scholarly journals Salt Stress Induces Paramylon Accumulation and Fine-Tuning of the Macro-Organization of Thylakoid Membranes in Euglena gracilis Cells

2021 ◽  
Vol 12 ◽  
Author(s):  
Sai Divya Kanna ◽  
Ildikó Domonkos ◽  
Tímea Ottília Kóbori ◽  
Ágnes Dergez ◽  
Kinga Böde ◽  
...  
Keyword(s):  
Salt Stress ◽  
Euglena Gracilis ◽  
Thylakoid Membrane ◽  
Protein Complexes ◽  
Polyacrylamide Gel Electrophoresis ◽  
Photosynthetic Apparatus ◽  
Cd Spectroscopy ◽  
Fluorescence Yield ◽  
Fine Tuning ◽  
Salt Stress Condition

The effects of salt stress condition on the growth, morphology, photosynthetic performance, and paramylon content were examined in the mixotrophic, unicellular, flagellate Euglena gracilis. We found that salt stress negatively influenced cell growth, accompanied by a decrease in chlorophyll (Chl) content. Circular dichroism (CD) spectroscopy revealed the changes in the macro-organization of pigment-protein complexes due to salt treatment, while the small-angle neutron scattering (SANS) investigations suggested a reduction in the thylakoid stacking, an effect confirmed by the transmission electron microscopy (TEM). At the same time, the analysis of the thylakoid membrane complexes using native-polyacrylamide gel electrophoresis (PAGE) revealed no significant change in the composition of supercomplexes of the photosynthetic apparatus. Salt stress did not substantially affect the photosynthetic activity, as reflected by the fact that Chl fluorescence yield, electron transport rate (ETR), and energy transfer between the photosystems did not change considerably in the salt-grown cells. We have observed notable increases in the carotenoid-to-Chl ratio and the accumulation of paramylon in the salt-treated cells. We propose that the accumulation of storage polysaccharides and changes in the pigment composition and thylakoid membrane organization help the adaptation of E. gracilis cells to salt stress and contribute to the maintenance of cellular processes under stress conditions.

scholarly journals Fast Diffusion of the Unassembled PetC1-GFP Protein in the Cyanobacterial Thylakoid Membrane

Life ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 15
Author(s):  
Radek Kaňa ◽  
Gábor Steinbach ◽  
Roman Sobotka ◽  
György Vámosi ◽  
Josef Komenda
Keyword(s):  
Membrane Proteins ◽  
Single Molecule ◽  
Protein Interactions ◽  
Thylakoid Membrane ◽  
Protein Complexes ◽  
Correlation Spectroscopy ◽  
Membrane Microdomains ◽  
Fast Diffusion ◽  
Light Harvesting Complexes ◽  
Term Survival

Biological membranes were originally described as a fluid mosaic with uniform distribution of proteins and lipids. Later, heterogeneous membrane areas were found in many membrane systems including cyanobacterial thylakoids. In fact, cyanobacterial pigment–protein complexes (photosystems, phycobilisomes) form a heterogeneous mosaic of thylakoid membrane microdomains (MDs) restricting protein mobility. The trafficking of membrane proteins is one of the key factors for long-term survival under stress conditions, for instance during exposure to photoinhibitory light conditions. However, the mobility of unbound ‘free’ proteins in thylakoid membrane is poorly characterized. In this work, we assessed the maximal diffusional ability of a small, unbound thylakoid membrane protein by semi-single molecule FCS (fluorescence correlation spectroscopy) method in the cyanobacterium Synechocystis sp. PCC6803. We utilized a GFP-tagged variant of the cytochrome b6f subunit PetC1 (PetC1-GFP), which was not assembled in the b6f complex due to the presence of the tag. Subsequent FCS measurements have identified a very fast diffusion of the PetC1-GFP protein in the thylakoid membrane (D = 0.14 − 2.95 µm2s−1). This means that the mobility of PetC1-GFP was comparable with that of free lipids and was 50–500 times higher in comparison to the mobility of proteins (e.g., IsiA, LHCII—light-harvesting complexes of PSII) naturally associated with larger thylakoid membrane complexes like photosystems. Our results thus demonstrate the ability of free thylakoid-membrane proteins to move very fast, revealing the crucial role of protein–protein interactions in the mobility restrictions for large thylakoid protein complexes.

scholarly journals Environmental effects on photosynthetic capacity of bean genotypes

2004 ◽  
Vol 39 (7) ◽  
pp. 615-623 ◽  
Author(s):  
Rafael Vasconcelos Ribeiro ◽  
Mauro Guida dos Santos ◽  
Gustavo Maia Souza ◽  
Eduardo Caruso Machado ◽  
Ricardo Ferraz de Oliveira ◽  
...  
Keyword(s):  
High Temperature ◽  
Natural Condition ◽  
Temperature Effects ◽  
Environmental Changes ◽  
Photosynthetic Capacity ◽  
Photosynthetic Apparatus ◽  
Co2 Assimilation ◽  
Fluorescence Yield ◽  
Environmental Condition ◽  
Response Curves

Photosynthetic responses to daily environmental changes were studied in bean (Phaseolus vulgaris L.) genotypes 'Carioca', 'Ouro Negro', and Guarumbé. Light response curves of CO2 assimilation and stomatal conductance (g s) were also evaluated under controlled (optimum) environmental condition. Under this condition, CO2 assimilation of 'Carioca' was not saturated at 2,000 µmol m-2 s-1, whereas Guarumbé and 'Ouro Negro' exhibited different levels of light saturation. All genotypes showed dynamic photoinhibition and reversible increase in the minimum chlorophyll fluorescence yield under natural condition, as well as lower photosynthetic capacity when compared with optimum environmental condition. Since differences in g s were not observed between natural and controlled conditions for Guarumbé and 'Ouro Negro', the lower photosynthetic capacity of these genotypes under natural condition seems to be caused by high temperature effects on biochemical reactions, as suggested by increased alternative electron sinks. The highest g s values of 'Carioca' were observed at controlled condition, providing evidences that reduction of photosynthetic capacity at natural condition was due to low g s in addition to the high temperature effects on the photosynthetic apparatus. 'Carioca' exhibited the highest photosynthetic rates under optimum environmental condition, and was more affected by daily changes of air temperature and leaf-to-air vapor pressure difference.

A Functional Alternative Oxidase Modulates Plant Salt Tolerance in Physcomitrella patens

2019 ◽  
Vol 60 (8) ◽  
pp. 1829-1841 ◽  
Author(s):  
Guochun Wu ◽  
Sha Li ◽  
Xiaochuan Li ◽  
Yunhong Liu ◽  
Shuangshuang Zhao ◽  
...  
Keyword(s):  
Salt Stress ◽  
Salt Tolerance ◽  
Stress Responses ◽  
Alternative Oxidase ◽  
Physcomitrella Patens ◽  
Redox Homeostasis ◽  
Respiratory Pathway ◽  
Functional Link ◽  
Salt Stress Condition ◽  
Plant Salt Tolerance

Abstract Alternative oxidase (AOX) has been reported to be involved in mitochondrial function and redox homeostasis, thus playing an essential role in plant growth as well as stress responses. However, its biological functions in nonseed plants have not been well characterized. Here, we report that AOX participates in plant salt tolerance regulation in moss Physcomitrella patens (P. patens). AOX is highly conserved and localizes to mitochondria in P. patens. We observed that PpAOX rescued the impaired cyanide (CN)-resistant alternative (Alt) respiratory pathway in Arabidopsis thaliana (Arabidopsis) aox1a mutant. PpAOX transcription and Alt respiration were induced upon salt stress in P. patens. Using homologous recombination, we generated PpAOX-overexpressing lines (PpAOX OX). PpAOX OX plants exhibited higher Alt respiration and lower total reactive oxygen species accumulation under salt stress condition. Strikingly, we observed that PpAOX OX plants displayed decreased salt tolerance. Overexpression of PpAOX disturbed redox homeostasis in chloroplasts. Meanwhile, chloroplast structure was adversely affected in PpAOX OX plants in contrast to wild-type (WT) P. patens. We found that photosynthetic activity in PpAOX OX plants was also lower compared with that in WT. Together, our work revealed that AOX participates in plant salt tolerance in P. patens and there is a functional link between mitochondria and chloroplast under challenging conditions.

DNA topoisomerase activity associated with simian virus 40 nucleoprotein complexes

1994 ◽  
Vol 72 (5-6) ◽  
pp. 195-201 ◽  
Author(s):  
Claude Hamelin ◽  
Benoit D'Amours ◽  
Christian Page ◽  
Young Sup Chung
Keyword(s):  
Protein Complexes ◽  
Polyacrylamide Gel Electrophoresis ◽  
Simian Virus 40 ◽  
Simian Virus ◽  
Dna Topoisomerase ◽  
Infected Monkey ◽  
Before And After ◽  
Catalytically Active ◽  
Nucleoprotein Complexes ◽  
Sv40 Dna

Simian virus 40 (SV40) chromatin extracted from nuclei of infected monkey cells (CV1) was sedimented in neutral sucrose gradients, before and after digestion with bovine pancreatic RNase I-A or DNase I. DNA topoisomerase (TI) activity was found associated with RNase-resistant, DNase-sensitive SV40 nucleoprotein complexes. After polyacrylamide gel electrophoresis, a number of proteins with a molecular mass between 40 and 70 kDa were seen at the level of viral DNA peaks, some of which may represent catalytically active breakdown products of the TI enzyme. Large protein complexes were observed under the electron microscope in association with the viral chromosomes and appear to correspond to the SV40 DNA replication complex, including TI. Our results suggest that TI activity is indeed associated with the viral minichromosomes undergoing replication in vivo.Key words: deoxyribonucleoproteins, DNA topoisomerase, minichromosomes, ribonucleoproteins, simian virus 40, viral chromatin.

scholarly journals Effect of salt stress on some sweet corn (Zea mays L. var. saccharata) genotypes

2015 ◽  
Vol 67 (3) ◽  
pp. 993-1000 ◽  
Author(s):  
Lydia Shtereva ◽  
Roumiana Vassilevska-Ivanova ◽  
Tanya Karceva
Keyword(s):  
Zea Mays ◽  
Salt Stress ◽  
Zea Mays L ◽  
Sweet Corn ◽  
Growth Parameters ◽  
Dry Weight ◽  
Germination Percentage ◽  
F1 Hybrid ◽  
Salt Stress Condition ◽  
Salinity Levels

An experiment was carried out hydroponically under laboratory conditions to investigate the effect of salt stress on several physiological and biochemical parameters of three sweet corn (Zea mays L. var. saccharata) genotypes: lines 6-13, C-6 (pollen source) and their heterotic F1 hybrid ?Zaharina?. The degree of salinity tolerance among these genotypes was evaluated at three different sodium chloride (NaCl) concentrations: 0 mM, 100 mM, 125 mM and 150 mM. Seed germination, plant growth and biochemical stress determining parameters such as malondialdehyde (MDA), proline content and hydrogen peroxide (H2O2) levels were compared between seedlings of lines and hybrid. The obtained results indicated that both lines and hybrid have similar responses at different salinity levels for all examined traits. All the seedlings? growth parameters, such as germination percentage, root length, shoot length, root and shoot fresh and dry weight, decreased with increasing salinity level. MDA, proline and H2O2 increased at different saline conditions in comparison to the control. Based on the results, of the three genotypes examined, the hybrid Zaharina, followed by line C-6, was more salt-sensitive than line 6-13 in salt stress condition.

scholarly journals In Vitro Regeneration of Onion (Allium cepa L.) Genotypes under Salt Stress Condition

2021 ◽  
pp. 34-43
Author(s):  
Asfiqur Rahman Plabon ◽  
M. E. Hoque ◽  
Farhana Afrin Vabna ◽  
Fahima Khatun
Keyword(s):  
Salt Stress ◽  
Allium Cepa ◽  
Root Length ◽  
Stress Condition ◽  
In Vitro Regeneration ◽  
Shoot Length ◽  
Salinity Level ◽  
Salt Stress Condition ◽  
Allium Cepa L

Salinity is a major problem affecting crop production all over the world. Excessive soil salinity can reduce the productivity of many agricultural crops including many vegetables and spices. Onion is one of the most important spices in the Asiatic region which is now in high demand. The experiment was conducted to observe in vitro regeneration of onion (Allium cepa L.) under salt stress condition from September 2016 to July 2017. The experiment was conducted as two factorial (genotype and treatment) Completely Randomized Design (CRD) with 3 replications for each treatment. Shoot tip segments of three genotypes namely Faridpuri, Taherpuri and Pusa red (Indian) were cultured in MS (Murashige and skoog, 1962) media supplemented with 25, 50, 75 and 100 mM NaCl. The genotype Faridpuri gave maximum salt tolerance upto 100 mM salinity level with 10.60 cm shoot length and 1.94 cm root length having the highest relative shoot and root growth. Pusa red was found to be salinity sensitive genotype which showing lowest shoot length of 7.03 cm and root length of 0.96 cm at 100 mM NaCl treatment. However, Taherpuri was tolerant up to 100 mM salinity level with 8.14 cm shoot length and 1.25 cm root length. Both the highest fresh weight of root (54.77 mg) and dry weight of root (41.36 mg) was from the genotype Faridpuri with 25 mM NaCl treatment. However, a convenient in vitro regeneration protocol of onion genotypes under different salinity level has been developed and the genotype Faridpuri can be used for further investigation in field condition to evaluate its performance at various salinity levels.

Physiological Significance of Overproduced Carotenoids in Transformants of the Cyanobacterium Synechococcus PCC7942

1999 ◽  
Vol 54 (3-4) ◽  
pp. 191-198
Author(s):  
Navassard V. Karapetyan ◽  
Ute Windhövel ◽  
Alfred R. Holzwarth ◽  
Peter Böger
Keyword(s):  
Protein Complexes ◽  
Photosynthetic Apparatus ◽  
Fluorescence Emission ◽  
Fluorescence Induction ◽  
Carotenoid Content ◽  
Excitation Spectra ◽  
Fluorescence Excitation ◽  
Whole Cells ◽  
Fluorescence Excitation Spectra ◽  
Synechococcus Pcc7942

Abstract The functional location of carotenoids in the photosynthetic apparatus of -crtB and -pys transformants of the cyanobacterium Synechococcus PCC7942 was studied and compared with a control strain -pFP 1-3. These transformants overproduce carotenoids due to the insertion of an additional foreign phytoene synthase gene. A higher carotenoid content was found for -crtB and -pys transformants both in whole cells and isolated membranes; the -crtB transformant was also enriched with chlorophyll. 77-K fluorescence emission and excitation spectra of the phycobilin-free membranes were examined for a possible location of overproduced carotenoids in pigment-protein complexes in situ. A similar ratio of the amplitudes of fluorescence bands at 716 and 695 nm emitted by photosystems I and II, found for the three strains, indicates that the stoichiometry between photosystems of the transformants was not changed. Overproduced carotenoids are not located in the core antenna of photosys­ tem I, since 77-K fluorescence excitation spectra for photosystem I of isolated membranes from the studied strains do not differ in the region of carotenoid absorption. When illuminated with light of the same intensity but different quality, absorbed preferentially by either carotenoids, chlorophylls or phycobilins, respectively, oxygen evolution was found always higher in the transformants -crtB and -pys than in -pFP 1-3 control cells. Identical kinetics of fluorescence induction of all strains under carotenoid excitation did not reveal a higher activity of photosystem II in cells enriched with carotenoids. It is suggested that overproduced carotenoids of the transformants are not involved in photosynthetic light-harvesting; rather they may serve to protect the cells and its membranes against photodestruction.

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