics reducing its negative environmental impact. One highly sustainable strategy to produce these biopolymers is the exploitation of photosynthetic microorganisms that use sunlight and CO2 to produce biomass and subsequently, PHB. Exploring environmental biological diversity is a powerful tool to find resilient microorganisms potentially exploitable to produce bioproducts. In this work, a cyanobacterium (Synechocystis sp.) isolated from a contaminated area close to an important industrial complex was shown to produce PHB under different culture conditions. Carbon, nutrients supply and light intensity impact on biomass and PHB productivity were assessed, showing that the highest yield of PHB achieved was 241 mg L-1 (31%dcw) under high light intensity. Remarkably this condition not only stimulated PHB accumulation by 70% compared to other conditions tested but also high cellular duplication rate, maximizing the potential of this strain for PHB production.


Assuntos
Synechocystis , Carbono , Hidroxibutiratos , Poliésteres
8.
J Exp Bot ; 71(18): 5538-5548, 2020 09 19.
Artigo em Inglês | MEDLINE | ID: mdl-32497206

RESUMO

Alternative electron pathways contribute to regulation of photosynthetic light reactions to adjust to metabolic demands in dynamic environments. The chloroplast NADH dehydrogenase-like (NDH) complex mediates the cyclic electron transport pathway around PSI in different cyanobacteria, algae, and plant species, but it is not fully conserved in all photosynthetic organisms. In order to assess how the physiological role of this complex changed during plant evolution, we isolated Physcomitrella patens lines knocked out for the NDHM gene that encodes a subunit fundamental for the activity of the complex. ndhm knockout mosses indicated high PSI acceptor side limitation upon abrupt changes in illumination. In P. patens, pseudo-cyclic electron transport mediated by flavodiiron proteins (FLVs) was also shown to prevent PSI over-reduction in plants exposed to light fluctuations. flva ndhm double knockout mosses had altered photosynthetic performance and growth defects under fluctuating light compared with the wild type and single knockout mutants. The results showed that while the contribution of NDH to electron transport is minor compared with FLV, NDH still participates in modulating photosynthetic activity, and it is critical to avoid PSI photoinhibition, especially when FLVs are inactive. The functional overlap between NDH- and FLV-dependent electron transport supports PSI activity and prevents its photoinhibition under light variations.


Assuntos
Bryopsida , Bryopsida/genética , Bryopsida/metabolismo , Cloroplastos/metabolismo , Transporte de Elétrons , Luz , NADH Desidrogenase/genética , NADH Desidrogenase/metabolismo , Fotossíntese , Complexo de Proteína do Fotossistema I/metabolismo
9.
New Phytol ; 228(4): 1316-1326, 2020 11.
Artigo em Inglês | MEDLINE | ID: mdl-32367526

RESUMO

Photosynthetic electron transport is regulated by cyclic and pseudocyclic electron flow (CEF and PCEF) to maintain the balance between light availability and metabolic demands. CEF transfers electrons from photosystem I to the plastoquinone pool with two mechanisms, dependent either on PGR5/PGRL1 or on the type I NADH dehydrogenase-like (NDH) complex. PCEF uses electrons from photosystem I to reduce oxygen and in many groups of photosynthetic organisms, but remarkably not in angiosperms, it is catalyzed by flavodiiron proteins (FLVs). In this study, Physcomitrella patens plants depleted in PGRL1, NDH and FLVs in different combinations were generated and characterized, showing that all these mechanisms are active in this moss. Surprisingly, in contrast to flowering plants, Physcomitrella patens can cope with the simultaneous inactivation of PGR5- and NDH-dependent CEF but, when FLVs are also depleted, plants show strong growth reduction and photosynthetic activity is drastically reduced. The results demonstrate that mechanisms for modulation of photosynthetic electron transport have large functional overlap but are together indispensable to protect photosystem I from damage and they are an essential component for photosynthesis in any light regime.


Assuntos
Bryopsida , Complexo de Proteína do Fotossistema I , Bryopsida/metabolismo , Transporte de Elétrons , Luz , Fotossíntese , Complexo de Proteína do Fotossistema I/metabolismo , Desenvolvimento Vegetal
10.
Sci Rep ; 10(1): 6770, 2020 04 21.
Artigo em Inglês | MEDLINE | ID: mdl-32317747

RESUMO

Although light is essential for photosynthesis, when in excess, it may damage the photosynthetic apparatus, leading to a phenomenon known as photoinhibition. Photoinhibition was thought as a light-induced damage to photosystem II; however, it is now clear that even photosystem I may become very vulnerable to light. One main characteristic of light induced damage to photosystem II (PSII) is the increased turnover of the reaction center protein, D1: when rate of degradation exceeds the rate of synthesis, loss of PSII activity is observed. With respect to photosystem I (PSI), an excess of electrons, instead of an excess of light, may be very dangerous. Plants possess a number of mechanisms able to prevent, or limit, such damages by safe thermal dissipation of light energy (non-photochemical quenching, NPQ), slowing-down of electron transfer through the intersystem transport chain (photosynthesis-control, PSC) in co-operation with the Proton Gradient Regulation (PGR) proteins, PGR5 and PGRL1, collectively called as short-term photoprotection mechanisms, and the redistribution of light between photosystems, called state transitions (responsible of fluorescence quenching at PSII, qT), is superimposed to these short term photoprotective mechanisms. In this manuscript we have generated a number of higher order mutants by crossing genotypes carrying defects in each of the short-term photoprotection mechanisms, with the final aim to obtain a direct comparison of their role and efficiency in photoprotection. We found that mutants carrying a defect in the ΔpH-dependent photosynthesis-control are characterized by photoinhibition of both photosystems, irrespectively of whether PSBS-dependent NPQ or state transitions defects were present or not in the same individual, demonstrating the primary role of PSC in photoprotection. Moreover, mutants with a limited capability to develop a strong PSBS-dependent NPQ, were characterized by a high turnover of the D1 protein and high values of Y(NO), which might reflect energy quenching processes occurring within the PSII reaction center.


Assuntos
Proteínas de Arabidopsis/genética , Proteínas de Membrana/genética , Complexo de Proteínas do Centro de Reação Fotossintética/genética , Complexo de Proteína do Fotossistema I/genética , Complexo de Proteína do Fotossistema II/genética , Arabidopsis/genética , Arabidopsis/fisiologia , Genótipo , Concentração de Íons de Hidrogênio , Luz , Fotossíntese/genética , Fotossíntese/efeitos da radiação , Complexo de Proteína do Fotossistema I/efeitos da radiação , Complexo de Proteína do Fotossistema II/efeitos da radiação
11.
Front Plant Sci ; 11: 182, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32210991

RESUMO

Oxygenic photosynthetic microorganisms are a focal point of research in the context of human space exploration. As part of the bioregenerative life-support systems, they could have a key role in the production of breathable O2, edible biomasses and in the regeneration of CO2 rich-atmospheres and wastewaters produced by astronauts. The test of the organism's response to simulated physico-chemical parameters of planetary bodies could also provide important information about their habitability potential. It is believed that the success of future planetary and space missions will require innovative technologies, developed on the base of preliminary experiments in custom-made laboratory facilities. In this context, simulation chambers will play a pivotal role by allowing the growth of the microorganisms under controlled conditions and the evaluation in real-time of their biomass productivity and impact on atmosphere composition. We here present a system capable of addressing these requirements with high replicability and low costs. The setup is composed by three main parts: 1) a Star Light Simulator, able to generate different light intensities and spectra, including those of non-solar stars; 2) an Atmosphere Simulator Chamber where cultures of photosynthetic microorganisms can be exposed to different gas compositions; 3) a reflectivity detection system to measure from remote the Normalized Difference Vegetation Indexes (NDVI). Such a setup allows us to monitor photosynthetic microorganism's growth and gas exchange performances under selected conditions of light quality and intensity, temperature, pressure, and atmospheres simulating non-terrestrial environments. All parameters are detected by remote sensing techniques, thus without interfering with the experiments and altering the environmental conditions set. We validated the setup by growing cyanobacteria liquid cultures under different light intensities of solar illumination, collecting data on their growth rate, photosynthetic activity, and gas exchange capacity. We utilized the reflectivity detection system to measure the reflection spectra of the growing cultures, obtaining their relative NDVI that was shown to correlate with optical density, chlorophyll content, and dry weight, demonstrating the potential application of this index as a proxy of growth.

12.
Plant Cell Physiol ; 61(1): 41-52, 2020 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-31511895

RESUMO

In nature, photosynthetic organisms are exposed to highly dynamic environmental conditions where the excitation energy and electron flow in the photosynthetic apparatus need to be continuously modulated. Fluctuations in incident light are particularly challenging because they drive oversaturation of photosynthesis with consequent oxidative stress and photoinhibition. Plants and algae have evolved several mechanisms to modulate their photosynthetic machinery to cope with light dynamics, such as thermal dissipation of excited chlorophyll states (non-photochemical quenching, NPQ) and regulation of electron transport. The regulatory mechanisms involved in the response to light dynamics have adapted during evolution, and exploring biodiversity is a valuable strategy for expanding our understanding of their biological roles. In this work, we investigated the response to fluctuating light in Nannochloropsis gaditana, a eukaryotic microalga of the phylum Heterokonta originating from a secondary endosymbiotic event. Nannochloropsis gaditana is negatively affected by light fluctuations, leading to large reductions in growth and photosynthetic electron transport. Exposure to light fluctuations specifically damages photosystem I, likely because of the ineffective regulation of electron transport in this species. The role of NPQ, also assessed using a mutant strain specifically depleted of this response, was instead found to be minor, especially in responding to the fastest light fluctuations.


Assuntos
Luz , Fotossíntese/fisiologia , Estramenópilas/metabolismo , Simbiose/fisiologia , Biodiversidade , Transporte de Elétrons/fisiologia , Estresse Oxidativo , Complexo de Proteína do Fotossistema I/metabolismo , Complexo de Proteína do Fotossistema I/efeitos da radiação , Plantas/metabolismo , Estramenópilas/crescimento & desenvolvimento , Estramenópilas/efeitos da radiação
13.
Biochem J ; 476(17): 2487-2498, 2019 09 13.
Artigo em Inglês | MEDLINE | ID: mdl-31519856

RESUMO

The regulation of photosynthesis is crucial to efficiently support the assimilation of carbon dioxide and to prevent photodamage. One key regulatory mechanism is the pseudo-cyclic electron flow (PCEF) mediated by class-C flavodiiron proteins (FLVs). These enzymes use electrons coming from Photosystem I (PSI) to reduce oxygen to water, preventing over-reduction in the acceptor side of PSI. FLVs are widely distributed among organisms performing oxygenic photosynthesis and they have been shown to be fundamental in many different conditions such as fluctuating light, sulfur deprivation and plant submersion. Moreover, since FLVs reduce oxygen they can help controlling the redox status of the cell and maintaining the microoxic environment essential for processes such as nitrogen fixation in cyanobacteria. Despite these important roles identified in various species, the genes encoding for FLV proteins have been lost in angiosperms where their activity could have been at least partially compensated by a more efficient cyclic electron flow (CEF). The present work reviews the information emerged on FLV function, analyzing recent structural data that suggest FLV could be regulated through a conformational change.


Assuntos
Proteínas de Bactérias/metabolismo , Cianobactérias/metabolismo , Fixação de Nitrogênio/fisiologia , Oxigênio/metabolismo , Fotossíntese/fisiologia , Complexo de Proteína do Fotossistema I/metabolismo , Proteínas de Bactérias/genética , Cianobactérias/genética , Oxirredução , Complexo de Proteína do Fotossistema I/genética
14.
Plant Physiol ; 180(3): 1582-1597, 2019 07.
Artigo em Inglês | MEDLINE | ID: mdl-31061101

RESUMO

In all eukaryotes, protein phosphorylation is a key regulatory mechanism in several cellular processes, including the acclimation of photosynthesis to environmental cues. Despite being a well-conserved regulatory mechanism in the chloroplasts of land plants, distinct differences in thylakoid protein phosphorylation patterns have emerged from studies on species of different phylogenetic groups. Here, we analyzed thylakoid protein phosphorylation in the moss Physcomitrella patens, assessing the thylakoid phospho-protein profile and dynamics in response to changes in white light intensity. Compared with Arabidopsis (Arabidopsis thaliana), parallel characterization of wild-type P patens and the knockout mutant stn8 (depleted in SER/THR PROTEIN KINASE8 [STN8]) disclosed a moss-specific pattern of thylakoid protein phosphorylation, both with respect to specific targets and to their dynamic phosphorylation in response to environmental cues. Unlike vascular plants, (1) phosphorylation of the PSII protein D1 in P patens was negligible under all light conditions, (2) phosphorylation of the PSII core subunits CP43 and D2 showed only minor changes upon fluctuations in light intensity, and (3) absence of STN8 completely abolished all PSII core protein phosphorylation. Further, we detected light-induced phosphorylation in the minor light harvesting complex (LHC) antenna protein LHCB6, which was dependent on STN8 kinase activity, and found specific phosphorylations on LHCB3. Data presented here provide further insights into the appearance and physiological role of thylakoid protein phosphorylation during evolution of oxygenic photosynthetic organisms and their colonization of land.


Assuntos
Bryopsida/metabolismo , Cloroplastos/metabolismo , Proteínas de Plantas/metabolismo , Proteínas Serina-Treonina Quinases/metabolismo , Tilacoides/metabolismo , Arabidopsis/genética , Arabidopsis/metabolismo , Bryopsida/genética , Cloroplastos/genética , Cloroplastos/ultraestrutura , Cinética , Luz , Complexos de Proteínas Captadores de Luz/genética , Complexos de Proteínas Captadores de Luz/metabolismo , Microscopia Eletrônica de Transmissão , Mutação , Fosforilação , Fotossíntese/genética , Fotossíntese/efeitos da radiação , Complexo de Proteína do Fotossistema II/genética , Complexo de Proteína do Fotossistema II/metabolismo , Proteínas de Plantas/genética , Proteínas Quinases/genética , Proteínas Quinases/metabolismo , Proteínas Serina-Treonina Quinases/genética , Tilacoides/genética , Tilacoides/ultraestrutura
15.
Planta ; 249(4): 1217-1228, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-30607502

RESUMO

MAIN CONCLUSION: Investigation of photosynthesis regulation in different plant groups exposed to variable conditions showed that all species have similar photosynthetic electron transport modulation while excess energy dissipation is species specific. Photosynthesis is regulated in response to dynamic environmental conditions to satisfy plant metabolic demands while also avoiding possible over-excitation of the electron transport chain and the generation of harmful reactive oxygen species. Photosynthetic organisms evolved several mechanisms to modulate light harvesting and electron transport efficiency to respond to conditions changing at different timescales, going from fast sun flecks to slow seasonal variations. These regulatory mechanisms changed during evolution of photosynthetic organisms, also adapting to various ecological niches, making the investigation of plant biodiversity highly valuable to uncover conserved traits and plasticity of photosynthetic regulation and complement studies on model species. In this work, a set of plants belonging to different genera of angiosperms, gymnosperms, ferns and lycophytes were investigated by monitoring their photosynthetic parameters in different seasons looking for common trends and differences. In all plants, analysed photosynthetic electron transport rate was found to be modulated by growth light intensity, ensuring a balance between available energy and photochemical capacity. Growth light also influenced the threshold where heat dissipation of excitation energy, a mechanism called non-photochemical quenching (NPQ), was activated. On the contrary, NPQ amplitude did not correlate with light intensity experienced by the plants but was a species-specific feature. The zeaxanthin-dependent component of NPQ, qZ, was found to be the most variable in different plants and its modulation influenced the intensity and the kinetic properties of the response.


Assuntos
Biodiversidade , Fotossíntese/fisiologia , Plantas/metabolismo , Transporte de Elétrons , Meio Ambiente , Luz , Complexo de Proteína do Fotossistema II/metabolismo
16.
New Phytol ; 221(1): 105-109, 2019 01.
Artigo em Inglês | MEDLINE | ID: mdl-30084195

RESUMO

Contents Summary 105 I. Introduction 105 II. Diversity of molecular mechanisms for regulation of photosynthetic electron transport 106 III. Role of FLVs in the regulation of photosynthesis in eukaryotes 107 IV. Why were FLVs lost in angiosperms? 108 V. Conclusions 108 Acknowledgements 109 References 109 SUMMARY: Photosynthetic electron transport requires continuous modulation to maintain the balance between light availability and metabolic demands. Multiple mechanisms for the regulation of electron transport have been identified and are unevenly distributed among photosynthetic organisms. Flavodiiron proteins (FLVs) influence photosynthetic electron transport by accepting electrons downstream of photosystem I to reduce oxygen to water. FLV activity has been demonstrated in cyanobacteria, green algae and mosses to be important in avoiding photosystem I overreduction upon changes in light intensity. FLV-encoding sequences were nevertheless lost during evolution by angiosperms, suggesting that these plants increased the efficiency of other mechanisms capable of accepting electrons from photosystem I, making the FLV activity for protection from overreduction superfluous or even detrimental for photosynthetic efficiency.


Assuntos
Evolução Biológica , Transporte de Elétrons , Fotossíntese/fisiologia , Fenômenos Fisiológicos Vegetais , Proteínas de Plantas/metabolismo , Magnoliopsida/fisiologia , Complexo de Proteína do Fotossistema I/metabolismo
17.
Plant Cell Environ ; 42(5): 1590-1602, 2019 05.
Artigo em Inglês | MEDLINE | ID: mdl-30496624

RESUMO

Photosynthetic organisms support cell metabolism by harvesting sunlight and driving the electron transport chain at the level of thylakoid membranes. Excitation energy and electron flow in the photosynthetic apparatus is continuously modulated in response to dynamic environmental conditions. Alternative electron flow around photosystem I plays a seminal role in this regulation contributing to photoprotection by mitigating overreduction of the electron carriers. Different pathways of alternative electron flow coexist in the moss Physcomitrella patens, including cyclic electron flow mediated by the PGRL1/PGR5 complex and pseudo-cyclic electron flow mediated by the flavodiiron proteins FLV. In this work, we generated P. patens plants carrying both pgrl1 and flva knock-out mutations. A comparative analysis of the WT, pgrl1, flva, and pgrl1 flva lines suggests that cyclic and pseudo-cyclic processes have a synergic role in the regulation of photosynthetic electron transport. However, although both contribute to photosystem I protection from overreduction by modulating electron flow following changes in environmental conditions, FLV activity is particularly relevant in the first seconds after a light change whereas PGRL1 has a major role upon sustained strong illumination.


Assuntos
Bryopsida/fisiologia , Transporte de Elétrons/fisiologia , Complexo de Proteínas do Centro de Reação Fotossintética/genética , Complexo de Proteína do Fotossistema I/metabolismo , Bryopsida/genética , Cloroplastos/metabolismo , Transporte de Elétrons/genética , Luz , Proteínas de Membrana/genética , Proteínas de Membrana/metabolismo , Mutação , Fotossíntese/genética , Fotossíntese/fisiologia , Complexo de Proteínas do Centro de Reação Fotossintética/metabolismo , Complexo de Proteína do Fotossistema I/genética , Plantas Geneticamente Modificadas , Luz Solar , Tilacoides/metabolismo
18.
Physiol Plant ; 166(1): 380-391, 2019 May.
Artigo em Inglês | MEDLINE | ID: mdl-30578540

RESUMO

The massive increase in carbon dioxide concentration in the atmosphere driven by human activities is causing huge negative consequences and new sustainable sources of energy, food and materials are highly needed. Algae are unicellular photosynthetic microorganisms that can provide a highly strategic contribution to this challenge as alternative source of biomass to complement crops cultivation. Algae industrial cultures are commonly limited by light availability, and biomass accumulation is strongly dependent on their photon-to-biomass conversion efficiency. Investigation of algae photosynthetic metabolism is thus strategic for the generation of more efficient strains with higher productivity. Algae are cultivated at industrial scale in conditions highly different from the natural niches they adapted to and strains development efforts must fully consider the seminal influence on productivity of regulatory mechanism of photosynthesis as well as of cultivation parameters like cells concentration, light distribution in the culture, mixing, nutrients and carbon dioxide availability. In this review we will focus in particular on how mathematical models can account for the complex influence of all environmental parameters and can be exploited for development of improved algae strains.


Assuntos
Microalgas/metabolismo , Fotossíntese/fisiologia , Biomassa , Biotecnologia , Dióxido de Carbono/metabolismo
19.
Biochim Biophys Acta Bioenerg ; 1859(9): 676-683, 2018 09.
Artigo em Inglês | MEDLINE | ID: mdl-29981721

RESUMO

In natural variable environments, plants rapidly adjust photosynthesis for optimum balance between photochemistry and photoprotection. These adjustments mainly occur via changes in their proton motive force (pmf). Recent studies based on time resolved analysis of the Electro Chromic Signal (ECS) bandshift of photosynthetic pigments in the model plant Arabidopsis thaliana have suggested an active role of ion fluxes across the thylakoid membranes in the regulation of the pmf. Among the different channels and transporters possibly involved in this phenomenon, we previously identified the TPK3 potassium channel. Plants silenced for TPK3 expression displayed light stress signatures, with reduced Non Photochemical Quenching (NPQ) capacity and sustained anthocyanin accumulation, even at moderate intensities. In this work we re-examined the role of this protein in pmf regulation, starting from the observation that both TPK3 knock-down (TPK3 KD) and WT plants display enhanced anthocyanin accumulation in the light under certain growth conditions, especially in old leaves. We thus compared the pmf features of young "green" (without anthocyanins) and old "red" (with anthocyanins) leaves in both genotypes using a global fit analysis of the ECS. We found that the differences in the ECS profile measured between the two genotypes reflect not only differences in TPK3 expression level, but also a modified photosynthetic activity of stressed red leaves, which are present in a larger amounts in the TPK3 KD plants.


Assuntos
Arabidopsis/metabolismo , Clorofila/metabolismo , Complexos de Proteínas Captadores de Luz/metabolismo , Plantas Geneticamente Modificadas/metabolismo , Canais de Potássio/metabolismo , Força Próton-Motriz , Arabidopsis/genética , Arabidopsis/efeitos da radiação , Luz , Complexos de Proteínas Captadores de Luz/genética , Fotossíntese , Plantas Geneticamente Modificadas/genética , Plantas Geneticamente Modificadas/efeitos da radiação , Canais de Potássio/genética , Tilacoides/metabolismo
20.
Plant Cell Physiol ; 59(7): 1377-1384, 2018 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-29878186

RESUMO

The adaptation to dehydration and rehydration cycles represents a key step in the evolution of photosynthetic organisms and requires the development of mechanisms by which to sense external stimuli and translate them into signaling components. In this study, we used genetically encoded fluorescent sensors to detect specific transient increases in the Ca2+ concentration in the moss Physcomitrella patens upon dehydration and rehydration treatment. Observation of the entire plant in a single time-series acquisition revealed that various cell types exhibited different sensitivities to osmotic stress and that Ca2+ waves originated from the basal part of the gametophore and were directionally propagated towards the top of the plant. Under similar conditions, the vascular plant Arabidopsis thaliana exhibited Ca2+ waves that propagated at a higher speed than those of P. patens. Our results suggest that systemic Ca2+ propagation occurs in plants even in the absence of vascular tissue, even though the rates can be different.


Assuntos
Bryopsida/metabolismo , Sinalização do Cálcio , Arabidopsis/metabolismo , Bryopsida/citologia , Bryopsida/fisiologia , Cálcio/análise , Cálcio/metabolismo , Calmodulina/metabolismo , Desidratação , Transferência Ressonante de Energia de Fluorescência , Proteínas Luminescentes/metabolismo , Imagem Molecular/métodos , Pressão Osmótica , Células Vegetais/metabolismo , Plantas Geneticamente Modificadas , Proteínas Recombinantes de Fusão/metabolismo
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