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When maize calluses are grown in the presence of the RGD peptide, important morphological changes are observed indicating the presence of a likely RGD-binding receptor. Polyclonal antibodies generated against the human L L1 integrin subunit, the platelet integrin K KIIbL L3 (P23) and antibodies specific for either the L L3 platelet chain or the K KIIb polypeptide crossreact with glycoproteins in Western blot analyses. Immunoprecipitation assays indicate that this maize integrin-like proteindoi:10.1016/s0014-5793(98)01634-2 pmid:9928986 fatcat:4lpjgdsirjhfpl2kcpkmrasqra
more »... es structural similarities with the animal K KIIbL L3 complex. We also show that AcAt2, a polyclonal antibody raised against Arabidopsis proteins purified on an RGD column, interacts with a maize protein. z 1999 Federation of European Biochemical Societies.
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/plasmadoi:10.1046/j.1432-1327.1998.2530552.x pmid:9654050 fatcat:mzy4nf2hsjbolnzhp6y5fhvhqm
more »... rane 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 peptide D-Arg-Gly-Asp-Trp, the major antigenic components detected migrate at 30 kDa and 60 kDa in the first experiment and 60 kDa in the second one. Only the 60-kDa component is immunodetected with antibodies specific for either the β3 platelet chain or the AIIb polypeptide, suggesting the presence of two polypeptides co-migrating. To address more precisely the structure of this complex in plants, competition assays were performed. A significant inhibition is observed with CS3 a monoclonal antibody that interacts with the complexed form AIIbβ3 but not the dissociated subunits. Further structural similarities with the animal AIIbβ3 complex is demonstrated with Western blotting detection after plant glycoproteins immunoprecipitation with CS3 in absence or presence of 5 mM EDTA to dissociate the complex. We also present data on the characterization of a polyclonal antibody, named AcAt2, raised against Arabidopsis glycocoproteins purified by affinity chromatography on a D-RGDW column and eluted with the same peptide, that specifically interacts with the animal AIIbβ3 receptor.
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,doi:10.1101/2020.08.30.274043 fatcat:rrchsovlcvhcbgfw5yobokkdoq
more »... e 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.
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 reliesdoi:10.1104/pp.16.01420 pmid:27895203 fatcat:y3ikrgtqzzcbldadcwzoibejam
more »... herefore 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 D0-ELO1. Heterologous expression in yeast (Saccharomyces cerevisiae) showed that NgD0-ELO1 could elongate palmitic acid. Nannochloropsis D0-elo1 mutants exhibited a reduced EPA level and a specific decrease in MGDG. In NgD0-elo1 lines, the impairment of photosynthesis is consistent with a role of EPA-rich MGDG in nonphotochemical quenching control, possibly providing an appropriate MGDG platform for the xanthophyll cycle. Concomitantly with MGDG decrease, the level of triacylglycerol (TAG) containing medium chain FAs increased. In Nannochloropsis, part of EPA used for MGDG production is therefore biosynthesized by a channeled process initiated at the elongation step of palmitic acid by D0-ELO1, thus acting as a committing enzyme for galactolipid production. Based on the MGDG/TAG balance controlled by D0-ELO1, this study also provides novel prospects for the engineering of oleaginous microalgae for biotechnological applications.
Mansour, 1 Bindesh Shrestha, 1 Éric Maréchal, 2 Denis Falconet 2 and Akos Vertes 1* 1 Department of Chemistry, W. M. ...doi:10.1016/j.aca.2015.08.047 pmid:26703248 fatcat:hfvyu5fwmvgdpcitxrccm5qyhe
Titre Adjustments of embryonic photosynthetic activity modulate seed fitness in Arabidopsis thaliana Type de publication Article de revue Auteur Allorent, Guillaume Editeur Wiley URL de la noticedoi:10.1111/nph.13044 pmid:25256557 fatcat:n7mz7fjhy5dajltbdb4oy3kwv4
Edited by Ulf-Ingo Flügge Keywords: Chloroplast division Chloroplast morphology Thylakoid membrane FtsZ Arabidopsis thaliana a b s t r a c t Seed plants and algae have two distinct FtsZ protein families, FtsZ1 and FtsZ2, involved in plastid division. Distinctively, seed plants and mosses contain two FtsZ2 family members (FtsZ2-1 and FtsZ2-2) thus raising the question of the role of these FtsZ2 paralogs in plants. We show that both FtsZ2 paralogs, in addition to being present in the stroma, aredoi:10.1016/j.febslet.2011.03.041 pmid:21439281 fatcat:txao55qikzfhhh42xy23smu3ei
more »... ssociated with the thylakoid membranes and that association is developmentally regulated. We also show that several FtsZ2-1 isoforms are present with distinct intra-plastidial localization. Mutant analyses show that FtsZ2-1 is essential for chloroplast division and that FtsZ2-2 plays a specific role in chloroplast morphology and internal organisation in addition to participating in chloroplast partition.
Glycerolipids constituting the matrix of photosynthetic membranes, from cyanobacteria to chloroplasts of eukaryotic cells, comprise monogalactosyldiacylglycerol, digalactosyldiacylglycerol, sulfoquinovosyldiacylglycerol and phosphatidylglycerol. This review covers our current knowledge on the structural and functional features of these lipids in various cellular models, from prokaryotes to eukaryotes. Their relative proportions in thylakoid membranes result from highly regulated anddoi:10.1016/j.bbabio.2013.09.007 pmid:24051056 fatcat:odezxmh3bffzdnwuhpv2dtozyq
more »... lized metabolic pathways, with a cooperation, in the case of eukaryotes, of non-plastidic compartments. This review also focuses on the role of each of these thylakoid glycerolipids in stabilizing protein complexes of the photosynthetic machinery, which might be one of the reasons for their fascinating conservation in the course of evolution. This article is part of a Special Issue entitled: Dynamic and ultrastructure of bioenergetic membranes and their components.
BMC Plant Biology
During sexual reproduction, pollen grains land on the stigma, rehydrate and produce pollen tubes that grow through the female transmitting-tract tissue allowing the delivery of the two sperm cells to the ovule and the production of healthy seeds. Because pollen tubes are single cells that expand by tip-polarized growth, they represent a good model to study the growth dynamics, cell wall deposition and intracellular machineries. Aiming to understand this complex machinery, we used a lowdoi:10.1186/s12870-019-1743-9 fatcat:5a7zhdbcurdshksfgq3png5urm
more »... t chemical screen approach in order to isolate new tip-growth disruptors. The effect of a chemical inhibitor of monogalactosyldiacylglycerol synthases, galvestine-1, was also investigated. The present work further characterizes their effects on the tip-growth and intracellular dynamics of pollen tubes. Results: Two small compounds among 258 were isolated based on their abilities to perturb pollen tube growth. They were found to disrupt in vitro pollen tube growth of tobacco, tomato and Arabidopsis thaliana. We show that these 3 compounds induced abnormal phenotypes (bulging and/or enlarged pollen tubes) and reduced pollen tube length in a dose dependent manner. Pollen germination was significantly reduced after treatment with the two compounds isolated from the screen. They also affected cell wall material deposition in pollen tubes. The compounds decreased anion superoxide accumulation, disorganized actin filaments and RIC4 dynamics suggesting that they may affect vesicular trafficking at the pollen tube tip. Conclusion: These molecules may alter directly or indirectly ROP1 activity, a key regulator of pollen tube growth and vesicular trafficking and therefore represent good tools to further study cellular dynamics during polarized-cell growth.
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,doi:10.1101/2020.05.19.104166 fatcat:epzlf6wp2zfq5gvhgc6zjk6tmi
more »... presentatives 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 chromatin organization and to biomineralization. Overall, this approach opens new perspectives to study phytoplankton acclimation responses to abiotic and biotic factors at a relevant biological scale
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,doi:10.7554/elife.62709 fatcat:yhthxryhgff5zg2zalxntpajhm
more »... e 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.
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 immunolocalizationdoi:10.1038/ncomms15885 pmid:28631733 pmcid:PMC5481826 fatcat:7cf5fhvfkfh45czvkzx56wdxcq
more »... lyses 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 distribution of the photosystems although via different thylakoid architectures, which likely evolved independently in the land and the ocean.
Endosymbioses have shaped the evolutionary trajectory of life and remain widespread and ecologically important. Investigating modern 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 3D subcellular imaging with photophysiology, carbon flux imaging and transcriptomics, we show that cell division of algal endosymbionts (Phaeocystis) isdoi:10.1101/2020.12.08.416644 fatcat:m4q6ygczhfd2hcvpemets6gcvm
more »... d 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 expansion of a reticular mitochondrial network in close proximity to plastids. Photosynthetic efficiency tends to increase with cell size and photon propagation modeling indicates that the networked mitochondrial architecture enhances light capture. This is accompanied by 150-fold higher carbon uptake and upregulation of genes involved in photosynthesis and carbon fixation, which, in conjunction with a ca.15-fold size increase of pyrenoids demonstrates enhanced primary production in symbiosis. NanoSIMS analysis revealed major carbon allocation to plastids and transfer to the host cell. Invagination of the symbiosome into endosymbionts to optimize metabolic exchanges is strong evidence that the algal metamorphosis is irreversible. Hosts therefore trigger and unambiguously benefit from major bioenergetic remodeling of symbiotic microalgae with important consequences for the oceanic carbon cycle. Unlike other photosymbioses, this interaction represents a so-called cytoklepty, which is a putative initial step towards plastid acquisition.
Plastid division in higher plants is morphologically similar to bacterial cell division, with a process termed binary fission involving constriction of the envelope membranes. FtsZ proteins involved in bacterial division are also present in higher plants, in which the ftsZ genes belong to two distinct families: ftsZ1 and ftsZ2. However, the roles of the corresponding proteins FtsZ1 and FtsZ2 in plastid division have not been determined. Here we show that the expression of plant FtsZ1 and FtsZ2doi:10.1042/bj20041281 pmid:15601251 pmcid:PMC1134996 fatcat:zw4ygyqhnzgrhixanjiwh4ecfa
more »... n bacteria has different effects on cell division, and that distinct protein domains are involved in the process. We have studied the assembly of purified FtsZ1 and FtsZ2 using a chemical cross-linking approach followed by PAGE and electron microscopy analyses of the resulting polymers. This has revealed that FtsZ1 is capable of forming long rod-shaped polymers and rings similar to the bacterial FtsZ structures, whereas FtsZ2 does not form any organized polymer. Moreover, using purified sub-plastidial fractions, we show that both proteins are present in the stroma, and that a subset of FtsZ2 is tightly bound to the purified envelope membranes. These results indicate that FtsZ2 has a localization pattern distinct from that of FtsZ1, which can be related to distinct properties of the proteins. From the results presented here, we propose a model for the sequential topological localization and functions of green plant FtsZ1 and FtsZ2 in chloroplast division.
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