Confocal microscopy of thylakoid autofluorescence in relation to origin of grana and phylogeny in the green algae

1999 ◽  
Vol 26 (7) ◽  
pp. 695 ◽  
Author(s):  
B. E. S. Gunning ◽  
O. M. Schwartz
Keyword(s):  
Electron Microscopy ◽  
Chlorophyll Fluorescence ◽  
Confocal Microscopy ◽  
Green Algae ◽  
Higher Plants ◽  
Higher Plant ◽  
Thylakoid Stacking ◽  
Uniform Background ◽  
High Concentrations ◽  
Thylakoid Appression

Confocal microscopy was used to examine heterogeneity of chlorophyll fluorescence in chloroplasts of selected green algae, in the light of evidence that the technique reveals the distribution of photosystem II (PSII). Three levels of complexity were seen: (1) uniform fluorescence (Codium) or intergrading zones of bright and less bright fluorescence in genera known from electron microscopy to have irregular areas of thylakoid appression (e.g. Chlamydomonas — in which Bertos and Gibbs (J. Phycol., 34, 1009, 1998) have found absence of segregation of photosystem I (PSI) and PSII, Ulothrix, Stigeoclonium, Draparnaldia); (2) a pattern of 1–2 µm patches of fluorescence on a less bright uniform background, in taxa where more organized thylakoid stacking (but not grana sensu higher plants) is seen by electron microscopy (Ulva, Oedogonium); and (3) Discrete 0.5–2 µm spots of fluorescence in a relatively fluorescence-free background, closely resembling higher plant grana (Cladophorophyceae, Zygnematales, Coleochaete, Nitella). Further investigation of these states may illuminate the evolution of higher plant thylakoid systems, where PSII is segregated into grana, and may provide clues concerning the adaptive advantages of grana. Association of putative PSII fluorescence with pyrenoids was found in most taxa, although fluorescence of trans-pyrenoid thylakoids was seen in one case only. The association prevails whether or not there is a starch sheath around the pyrenoids, and is persistent in pyrenoids isolated from Spirogyra. We speculate that this fluorescence may represent a subset of PSII that functions with thylakoid carbonic anhydrase to provide locally high concentrations of CO2 to the Rubisco in the pyrenoid core, as predicted by Raven (Plant, Cell and Environment, 20, 147, 1997).

scholarly journals Midpoint redox potentials of plant and algal ferredoxins

1977 ◽  
Vol 168 (2) ◽  
pp. 205-209 ◽  
Author(s):  
R Cammack ◽  
K K Rao ◽  
C P Bargeron ◽  
K G Hutson ◽  
P W Andrew ◽  
...  
Keyword(s):  
Green Algae ◽  
Higher Plants ◽  
Electron Paramagnetic Resonance Spectroscopy ◽  
Photosynthetic Electron Transport ◽  
Resonance Spectroscopy ◽  
Redox Potentials ◽  
Higher Plant ◽  
Paramagnetic Resonance ◽  
Blue Green Algae ◽  
Nostoc Strain

Midpoint potentials of plant-type ferredoxins from a range of sources were measured by redox titrations combined with electron-paramagnetic-resonance spectroscopy. For ferredoxins from higher plants, green algae and most red algae, the midpoint potentials (at pH 8.0) were between —390 and —425 mV. Values for the major ferredoxin fractions from blue-green algae were less negative (between —325 and —390 mV). In addition, Spirulina maxima and Nostoc strain MAC contain second minor ferredoxin components with a different potential, —305 mV (the highest so far measured for a plant-algal ferrodoxin) for Spirulina ferrodoxin II, and —455 mV (the lowest so far measured for a plant-algal ferredoxin) for Nostoc strain MAC ferredoxin II. However, two ferredoxins extracted from a variety of the higher plant Pisum sativum (pea) had midpoint potentials that were only slightly different from each other. These values are discussed in terms of possible roles for the ferredoxins in addition to their involvement in photosynthetic electron transport.

scholarly journals Purification and characterization of high- and low-molecular-mass isoforms of phosphoenolpyruvate carboxylase from Chlamydomonas reinhardtii

1998 ◽  
Vol 331 (1) ◽  
pp. 201-209 ◽  
Author(s):  
Jean RIVOAL ◽  
William C. PLAXTON ◽  
David H. TURPIN
Keyword(s):  
Green Algae ◽  
Phosphoenolpyruvate Carboxylase ◽  
Higher Plants ◽  
Current Model ◽  
Catalytic Subunit ◽  
Dihydroxyacetone Phosphate ◽  
Evolutionary Divergence ◽  
Banana Fruit ◽  
Higher Plant ◽  
Green Algal

Phosphoenolpyruvate carboxylase (PEPC) is a key enzyme in the supply of carbon skeletons for the assimilation of nitrogen by green algae. Two PEPC isoforms with respective native molecular masses of 400 (PEPC1) and 650 (PEPC2) kDa have been purified from Chlamydomonas reinhardtiiCW-15 cc1883 (Chlorophyceae). SDS/PAGE, immunoblot and CNBr peptide-mapping analyses indicate the presence of the same 100 kDa PEPC catalytic subunit in both isoforms. PEPC1 is a homotetramer, whereas PEPC2 seems to be a complex between the PEPC catalytic subunit and other immunologically unrelated polypeptides of 50–70 kDa. Kinetic analyses indicate that these PEPC isoforms are (1) differentially regulated by pH, (2) activated by glutamine and dihydroxyacetone phosphate and (3) inhibited by glutamate, aspartate, 2-oxoglutarate and malate. These results are consistent with the current model for the regulation of anaplerotic carbon fixation in green algae, and demonstrate that green algal PEPCs are uniquely regulated by glutamine. Several techniques were used to assess the structural relationships between C. reinhardtiiPEPC and the higher plant or prokaryotic enzyme. Immunoblot studies using anti-(green algal or higher plant PEPC) IgGs suggested that green algal (C. reinhardtii, Selenastrum minutum), higher plant (maize, banana fruit, tobacco) and prokaryotic (Synechococcus leopoliensis, Escherichia coli)PEPCs have little or no immunological relatedness. Moreover, the N-terminal amino acid sequence of the C. reinhardtiiPEPC subunit did not have significant similarity to the highly conserved corresponding region in enzymes from higher plants, and CNBr cleavage patterns of green algal PEPCs were distinct from those of higher plant and cyanobacterial PEPCs. These results point to significant evolutionary divergence between green algal, higher plant and prokaryotic PEPCs.

A Scanning Electron Microscopic Study of Pro-Vascular Cellular Morphology in Chaetophora Incressata

1985 ◽  
Vol 43 ◽  
pp. 638-639
Author(s):  
A. E. Hotchkiss ◽  
A. T. Hotchkiss ◽  
R. P. Apkarian
Keyword(s):  
Green Algae ◽  
Vascular Plants ◽  
Vascular System ◽  
Higher Plants ◽  
Wall Structure ◽  
Electron Microscopic ◽  
Physiological Processes ◽  
Scanning Electron Microscopic Study ◽  
Scanning Electron Microscopic ◽  
Scanning Electron

Multicellular green algae may be an ancestral form of the vascular plants. These algae exhibit cell wall structure, chlorophyll pigmentation, and physiological processes similar to those of higher plants. The presence of a vascular system which provides water, minerals, and nutrients to remote tissues in higher plants was believed unnecessary for the algae. Among the green algae, the Chaetophorales are complex highly branched forms that might require some means of nutrient transport. The Chaetophorales do possess apical meristematic groups of cells that have growth orientations suggestive of stem and root positions. Branches of Chaetophora incressata were examined by the scanning electron microscope (SEM) for ultrastructural evidence of pro-vascular transport.

scholarly journals Effect of Exogenously Applied 24-Epibrassinolide and Brassinazole on Xylogenesis and Microdistribution of Cell Wall Polymers in Leucaena leucocephala (Lam) De Wit

2021 ◽  
Author(s):  
S. Pramod ◽  
M. Anju ◽  
H. Rajesh ◽  
A. Thulaseedharan ◽  
Karumanchi S. Rao
Keyword(s):  
Electron Microscopy ◽  
Cell Wall ◽  
Leucaena Leucocephala ◽  
Higher Plants ◽  
Lignin Content ◽  
Wood Quality ◽  
Wall Structure ◽  
Vessel Element ◽  
Xylem Differentiation ◽  
Cell Wall Polymers

AbstractPlant growth regulators play a key role in cell wall structure and chemistry of woody plants. Understanding of these regulatory signals is important in advanced research on wood quality improvement in trees. The present study is aimed to investigate the influence of exogenous application of 24-epibrassinolide (EBR) and brassinosteroid inhibitor, brassinazole (BRZ) on wood formation and spatial distribution of cell wall polymers in the xylem tissue of Leucaena leucocephala using light and immuno electron microscopy methods. Brassinazole caused a decrease in cambial activity, xylem differentiation, length and width of fibres, vessel element width and radial extent of xylem suggesting brassinosteroid inhibition has a concomitant impact on cell elongation, expansion and secondary wall deposition. Histochemical studies of 24-epibrassinolide treated plants showed an increase in syringyl lignin content in the xylem cell walls. Fluorescence microscopy and transmission electron microscopy studies revealed the inhomogenous pattern of lignin distribution in the cell corners and middle lamellae region of BRZ treated plants. Immunolocalization studies using LM10 and LM 11 antibodies have shown a drastic change in the micro-distribution pattern of less substituted and highly substituted xylans in the xylem fibres of plants treated with EBR and BRZ. In conclusion, present study demonstrates an important role of brassinosteroid in plant development through regulating xylogenesis and cell wall chemistry in higher plants.

scholarly journals Odontoblast processes in dentin revealed by fluorescent Di-I.

1995 ◽  
Vol 43 (2) ◽  
pp. 159-168 ◽  
Author(s):  
M R Byers ◽  
A Sugaya
Keyword(s):  
Electron Microscopy ◽  
Confocal Microscopy ◽  
Cell Structure ◽  
Carbocyanine Dyes ◽  
Carbocyanine Dye ◽  
Reparative Dentin ◽  
Hard Tissues ◽  
Odontoblast Process ◽  
Odontoblast Processes ◽  
Rat Molars

There has been controversy about the length and structure of the odontoblast process within dentin since the earliest histologic studies of teeth. Our objective was to use the fluorescent carbocyanine dye Di-I combined with a new gelatin embedment procedure and confocal microscopy to determine the structure and extent of odontoblast processes in developing and mature rat teeth, injured rat molars, reparative dentin, and adult monkey teeth. We found that odontoblast processes do not extend into outer dentin or to the dentin-enamel junction except during early stages of development. Those in innervated regions of crown are long and straight, whereas those in roots are extensively branched and shorter. Cavity injury to crown dentin caused odontoblast fragments to be aspirated into outer dentin. In reparative dentin the odontoblast processes were branched and similar to those in roots. We used photoconversion and electron microscopy to show that Di-I fills the entire odontoblast after gelatin embedment, including the cytoplasm. This is a different type of carbocyanine staining from any previously reported, and it also stains other cells in adjacent hard tissues such as bone and cementum. The Di-I-gelatin method is a new way to use carbocyanine dyes. It has enabled us to solve a long-standing controversy about the histology of teeth, and it should be useful for many other studies of cell structure.

Morphology and behaviour of dinoflagellate chromosomes during the cell cycle and mitosis

2000 ◽  
Vol 113 (7) ◽  
pp. 1231-1239 ◽  
Author(s):  
Y. Bhaud ◽  
D. Guillebault ◽  
J. Lennon ◽  
H. Defacque ◽  
M.O. Soyer-Gobillard ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Cell Cycle ◽  
Confocal Microscopy ◽  
Nuclear Envelope ◽  
Chromosome Segregation ◽  
Morphological Changes ◽  
S Phase ◽  
Chromosome Behaviour ◽  
Double Number ◽  
Do So

The morphology and behaviour of the chromosomes of dinoflagellates during the cell cycle appear to be unique among eukaryotes. We used synchronized and aphidicolin-blocked cultures of the dinoflagellate Crypthecodinium cohnii to describe the successive morphological changes that chromosomes undergo during the cell cycle. The chromosomes in early G(1) phase appeared to be loosely condensed with numerous structures protruding toward the nucleoplasm. They condensed in late G(1), before unwinding in S phase. The chromosomes in cells in G(2) phase were tightly condensed and had a double number of arches, as visualised by electron microscopy. During prophase, chromosomes elongated and split longitudinally, into characteristic V or Y shapes. We also used confocal microscopy to show a metaphase-like alignment of the chromosomes, which has never been described in dinoflagellates. The metaphase-like nucleus appeared flattened and enlarged, and continued to do so into anaphase. Chromosome segregation occurred via binding to the nuclear envelope surrounding the cytoplasmic channels and microtubule bundles. Our findings are summarized in a model of chromosome behaviour during the cell cycle.

Lack of Cross-Resistance of Paraquat-Resistant Hairy Fleabane (Conyza bonariensis) to Other Toxic Oxygen Generators Indicates Enzymatic Protection is Not the Resistance Mechanism

Weed Science ◽  
1989 ◽  
Vol 37 (1) ◽  
pp. 5-11 ◽  
Author(s):  
Kevin C. Vaughn ◽  
Martin A. Vaughan ◽  
Patrick Camilleri
Keyword(s):  
Electron Microscopy ◽  
Chlorophyll Fluorescence ◽  
Resistance Mechanism ◽  
Cross Resistance ◽  
Oxygen Generator ◽  
Conyza Bonariensis ◽  
Singlet Oxygen Generator ◽  
Chlorophyll Bleaching ◽  
Direct Measures ◽  
Hairy Fleabane

Cross-resistance of the paraquat-resistant (R) hairy fleabane to other compounds that accept electrons from photosystem I (PSI) or produce toxic oxygen species was determined by chlorophyll loss, electron microscopy, and chlorophyll fluorescence suppression. Although the R bioype is approximately 100 x more resistant to paraquat than the susceptible (S) biotype based upon the assays for tissue damage, little or no cross-resistance was observed to a number of other PSI electron acceptors, including the bipyridilium herbicide morfamquat. A low level of resistance (approximately 10-fold) was noted to diquat and the singlet oxygen generator rose bengal. As measured by chlorophyll fluorescence suppression, the R biotype was about 100-fold resistant to paraquat, but only 10-fold resistant to diquat, and exhibited no resistance to morfamquat. Because differences observed with this protocol are direct measures of the ability of the herbicide to reach the active site and the results correlate with the level of resistance observed by chlorophyll bleaching or electron microscopy, these data suggest that compartmentalization is the major factor in paraquat resistance in hairy fleabane.

Measurement of ferrochelatase activity using a novel assay suggests that plastids are the major site of haem biosynthesis in both photosynthetic and non-photosynthetic cells of pea (Pisum sativum L.)

2002 ◽  
Vol 362 (2) ◽  
pp. 423-432 ◽  
Author(s):  
Johanna E. CORNAH ◽  
Jennifer M. ROPER ◽  
Davinder Pal SINGH ◽  
Alison G. SMITH
Keyword(s):  
Ferrous Iron ◽  
Specific Activity ◽  
Higher Plants ◽  
Protoporphyrin Ix ◽  
Chlorophyll Synthesis ◽  
Marker Enzyme ◽  
Hexane Extraction ◽  
Higher Plant ◽  
Major Site ◽  
Haem Biosynthesis

Ferrochelatase is the terminal enzyme of haem biosynthesis, catalysing the insertion of ferrous iron into the macrocycle of protoporphyrin IX, the last common intermediate of haem and chlorophyll synthesis. Its activity has been reported in both plastids and mitochondria of higher plants, but the relative amounts of the enzyme in the two organelles are unknown. Ferrochelatase is difficult to assay since ferrous iron requires strict anaerobic conditions to prevent oxidation, and in photosynthetic tissues chlorophyll interferes with the quantification of the product. Accordingly, we developed a sensitive fluorimetric assay for ferrochelatase that employs Co2+ and deuteroporphyrin in place of the natural substrates, and measures the decrease in deuteroporphyrin fluorescence. A hexane-extraction step to remove chlorophyll is included for green tissue. The assay is linear over a range of chloroplast protein concentrations, with an average specific activity of 0.68nmol·min−1·mg of protein−1, the highest yet reported. The corresponding value for mitochondria is 0.19nmol·min−1·mg of protein−1. The enzyme is inhibited by N-methylprotoporphyrin, with an estimated IC50 value of ≈ 1nM. Using this assay we have quantified ferrochelatase activity in plastids and mitochondria from green pea leaves, etiolated pea leaves and pea roots to determine the relative amounts in the two organelles. We found that, in all three tissues, greater than 90% of the activity was associated with plastids, but ferrochelatase was reproducibly detected in mitochondria, at levels greater than the contaminating plastid marker enzyme, and was latent. Our results indicate that plastids are the major site of haem biosynthesis in higher plant cells, but that mitochondria also have the capacity for haem production.

scholarly journals Multiwalled carbon nanotubes in alfalfa and wheat: toxicology and uptake

2012 ◽  
Vol 9 (77) ◽  
pp. 3514-3527 ◽  
Author(s):  
Pola Miralles ◽  
Errin Johnson ◽  
Tamara L. Church ◽  
Andrew T. Harris
Keyword(s):  
Electron Microscopy ◽  
Carbon Nanotubes ◽  
Root Elongation ◽  
Wheat Root ◽  
Root Tip ◽  
Multiwalled Carbon ◽  
Wheat Seedlings ◽  
Industrial Grade ◽  
High Concentrations ◽  
Multiwalled Cnts

Data on the bioavailability and toxicity of carbon nanotubes (CNTs) in the environment, and, in particular, on their interactions with vascular plants, are limited. We investigated the effects of industrial-grade multiwalled CNTs (75 wt% CNTs) and their impurities on alfalfa and wheat. Phytotoxicity assays were performed during both seed germination and seedling growth. The germinations of both species were tolerant of up to 2560 mg l −1 CNTs, and root elongation was enhanced in alfalfa and wheat seedlings exposed to CNTs. Remarkably, catalyst impurities also enhanced root elongation in alfalfa seedlings as well as wheat germination. Thus the impurities, not solely the CNTs, impacted the plants. CNT internalization by plants was investigated using electron microscopy and two-dimensional Raman mapping. The latter showed that CNTs were adsorbed onto the root surfaces of alfalfa and wheat without significant uptake or translocation. Electron microscopy investigations of internalization were inconclusive owing to poor contrast, so Fe 3 O 4 -functionalized CNTs were prepared and studied using energy-filter mapping of Fe 3 O 4 . CNTs bearing Fe 3 O 4 nanoparticles were detected in the epidermis of one wheat root tip only, suggesting that internalization was possible but unusual. Thus, alfalfa and wheat tolerated high concentrations of industrial-grade multiwalled CNTs, which adsorbed onto their roots but were rarely taken up.

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