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1.
Plant Dis ; 104(1): 161-167, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31660796

RESUMO

Orange cane blotch (OCB), an algal disease on commercial blackberry plants in the southeastern United States, has been an increasing concern among producers. The causal agent, Cephaleuros virescens, produces brightly colored green to orange lesions on blackberry stems, but proof of actual damage and impact on crop yield has not been documented. Naturally infected stem sections were viewed using transmission and scanning electron microscopy to evaluate cane damage. Surface abrasions, intercellular growth, and occasional intracellular growth were observed on the surface and epidermal layers. Field studies at four commercial sites over 2 years were conducted to assess the impact of OCB on yield in 'Ouachita' blackberry plants not treated with algicidal chemicals. Neither cane diameter nor berry size was impacted by severity of OCB; however, berry number decreased with increasing OCB intensity in a nonlinear manner, thereby resulting in reduced yields.


Assuntos
Clorófitas , Doenças das Plantas , Rubus , Agricultura , Clorófitas/fisiologia , Frutas , Georgia , Doenças das Plantas/parasitologia , Rubus/parasitologia
2.
Int J Mol Sci ; 20(18)2019 Sep 13.
Artigo em Inglês | MEDLINE | ID: mdl-31540290

RESUMO

Following the physiological complementary/parallel Celis-Plá et al., by inhibiting extracellular signal regulated kinases (ERK), c-Jun N-terminal kinases (JNK), and cytokinin specific binding protein (p38), we assessed the role of the mitogen-activated protein kinases (MAPK) pathway in detoxification responses mediated by chronic copper (10 µM) in U. compressa. Parameters were taken at 6, 24, and 48 h, and 6 days (d). H2O2 and lipid peroxidation under copper and inhibition of ERK, JNK, or p38 alone increased but recovered by the sixth day. By blocking two or more MAPKs under copper, H2O2 and lipid peroxidation decayed even below controls. Inhibition of more than one MAPK (at 6 d) caused a decrease in total glutathione (reduced glutathione (GSH) + oxidised glutathione (GSSG)) and ascorbate (reduced ascorbate (ASC) + dehydroascorbate (DHA)), although in the latter it did not occur when the whole MAPK was blocked. Catalase (CAT), superoxide dismutase (SOD), thioredoxin (TRX) ascorbate peroxidase (APX), dehydroascorbate reductase (DHAR), and glutathione synthase (GS), were downregulated when blocking more than one MAPK pathway. When one MAPK pathway was blocked under copper, a recovery and even enhancement of detoxification mechanisms was observed, likely due to crosstalk within the MAPKs and/or other signalling processes. In contrast, when more than one MAPK pathway were blocked under copper, impairment of detoxification defences occurred, demonstrating that MAPKs were key signalling mechanisms for detoxification in macroalgae.


Assuntos
Clorófitas/fisiologia , Cobre/metabolismo , Sistema de Sinalização das MAP Quinases , Ácido Ascórbico/metabolismo , Biodegradação Ambiental , Clorófitas/metabolismo , Regulação da Expressão Gênica de Plantas , Glutationa/metabolismo , Peróxido de Hidrogênio/metabolismo , Peroxidação de Lipídeos
3.
Int J Mol Sci ; 20(18)2019 Sep 13.
Artigo em Inglês | MEDLINE | ID: mdl-31540294

RESUMO

There is currently no information regarding the role that whole mitogen activated protein kinase (MAPK) pathways play in counteracting environmental stress in photosynthetic organisms. To address this gap, we exposed Ulva compressa to chronic levels of copper (10 µM) specific inhibitors of Extracellular Signal Regulated Kinases (ERK), c-Jun N-terminal Kinases (JNK), and Cytokinin Specific Binding Protein (p38) MAPKs alone or in combination. Intracellular copper accumulation and photosynthetic activity (in vivo chlorophyll a fluorescence) were measured after 6 h, 24 h, 48 h, and 6 days of exposure. By day 6, when one (except JNK) or more of the MAPK pathways were inhibited under copper stress, there was a decrease in copper accumulation compared with algae exposed to copper alone. When at least two MAPKs were blocked, there was a decrease in photosynthetic activity expressed in lower productivity (ETRmax), efficiency (αETR), and saturation of irradiance (EkETR), accompanied by higher non-photochemical quenching (NPQmax), compared to both the control and copper-only treatments. In terms of accumulation, once the MAPK pathways were partially or completely blocked under copper, there was crosstalk between these and other signaling mechanisms to enhance metal extrusion/exclusion from cells. Crosstalk occurred among MAPK pathways to maintain photosynthesis homeostasis, demonstrating the importance of the signaling pathways for physiological performance. This study is complemented by a parallel/complementary article Rodríguez-Rojas et al. on the role of MAPKs in copper-detoxification.


Assuntos
Clorófitas/fisiologia , Cobre/metabolismo , Sistema de Sinalização das MAP Quinases , Biodegradação Ambiental , Clorófitas/metabolismo , Sistema de Sinalização das MAP Quinases/efeitos dos fármacos , Fotossíntese/efeitos dos fármacos , Inibidores de Proteínas Quinases/farmacologia
4.
Sci Total Environ ; 693: 133650, 2019 Nov 25.
Artigo em Inglês | MEDLINE | ID: mdl-31377356

RESUMO

Advanced sewage treatment by microalgae is regarded as a promising method for addressing eutrophication. To improve sewage treatment, three kinds of plant hormones including auxin (indole-3-acetic acid, IAA), cytokinin (Zeatin), and brassinosteroid, were chosen to measure the influence of plant hormones on nitrogen and phosphorus removal by Tetraselmis cordiformis and to analyze their mechanisms, including photosynthesis, nutrient metabolism, and gene transcription. The results indicated that the maximal removal efficiencies of total nitrogen and phosphate by T. cordiformis were elevated by the plant hormones by 184.3% and 53.2%, respectively. The chlorophyll a content was increased by 1.1 times by the plant hormones in comparison with the control. Moreover, after being stimulated by plant hormones, the activities of nitrate reductase (NR) and glutamine synthetase (GS) increased by 90.4% and 82.1%, respectively, in comparison with the control. Supplementation with plant hormones also significantly elevated the mRNA expression level of GS-related gene by 30.9%. This study demonstrated that plant hormones could significantly promote the nutrient removal of microalgae for sewage treatment in artificial laboratory conditions and provided theoretical support for its further practical full-scale application under variable conditions.


Assuntos
Biodegradação Ambiental , Clorófitas/fisiologia , Eliminação de Resíduos Líquidos/métodos , Nitrogênio , Fósforo , Reguladores de Crescimento de Planta , Esgotos
5.
Mar Pollut Bull ; 149: 110528, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31470209

RESUMO

In this study, we used flow cytometry to examine how incubation in dark versus light affects the vitality and viability of UV-irradiated Tetraselmis suecica. High UV doses (300 and 400 mJ/cm2) affected the esterase activity, membrane permeability, and chlorophyll content more when the subsequent incubation took place in light. For non- or low UV dose (100 and 200 mJ/cm2)-treated cells, incubation in light resulted in cell regrowth as compared to incubation in dark. Damaged cells (enzymatically active but with permeable membranes) did not recover when incubated under light or dark conditions. Exposure to light reduces the evaluation time of any given ballast water treatment, as viable cells will be detected at an earlier stage and the vitality is more affected. When evaluating the performance of UV-based ballast water treatment systems (BWTS), these results can be useful for type approval using T. suecica as a test organism in the test regime.


Assuntos
Clorófitas/fisiologia , Clorófitas/efeitos da radiação , Purificação da Água/métodos , Clorofila/metabolismo , Escuridão , Relação Dose-Resposta à Radiação , Esterases/metabolismo , Citometria de Fluxo/métodos , Fluoresceínas , Luz , Fitoplâncton/fisiologia , Fitoplâncton/efeitos da radiação , Raios Ultravioleta
6.
Artigo em Inglês | MEDLINE | ID: mdl-31362358

RESUMO

Seagrasses are a crucial indicator species of coastal marine ecosystems that provide substratum, shelter, and food for epiphytic algae, invertebrates, and fishes. More accurate mapping of seagrasses is essential for their survival as a long-lasting natural resource. Before reflectance spectra could properly be used as remote sensing endmembers, factors that may obscure the detection of reflectance signals must be assessed. The objectives in this study are to determine the influence of (1) epiphytes, (2) water depth, and (3) seagrass genus on the detection of reflectance spectral signals. The results show that epiphytes significantly dampen bottom-type reflectance throughout most of the visible light spectrum, excluding 670-679 nm; the depth does influence reflectance, with the detection of deeper seagrasses being easier, and as the depth increases, only Heterozostera increase in the exact "red edge" wavelength at which there is a rapid change in the near-infrared (NIR) spectrum. These findings helped improve the detection of seagrass endmembers during remote sensing, thereby helping protect the natural resource of seagrasses.


Assuntos
Clorófitas/fisiologia , Ecossistema , Poaceae/fisiologia , Tecnologia de Sensoriamento Remoto , Análise Espectral/métodos , Animais , Demografia , Oceanos e Mares , Austrália do Sul
7.
Ecotoxicol Environ Saf ; 182: 109413, 2019 Oct 30.
Artigo em Inglês | MEDLINE | ID: mdl-31284121

RESUMO

The effects of rhamnolipids (RLs) produced and further purified from Burkholderia thailandensis, on the unicellular microalgae Dunaliella tertiolecta were investigated, in terms of RLs ability to affect algal growth, photosynthetic apparatus structure and energy flux, round and through photosystems II and I. Specifically, 24-48 h RLs-treated algae (RLs at concentrations ranged from 5 to 50 mg L-1) showed significantly decreased levels of growth rate, while increased levels of Chl a and b were obtained only in 72-96 h RLs-treated algae. Similarly, although no changes were obtained in the Chl a/b ratio and almost all chlorophyll fluorescence parameters over time, yields of electron transport (ϕR0, ϕE0) and respective performance index (PItotal) were negatively affected at 72 and 96 h. Based on those findings, it seems that the inhibitory effect of RLs on the algae growth rate after 24 and 48 h and the gradual attenuation of the phenomenon (after 72 h of exposure), may indicate the initial response of the organism, as well as algae ability to overcome, since RLs showed no effects on algae photosynthetic ability. Those findings reveal for the first time that RLs from Burkholderia thailandensis are not harmful for Dunaliella tertiolecta. However, further studies with the use of more aquatic species could be essential for assessing the RLs-mediated effects on aquatic biota.


Assuntos
Burkholderia/fisiologia , Clorófitas/fisiologia , Glicolipídeos/toxicidade , Clorofíceas , Clorófitas/efeitos dos fármacos , Transporte de Elétrons , Fotossíntese , Complexo de Proteína do Fotossistema II
8.
Sci Total Environ ; 689: 287-294, 2019 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-31276996

RESUMO

Collaborations between multiple microbial species are important for understanding natural clearance and ecological effects of toxic organic contaminants in the environment. However, the interactions between different species in the transformation and degradation of contaminants remain to address. In this study, the effects of pyrene and its bacterial metabolites on the algal growth (Selenastrum capricornutum) were examined. The specific growth rate of algal cells incubated with bacterial pyrene metabolites (1.18 d-1) was highest among all treatment, followed by the controls (1.07 d-1), treated with pyrene-free bacterial metabolites (1.04 d-1) and those treated with pyrene (0.55 d-1). G1 phase is the key growth phase for the cells to synthesize biomolecules for subsequent cell division in the cell cycle. Approximately 76.9% of the cells treated with bacterial pyrene metabolites were at the G1 phase and significantly lower than those with the controls (85.3%), pyrene-free bacterial metabolites (85.5%) and pyrene treatment (92.5%). Transcriptomic analysis of algae showed that the expression of 47 ribosomal unigenes was down-regulated by 5 mg L-1 of pyrene, while 308 unigenes related to the preparation of cell division (DNA replication and protein synthesis) were up-regulated by bacterial pyrene metabolites. It indicated that basal metabolism associated with the growth and proliferation of algal cells could be significantly promoted by bacterial pyrene metabolites. Overall, this study suggests a close relationship between algae and bacteria in the transformation and ecological effects of toxic contaminants.


Assuntos
Divisão Celular/efeitos dos fármacos , Clorófitas/efeitos dos fármacos , Mycobacterium/metabolismo , Pirenos/metabolismo , Clorófitas/fisiologia , Pirenos/efeitos adversos
9.
Plant Physiol Biochem ; 141: 398-406, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31228796

RESUMO

The fruticose epiphytic lichen Seirophora villosa, strictly associated with Juniperus shrublands in the Mediterranean basin, was used to investigate the role of hairiness on a lichen thallus, as a characteristic morphological trait. We evaluated the effect of hair removal on the physiological parameters of a set of samples, during desiccation and on exposure to different salt concentrations. Hairy thalli were less affected by salt, suggesting that during dehydration, the presence of hair protects the thallus from light irradiance, oxidative stresses and the lipid peroxidation generated by free radicals, and could offer passive, but selective, water control. Our results showed that hair could not only increase thallus surface and promote water absorption when availability is low, but could also repel the salt dissolved in water by activating a passive resistance mechanism, by preventing salt entering.


Assuntos
Clorofila A/química , Líquens/fisiologia , Estresse Oxidativo , Estresse Salino , Antioxidantes/química , Carotenoides/química , Clorófitas/fisiologia , Desidratação , Depuradores de Radicais Livres/química , Peróxido de Hidrogênio/química , Peroxidação de Lipídeos , Malondialdeído/química , Região do Mediterrâneo , Fotossíntese , Espécies Reativas de Oxigênio/química , Espectrometria de Fluorescência , Água/química
10.
Sci Total Environ ; 687: 416-422, 2019 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-31212149

RESUMO

Algal cultures of Dictyosphaerium sp. were treated with a wide range (0-8 mg/L) of nonylphenol (NP) applications to investigate the species' potential to perform bioremediation of NP-contaminated wastewater and explore the mechanism of NP toxicity in algal cell. The algal species exhibited a high tolerance for NP and efficiently removed even high concentrations of NP. The accumulation of NP in algal cells tended to increase and the percentage of NP adhered to the cell walls tended to decrease as the NP concentration increased. The thylakoid density and the pyrenoid size also tended to decrease as the NP concentration rose. The key genes involved in the antioxidative pathways and photosynthetic pathways were down-regulated in the NP-treated algal cells. Algal ribosome genes were especially sensitive to NP. The results indicated that NP could induce oxidative stress in algal cells and that Dictyosphaerium sp. showed potential as a bioremediation agent.


Assuntos
Clorófitas/fisiologia , Fenóis/toxicidade , Poluentes Químicos da Água/toxicidade , Biodegradação Ambiental , Fotossíntese , Transcriptoma
11.
Sci Total Environ ; 686: 246-253, 2019 Oct 10.
Artigo em Inglês | MEDLINE | ID: mdl-31181512

RESUMO

Nanoparticles (NPs) often serve as carriers of background toxins and enhance their toxicity on aquatic organisms such as Ceriodaphnia dubia (C. dubia). However, foods, especially algae, are also present in natural water and impacts this type of toxicity. This study investigated the effect of algae on the combined toxicity of nano-TiO2 and lead (Pb). A mixture of yeast-trout chow-cereal leaves (YTC) was also used as another model food. Results indicated that, both algae and YTC significantly reduce the combined toxicity of nano-TiO2 and Pb. Further investigation indicated that the ingestion of algae had minimal impacts on Pb uptake by, Pb depuration from, and Pb distribution within the C. dubia. Therefore, the toxicity reduction from algae ingestion should come from mechanisms other than the change in Pb mass and speciation in C. dubia, which will need future investigation. Nevertheless, the effect of food on the mitigation of combined toxicity of NPs and heavy metals must be considered when assessing the toxicity of nanoparticles in the natural environment because food always exists in natural waterbodies where aquatic organisms grow.


Assuntos
Clorófitas/fisiologia , Cladóceros/fisiologia , Chumbo/toxicidade , Titânio/toxicidade , Animais , Nanopartículas/toxicidade , Testes de Toxicidade , Poluentes Químicos da Água/toxicidade
12.
Extremophiles ; 23(4): 367-376, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31119431

RESUMO

Continental hydrothermal systems are a dynamic component of global thermal and geochemical cycles, exerting a pronounced impact on water chemistry and heat storage. As such, these environments are commonly classified by temperature, thermal fluid ionic concentration, and pH. Terrestrial hydrothermal systems are a refuge for extremophilic organisms, as extremes in temperature, metal concentration, and pH profoundly impact microorganism assemblage composition. While numerous studies focus on Bacteria and Archaea in these environments, few focus on Eukarya-likely due to lower temperature tolerances and because they are not model organisms for understanding the evolution of early life. However, where present, eukaryotic organisms are significant members of continental hydrothermal microorganism communities. Thus, this manuscript focuses on the eukaryotic occupants of terrestrial hydrothermal systems and provides a review of the current status of research, including microbe-eukaryote interactions and suggestions for future directions.


Assuntos
Amébidos/fisiologia , Biodiversidade , Clorófitas/fisiologia , Fungos/fisiologia , Fontes Hidrotermais , Rodófitas/fisiologia , Amébidos/isolamento & purificação , Fungos/isolamento & purificação
13.
Environ Sci Pollut Res Int ; 26(17): 17845-17852, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-31041713

RESUMO

Worldwide, reef building corals are being degraded due to increasing anthropogenic pressure, and as a result, macroalgal cover is being increased. Hence, mechanism of coral-algal interaction, differential coral response to algal overgrowth, is critical from every geographical location to predict future coral dynamics. This paper documents the frequency of coral-algal (Halimeda) interactions, differential coral response to algal interaction. We found difference in susceptibility among coral genera to competitive effects. Out of 970 coral colonies surveyed, 36.7% were in contact with Halimeda sp. Most frequent contact was observed in Porites (57%) followed by Favites 28% (n = 60), Acropora 26% (n = 48), Platygyra 5% (n = 5) and Symphyllia 4.2% (n = 3). Frequent discoloration and tissue loss were only observed in Porites. Continuous monitoring revealed that long-term algal physical contact prevents light required for polyp for photosynthesis and stops coral feeding ability. In this study, we also found mutual exclusion between Halimeda and coral recruit. Out of 180 coral colonies (size class between 5 and 15 cm) comprised of Favites (n = 74), Acropora (n = 20), Favia (n = 79) and Porites (n = 7) surveyed, none of them were found in Halimeda-dominated sites. The documented effects of recruitment exclusion and tissue mortality followed by algal interaction on major reef building corals (Porites) could affect replenishing process and health of the remaining healthy corals in the Palk Bay reef if algal proliferation rate is not controlled through proper management strategies.


Assuntos
Antozoários/fisiologia , Clorófitas/fisiologia , Recifes de Corais , Animais , Antozoários/microbiologia , Índia
14.
ISME J ; 13(8): 2058-2067, 2019 08.
Artigo em Inglês | MEDLINE | ID: mdl-31015561

RESUMO

Understanding factors affecting the susceptibility of organisms to thermal stress is of enormous interest in light of our rapidly changing climate. When adaptation is limited, thermal acclimation and deacclimation abilities of organisms are critical for population persistence through a period of thermal stress. Holobionts (hosts plus associated symbionts) are key components of various ecosystems, such as coral reefs, yet the contributions of their two partners to holobiont thermal plasticity are poorly understood. Here, we tested thermal plasticity of the freshwater cnidarian Hydra viridissima (green hydra) using individual behavior and population responses. We found that algal presence initially reduced hydra thermal tolerance. Hydra with algae (symbiotic hydra) had comparable acclimation rates, deacclimation rates, and thermal tolerance after acclimation to those without algae (aposymbiotic hydra) but they had higher acclimation capacity. Acclimation of the host (hydra) and/or symbiont (algae) to elevated temperatures increased holobiont thermal tolerance and these effects persisted for multiple asexual generations. In addition, acclimated algae presence enhanced hydra fitness under prolonged sublethal thermal stress, especially when food was limited. Our study indicates while less intense but sublethal stress may favor symbiotic organisms by allowing them to acclimate, sudden large, potentially lethal fluctuations in climate stress likely favor aposymbiotic organisms. It also suggests that thermally stressed colonies of holobionts could disperse acclimated hosts and/or symbionts to other colonies, thereby reducing their vulnerability to climate change.


Assuntos
Aclimatação , Clorófitas/fisiologia , Cnidários/fisiologia , Hydra/fisiologia , Simbiose , Animais , Recifes de Corais , Ecossistema , Alimentos , Água Doce , Temperatura Alta , Estresse Fisiológico
15.
Environ Pollut ; 250: 186-195, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-30995572

RESUMO

The ultra-high Cd polluted environment is a special habitat in nature. Analysis of the biological adaptation and resistance mechanism of Auxenochlorella protothecoides UTEX234 to ultra-high Cd stress would offer some inspiring understanding on Cd detoxification mechanism and help discovering highly active bioremediation agents. In this study, integrated analyses of the transcriptome, multi-physiological and biochemical data and fatty acid profilings of UTEX2341 were performed for the first time. It was found that exogenous Ca ions could alleviate Cd stress. Manganese-dependent superoxide dismutase and peroxidase also participated in intracellular detoxification. And non-enzymatic antioxidants rather than one specific enzymatic antioxidant were suggested to be used as "core antioxidants", which witnessed better performance in Cd detoxification. In addition, Cd stress improved sixteen alkane value and biofuel yield and quality.


Assuntos
Cádmio/metabolismo , Clorófitas/fisiologia , Poluentes Ambientais/metabolismo , Lipídeos/biossíntese , Microalgas/fisiologia , Adaptação Fisiológica , Antioxidantes/metabolismo , Biodegradação Ambiental , Biocombustíveis , Cádmio/toxicidade , Clorófitas/genética , Clorófitas/metabolismo , Poluentes Ambientais/toxicidade , Microalgas/genética , Microalgas/metabolismo , Transcriptoma
16.
Artigo em Inglês | MEDLINE | ID: mdl-30987041

RESUMO

In order to study the effects of nitrogen stress on the lipid synthesis of Parachlorella kessleri TY02 and to understand the changes in growth, photosynthetic pigments, total protein and total carbohydrate contents during lipid accumulation, the cells of the strain were cultured in nitrogen-deficient (N-) and nitrogen-rich (N⁺) media for one week. Changes in cell growth, chlorophyll content, chlorophyll fluorescence parameters, neutral lipid and total lipid content, total protein content and total carbohydrate content were measured and analyzed. The results showed that, under nitrogen stress, the algal strain grew slowly, and chlorophyll and total protein contents decreased, while total carbohydrate and total lipid contents increased. This indicated that, under nitrogen stress, most of the carbon flowed to the synthesis of lipids and carbohydrates. Meanwhile, reducing the nitrogen content was a relatively economical and easy to operate method of promoting lipid accumulation.


Assuntos
Clorófitas/fisiologia , Metabolismo dos Lipídeos , Estresse Fisiológico , Carboidratos/análise , Carbono/metabolismo , Clorofila/metabolismo , Clorófitas/crescimento & desenvolvimento , Clorófitas/metabolismo , Nitrogênio/metabolismo , Fotossíntese , Proteínas de Plantas/metabolismo
17.
Environ Sci Pollut Res Int ; 26(13): 13346-13353, 2019 May.
Artigo em Inglês | MEDLINE | ID: mdl-30903473

RESUMO

Intertidal macroalgae suffer different environmental conditions and mat densities during growing period. In the present study, Ulva lactuca Linnaeus were collected from high, intermediate, and low tidal zones at Nan'ao Island, China. These algal photosynthetic pigments and photosynthesis behaviors with different mat densities were measured. The aim is to examine how the physiological responses and acclimation match the representative tidal distribution and algal mat density. The photosynthetic pigment (chlorophyll a and carotenoid) contents and irradiance-saturated maximum photosynthetic rates (Pmax) were greater in low zone-grown U. lactuca compared with the algae grown at high and intermediate zones. Under low algal mat density, the Pmax, apparent photosynthetic efficiency (α), and dark respiration rate (Rd) of U. lactuca grown at low zone were increased, whereas the irradiance saturation points (Ik) were decreased, compared with the algae grown at higher zone. However, the Pmax of high and intermediate zone-grown U. lactuca at high algal mat density were greater than at low density. Moreover, the pH compensation point of low zone-grown thalli (9.98) was lower than the higher zone-grown thalli (more than 10.15); however, the chlorophyll fluorescence parameters (reflect photosynthetic system activity) of the thalli collected from the three different zones were similar. Therefore, we proposed that the effects of varied densities on the photosynthetic rates of these three tidal zone-grown U. lactuca thalli were different, which might be related with different capacity of HCO3- utilization of macroalgae at their zonations.


Assuntos
Clorofila A/química , Clorófitas/química , Fotossíntese/fisiologia , Ulva/química , Aclimatação , Carotenoides , China , Clorófitas/fisiologia , Ilhas , Alga Marinha
18.
Genes (Basel) ; 10(2)2019 02 19.
Artigo em Inglês | MEDLINE | ID: mdl-30791470

RESUMO

Circadian clocks in eukaryotes involve both transcriptional-translational feedback loops, post-translational regulation, and metabolic, non-transcriptional oscillations. We recently identified the involvement of circadian oscillations in the intracellular concentrations of magnesium ions (Mg2+i) that were conserved in three eukaryotic kingdoms. Mg2+i in turn contributes to transcriptional clock properties of period and amplitude, and can function as a zeitgeber to define phase. However, the mechanism-or mechanisms-responsible for the generation of Mg2+i oscillations, and whether these are functionally conserved across taxonomic groups, remain elusive. We employed the cellular clock model Ostreococcus tauri to provide a first study of an MgtE domain-containing protein in the green lineage. OtMgtE shares homology with the mammalian SLC41A1 magnesium/sodium antiporter, which has previously been implicated in maintaining clock period. Using genetic overexpression, we found that OtMgtE contributes to both timekeeping and daily changes in Mg2+i. However, pharmacological experiments and protein sequence analyses indicated that critical differences exist between OtMgtE and either the ancestral MgtE channel or the mammalian SLC41 antiporters. We concluded that even though MgtE domain-containing proteins are only distantly related, these proteins retain a shared role in contributing to cellular timekeeping and the regulation of Mg2+i.


Assuntos
Antiporters/genética , Proteínas de Bactérias/genética , Proteínas de Transporte de Cátions/genética , Clorófitas/genética , Ritmo Circadiano , Magnésio/metabolismo , Proteínas de Plantas/genética , Clorófitas/fisiologia , Proteínas de Plantas/metabolismo
19.
Photosynth Res ; 140(1): 65-76, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-30635858

RESUMO

Marine phytoplankton experience a wide range of nutrient and light conditions in nature and respond to these conditions through changes in growth rate, chlorophyll concentration, and other physiological properties. Chlorophyll fluorescence is a non-invasive and efficient tool for characterizing changes in these physiological properties. In particular, the introduction of fast repetition rate fluorometry (FRRf) into studies of phytoplankton physiology has enabled detailed studies of photosynthetic components and kinetics. One property retrieved with an FRRf is the 'single-turnover' maximum fluorescence (FmST) when the primary electron acceptor, Qa, is reduced but the plastoquinone (PQ) pool is oxidized. A second retrieved property is the 'multiple-turnover' fluorescence (FMT) when both Qa and PQ are reduced. Here, variations in FmST and FMT were measured in the green alga Dunaliella tertiolecta grown under nitrate-limited, light-limited, and replete conditions. The ratio of FmST to FMT (ST/MT) showed a consistent relationship with cellular chlorophyll in D. tertiolecta across all growth conditions. However, the ST/MT ratio decreased with growth rate under nitrate-limited conditions but increased with growth rate under light-limited conditions. In addition, cells from light-limited conditions showed a high accumulation of Qb-nonreducing centers, while cells from nitrate-limited conditions showed little to none. We propose that these findings reflect differences in the reduction and oxidation rates of plastoquinone due to the unique impacts of light and nitrate limitation on the stoichiometry of light-harvesting components and downstream electron acceptors.


Assuntos
Clorófitas/fisiologia , Plastoquinona/metabolismo , Aclimatação , Clorofila/metabolismo , Clorófitas/crescimento & desenvolvimento , Clorófitas/efeitos da radiação , Transporte de Elétrons , Fluorescência , Fluorometria , Cinética , Oxirredução , Fotossíntese , Fitoplâncton
20.
Plant Cell Physiol ; 60(6): 1205-1223, 2019 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-30668793

RESUMO

Lobosphaera incisa is a green microalga that accumulates high levels of the valuable omega-6 long-chain polyunsaturated fatty acids (LC-PUFA) arachidonic acid (ARA, 20:4n-6) in triacylglycerols (TAG) under nitrogen (N) starvation. LC-PUFA accumulation is a rare trait in photosynthetic microalgae with insufficiently understood physiological significance. In this study, RNAi was attempted, for the first time in L. incisa, to produce knockdown lines for the Δ5 desaturase gene. Two lines, termed modified lines, which were isolated during screening for transgenic events, demonstrated alterations in their LC-PUFA profile, ARA-biosynthesis gene expression and lipid class distribution. In line M5-78, which appeared to carry a mutation in the Δ6 elongase gene, LC-PUFA were substituted by 18:3n-6 in all glycerolipids. Line M2-35, for which the exact genetic background has not been established, displayed a dramatic reduction in 20:4n-6, concomitant with an augmented proportion of 18:1n-9, in particular in the extraplastidial membrane lipids and TAG. The physiological responses of the modified lines to stressful conditions were compared with the wild type and the Δ5 desaturase mutant. In the N-replete cells of modified lines, the frequency of lipid droplets was reduced, while a number of starch grains increased, suggesting altered partitioning of assimilated carbon into reserve products. Furthermore, both lines exhibited reduced ability to accumulate TAG under N deprivation and recover from N starvation. Both lines demonstrated lower photosynthetic pigment contents, impairments in photosynthesis under a range of stressful conditions, and less efficient functioning of photoprotection under optimal conditions. Possible implications of fatty acids modifications in the stress response of L. incisa are addressed.


Assuntos
Clorófitas/fisiologia , Ácidos Graxos Insaturados/fisiologia , Ácido Araquidônico/metabolismo , Clorófitas/metabolismo , Clorófitas/ultraestrutura , Cloroplastos/metabolismo , Cloroplastos/ultraestrutura , Ácidos Graxos Ômega-6/metabolismo , Ácidos Graxos Ômega-6/fisiologia , Ácidos Graxos Insaturados/metabolismo , Regulação da Expressão Gênica de Plantas , Microscopia Eletrônica de Transmissão , Nitrogênio/deficiência , Fotossíntese , Estresse Fisiológico
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