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1.
Biochim Biophys Acta Bioenerg ; 1861(3): 148154, 2020 03 01.
Artigo em Inglês | MEDLINE | ID: mdl-31935360

RESUMO

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


Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/metabolismo , Elétrons , NAD(P)H Desidrogenase (Quinona)/metabolismo , Complexo de Proteínas do Centro de Reação Fotossintética/metabolismo , Complexo de Proteína do Fotossistema I/metabolismo , Arabidopsis/genética , Arabidopsis/efeitos da radiação , Transporte de Elétrons/efeitos da radiação , Genótipo , Luz , Oxirredução/efeitos da radiação , Fosforilação/efeitos da radiação , Complexo de Proteína do Fotossistema II/metabolismo
2.
Plant Sci ; 289: 110275, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31623777

RESUMO

Owing to the high leaf mass per area, alpine evergreen sclerophyllous Rhododendron have low values of mesophyll conductance (gm). The resulting low chloroplast CO2 concentration aggravates photorespiration, which requires a higher ATP/NADPH ratio. However, the significance of photorespiration and underlying mechanisms of energy balance in these species are little known. In this study, eight alpine evergreen sclerophyllous Rhododendron species grown in a common garden were tested for their gm, electron flow to photorespiration, and energy balancing. Under saturating light, gm was the most limiting factor for net photosynthesis (AN) in all species, and the species differences in AN were primarily driven by gm rather than stomatal conductance. The total electron flow through photosystem II (ETRII) nearly equaled the electron transport required for Rubisco carboxylation and oxygenation. Furthermore, blocking electron flow to photosystem I with appropriate inhibitors showed that electron flow to plastic terminal oxidase was not observed. As a result, these studied species showed little alternative electron flow mediated by water-water cycle or plastic terminal oxidase. By comparison, the ratio of electron transport consumed by photorespiration to ETRII (JPR/ETRII), ranging from 43%∼55%, was negatively correlated to AN and gm. Furthermore, the increased ATP production required by enhanced photorespiration was regulated by cyclic electron flow around photosystem I. These results indicate that photorespiration is the major electron sink for dissipation of excess excitation energy in the alpine evergreen sclerophyllous Rhododendron species. The coordination of gm, photorespiration and cyclic electron flow is important for sustaining leaf photosynthesis.


Assuntos
Transporte de Elétrons/efeitos da radiação , Luz , Fotossíntese/efeitos da radiação , Complexo de Proteína do Fotossistema II/metabolismo , Rhododendron/fisiologia , Altitude , Rhododendron/efeitos da radiação , Especificidade da Espécie
3.
Plant Sci ; 287: 110166, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31481226

RESUMO

In angiosperms, cyclic electron flow (CEF) around photosystem I (PSI) is more important for photoprotection under fluctuating light than under constant light. However, the underlying mechanism is not well known. In the present study, we measured the CEF activity, P700 redox state and electrochromic shift signal upon a sudden transition from low to high light in wild-type plants of Arabidopsis thaliana and Bletilla striata (Orchidaceae). Within the first 20 s after transition from low to high light, P700 was highly reduced in both species, which was accompanied with a sufficient proton gradient (ΔpH) across the thylakoid membranes. Meanwhile, the level of CEF activation was elevated. After transition from low to high light for 60 s, the plants generated an optimal ΔpH. Under such condition, PSI was highly oxidized and the level of CEF activation decreased to the steady state. Furthermore, the CEF activation was positively correlated to the P700 reduction ratio. These results indicated that upon a sudden transition from low to high light, the insufficient ΔpH led to the over-reduction of PSI electron carriers, which in turn stimulated the CEF around PSI. This transient stimulation of CEF not only favored the rapid ΔpH formation but also accepted electrons from PSI, thus protecting PSI at donor and acceptor sides. These findings provide new insights into the important role of CEF in regulation of photosynthesis under fluctuating light.


Assuntos
Arabidopsis/metabolismo , Transporte de Elétrons , Orchidaceae/metabolismo , Complexo de Proteína do Fotossistema I/metabolismo , Arabidopsis/efeitos da radiação , Clorofila/metabolismo , Relação Dose-Resposta à Radiação , Transporte de Elétrons/efeitos da radiação , Luz , Orchidaceae/efeitos da radiação , Complexo de Proteína do Fotossistema I/efeitos da radiação
4.
Med Eng Phys ; 71: 108-113, 2019 09.
Artigo em Inglês | MEDLINE | ID: mdl-31303375

RESUMO

The purpose of this study was to investigate the effect of different doses of photobiomodulation (PBM) on mitochondrial respiratory complexes and oxidative cellular energy metabolic enzymes in the mitochondria of brain, muscle, and C6 glioma cells after different time intervals. C6 cells were irradiated with an AlGaInP laser at 10, 30, and 60 J/cm2 for 20, 60, and 120 s, respectively. After irradiation, the cells were maintained in serum-free Dulbecco's Modified Eagle's medium for 24 h, and biochemical measurements were made subsequently. Mitochondrial suspensions from adult rat skeletal muscles/brains were irradiated with an AlGaInP laser at the abovementioned doses. In one group, the reaction was stopped 5 min after irradiation and in the other 60 min after irradiation. Both the C6 cells that received the doses of 10 and 30 J/cm² showed increased complex I activity; the cells that were irradiated at 30 J/cm2 showed increased hexokinase activity. Five minutes after the introduction of PBM of the muscle mitochondria (at 30 and 60 J/cm2), the activity of complex I increased, while the activity of complex IV increased only at 60 J/cm2. One hour after the laser session, complex II activity increased in the cells treated with 10 and 60 J/cm²; however, complex IV activity showed an increase in all PBM groups. In brain mitochondria, 5 min after irradiation only the activity of complex IV increased in all PBM groups. One hour after the laser session, complex II activity increased at 60 J/cm2, and complex IV activity increased for all PBM groups when compared to controls. PBM could increase the activity of respiratory chain complexes in an apparently dose- and time-dependent manner.


Assuntos
Astrocitoma/patologia , Encéfalo/citologia , Terapia com Luz de Baixa Intensidade , Mitocôndrias/efeitos da radiação , Músculos/citologia , Linhagem Celular Tumoral , Relação Dose-Resposta à Radiação , Transporte de Elétrons/efeitos da radiação , Humanos , Mitocôndrias/metabolismo , Fatores de Tempo
5.
Phys Chem Chem Phys ; 21(17): 8721-8728, 2019 Apr 24.
Artigo em Inglês | MEDLINE | ID: mdl-30968099

RESUMO

The photosynthetic protein complex, photosystem II (PSII), conducts the light-driven water-splitting reaction with unrivaled efficiency. Proton-coupled electron transfer (PCET) reactions at the redox-active tyrosine residues are thought to play a critical role in the water-splitting chemistry. Addressing the fundamental question as to why the tyrosine residue, YZ, is kinetically competent in comparison to a symmetrically placed tyrosine residue, YD, is important for the elucidation of the mechanism of PCET in the water-splitting reaction of PSII. Here, using all-quantum-mechanical calculations we study PCET at the YZ and YD residues of PSII. We find that when YZ is in its protein matrix under physiological conditions, the HOMO of YZ constitutes the HOMO of the whole system. In contrast, the HOMO of YD is buried under the electronic states localized elsewhere in the protein matrix and PCET at YD requires the transfer of the phenolic proton, which elevates the HOMO of YD to become the HOMO of the whole system. This leads to the oxidation of YD, albeit on a slower timescale. Our study reveals that the key differences between the electronic structure of YZ and YD are primarily determined by the protonation state of the respective hydrogen-bonding partners, D1-His190 and D2-His189, or more generally by the H-bonding network of the protein matrix.


Assuntos
Modelos Moleculares , Complexo de Proteína do Fotossistema II/química , Transporte de Elétrons/efeitos da radiação , Ligação de Hidrogênio/efeitos da radiação , Cinética , Oxirredução , Fotossíntese/efeitos da radiação , Conformação Proteica , Prótons , Teoria Quântica , Tirosina/química , Água/química
6.
Photosynth Res ; 141(3): 303-314, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31004254

RESUMO

When plants suffer from abiotic stresses, cyclic electron flow (CEF) is induced for photo-protection. Putrescine (Put), a primary polyamine in chloroplasts, plays a critical role in stress tolerance. However, the relationship between CEF and Put in chloroplasts for photo-protection is unknown. In this study, we investigated the role of Put-induced CEF for salt tolerance in cucumber plants (Cucumis sativus L). Treatment with 90 mM NaCl and/or Put did not influence the maximum photochemical efficiency of PSII (Fv/Fm), but the photoactivity of PSI was severely inhibited by NaCl. Salt stress induced a high level of CEF; moreover, plants treated with both NaCl and Put exhibited much higher CEF activity and ATP accumulation than those exhibited by single-salt-treated plants to provide an adequate ATP/NADPH ratio for plant growth. Furthermore, Put decreased the trans-membrane proton gradient (ΔpH), which was accompanied by reduced pH-dependent non-photochemical quenching (NPQ) and an increased the effective quantum yield of PSII (Y(II)). The ratio of NADP+/NADPH increased significantly with Put in salt-stressed leaves compared with the ratio in leaves treated with NaCl, indicating that Put relieved over-reduction pressure at the PSI acceptor side caused by salt stress. Collectively, our results suggest that exogenous Put creates an excellent condition for CEF promotion: a large amount of pmf is predominantly stored as Δψ, resulting in moderate lumen pH and low NPQ, while maintaining high rates of ATP synthesis (high pmf).


Assuntos
Cucumis sativus/fisiologia , Cucumis sativus/efeitos da radiação , Luz , Putrescina/farmacologia , Estresse Salino/efeitos da radiação , Trifosfato de Adenosina/metabolismo , Clorofila/metabolismo , Cucumis sativus/efeitos dos fármacos , Cucumis sativus/crescimento & desenvolvimento , Transporte de Elétrons/efeitos dos fármacos , Transporte de Elétrons/efeitos da radiação , Fluorescência , Modelos Biológicos , NADP/metabolismo , Fenótipo , Fotossíntese/efeitos dos fármacos , Complexo de Proteína do Fotossistema II/metabolismo , Folhas de Planta/efeitos dos fármacos , Folhas de Planta/fisiologia , Proteínas de Plantas/metabolismo , Força Próton-Motriz , Estresse Salino/efeitos dos fármacos , Plântula/efeitos dos fármacos , Plântula/fisiologia , Cloreto de Sódio/farmacologia
7.
FEBS Lett ; 593(8): 788-798, 2019 04.
Artigo em Inglês | MEDLINE | ID: mdl-30896038

RESUMO

In photosynthetic systems of oxygenic type, plastoquinone (PQ) molecules are reduced by photosystem II (PSII). The turnover of PQ determines the rate of PSII operation. PQ molecules are present in surplus with respect to PSII. In this work, using the pulse amplitude modulation-fluorometry technique, we quantified photo-reducible PQ pools in chloroplasts of two contrasting ecotypes of Tradescantia, acclimated either to low light (~ 100 µmol photons·m-2 ·s-1 , LL) or to high light (~ 1000 µmol photons·m-2 ·s-1 , HL). The LL-grown plants are characterized by higher capacity of rapidly reducible PQ pool ([PQ]0 /[PSII] ≈ 8) as compared to HL-grown plants of both species ([PQ]0 /[PSII] ≈ 4). The elevated content of PQ in LL plants favours photosynthetic electron flow at low-solar irradiance.


Assuntos
Aclimatação/efeitos da radiação , Cloroplastos/metabolismo , Cloroplastos/efeitos da radiação , Commelinaceae/fisiologia , Commelinaceae/efeitos da radiação , Luz , Plastoquinona/metabolismo , Clorofila/metabolismo , Commelinaceae/metabolismo , Relação Dose-Resposta à Radiação , Transporte de Elétrons/efeitos da radiação , Cinética , Complexo de Proteína do Fotossistema II/metabolismo
8.
Phys Chem Chem Phys ; 21(8): 4387-4393, 2019 Feb 20.
Artigo em Inglês | MEDLINE | ID: mdl-30729242

RESUMO

The understanding of the 5-bromouracil (BrU) based photosensitization mechanism of DNA damage is of large interest due to the potential applications in photodynamic therapy. Photoinduced electron transfer (ET) in BrU labeled duplexes comprising the 5'-GBrU or 5'-ABrU sequence showed that a much lower reactivity was found for the 5'-GBrU pattern. Since the ionization potential of G is lower than that of A, this sequence selectivity has been dubbed a contrathermodynamic one. In the current work, we employ the Marcus and Marcus-Levich-Jortner theory of ET in order to shed light on the observed effect. By using a combination of Density Functional Theory (DFT) and solvation continuum models, we calculated the electronic couplings, reorganization energies, and thermodynamic stimuli for electron transfer which enabled the rates of forward and back ET to be estimated for the two considered sequences. The calculated rates show that the photoreaction could not be efficient if the ET process proceeded within the considered dimers. Only after introducing additional adenines between G and BrU, which accelerates the forward and slows down the back ET, is a significant amount of photodamage expected.


Assuntos
Bromouracila/química , DNA/efeitos da radiação , Modelos Moleculares , Processos Fotoquímicos , Adenina/química , Transporte de Elétrons/efeitos da radiação , Elétrons , Guanina/química , Cinética , Luz , Conformação de Ácido Nucleico , Relação Estrutura-Atividade , Termodinâmica
9.
New Phytol ; 222(3): 1364-1379, 2019 05.
Artigo em Inglês | MEDLINE | ID: mdl-30636322

RESUMO

Photoacclimation consists of short- and long-term strategies used by photosynthetic organisms to adapt to dynamic light environments. Observable photophysiology changes resulting from these strategies have been used in coarse-grained models to predict light-dependent growth and photosynthetic rates. However, the contribution of the broader metabolic network, relevant to species-specific strategies and fitness, is not accounted for in these simple models. We incorporated photophysiology experimental data with genome-scale modeling to characterize organism-level, light-dependent metabolic changes in the model diatom Phaeodactylum tricornutum. Oxygen evolution and photon absorption rates were combined with condition-specific biomass compositions to predict metabolic pathway usage for cells acclimated to four different light intensities. Photorespiration, an ornithine-glutamine shunt, and branched-chain amino acid metabolism were hypothesized as the primary intercompartment reductant shuttles for mediating excess light energy dissipation. Additionally, simulations suggested that carbon shunted through photorespiration is recycled back to the chloroplast as pyruvate, a mechanism distinct from known strategies in photosynthetic organisms. Our results suggest a flexible metabolic network in P. tricornutum that tunes intercompartment metabolism to optimize energy transport between the organelles, consuming excess energy as needed. Characterization of these intercompartment reductant shuttles broadens our understanding of energy partitioning strategies in this clade of ecologically important primary producers.


Assuntos
Diatomáceas/metabolismo , Diatomáceas/efeitos da radiação , Luz , Aclimatação/efeitos da radiação , Oxirredutases do Álcool/metabolismo , Biomassa , Respiração Celular/efeitos da radiação , Ritmo Circadiano/efeitos da radiação , Simulação por Computador , Transporte de Elétrons/efeitos da radiação , Redes e Vias Metabólicas/efeitos da radiação , Mitocôndrias/metabolismo , Mitocôndrias/efeitos da radiação , Modelos Biológicos , Fotossíntese/efeitos da radiação , Ácido Pirúvico/metabolismo
10.
New Phytol ; 221(3): 1317-1327, 2019 02.
Artigo em Inglês | MEDLINE | ID: mdl-30306559

RESUMO

Mixotrophy is a dominant metabolic strategy in ecosystems worldwide. Shifts in temperature (T) and light (i.e. the ultraviolet portion of spectrum (UVR)) are key abiotic factors that modulate the conditions under which an organism is able to live. However, whether the interaction between both drivers alters mixotrophy in a global-change context remains unassessed. To determine the T × UVR effects on relative electron transport rates, nonphotochemical quenching, bacterivory, and bacterial production, we conducted an experiment with Isochrysis galbana populations grown mixotrophically, which were exposed to 5°C of cooling and warming with respect to the control (19°C) with (or without) UVR over light-dark cycles and different timescales. At the beginning of the experiment, cooling inhibited the relative electron transport and bacterivory rates, whereas warming depressed only bacterivory regardless of the radiation treatment. By the end of the experiment, warming and UVR conditions stimulated bacterivory. These reduced relative electron transport rates (c. 50% (warming) and > 70% (cooling)) were offset by increased (35%) cumulative bacterivory rates under warming and UVR conditions. We propose that mixotrophy constitutes an energy-saving and a compensatory mechanism to gain carbon (C) when photosynthesis is impaired, and highlight the need to consider the natural environmental changes affecting the populations when we test the impacts of interacting global-change drivers.


Assuntos
Organismos Aquáticos/fisiologia , Organismos Aquáticos/efeitos da radiação , Temperatura Baixa , Aquecimento Global , Haptófitas/fisiologia , Haptófitas/efeitos da radiação , Raios Ultravioleta , Bactérias/metabolismo , Transporte de Elétrons/efeitos da radiação , Fotoperíodo , Complexo de Proteína do Fotossistema II/metabolismo
11.
Physiol Plant ; 167(2): 144-158, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-30426522

RESUMO

Plants are often subjected to rapidly alternating light intensity and quality. While both short- and long-term changes in red and blue light affect leaf photosynthesis, their impact on dynamic photosynthesis is not well documented. It was tested how dynamic and steady-state photosynthetic traits were affected by red/blue ratios, either during growth or during measurements, in tomato leaves. Four red/blue ratios were used: monochromatic red (R100 ), monochromatic blue (B100 ), a red/blue light ratio of 9:1 (R90 B10 ) and a red/blue light ratio of 7:3 (R70 B30 ). R100 grown leaves showed decreased photosynthetic capacity (maximum rates of light-saturated photosynthesis, carboxylation, electron transport and triose phosphate use), leaf thickness and nitrogen concentrations. Acclimation to various red/blue ratios had limited effects on photosynthetic induction in dark-adapted leaves. B100 -grown leaves had a approximately 15% larger initial NPQ transient than the other treatments, which may be beneficial for photoprotection under fluctuating light. B100 -grown leaves also showed faster stomatal closure when exposed to low light intensity, which likely resulted from smaller stomata and higher stomatal density. When measured under different red/blue ratios, stomatal opening rate and photosynthetic induction rate were hardly accelerated by increased fractions of blue light in both growth chamber-grown leaves and greenhouse-grown leaves. However, steady-state photosynthesis rate 30 min after photosynthetic induction was strongly reduced in leaves exposed to B100 during the measurement. We conclude that varying red/blue light ratios during growth and measurement strongly affects steady-state photosynthesis, but has limited effects on photosynthetic induction rate.


Assuntos
Lycopersicon esculentum/efeitos da radiação , Fotossíntese/efeitos da radiação , Transporte de Elétrons/efeitos da radiação , Luz , Lycopersicon esculentum/fisiologia , Folhas de Planta/fisiologia , Folhas de Planta/efeitos da radiação
12.
Free Radic Biol Med ; 130: 436-445, 2019 01.
Artigo em Inglês | MEDLINE | ID: mdl-30395972

RESUMO

Heavy ion radiotherapy has shown great promise for cancer therapy. Understanding the cellular response mechanism to heavy ion radiation is required to explore measures of overcoming devastating side effects. Here, we performed a quantitative proteomic analysis to investigate the mechanism of carbon ion irradiation on human AHH-1 lymphoblastoid cells. We identified 4602 proteins and quantified 4569 proteins showing high coverage in the mitochondria. Data are available via ProteomeXchange with identifier PXD008351. After stringent filtering, 290 proteins were found to be significantly up-regulated and 16 proteins were down-regulated. Functional analysis revealed that these up-regulated proteins were enriched in the process of DNA damage repair, mitochondrial ribosome, and particularly mitochondrial respiratory chain, accounting for approximately 50% of the accumulated proteins. Bioinformatics and functional analysis demonstrated that these up-regulated mitochondrial respiratory chain proteins enhanced ATP production and simultaneously reactive oxygen species release. More importantly, increased reactive oxygen species led to secondary organelle injury and lagged DNA double-strand breaks. Consistently, the expression of antioxidant enzymes was up-regulated for free radical scavenging. The mechanism of lagged secondary injury originated from disturbances in the mitochondrial respiratory chain. Our results provided a novel target for cell self-repair against heavy ion radiation-induced cellular damage.


Assuntos
Transporte de Elétrons/efeitos da radiação , Mitocôndrias/efeitos da radiação , Neoplasias/radioterapia , Proteômica , Antioxidantes/farmacologia , Linhagem Celular Tumoral , Dano ao DNA/genética , Dano ao DNA/efeitos da radiação , Reparo do DNA/genética , Reparo do DNA/efeitos da radiação , Radioterapia com Íons Pesados/efeitos adversos , Humanos , Mitocôndrias/metabolismo , Neoplasias/genética , Neoplasias/metabolismo , Espécies Reativas de Oxigênio/metabolismo
13.
Photosynth Res ; 139(1-3): 367-385, 2019 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-29725995

RESUMO

The high-light-induced alterations in photosynthetic performance of photosystem II (PSII) and photosystem I (PSI) as well as effectiveness of dissipation of excessive absorbed light during illumination for different periods of time at room (22 °C) and low (8-10 °C) temperature of leaves of Arabidopsis thaliana, wt and lut2, were followed with the aim of unraveling the role of lutein in the process of photoinhibition. Photosynthetic parameters of PSII and PSI were determined on whole leaves by PAM fluorometer and oxygen evolving activity-by a Clark-type electrode. In thylakoid membranes, isolated from non-illuminated and illuminated for 4.5 h leaves of wt and lut2 the photochemical activity of PSII and PSI and energy interaction between the main pigment-protein complexes was determined. Results indicate that in non-illuminated leaves of lut2 the maximum rate of oxygen evolution and energy utilization in PSII is lower, excitation pressure of PSII is higher and cyclic electron transport around PSI is faster than in wt leaves. Under high-light illumination, lut2 leaves are more sensitive in respect to PSII performance and the extent of increase of excitation pressure of PSII, ΦNO, and cyclic electron transport around PSI are higher than in wt leaves, especially when illumination is performed at low temperature. Significant part of the excessive light energy is dissipated via mechanism, not dependent on ∆pH and to functioning of xanthophyll cycle in LHCII, operating more intensively in lut2 leaves.


Assuntos
Arabidopsis/metabolismo , Luz , Arabidopsis/efeitos da radiação , Transporte de Elétrons/efeitos da radiação , Mutação , Fotossíntese/fisiologia , Fotossíntese/efeitos da radiação , Folhas de Planta/metabolismo , Folhas de Planta/efeitos da radiação , Temperatura
14.
Sci Rep ; 8(1): 14745, 2018 10 03.
Artigo em Inglês | MEDLINE | ID: mdl-30283151

RESUMO

Photosystem II (PSII) reaction centre D1 protein of oxygenic phototrophs is pivotal for sustaining photosynthesis. Also, it is targeted by herbicides and herbicide-resistant weeds harbour single amino acid substitutions in D1. Conservation of D1 primary structure is seminal in the photosynthetic performance in many diverse species. In this study, we analysed built-in and environmentally-induced (high temperature and high photon fluency - HT/HL) phenotypes of two D1 mutants of Chlamydomonas reinhardtii with Ala250Arg (A250R) and Ser264Lys (S264K) substitutions. Both mutations differentially affected efficiency of electron transport and oxygen production. In addition, targeted metabolomics revealed that the mutants undergo specific differences in primary and secondary metabolism, namely, amino acids, organic acids, pigments, NAD, xanthophylls and carotenes. Levels of lutein, ß-carotene and zeaxanthin were in sync with their corresponding gene transcripts in response to HT/HL stress treatment in the parental (IL) and A250R strains. D1 structure analysis indicated that, among other effects, remodelling of H-bond network at the QB site might underpin the observed phenotypes. Thus, the D1 protein, in addition to being pivotal for efficient photosynthesis, may have a moonlighting role in rewiring of specific metabolic pathways, possibly involving retrograde signalling.


Assuntos
Chlamydomonas reinhardtii/genética , Transdução de Sinal Luminoso/genética , Fótons , Fotossíntese/genética , Complexo de Proteína do Fotossistema II/química , Substituição de Aminoácidos , Aminoácidos/metabolismo , Carotenoides/biossíntese , Reprogramação Celular , Chlamydomonas reinhardtii/metabolismo , Chlamydomonas reinhardtii/efeitos da radiação , Ácidos Dicarboxílicos/metabolismo , Transporte de Elétrons/efeitos da radiação , Expressão Gênica , Temperatura Alta , Ligação de Hidrogênio , Redes e Vias Metabólicas/genética , Modelos Moleculares , Mutação , NAD/metabolismo , Oxigênio/metabolismo , Complexo de Proteína do Fotossistema II/genética , Complexo de Proteína do Fotossistema II/metabolismo , Pigmentos Biológicos/biossíntese , Estrutura Secundária de Proteína , Xantofilas/biossíntese
15.
Plant Physiol Biochem ; 132: 453-464, 2018 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-30292162

RESUMO

The interaction of widely recognized causes of eelgrass decline (high seawater temperature and limited light intensity) on photosynthetic electron transport was investigated via chlorophyll fluorescence technique. High seawater temperature combined light intensity significantly increasing the relative maximum electron transport rate (rETRmax); at critical temperature of 30 °C, the rETRmax increased with the enhancement of light intensity, indicating the elevation of overall photosynthetic performance. Based on the magnitude of effect size (η2), light intensity was the predominant factor affecting the performance index (PIABS), indicating that photosystem II (PSII) was sensitive to light intensity. Moreover, the donor side was severely damaged as evidenced by the higher decrease amplitude of fast component and its subsequent incomplete recovery. The reaction center exhibited limited flexibility due to the slight decrease amplitude in maximum photochemical quantum yield. In contrast with PSII, photosystem I (PSI) was more sensitive to high seawater temperature, based on the magnitude of η2 derived from the maximal decrease in slope. High seawater temperature significantly increased PSI activity, plastoquinol reoxidation capacity, and probability for electron transfer to final PSI electron acceptors. Moreover, it combined elevated light intensity significantly stimulated the activity of cyclic electron flow (CEF) around PSI. Higher activity of both PSI and CEF contributed to balancing the linear electron transport via alleviating the over-reduction of the plastoquinone pool, exhibiting flexible regulation of photosynthetic electron transport at critical temperature. Therefore, limited light intensity decreased the tolerance of eelgrass to critical temperature, which might be a factor contributing factor in the observed decline.


Assuntos
Temperatura Alta , Luz , Fotossíntese/efeitos da radiação , Água do Mar , Zosteraceae/fisiologia , Zosteraceae/efeitos da radiação , Análise de Variância , Clorofila/metabolismo , Transporte de Elétrons/efeitos da radiação , Fluorescência , Complexo de Proteína do Fotossistema I/metabolismo , Complexo de Proteína do Fotossistema II/metabolismo , Probabilidade , Fatores de Tempo
16.
In Vitro Cell Dev Biol Anim ; 54(8): 589-599, 2018 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-30083841

RESUMO

Application of high-dosage UVB irradiation in phototherapeutic dermatological treatments present health concerns attributed to UV-exposure. In assessing UV-induced photobiological damage, we investigated dose-dependent effects of UVB irradiation on human keratinocyte cells (HaCaT). Our study implemented survival and apoptosis assays and revealed an unexpected dose response wherein higher UVB-dosage induced higher viability. Established inhibitors, such as AKT- (LY294002), PKC- (Gö6976, and Rottlerin), ERK- (PD98059), P38 MAPK- (SB203580), and JNK- (SP600125), were assessed to investigate UV-induced apoptotic pathways. Despite unobvious contributions of known signaling pathways in dose-response mediation, microarray analysis identified transcriptional expression of UVB-response genes related to the respiratory-chain. Observed correlation of ROS-production with UVB irradiation potentiated ROS as the underlying mechanism for observed dose responses. Inability of established pathways to explain such responses suggests the complex nature underlying UVB-phototherapy response.


Assuntos
Queratinócitos/efeitos da radiação , Raios Ultravioleta , Acetofenonas/farmacologia , Apoptose/efeitos dos fármacos , Apoptose/efeitos da radiação , Benzopiranos/farmacologia , Ciclo Celular/efeitos dos fármacos , Ciclo Celular/efeitos da radiação , Linhagem Celular , Sobrevivência Celular/efeitos dos fármacos , Sobrevivência Celular/efeitos da radiação , Relação Dose-Resposta à Radiação , Transporte de Elétrons/efeitos da radiação , Flavonoides/farmacologia , Perfilação da Expressão Gênica , Humanos , Queratinócitos/efeitos dos fármacos , Queratinócitos/metabolismo , Óxido Nítrico/metabolismo , Fosfatidilinositol 3-Quinases/metabolismo , Poli(ADP-Ribose) Polimerases/metabolismo , Proteínas Proto-Oncogênicas c-akt/metabolismo , Espécies Reativas de Oxigênio/metabolismo , Superóxidos/metabolismo , Transcrição Genética/efeitos dos fármacos , Transcrição Genética/efeitos da radiação , Regulação para Cima/efeitos dos fármacos , Regulação para Cima/efeitos da radiação
17.
Nat Commun ; 9(1): 2168, 2018 06 04.
Artigo em Inglês | MEDLINE | ID: mdl-29867170

RESUMO

Oxygenic photosynthetic organisms perform solar energy conversion of water and CO2 to O2 and sugar at a broad range of wavelengths and light intensities. These cells also metabolize sugars using a respiratory system that functionally overlaps the photosynthetic apparatus. In this study, we describe the harvesting of photocurrent used for hydrogen production from live cyanobacteria. A non-harmful gentle physical treatment of the cyanobacterial cells enables light-driven electron transfer by an endogenous mediator to a graphite electrode in a bio-photoelectrochemical cell, without the addition of sacrificial electron donors or acceptors. We show that the photocurrent is derived from photosystem I and that the electrons originate from carbohydrates digested by the respiratory system. Finally, the current is utilized for hydrogen evolution on the cathode at a bias of 0.65 V. Taken together, we present a bio-photoelectrochemical system where live cyanobacteria produce stable photocurrent that can generate hydrogen.


Assuntos
Cianobactérias/metabolismo , Hidrogênio/metabolismo , Luz , Consumo de Oxigênio/efeitos da radiação , Fotossíntese/efeitos da radiação , Proteínas de Bactérias/metabolismo , Cianobactérias/ultraestrutura , Transporte de Elétrons/efeitos da radiação , Microscopia Eletrônica de Varredura , Complexo de Proteína do Fotossistema I/metabolismo , Synechocystis/metabolismo , Synechocystis/ultraestrutura
18.
Cell Rep ; 23(12): 3621-3634, 2018 06 19.
Artigo em Inglês | MEDLINE | ID: mdl-29925003

RESUMO

Although growing evidence indicates that bioenergetic metabolism plays an important role in the progression of tumorigenesis, little information is available on the contribution of reprogramming of energy metabolism in cancer initiation. By applying a quantitative proteomic approach and targeted metabolomics, we find that specific metabolic modifications precede primary skin tumor formation. Using a multistage model of ultraviolet B (UVB) radiation-induced skin cancer, we show that glycolysis, tricarboxylic acid (TCA) cycle, and fatty acid ß-oxidation are decreased at a very early stage of photocarcinogenesis, while the distal part of the electron transport chain (ETC) is upregulated. Reductive glutamine metabolism and the activity of dihydroorotate dehydrogenase (DHODH) are both necessary for maintaining high ETC. Mice with decreased DHODH activity or impaired ETC failed to develop pre-malignant and malignant lesions. DHODH activity represents a major link between DNA repair efficiency and bioenergetic patterning during skin carcinogenesis.


Assuntos
Carcinogênese/metabolismo , Carcinogênese/efeitos da radiação , Metabolismo Energético/efeitos da radiação , Neoplasias Cutâneas/metabolismo , Neoplasias Cutâneas/patologia , Raios Ultravioleta , Animais , Proteínas de Ligação a DNA/metabolismo , Regulação para Baixo/efeitos da radiação , Transporte de Elétrons/efeitos da radiação , Epiderme/patologia , Epiderme/efeitos da radiação , Glutamina/metabolismo , Proteínas de Grupo de Alta Mobilidade/metabolismo , Queratinócitos/metabolismo , Queratinócitos/patologia , Queratinócitos/efeitos da radiação , Redes e Vias Metabólicas , Camundongos , Camundongos Pelados , Oxirredutases atuantes sobre Doadores de Grupo CH-CH/metabolismo , Fenótipo , Regulação para Cima/efeitos da radiação
19.
Methods Mol Biol ; 1796: 247-253, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-29856058

RESUMO

Lytic polysaccharide monooxygenases (LPMOs) are redox enzymes that oxidize the most recalcitrant polysaccharides and require extracellular electron donors. The role of electron donation to redox enzymes is pivotal since a nonefficient electron transfer might result in partial activity or reduced kinetics. In this protocol we show the effect of using excited photosynthetic pigments combined with reducing agents as efficient electron donors for monooxygenases. The light-induced electron transfer can enhance the oxidation ability of LPMOs up to ten times.


Assuntos
Bioquímica/métodos , Luz , Oxigenases de Função Mista/metabolismo , Polissacarídeos/metabolismo , Celulose/metabolismo , Transporte de Elétrons/efeitos da radiação , Oxirredução , Padrões de Referência
20.
PLoS One ; 13(5): e0196472, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-29768440

RESUMO

Natural ionizing background radiation has exerted a constant pressure on organisms since the first forms of life appeared on Earth, so that cells have developed molecular mechanisms to avoid or repair damages caused directly by radiation or indirectly by radiation-induced reactive oxygen species (ROS). In the present study, we investigated the transcriptional effect of depriving Shewanella oneidensis cultures of background levels of radiation by growing the cells in a mine 655 m underground, thus reducing the dose rate from 72.1 to 0.9 nGy h-1 from control to treatment, respectively. RNASeq transcriptome analysis showed the differential expression of 4.6 and 7.6% of the S. oneidensis genome during early- and late-exponential phases of growth, respectively. The greatest change observed in the treatment was the downregulation of ribosomal proteins (21% of all annotated ribosomal protein genes during early- and 14% during late-exponential) and tRNA genes (14% of all annotated tRNA genes in early-exponential), indicating a marked decrease in protein translation. Other significant changes were the upregulation of membrane transporters, implying an increase in the traffic of substrates across the cell membrane, as well as the up and downregulation of genes related to respiration, which could be interpreted as a response to insufficient oxidants in the cells. In other reports, there is evidence in multiple species that some ROS not just lead to oxidative stress, but act as signaling molecules to control cellular metabolism at the transcriptional level. Consistent with these reports, several genes involved in the metabolism of carbon and biosynthesis of amino acids were also regulated, lending support to the idea of a wide metabolic response. Our results indicate that S. oneidensis is sensitive to the withdrawal of background levels of ionizing radiation and suggest that a transcriptional response is required to maintain homeostasis and retain normal growth.


Assuntos
Shewanella/genética , Shewanella/efeitos da radiação , Aminoácidos/metabolismo , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Relação Dose-Resposta à Radiação , Transporte de Elétrons/genética , Transporte de Elétrons/efeitos da radiação , Perfilação da Expressão Gênica , Regulação Bacteriana da Expressão Gênica/efeitos da radiação , Ontologia Genética , Genoma Bacteriano/efeitos da radiação , Proteínas de Membrana Transportadoras/genética , Proteínas de Membrana Transportadoras/metabolismo , Interações Microbianas , Estresse Oxidativo/efeitos da radiação , RNA Bacteriano/genética , RNA Bacteriano/metabolismo , Proteínas Ribossômicas/genética , Proteínas Ribossômicas/metabolismo , Shewanella/metabolismo , Transcrição Genética/efeitos da radiação
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