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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.
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.

3.
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
4.
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
5.
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
6.
Plant Direct ; 3(5): e00138, 2019 May.
Artigo em Inglês | MEDLINE | ID: mdl-31276082

RESUMO

Field-grown plants have variable exposure to sunlight as a result of shifting cloud-cover, seasonal changes, canopy shading, and other environmental factors. As a result, they need to have developed a method for dissipating excess energy obtained from periodic excessive sunlight exposure. Non-photochemical quenching (NPQ) dissipates excess energy as heat, however, the physical and molecular genetic mechanics of NPQ variation are not understood. In this study, we investigated the genetic loci involved in NPQ by first growing different Arabidopsis thaliana accessions in local and seasonal climate conditions, then measured their NPQ kinetics through development by chlorophyll fluorescence. We used genome-wide association studies (GWAS) to identify 15 significant quantitative trait loci (QTL) for a range of photosynthetic traits, including a QTL co-located with known NPQ gene PSBS (AT1G44575). We found there were large alternative regulatory segments between the PSBS promoter regions of the functional haplotypes and a significant difference in PsbS protein concentration. These findings parallel studies in rice showing recurrent regulatory evolution of this gene. The variation in the PSBS promoter and the changes underlying other QTLs could give insight to allow manipulations of NPQ in crops to improve their photosynthetic efficiency and yield.

7.
Front Plant Sci ; 10: 916, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31354779

RESUMO

Photosynthesis involves the conversion of sunlight energy into stored chemical energy, which is achieved through electron transport along a series of redox reactions. Excess photosynthetic electron transport might be dangerous due to the risk of molecular oxygen reduction, generating reactive oxygen species (ROS) over-accumulation. Avoiding excess ROS production requires the rate of electron transport to be coordinated with the capacity of electron acceptors in the chloroplast stroma. Imbalance between the donor and acceptor sides of photosystem I (PSI) can lead to inactivation, which is called PSI photoinhibition. We used a light-inducible PSI photoinhibition system in Arabidopsis thaliana to resolve the time dynamics of inhibition and to investigate its impact on ROS production and turnover. The oxidation state of the PSI reaction center and rates of CO2 fixation both indicated strong and rapid PSI photoinhibition upon donor side/acceptor side imbalance, while the rate of inhibition eased during prolonged imbalance. PSI photoinhibition was not associated with any major changes in ROS accumulation or antioxidant activity; however, a lower level of lipid oxidation correlated with lower abundance of chloroplast lipoxygenase in PSI-inhibited leaves. The results of this study suggest that rapid activation of PSI photoinhibition under severe photosynthetic imbalance protects the chloroplast from over-reduction and excess ROS formation.

9.
Biochim Biophys Acta Bioenerg ; 1860(6): 519-532, 2019 06 01.
Artigo em Inglês | MEDLINE | ID: mdl-31034800

RESUMO

Ca2+ is a potent signalling molecule that regulates many cellular processes. In cyanobacteria, Ca2+ has been linked to cell growth, stress response and photosynthesis, and to the development of specialist heterocyst cells in certain nitrogen-fixing species. Despite this, the pathways of Ca2+ signal transduction in cyanobacteria are poorly understood, and very few protein components are known. The current study describes a previously unreported Ca2+-binding protein which was called the Ca2+ Sensor EF-hand (CSE), which is conserved in filamentous, nitrogen-fixing cyanobacteria. CSE is shown to bind Ca2+, which induces a conformational change in the protein structure. Poor growth of a strain of Anabaena sp. PCC 7120 overexpressing CSE was attributed to diminished photosynthetic performance. Transcriptomics, biophysics and proteomics analyses revealed modifications in the light-harvesting phycobilisome and photosynthetic reaction centre protein complexes.


Assuntos
Anabaena/metabolismo , Proteínas de Bactérias/metabolismo , Cálcio/metabolismo , Transporte de Elétrons/fisiologia , Fotossíntese/fisiologia , Sequência de Aminoácidos , Anabaena/crescimento & desenvolvimento , Proteínas de Bactérias/genética , Proteínas de Bactérias/isolamento & purificação , Carbono/metabolismo , Cátions Bivalentes/metabolismo , Sequência Conservada , Regulação Bacteriana da Expressão Gênica , Técnicas de Inativação de Genes , Modelos Moleculares , Nitrogênio/metabolismo , Nitrogenase/metabolismo , Ligação Proteica , Conformação Proteica , Proteínas Recombinantes/genética , Proteínas Recombinantes/isolamento & purificação , Proteínas Recombinantes/metabolismo , Alinhamento de Sequência , Transcriptoma
10.
J Exp Bot ; 70(12): 3211-3225, 2019 06 28.
Artigo em Inglês | MEDLINE | ID: mdl-30938447

RESUMO

Pinaceae are the predominant photosynthetic species in boreal forests, but so far no detailed description of the protein components of the photosynthetic apparatus of these gymnosperms has been available. In this study we report a detailed characterization of the thylakoid photosynthetic machinery of Norway spruce (Picea abies (L.) Karst). We first customized a spruce thylakoid protein database from translated transcript sequences combined with existing protein sequences derived from gene models, which enabled reliable tandem mass spectrometry identification of P. abies thylakoid proteins from two-dimensional large pore blue-native/SDS-PAGE. This allowed a direct comparison of the two-dimensional protein map of thylakoid protein complexes from P. abies with the model angiosperm Arabidopsis thaliana. Although the subunit composition of P. abies core PSI and PSII complexes is largely similar to that of Arabidopsis, there was a high abundance of a smaller PSI subcomplex, closely resembling the assembly intermediate PSI* complex. In addition, the evolutionary distribution of light-harvesting complex (LHC) family members of Pinaceae was compared in silico with other land plants, revealing that P. abies and other Pinaceae (also Gnetaceae and Welwitschiaceae) have lost LHCB4, but retained LHCB8 (formerly called LHCB4.3). The findings reported here show the composition of the photosynthetic apparatus of P. abies and other Pinaceae members to be unique among land plants.


Assuntos
Fotossíntese/genética , Complexo de Proteínas do Centro de Reação Fotossintética/genética , Picea/genética , Sequência de Aminoácidos , Complexo de Proteínas do Centro de Reação Fotossintética/química , Complexo de Proteínas do Centro de Reação Fotossintética/metabolismo , Filogenia , Picea/metabolismo , Alinhamento de Sequência , Tilacoides/metabolismo
11.
Plant J ; 97(6): 1061-1072, 2019 03.
Artigo em Inglês | MEDLINE | ID: mdl-30488561

RESUMO

Natural growth environments commonly include fluctuating conditions that can disrupt the photosynthetic energy balance and induce photoinhibition through inactivation of the photosynthetic apparatus. Photosystem II (PSII) photoinhibition is efficiently reversed by the PSII repair cycle, whereas photoinhibited photosystem I (PSI) recovers much more slowly. In the current study, treatment of the Arabidopsis thaliana mutant proton gradient regulation 5 (pgr5) with excess light was used to compromise PSI functionality in order to investigate the impact of photoinhibition and subsequent recovery on photosynthesis and carbon metabolism. The negative impact of PSI photoinhibition on CO2 fixation was especially deleterious under low irradiance. Impaired starch accumulation after PSI photoinhibition was reflected in reduced respiration in the dark, but this was not attributed to impaired sugar synthesis. Normal chloroplast and mitochondrial metabolisms were shown to recover despite the persistence of substantial PSI photoinhibition for several days. The results of this study indicate that the recovery of PSI function involves the reorganization of the light-harvesting antennae, and suggest a pool of surplus PSI that can be recruited to support photosynthesis under demanding conditions.


Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/efeitos da radiação , Dióxido de Carbono/metabolismo , Carbono/metabolismo , Complexo de Proteínas do Centro de Reação Fotossintética/metabolismo , Complexo de Proteína do Fotossistema I/metabolismo , Complexo de Proteína do Fotossistema II/metabolismo , Arabidopsis/genética , Arabidopsis/fisiologia , Proteínas de Arabidopsis/genética , Metabolismo dos Carboidratos , Cloroplastos/metabolismo , Luz , Mitocôndrias/metabolismo , Mutação , Fotossíntese/efeitos da radiação , Complexo de Proteínas do Centro de Reação Fotossintética/genética , Amido/metabolismo
12.
Philos Trans R Soc Lond B Biol Sci ; 372(1730)2017 Sep 26.
Artigo em Inglês | MEDLINE | ID: mdl-28808104

RESUMO

The photosynthetic light reactions provide energy that is consumed and stored in electron sinks, the products of photosynthesis. A balance between light reactions and electron consumption in the chloroplast is vital for plants, and is protected by several photosynthetic regulation mechanisms. Photosystem I (PSI) is particularly susceptible to photoinhibition when these factors become unbalanced, which can occur in low temperatures or in high light. In this study we used the pgr5 Arabidopsis mutant that lacks ΔpH-dependent regulation of photosynthetic electron transport as a model to study the consequences of PSI photoinhibition under high light. We found that PSI damage severely inhibits carbon fixation and starch accumulation, and attenuates enzymatic oxylipin synthesis and chloroplast regulation of nuclear gene expression after high light stress. This work shows that modifications to regulation of photosynthetic light reactions, which may be designed to improve yield in crop plants, can negatively impact metabolism and signalling, and thereby threaten plant growth and stress tolerance.This article is part of the themed issue 'Enhancing photosynthesis in crop plants: targets for improvement'.


Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/fisiologia , Cloroplastos/metabolismo , Fotossíntese , Complexo de Proteína do Fotossistema I/genética , Transdução de Sinais , Transporte de Elétrons , Luz
13.
Nat Genet ; 49(6): 904-912, 2017 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-28481341

RESUMO

Silver birch (Betula pendula) is a pioneer boreal tree that can be induced to flower within 1 year. Its rapid life cycle, small (440-Mb) genome, and advanced germplasm resources make birch an attractive model for forest biotechnology. We assembled and chromosomally anchored the nuclear genome of an inbred B. pendula individual. Gene duplicates from the paleohexaploid event were enriched for transcriptional regulation, whereas tandem duplicates were overrepresented by environmental responses. Population resequencing of 80 individuals showed effective population size crashes at major points of climatic upheaval. Selective sweeps were enriched among polyploid duplicates encoding key developmental and physiological triggering functions, suggesting that local adaptation has tuned the timing of and cross-talk between fundamental plant processes. Variation around the tightly-linked light response genes PHYC and FRS10 correlated with latitude and longitude and temperature, and with precipitation for PHYC. Similar associations characterized the growth-promoting cytokinin response regulator ARR1, and the wood development genes KAK and MED5A.


Assuntos
Betula/genética , Genoma de Planta , Proteínas de Plantas/genética , Polimorfismo de Nucleotídeo Único , Adaptação Biológica/genética , Betula/fisiologia , Finlândia , Duplicação Gênica , Genética Populacional , Filogenia , Densidade Demográfica
14.
J Exp Bot ; 67(13): 3997-4008, 2016 06.
Artigo em Inglês | MEDLINE | ID: mdl-27012282

RESUMO

Calcium is integral to the perception, communication and adjustment of cellular responses to environmental changes. However, the role of Ca(2+) in fine-tuning cellular responses of wild-type cyanobacteria under favourable growth conditions has not been examined. In this study, extracellular Ca(2+) has been altered, and changes in the whole transcriptome of Anabaena sp. PCC 7120 have been evaluated under conditions replete of carbon and combined nitrogen. Ca(2+) induced differential expression of many genes driving primary cellular metabolism, with transcriptional regulation of carbon- and nitrogen-related processes responding with opposing trends. However, physiological effects of these transcriptional responses on biomass accumulation, biomass composition, and photosynthetic activity over the 24h period following Ca(2+) adjustment were found to be minor. It is well known that intracellular carbon:nitrogen balance is integral to optimal cell growth and that Ca(2+) plays an important role in the response of heterocystous cyanobacteria to combined-nitrogen deprivation. This work adds to the current knowledge by demonstrating a signalling role of Ca(2+) for making sensitive transcriptional adjustments required for optimal growth under non-limiting conditions.


Assuntos
Anabaena/metabolismo , Cálcio/metabolismo , Carbono/metabolismo , Nitrogênio/metabolismo , Anabaena/genética , Transdução de Sinais , Transcriptoma
15.
Curr Opin Plant Biol ; 27: 180-91, 2015 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-26318477

RESUMO

Chloroplast retrograde signalling is ultimately dependent on the function of the photosynthetic light reactions and not only guides the acclimation of the photosynthetic apparatus to changing environmental and metabolic cues, but has a much wider influence on the growth and development of plants. New information generated during the past few years about regulation of photosynthetic light reactions and identification of the underlying regulatory proteins has paved the way towards better understanding of the signalling molecules produced in chloroplasts upon changes in the environment. Likewise, the availability of various mutants lacking regulatory functions has made it possible to address the role of excitation energy distribution and electron flow in the thylakoid membrane in inducing the retrograde signals from chloroplasts to the nucleus. Such signalling molecules also induce and interact with hormonal signalling cascades to provide comprehensive information from chloroplasts to the nucleus.


Assuntos
Cloroplastos/metabolismo , Fotossíntese , Fenômenos Fisiológicos Vegetais , Transdução de Sinais
16.
Philos Trans R Soc Lond B Biol Sci ; 369(1640): 20130229, 2014 Apr 19.
Artigo em Inglês | MEDLINE | ID: mdl-24591716

RESUMO

The amount of light energy that is harvested and directed to the photosynthetic machinery is regulated in order to control the production of reactive oxygen species (ROS) in leaf tissues. ROS have important roles as signalling factors that instigate and mediate a range of cellular responses, suggesting that the mechanisms regulating light-harvesting and photosynthetic energy transduction also affect cell signalling. In this study, we exposed wild-type (WT) Arabidopsis and mutants impaired in the regulation of photosynthetic light-harvesting (stn7, tap38 and npq4) to transient high light (HL) stress in order to study the role of these mechanisms for up- and downregulation of gene expression under HL stress. The mutants, all of which have disturbed regulation of excitation energy transfer and distribution, responded to transient HL treatment with surprising similarity to the WT in terms of general 'abiotic stress-regulated' genes associated with hydrogen peroxide and 12-oxo-phytodienoic acid signalling. However, we identified distinct expression profiles in each genotype with respect to induction of singlet oxygen and jasmonic acid-dependent responses. The results of this study suggest that the control of excitation energy transfer interacts with hormonal regulation. Furthermore, the photosynthetic pigment-protein complexes appear to operate as receptors that sense the energetic balance between the photosynthetic light reactions and downstream metabolism.


Assuntos
Arabidopsis/fisiologia , Regulação da Expressão Gênica de Plantas/fisiologia , Transdução de Sinal Luminoso/fisiologia , Complexos de Proteínas Captadores de Luz/metabolismo , Luz , Fotossíntese/fisiologia , Espécies Reativas de Oxigênio/metabolismo , Arabidopsis/genética , Proteínas de Arabidopsis/genética , Biologia Computacional , Ciclopentanos/metabolismo , Perfilação da Expressão Gênica , Regulação da Expressão Gênica de Plantas/efeitos da radiação , Complexos de Proteínas Captadores de Luz/genética , Análise em Microsséries , Mutação/genética , Oxirredução , Oxilipinas/metabolismo , Fosfoproteínas Fosfatases/genética , Fotossíntese/genética , Complexo de Proteína do Fotossistema II/genética , Folhas de Planta/metabolismo , Folhas de Planta/fisiologia , Proteínas Serina-Treonina Quinases/genética , Oxigênio Singlete/metabolismo
17.
Front Plant Sci ; 4: 434, 2013 Oct 31.
Artigo em Inglês | MEDLINE | ID: mdl-24198822

RESUMO

It has been known for a long time that the thylakoid lumen provides the environment for oxygen evolution, plastocyanin-mediated electron transfer, and photoprotection. More recently lumenal proteins have been revealed to play roles in numerous processes, most often linked with regulating thylakoid biogenesis and the activity and turnover of photosynthetic protein complexes, especially the photosystem II and NAD(P)H dehydrogenase-like complexes. Still, the functions of the majority of lumenal proteins in Arabidopsis thaliana are unknown. Interestingly, while the thylakoid lumen proteome of at least 80 proteins contains several large protein families, individual members of many protein families have highly divergent roles. This is indicative of evolutionary pressure leading to neofunctionalization of lumenal proteins, emphasizing the important role of the thylakoid lumen for photosynthetic electron transfer and ultimately for plant fitness. Furthermore, the involvement of anterograde and retrograde signaling networks that regulate the expression and activity of lumen proteins is increasingly pertinent. Recent studies have also highlighted the importance of thiol/disulfide modulation in controlling the functions of many lumenal proteins and photosynthetic regulation pathways.

18.
Planta ; 237(2): 399-412, 2013 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-22971817

RESUMO

The comparative study of photosynthetic regulation in the thylakoid membrane of different phylogenetic groups can yield valuable insights into mechanisms, genetic requirements and redundancy of regulatory processes. This review offers a brief summary on the current understanding of light harvesting and photosynthetic electron transport regulation in different photosynthetic eukaryotes, with a special focus on the comparison between higher plants and unicellular algae of secondary endosymbiotic origin. The foundations of thylakoid structure, light harvesting, reversible protein phosphorylation and PSI-mediated cyclic electron transport are traced not only from green algae to vascular plants but also at the branching point between the "green" and the "red" lineage of photosynthetic organisms. This approach was particularly valuable in revealing processes that (1) are highly conserved between phylogenetic groups, (2) serve a common physiological role but nevertheless originate in divergent genetic backgrounds or (3) are missing in one phylogenetic branch despite their unequivocal importance in another, necessitating a search for alternative regulatory mechanisms and interactions.


Assuntos
Complexos de Proteínas Captadores de Luz/metabolismo , Filogenia , Arabidopsis/enzimologia , Arabidopsis/metabolismo , Proteínas de Arabidopsis/metabolismo , Proteínas de Cloroplastos/classificação , Proteínas de Cloroplastos/metabolismo , Diatomáceas/enzimologia , Diatomáceas/metabolismo , Transporte de Elétrons , Evolução Molecular , Fosforilação , Fotossíntese , Complexo de Proteína do Fotossistema I/metabolismo , Complexo de Proteína do Fotossistema II/metabolismo , Proteínas Serina-Treonina Quinases/metabolismo , Tilacoides/enzimologia , Tilacoides/metabolismo
19.
Plant Signal Behav ; 8(1): e22741, 2013 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-23221748

RESUMO

In a plant's natural environment, the intensity of light can change rapidly due to sunflecks, cloudiness and intermittent shading. Fluctuations between high and low illumination phases expose the photosynthetic machinery to rapidly changing signals that can be overlapping or contradictory, and accordingly plants have developed astute acclimation strategies to maintain optimal photosynthetic performance in these conditions. Continuous exposure to high light induces an array of protective mechanisms at anatomical, chemical and molecular levels, but when high light phases are short, such as under fluctuating light conditions, the protective strategies that afford protection to constant high light are not employed by plants. One mechanism that is engaged under both constant and fluctuating high light is the photosynthetic control of the Cyt b 6f complex, which prevents hyper-reduction of the electron transfer chain in order to protect PSI from photodamage. The PGR5 protein was recently shown to play an indispensable role in this protective mechanism. This review revisits the findings of earlier studies into photosynthetic control and places PGR5 within the broader context of photoprotection and light acclimation strategies.


Assuntos
Aclimatação , Proteínas de Arabidopsis/metabolismo , Arabidopsis/metabolismo , Complexo Citocromos b6f/metabolismo , Luz , Fotossíntese , Complexo de Proteínas do Centro de Reação Fotossintética/metabolismo , Complexo de Proteína do Fotossistema I/metabolismo , Arabidopsis/fisiologia , Respiração Celular , Transporte de Elétrons
20.
Front Plant Sci ; 3: 277, 2012.
Artigo em Inglês | MEDLINE | ID: mdl-23267361

RESUMO

Phosphorylation of the major photosynthetic light harvesting antenna proteins by STN7 kinase balances excitation between PSII and PSI. Phosphorylation of such abundant proteins is unique, differing distinctively from conventional tasks of protein kinases in phosphorylation of low abundance proteins in signaling cascades. Excitation balance between PSII and PSI is critical for redox homeostasis between the plastoquinone and plastocyanin pools and PSI electron acceptors, determining the capacity of the thylakoid membrane to produce reactive oxygen species (ROS) that operate as signals relaying information between chloroplasts and other cellular compartments. STN7 has also been proposed to be a conventional signaling kinase, instigating the phosphorylation cascade required for coordinated expression of photosynthesis genes and assembly of the photosynthetic machinery. The absence of STN7 kinase, however, does not prevent plants from sensing redox imbalance and adjusting the stoichiometry of the photosynthetic machinery to restore redox homeostasis. This suggests that STN7 is not essential for signaling between the chloroplast and the nucleus. Here we discuss the evolution and functions of the STN7 and other thylakoid protein kinases and phosphatases, and the inherent difficulties in analyzing signaling cascades initiated from the photosynthetic machinery. Based on our analyses of literature and publicly available expression data, we conclude that STN7 exerts it signaling effect primarily by controlling chloroplast ROS homeostasis through maintaining steady-state phosphorylation of the light harvesting II proteins and the redox balance in the thylakoid membrane. ROS are important signaling molecules with a direct effect on the development of jasmonate, which in turn relays information out from the chloroplast. We propose that thylakoid membrane redox homeostasis, regulated by SNT7, sends cell-wide signals that reprogram the entire hormonal network in the cell.

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