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1.
Int J Mol Sci ; 22(15)2021 Jul 29.
Artigo em Inglês | MEDLINE | ID: mdl-34360890

RESUMO

The thylakoid lumen houses proteins that are vital for photosynthetic electron transport, including water-splitting at photosystem (PS) II and shuttling of electrons from cytochrome b6f to PSI. Other lumen proteins maintain photosynthetic activity through biogenesis and turnover of PSII complexes. Although all lumen proteins are soluble, these known details have highlighted interactions of some lumen proteins with thylakoid membranes or thylakoid-intrinsic proteins. Meanwhile, the functional details of most lumen proteins, as well as their distribution between the soluble and membrane-associated lumen fractions, remain unknown. The current study isolated the soluble free lumen (FL) and membrane-associated lumen (MAL) fractions from Arabidopsis thaliana, and used gel- and mass spectrometry-based proteomics methods to analyze the contents of each proteome. These results identified 60 lumenal proteins, and clearly distinguished the difference between the FL and MAL proteomes. The most abundant proteins in the FL fraction were involved in PSII assembly and repair, while the MAL proteome was enriched in proteins that support the oxygen-evolving complex (OEC). Novel proteins, including a new PsbP domain-containing isoform, as well as several novel post-translational modifications and N-termini, are reported, and bi-dimensional separation of the lumen proteome identified several protein oligomers in the thylakoid lumen.


Assuntos
Proteínas de Arabidopsis/química , Proteínas de Arabidopsis/metabolismo , Arabidopsis/metabolismo , Membranas Intracelulares/metabolismo , Complexo de Proteína do Fotossistema II/química , Complexo de Proteína do Fotossistema II/metabolismo , Proteoma , Tilacoides/metabolismo , Arabidopsis/genética , Proteínas de Arabidopsis/genética , Eletroforese em Gel Bidimensional/métodos , Eletroforese em Gel de Poliacrilamida/métodos , Espectrometria de Massas/métodos , Fotossíntese/fisiologia , Complexo de Proteína do Fotossistema II/genética , Filogenia , Processamento de Proteína Pós-Traducional , Proteômica/métodos
2.
Microb Cell Fact ; 20(1): 130, 2021 Jul 10.
Artigo em Inglês | MEDLINE | ID: mdl-34246263

RESUMO

BACKGROUND: Synechocystis sp. PCC 6803 provides a well-established reference point to cyanobacterial metabolic engineering as part of basic photosynthesis research, as well as in the development of next-generation biotechnological production systems. This study focused on expanding the current knowledge on genomic integration of expression constructs in Synechocystis, targeting a range of novel sites in the chromosome and in the native plasmids, together with established loci used in literature. The key objective was to obtain quantitative information on site-specific expression in reference to replicon copy numbers, which has been speculated but never compared side by side in this host. RESULTS: An optimized sYFP2 expression cassette was successfully integrated in two novel sites in Synechocystis chromosome (slr0944; sll0058) and in all four endogenous megaplasmids (pSYSM/slr5037-slr5038; pSYSX/slr6037; pSYSA/slr7023; pSYSG/slr8030) that have not been previously evaluated for the purpose. Fluorescent analysis of the segregated strains revealed that the expression levels between the megaplasmids and chromosomal constructs were very similar, and reinforced the view that highest expression in Synechocystis can be obtained using RSF1010-derived replicative vectors or the native small plasmid pCA2.4 evaluated in comparison. Parallel replicon copy number analysis by RT-qPCR showed that the expression from the alternative loci is largely determined by the gene dosage in Synechocystis, thereby confirming the dependence formerly proposed based on literature. CONCLUSIONS: This study brings together nine different integrative loci in the genome of Synechocystis to demonstrate quantitative differences between target sites in the chromosome, the native plasmids, and a RSF1010-based replicative expression vector. To date, this is the most comprehensive comparison of alternative integrative sites in Synechocystis, and provides the first direct reference between expression efficiency and replicon gene dosage in the context. In the light of existing literature, the findings support the view that the small native plasmids can be notably more difficult to target than the chromosome or the megaplasmids, and that the RSF1010-derived vectors may be surprisingly well maintained under non-selective culture conditions in this cyanobacterial host. Altogether, the work broadens our views on genomic integration and the rational use of different integrative loci versus replicative plasmids, when aiming at expressing heterologous genes in Synechocystis.

3.
Physiol Plant ; 173(1): 305-320, 2021 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-34145600

RESUMO

Photosynthetic cyanobacteria are exposed to rapid changes in light intensity in their natural habitats, as well as in photobioreactors. To understand the effects of such fluctuations on Synechocystis sp. PCC 6803, the global proteome of cells grown under a fluctuating light condition (low background light interrupted with high light pulses) was compared to the proteome of cells grown under constant light with concomitant acclimation of cells to low CO2 level. The untargeted global proteome of Synechocystis sp. PCC 6803 was analyzed by data-dependent acquisition (DDA), which relies on the high mass accuracy and sensitivity of orbitrap-based tandem mass spectrometry. In addition, a targeted selected reaction monitoring (SRM) approach was applied to monitor the proteomic changes in a strain lacking flavodiiron proteins Flv1 and Flv3. This strain is characterized by impaired growth and photosynthetic activity under fluctuating light. An obvious reprogramming of cell metabolism was observed in this study and was compared to a previous transcriptional analysis performed under the same fluctuating light regime. Cyanobacterial responses to fluctuating light correlated at mRNA and protein levels to some extent, but discrepancies indicate that several proteins are post-transcriptionally regulated (affecting observed protein abundances). The data suggest that Synechocystis sp. PCC 6803 maintain higher nitrogen assimilation, serving as an electron valve, for long-term acclimation to fluctuating light upon CO2 step-down. Although Flv1 and Flv3 are known to be crucial for the cells at the onset of illumination, the flavodiiron proteins, as well as components of carbon assimilation pathways, were less abundant under fluctuating light.


Assuntos
Synechocystis , Proteínas de Bactérias/metabolismo , Dióxido de Carbono , Luz , Fotossíntese , Proteômica , Synechocystis/metabolismo
4.
Physiol Plant ; 173(2): 507-513, 2021 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-33709388

RESUMO

NordAqua is a multidisciplinary Nordic Center of Excellence funded by NordForsk Bioeconomy program (2017-2022). The research center promotes Blue Bioeconomy and endeavours to reform the use of natural resources in a environmentally sustainable way. In this short communication, we summarize particular outcomes of the consortium. The key research progress of NordAqua includes (1) improving of photosynthetisis, (2) developing novel photosynthetic cell factories that function in a "solar-driven direct CO2 capture to target bioproducts" mode, (3) promoting the diversity of Nordic cyanobacteria and algae as an abundant and resilient alternative for less sustainable forest biomass and for innovative production of biochemicals, and (4) improving the bio-based wastewater purification and nutrient recycling technologies to provide new tools for integrative circular economy platforms.


Assuntos
Fotossíntese , Biomassa
6.
Life (Basel) ; 10(11)2020 Nov 20.
Artigo em Inglês | MEDLINE | ID: mdl-33233741

RESUMO

Nostoc (Anabaena) sp. PCC 7120 is a filamentous cyanobacterial species that fixes N2 to nitrogenous compounds using specialised heterocyst cells. Changes in the intracellular ratio of carbon to nitrogen (C/N balance) is known to trigger major transcriptional reprogramming of the cell, including initiating the differentiation of vegetative cells to heterocysts. Substantial transcriptional analysis has been performed on Nostoc sp. PCC 7120 during N stepdown (low to high C/N), but not during C stepdown (high to low C/N). In the current study, we shifted the metabolic balance of Nostoc sp. PCC 7120 cultures grown at 3% CO2 by introducing them to atmospheric conditions containing 0.04% CO2 for 1 h, after which the changes in gene expression were measured using RNAseq transcriptomics. This analysis revealed strong upregulation of carbon uptake, while nitrogen uptake and metabolism and early stages of heterocyst development were downregulated in response to the shift to low CO2. Furthermore, gene expression changes revealed a decrease in photosynthetic electron transport and increased photoprotection and reactive oxygen metabolism, as well a decrease in iron uptake and metabolism. Differential gene expression was largely attributed to change in the abundances of the metabolites 2-phosphoglycolate and 2-oxoglutarate, which signal a rapid shift from fluent photoassimilation to glycolytic metabolism of carbon after transition to low CO2. This work shows that the C/N balance in Nostoc sp. PCC 7120 rapidly adjusts the metabolic strategy through transcriptional reprogramming, enabling survival in the fluctuating environment.

7.
J Exp Bot ; 71(22): 7210-7223, 2020 12 31.
Artigo em Inglês | MEDLINE | ID: mdl-32930769

RESUMO

Plants can quickly and dynamically respond to spectral and intensity variations of the incident light. These responses include activation of developmental processes, morphological changes, and photosynthetic acclimation that ensure optimal energy conversion and minimal photoinhibition. Plant adaptation and acclimation to environmental changes have been extensively studied, but many details surrounding these processes remain elusive. The photosystem II (PSII)-associated protein PSB33 plays a fundamental role in sustaining PSII as well as in the regulation of the light antenna in fluctuating light. We investigated how PSB33 knock-out Arabidopsis plants perform under different light qualities. psb33 plants displayed a reduction of 88% of total fresh weight compared to wild type plants when cultivated at the boundary of UV-A and blue light. The sensitivity towards UV-A light was associated with a lower abundance of PSII proteins, which reduces psb33 plants' capacity for photosynthesis. The UV-A phenotype was found to be linked to altered phytohormone status and changed thylakoid ultrastructure. Our results collectively show that PSB33 is involved in a UV-A light-mediated mechanism to maintain a functional PSII pool in the chloroplast.


Assuntos
Proteínas de Arabidopsis , Arabidopsis , Arabidopsis/genética , Arabidopsis/metabolismo , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Cloroplastos/metabolismo , Luz , Fotossíntese , Complexo de Proteína do Fotossistema II/metabolismo , Tilacoides/metabolismo
8.
BMC Plant Biol ; 20(1): 413, 2020 Sep 04.
Artigo em Inglês | MEDLINE | ID: mdl-32887556

RESUMO

BACKGROUND: Non-photosynthetic plastids of plants are known to be involved in a range of metabolic and biosynthetic reactions, even if they have been difficult to study due to their small size and lack of color. The morphology of root plastids is heterogeneous and also the plastid size, density and subcellular distribution varies depending on the cell type and developmental stage, and therefore the functional features have remained obscure. Although the root plastid proteome is likely to reveal specific functional features, Arabidopsis thaliana root plastid proteome has not been studied to date. RESULTS: In the present study, we separated Arabidopsis root protein fraction enriched with plastids and mitochondria by 2D-PAGE and identified 84 plastid-targeted and 77 mitochondrion-targeted proteins using LC-MS/MS. The most prevalent root plastid protein categories represented amino acid biosynthesis, carbohydrate metabolism and lipid biosynthesis pathways, while the enzymes involved in starch and sucrose metabolism were not detected. Mitochondrion-targeted proteins were classified mainly into the energetics category. CONCLUSIONS: This is the first study presenting gel-based map of Arabidopsis thaliana root plastid and mitochondrial proteome. Our findings suggest that Arabidopsis root plastids have broad biosynthetic capacity, and that they do not play a major role in a long-term storage of carbohydrates. The proteomic map provides a tool for further studies to compare changes in the proteome, e.g. in response to environmental cues, and emphasizes the role of root plastids in nitrogen and sulfur metabolism as well as in amino acid and fatty acid biosynthesis. The results enable taking a first step towards an integrated view of root plastid/mitochondrial proteome and metabolic functions in Arabidopsis thaliana roots.


Assuntos
Arabidopsis/genética , Mapeamento Cromossômico , Mitocôndrias/genética , Proteínas de Plantas/genética , Plastídeos/genética , Proteoma/genética , Eletroforese em Gel Bidimensional , Raízes de Plantas/genética , Proteômica
9.
Proc Natl Acad Sci U S A ; 117(30): 17499-17509, 2020 07 28.
Artigo em Inglês | MEDLINE | ID: mdl-32690715

RESUMO

Coping of evergreen conifers in boreal forests with freezing temperatures on bright winter days puts the photosynthetic machinery in great risk of oxidative damage. To survive harsh winter conditions, conifers have evolved a unique but poorly characterized photoprotection mechanism, a sustained form of nonphotochemical quenching (sustained NPQ). Here we focused on functional properties and underlying molecular mechanisms related to the development of sustained NPQ in Norway spruce (Picea abies). Data were collected during 4 consecutive years (2016 to 2019) from trees growing in sun and shade habitats. When day temperatures dropped below -4 °C, the specific N-terminally triply phosphorylated LHCB1 isoform (3p-LHCII) and phosphorylated PSBS (p-PSBS) could be detected in the thylakoid membrane. Development of sustained NPQ coincided with the highest level of 3p-LHCII and p-PSBS, occurring after prolonged coincidence of bright winter days and temperatures close to -10 °C. Artificial induction of both the sustained NPQ and recovery from naturally induced sustained NPQ provided information on differential dynamics and light-dependence of 3p-LHCII and p-PSBS accumulation as prerequisites for sustained NPQ. Data obtained collectively suggest three components related to sustained NPQ in spruce: 1) Freezing temperatures induce 3p-LHCII accumulation independently of light, which is suggested to initiate destacking of appressed thylakoid membranes due to increased electrostatic repulsion of adjacent membranes; 2) p-PSBS accumulation is both light- and temperature-dependent and closely linked to the initiation of sustained NPQ, which 3) in concert with PSII photoinhibition, is suggested to trigger sustained NPQ in spruce.


Assuntos
Fotossíntese , Picea/fisiologia , Estações do Ano , Proteínas das Membranas dos Tilacoides/metabolismo , Tilacoides/metabolismo , Sequência de Aminoácidos , Meio Ambiente , Complexos de Proteínas Captadores de Luz/metabolismo , Noruega , Fosforilação , Espectrometria de Massas em Tandem , Proteínas das Membranas dos Tilacoides/química , Árvores
10.
Front Plant Sci ; 11: 382, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32351519

RESUMO

In plant science, 2,4-dinitrophenylether of iodonitrothymol (DNP-INT) is frequently used as an alternative to 2,5-dibromo-6-isopropyl-3-methyl-1,4-benzoquinone (DBMIB) to examine the capacity of plastoquinol and semiquinone to reduce O2. DNP-INT is considered to be an effective inhibitor of the photosynthetic electron transfer chain (PETC) through its binding at the Q0 site of Cyt-b6f. The binding and action of DNP-INT has been previously characterized spectroscopically in purified Cyt-b6f complex reconstituted with Plastocyanin, PSII membranes and plastoquinone, as well as in isolated thylakoids based on its property to block MV-mediated O2 consumption. Contrary to the conclusions obtained from these experiments, we observed clear reduction of P700+ in samples incubated with DNP-INT during our recent investigation into the sites of oxygen consumption in isolated thylakoids. Therefore, we carried out an extensive investigation of DNP-INT's chemical efficacy in isolated thylakoids and intact leaves. This included examination of its capacity to block the PETC before PSI, and therefore its inhibition of CO2 fixation. P700 redox kinetics were measured using Dual-PAM whilst Membrane Inlet Mass Spectrometry (MIMS) was used for simultaneous determination of the rates of O2 evolution and O2 consumption in isolated thylakoids and CO2 fixation in intact leaves, using two stable isotopes of oxygen (16O2, 18O2) and CO2 (12C, 13C), respectively. Based on these investigations we confirmed that DNP-INT is unable to completely block the PETC and CO2 fixation, therefore its use may produce artifacts if applied to isolated thylakoids or intact cells, especially when determining the locations of reactive oxygen species formation in the photosynthetic apparatus.

11.
Philos Trans R Soc Lond B Biol Sci ; 375(1801): 20190406, 2020 06 22.
Artigo em Inglês | MEDLINE | ID: mdl-32362249

RESUMO

The photosynthetic apparatus is one of the major primary sensors of the plant's external environment. Changes in environmental conditions affect the balance between harvested light energy and the capacity to deal with excited electrons in the stroma, which alters the redox homeostasis of the photosynthetic electron transport chain. Disturbances to redox balance activate photosynthetic regulation mechanisms and trigger signalling cascades that can modify the transcription of nuclear genes. H2O2 and oxylipins have been identified as especially prominent regulators of gene expression in response to excess light stress. This paper explores the hypothesis that photosynthetic imbalance triggers specific signals that target discrete gene profiles and biological processes. Analysis of the major retrograde signalling pathways engaged during high light stress and recovery demonstrates both specificity and overlap in gene targets. This work reveals distinct, time-resolved profiles of gene expression that suggest a regulatory interaction between rapidly activated abiotic stress response and induction of secondary metabolism and detoxification processes during recovery. The findings of this study show that photosynthetic electron transport provides a finely tuned sensor for detecting and responding to the environment through chloroplast retrograde signalling. This article is part of the theme issue 'Retrograde signalling from endosymbiotic organelles'.


Assuntos
Arabidopsis/fisiologia , Cloroplastos/fisiologia , Luz/efeitos adversos , Fotossíntese/fisiologia , Transdução de Sinais , Transporte de Elétrons , Estresse Fisiológico
12.
Philos Trans R Soc Lond B Biol Sci ; 375(1801): 20190413, 2020 06 22.
Artigo em Inglês | MEDLINE | ID: mdl-32362253

RESUMO

The Arabidopsis mutant rcd1 is tolerant to methyl viologen (MV). MV enhances the Mehler reaction, i.e. electron transfer from Photosystem I (PSI) to O2, generating reactive oxygen species (ROS) in the chloroplast. To study the MV tolerance of rcd1, we first addressed chloroplast thiol redox enzymes potentially implicated in ROS scavenging. NADPH-thioredoxin oxidoreductase type C (NTRC) was more reduced in rcd1. NTRC contributed to the photosynthetic and metabolic phenotypes of rcd1, but did not determine its MV tolerance. We next tested rcd1 for alterations in the Mehler reaction. In rcd1, but not in the wild type, the PSI-to-MV electron transfer was abolished by hypoxic atmosphere. A characteristic feature of rcd1 is constitutive expression of mitochondrial dysfunction stimulon (MDS) genes that affect mitochondrial respiration. Similarly to rcd1, in other MDS-overexpressing plants hypoxia also inhibited the PSI-to-MV electron transfer. One possible explanation is that the MDS gene products may affect the Mehler reaction by altering the availability of O2. In green tissues, this putative effect is masked by photosynthetic O2 evolution. However, O2 evolution was rapidly suppressed in MV-treated plants. Transcriptomic meta-analysis indicated that MDS gene expression is linked to hypoxic response not only under MV, but also in standard growth conditions. This article is part of the theme issue 'Retrograde signalling from endosymbiotic organelles'.


Assuntos
Arabidopsis/genética , Arabidopsis/fisiologia , Mitocôndrias/metabolismo , Fotossíntese , Transdução de Sinais , Anaerobiose , Proteínas de Arabidopsis/genética , Transporte de Elétrons , Proteínas Nucleares/genética
13.
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
14.
Plant Cell Physiol ; 61(6): 1168-1180, 2020 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-32277833

RESUMO

In green plants, photosystem II (PSII) forms multisubunit supercomplexes (SCs) containing a dimeric core and light-harvesting complexes (LHCs). In this study, we show that Arabidopsis thaliana PsbP-like protein 1 (PPL1) is involved in the assembly of the PSII SCs and is required for adaptation to changing light intensity. PPL1 is a homolog of PsbP protein that optimizes the water-oxidizing reaction of PSII in green plants and is required for the efficient repair of photodamaged PSII; however, its exact function has been unknown. PPL1 was enriched in stroma lamellae and grana margins and associated with PSII subcomplexes including PSII monomers and PSII dimers, and several LHCII assemblies, while PPL1 was not detected in PSII-LHCII SCs. In a PPL1 null mutant (ppl1-2), assembly of CP43, PsbR and PsbW was affected, resulting in a reduced accumulation of PSII SCs even under moderate light intensity. This caused the abnormal association of LHCII in ppl1-2, as indicated by lower maximal quantum efficiency of PSII (Fv/Fm) and accelerated State 1 to State 2 transitions. These differences would lower the capability of plants to adapt to changing light environments, thereby leading to reduced growth under natural fluctuating light environments. Phylogenetic and structural analyses suggest that PPL1 is closely related to its cyanobacterial homolog CyanoP, which functions as an assembly factor in the early stage of PSII biogenesis. Our results suggest that PPL1 has a similar function, but the data also indicate that it could aid the association of LHCII with PSII.


Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/metabolismo , Complexo de Proteína do Fotossistema II/metabolismo , Arabidopsis/genética , Arabidopsis/fisiologia , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/fisiologia , Luz , Complexo de Proteína do Fotossistema II/genética , Complexo de Proteína do Fotossistema II/fisiologia , Filogenia , Estrutura Terciária de Proteína , Reação em Cadeia da Polimerase em Tempo Real , Alinhamento de Sequência , Tilacoides/metabolismo
15.
Photochem Photobiol Sci ; 19(5): 604-619, 2020 May 20.
Artigo em Inglês | MEDLINE | ID: mdl-32297616

RESUMO

The photosystems (PS), catalyzing the photosynthetic reactions of higher plants, are unevenly distributed in the thylakoid membrane: PSII, together with its light harvesting complex (LHC)II, is enriched in the appressed grana stacks, while PSI-LHCI resides in the non-appressed stroma thylakoids, which wind around the grana stacks. The two photosystems interact in a third membrane domain, the grana margins, which connect the grana and stroma thylakoids and allow the loosely bound LHCII to serve as an additional antenna for PSI. The light harvesting is balanced by reversible phosphorylation of LHCII proteins. Nevertheless, light energy also damages PSII and the repair process is regulated by reversible phosphorylation of PSII core proteins. Here, we discuss the detailed composition and organization of PSII-LHCII and PSI-LHCI (super)complexes in the thylakoid membrane of angiosperm chloroplasts and address the role of thylakoid protein phosphorylation in dynamics of the entire protein complex network of the photosynthetic membrane. Finally, we scrutinize the phosphorylation-dependent dynamics of the protein complexes in context of thylakoid ultrastructure and present a model on the reorganization of the entire thylakoid network in response to changes in thylakoid protein phosphorylation.


Assuntos
Arabidopsis/química , Complexo de Proteína do Fotossistema I/metabolismo , Complexo de Proteína do Fotossistema II/metabolismo , Tilacoides/metabolismo , Arabidopsis/metabolismo , Fosforilação , Complexo de Proteína do Fotossistema I/química , Complexo de Proteína do Fotossistema II/química , Tilacoides/química
16.
Plant Cell Environ ; 43(6): 1484-1500, 2020 06.
Artigo em Inglês | MEDLINE | ID: mdl-32176335

RESUMO

Drought is a major cause of losses in crop yield. Under field conditions, plants exposed to drought are usually also experiencing rapid changes in light intensity. Accordingly, plants need to acclimate to both, drought and light stress. Two crucial mechanisms in plant acclimation to changes in light conditions comprise thylakoid protein phosphorylation and dissipation of light energy as heat by non-photochemical quenching (NPQ). Here, we analyzed the acclimation efficacy of two different wheat varieties, by applying fluctuating light for analysis of plants, which had been subjected to a slowly developing drought stress as it usually occurs in the field. This novel approach allowed us to distinguish four drought phases, which are critical for grain yield, and to discover acclimatory responses which are independent of photodamage. In short-term, under fluctuating light, the slowdown of NPQ relaxation adjusts the photosynthetic activity to the reduced metabolic capacity. In long-term, the photosynthetic machinery acquires a drought-specific configuration by changing the PSII-LHCII phosphorylation pattern together with protein stoichiometry. Therefore, the fine-tuning of NPQ relaxation and PSII-LHCII phosphorylation pattern represent promising traits for future crop breeding strategies.


Assuntos
Secas , Luz , Fotossíntese/efeitos da radiação , Triticum/fisiologia , Triticum/efeitos da radiação , Aclimatação/fisiologia , Ecótipo , Complexos de Proteínas Captadores de Luz/metabolismo , Fosforilação/efeitos da radiação , Complexo de Proteína do Fotossistema II/metabolismo , Estresse Fisiológico/efeitos da radiação , Triticum/crescimento & desenvolvimento
17.
BMC Microbiol ; 20(1): 57, 2020 03 11.
Artigo em Inglês | MEDLINE | ID: mdl-32160863

RESUMO

BACKGROUND: Filamentous cyanobacteria represent model organisms for investigating multicellularity. For many species, nitrogen-fixing heterocysts are formed from photosynthetic vegetative cells under nitrogen limitation. Intracellular Ca2+ has been implicated in the highly regulated process of heterocyst differentiation but its role remains unclear. Ca2+ is known to operate more broadly in metabolic signalling in cyanobacteria, although the signalling mechanisms are virtually unknown. A Ca2+-binding protein called the Ca2+ Sensor EF-hand (CSE) is found almost exclusively in filamentous cyanobacteria. Expression of asr1131 encoding the CSE protein in Anabaena sp. PCC 7120 was strongly induced by low CO2 conditions, and rapidly downregulated during nitrogen step-down. A previous study suggests a role for CSE and Ca2+ in regulation of photosynthetic activity in response to changes in carbon and nitrogen availability. RESULTS: In the current study, a mutant Anabaena sp. PCC 7120 strain lacking asr1131 (Δcse) was highly prone to filament fragmentation, leading to a striking phenotype of very short filaments and poor growth under nitrogen-depleted conditions. Transcriptomics analysis under nitrogen-replete conditions revealed that genes involved in heterocyst differentiation and function were downregulated in Δcse, while heterocyst inhibitors were upregulated, compared to the wild-type. CONCLUSIONS: These results indicate that CSE is required for filament integrity and for proper differentiation and function of heterocysts upon changes in the cellular carbon/nitrogen balance. A role for CSE in transmitting Ca2+ signals during the first response to changes in metabolic homeostasis is discussed.


Assuntos
Anabaena/crescimento & desenvolvimento , Proteínas de Bactérias/metabolismo , Nitrogênio/metabolismo , Anabaena/genética , Anabaena/metabolismo , Sinalização do Cálcio , Dióxido de Carbono/metabolismo , Regulação Bacteriana da Expressão Gênica , Fotossíntese
18.
Plant Physiol ; 183(1): 67-79, 2020 05.
Artigo em Inglês | MEDLINE | ID: mdl-32198308

RESUMO

Despite the ecological relevance of diatoms, many aspects of their photosynthetic machinery remain poorly understood. Diatoms differ from the green lineage of oxygenic organisms by their photosynthetic pigments and light-harvesting complex (Lhc) proteins, the latter of which are also called fucoxanthin-chlorophyll proteins (FCP). These are composed of three groups of proteins: Lhcf as the main group, Lhcr that are PSI associated, and Lhcx that are involved in photoprotection. The FCP complexes are assembled in trimers and higher oligomers. Several studies have investigated the biochemical properties of purified FCP complexes, but limited knowledge is available about their interaction with the photosystem cores. In this study, isolation of stable supercomplexes from the centric diatom Thalassiosira pseudonana was achieved. To preserve in vivo structure, the separation of thylakoid complexes was performed by native PAGE and sucrose density centrifugation. Different subpopulations of PSI and PSII supercomplexes were isolated and their subunits identified. Analysis of Lhc antenna composition identified Lhc(s) specific for either PSI (Lhcr 1, 3, 4, 7, 10-14, and Lhcf10) or PSII (Lhcf 1-7, 11, and Lhcr2). Lhcx6_1 was reproducibly found in PSII supercomplexes, whereas its association with PSI was unclear. No evidence was found for the interaction between photosystems and higher oligomeric FCPs, comprising Lhcf8 as the main component. Although the subunit composition of the PSII supercomplexes in comparison with that of the trimeric FCP complexes indicated a close mutual association, the higher oligomeric pool is only weakly associated with the photosystems, albeit its abundance in the thylakoid membrane.


Assuntos
Diatomáceas/metabolismo , Complexo de Proteína do Fotossistema I/metabolismo , Complexo de Proteína do Fotossistema II/metabolismo , Diatomáceas/genética , Escherichia coli/genética , Escherichia coli/metabolismo , Frutas/genética , Frutas/metabolismo , Complexo de Proteína do Fotossistema I/genética , Complexo de Proteína do Fotossistema II/genética , Locos de Características Quantitativas/genética , Relação Estrutura-Atividade , Tilacoides/metabolismo
19.
Biochim Biophys Acta Bioenerg ; 1861(3): 148154, 2020 03 01.
Artigo em Inglês | MEDLINE | ID: mdl-31935360

RESUMO

Avoidance of photoinhibition at photosystem (PS)I is based on synchronized function of PSII, PSI, Cytochrome b6f and stromal electron acceptors. Here, we used a special light regime, PSI photoinhibition treatment (PIT), in order to specifically inhibit PSI by accumulating excess electrons at the photosystem (Tikkanen and Grebe, 2018). In the analysis, Arabidopsis thaliana WT was compared to the pgr5 and ndho mutants, deficient in one of the two main cyclic electron transfer pathways described to function as protective alternative electron acceptors of PSI. The aim was to investigate whether the PGR5 (pgr5) and the type I NADH dehydrogenase (NDH-1) (ndho) systems protect PSI from excess electron stress and whether they help plants to cope with the consequences of PSI photoinhibition. First, our data reveals that neither PGR5 nor NDH-1 system protects PSI from a sudden burst of electrons. This strongly suggests that these systems in Arabidopsis thaliana do not function as direct acceptors of electrons delivered from PSII to PSI - contrasting with the flavodiiron proteins that were found to make Physcomitrella patens PSI resistant to the PIT. Second, it is demonstrated that under light-limiting conditions, the electron transfer rate at PSII is linearly dependent on the amount of functional PSI in all genotypes, while under excess light, the PGR5-dependent control of electron flow at the Cytochrome b6f complex overrides the effect of PSI inhibition. Finally, the PIT is shown to increase the amount of PGR5 and NDH-1 as well as of PTOX, suggesting that they mitigate further damage to PSI after photoinhibition rather than protect against it.


Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/metabolismo , Elétrons , NAD(P)H Desidrogenase (Quinona)/metabolismo , Complexo de Proteínas do Centro de Reação Fotossintética/metabolismo , Complexo de Proteína do Fotossistema I/metabolismo , Arabidopsis/genética , Arabidopsis/efeitos da radiação , Transporte de Elétrons/efeitos da radiação , Genótipo , Luz , Oxirredução/efeitos da radiação , Fosforilação/efeitos da radiação , Complexo de Proteína do Fotossistema II/metabolismo
20.
Plant Physiol ; 182(2): 1161-1181, 2020 02.
Artigo em Inglês | MEDLINE | ID: mdl-31659127

RESUMO

Plants optimize their growth and survival through highly integrated regulatory networks that coordinate defensive measures and developmental transitions in response to environmental cues. Protein phosphatase 2A (PP2A) is a key signaling component that controls stress reactions and growth at different stages of plant development, and the PP2A regulatory subunit PP2A-B'γ is required for negative regulation of pathogenesis responses and for maintenance of cell homeostasis in short-day conditions. Here, we report molecular mechanisms by which PP2A-B'γ regulates Botrytis cinerea resistance and leaf senescence in Arabidopsis (Arabidopsis thaliana). We extend the molecular functionality of PP2A-B'γ to a protein kinase-phosphatase interaction with the defense-associated calcium-dependent protein kinase CPK1 and present indications this interaction may function to control CPK1 activity. In presenescent leaf tissues, PP2A-B'γ is also required to negatively control the expression of salicylic acid-related defense genes, which have recently proven vital in plant resistance to necrotrophic fungal pathogens. In addition, we find the premature leaf yellowing of pp2a-b'γ depends on salicylic acid biosynthesis via SALICYLIC ACID INDUCTION DEFICIENT2 and bears the hallmarks of developmental leaf senescence. We propose PP2A-B'γ age-dependently controls salicylic acid-related signaling in plant immunity and developmental leaf senescence.


Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/enzimologia , Botrytis/imunologia , Senescência Celular/genética , Resistência à Doença/genética , Doenças das Plantas/imunologia , Folhas de Planta/metabolismo , Proteína Fosfatase 2/metabolismo , Arabidopsis/genética , Arabidopsis/crescimento & desenvolvimento , Arabidopsis/microbiologia , Proteínas de Arabidopsis/genética , Cálcio/metabolismo , Senescência Celular/fisiologia , Cisteína Endopeptidases/genética , Cisteína Endopeptidases/metabolismo , Resistência à Doença/imunologia , Regulação da Expressão Gênica no Desenvolvimento/genética , Regulação da Expressão Gênica de Plantas/genética , Genótipo , Transferases Intramoleculares/genética , Transferases Intramoleculares/metabolismo , Mutação , Fenótipo , Doenças das Plantas/genética , Doenças das Plantas/microbiologia , Imunidade Vegetal/genética , Folhas de Planta/genética , Folhas de Planta/crescimento & desenvolvimento , Ligação Proteica , Proteínas Quinases/genética , Proteínas Quinases/metabolismo , Proteína Fosfatase 2/genética , Ácido Salicílico/metabolismo , Transdução de Sinais/genética , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo , Transcriptoma/genética
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