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Les ARN ribosomiques (ARNr) mitochondriaux 55, 18S et 26S sont codes uniquement par l'ADN mitochondrial (ADNmt) chez le ble Triticum aestivum. Les fragments de restriction Sal I de l'ADNmt de ble ont ete clones dans le plasmide... more
Les ARN ribosomiques (ARNr) mitochondriaux 55, 18S et 26S sont codes uniquement par l'ADN mitochondrial (ADNmt) chez le ble Triticum aestivum. Les fragments de restriction Sal I de l'ADNmt de ble ont ete clones dans le plasmide pBR322 et le cosmide pHC79. Les plasmides hybrides contenant les genes codant pour les ARNr ont ete identifies par hybridations moleculaires avec les differents ARNr marques au 32p. L'etablissement des cartes de restriction des fragments ainsi identifies a permis de montrer que : -Les genes 5S et 18S sont proches l'un de l'autre et le gene 26S se trouve a un autre endroit du genome. -Les genes 5S et 18S se trouvent a l'interieur d'une sequence repetee, R, d'environ 4 kpb. Cette unite est bordee par 4 sequences designees u, v, w et y, avec les orientations v-R-w, v-R-y, u-R-w, et u-R-y. Nous en concluons que les genes 5S et 18S se trouvent a plusieurs endroits differents dans le genome mitochondrial du ble et suggerons que des recombinaisons reciproques intra -et/ou intermoleculaires entre de telles sequences repetees produiraient d'importants rearrangements genomiques et contribueraient ainsi a l'heterogeneite physique observee dans la plupart des ADNmt des plantes. Nous proposons deux modeles pour expliquer les interconversions "site specifique" entre de telles sequences. L'organisation du gene 26S est similaire et nous montrons que pour ce gene l'un des modeles proposes est le plus probable. La sequence nucleotidique du gene 26S et des regions adjacentes a ete determinee et comparee avec les sequences correspondantes dans les mitochondries de plantes, les chloroplastes et E. Coli. Cette analyse nous a permis de mettre en evidence trois regions variables a l'interieur du gene dont deux refleteraient des differences entre les plantes monocotyledones et dicotyledones. Les extremites 5' et 3' du gene ont ete determinees par cartographie a l'aide de la nuclease S1. Le gene 26S mitochondrial comporte 3465 nucleotides et ne possede pas d'intron. Les sequences supplementaires observees dans cet ARNr pourraient provenir d'autres endroits du genome. En outre, nous avons mis en evidence dans ce genome, l'existence de petites sequences repetees et d'une sequence chloroplastique.
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Light triggers chloroplast differentiation whereby the etioplast transforms into a photosynthesizing chloroplast and the thylakoid rapidly emerges. However, the sequence of events during chloroplast differentiation remains poorly... more
Light triggers chloroplast differentiation whereby the etioplast transforms into a photosynthesizing chloroplast and the thylakoid rapidly emerges. However, the sequence of events during chloroplast differentiation remains poorly understood. Using Serial Block Face Scanning Electron Microscopy (SBF-SEM), we generated a series of chloroplast 3D reconstructions during differentiation, revealing chloroplast number and volume and the extent of envelope and thylakoid membrane surfaces. Furthermore, we used quantitative lipid and whole proteome data to complement the (ultra)structural data, providing a time-resolved, multi-dimensional description of chloroplast differentiation. This showed two distinct phases of chloroplast biogenesis: an initial photosynthesis-enabling ‘Structure Establishment Phase’ followed by a ‘Chloroplast Proliferation Phase’ during cell expansion. Moreover, these data detail thylakoid membrane expansion during de-etiolation at the seedling level and the relative contribution and differential regulation of proteins and lipids at each developmental stage. Altogether, we establish a roadmap for chloroplast differentiation, a critical process for plant photoautotrophic growth and survival.
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This study probes the exposure route-dependent fate of silver nanoparticles by using a 3D cell model mimicking the liver. It reveals the cellular trafficking and transformation of silver species, up to their storage in vacuoles or biliary... more
This study probes the exposure route-dependent fate of silver nanoparticles by using a 3D cell model mimicking the liver. It reveals the cellular trafficking and transformation of silver species, up to their storage in vacuoles or biliary excretion.
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Summary Haberlea rhodopensis is a resurrection plant that can tolerate extreme and prolonged periods of desiccation with a rapid restoration of physiological function upon rehydration. Specialized mechanisms are required to minimize... more
Summary Haberlea rhodopensis is a resurrection plant that can tolerate extreme and prolonged periods of desiccation with a rapid restoration of physiological function upon rehydration. Specialized mechanisms are required to minimize cellular damage during desiccation and to maintain integrity for rapid recovery following rehydration. In this study we used respiratory activity measurements, electron microscopy, transcript, protein and blue native‐PAGE analysis to investigate mitochondrial activity and biogenesis in fresh, desiccated and rehydrated detached H. rhodopensis leaves. We demonstrate that unlike photosynthesis, mitochondrial respiration was almost immediately activated to levels of fresh tissue upon rehydration. The abundance of transcripts and proteins involved in mitochondrial respiration and biogenesis were at comparable levels in fresh, desiccated and rehydrated tissues. Blue native‐PAGE analysis revealed fully assembled and equally abundant OXPHOS complexes in mitochon...
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The complicated restriction patterns of plant mtDNA suggest that it is unusually large and complex and possesses a type of sequence heterogeneity not found in the mtDNAs of other eukaryotes (Leaver and Gray 1982). As a result, our... more
The complicated restriction patterns of plant mtDNA suggest that it is unusually large and complex and possesses a type of sequence heterogeneity not found in the mtDNAs of other eukaryotes (Leaver and Gray 1982). As a result, our knowledge of the genetic function and organization of this important organelle genome is much less advanced than in the case of animal and fungal mtDNAs. As one approach to improving this situation, we are identifying and characterizing large restriction fragments encoding specific plant mitochondrial genes. Our work has centered on the mtDNA of wheat, Triticum aestivum, and has focused particularly on the rRNA genes. DISCUSSION Novel Arrangement of rRNA Genes in Wheat mtDNA The mitochondrial 26S and 18S rRNAs of wheat differ from their cytosol counterparts in physicochemical properties (Cunningham and Gray 1977), T1 oligonucleotide fingerprints (Cunningham et al. 1976), and (in the case of the 18S rRNAs) T1 oligonucleotide catalogs (Bonen et al. 1977). Wh...
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Sanguina nivaloides is the main alga forming red snowfields in high mountains and Polar Regions. It is non-cultivable. Analysis of environmental samples by X-ray tomography, focused-ion-beam scanning-electron-microscopy, physicochemical... more
Sanguina nivaloides is the main alga forming red snowfields in high mountains and Polar Regions. It is non-cultivable. Analysis of environmental samples by X-ray tomography, focused-ion-beam scanning-electron-microscopy, physicochemical and physiological characterization reveal adaptive traits accounting for algal capacity to reside in snow. Cysts populate liquid water at the periphery of ice, are photosynthetically active, can survive for months, and are sensitive to freezing. They harbour a wrinkled plasma membrane expanding the interface with environment. Ionomic analysis supports a cell efflux of K+, and assimilation of phosphorus. Glycerolipidomic analysis confirms a phosphate limitation. The chloroplast contains thylakoids oriented in all directions, fixes carbon in a central pyrenoid and produces starch in peripheral protuberances. Analysis of cells stored in the dark show that starch is a short-term carbon storage. The biogenesis of cytosolic droplets shows that they are loa...
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Algae belonging to the Microchloropsis genus are promising organisms for biotech purposes, being able to accumulate large amounts of lipid reserves. These organisms adapt to different trophic conditions, thriving in strict... more
Algae belonging to the Microchloropsis genus are promising organisms for biotech purposes, being able to accumulate large amounts of lipid reserves. These organisms adapt to different trophic conditions, thriving in strict photoautotrophic conditions, as well as in the concomitant presence of light plus reduced external carbon as energy sources (mixotrophy). In this work, we investigated the mixotrophic responses of Microchloropsis gaditana (formerly Nannochloropsis gaditana). Using the Biolog growth test, in which cells are loaded into multiwell plates coated with different organic compounds, we could not find a suitable substrate for Microchloropsis mixotrophy. By contrast, addition of the Lysogeny broth (LB) to the inorganic growth medium had a benefit on growth, enhancing respiratory activity at the expense of photosynthetic performances. To further dissect the role of respiration in Microchloropsis mixotrophy, we focused on the mitochondrial alternative oxidase (AOX), a protein...
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The so-called "complex" plastids from diatoms possessing four envelope membranes are a typical feature of algae that arose from secondary endosymbiosis. Studying isolated plastids from these algae may allow answering a number of... more
The so-called "complex" plastids from diatoms possessing four envelope membranes are a typical feature of algae that arose from secondary endosymbiosis. Studying isolated plastids from these algae may allow answering a number of fundamental questions regarding diatom photosynthesis and plastid functionality. Due to their complex architecture and their integration into the cellular endoplasmic reticulum (ER) system, their isolation though is still challenging. In this work, we report a reliable isolation technique that is applicable for the two model diatoms Thalassiosira pseudonana and Phaeodactylum tricornutum. The resulting plastid-enriched fractions are of homogenous quality, almost free from cellular contaminants, and feature structurally intact thylakoids that are capable to perform oxygenic photosynthesis, though in most cases they seem to lack most of the stromal components as well as plastid envelopes.
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Figure S4. Time-lapse imaging of RIC4 dynamics of a pollen tube treated with Disruptol-B for 2 h. (PDF 169 kb)
Video S2. Time-lapse imaging of actin dynamics in Arabidopsis thaliana pollen tubes treated for 6 h with Disruptol-A. A frame was acquired every 3 s during 5 min. (MP4 967 kb)
Figure S2. Time-lapse observations of actin dynamics in Arabidopsis thaliana pollen tubes treated for 2, 4 and 6 h with the compounds. (PDF 220 kb)
The outer layer of the pollen grain, the exine, plays a key role in the survival of terrestrial plant life. However, the exine structure in different groups of plants remains enigmatic. Modern and fossil coniferous bisaccate pollen were... more
The outer layer of the pollen grain, the exine, plays a key role in the survival of terrestrial plant life. However, the exine structure in different groups of plants remains enigmatic. Modern and fossil coniferous bisaccate pollen were examined to investigate the detailed three-dimensional structure and properties of the pollen wall. X-ray nano-tomography was used to provide high-resolution imagery, revealing a solid nano-foam structure. Atomic force microscopy measurements were used to compare the pollen wall with other natural and synthetic foams and to demonstrate that the mechanical properties of the wall in this type of pollen are retained for millions of years in fossil specimens. The microscopic structure of this robust biological material described here for the first time, has potential applications in materials sciences and also contributes to our understanding of the evolutionary success of conifers and other plants over geological time.
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Research Interests: Stem Cells, Biology, Immunohistochemistry, Transmission Electron Microscopy, Confocal Microscopy, and 14 moreMedicine, Arabidopsis thaliana, Biological Sciences, Organelles, Chlorophyll, Biochemical, Arabidopsis, Phenotype, CHEMICAL SCIENCES, PLANT PROTEINS, Thylakoid membrane, Chloroplasts, Thylakoids, and Medical and Health Sciences
protein FtsZ1 with thylakoid membranes in Arabidopsis
doi: 10.3389/fpls.2014.00203 The selective biotin tagging and thermolysin proteolysis of chloroplast outer envelope proteins reveals information on
Using a polyclonal antibody (P23) generated against the human platelet integrin AIIbβ3 and a FITCconjugate secondary antibody, fluorescence is observed at the surface of protoplasts isolated from Arabidopsis thaliana and Rubus fruticosus.... more
Using a polyclonal antibody (P23) generated against the human platelet integrin AIIbβ3 and a FITCconjugate secondary antibody, fluorescence is observed at the surface of protoplasts isolated from Arabidopsis thaliana and Rubus fruticosus. Arabidopsis thaliana cells grown in suspension culture containing P23 and glycylarginylglycylaspartylserine (GRGDS), a synthetic peptide containing the RGD sequence found in many extracellular matrix adhesive proteins demonstrated aberrant cell wall/plasma membrane interactions and organization. When glycoproteins from these plants, purified on a concanavalin A Sepharose 4B, were subjected to SDS/PAGE and Western blotting, under reduced and non-reduced conditions, immunoblots probed with P23 revealed bands in both species. A shift in electrophoretic mobility is observed to different apparent molecular mass when no reducing agent is present. When purified by immunoaffinity chromatography on anti-AIIbβ3 Sepharose or Sepharose linked to the synthetic ...
Research Interests: Plant Biology, Biology, Medicine, Humans, Animals, and 15 morePlants, Glycoproteins, Arabidopsis, Integrins, European, Molecular weight, Amino Acid Sequence, Cell Wall, Epitopes, PLANT PROTEINS, Plasma Membrane, Integrin, Biochemistry and cell biology, Immunoblotting, and Medical biochemistry and metabolomics
Phytoplankton is a minor fraction of the global biomass playing a major role in primary production and climate. Despite improved understanding of phytoplankton diversity and genomics, we lack nanoscale subcellular imaging approaches to... more
Phytoplankton is a minor fraction of the global biomass playing a major role in primary production and climate. Despite improved understanding of phytoplankton diversity and genomics, we lack nanoscale subcellular imaging approaches to understand their physiology and cell biology. Here, we present a complete Focused Ion Beam - Scanning Electron Microscopy (FIB-SEM) workflow (from sample preparation to image processing) to generate nanometric 3D phytoplankton models. Tomograms of entire cells, representatives of six ecologically-successful phytoplankton unicellular eukaryotes, were used for quantitative morphometric analysis. Besides lineage-specific cellular architectures, we observed common features related to cellular energy management: i) conserved cell-volume fractions occupied by the different organelles; ii) consistent plastid-mitochondria interactions, iii) constant volumetric ratios in these energy-producing organelles. We revealed detailed subcellular features related to ch...
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FtsZ proteins of the FtsZ1 and FtsZ2 families play important roles in the initiation and progression of plastid division in plants and green algae. Arabidopsis possesses a single FTSZ1 member and two FTSZ2 members, FTSZ2-1 and FTSZ2-2.... more
FtsZ proteins of the FtsZ1 and FtsZ2 families play important roles in the initiation and progression of plastid division in plants and green algae. Arabidopsis possesses a single FTSZ1 member and two FTSZ2 members, FTSZ2-1 and FTSZ2-2. The contribution of these to chloroplast division and partitioning has been mostly investigated in leaf mesophyll tissues. Here, we assessed the involvement of the three FtsZs in plastid division at earlier stages of chloroplast differentiation. To this end, we studied the effect of the absence of specific FtsZ proteins on plastids in the vegetative shoot apex, where the proplastid-to-chloroplast transition takes place. We found that the relative contribution of the two major leaf FtsZ isoforms, FtsZ1 and FtsZ2-1, to the division process varies with cell lineage and position within the shoot apex. While FtsZ2-1 dominates division in the L1 and L3 layers of the shoot apical meristem (SAM), in the L2 layer, FtsZ1 and FtsZ2-1 contribute equally toward the process. Depletion of the third isoform, FtsZ2-2, generally resulted in stronger effects in the shoot apex than those observed in mature leaves. The implications of these findings, along with additional observations made in this work, to our understanding of the mechanisms and regulation of plastid proliferation in the shoot apex are discussed.
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The existence of extranuclear genetic information in the cytoplasm of higher plants was discerned long ago by formal genetics. However, it was not until the early 1960’s that direct evidence was obtained of the isolation of both... more
The existence of extranuclear genetic information in the cytoplasm of higher plants was discerned long ago by formal genetics. However, it was not until the early 1960’s that direct evidence was obtained of the isolation of both chloro-plastic (ct) DNA and mitochondrial (mt) DNA.
FtsZ is a key protein involved in bacterial and organellar division. Bacteria have only one ftsZ gene, while chlorophytes (higher plants and green alga) have two distinct FtsZ gene families, named FtsZ1 and FtsZ2. This raises the question... more
FtsZ is a key protein involved in bacterial and organellar division. Bacteria have only one ftsZ gene, while chlorophytes (higher plants and green alga) have two distinct FtsZ gene families, named FtsZ1 and FtsZ2. This raises the question of why chloro-plasts in these organisms need distinct FtsZ proteins to divide. In order to unravel new functions associated with FtsZ proteins, we have identified and characterized an Arabidopsis thaliana FtsZ1 loss-of-function mutant. ftsZ1-knockout mutants are impeded in chloroplast division, and division is restored when FtsZ1 is expressed at a low level. FtsZ1-overexpressing plants show a drastic inhibition of chloroplast division. Chloroplast morphology is altered in ftsZ1, with chloroplasts having abnormalities in the thylakoid membrane network. Overexpression of FtsZ1 also in-duced defects in thylakoid organization with an increased network of twisting thylakoids and larger grana. We show that FtsZ1, in addition to being present in the strom...
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Thraustochytrids are marine protists that naturally accumulate triacylglycerol with long chains of polyunsaturated fatty acids, such as ω3-docosahexaenoic acid (DHA). They represent a sustainable response to the increasing demand for... more
Thraustochytrids are marine protists that naturally accumulate triacylglycerol with long chains of polyunsaturated fatty acids, such as ω3-docosahexaenoic acid (DHA). They represent a sustainable response to the increasing demand for these “essential” fatty acids (FAs). Following an attempt to transform a strain of Aurantiochytrium limacinum, we serendipitously isolated a clone that did not incorporate any recombinant DNA but contained two to three times more DHA than the original strain. Metabolic analyses indicated a deficit in FA catabolism. However, whole transcriptome analysis did not show down-regulation of genes involved in FA catabolism. Genome sequencing revealed extensive DNA deletion in one allele encoding a putative peroxisomal adenylate transporter. Phylogenetic analyses and yeast complementation experiments confirmed the gene as a peroxisomal adenylate nucleotide transporter (AlANT1), homologous to yeast ScANT1 and plant peroxisomal adenylate nucleotide carrier AtPNC g...
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Light triggers chloroplast differentiation whereby the etioplast transforms into a photosynthesizing chloroplast and the thylakoid rapidly emerges. However, the sequence of events during chloroplast differentiation remains poorly... more
Light triggers chloroplast differentiation whereby the etioplast transforms into a photosynthesizing chloroplast and the thylakoid rapidly emerges. However, the sequence of events during chloroplast differentiation remains poorly understood. Using Serial Block Face Scanning Electron Microscopy (SBF-SEM), we generated a series of chloroplast 3D reconstructions during differentiation, revealing chloroplast number and volume and the extent of envelope and thylakoid membrane surfaces. Furthermore, we used quantitative lipid and whole proteome data to complement the (ultra)structural data, providing a time-resolved, multi-dimensional description of chloroplast differentiation. This showed two distinct phases of chloroplast biogenesis: an initial photosynthesis-enabling ‘Structure Establishment Phase’ followed by a ‘Chloroplast Proliferation Phase’ during cell expansion. Moreover, these data detail thylakoid membrane expansion during de-etiolation at the seedling level and the relative co...
Endosymbioses have shaped the evolutionary trajectory of life and remain ecologically important. Investigating oceanic photosymbioses can illuminate how algal endosymbionts are energetically exploited by their heterotrophic hosts and... more
Endosymbioses have shaped the evolutionary trajectory of life and remain ecologically important. Investigating oceanic photosymbioses can illuminate how algal endosymbionts are energetically exploited by their heterotrophic hosts and inform on putative initial steps of plastid acquisition in eukaryotes. By combining three-dimensional subcellular imaging with photophysiology, carbon flux imaging, and transcriptomics, we show that cell division of endosymbionts (Phaeocystis) is blocked within hosts (Acantharia) and that their cellular architecture and bioenergetic machinery are radically altered. Transcriptional evidence indicates that a nutrient-independent mechanism prevents symbiont cell division and decouples nuclear and plastid division. As endosymbiont plastids proliferate, the volume of the photosynthetic machinery volume increases 100-fold in correlation with the expansion of a reticular mitochondrial network in close proximity to plastids. Photosynthetic efficiency tends to i...
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Eukaryotic phytoplankton have a small global biomass but play major roles in primary production and climate. Despite improved understanding of phytoplankton diversity and evolution, we largely ignore the cellular bases of their... more
Eukaryotic phytoplankton have a small global biomass but play major roles in primary production and climate. Despite improved understanding of phytoplankton diversity and evolution, we largely ignore the cellular bases of their environmental plasticity. By comparative 3D morphometric analysis across seven distant phytoplankton taxa, we observe constant volume occupancy by the main organelles and preserved volumetric ratios between plastids and mitochondria. We hypothesise that phytoplankton subcellular topology is modulated by energy-management constraints. Consistent with this, shifting the diatom Phaeodactylum from low to high light enhances photosynthesis and respiration, increases cell-volume occupancy by mitochondria and the plastid CO2-fixing pyrenoid, and boosts plastid-mitochondria contacts. Changes in organelle architectures and interactions also accompany Nannochloropsis acclimation to different trophic lifestyles, along with respiratory and photosynthetic responses. By re...
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Internal chloroplast structures present complex and various characteristics, which are still largely undetermined due to insufficient imaging investigation. Information on chloroplast morphology has traditionally been collected using... more
Internal chloroplast structures present complex and various characteristics, which are still largely undetermined due to insufficient imaging investigation. Information on chloroplast morphology has traditionally been collected using light microscopy (LM), confocal laser scanning microscopy (CLSM), transmission electron microscopy (TEM), and scanning electron microscopy (SEM) techniques. However, recent technological progresses in the field of microscopy have made it possible to visualize the internal structure of chloroplast in far greater detail and in 3D. Here we recapitulate protocols to visualize chloroplasts from Arabidopsis leaves and Phaeodactylum tricornutum cells with confocal and transmission electron microscopy together with a new technique using a focused ion beam-scanning electron microscope (FIB-SEM) allowing for 3D imaging.
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Photosynthesis is a unique process that allows independent colonization of the land by plants and of the oceans by phytoplankton. Although the photosynthesis process is well understood in plants, we are still unlocking the mechanisms... more
Photosynthesis is a unique process that allows independent colonization of the land by plants and of the oceans by phytoplankton. Although the photosynthesis process is well understood in plants, we are still unlocking the mechanisms evolved by phytoplankton to achieve extremely efficient photosynthesis. Here, we combine biochemical, structural and in vivo physiological studies to unravel the structure of the plastid in diatoms, prominent marine eukaryotes. Biochemical and immunolocalization analyses reveal segregation of photosynthetic complexes in the loosely stacked thylakoid membranes typical of diatoms. Separation of photosystems within subdomains minimizes their physical contacts, as required for improved light utilization. Chloroplast 3D reconstruction and in vivo spectroscopy show that these subdomains are interconnected, ensuring fast equilibration of electron carriers for efficient optimum photosynthesis. Thus, diatoms and plants have converged towards a similar functional...
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Nannochloropsis species are oleaginous eukaryotes containing a plastid limited by four membranes, deriving from a secondary endosymbiosis. In Nannochloropsis, thylakoid lipids, including monogalactosyldiacylglycerol (MGDG), are enriched... more
Nannochloropsis species are oleaginous eukaryotes containing a plastid limited by four membranes, deriving from a secondary endosymbiosis. In Nannochloropsis, thylakoid lipids, including monogalactosyldiacylglycerol (MGDG), are enriched in eicosapentaenoic acid (EPA). The need for EPA in MGDG is not understood. Fatty acids are de novo synthesized in the stroma, then converted into very-long-chain polyunsaturated fatty acids (FAs) at the endoplasmic reticulum (ER). The production of MGDG relies therefore on an EPA supply from the ER to the plastid, following an unknown process. We identified seven elongases and five desaturases possibly involved in EPA production in Nannochloropsis gaditana Among the six heterokont-specific saturated FA elongases possibly acting upstream in this pathway, we characterized the highly expressed isoform Δ0-ELO1 Heterologous expression in yeast (Saccharomyces cerevisiae) showed that NgΔ0-ELO1 could elongate palmitic acid. Nannochloropsis Δ0-elo1 mutants e...
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Life can thrive in extreme environments where inhospitable conditions prevail. Organisms which resist, for example, acidity, pressure, low or high temperature, have been found in harsh environments. Most of them are bacteria and archaea.... more
Life can thrive in extreme environments where inhospitable conditions prevail. Organisms which resist, for example, acidity, pressure, low or high temperature, have been found in harsh environments. Most of them are bacteria and archaea. The bacterium Deinococcus radiodurans is considered to be a champion among all living organisms, surviving extreme ionizing radiation levels. We have discovered a new extremophile eukaryotic organism that possesses a resistance to ionizing radiations similar to that of D. radiodurans. This microorganism, an autotrophic freshwater green microalga, lives in a peculiar environment, namely the cooling pool of a nuclear reactor containing spent nuclear fuels, where it is continuously submitted to nutritive, metallic, and radiative stress. We investigated its morphology and its ultrastructure by light, fluorescence and electron microscopy as well as its biochemical properties. Its resistance to UV and gamma radiation was assessed. When submitted to different dose rates of the order of some tens of mGy · h(-1) to several thousands of Gy · h(-1) , the microalga revealed to be able to survive intense gamma-rays irradiation, up to 2,000 times the dose lethal to human. The nuclear genome region spanning the genes for small subunit ribosomal RNA-Internal Transcribed Spacer (ITS) 1-5.8S rRNA-ITS2-28S rRNA (beginning) was sequenced (4,065 bp). The phylogenetic position of the microalga was inferred from the 18S rRNA gene. All the revealed characteristics make the alga a new species of the genus Coccomyxa in the class Trebouxiophyceae, which we name Coccomyxa actinabiotis sp. nov.
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ABSTRACT
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Research Interests: Genetics, Plant Biology, Medicinal Plants, Comparative Study, Plant Molecular Biology, and 15 moreDNA, Sequence alignment, Chlorophyll, Homology, Fabaceae, Amino Acid Sequence, Base Sequence, Photosystem II, Protein Binding, PISUM SATIVUM, Chlorophyll a, Biochemistry and cell biology, Molecular Sequence Data, Nucleotide sequence, and photosystem
In higher plants, the FtsZ protein, the ancestor of tubulin, has been shown to be implicated in both proplastid division, which occurs in dividing cells and in the division of the differentiated plastids present in non-dividing cells.... more
In higher plants, the FtsZ protein, the ancestor of tubulin, has been shown to be implicated in both proplastid division, which occurs in dividing cells and in the division of the differentiated plastids present in non-dividing cells. Here we report studies on the expression of the two FtsZ gene families in higher plants, FtsZ1 and FtsZ2, in non-synchronized and synchronized tobacco BY2 cells. We have isolated and characterized members of each gene family from Nicotiana tabacum. Specific cDNA probes for each tobacco FtsZ gene family and polyclonal antibodies specific for the FtsZ1 and FtsZ2 proteins were obtained in order to determine mRNA and protein levels. A constant level of FtsZ1 and FtsZ2 transcripts and proteins was observed in non-synchronized cell cultures. However, a complex pattern of expression of both gene families was observed during the cell cycle in synchronized cells, with mRNA and protein levels peaking during cell division, thus implying that the FtsZ proteins may be involved in plastid transmission to the two daughter cells.