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1.
J Hazard Mater ; 477: 135164, 2024 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-39032180

RESUMO

Cadmium (Cd) is one of the most toxic heavy metals for plants and humans. Reactive oxygen species (ROS) are some of the primary signaling molecules produced after Cd treatment in plants but the contribution of different organelles and specific cell types, together with the impact of light is unknown. We used Arabidopsis lines expressing GRX1-roGFP2 (glutaredoxin1-roGFP) targeted to different cell compartments and analysed changes in redox state over 24 h light/dark cycle in Cd-treated leaf discs. We imaged redox state changes in peroxisomes and chloroplasts in leaf tissue. Chloroplasts and peroxisomes were the most affected organelles in the dark and blocking the photosynthetic electron transport chain (pETC) by DCMU (3-(3,4-dichlorophenyl)-1,1-dimethylurea) promotes higher Cd-dependent oxidation in all organelles. Peroxisomes underwent the most rapid changes in redox state in response to Cd and DCMU and silencing chloroplastic NTRC (NADPH thioredoxin reductase C) considerably increases peroxisome oxidation. Total NAD(P)H and cytosolic NADH decreased during exposure to Cd, while Ca+2 content in chloroplasts and cytosol increased in the dark period. Our results demonstrate a Cd-, time- and light-dependent increase of oxidation of all organelles analysed, that could be in part triggered by disturbances in pETC and photorespiration, the decrease of NAD(P)H availability, and differential antioxidants expression at subcellular level.


Assuntos
Arabidopsis , Cádmio , Cloroplastos , Oxirredução , Peroxissomos , Arabidopsis/efeitos dos fármacos , Arabidopsis/metabolismo , Arabidopsis/efeitos da radiação , Cádmio/toxicidade , Cloroplastos/metabolismo , Cloroplastos/efeitos dos fármacos , Cloroplastos/efeitos da radiação , Peroxissomos/metabolismo , Peroxissomos/efeitos dos fármacos , Luz , Folhas de Planta/efeitos dos fármacos , Folhas de Planta/metabolismo , Folhas de Planta/efeitos da radiação , Cálcio/metabolismo , Diurona/toxicidade , Diurona/farmacologia
2.
Nat Commun ; 13(1): 652, 2022 02 03.
Artigo em Inglês | MEDLINE | ID: mdl-35115512

RESUMO

Stomatal opening requires the provision of energy in the form of ATP for proton pumping across the guard cell (GC) plasma membrane and for associated metabolic rearrangements. The source of ATP for GCs is a matter of ongoing debate that is mainly fuelled by controversies around the ability of GC chloroplasts (GCCs) to perform photosynthesis. By imaging compartment-specific fluorescent ATP and NADPH sensor proteins in Arabidopsis, we show that GC photosynthesis is limited and mitochondria are the main source of ATP. Unlike mature mesophyll cell (MC) chloroplasts, which are impermeable to cytosolic ATP, GCCs import cytosolic ATP through NUCLEOTIDE TRANSPORTER (NTT) proteins. GCs from ntt mutants exhibit impaired abilities for starch biosynthesis and stomatal opening. Our work shows that GCs obtain ATP and carbohydrates via different routes from MCs, likely to compensate for the lower chlorophyll contents and limited photosynthesis of GCCs.


Assuntos
Trifosfato de Adenosina/metabolismo , Arabidopsis/metabolismo , Cloroplastos/metabolismo , Estômatos de Plantas/metabolismo , Amido/metabolismo , Arabidopsis/citologia , Arabidopsis/genética , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Transporte Biológico , Cloroplastos/efeitos dos fármacos , Cloroplastos/efeitos da radiação , Citosol/metabolismo , Peróxido de Hidrogênio/farmacologia , Luz , Células do Mesofilo/citologia , Células do Mesofilo/metabolismo , Células do Mesofilo/efeitos da radiação , Microscopia Confocal , NADP/metabolismo , Proteínas de Transporte de Nucleotídeos/genética , Proteínas de Transporte de Nucleotídeos/metabolismo , Oxidantes/farmacologia , Epiderme Vegetal/citologia , Epiderme Vegetal/metabolismo , Folhas de Planta/citologia , Folhas de Planta/metabolismo , Estômatos de Plantas/citologia , Estômatos de Plantas/fisiologia , Plantas Geneticamente Modificadas
3.
Plant Sci ; 312: 111046, 2021 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-34620444

RESUMO

Barren stalks and kernel abortion are the major obstacles that hinder maize production. After many years of inbreeding, our group produced a pair of barren stalk/non-barren stalk near-isogenic lines SN98A/SN98B. Under weak light stress, the barren stalk rate is up to 98 % in SN98A but zero in SN98B. Therefore, we consider that SN98A is a weak light-sensitive inbred line whereas SN98B is insensitive. In the present study, the near-isogenic lines SN98A/SN98B were used as test materials to conduct cytological and photosynthetic physiological analyses of the physiological mechanism associated with the differences in maize barren stalk induced by weak light stress. The results showed that weak light stress increased the accumulation of reactive oxygen species (ROS), decreased the function of chloroplasts, destroyed the normal rosette structure, inhibited photosynthetic electron transport, and enhanced lipid peroxidation. The actual photochemical quantum efficiency for PSI (Y(I)) and PSII (Y(II)), relative electron transfer rate for PSI (ETR(I)) and PSII (ETR(II)), and the P700 activities decreased significantly in the leaves of SN98A and SN98B under weak light stress, where the decreases were greater in SN98A than SN98B. After 10 days of shading treatment, the O2·- production rate, H2O2 contents, the yield of regulated energy dissipation (Y(NPQ)), the donor side restriction for PSI (Y(ND)) and the quantum efficiency of cyclic electron flow photochemistry were always higher in SN98A than SN98B, and the antioxidant enzyme activities were always lower in SN98A than those in SN98B. These results show that SN98B has a stronger ability to remove ROS at its source, and maintain the integrity of the structure and function of the photosynthetic system. This self-protection mechanism is an important physiological reason for its adaptation to weak light.


Assuntos
Adaptação Ocular/genética , Adaptação Ocular/efeitos da radiação , Fotossíntese/efeitos da radiação , Caules de Planta/crescimento & desenvolvimento , Caules de Planta/efeitos da radiação , Energia Solar , Zea mays/genética , Zea mays/efeitos da radiação , Diferenciação Celular/genética , Diferenciação Celular/efeitos da radiação , Cloroplastos/genética , Cloroplastos/efeitos da radiação , Produtos Agrícolas/crescimento & desenvolvimento , Produtos Agrícolas/efeitos da radiação , Transporte de Elétrons/genética , Transporte de Elétrons/efeitos da radiação , Variação Genética , Genótipo , Fotossíntese/genética , Zea mays/crescimento & desenvolvimento
4.
Plant Cell ; 33(5): 1828-1844, 2021 07 02.
Artigo em Inglês | MEDLINE | ID: mdl-33624811

RESUMO

Plants are subjected to fluctuations in light intensity, and this might cause unbalanced photosynthetic electron fluxes and overproduction of reactive oxygen species (ROS). Electrons needed for ROS detoxification are drawn, at least partially, from the cellular glutathione (GSH) pool via the ascorbate-glutathione cycle. Here, we explore the dynamics of the chloroplastic glutathione redox potential (chl-EGSH) using high-temporal-resolution monitoring of Arabidopsis (Arabidopsis thaliana) lines expressing the reduction-oxidation sensitive green fluorescent protein 2 (roGFP2) in chloroplasts. This was carried out over several days under dynamic environmental conditions and in correlation with PSII operating efficiency. Peaks in chl-EGSH oxidation during dark-to-light and light-to-dark transitions were observed. Increasing light intensities triggered a binary oxidation response, with a threshold around the light saturating point, suggesting two regulated oxidative states of the chl-EGSH. These patterns were not affected in npq1 plants, which are impaired in non-photochemical quenching. Oscillations between the two oxidation states were observed under fluctuating light in WT and npq1 plants, but not in pgr5 plants, suggesting a role for PSI photoinhibition in regulating the chl-EGSH dynamics. Remarkably, pgr5 plants showed an increase in chl-EGSH oxidation during the nights following light stresses, linking daytime photoinhibition and nighttime GSH metabolism. This work provides a systematic view of the dynamics of the in vivo chloroplastic glutathione redox state during varying light conditions.


Assuntos
Arabidopsis/fisiologia , Cloroplastos/metabolismo , Ritmo Circadiano/fisiologia , Glutationa/metabolismo , Fotossíntese/fisiologia , Arabidopsis/efeitos da radiação , Proteínas de Arabidopsis/metabolismo , Cloroplastos/efeitos da radiação , Ritmo Circadiano/efeitos da radiação , Transporte de Elétrons/efeitos da radiação , Luz , Oxirredução/efeitos da radiação , Fotossíntese/efeitos da radiação , Complexo de Proteínas do Centro de Reação Fotossintética/metabolismo , Complexo de Proteína do Fotossistema I/metabolismo , Complexo de Proteína do Fotossistema II/metabolismo
5.
ACS Appl Mater Interfaces ; 12(18): 21009-21019, 2020 May 06.
Artigo em Inglês | MEDLINE | ID: mdl-32281782

RESUMO

Sunlight utilization by plants via the photosynthesis process is limited to the visible spectral range. How to expand the utilization spectral range via construction of a hybrid photosynthetic system is a hot topic in this field. In this work, far-red carbon dots (FR-CDs) with excellent water solubility, good biocompatibility, high quantum yield (QY), and superior stability were prepared by a one-step microwave synthesis in 3 min. The as-prepared FR-CDs is an efficient converter transferring ultraviolet A (UV-A) light to 625-800 nm far-red emission, which can be directly absorbed and utilized by chloroplasts. Due to the broader spectral utilization of solar energy and Emerson effect, increased photosynthetic activity can be achieved both in vivo and in vitro when applied for Roman lettuce. The in vitro hybrid photosynthetic system via coating chloroplasts with FR-CDs presents higher electron transfer efficiency between PS II (photosystem II) to PS I (photosystem I), which consequently increases the ATP production. The in vivo experiment further confirms that FR-CDs-treated lettuce can induce a 28.00% higher electron transfer rate compared with the control group, which results in 51.14 and 24.60% enhancement of fresh and dry weights, respectively. This work is expected to provide a way for improving the conversion efficiency from solar energy to chemical energy. (PS II) to photosystem I (PS I), which consequently increases the ATP production. The in vivo experiment further confirms that FR-CDs-treated lettuce can induce a 28.00% higher electron transfer rate compared with the control group, which results in 51.14 and 24.60% enhancement of fresh and dry weights, respectively. This work is expected to provide a way for improving the conversion efficiency from solar energy to chemical energy.


Assuntos
Cloroplastos/metabolismo , Fotossíntese/fisiologia , Pontos Quânticos/química , Trifosfato de Adenosina/metabolismo , Carbono/química , Cloroplastos/efeitos da radiação , Lactuca/metabolismo , Oxigênio/metabolismo , Fotossíntese/efeitos da radiação , Complexo de Proteína do Fotossistema I/metabolismo , Complexo de Proteína do Fotossistema II/metabolismo , Proteínas de Plantas/metabolismo , Pontos Quânticos/efeitos da radiação , Raios Ultravioleta
6.
Plant Physiol ; 182(1): 424-435, 2020 01.
Artigo em Inglês | MEDLINE | ID: mdl-31636102

RESUMO

Acclimation to changing light intensities poses major challenges to plant metabolism and has been shown to involve regulatory adjustments in chloroplast gene expression. However, this regulation has not been examined at a plastid genome-wide level and for many genes, it is unknown whether their expression responds to altered light intensities. Here, we applied comparative ribosome profiling and transcriptomic experiments to analyze changes in chloroplast transcript accumulation and translation in leaves of tobacco (Nicotiana tabacum) seedlings after transfer from moderate light to physiological high light. Our time-course data revealed almost unaltered chloroplast transcript levels and only mild changes in ribosome occupancy during 2 d of high light exposure. Ribosome occupancy on the psbA mRNA (encoding the D1 reaction center protein of PSII) increased and that on the petG transcript decreased slightly after high light treatment. Transfer from moderate light to high light did not induce substantial alterations in ribosome pausing. Transfer experiments from low light to high light conditions resulted in strong PSII photoinhibition and revealed the distinct light-induced activation of psbA translation, which was further confirmed by reciprocal shift experiments. In low-light-to-high-light shift experiments, as well as reciprocal treatments, the expression of all other chloroplast genes remained virtually unaltered. Altogether, our data suggest that low light-acclimated plants upregulate the translation of a single chloroplast gene, psbA, during acclimation to high light. Our results indicate that psbA translation activation occurs already at moderate light intensities. Possible reasons for the otherwise mild effects of light intensity changes on gene expression in differentiated chloroplasts are discussed.


Assuntos
Cloroplastos/metabolismo , Luz , Nicotiana/metabolismo , Cloroplastos/efeitos da radiação , Complexo de Proteína do Fotossistema II/metabolismo , RNA Mensageiro/metabolismo , Ribossomos/metabolismo , Ribossomos/efeitos da radiação , Nicotiana/efeitos da radiação
7.
Plant Cell ; 31(12): 3057-3072, 2019 12.
Artigo em Inglês | MEDLINE | ID: mdl-31591163

RESUMO

Intracellular processes can be localized for efficiency or regulation. For example, localized mRNA translation by chloroplastic ribosomes occurs in the biogenesis of PSII, one of the two photosystems of the photosynthetic electron transport chain in the chloroplasts of plants and algae. The biogenesis of PSI and PSII requires the synthesis and assembly of their constituent polypeptide subunits, pigments, and cofactors. Although these biosynthetic pathways are well characterized, less is known about when and where they occur in developing chloroplasts. Here, we used fluorescence microscopy in the unicellular alga Chlamydomonas reinhardtii to reveal spatiotemporal organization in photosystem biogenesis. We focused on translation by chloroplastic ribosomes and chlorophyll biosynthesis in two developmental contexts of active photosystem biogenesis: (1) growth of the mature chloroplast and (2) greening of a nonphotosynthetic chloroplast. The results reveal that a translation zone is the primary location of the biogenesis of PSI and PSII. This discretely localized region within the chloroplast contrasts with the distributions of photosystems throughout this organelle and, therefore, is likely a hub where anabolic pathways converge for photosystem biogenesis.plantcell;31/12/3057/FX1F1fx1.


Assuntos
Chlamydomonas reinhardtii/metabolismo , Chlamydomonas/metabolismo , Cloroplastos/metabolismo , Complexo de Proteína do Fotossistema II/metabolismo , Biossíntese de Proteínas/fisiologia , Ribossomos/metabolismo , Chlamydomonas/genética , Chlamydomonas reinhardtii/citologia , Chlamydomonas reinhardtii/genética , Clorofila/biossíntese , Cloroplastos/efeitos da radiação , Mitose/genética , Fotossíntese , Complexo de Proteína do Fotossistema I/metabolismo , Complexo de Proteína do Fotossistema II/genética , Biossíntese de Proteínas/genética , Biossíntese de Proteínas/efeitos da radiação , RNA Mensageiro/genética , Tilacoides/metabolismo
8.
Plant Physiol ; 180(4): 1947-1961, 2019 08.
Artigo em Inglês | MEDLINE | ID: mdl-31213510

RESUMO

Key aspects of leaf mitochondrial metabolism in the light remain unresolved. For example, there is debate about the relative importance of exporting reducing equivalents from mitochondria for the peroxisomal steps of photorespiration versus oxidation of NADH to generate ATP by oxidative phosphorylation. Here, we address this and explore energetic coupling between organelles in the light using a diel flux balance analysis model. The model included more than 600 reactions of central metabolism with full stoichiometric accounting of energy production and consumption. Different scenarios of energy availability (light intensity) and demand (source leaf versus a growing leaf) were considered, and the model was constrained by the nonlinear relationship between light and CO2 assimilation rate. The analysis demonstrated that the chloroplast can theoretically generate sufficient ATP to satisfy the energy requirements of the rest of the cell in addition to its own. However, this requires unrealistic high light use efficiency and, in practice, the availability of chloroplast-derived ATP is limited by chloroplast energy dissipation systems, such as nonphotochemical quenching, and the capacity of the chloroplast ATP export shuttles. Given these limitations, substantial mitochondrial ATP synthesis is required to fulfill cytosolic ATP requirements, with only minimal, or zero, export of mitochondrial reducing equivalents. The analysis also revealed the importance of exporting reducing equivalents from chloroplasts to sustain photorespiration. Hence, the chloroplast malate valve and triose phosphate-3-phosphoglycerate shuttle are predicted to have important metabolic roles, in addition to their more commonly discussed contribution to the avoidance of photooxidative stress.


Assuntos
Cloroplastos/metabolismo , Cloroplastos/efeitos da radiação , Luz , Mitocôndrias/metabolismo , Mitocôndrias/efeitos da radiação , Folhas de Planta/metabolismo , Folhas de Planta/efeitos da radiação , Trifosfato de Adenosina/metabolismo , Transporte de Elétrons/efeitos da radiação , Metabolismo Energético/efeitos da radiação , Malatos/metabolismo , Modelos Biológicos , NADP/metabolismo
9.
Physiol Plant ; 167(2): 188-204, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-30467859

RESUMO

Research has begun to elucidate the signal transduction pathway(s) that control cellular responses to changes in mitochondrial status. Important tools in such studies are chemical inhibitors used to initiate mitochondrial dysfunction. This study compares the effect of different inhibitors and treatment conditions on the transcript amount of nuclear genes specifically responsive to mitochondrial dysfunction in leaf of Nicotiana tabacum L. cv. Petit Havana. The Complex III inhibitors antimycin A (AA) and myxothiazol (MYXO), and the Complex V inhibitor oligomycin (OLIGO), each increased the transcript amount of the mitochondrial dysfunction genes. Transcript responses to OLIGO were greater during treatment in the dark than in the light, and the dark treatment resulted in cell death. In the dark, transcript responses to AA and MYXO were similar to one another, despite MYXO leading to cell death. In the light, transcript responses to AA and MYXO diverged, despite cell viability remaining high with either inhibitor. This divergent response may be due to differential signaling from the chloroplast because only AA also inhibited cyclic electron transport, resulting in a strong acceptor-side limitation in photosystem I. In the light, chemical inhibition of chloroplast electron transport reduced transcript responses to AA, while having no effect on the response to MYXO, and increasing the response to OLIGO. Hence, when studying mitochondrial dysfunction signaling, different inhibitor and treatment combinations differentially affect linked processes (e.g. chloroplast function and cell fate) that then contribute to measured responses. Therefore, inhibitor and treatment conditions should be chosen to align with specific study goals.


Assuntos
Cloroplastos/metabolismo , Mitocôndrias/metabolismo , Nicotiana/genética , Transdução de Sinais , Antimicina A/farmacologia , Cloroplastos/efeitos da radiação , Transporte de Elétrons/efeitos dos fármacos , Complexo III da Cadeia de Transporte de Elétrons/antagonistas & inibidores , Luz , Metacrilatos/farmacologia , Mitocôndrias/efeitos da radiação , ATPases Mitocondriais Próton-Translocadoras/antagonistas & inibidores , Oligomicinas/farmacologia , Complexo de Proteína do Fotossistema I/efeitos dos fármacos , Complexo de Proteína do Fotossistema I/genética , Complexo de Proteína do Fotossistema I/metabolismo , Folhas de Planta/genética , Folhas de Planta/fisiologia , Folhas de Planta/efeitos da radiação , Tiazóis/farmacologia , Nicotiana/fisiologia , Nicotiana/efeitos da radiação
10.
FEBS Lett ; 592(18): 3111-3115, 2018 09.
Artigo em Inglês | MEDLINE | ID: mdl-30076598

RESUMO

In order to maintain enzyme stability and activity, chloroplasts use two systems of thiol-disulfide reductases for the control of redox-dependent properties of proteins. Previous studies have revealed that plastid-localized thioredoxins (TRX) and the NADPH-dependent thioredoxin reductase C (NTRC) are important for the reduction of cysteine residues of enzymes involved in chlorophyll synthesis. Very recently, it was shown that the pale green phenotype of the ntrc mutant is suppressed when the contents of 2-cysteine peroxiredoxins (2CP) A and B are decreased. Here, we show that suppression of the ntrc phenotype results from a recovery of wild-type-like redox control of chlorophyll biosynthesis enzymes in ntrc/2cp mutants. The presented results support the conclusion that TRXs rather than NTRC are the predominant reductases mediating the redox-regulation of these enzymes.


Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/metabolismo , Clorofila/biossíntese , Tiorredoxinas/metabolismo , Arabidopsis/genética , Arabidopsis/efeitos da radiação , Proteínas de Arabidopsis/genética , Cloroplastos/genética , Cloroplastos/metabolismo , Cloroplastos/efeitos da radiação , Luz , Mutação , Fotossíntese/genética , Fotossíntese/efeitos da radiação , Plântula/genética , Plântula/metabolismo , Plântula/efeitos da radiação , Tiorredoxina Dissulfeto Redutase/genética , Tiorredoxina Dissulfeto Redutase/metabolismo , Tiorredoxinas/genética
11.
Sci Rep ; 8(1): 6097, 2018 04 17.
Artigo em Inglês | MEDLINE | ID: mdl-29666396

RESUMO

Plants utilize energy from sunlight to perform photosynthesis in chloroplast, an organelle that could be damaged by solar UV radiation. The ultraviolet-B (UV-B) photoreceptor UVR8 is required for UV-B perception and signal transduction. However, little is known about how UVR8 influence chloroplast development under UV-B radiation. Here, we characterized tomato UVR8 gene (SlUVR8) and our results indicated that SlUVR8 facilitate plant acclimation to UV-B stress by orchestrating expression of the UVB-responsive genes (HY5 and CHS) and accumulating UV-absorptive compounds. In addition, we also discovered that SlUVR8 promotes fruit chloroplast development through enhancing accumulation of transcription factor GOLDEN2-LIKE2 (SlGLK2) which determines chloroplast and chlorophyll levels. Furthermore, UV-B radiation could increase expression of SlGLK2 and its target genes in fruits and leaves. SlUVR8 is required for UVB-induced SlGLK2 expression. Together, our work not only identified the conserved functions of SlUVR8 gene in response to UV-B stress, but also uncovered a novel role that SlUVR8 could boost chloroplast development by accumulating SlGLK2 proteins.


Assuntos
Regulação da Expressão Gênica de Plantas/efeitos da radiação , Fotorreceptores de Plantas/genética , Proteínas de Plantas/genética , Solanum lycopersicum/genética , Fatores de Transcrição/genética , Raios Ultravioleta/efeitos adversos , Aclimatação , Cloroplastos/genética , Cloroplastos/metabolismo , Cloroplastos/efeitos da radiação , Frutas/genética , Frutas/crescimento & desenvolvimento , Frutas/metabolismo , Frutas/efeitos da radiação , Solanum lycopersicum/crescimento & desenvolvimento , Solanum lycopersicum/metabolismo , Solanum lycopersicum/efeitos da radiação , Fotorreceptores de Plantas/metabolismo , Fotossíntese , Proteínas de Plantas/metabolismo , Fatores de Transcrição/metabolismo
13.
Plant Physiol ; 176(1): 596-610, 2018 01.
Artigo em Inglês | MEDLINE | ID: mdl-29150559

RESUMO

Iron (Fe) is an essential element for plants, utilized in nearly every cellular process. Because the adjustment of uptake under Fe limitation cannot satisfy all demands, plants need to acclimate their physiology and biochemistry, especially in their chloroplasts, which have a high demand for Fe. To investigate if a program exists for the utilization of Fe under deficiency, we analyzed how hydroponically grown Arabidopsis (Arabidopsis thaliana) adjusts its physiology and Fe protein composition in vegetative photosynthetic tissue during Fe deficiency. Fe deficiency first affected photosynthetic electron transport with concomitant reductions in carbon assimilation and biomass production when effects on respiration were not yet significant. Photosynthetic electron transport function and protein levels of Fe-dependent enzymes were fully recovered upon Fe resupply, indicating that the Fe depletion stress did not cause irreversible secondary damage. At the protein level, ferredoxin, the cytochrome-b6f complex, and Fe-containing enzymes of the plastid sulfur assimilation pathway were major targets of Fe deficiency, whereas other Fe-dependent functions were relatively less affected. In coordination, SufA and SufB, two proteins of the plastid Fe-sulfur cofactor assembly pathway, were also diminished early by Fe depletion. Iron depletion reduced mRNA levels for the majority of the affected proteins, indicating that loss of enzyme was not just due to lack of Fe cofactors. SufB and ferredoxin were early targets of transcript down-regulation. The data reveal a hierarchy for Fe utilization in photosynthetic tissue and indicate that a program is in place to acclimate to impending Fe deficiency.


Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/metabolismo , Deficiências de Ferro , Arabidopsis/efeitos da radiação , Proteínas de Arabidopsis/genética , Carbono/metabolismo , Dióxido de Carbono/metabolismo , Clorofila/metabolismo , Cloroplastos/metabolismo , Cloroplastos/efeitos da radiação , Transporte de Elétrons/efeitos da radiação , Regulação da Expressão Gênica de Plantas/efeitos da radiação , Ferro/metabolismo , Luz , Fotossíntese/efeitos da radiação , Folhas de Planta/fisiologia , Folhas de Planta/efeitos da radiação , RNA Mensageiro/genética , RNA Mensageiro/metabolismo
14.
Plant J ; 91(6): 995-1014, 2017 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-28644561

RESUMO

The integration of redox- and reactive oxygen species-dependent signaling and metabolic activities is fundamental to plant acclimation to biotic and abiotic stresses. Previous data suggest the existence of a dynamically interacting module in the chloroplast stroma consisting of cyclophilin 20-3 (Cyp20-3), O-acetylserine(thiol)lyase B (OASTL-B), 2-cysteine peroxiredoxins A/B (2-CysPrx) and serine acetyltransferase 2;1 (SERAT2;1). The functionality of this COPS module is influenced by redox stimuli and oxophytodienoic acid (OPDA), which is the precursor for jasmonic acid. The concept of an integrating function of these proteins in stress signaling was challenged by combining transcriptome and biochemical analyses in Arabidopsis mutants devoid of oastlB, serat2;1, cyp20-3 and 2-cysprxA/B, and wild-type (WT). Leaf transcriptomes were analyzed 6 h after transfer to light intensity 10-fold in excess of growth light or under growth light. The survey of KEGG-based gene ontology groups showed common upregulation of translation- and protein homeostasis-associated transcripts under control conditions in all mutants compared with WT. The results revealed that the interference of the module was accompanied with disturbance of carbohydrate, sulfur and nitrogen metabolism, and also citric acid cycle intermediates. Apart from common regulation, specific responses at the transcriptome and metabolite level linked Cyp20-3 to cell wall-bound carbohydrates and oxylipin signaling, and 2-CysPrx to photosynthesis, sugar and amino acid metabolism. Deletion of either OASTL-B or SERAT2;1 frequently induced antagonistic changes in biochemical or molecular features. Enhanced sensitivity of mutant seedlings to OPDA and leaf discs to NaHS-administration confirmed the presumed functional interference of the COPS module in redox and oxylipin signaling.


Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/genética , Oxilipinas/metabolismo , Transdução de Sinais , Enxofre/metabolismo , Aclimatação , Arabidopsis/enzimologia , Arabidopsis/fisiologia , Arabidopsis/efeitos da radiação , Proteínas de Arabidopsis/genética , Carbono-Oxigênio Liases/genética , Carbono-Oxigênio Liases/metabolismo , Cloroplastos/metabolismo , Cloroplastos/efeitos da radiação , Ciclopentanos/metabolismo , Ciclofilinas/genética , Ciclofilinas/metabolismo , Cisteína/metabolismo , Cisteína Sintase/genética , Cisteína Sintase/metabolismo , Luz , Oxirredução , Peroxirredoxinas/genética , Peroxirredoxinas/metabolismo , Fotossíntese/efeitos da radiação , Folhas de Planta/genética , Folhas de Planta/fisiologia , Folhas de Planta/efeitos da radiação , Plântula/genética , Plântula/fisiologia , Plântula/efeitos da radiação
15.
Plant Cell Environ ; 40(8): 1552-1564, 2017 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-28338213

RESUMO

We examined the effects of leaf temperature on the estimation of maximal Rubisco capacity (Vcmax ) from gas exchange measurements of wheat leaves using a C3 photosynthesis model. Cultivars of spring wheat (Triticum aestivum (L)) and triticale (X Triticosecale Wittmack) were grown in a greenhouse or in the field and measured at a range of temperatures under controlled conditions in a growth cabinet (2 and 21% O2 ) or in the field using natural diurnal variation in temperature, respectively. Published Rubisco kinetic constants for tobacco did not describe the observed CO2 response curves well as temperature varied. By assuming values for the Rubisco Michaelis-Menten constants for CO2 (Kc ) and O2 (Ko ) at 25 °C derived from tobacco and the activation energies of Vcmax from wheat and respiration in the light, Rd , from tobacco, we derived activation energies for Kc and Ko (93.7 and 33.6 kJ mol-1 , respectively) that considerably improved the fit of the model to observed data. We confirmed that temperature dependence of dark respiration for wheat was well described by the activation energy for Rd from tobacco. The new parameters improved the estimation of Vcmax under field conditions, where temperatures increased through the day.


Assuntos
Carbono/metabolismo , Modelos Biológicos , Fotossíntese , Temperatura , Triticum/fisiologia , Dióxido de Carbono/metabolismo , Respiração Celular/efeitos da radiação , Cloroplastos/metabolismo , Cloroplastos/efeitos da radiação , Meio Ambiente , Cinética , Luz , Fotossíntese/efeitos da radiação , Folhas de Planta/fisiologia , Folhas de Planta/efeitos da radiação , Reprodutibilidade dos Testes , Ribulose-Bifosfato Carboxilase/metabolismo , Triticum/efeitos da radiação
16.
Biochem J ; 474(6): 877-883, 2017 03 07.
Artigo em Inglês | MEDLINE | ID: mdl-28270560

RESUMO

Concepts of the roles of reactive oxygen species (ROS) in plants and animals have shifted in recent years from focusing on oxidative damage effects to the current view of ROS as universal signalling metabolites. Rather than having two opposing activities, i.e. damage and signalling, the emerging concept is that all types of oxidative modification/damage are involved in signalling, not least in the induction of repair processes. Examining the multifaceted roles of ROS as crucial cellular signals, we highlight as an example the loss of photosystem II function called photoinhibition, where photoprotection has classically been conflated with oxidative damage.


Assuntos
Transdução de Sinal Luminoso/fisiologia , Fotossíntese/fisiologia , Complexo de Proteína do Fotossistema II/fisiologia , Plantas/efeitos da radiação , Espécies Reativas de Oxigênio/metabolismo , Trifosfato de Adenosina/biossíntese , Clorofila/agonistas , Clorofila/metabolismo , Cloroplastos/metabolismo , Cloroplastos/efeitos da radiação , Cloroplastos/ultraestrutura , Fluorescência , Luz , NADP/biossíntese , Oxirredução , Estresse Oxidativo , Plantas/metabolismo , Plantas/ultraestrutura
17.
Plant Physiol ; 172(3): 1480-1493, 2016 11.
Artigo em Inglês | MEDLINE | ID: mdl-27634426

RESUMO

In linear photosynthetic electron transport, ferredoxin:NADP(H) oxidoreductase (FNR) transfers electrons from ferredoxin (Fd) to NADP+ Both NADPH and reduced Fd (Fdred) are required for reductive assimilation and light/dark activation/deactivation of enzymes. FNR is therefore a hub, connecting photosynthetic electron transport to chloroplast redox metabolism. A correlation between FNR content and tolerance to oxidative stress is well established, although the precise mechanism remains unclear. We investigated the impact of altered FNR content and localization on electron transport and superoxide radical evolution in isolated thylakoids, and probed resulting changes in redox homeostasis, expression of oxidative stress markers, and tolerance to high light in planta. Our data indicate that the ratio of Fdred to FNR is critical, with either too much or too little FNR potentially leading to increased superoxide production, and perception of oxidative stress at the level of gene transcription. In FNR overexpressing plants, which show more NADP(H) and glutathione pools, improved tolerance to high-light stress indicates that disturbance of chloroplast redox poise and increased free radical generation may help "prime" the plant and induce protective mechanisms. In fnr1 knock-outs, the NADP(H) and glutathione pools are more oxidized relative to the wild type, and the photoprotective effect is absent despite perception of oxidative stress at the level of gene transcription.


Assuntos
Adaptação Fisiológica , Proteínas de Arabidopsis/metabolismo , Arabidopsis/enzimologia , Arabidopsis/fisiologia , Ferredoxina-NADP Redutase/metabolismo , Estresse Fisiológico , Adaptação Fisiológica/efeitos da radiação , Arabidopsis/efeitos da radiação , Cloroplastos/metabolismo , Cloroplastos/efeitos da radiação , Regulação da Expressão Gênica de Plantas/efeitos da radiação , Glutationa/metabolismo , Luz , NADP/metabolismo , Oxirredução/efeitos da radiação , Plantas Geneticamente Modificadas , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Espécies Reativas de Oxigênio/metabolismo , Solubilidade , Estresse Fisiológico/efeitos da radiação , Superóxidos/metabolismo , Tilacoides/metabolismo
18.
Photosynth Res ; 129(2): 217-25, 2016 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-27372712

RESUMO

In the context of global climate change, drought is one of the major stress factors with negative effect on photosynthesis and plant productivity. Currently, chlorophyll fluorescence parameters are widely used as indicators of plant stress, mainly owing to the rapid, non-destructive and simple measurements this technique allows. However, these parameters have been shown to have limited sensitivity for the monitoring of water deficit as leaf desiccation has relatively small effect on photosystem II photochemistry. In this study, we found that blue light-induced increase in leaf transmittance reflecting chloroplast avoidance movement was much more sensitive to a decrease in relative water content (RWC) than chlorophyll fluorescence parameters in dark-desiccating leaves of tobacco (Nicotiana tabacum L.) and barley (Hordeum vulgare L.). Whereas the inhibition of chloroplast avoidance movement was detectable in leaves even with a small RWC decrease, the chlorophyll fluorescence parameters (F V/F M, V J, Ф PSII, NPQ) changed markedly only when RWC dropped below 70 %. For this reason, we propose light-induced chloroplast avoidance movement as a sensitive indicator of the decrease in leaf RWC. As our measurement of chloroplast movement using collimated transmittance is simple and non-destructive, it may be more suitable in some cases for the detection of plant stresses including water deficit than the conventionally used chlorophyll fluorescence methods.


Assuntos
Cloroplastos/fisiologia , Hordeum/fisiologia , Nicotiana/fisiologia , Água/análise , Clorofila/metabolismo , Cloroplastos/efeitos da radiação , Escuridão , Dessecação , Secas , Fluorescência , Hordeum/efeitos da radiação , Fotossíntese , Folhas de Planta/fisiologia , Folhas de Planta/efeitos da radiação , Estresse Fisiológico , Nicotiana/efeitos da radiação , Água/fisiologia
19.
Plant Cell Physiol ; 57(9): 1839-53, 2016 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-27318281

RESUMO

Taxus chinensis var. mairei is a species endemic to south-eastern China and one of the natural sources for the anticancer medicine paclitaxel. To investigate the molecular response and defense mechanisms of T. chinensis leaves to enhanced ultraviolet-A (UV-A) radiation, gel-free/label-free and gel-based proteomics and gas chromatography-mass spectrometry (GC-MS) analyses were performed. The transmission electron microscopy results indicated damage to the chloroplast under UV-A radiation. Proteomics analyses in leaves and chloroplasts showed that photosynthesis-, glycolysis-, secondary metabolism-, stress-, and protein synthesis-, degradation- and activation-related systems were mainly changed under UV-A radiation. Forty-seven PSII proteins and six PSI proteins were identified as being changed in leaves and chloroplasts under UV-A treatment. This indicated that PSII was more sensitive to UV-A than PSI as the target of UV-A light. Enhanced glycolysis, with four glycolysis-related key enzymes increased, provided precursors for secondary metabolism. The 1-deoxy-d-xylulose-5-phosphate reductoisomerase and 4-hydroxy-3-methylbut-2-enyl diphosphate reductase were identified as being significantly increased during UV-A radiation, which resulted in paclitaxel enhancement. Additionally, mRNA expression levels of genes involved in the paclitaxel biosynthetic pathway indicated a down-regulation under UV-A irradiation and up-regulation in dark incubation. These results reveal that a short-term high dose of UV-A radiation could stimulate the plant stress defense system and paclitaxel production.


Assuntos
Metabolômica/métodos , Folhas de Planta/fisiologia , Proteômica/métodos , Taxus/metabolismo , Taxus/efeitos da radiação , Carotenoides/metabolismo , Cloroplastos/efeitos da radiação , Cloroplastos/ultraestrutura , Enzimas/genética , Enzimas/metabolismo , Regulação da Expressão Gênica de Plantas , Paclitaxel/biossíntese , Paclitaxel/metabolismo , Fitosteróis/metabolismo , Folhas de Planta/metabolismo , Folhas de Planta/efeitos da radiação , Folhas de Planta/ultraestrutura , Proteínas de Plantas/análise , Proteínas de Plantas/metabolismo , Taxoides/metabolismo , Taxus/genética , Raios Ultravioleta
20.
J Exp Bot ; 67(8): 2495-506, 2016 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-26969746

RESUMO

Plant chloroplasts are light-driven cell factories that have great potential to act as a chassis for metabolic engineering applications. Using plant chloroplasts, we demonstrate how photosynthetic reducing power can drive a metabolic pathway to synthesise a bio-active natural product. For this purpose, we stably engineered the dhurrin pathway from Sorghum bicolor into the chloroplasts of Nicotiana tabacum (tobacco). Dhurrin is a cyanogenic glucoside and its synthesis from the amino acid tyrosine is catalysed by two membrane-bound cytochrome P450 enzymes (CYP79A1 and CYP71E1) and a soluble glucosyltransferase (UGT85B1), and is dependent on electron transfer from a P450 oxidoreductase. The entire pathway was introduced into the chloroplast by integrating CYP79A1, CYP71E1, and UGT85B1 into a neutral site of the N. tabacum chloroplast genome. The two P450s and the UGT85B1 were functional when expressed in the chloroplasts and converted endogenous tyrosine into dhurrin using electrons derived directly from the photosynthetic electron transport chain, without the need for the presence of an NADPH-dependent P450 oxidoreductase. The dhurrin produced in the engineered plants amounted to 0.1-0.2% of leaf dry weight compared to 6% in sorghum. The results obtained pave the way for plant P450s involved in the synthesis of economically important compounds to be engineered into the thylakoid membrane of chloroplasts, and demonstrate that their full catalytic cycle can be driven directly by photosynthesis-derived electrons.


Assuntos
Vias Biossintéticas , Cloroplastos/metabolismo , Cloroplastos/efeitos da radiação , Sistema Enzimático do Citocromo P-450/metabolismo , Luz , Nicotiana/genética , Nitrilas/metabolismo , Sorghum/enzimologia , Biomassa , Vias Biossintéticas/genética , Vias Biossintéticas/efeitos da radiação , Cloroplastos/ultraestrutura , Cromatografia Líquida , Regulação Enzimológica da Expressão Gênica/efeitos da radiação , Genoma de Cloroplastos , Genoma de Planta , Glucosídeos/metabolismo , Espectrometria de Massas , Óperon/genética , Fenótipo , Fotossíntese/efeitos da radiação , Plantas Geneticamente Modificadas , Subunidades Proteicas/metabolismo , Transformação Genética/efeitos da radiação
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