Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 27
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
Plant Physiol ; 186(4): 1859-1877, 2021 Aug 03.
Artigo em Inglês | MEDLINE | ID: mdl-34618107

RESUMO

Mitochondria are tightly embedded within metabolic and regulatory networks that optimize plant performance in response to environmental challenges. The best-known mitochondrial retrograde signaling pathway involves stress-induced activation of the transcription factor NAC DOMAIN CONTAINING PROTEIN 17 (ANAC017), which initiates protective responses to stress-induced mitochondrial dysfunction in Arabidopsis (Arabidopsis thaliana). Posttranslational control of the elicited responses, however, remains poorly understood. Previous studies linked protein phosphatase 2A subunit PP2A-B'γ, a key negative regulator of stress responses, with reversible phosphorylation of ACONITASE 3 (ACO3). Here we report on ACO3 and its phosphorylation at Ser91 as key components of stress regulation that are induced by mitochondrial dysfunction. Targeted mass spectrometry-based proteomics revealed that the abundance and phosphorylation of ACO3 increased under stress, which required signaling through ANAC017. Phosphomimetic mutation at ACO3-Ser91 and accumulation of ACO3S91D-YFP promoted the expression of genes related to mitochondrial dysfunction. Furthermore, ACO3 contributed to plant tolerance against ultraviolet B (UV-B) or antimycin A-induced mitochondrial dysfunction. These findings demonstrate that ACO3 is both a target and mediator of mitochondrial dysfunction signaling, and critical for achieving stress tolerance in Arabidopsis leaves.

2.
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
3.
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
4.
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
5.
PLoS One ; 15(7): e0227466, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32678822

RESUMO

Trans-methylation reactions are intrinsic to cellular metabolism in all living organisms. In land plants, a range of substrate-specific methyltransferases catalyze the methylation of DNA, RNA, proteins, cell wall components and numerous species-specific metabolites, thereby providing means for growth and acclimation in various terrestrial habitats. Trans-methylation reactions consume vast amounts of S-adenosyl-L-methionine (SAM) as a methyl donor in several cellular compartments. The inhibitory reaction by-product, S-adenosyl-L-homocysteine (SAH), is continuously removed by SAH hydrolase (SAHH), which essentially maintains trans-methylation reactions in all living cells. Here we report on the evolutionary conservation and post-translational control of SAHH in land plants. We provide evidence suggesting that SAHH forms oligomeric protein complexes in phylogenetically divergent land plants and that the predominant protein complex is composed by a tetramer of the enzyme. Analysis of light-stress-induced adjustments of SAHH in Arabidopsis thaliana and Physcomitrella patens further suggests that regulatory actions may take place on the levels of protein complex formation and phosphorylation of this metabolically central enzyme. Collectively, these data suggest that plant adaptation to terrestrial environments involved evolution of regulatory mechanisms that adjust the trans-methylation machinery in response to environmental cues.


Assuntos
Adenosil-Homocisteinase/metabolismo , Proteínas de Arabidopsis/metabolismo , Arabidopsis/enzimologia , Evolução Molecular , Adenosil-Homocisteinase/classificação , Adenosil-Homocisteinase/genética , Sequência de Aminoácidos , Proteínas de Arabidopsis/classificação , Proteínas de Arabidopsis/genética , Eletroforese em Gel Bidimensional , Focalização Isoelétrica , Luz , Filogenia , Folhas de Planta/enzimologia , Processamento de Proteína Pós-Traducional/efeitos da radiação , RNA Mensageiro/metabolismo , Alinhamento de Sequência , Estresse Fisiológico
6.
Plant J ; 101(5): 1198-1220, 2020 03.
Artigo em Inglês | MEDLINE | ID: mdl-31648387

RESUMO

Correct chloroplast development and function require co-ordinated expression of chloroplast and nuclear genes. This is achieved through chloroplast signals that modulate nuclear gene expression in accordance with the chloroplast's needs. Genetic evidence indicates that GUN1, a chloroplast-localized pentatricopeptide repeat (PPR) protein with a C-terminal Small MutS-Related (SMR) domain, is involved in integrating multiple developmental and stress-related signals in both young seedlings and adult leaves. Recently, GUN1 was found to interact physically with factors involved in chloroplast protein homeostasis, and with enzymes of tetrapyrrole biosynthesis in adult leaves that function in various retrograde signalling pathways. Here we show that following perturbation of chloroplast protein homeostasis: (i) by growth in lincomycin-containing medium; or (ii) in mutants defective in either the FtsH protease complex (ftsh), plastid ribosome activity (prps21-1 and prpl11-1) or plastid protein import and folding (cphsc70-1), GUN1 influences NEP-dependent transcript accumulation during cotyledon greening and also intervenes in chloroplast protein import.


Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/genética , Proteínas de Ligação a DNA/metabolismo , Proteostase/genética , Transdução de Sinais , Arabidopsis/metabolismo , Proteínas de Arabidopsis/genética , Núcleo Celular/metabolismo , Cloroplastos/metabolismo , Cotilédone/genética , Cotilédone/metabolismo , Proteínas de Ligação a DNA/genética , Regulação da Expressão Gênica de Plantas , Transporte Proteico , Plântula/genética , Plântula/metabolismo
7.
Plant Physiol ; 181(4): 1615-1631, 2019 12.
Artigo em Inglês | MEDLINE | ID: mdl-31615849

RESUMO

Thylakoid membranes in land plant chloroplasts are organized into appressed and nonappressed membranes, which contribute to the control of energy distribution between the two photosystems (PSI and PSII) from the associated light-harvesting complexes (LHCs). Under fluctuating light conditions, fast reversible phosphorylation of the N-terminal thylakoid protein domains and changes in electrostatic forces induce modifications in thylakoid organization. To gain insight into the role and dynamics of thylakoid protein phosphorylation, we used targeted proteomics to quantify amounts of the structural proteins CURVATURE THYLAKOID1 (CURT1), including the levels of CURT1B N terminus phosphorylation and acetylation, after short-term fluctuating light treatments of Arabidopsis (Arabidopsis thaliana). The CURT1B protein was localized to a specific curvature domain separated from the margin domain, and specifically depleted of chlorophyll-binding protein complexes. The acetylation and phosphorylation of the CURT1B N terminus were mutually exclusive. The level of CURT1B phosphorylation, but not of acetylation, increased upon light shifts that also led to an increase in PSII core protein phosphorylation. These dynamics were largely absent in the knockout mutant of PSII core protein kinase SER/THR PROTEIN KINASE8 (STN8). Moreover, in mutants impaired in interaction between phosphorylated LHCII and PSI, the phosphorylation dynamics of CURT1B and the amount of the other CURT1 proteins were misregulated, indicating a functional interaction between CURT1B and PSI-LHCII complexes in grana margins. The complex relationships between phosphorylation of PSII, LHCII, and CURT1B support the dynamics of thylakoid protein complexes that are crucial in the optimization of photosynthesis under fluctuating light intensities.


Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/metabolismo , Proteínas de Ligação a DNA/metabolismo , Complexo de Proteína do Fotossistema I/metabolismo , Tilacoides/metabolismo , Acetilação , Alanina/metabolismo , Proteínas de Arabidopsis/química , Clorofila/metabolismo , Proteínas de Ligação a DNA/química , Luz , Complexos de Proteínas Captadores de Luz/metabolismo , Modelos Biológicos , Fosforilação , Fosfotreonina/metabolismo , Complexo de Proteína do Fotossistema I/química , Complexo de Proteína do Fotossistema II/metabolismo , Ligação Proteica , Isoformas de Proteínas/metabolismo , Subunidades Proteicas/metabolismo
8.
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
9.
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
10.
Free Radic Biol Med ; 134: 555-566, 2019 04.
Artigo em Inglês | MEDLINE | ID: mdl-30738155

RESUMO

Reactive oxygen species (ROS) are key signalling intermediates in plant metabolism, defence, and stress adaptation. In plants, both the chloroplast and mitochondria are centres of metabolic control and ROS production, which coordinate stress responses in other cell compartments. The herbicide and experimental tool, methyl viologen (MV) induces ROS generation in the chloroplast under illumination, but is also toxic in non-photosynthetic organisms. We used MV to probe plant ROS signalling in compartments other than the chloroplast. Taking a genetic approach in the model plant Arabidopsis (Arabidopsis thaliana), we used natural variation, QTL mapping, and mutant studies with MV in the light, but also under dark conditions, when the chloroplast electron transport is inactive. These studies revealed a light-independent MV-induced ROS-signalling pathway, suggesting mitochondrial involvement. Mitochondrial Mn SUPEROXIDE DISMUTASE was required for ROS-tolerance and the effect of MV was enhanced by exogenous sugar, providing further evidence for the role of mitochondria. Mutant and hormone feeding assays revealed roles for stress hormones in organellar ROS-responses. The radical-induced cell death1 mutant, which is tolerant to MV-induced ROS and exhibits altered mitochondrial signalling, was used to probe interactions between organelles. Our studies suggest that mitochondria are involved in the response to ROS induced by MV in plants.


Assuntos
Arabidopsis/metabolismo , Cloroplastos/metabolismo , Mitocôndrias/metabolismo , Estresse Oxidativo/efeitos dos fármacos , Paraquat/farmacologia , Arabidopsis/efeitos dos fármacos , Cloroplastos/efeitos dos fármacos , Transporte de Elétrons , Herbicidas/farmacologia , Mitocôndrias/efeitos dos fármacos , Espécies Reativas de Oxigênio/metabolismo , Transdução de Sinais
11.
Nat Plants ; 4(11): 910-919, 2018 11.
Artigo em Inglês | MEDLINE | ID: mdl-30374091

RESUMO

Photosystem I of the moss Physcomitrella patens has special properties, including the capacity to undergo non-photochemical fluorescence quenching. We studied the organization of photosystem I under different light and carbon supply conditions in wild-type moss and in moss with the lhcb9 (light-harvesting complex) knockout genotype, which lacks an antenna protein endowed with red-shifted absorption forms. Wild-type moss, when grown on sugars and in low light, accumulated LHCB9 proteins and a large form of the photosystem I supercomplex, which, besides the canonical four LHCI subunits, included a LHCII trimer and four additional LHC monomers. The lhcb9 knockout produced an angiosperm-like photosystem I supercomplex with four LHCI subunits irrespective of the growth conditions. Growth in the presence of sublethal concentrations of electron transport inhibitors that caused oxidation or reduction of the plastoquinone pool prevented or promoted, respectively, the accumulation of LHCB9 and the formation of the photosystem I megacomplex. We suggest that LHCB9 is a key subunit regulating the antenna size of photosystem I and the ability to avoid the over-reduction of plastoquinone: this condition is potentially dangerous in the shaded and sunfleck-rich environment typical of mosses, whose plastoquinone pool is reduced by both photosystem II and the oxidation of sugar substrates.


Assuntos
Bryopsida/metabolismo , Complexos de Proteínas Captadores de Luz/metabolismo , Complexo de Proteína do Fotossistema I/metabolismo , Bryopsida/efeitos da radiação , Luz , Complexos de Proteínas Captadores de Luz/efeitos da radiação , Complexos de Proteínas Captadores de Luz/ultraestrutura , Microscopia Eletrônica , Complexo de Proteína do Fotossistema I/efeitos da radiação , Complexo de Proteína do Fotossistema I/ultraestrutura , Complexo de Proteína do Fotossistema II/metabolismo , Proteômica , Tilacoides/metabolismo
12.
Plant Physiol Biochem ; 132: 356-362, 2018 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-30261469

RESUMO

Salicornia veneta (Pignatti et Lausi) is an extreme halophyte living in salt marsh where NaCl concentration may be as high as 1 M. Here we report on the isolation and characterization of a PSII preparation obtained by Triton X-100 solubilisation of the thylakoid membrane. By a combination of gel electrophoresis, immunoblotting and mass spectrometry, the depletion of a number of PSII proteins such as PsbQ, PsbM and PsbT was highlighted. Moreover, the requirement of Cl- and Ca2+ for optimal oxygen evolution was determined, showing that in absence of PsbQ a higher level of these ions are required. At high Cl- concentrations, oxygen evolution was inhibited in the same way in Salicornia veneta and spinach. Reconstitution of Salicornia veneta PSII preparation with partially purified spinach PsbP and PsbQ restored oxygen evolution activity at low Cl- and Ca2+ concentrations. Adaptation to high salt makes several PSII proteins dispensable.


Assuntos
Chenopodiaceae/metabolismo , Complexo de Proteína do Fotossistema II/isolamento & purificação , Complexo de Proteína do Fotossistema II/metabolismo , Plantas Tolerantes a Sal/metabolismo , Tilacoides/metabolismo , Cálcio/metabolismo , Cloretos/metabolismo , Oxigênio/análise , Proteínas de Plantas/metabolismo , Spinacia oleracea/metabolismo
13.
Physiol Plant ; 162(2): 162-176, 2018 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-28815615

RESUMO

Trans-methylation reactions are vital in basic metabolism, epigenetic regulation, RNA metabolism, and posttranslational control of protein function and therefore fundamental in determining the physiological processes in all living organisms. The plant kingdom is additionally characterized by the production of secondary metabolites that undergo specific hydroxylation, oxidation and methylation reactions to obtain a wide array of different chemical structures. Increasing research efforts have started to reveal the enzymatic pathways underlying the biosynthesis of complex metabolites in plants. Further engineering of these enzymatic machineries offers significant possibilities in the development of bio-based technologies, but necessitates deep understanding of their potential metabolic and regulatory interactions. Trans-methylation reactions are tightly coupled with the so-called activated methyl cycle (AMC), an essential metabolic circuit that maintains the trans-methylation capacity in all living cells. Tight regulation of the AMC is crucial in ensuring accurate trans-methylation reactions in different subcellular compartments, cell types, developmental stages and environmental conditions. This review addresses the organization and posttranslational regulation of the AMC and elaborates its critical role in determining metabolic regulation through modulation of methyl utilization in stress-exposed plants.


Assuntos
Proteínas de Plantas/metabolismo , Plantas/metabolismo , Processamento de Proteína Pós-Traducional , Sequência de Aminoácidos , Arabidopsis/genética , Arabidopsis/metabolismo , Metilação , Metiltransferases/genética , Metiltransferases/metabolismo , Modelos Biológicos , Proteínas de Plantas/genética , Plantas/genética , S-Adenosil-Homocisteína/metabolismo , S-Adenosilmetionina/metabolismo
14.
Plant Direct ; 2(11): e00093, 2018 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31245694

RESUMO

Linear electron transport in the thylakoid membrane drives photosynthetic NADPH and ATP production, while cyclic electron flow (CEF) around photosystem I only promotes the translocation of protons from stroma to thylakoid lumen. The chloroplast NADH dehydrogenase-like complex (NDH) participates in one CEF route transferring electrons from ferredoxin back to the plastoquinone pool with concomitant proton pumping to the lumen. CEF has been proposed to balance the ratio of ATP/NADPH production and to control the redox poise particularly in fluctuating light conditions, but the mechanisms regulating the NDH complex remain unknown. We have investigated potential regulation of the CEF pathways by the chloroplast NADPH-thioredoxin reductase (NTRC) in vivo by using an Arabidopsis knockout line of NTRC as well as lines overexpressing NTRC. Here, we present biochemical and biophysical evidence showing that NTRC stimulates the activity of NDH-dependent CEF and is involved in the regulation of generation of proton motive force, thylakoid conductivity to protons, and redox balance between the thylakoid electron transfer chain and the stroma during changes in light conditions. Furthermore, protein-protein interaction assays suggest a putative thioredoxin-target site in close proximity to the ferredoxin-binding domain of NDH, thus providing a plausible mechanism for redox regulation of the NDH ferredoxin:plastoquinone oxidoreductase activity.

15.
J Exp Bot ; 68(15): 4281-4293, 2017 07 10.
Artigo em Inglês | MEDLINE | ID: mdl-28922769

RESUMO

On Earth, solar irradiance varies as the sun rises and sets over the horizon, and sunlight is thus in constant fluctuation, following a slow dark-low-high-low-dark curve. Optimal plant growth and development are dependent on the capacity of plants to acclimate and regulate photosynthesis in response to these changes of light. Little is known of regulative processes for photosynthesis during nocturnal events. The nucleus-encoded plant lineage-specific protein PSB33 has been described as stabilizing the photosystem II complex, especially under light stress conditions, and plants lacking PSB33 have a dysfunctional state transition. To clarify the localization and function of this protein, we used phenomic, biochemical and proteomics approaches in the model plant Arabidopsis. We report that PSB33 is predominantly located in non-appressed thylakoid regions and dynamically associates with a thylakoid protein complex in a light-dependent manner. Moreover, plants lacking PSB33 show an accelerated D1 protein degradation in nocturnal periods, and show severely stunted growth when challenged with fluctuating light. We further show that the function of PSB33 precedes the STN7 kinase to regulate or balance the excitation energy of photosystems I and II in fluctuating light conditions.


Assuntos
Aclimatação , Proteínas de Arabidopsis/fisiologia , Arabidopsis/fisiologia , Luz , Fotossíntese , Complexo de Proteína do Fotossistema II/fisiologia , Arabidopsis/genética , Proteínas de Arabidopsis/genética , Complexo de Proteína do Fotossistema II/genética
16.
Plant J ; 89(1): 112-127, 2017 01.
Artigo em Inglês | MEDLINE | ID: mdl-27598402

RESUMO

Glucosinolates (GSL) of cruciferous plants comprise a major group of structurally diverse secondary compounds which act as deterrents against aphids and microbial pathogens and have large commercial and ecological impacts. While the transcriptional regulation governing the biosynthesis and modification of GSL is now relatively well understood, post-translational regulatory components that specifically determine the structural variation of indole glucosinolates have not been reported. We show that the cytoplasmic protein phosphatase 2A regulatory subunit B'γ (PP2A-B'γ) physically interacts with indole glucosinolate methyltransferases and controls the methoxylation of indole glucosinolates and the formation of 4-methoxy-indol-3-yl-methyl glucosinolate in Arabidopsis leaves. By taking advantage of proteomic approaches and metabolic analysis we further demonstrate that PP2A-B'γ is required to control the abundance of oligomeric protein complexes functionally linked with the activated methyl cycle and the trans-methylation capacity of leaf cells. These findings highlight the key regulatory role of PP2A-B'γ in methionine metabolism and provide a previously unrecognized perspective for metabolic engineering of glucosinolate metabolism in cruciferous plants.


Assuntos
Proteínas de Arabidopsis/metabolismo , Glucosinolatos/metabolismo , Folhas de Planta/metabolismo , Proteína Fosfatase 2/metabolismo , Sequência de Aminoácidos , Arabidopsis/genética , Arabidopsis/metabolismo , Proteínas de Arabidopsis/genética , Metionina/metabolismo , Metilação , Metiltransferases/genética , Metiltransferases/metabolismo , Modelos Biológicos , Folhas de Planta/genética , Ligação Proteica , Proteína Fosfatase 2/genética , Subunidades Proteicas/genética , Subunidades Proteicas/metabolismo , Proteômica/métodos , Homologia de Sequência de Aminoácidos
17.
Plant J ; 87(5): 484-94, 2016 09.
Artigo em Inglês | MEDLINE | ID: mdl-27214592

RESUMO

STN7 kinase catalyzes the phosphorylation of the globally most common membrane proteins, the light-harvesting complex II (LHCII) in plant chloroplasts. STN7 itself possesses one serine (Ser) and two threonine (Thr) phosphosites. We show that phosphorylation of the Thr residues protects STN7 against degradation in darkness, low light and red light, whereas increasing light intensity and far red illumination decrease phosphorylation and induce STN7 degradation. Ser phosphorylation, in turn, occurs under red and low intensity white light, coinciding with the client protein (LHCII) phosphorylation. Through analysis of the counteracting LHCII phosphatase mutant tap38/pph1, we show that Ser phosphorylation and activation of the STN7 kinase for subsequent LHCII phosphorylation are heavily affected by pre-illumination conditions. Transitions between the three activity states of the STN7 kinase (deactivated in darkness and far red light, activated in low and red light, inhibited in high light) are shown to modulate the phosphorylation of the STN7 Ser and Thr residues independently of each other. Such dynamic regulation of STN7 kinase phosphorylation is crucial for plant growth and environmental acclimation.


Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/metabolismo , Luz , Proteínas Serina-Treonina Quinases/metabolismo , Serina/metabolismo , Treonina/metabolismo , Arabidopsis/genética , Arabidopsis/efeitos da radiação , Proteínas de Arabidopsis/genética , Fosforilação , Proteínas Serina-Treonina Quinases/genética
19.
Plant J ; 84(2): 360-73, 2015 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-26332430

RESUMO

Thylakoid energy metabolism is crucial for plant growth, development and acclimation. Non-appressed thylakoids harbor several high molecular mass pigment-protein megacomplexes that have flexible compositions depending upon the environmental cues. This composition is important for dynamic energy balancing in photosystems (PS) I and II. We analysed the megacomplexes of Arabidopsis wild type (WT) plants and of several thylakoid regulatory mutants. The stn7 mutant, which is defective in phosphorylation of the light-harvesting complex (LHC) II, possessed a megacomplex composition that was strikingly different from that of the WT. Of the nine megacomplexes in total for the non-appressed thylakoids, the largest megacomplex in particular was less abundant in the stn7 mutant under standard growth conditions. This megacomplex contains both PSI and PSII and was recently shown to allow energy spillover between PSII and PSI (Nat. Commun., 6, 2015, 6675). The dynamics of the megacomplex composition was addressed by exposing plants to different light conditions prior to thylakoid isolation. The megacomplex pattern in the WT was highly dynamic. Under darkness or far red light it showed low levels of LHCII phosphorylation and resembled the stn7 pattern; under low light, which triggers LHCII phosphorylation, it resembled that of the tap38/pph1 phosphatase mutant. In contrast, solubilization of the entire thylakoid network with dodecyl maltoside, which efficiently solubilizes pigment-protein complexes from all thylakoid compartments, revealed that the pigment-protein composition remained stable despite the changing light conditions or mutations that affected LHCII (de)phosphorylation. We conclude that the composition of pigment-protein megacomplexes specifically in non-appressed thylakoids undergoes redox-dependent changes, thus facilitating maintenance of the excitation balance between the two photosystems upon changes in light conditions.


Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/metabolismo , Luz , Tilacoides/metabolismo , Aclimatação/efeitos da radiação , Arabidopsis/efeitos da radiação , Complexos de Proteínas Captadores de Luz/metabolismo , Complexo de Proteína do Fotossistema I/metabolismo , Complexo de Proteína do Fotossistema II/metabolismo , Tilacoides/efeitos da radiação
20.
Plant Cell Environ ; 38(12): 2641-51, 2015 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-26012558

RESUMO

Plants survive periods of unfavourable conditions with the help of sensory mechanisms that respond to reactive oxygen species (ROS) as signalling molecules in different cellular compartments. We have previously demonstrated that protein phosphatase 2A (PP2A) impacts on organellar cross-talk and associated pathogenesis responses in Arabidopsis thaliana. This was evidenced by drastically enhanced pathogenesis responses and cell death in cat2 pp2a-b'γ double mutants, deficient in the main peroxisomal antioxidant enzyme CATALASE 2 and PP2A regulatory subunit B'γ (PP2A-B'γ). In the present paper, we explored the impacts of PP2A-B'γ and a highly similar regulatory subunit PP2A-B'ζ in growth regulation and light stress tolerance in Arabidopsis. PP2A-B'γ and PP2A-B'ζ display high promoter activities in rapidly growing tissues and are required for optimal growth under favourable conditions. Upon acclimation to a combination of high light, elevated temperature and reduced availability of water, however, pp2a-b'γζ double mutants grow similarly to the wild type and show enhanced tolerance against photo-oxidative stress. We conclude that by controlling ROS homeostasis and signalling, PP2A-B'γ and PP2A-B'ζ may direct acclimation strategies upon environmental perturbations, hence acting as important determinants of defence responses and light acclimation in plants.


Assuntos
Arabidopsis/enzimologia , Proteína Fosfatase 2/metabolismo , Subunidades Proteicas , Aclimatação , Arabidopsis/genética , Arabidopsis/fisiologia , Arabidopsis/efeitos da radiação , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Perfilação da Expressão Gênica , Genes Reporter , Homeostase , Luz , Mutação , Estresse Oxidativo , Fosforilação , Folhas de Planta/enzimologia , Folhas de Planta/genética , Folhas de Planta/fisiologia , Folhas de Planta/efeitos da radiação , Plantas Geneticamente Modificadas , Regiões Promotoras Genéticas/genética , Proteína Fosfatase 2/genética , Espécies Reativas de Oxigênio/metabolismo , Plântula/enzimologia , Plântula/genética , Plântula/fisiologia , Plântula/efeitos da radiação , Estresse Fisiológico
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...