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1.
Int J Mol Sci ; 22(16)2021 Aug 05.
Artigo em Inglês | MEDLINE | ID: mdl-34445145

RESUMO

The main goal of growing plants under various photoperiods is to optimize photosynthesis for using the effect of day length that often acts on plants in combination with biotic and/or abiotic stresses. In this study, Brassica juncea plants were grown under four different day-length regimes, namely., 8 h day/16 h night, 12 h day/12 h night, 16 h day/8 h night, and continuous light, and were infected with a necrotrophic fungus Alternaria brassicicola. The development of necroses on B. juncea leaves was strongly influenced by leaf position and day length. The largest necroses were formed on plants grown under a 16 h day/8 h night photoperiod at 72 h post-inoculation (hpi). The implemented day-length regimes had a great impact on leaf morphology in response to A. brassicicola infection. They also influenced the chlorophyll and carotenoid contents and photosynthesis efficiency. Both the 1st (the oldest) and 3rd infected leaves showed significantly higher minimal fluorescence (F0) compared to the control leaves. Significantly lower values of other investigated chlorophyll a fluorescence parameters, e.g., maximum quantum yield of photosystem II (Fv/Fm) and non-photochemical quenching (NPQ), were observed in both infected leaves compared to the control, especially at 72 hpi. The oldest infected leaf, of approximately 30% of the B. juncea plants, grown under long-day and continuous light conditions showed a 'green island' phenotype in the form of a green ring surrounding an area of necrosis at 48 hpi. This phenomenon was also reflected in changes in the chloroplast's ultrastructure and accelerated senescence (yellowing) in the form of expanding chlorosis. Further research should investigate the mechanism and physiological aspects of 'green islands' formation in this pathosystem.


Assuntos
Alternaria/patogenicidade , Mostardeira/microbiologia , Mostardeira/fisiologia , Necrose/microbiologia , Necrose/patologia , Fotossíntese/fisiologia , Doenças das Plantas/microbiologia , Carotenoides/metabolismo , Clorofila/metabolismo , Clorofila A/metabolismo , Fluorescência , Mostardeira/metabolismo , Necrose/metabolismo , Fotoperíodo , Complexo de Proteína do Fotossistema II/metabolismo , Folhas de Planta/metabolismo , Folhas de Planta/microbiologia
2.
Molecules ; 26(16)2021 Aug 20.
Artigo em Inglês | MEDLINE | ID: mdl-34443651

RESUMO

Caraway (Carum carvi L.) essential oil is a candidate for botanical herbicides. A hypothesis was formulated that the sand-applied maltodextrin-coated caraway oil (MCEO) does not affect the growth of maize (Zea mays L.). In the pot experiment, pre-emergence application of five doses of MCEO was tested on four maize cultivars up to the three-leaf growth stage. The morphological analyses were supported by the measurements of relative chlorophyll content (SPAD), two parameters of chlorophyll a fluorescence, e.g., Fv/Fm and Fv/F0, and fluorescence emission spectra. The analyzed MCEO contained 6.5% caraway EO with carvone and limonene as the main compounds, constituting 95% of the oil. The MCEO caused 7-day delays in maize emergence from the dose of 0.9 g per pot (equal to 96 g m-2). Maize development at the three-leaf growth stage, i.e., length of roots, length of leaves, and biomass of shoots and leaves, was significantly impaired already at the lowest dose of MCEO: 0.4 g per pot, equal to 44 g m-2. A significant drop of both chlorophyll a fluorescence parameters was noted, on average, from the dose of 0.7 g per pot, equal to 69 g m-2. Among the tested cultivars, cv. Rywal and Pomerania were less susceptible to the MCEO compared to the cv. Kurant and Podole. In summary, maize is susceptible to the pre-emergence, sand-applied MCEO from the dose of 44 g m-2.


Assuntos
Óleos Voláteis/farmacologia , Óleos Vegetais/farmacologia , Zea mays/efeitos dos fármacos , Zea mays/crescimento & desenvolvimento , Biomassa , Carum/química , Clorofila A/metabolismo , Monoterpenos Cicloexânicos/química , Monoterpenos Cicloexânicos/farmacologia , Fluorescência , Herbicidas/farmacologia , Limoneno/química , Limoneno/farmacologia , Fotossíntese/efeitos dos fármacos , Folhas de Planta/efeitos dos fármacos , Folhas de Planta/crescimento & desenvolvimento , Folhas de Planta/metabolismo , Raízes de Plantas/efeitos dos fármacos , Raízes de Plantas/crescimento & desenvolvimento , Raízes de Plantas/metabolismo , Zea mays/metabolismo
3.
Plant Cell Physiol ; 62(5): 872-882, 2021 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-33822212

RESUMO

Photosynthetic organisms adjust to fluctuating natural light under physiological ambient conditions through flexible light-harvesting ability of light-harvesting complex II (LHCII). A process called state transition is an efficient regulation mechanism to balance the excitations between photosystem II (PSII) and photosystem I (PSI) by shuttling mobile LHCII between them. However, in situ observation of the migration of LHCII in vivo remains limited. In this study, we investigated the in vivo reversible changes in the intracellular distribution of the chlorophyll (Chl) fluorescence during the light-induced state transitions in Chlamydomonas reinhardtii. The newly developed noninvasive excitation-spectral microscope provided powerful spectral information about excitation-energy transfer between Chl-a and Chl-b. The excitation spectra were detected through the fluorescence emission in the 700-750-nm spectral range, where PSII makes the main contribution, though PSI still makes a non-negligible contribution at room temperature. The technique is sensitive to the Chl-b spectral component specifically bound to LHCII. Using a PSI-specific 685-nm component also provided visualization of the local relative concentration of PSI within a chloroplast at room temperature. The decrease in the relative intensity of the Chl-b band in state 2 was more conspicuous in the PSII-rich region than in the PSI-rich region, reflecting the dissociation of LHCII from PSII. We observed intracellular redistributions of the Chl-b-related light-harvesting abilities within a chloroplast during the state transitions. This observation implies the association of the state transitions with the morphological changes in the thylakoid membrane.


Assuntos
Chlamydomonas reinhardtii/metabolismo , Complexos de Proteínas Captadores de Luz/metabolismo , Microscopia/métodos , Chlamydomonas reinhardtii/química , Clorofila/metabolismo , Clorofila A/metabolismo , Cloroplastos/metabolismo , Lasers , Luz , Complexos de Proteínas Captadores de Luz/química , Complexo de Proteína do Fotossistema I/química , Complexo de Proteína do Fotossistema I/metabolismo , Complexo de Proteína do Fotossistema II/química , Complexo de Proteína do Fotossistema II/metabolismo , Espectrometria de Fluorescência/métodos
4.
Cells ; 10(3)2021 03 21.
Artigo em Inglês | MEDLINE | ID: mdl-33801135

RESUMO

Cyanotoxins are harmful to aquatic and water-related organisms. In this study, Lemna trisulca was tested as a phytoremediation agent for three common cyanotoxins produced by bloom-forming cyanobacteria. Cocultivation of L. trisulca with Dolichospermum flos-aquae in BG11 medium caused a release of the intracellular pool of anatoxin-a into the medium and the adsorption of 92% of the toxin by the plant-after 14 days, the total amount of toxin decreased 3.17 times. Cocultivation with Raphidopsis raciborskii caused a 2.77-time reduction in the concentration of cylindrospermopsin (CYN) in comparison to the control (62% of the total pool of CYN was associated with the plant). The greatest toxin limitation was noted for cocultivation with Microcystis aeruginosa. After two weeks, the microcystin-LR (MC-LR) concentration decreased more than 310 times. The macrophyte also influenced the growth and development of cyanobacteria cells. Overall, 14 days of cocultivation reduced the biomass of D. flos-aquae, M. aeruginosa, and R. raciborskii by 8, 12, and 3 times, and chlorophyll a concentration in comparison to the control decreased by 17.5, 4.3, and 32.6 times, respectively. Additionally, the macrophyte stabilized the electrical conductivity (EC) and pH values of the water and affected the even uptake of cations and anions from the medium. The obtained results indicate the biotechnological potential of L. trisulca for limiting the development of harmful cyanobacterial blooms and their toxicity.


Assuntos
Alcaloides/isolamento & purificação , Araceae/metabolismo , Toxinas Marinhas/isolamento & purificação , Microcistinas/isolamento & purificação , Tropanos/isolamento & purificação , Poluentes Químicos da Água/isolamento & purificação , Biodegradação Ambiental , Biomassa , Clorofila A/metabolismo , Cianobactérias/metabolismo , Condutividade Elétrica , Concentração de Íons de Hidrogênio , Íons , Cinética , Fotossíntese
5.
PLoS One ; 16(4): e0250604, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33901250

RESUMO

While primary productivity in the oligotrophic North Pacific Subtropical Gyre (NPSG) is changing, the micro-size plankton community has not been evaluated in the last 4 decades, prompting a re-evaluation. We collected samples over three years (2016-2018) from depths of 10 to 200 m (n = 127), and the micro-size plankton were identified and counted to understand the heterogeneity of micro-size plankton community structure. The assemblages were consistent to the those of 4 decades ago. Dinophyceae (dinoflagellates) were the most numerically abundant, followed by Cryptophyceae and Bacillariophyceae (diatoms). The other micro-size plankton classes (Cyanophyceae, Haptophyceae, Dictyochophyceae, Euglenophyceae, and Prasinophyceae) were not always detected, whereas only Trichodesmium spp. was counted in the Cyanophyceae. Other unidentified autotrophic and heterotrophic flagellates were also significantly present, and their numeric abundance was higher than or at the same level as was that of the Dinophyceae. In the Dinophyceae, Gymnodiniaceae and Peridiniales were abundant. The chlorophyll a concentration and these class-level assemblages suggested micro-size plankton is not a major primary producer in this area. We applied generalized additive models (GAMs) and principal coordination analyses (PCoAs) to evaluate the habitats of every plankton group and the heterogeneity of the assemblages. The GAMs suggested that every classified plankton abundance showed a similar response to salinity, and we observed differences in habitats in terms of temperature and nitrate concentrations. Based on the PCoAs, we observed unique communities at the 200 m depth layer compared with those at the other sampling layers. The site scores of PCoAs indicated that the micro-size plankton assemblages are most heterogeneous at the 10 m depth layer. At such depth, diazotrophic Cyanophyceae (Trichodesmium spp.) are abundant, particularly in less-saline water. Therefore, nitrogen fixation may contribute to the heterogeneity in the abundance and assemblages in the western NPSG.


Assuntos
Diatomáceas/crescimento & desenvolvimento , Dinoflagelados/crescimento & desenvolvimento , Ecossistema , Clorofila A/metabolismo , Cianobactérias/crescimento & desenvolvimento , Cianobactérias/metabolismo , Diatomáceas/metabolismo , Dinoflagelados/metabolismo , Nitratos/química , Nitratos/metabolismo , Fixação de Nitrogênio , Oceano Pacífico , Análise de Componente Principal , Salinidade , Temperatura
6.
PLoS One ; 16(4): e0248715, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33826626

RESUMO

Based on the biological, nutrients and hydrological data in August 2018, the vertical chlorophyll a (Chl-a) concentration profiles and the relationship among surface Chl-a (Chl-a(0)) concentration, maximum Chl-a (Chl-a(m)) concentration and depth-integrated Chl-a (Chl-a(int)) concentration were studied in the Northern South China Sea (NSCS). The results indicate that there are 4 different patterns in the vertical Chl-a profiles in the NSCS: (i) Chl-a increases with depth from the surface (e.g. station 1); (ii) there exists subsurface chlorophyll maximum (SCM), with low Chl-a on the surface and at the bottom layers respectively (e.g. station 5); (iii) there is no SCM, only with high Chl-a on the surface and in the bottom (e.g. station 14); (iv) the 4th pattern is similar to (ii), with the higher Chl-a(0) (e.g. station 28). The SCM is observed at 95% stations in the NSCS and is not detected only at a few stations near the Pearl River (PR) estuary. These patterns are mainly regulated by alternative limitation of nutrients and light from the surface to the bottom of euphotic layer. For the pattern 1 (e.g. station 1), light is not a limited factor, and Chl-a and nutrients increase with depth. The pattern 2 (e.g. station 5) exists with the limitation of surface nutrients in offshore region. The nutrients increases with depth and the nutrients limitation turns to light limitation gradually from surface to bottom. And the SCM appears in the layer which need of the light and nutrients is roughly equivalent. Compared with that the offshore SCM, the nutrients for the pattern 3 (e.g. station 14) are rich on the surface with nutrients concentration and light irradiance. Therefore, it is seawater intrusion from the bottom that brings the higher nutrients concentration. The reason for the high Chl-a(0) on the pattern 4 (e.g. station 28) is terrestrial matter from the nearshore. High correlation (R2 = 0.5206, p<0.01) between the depth of SCM (Depth(m)) and Chl-a(0) indicates that the SCM depth is regulated by light masking effect of surface phytoplankton, generally with shallow nutriclines and fast light attenuation for high Chl-a(0) and vice versa low Chl-a(0) brings deeper nutriclines and light attenuate slowly with less shading effect. Further research results shows that Chl-a(int) and Chl-a(m) have a good correlation(R2 = 0.6397, p<0.01). However, the correlation between Chl-a(int) and Chl-a(0) is relative weak (R2 = 0.3202, p<0.01). That could be attributed to the availability of nutrients playing an important role in growth of phytoplankton, with high nutrients at upper euphotic layers for the stations with high Chl-a(0).


Assuntos
Clorofila A/metabolismo , Estuários , Fitoplâncton/crescimento & desenvolvimento , Estações do Ano , China , Clorofila A/análise
7.
Toxins (Basel) ; 13(4)2021 04 20.
Artigo em Inglês | MEDLINE | ID: mdl-33924256

RESUMO

Microplastics (MP) widely distributed in aquatic environments have adverse effects on aquatic organisms. Currently, the impact of MP on toxigenic red tide microalgae is poorly understood. In this study, the strain of Alexandrium pacificum ATHK, typically producing paralytic shellfish toxins (PST), was selected as the target. Effects of 1 and 0.1 µm polystyrene MP with three concentration gradients (5 mg L-1, 25 mg L-1 and 100 mg L-1) on the growth, chlorophyll a (Chl a), photosynthetic activity (Fv/Fm) and PST production of ATHK were explored. Results showed that the high concentration (100 mg L-1) of 1 µm and 0.1 µm MP significantly inhibited the growth of ATHK, and the inhibition depended on the size and concentration of MP. Contents of Chl a showed an increase with various degrees after MP exposure in all cases. The photosynthesis indicator Fv/Fm of ATHK was significantly inhibited in the first 11 days, then gradually returned to the level of control group at day 13, and finally was gradually inhibited in the 1 µm MP treatments, and promotion or inhibition to some degree also occurred at different periods after exposure to 0.1 µm MP. Overall, both particle sizes of MP at 5 and 25 mg L-1 had no significant effect on cell toxin quota, and the high concentration 100 mg L-1 significantly promoted the PST biosynthesis on the day 7, 11 and 15. No significant difference occurred in the cell toxin quota and the total toxin content in all treatments at the end of the experiment (day 21). All MP treatments did not change the toxin profiles of ATHK, nor did the relative molar percentage of main PST components. The growth of ATHK, Chl a content, Fv/Fm and toxin production were not affected by MP shading. This is the first report on the effects of MP on the PST-producing microalgae, which will improve the understanding of the adverse impact of MP on the growth and toxin production of A. pacificum.


Assuntos
Dinoflagelados/efeitos dos fármacos , Toxinas Marinhas/metabolismo , Microalgas/efeitos dos fármacos , Microplásticos/toxicidade , Fotossíntese/efeitos dos fármacos , Poliestirenos/toxicidade , Intoxicação por Frutos do Mar , Poluentes Químicos da Água/toxicidade , Clorofila A/metabolismo , Dinoflagelados/crescimento & desenvolvimento , Dinoflagelados/metabolismo , Microalgas/crescimento & desenvolvimento , Microalgas/metabolismo , Fatores de Tempo
8.
Nat Commun ; 12(1): 2069, 2021 04 06.
Artigo em Inglês | MEDLINE | ID: mdl-33824308

RESUMO

The oxygenation of early Earth's atmosphere during the Great Oxidation Event, is generally accepted to have been caused by oceanic Cyanobacterial oxygenic photosynthesis. Recent studies suggest that Fe(II) toxicity delayed the Cyanobacterial expansion necessary for the GOE. This study investigates the effects of Fe(II) on two Cyanobacteria, Pseudanabaena sp. PCC7367 and Synechococcus sp. PCC7336, in a simulated shallow-water marine Archean environment. A similar Fe(II) toxicity response was observed as reported for closed batch cultures. This toxicity was not observed in cultures provided with continuous gaseous exchange that showed significantly shorter doubling times than the closed-culture system, even with repeated nocturnal addition of Fe(II) for 12 days. The green rust (GR) formed under high Fe(II) conditions, was not found to be directly toxic to Pseudanabaena sp. PCC7367. In summary, we present evidence of diurnal Fe cycling in a simulated shallow-water marine environment for two ancestral strains of Cyanobacteria, with increased O2 production under anoxic conditions.


Assuntos
Organismos Aquáticos/metabolismo , Archaea/metabolismo , Ritmo Circadiano , Ferro/metabolismo , Oxigênio/metabolismo , Organismos Aquáticos/efeitos dos fármacos , Organismos Aquáticos/crescimento & desenvolvimento , Archaea/efeitos dos fármacos , Archaea/crescimento & desenvolvimento , Atmosfera , Clorofila A/metabolismo , Ferro/toxicidade , Modelos Biológicos , Água do Mar
9.
Biochim Biophys Acta Bioenerg ; 1862(7): 148424, 2021 07 01.
Artigo em Inglês | MEDLINE | ID: mdl-33785317

RESUMO

Recent studies on Photosystem I (PS I) have shown that the six core chlorophyll a molecules are highly coupled, allowing for efficient creation and stabilization of the charge-separated state. One area of particular interest is the identity and function of the primary acceptor, A0, as the factors that influence its ultrafast processes and redox properties are not yet fully elucidated. It was recently shown that A0 exists as a dimer of the closely-spaced Chl2/Chl3 molecules wherein the reduced A0- state has an asymmetric distribution of electron spin density that favors Chl3. Previous experimental work in which this ligand was changed to a hard base (histidine, M688HPsaA) revealed severely impacted electron transfer processes at both the A0 and A1 acceptors; molecular dynamics simulations further suggested two distinct conformations of PS I in which the His residue coordinates and forms a hydrogen bond to the A0 and A1 cofactors, respectively. In this study, we have applied 2D HYSCORE spectroscopy in conjunction with molecular dynamics simulations and density functional theory calculations to the study of the M688HPsaA variant. Analysis of the hyperfine parameters demonstrates that the His imidazole serves as the axial ligand to the central Mg2+ ion in Chl3A in the M688HPsaA variant. Although the change in ligand identity does not alter delocalization of electron density over the Chl2/Chl3 dimer, a small shift in the asymmetry of delocalization, coupled with the electron withdrawing properties of the ligand, most likely accounts for the inhibition of forward electron transfer in the His-ligated conformation.


Assuntos
Clorofila A/metabolismo , Elétrons , Histidina/metabolismo , Imidazóis/metabolismo , Complexo de Proteína do Fotossistema I/química , Complexo de Proteína do Fotossistema I/metabolismo , Clorofila A/química , Transporte de Elétrons , Histidina/química , Ligação de Hidrogênio , Imidazóis/química , Cinética , Ligantes , Simulação de Dinâmica Molecular , Mutagênese Sítio-Dirigida , Oxirredução , Complexo de Proteína do Fotossistema I/genética
10.
J Photochem Photobiol B ; 217: 112145, 2021 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-33735745

RESUMO

Photophysiological responses of phytoplankton to changing multiple environmental drivers are essential in understanding and predicting ecological consequences of ocean climate changes. In this study, we investigated the combined effects of two CO2 levels (410 and 925 µatm) and five light intensities (80 to 480 µmol photons m-2 s-1) on cellular pigments contents, photosynthesis and calcification of the coccolithophore Emiliania huxleyi grown under nutrient replete and limited conditions, respectively. Our results showed that high light intensity, high CO2 level and nitrate limitation acted synergistically to reduce cellular chlorophyll a and carotenoid contents. Nitrate limitation predominantly enhanced calcification rate; phosphate limitation predominantly reduced photosynthetic carbon fixation rate, with larger extent of the reduction under higher levels of CO2 and light. Reduced availability of both nitrate and phosphate under the elevated CO2 concentration decreased saturating light levels for the cells to achieve the maximal relative electron transport rate (rETRmax). Light-saturating levels for rETRmax were lower than that for photosynthetic and calcification rates under the nutrient limitation. Regardless of the culture conditions, rETR under growth light levels correlated linearly and positively with measured photosynthetic and calcification rates. Our findings imply that E. huxleyi cells acclimated to macro-nutrient limitation and elevated CO2 concentration decreased their light requirement to achieve the maximal electron transport, photosynthetic and calcification rates, indicating a photophysiological strategy to cope with CO2 rise/pH drop in shoaled upper mixing layer above the thermocline where the microalgal cells are exposed to increased levels of light and decreased levels of nutrients.


Assuntos
Dióxido de Carbono/farmacologia , Haptófitas/crescimento & desenvolvimento , Luz , Nutrientes/química , Fotossíntese/efeitos dos fármacos , Calcificação Fisiológica/efeitos dos fármacos , Calcificação Fisiológica/efeitos da radiação , Clorofila A/metabolismo , Transporte de Elétrons , Haptófitas/metabolismo , Concentração de Íons de Hidrogênio , Nutrientes/deficiência , Fotossíntese/efeitos da radiação
11.
Food Chem ; 354: 129571, 2021 Aug 30.
Artigo em Inglês | MEDLINE | ID: mdl-33761337

RESUMO

The physicochemical properties, including nutrient and bioactive compound compositions, in fruit of four creole avocados (CA) from Mexico were determined and compared with those of 'Hass' fruit. 'Hass' pulp and some CA pulps contained similar concentrations of lutein, chlorophyll a, ß-sitosterol and α-tocopherol. CA pulp contained 3.91-9.55% more oil than 'Hass'. Oil from CA pulp contained 10.10-26.79% more oleic acid than 'Hass' pulp. However, CA were small (CA = 81.40-137.15 g, 'Hass' = 188.59 g) and their pulp contents were low (CA = 39.83-84.82 g, 'Hass' = 144.14 g). CA peels were very thin, making these avocado peels edible but prone to mechanical damage. CA peels also contained higher concentrations and greater diversity of anthocyanins and glycosylated quercetin compounds than 'Hass' peels. Some CA were particularly rich in mannoheptulose and perseitol. Consumption of CA, including their peel, might result in higher intakes of some nutrients and bioactive compounds compared with 'Hass' avocados.


Assuntos
Frutas/metabolismo , Metabolômica , Persea/metabolismo , Antocianinas/metabolismo , Clorofila A/metabolismo , México
12.
J Biochem ; 169(6): 709-719, 2021 Sep 07.
Artigo em Inglês | MEDLINE | ID: mdl-33537746

RESUMO

To understand the physiological role of NADPH-thioredoxin reductase C (NTRC) in cyanobacteria, we investigated an NTRC-deficient mutant strain of Anabaena sp., PCC 7120, cultivated under different regimes of nitrogen supplementation and light exposure. The deletion of ntrC did not induce a change in the cell structure and metabolic pathways. However, time-dependent changes in the abundance of specific proteins and metabolites were observed. A decrease in chlorophyll a was correlated with a decrease in chlorophyll a biosynthesis enzymes and photosystem I subunits. The deletion of ntrC led to a deregulation of nitrogen metabolism, including the NtcA accumulation and heterocyst-specific proteins while nitrate ions were available in the culture medium. Interestingly, this deletion resulted in a redox imbalance, indicated by higher peroxide levels, higher catalase activity and the induction of chaperones such as MsrA. Surprisingly, the antioxidant protein 2-CysPrx was downregulated. The deficiency in ntrC also resulted in the accumulation of metabolites such as 6-phosphogluconate, ADP and ATP. Higher levels of NADP+ and NADPH partly correlated with higher G6PDH activity. Rather than impacting protein expression levels, NTRC appears to be involved in the direct regulation of enzymes, especially during the dark-to-light transition period.


Assuntos
Anabaena/genética , Anabaena/metabolismo , Proteínas de Bactérias/metabolismo , NADP/metabolismo , Nitrogênio/metabolismo , Complexo de Proteína do Fotossistema I/metabolismo , Tiorredoxina Dissulfeto Redutase/metabolismo , Anabaena/crescimento & desenvolvimento , Proteínas de Bactérias/genética , Clorofila A/metabolismo , Luz , Tiorredoxina Dissulfeto Redutase/genética
13.
mBio ; 12(1)2021 02 16.
Artigo em Inglês | MEDLINE | ID: mdl-33593975

RESUMO

Oxygenic photosynthetic organisms have evolved a multitude of mechanisms for protection against high-light stress. IsiA, a chlorophyll a-binding cyanobacterial protein, serves as an accessory antenna complex for photosystem I. Intriguingly, IsiA can also function as an independent pigment protein complex in the thylakoid membrane and facilitate the dissipation of excess energy, providing photoprotection. The molecular basis of the IsiA-mediated excitation quenching mechanism remains poorly understood. In this study, we demonstrate that IsiA uses a novel cysteine-mediated process to quench excitation energy. The single cysteine in IsiA in the cyanobacterium Synechocystis sp. strain PCC 6803 was converted to a valine. Ultrafast fluorescence spectroscopic analysis showed that this single change abolishes the excitation energy quenching ability of IsiA, thus providing direct evidence of the crucial role of this cysteine residue in energy dissipation from excited chlorophylls. Under stress conditions, the mutant cells exhibited enhanced light sensitivity, indicating that the cysteine-mediated quenching process is critically important for photoprotection.IMPORTANCE Cyanobacteria, oxygenic photosynthetic microbes, constantly experience varying light regimes. Light intensities higher than those that saturate the photosynthetic capacity of the organism often lead to redox damage to the photosynthetic apparatus and often cell death. To meet this challenge, cyanobacteria have developed a number of strategies to modulate light absorption and dissipation to ensure maximal photosynthetic productivity and minimal photodamage to cells under extreme light conditions. In this communication, we have determined the critical role of a novel cysteine-mediated mechanism for light energy dissipation in the chlorophyll protein IsiA.


Assuntos
Proteínas de Bactérias/genética , Clorofila A/metabolismo , Cianobactérias/metabolismo , Cisteína/metabolismo , Complexos de Proteínas Captadores de Luz/genética , Luz , Proteínas de Bactérias/metabolismo , Cisteína/genética , Complexos de Proteínas Captadores de Luz/metabolismo , Oxirredução , Fotossíntese , Complexo de Proteína do Fotossistema I/metabolismo , Ligação Proteica , Espectrometria de Fluorescência , Valina/genética , Valina/metabolismo
14.
Biochim Biophys Acta Bioenerg ; 1862(5): 148384, 2021 05 01.
Artigo em Inglês | MEDLINE | ID: mdl-33545114

RESUMO

The siphonaxanthin-siphonein-chlorophyll-a/b-binding protein (SCP), a trimeric light-harvesting complex isolated from photosystem II of the siphonous green alga Codium fragile, binds the carotenoid siphonaxanthin (Sx) and/or its ester siphonein in place of lutein, in addition to chlorophylls a/b and neoxanthin. SCP exhibits a higher content of chlorophyll b (Chl-b) than its counterpart in green plants, light-harvesting complex II (LHCII), increasing the relative absorption of blue-green light for photosynthesis. Using low temperature absorption and resonance Raman spectroscopies, we reveal the presence of two non-equivalent Sx molecules in SCP, and assign their absorption peaks at 501 and 535 nm. The red-absorbing Sx population exhibits a significant distortion that is reminiscent of lutein 2 in trimeric LHCII. Unexpected enhancement of the Raman modes of Chls-b in SCP allows an unequivocal description of seven to nine non-equivalent Chls-b, and six distinct Chl-a populations in this protein.


Assuntos
Clorofila A/metabolismo , Clorofila/metabolismo , Clorófitas/metabolismo , Complexos de Proteínas Captadores de Luz/metabolismo , Complexo de Proteína do Fotossistema II/metabolismo , Pigmentos Biológicos/química , Xantofilas/metabolismo , Fotossíntese , Pigmentos Biológicos/metabolismo
15.
PLoS One ; 16(2): e0238013, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33529253

RESUMO

Direct measurements of gross primary productivity (GPP) in the water column are essential, but can be spatially and temporally restrictive. Fast repetition rate fluorometry (FRRf) is a bio-optical technique based on chlorophyll a (Chl-a) fluorescence that can estimate the electron transport rate (ETRPSII) at photosystem II (PSII) of phytoplankton in real time. However, the derivation of phytoplankton GPP in carbon units from ETRPSII remains challenging because the electron requirement for carbon fixation (Фe,C), which is mechanistically 4 mol e- mol C-1 or above, can vary depending on multiple factors. In addition, FRRf studies are limited in freshwater lakes where phosphorus limitation and cyanobacterial blooms are common. The goal of the present study is to construct a robust Фe,C model for freshwater ecosystems using simultaneous measurements of ETRPSII by FRRf with multi-excitation wavelengths coupled with a traditional carbon fixation rate by the 13C method. The study was conducted in oligotrophic and mesotrophic parts of Lake Biwa from July 2018 to May 2019. The combination of excitation light at 444, 512 and 633 nm correctly estimated ETRPSII of cyanobacteria. The apparent range of Фe,C in the phytoplankton community was 1.1-31.0 mol e- mol C-1 during the study period. A generalised linear model showed that the best fit including 12 physicochemical and biological factors explained 67% of the variance in Фe,C. Among all factors, water temperature was the most significant, while photosynthetically active radiation intensity was not. This study quantifies the in situ FRRf method in a freshwater ecosystem, discusses core issues in the methodology to calculate Фe,C, and assesses the applicability of the method for lake GPP prediction.


Assuntos
Fluorometria/métodos , Fotossíntese/fisiologia , Fitoplâncton/crescimento & desenvolvimento , Carbono , Ciclo do Carbono , Clorofila/metabolismo , Clorofila A/metabolismo , Cianobactérias/crescimento & desenvolvimento , Ecossistema , Transporte de Elétrons/fisiologia , Elétrons , Japão , Lagos , Modelos Teóricos , Complexo de Proteína do Fotossistema II/metabolismo , Temperatura
16.
PLoS One ; 16(2): e0246719, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33571231

RESUMO

Discharge reduction, as caused by water diversion for hydropower, and fine sediments deposition, are prevalent stressors that may affect multiple ecosystem functions in streams. Periphytic biofilms play a key role in stream ecosystem functioning and are potentially affected by these stressors and their interaction. We experimentally assessed the interactive effects of discharge and fine sediments on biofilm metabolism in artificial indoor channels using a factorial split-plot design with two explanatory variables: water discharge (20, 39, 62, 141 and 174 cm3 s-1) and fine sediments (no sediment or 1100 mg L-1 of sediments). We incubated artificial tiles for 25 days in an unpolluted stream to allow biofilm colonization, and then placed them into the indoor channels for acclimation for 18 days. Subsequently, we manipulated water discharge and fine sediments and, after 17 days, we measured biofilm chlorophyll-a concentration and metabolism. Water velocity (range, 0.5 to 3.0 cm s-1) and sediment deposition (range, 6.1 to 16.6 mg cm-2) increased with discharge, the latter showing that the effect of increased inputs prevailed over sloughing. In the no-sediment treatments, discharge did not affect biofilm metabolism, but reduced chlorophyll-a. Sediments, probably as a consequence of nutrients released, promoted metabolism of biofilm and chlorophyll-a, which became independent of water discharge. Our results indicate that pulses of fine sediments can promote biofilm algal biomass and metabolism, but show interactive effects with discharge. Although discharge reduction can affect the abundance of basal resources for food webs, its complex interactions with fine sediments make it difficult to forecast the extent and direction of the changes.


Assuntos
Biofilmes/crescimento & desenvolvimento , Clorófitas/fisiologia , Sedimentos Geológicos/microbiologia , Rios/microbiologia , Biodiversidade , Biomassa , Clorofila A/metabolismo , Clorófitas/metabolismo , Sedimentos Geológicos/análise , Rios/química
17.
Lett Appl Microbiol ; 72(5): 619-625, 2021 May.
Artigo em Inglês | MEDLINE | ID: mdl-33566365

RESUMO

Improving the growth and pigment accumulation of microalgae by electrochemical approaches was considered a novel and promising method. In this research, we investigated the effect of conductive polymer poly (3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) dispersible in water on growth and pigment accumulation of Haematococcus lacustris and Euglena gracilis. The results revealed that effect of PEDOT:PSS was strongly cell-dependent and each cell type has its own peculiar response. For H. lacustris, the cell density in the 50 mg·l-1 treatment group increased by 50·27%, and the astaxanthin yield in the 10 mg·l-1 treatment group increased by 37·08%. However, under the high concentrations of PEDOT:PSS treatment, cell growth was significantly inhibited, and meanwhile, the smaller and more active zoospores were observed, which reflected the changes in cell life cycle and growth mode. Cell growth of E. gracilis in all the PEDOT:PSS treatment groups were notably inhibited. Chlorophyll a content in E. gracilis decreased while chlorophyll b content increased in response to the PEDOT:PSS treatment. The results laid a foundation for further development of electrochemical methods to promote microalgae growth and explore the interactions between conductive polymers and microalgae cells.


Assuntos
Compostos Bicíclicos Heterocíclicos com Pontes/farmacologia , Proliferação de Células/efeitos dos fármacos , Clorofíceas/crescimento & desenvolvimento , Euglena gracilis/crescimento & desenvolvimento , Polímeros/farmacologia , Poliestirenos/farmacologia , Tiofenos/farmacologia , Compostos Bicíclicos Heterocíclicos com Pontes/química , Clorofíceas/efeitos dos fármacos , Clorofila/metabolismo , Clorofila A/metabolismo , Condutividade Elétrica , Técnicas Eletroquímicas , Euglena gracilis/efeitos dos fármacos , Polímeros/química , Xantofilas/metabolismo
18.
Microb Cell Fact ; 20(1): 14, 2021 Jan 12.
Artigo em Inglês | MEDLINE | ID: mdl-33430874

RESUMO

BACKGROUND: Chlorophyllase catalyzes the hydrolysis of chlorophyll and produces chlorophyllide and phytol. Cyanobacterial chlorophyllases are likely to be more highly heterologously expressed than plant chlorophyllases. A novel recombinant chlorophyllase from the cyanobacterium Oscillatoria acuminata PCC 6304 was successfully expressed in Escherichia coli BL21(DE3). RESULTS: The putative N-terminal 28-amino-acid signal peptide sequence of O. acuminata chlorophyllase (OaCLH) is essential for its activity, but may confer poor solubility on OaCLH. The C-terminal fusion of a 6 × His tag caused a partial loss of activity in recombinant OaCLH, but an N-terminal 6 × His tag did not destroy its activity. The optimal pH and temperature for recombinant OaCLH activity are 7.0 and 40 °C, respectively. Recombinant OaCLH has hydrolysis activities against chlorophyll a, chlorophyll b, bacteriochlorophyll a, and pheophytin a, but prefers chlorophyll b and chlorophyll a as substrates. The results of site-directed mutagenesis experiments indicated that the catalytic triad of OaCLH consists of Ser159, Asp226, and His258. CONCLUSIONS: The high-level expression and broad substrate specificity of recombinant OaCLH make it suitable for genetically engineering and a promising biocatalyst for industrial production, with applications in vegetable oil refining and laundry detergents.


Assuntos
Proteínas de Bactérias/metabolismo , Hidrolases de Éster Carboxílico/metabolismo , Clorofila A/metabolismo , Clorofila/metabolismo , Oscillatoria/enzimologia , Proteínas Recombinantes/metabolismo , Sequência de Aminoácidos , Proteínas de Bactérias/química , Proteínas de Bactérias/genética , Biocatálise , Hidrolases de Éster Carboxílico/química , Hidrolases de Éster Carboxílico/genética , Clonagem Molecular , Escherichia coli/genética , Concentração de Íons de Hidrogênio , Hidrólise , Cinética , Modelos Moleculares , Oscillatoria/genética , Estrutura Terciária de Proteína , Proteínas Recombinantes/química , Homologia de Sequência de Aminoácidos , Especificidade por Substrato , Temperatura
19.
Plant Sci ; 303: 110774, 2021 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-33487358

RESUMO

Hydrogen peroxide priming has emerged as a powerful strategy to trigger multiple responses involved in plant acclimation that reinforce tolerance to abiotic stresses, including salt stress. Thus, this study aimed to investigate the impact of foliar H2O2 priming on the physiological, biochemical, and ultrastructural traits related to photosynthesis of salt-stressed plants. Besides, we provided comparative leaf metabolomic profiles of Zea mays plants under such conditions. For this, H2O or H2O2 pretreated plants were grown under saline conditions for 12-days. Salinity drastically affected photosynthetic parameters and structural chloroplasts integrity, also increased reactive oxygen species contents promoting disturbance in the plant metabolism when compared to non-saline conditions. Our results suggest that H2O2-pretreated plants improved photosynthetic performance avoiding salinity-induced energy excess and ultrastructural damage by preserving stacking thylakoids. It displayed modulation of some metabolites, as arabitol, glucose, asparagine, and tyrosine, which may contribute to the maintenance of osmotic balance and reduced oxidative stress. Hence, our study brings new insights into an understanding of plant acclimation to salinity by H2O2 priming based on photosynthesis maintenance and metabolite modulation.


Assuntos
Cloroplastos/efeitos dos fármacos , Peróxido de Hidrogênio/farmacologia , Zea mays/metabolismo , Clorofila A/metabolismo , Cloroplastos/metabolismo , Cloroplastos/ultraestrutura , Metabolômica , Microscopia Eletrônica de Transmissão , Pressão Osmótica , Fosfoenolpiruvato Carboxilase/metabolismo , Fotossíntese , Espécies Reativas de Oxigênio/metabolismo , Tolerância ao Sal , Zea mays/efeitos dos fármacos , Zea mays/fisiologia
20.
Nat Commun ; 12(1): 679, 2021 01 29.
Artigo em Inglês | MEDLINE | ID: mdl-33514722

RESUMO

Diverse algae of the red lineage possess chlorophyll a-binding proteins termed LHCR, comprising the PSI light-harvesting system, which represent an ancient antenna form that evolved in red algae and was acquired through secondary endosymbiosis. However, the function and regulation of LHCR complexes remain obscure. Here we describe isolation of a Nannochloropsis oceanica LHCR mutant, named hlr1, which exhibits a greater tolerance to high-light (HL) stress compared to the wild type. We show that increased tolerance to HL of the mutant can be attributed to alterations in PSI, making it less prone to ROS production, thereby limiting oxidative damage and favoring growth in HL. HLR1 deficiency attenuates PSI light-harvesting capacity and growth of the mutant under light-limiting conditions. We conclude that HLR1, a member of a conserved and broadly distributed clade of LHCR proteins, plays a pivotal role in a dynamic balancing act between photoprotection and efficient light harvesting for photosynthesis.


Assuntos
Adaptação Fisiológica/genética , Proteínas de Ligação à Clorofila/metabolismo , Luz/efeitos adversos , Complexo de Proteína do Fotossistema I/metabolismo , Estramenópilas/fisiologia , Adaptação Fisiológica/efeitos da radiação , Clorofila A/metabolismo , Proteínas de Ligação à Clorofila/genética , Proteínas de Ligação à Clorofila/isolamento & purificação , Mutação , Fotossíntese/genética , Fotossíntese/efeitos da radiação , Complexo de Proteína do Fotossistema I/genética , Estramenópilas/efeitos da radiação
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