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Sample records for plasmodesmata

  1. Phloem loading through plasmodesmata: a biophysical analysis

    CERN Document Server

    Comtet, Jean; Stroock, Abraham D

    2016-01-01

    In many species, sucrose en route out of the leaf migrates from photosynthetically active mesophyll cells into the phloem down its concentration gradient via plasmodesmata, i.e., symplastically. In some of these plants the process is entirely passive, but in others phloem sucrose is actively converted into larger sugars, raffinose and stachyose, and segregated (trapped), thus raising total phloem sugar concentration to a level higher than in the mesophyll. Questions remain regarding the mechanisms and selective advantages conferred by both of these symplastic loading processes. Here we present an integrated model - including local and global transport and the kinetics of oligomerization - for passive and active symplastic loading. We also propose a physical model of transport through the plasmodesmata. With these models, we predict that: 1) relative to passive loading, oligomerization of sucrose in the phloem, even in the absence of segregation, lowers the sugar content in the leaf required to achieve a given...

  2. Plasmodesmata in Arabidopsis thaliana suspension cells.

    Science.gov (United States)

    Bayer, E; Thomas, C L; Maule, A J

    2004-06-01

    A current challenge in plant biology is to identify the structural and functional components of plasmodesmata (PDs). The use of plant tissue as a source material for plasmodesmal characterisation has had limited success, so we have explored the frequency and features of PDs occurring in suspension cell cultures of Arabidopsis thaliana. This material has the advantages of homogeneity, quantity, and ease of disruption. Using light and electron microscopy and immunostaining for callose and calreticulin, we showed that suspension cells laid down abundant PDs in division walls, and that vestiges of these structures were retained as half PDs even when the cell-to-cell contacts were disrupted during culture growth. Although callose was a reliable marker for PD distribution, which was deposited in an organised collar around the neck of PDs, it was not abundant in unstressed cells. Calreticulin and the chemical stain 3,3'-dihexyloxacarbocyanine iodide also provided useful markers when monitoring PDs in cell wall preparations by light microscopy. Purified cell walls were shown to be virtually free of contamination from cytoplasmic components, except for the presence of small amounts of cortical endoplasmic reticulum attached to PDs. Hence, clean cell walls from A. thaliana suspension cells provide a valuable resource for a proteomic approach to the analysis of plasmodesmal components.

  3. Plasmodesmata: channels for viruses on the move.

    Science.gov (United States)

    Heinlein, Manfred

    2015-01-01

    The symplastic communication network established by plasmodesmata (PD) and connected phloem provides an essential pathway for spatiotemporal intercellular signaling in plant development but is also exploited by viruses for moving their genomes between cells in order to infect plants systemically. Virus movement depends on virus-encoded movement proteins (MPs) that target PD and therefore represent important keys to the cellular mechanisms underlying the intercellular trafficking of viruses and other macromolecules. Viruses and their MPs have evolved different mechanisms for intracellular transport and interaction with PD. Some viruses move from cell to cell by interacting with cellular mechanisms that control the size exclusion limit of PD whereas other viruses alter the PD architecture through assembly of specialized transport structures within the channel. Some viruses move between cells in the form of assembled virus particles whereas other viruses may interact with nucleic acid transport mechanisms to move their genomes in a non-encapsidated form. Moreover, whereas several viruses rely on the secretory pathway to target PD, other viruses interact with the cortical endoplasmic reticulum and associated cytoskeleton to spread infection. This chapter provides an introduction into viruses and their role in studying the diverse cellular mechanisms involved in intercellular PD-mediated macromolecular trafficking.

  4. PLASMODESMOS: ESTRUCTURA Y FUNCIÓN Plasmodesmata: Structure and Function

    Directory of Open Access Journals (Sweden)

    THOMAS DAVID GEYDAN

    Full Text Available Los plasmodesmos son canales que atraviesan la membrana y la pared celular. Estos canales especializados y no pasivos, actúan como compuertas que facilitan y regulan la comunicación y el transporte de sustancias como agua, nutrientes, metabolitos y macromoléculas entre las células vegetales. En los últimos años, una nueva visión sobre estos canales ha surgido y, estudios han demostrado que los plasmodesmos son más complejos de lo que anteriormente se pensaba. En esta nota, se pretende exponer el conocimiento actual sobre dichas estructuras, enfocándonos en su estructura y función.Plasmodesmata are channels that transverse the cell wall and membrane. These specialized and non passive channels act like gates that facilitate and regulate both communication and transportation of molecules such as water, nutrients, metabolites and macromolecules between plant cells. In the last decade a new point of view of plasmodesmata has emerged, and studies have demonstrated that these channels are more complex. In this brief note, we pretend to expose the actual knowledge of plasmodesmata, focusing on their structure and function.

  5. Isolation of plasmodesmata from Arabidopsis suspension culture cells.

    Science.gov (United States)

    Grison, Magali S; Fernandez-Calvino, Lourdes; Mongrand, Sébastien; Bayer, Emmanuelle M F

    2015-01-01

    Due to their position firmly anchored within the plant cell wall, plasmodesmata (PD) are notoriously difficult to isolate from plant tissue. Yet, getting access to isolated PD represents the most straightforward strategy for the identification of their molecular components. Proteomic and lipidomic analyses of such PD fractions have provided and will continue to provide critical information on the functional and structural elements that define these membranous nano-pores. Here, we describe a two-step simple purification procedure that allows isolation of pure PD-derived membranes from Arabidopsis suspension cells. The first step of this procedure consists in isolating cell wall fragments containing intact PD while free of contamination from other cellular compartments. The second step relies on an enzymatic degradation of the wall matrix and the subsequent release of "free" PD. Isolated PD membranes provide a suitable starting material for the analysis of PD-associated proteins and lipids.

  6. Plasmodesmata: intercellular tunnels facilitating transport of macromolecules in plants.

    Science.gov (United States)

    Kragler, Friedrich

    2013-04-01

    In plants, intercellular structures named plasmodesmata (PD) form a continuous cytoplasmic network between neighboring cells. PD pores provide channels for intercellular symplasmic (cell-to-cell) transport throughout most tissues of the plant body. Cell-defining proteins, such as transcription factors, and regulatory non-coding sequences, such as short interfering RNA, micro RNA, protein-encoding messenger RNAs, viroids, and viral RNA/DNA genomes move via PD channels to adjacent cells. PD-mediated intercellular transport of macromolecules is a regulated process depending on the tissue, developmental stage, and nature of the transported macromolecule. In this review, PD channels and their similarity to tunneling nanotubes present in animals are highlighted. In addition, homeodomain protein movement and cellular components regulating transport are discussed.

  7. Integument cell differentiation in dandelions (Taraxacum, Asteraceae, Lactuceae) with special attention paid to plasmodesmata.

    Science.gov (United States)

    Płachno, Bartosz J; Kurczyńska, Ewa; Świątek, Piotr

    2016-09-01

    The aim of the paper is to determine what happens with plasmodesmata when mucilage is secreted into the periplasmic space in plant cells. Ultrastructural analysis of the periendothelial zone mucilage cells was performed on examples of the ovule tissues of several sexual and apomictic Taraxacum species. The cytoplasm of the periendothelial zone cells was dense, filled by numerous organelles and profiles of rough endoplasmic reticulum and active Golgi dictyosomes with vesicles that contained fibrillar material. At the beginning of the differentiation process of the periendothelial zone, the cells were connected by primary plasmodesmata. However, during the differentiation and the thickening of the cell walls (mucilage deposition), the plasmodesmata become elongated and associated with cytoplasmic bridges. The cytoplasmic bridges may connect the protoplast to the plasmodesmata through the mucilage layers in order to maintain cell-to-cell communication during the differentiation of the periendothelial zone cells.

  8. Targeting of TMV movement protein to plasmodesmata requires the actin/ER network: evidence from FRAP

    National Research Council Canada - National Science Library

    Wright, Kathryn M; Wood, Nicola T; Roberts, Alison G; Chapman, Sean; Boevink, Petra; Mackenzie, Katrin M; Oparka, Karl J

    2007-01-01

    ...) of tobacco mosaic virus (TMV) is targeted to plasmodesmata (PD). The data show that fluorescence recovery in PD at the leading edge of an infection requires elements of the cortical actin/endoplasmic reticulum (ER...

  9. Plasmodesmata: channels for intercellular signaling during plant growth and development.

    Science.gov (United States)

    Sevilem, Iris; Yadav, Shri Ram; Helariutta, Ykä

    2015-01-01

    Plants have evolved strategies for short- and long-distance communication to coordinate plant development and to adapt to changing environmental conditions. Plasmodesmata (PD) are intercellular nanochannels that provide an effective pathway for both selective and nonselective movement of various molecules that function in diverse biological processes. Numerous non-cell-autonomous proteins (NCAP) and small RNAs have been identified that have crucial roles in cell fate determination and organ patterning during development. Both the density and aperture size of PD are developmentally regulated, allowing formation of spatial symplastic domains for establishment of tissue-specific developmental programs. The PD size exclusion limit (SEL) is controlled by reversible deposition of callose, as well as by some PD-associated proteins. Although a large number of PD-associated proteins have been identified, many of their functions remain unknown. Despite the fact that PD are primarily membranous structures, surprisingly very little is known about their lipid composition. Thus, future studies in PD biology will provide deeper insights into the high-resolution structure and tightly regulated functions of PD and the evolution of PD-mediated cell-to-cell communication in plants.

  10. Plasmodesmata-mediated intercellular signaling during plant growth and development.

    Science.gov (United States)

    Yadav, Shri R; Yan, Dawei; Sevilem, Iris; Helariutta, Ykä

    2014-01-01

    Plasmodesmata (PD) are cytoplasmic channels that connect neighboring cells for cell-to-cell communication. PD structure and function vary temporally and spatially to allow formation of symplastic domains during different stages of plant development. Reversible deposition of callose at PD plays an important role in controlling molecular trafficking through PD by regulating their size exclusion limit. Previously, we reported several semi-dominant mutants for CALLOSE SYNTHASE 3 (CALS3) gene, which overproduce callose at PD in Arabidopsis. By combining two of these mutations in a LexA-VP16-ER (XVE)-based estradiol inducible vector system, a tool known as the "icals3m system" was developed to temporally obstruct the symplastic connections in a specified spatial domain. The system has been successfully tested and used, in combination with other methods, to investigate the route for mobile signals such as the SHR protein, microRNA165/6, and cytokinins in Arabidopsis roots, and also to understand the role of symplastic domain formation during lateral root development. We envision that this tool may also be useful for identifying tissue-specific symplastic regulatory networks and to analyze symplastic movement of metabolites.

  11. Dissecting plasmodesmata molecular composition by mass spectrometry-based proteomics.

    Directory of Open Access Journals (Sweden)

    Emmanuelle Maria Françoise Bayer

    2013-01-01

    Full Text Available In plants, the intercellular communication through the membranous channels called plasmodesmata (PD; singular plasmodesma plays pivotal roles in the orchestration of development, defence responses and viral propagation. PD are dynamic structures embedded in the plant cell wall that are defined by specialised domains of the endoplasmic reticulum and the plasma membrane. PD structure and unique functions are guaranteed by their particular molecular composition. Yet, up to recent years and despite numerous approaches such as mutant screens, immunolocalisation or screening of random cDNAs, only few PD proteins had been conclusively identified and characterised. A clear breakthrough in the search of PD constituents came from mass-spectrometry-based proteomic approaches coupled with subcellular fractionation strategies. Due to their position, firmly anchored in the extracellular matrix, PD are notoriously difficult to isolate for biochemical analysis. Proteomic-based approaches have therefore first relied on the use of cell wall fractions containing embedded PD then on free PD fractions whereby PD membranes were released from the walls by enzymatic degradation. To discriminate between likely contaminants and PD protein candidates, bioinformatics tools have often been used in combination with proteomic approaches. GFP fusion proteins of selected candidates have confirmed the PD association of several protein families. Here we review the accomplishments and limitations of the proteomic based strategies to unravel the functional and structural complexity of PD. We also discuss the role of the identified PD associated proteins.

  12. Formation of secondary plasmodesmata and intercellular passages by means of ACHT

    Institute of Scientific and Technical Information of China (English)

    吴伯骥; 谢明唐; 崔亚亚; 陈毅平; 郭卫红; 蒋辉; 郑国锠

    1995-01-01

    By artificially forcing cytoplasm and chromatin migration between different plant cells and through coculture. the isolation layer with uneven Ihickness was formed between tobacco and spinach cells. Then it was gradually absorbed, thinned, and eliminated finally, so that different plant cells were linked together with each other into chimaera. Under further co-culture condition, secondary half-plasmodesmata, secondary plasmodesmata and intercellular passages (cytomictic channels) were formed on one side or both sides of the walls of the adjoining cells, thus different plant cells were linked into symplastic cell mass. This provides the cell structural and cell physiological basis for further manipulating the intercellular migration of cytoplasm and chvomatin. Various intercellular contacts and passages are described.

  13. Super-resolution imaging of plasmodesmata using three-dimensional structured illumination microscopy

    OpenAIRE

    Fitzgibbon, Jessica; Bell,Karen; King, Emma; Oparka, Karl

    2010-01-01

    We used three-dimensional structured illumination microscopy (3D-SIM) to obtain subdiffraction ("super-resolution") images of plasmodesmata (PD) expressing a green fluorescent protein-tagged viral movement protein (MP) in tobacco (Nicotiana tabacum). In leaf parenchyma cells, we were able to resolve individual components of PD (neck and central cavities) at twice the resolution of a confocal microscope. Within the phloem, MP-green fluorescent protein filaments extended outward from the specia...

  14. Plasmodesmata: Structure and Function Plasmodesmos: Estructura y función

    Directory of Open Access Journals (Sweden)

    Melgarejo Luz Marina

    2006-12-01

    Full Text Available Plasmodesmata are channels that transverse the cell wall and membrane. These specialized and non passive channels act like gates that facilitate and regulate both communication and transportation of molecules such as water, nutrients, metabolites and macromolecules between plant cells. In the last decade a new point of view of plasmodesmata has emerged, and studies have  demonstrated that these channels are more complex. In this brief note, we pretend to expose the actual knowledge of plasmodesmata, focusing on their structure and function.Los plasmodesmos son canales que atraviesan la membrana y la pared celular. Estos canales especializados y no pasivos, actúan como compuertas que facilitan y regulan la comunicación y el transporte de sustancias como agua, nutrientes, metabolitos y macromoléculas entre las células vegetales. En los últimos años, una nueva visión sobre estos canales ha surgido y, estudios han demostrado que los plasmodesmos son más complejos de lo que anteriormente se pensaba. En esta nota, se pretende exponer el conocimiento actual sobre dichas estructuras, enfocándonos en su estructura y función.

  15. Reticulomics: Protein-Protein Interaction Studies with Two Plasmodesmata-Localized Reticulon Family Proteins Identify Binding Partners Enriched at Plasmodesmata, Endoplasmic Reticulum, and the Plasma Membrane.

    Science.gov (United States)

    Kriechbaumer, Verena; Botchway, Stanley W; Slade, Susan E; Knox, Kirsten; Frigerio, Lorenzo; Oparka, Karl; Hawes, Chris

    2015-11-01

    The endoplasmic reticulum (ER) is a ubiquitous organelle that plays roles in secretory protein production, folding, quality control, and lipid biosynthesis. The cortical ER in plants is pleomorphic and structured as a tubular network capable of morphing into flat cisternae, mainly at three-way junctions, and back to tubules. Plant reticulon family proteins (RTNLB) tubulate the ER by dimerization and oligomerization, creating localized ER membrane tensions that result in membrane curvature. Some RTNLB ER-shaping proteins are present in the plasmodesmata (PD) proteome and may contribute to the formation of the desmotubule, the axial ER-derived structure that traverses primary PD. Here, we investigate the binding partners of two PD-resident reticulon proteins, RTNLB3 and RTNLB6, that are located in primary PD at cytokinesis in tobacco (Nicotiana tabacum). Coimmunoprecipitation of green fluorescent protein-tagged RTNLB3 and RTNLB6 followed by mass spectrometry detected a high percentage of known PD-localized proteins as well as plasma membrane proteins with putative membrane-anchoring roles. Förster resonance energy transfer by fluorescence lifetime imaging microscopy assays revealed a highly significant interaction of the detected PD proteins with the bait RTNLB proteins. Our data suggest that RTNLB proteins, in addition to a role in ER modeling, may play important roles in linking the cortical ER to the plasma membrane.

  16. Plasmodesmata without callose and calreticulin in higher plants - open channels for fast symplastic transport?

    Directory of Open Access Journals (Sweden)

    Kirill N. Demchenko

    2014-03-01

    Full Text Available Plasmodesmata (PD represent membrane-lined channels that link adjacent plant cells across the cell wall. PD of higher plants contain a central tube of endoplasmic reticulum called desmotubule. Membrane and lumen proteins seem to be able to move through the desmotubule, but most transport processes through PD occur through the cytoplasmic annulus (Brunkard et al., 2013. Calreticulin (CRT, a highly conserved Ca2+-binding protein found in all multi-cellular eukaryotes, predominantly located in the ER, was shown to localize to PD, though not all PD accumulate CRT. In nitrogen fixing actinorhizal root nodules of the Australian tree Casuarina glauca, the primary walls of infected cells containing the microsymbiont become lignified upon infection. TEM analysis of these nodules showed that during the differentiation of infected cells, PD connecting infected cells, and connecting infected and adjacent uninfected cells, were reduced in number as well as diameter (Schubert et al., 2013. In contrast with PD connecting young infected cells, and most PD connecting mature infected and adjacent uninfected cells, PD connecting mature infected cells did not accumulate CRT. Furthermore, as shown here, these PD were not associated with callose, and based on their diameter, they probably had lost their desmotubules. We speculate that either this is a slow path to PD degradation, or that the loss of callose accumulation and presumably also desmotubules leads to the PD becoming open channels and improves metabolite exchange between cells.

  17. Plasma membrane partitioning: from macro-domains to new views on plasmodesmata

    Directory of Open Access Journals (Sweden)

    Yohann eBoutté

    2014-04-01

    Full Text Available Compartmentalization of cellular functions relies on partitioning of domains of diverse sizes within the plasma membrane (PM. Macro-domains measure several micrometers and contain specific proteins concentrated to specific sides (apical, basal and lateral of the PM conferring a polarity to the cell. Cell polarity is one of the driving forces in tissue and growth patterning. To maintain macro-domains within the PM, eukaryotic cells exert diverse mechanisms to counteract the free lateral diffusion of proteins. Protein activation/inactivation, endocytosis, PM recycling of transmembrane proteins and the role of diffusion barriers in macro-domains partitioning at PM will be discussed. Moreover, as plasmodesmata (PDs are domains inserted within the PM which also mediate tissue and growth patterning, it is essential to understand how segregation of specific set of proteins is maintained at PDs while PDs domains are smaller in size compared to macro-domains. Here, we will present mechanisms allowing restriction of proteins at PM macrodomains, but for which molecular components have been found in PDs proteome. We will explore the hypothesis that partitioning of macro-domains and PDs may be ruled by similar mechanisms.

  18. Plasma membrane partitioning: from macro-domains to new views on plasmodesmata.

    Science.gov (United States)

    Boutté, Yohann; Moreau, Patrick

    2014-01-01

    Compartmentalization of cellular functions relies on partitioning of domains of diverse sizes within the plasma membrane (PM). Macro-domains measure several micrometers and contain specific proteins concentrated to specific sides (apical, basal, and lateral) of the PM conferring a polarity to the cell. Cell polarity is one of the driving forces in tissue and growth patterning. To maintain macro-domains within the PM, eukaryotic cells exert diverse mechanisms to counteract the free lateral diffusion of proteins. Protein activation/inactivation, endocytosis, PM recycling of transmembrane proteins and the role of diffusion barriers in macro-domains partitioning at PM will be discussed. Moreover, as plasmodesmata (PDs) are domains inserted within the PM which also mediate tissue and growth patterning, it is essential to understand how segregation of specific set of proteins is maintained at PDs while PDs domains are smaller in size compared to macro-domains. Here, we will present mechanisms allowing restriction of proteins at PM macro-domains, but for which molecular components have been found in PDs proteome. We will explore the hypothesis that partitioning of macro-domains and PDs may be ruled by similar mechanisms.

  19. Super-resolution imaging of plasmodesmata using three-dimensional structured illumination microscopy.

    Science.gov (United States)

    Fitzgibbon, Jessica; Bell, Karen; King, Emma; Oparka, Karl

    2010-08-01

    We used three-dimensional structured illumination microscopy (3D-SIM) to obtain subdiffraction ("super-resolution") images of plasmodesmata (PD) expressing a green fluorescent protein-tagged viral movement protein (MP) in tobacco (Nicotiana tabacum). In leaf parenchyma cells, we were able to resolve individual components of PD (neck and central cavities) at twice the resolution of a confocal microscope. Within the phloem, MP-green fluorescent protein filaments extended outward from the specialized pore-PD that connect sieve elements (SEs) with their companion cells (CCs) along the tubular sieve element reticulum (SER). The SER was shown to interconnect individual pore-PD at the SE-CC interface. 3D-SIM resolved fine (less than 100 nm) endoplasmic reticulum threads running into individual pore-PD as well as strands that crossed sieve plate pores, structurally linking SEs within a file. Our data reveal that MP entering the SE from the CC may remain associated with the SER. Fluorescence recovery after photobleaching experiments revealed that this MP pool is relatively immobile compared with the membrane probe 3,3'-dihexyloxacarbocyanine iodide, suggesting that MP may become sequestered by the SER once it has entered the SE. The advent of 3D-SIM offers considerable potential in the subdiffraction imaging of plant cells, bridging an important gap between confocal and electron microscopy.

  20. Plasmodesmos: transporte simplástico de herbicidas na planta Plasmodesmata: symplastic transport of herbicides within the plant

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    G. Concenço

    2007-01-01

    Full Text Available Plasmodesmos são canais responsáveis pela conexão citoplasmática entre células vizinhas, possibilitando a troca de moléculas de informação, funcionais, estruturais ou ainda de xenobióticos entre as células pertencentes a um mesmo grupo. Células pertencentes ao mesmo conjunto (domínio constituem-se numa unidade funcional, e substâncias podem se mover entre estas células com velocidade muito superior à observada no transporte através de membranas. Os plasmodesmos podem atuar ainda no transporte a longa distância, tanto pela associação com o floema como pelo intercâmbio entre domínios simplásticos. Quando a planta se encontra sob estresse e as taxas de transporte via xilema e floema são mais reduzidas, os plasmodesmos podem ser mais efetivos no transporte a longa distância, das moléculas de herbicidas sistêmicos. Falta ainda esclarecer se existe afinidade entre moléculas de determinados herbicidas com as proteínas da superfície interna dos plasmodesmos, o que poderia facilitar o transporte desses herbicidas pela manipulação do Tamanho Limite de Exclusão do plasmodesmo, independentemente do tamanho da molécula, bem como determinar se a semelhança com algum composto natural da planta promove maior taxa de transporte simplástico. Pouca importância tem sido dada à participação dos plasmodesmos no transporte de herbicidas sistêmicos. No entanto, o avanço dos trabalhos com produtos marcados e a intensificação das pesquisas em fisiologia vegetal para melhor entendimento dos processos referentes à absorção, translocação, conjugação e/ou degradação de herbicidas podem esclarecer muitos aspectos ainda não definidos do transporte de herbicidas via xilema e floema e sua associação com o apoplasto e domínios simplásticos.Plasmodesmata are plasma channels connecting neighboring cells and allowing the exchange of informational, functional and structural molecules and xenobiotics among cells of the same

  1. Plasmodesmata-located protein overexpression negatively impacts the manifestation of systemic acquired resistance and the long-distance movement of Defective in Induced Resistance1 in Arabidopsis.

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    Carella, P; Isaacs, M; Cameron, R K

    2015-03-01

    Systemic acquired resistance (SAR) is a plant defence response that provides immunity to distant uninfected leaves after an initial localised infection. The lipid transfer protein (LTP) Defective in Induced Resistance1 (DIR1) is an essential component of SAR that moves from induced to distant leaves following a SAR-inducing local infection. To understand how DIR1 is transported to distant leaves during SAR, we analysed DIR1 movement in transgenic Arabidopsis lines with reduced cell-to-cell movement caused by the overexpression of Plasmodesmata-Located Proteins PDLP1 and PDLP5. These PDLP-overexpressing lines were defective for SAR, and DIR1 antibody signals were not observed in phloem sap-enriched petiole exudates collected from distant leaves. Our data support the idea that cell-to-cell movement of DIR1 through plasmodesmata is important during long-distance SAR signalling in Arabidopsis.

  2. A ocorrência de plasmodesmas no endosperma de Coffea arabica L. var. typica Cramer Plasmodesmata in endosperm cells of Coffea arabica L. var. typica Cramer

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    G. C. de Mello Ayres

    1954-01-01

    Full Text Available O endosperma de café, tratado segundo a técnica utilizada por Crafts nos seus estudos com Solanum tuberosum L., evidenciou a ocorrência de plasmodesmas nas paredes de suas células. Êstes plasmodesmas apresentam-se como filamentos tênues, na maioria dos casos geniculados e agregados em grupos, localizados nos "campos de pontuações primárias". O aspecto, a morfologia, a freqüência e a distribuição dos plasmodesmas, no endosperma de café, são sensivelmente semelhantes às estruturas vistas e descritas por Quisumbing, em Diospyros kaki L.Following the technic utilized by Crafts in his work on. the storage tissue of potato tubers (Solanum tuberosum L., it was possible to demonstrate the occurrence of plasmodesmata in cell walls of the endosperm tissue of Coffea arabica L. var. typica Cramer. These plasmodesmata appear more abundantly in the "primary pit fields" of the cell walls, and were found to be very different from those which occur in the potato tuber cells ; their shape, size, and number are very similar to the plasmodesmata reported for the endosperm cells of Diospyros kaki L. by Quisumbing.

  3. A developmental framework for complex plasmodesmata formation revealed by large-scale imaging of the Arabidopsis leaf epidermis.

    Science.gov (United States)

    Fitzgibbon, Jessica; Beck, Martina; Zhou, Ji; Faulkner, Christine; Robatzek, Silke; Oparka, Karl

    2013-01-01

    Plasmodesmata (PD) form tubular connections that function as intercellular communication channels. They are essential for transporting nutrients and for coordinating development. During cytokinesis, simple PDs are inserted into the developing cell plate, while during wall extension, more complex (branched) forms of PD are laid down. We show that complex PDs are derived from existing simple PDs in a pattern that is accelerated when leaves undergo the sink-source transition. Complex PDs are inserted initially at the three-way junctions between epidermal cells but develop most rapidly in the anisocytic complexes around stomata. For a quantitative analysis of complex PD formation, we established a high-throughput imaging platform and constructed PDQUANT, a custom algorithm that detected cell boundaries and PD numbers in different wall faces. For anticlinal walls, the number of complex PDs increased with increasing cell size, while for periclinal walls, the number of PDs decreased. Complex PD insertion was accelerated by up to threefold in response to salicylic acid treatment and challenges with mannitol. In a single 30-min run, we could derive data for up to 11k PDs from 3k epidermal cells. This facile approach opens the door to a large-scale analysis of the endogenous and exogenous factors that influence PD formation.

  4. Plasmodesmata-Mediated Cell-to-Cell Communication in the Shoot Apical Meristem: How Stem Cells Talk.

    Science.gov (United States)

    Kitagawa, Munenori; Jackson, David

    2017-03-01

    Positional information is crucial for the determination of plant cell fates, and it is established based on coordinated cell-to-cell communication, which in turn is essential for plant growth and development. Plants have evolved a unique communication pathway, with tiny channels called plasmodesmata (PD) spanning the cell wall. PD interconnect most cells in the plant and generate a cytoplasmic continuum, to mediate short- and long-distance trafficking of various molecules. Cell-to-cell communication through PD plays a role in transmitting positional signals, however, the regulatory mechanisms of PD-mediated trafficking are still largely unknown. The induction and maintenance of stem cells in the shoot apical meristem (SAM) depends on PDmediated cell-to-cell communication, hence, it is an optimal model for dissecting the regulatory mechanisms of PD-mediated cell-to-cell communication and its function in specifying cell fates. In this review, we summarize recent knowledge of PD-mediated cell-to-cell communication in the SAM, and discuss mechanisms underlying molecular trafficking through PD and its role in plant development.

  5. Plasmodesmata-Mediated Cell-to-Cell Communication in the Shoot Apical Meristem: How Stem Cells Talk

    Directory of Open Access Journals (Sweden)

    Munenori Kitagawa

    2017-03-01

    Full Text Available Positional information is crucial for the determination of plant cell fates, and it is established based on coordinated cell-to-cell communication, which in turn is essential for plant growth and development. Plants have evolved a unique communication pathway, with tiny channels called plasmodesmata (PD spanning the cell wall. PD interconnect most cells in the plant and generate a cytoplasmic continuum, to mediate short- and long-distance trafficking of various molecules. Cell-to-cell communication through PD plays a role in transmitting positional signals, however, the regulatory mechanisms of PD-mediated trafficking are still largely unknown. The induction and maintenance of stem cells in the shoot apical meristem (SAM depends on PDmediated cell-to-cell communication, hence, it is an optimal model for dissecting the regulatory mechanisms of PD-mediated cell-to-cell communication and its function in specifying cell fates. In this review, we summarize recent knowledge of PD-mediated cell-to-cell communication in the SAM, and discuss mechanisms underlying molecular trafficking through PD and its role in plant development.

  6. Interaction between the Alfalfa mosaic virus movement protein and plasmodesmata

    NARCIS (Netherlands)

    Wel, van der N.N.

    2000-01-01

    For a full infection of a host, plant viruses should be able to multiply in the initially infected cell and to spread to neighbouring cells as to eventually invade the entire plant. The viral transport pathway can in principle be divided into two steps, i.e. cell-to-cell movement within tissues, and

  7. Phloem loading in two Scrophulariaceae species. What can drive symplastic flow via plasmodesmata?

    Science.gov (United States)

    Voitsekhovskaja, Olga V; Koroleva, Olga A; Batashev, Denis R; Knop, Christian; Tomos, A Deri; Gamalei, Yuri V; Heldt, Hans-Walter; Lohaus, Gertrud

    2006-01-01

    To determine the driving forces for symplastic sugar flux between mesophyll and phloem, gradients of sugar concentrations and osmotic pressure were studied in leaf tissues of two Scrophulariaceae species, Alonsoa meridionalis and Asarina barclaiana. A. meridionalis has a typical symplastic configuration of minor-vein phloem, i.e. intermediary companion cells with highly developed plasmodesmal connections to bundle-sheath cells. In A. barclaiana, two types of companion cells, modified intermediary cells and transfer cells, were found in minor-vein phloem, giving this species the potential to have a complex phloem-loading mode. We identified all phloem-transported carbohydrates in both species and analyzed the levels of carbohydrates in chloroplasts, vacuoles, and cytoplasm of mesophyll cells by nonaqueous fractionation. Osmotic pressure was measured in single epidermal and mesophyll cells and in whole leaves and compared with calculated values for phloem sap. In A. meridionalis, a 2-fold concentration gradient for sucrose between mesophyll and phloem was found. In A. barclaiana, the major transported carbohydrates, sucrose and antirrhinoside, were present in the phloem in 22- and 6-fold higher concentrations, respectively, than in the cytoplasm of mesophyll cells. The data show that diffusion of sugars along their concentration gradients is unlikely to be the major mechanism for symplastic phloem loading if this were to occur in these species. We conclude that in both A. meridionalis and A. barclaiana, apoplastic phloem loading is an indispensable mechanism and that symplastic entrance of solutes into the phloem may occur by mass flow. The conditions favoring symplastic mass flow into the phloem are discussed.

  8. Phloem Loading in Two Scrophulariaceae Species. What Can Drive Symplastic Flow via Plasmodesmata?1

    Science.gov (United States)

    Voitsekhovskaja, Olga V.; Koroleva, Olga A.; Batashev, Denis R.; Knop, Christian; Tomos, A. Deri; Gamalei, Yuri V.; Heldt, Hans-Walter; Lohaus, Gertrud

    2006-01-01

    To determine the driving forces for symplastic sugar flux between mesophyll and phloem, gradients of sugar concentrations and osmotic pressure were studied in leaf tissues of two Scrophulariaceae species, Alonsoa meridionalis and Asarina barclaiana. A. meridionalis has a typical symplastic configuration of minor-vein phloem, i.e. intermediary companion cells with highly developed plasmodesmal connections to bundle-sheath cells. In A. barclaiana, two types of companion cells, modified intermediary cells and transfer cells, were found in minor-vein phloem, giving this species the potential to have a complex phloem-loading mode. We identified all phloem-transported carbohydrates in both species and analyzed the levels of carbohydrates in chloroplasts, vacuoles, and cytoplasm of mesophyll cells by nonaqueous fractionation. Osmotic pressure was measured in single epidermal and mesophyll cells and in whole leaves and compared with calculated values for phloem sap. In A. meridionalis, a 2-fold concentration gradient for sucrose between mesophyll and phloem was found. In A. barclaiana, the major transported carbohydrates, sucrose and antirrhinoside, were present in the phloem in 22- and 6-fold higher concentrations, respectively, than in the cytoplasm of mesophyll cells. The data show that diffusion of sugars along their concentration gradients is unlikely to be the major mechanism for symplastic phloem loading if this were to occur in these species. We conclude that in both A. meridionalis and A. barclaiana, apoplastic phloem loading is an indispensable mechanism and that symplastic entrance of solutes into the phloem may occur by mass flow. The conditions favoring symplastic mass flow into the phloem are discussed. PMID:16377750

  9. ANK, a host cytoplasmic receptor for the Tobacco mosaic virus cell-to-cell movement protein, facilitates intercellular transport through plasmodesmata.

    Directory of Open Access Journals (Sweden)

    Shoko Ueki

    Full Text Available Plasmodesma (PD is a channel structure that spans the cell wall and provides symplastic connection between adjacent cells. Various macromolecules are known to be transported through PD in a highly regulated manner, and plant viruses utilize their movement proteins (MPs to gate the PD to spread cell-to-cell. The mechanism by which MP modifies PD to enable intercelluar traffic remains obscure, due to the lack of knowledge about the host factors that mediate the process. Here, we describe the functional interaction between Tobacco mosaic virus (TMV MP and a plant factor, an ankyrin repeat containing protein (ANK, during the viral cell-to-cell movement. We utilized a reverse genetics approach to gain insight into the possible involvement of ANK in viral movement. To this end, ANK overexpressor and suppressor lines were generated, and the movement of MP was tested. MP movement was facilitated in the ANK-overexpressing plants, and reduced in the ANK-suppressing plants, demonstrating that ANK is a host factor that facilitates MP cell-to-cell movement. Also, the TMV local infection was largely delayed in the ANK-suppressing lines, while enhanced in the ANK-overexpressing lines, showing that ANK is crucially involved in the infection process. Importantly, MP interacted with ANK at PD. Finally, simultaneous expression of MP and ANK markedly decreased the PD levels of callose, β-1,3-glucan, which is known to act as a molecular sphincter for PD. Thus, the MP-ANK interaction results in the downregulation of callose and increased cell-to-cell movement of the viral protein. These findings suggest that ANK represents a host cellular receptor exploited by MP to aid viral movement by gating PD through relaxation of their callose sphincters.

  10. Cytology of the minor-vein phloem in 320 species from the subclass Asteridae suggests a high diversity of phloem-loading modes

    OpenAIRE

    Batashev, Denis R.; Pakhomova, Marina V.; Razumovskaya, Anna V.; Voitsekhovskaja, Olga V.; Gamalei, Yuri V.

    2013-01-01

    The discovery of abundant plasmodesmata at the bundle sheath/phloem interface in Oleaceae (Gamalei, 1974) and Cucurbitaceae (Turgeon et al., 1975) opened the questions whether these plasmodesmata are functional in phloem loading and how widespread is symplasmic loading. Analysis of over 800 dicot species allowed the definition of ‘open’ and ‘closed’ types of the minor vein phloem depending on the abundance of plasmodesmata between companion cells and bundle sheath (Gamalei, 1989; 1990). These...

  11. Cytology of the minor-vein phloem in 320 species from the subclass Asteridae suggests a high diversity of phloem-loading modes †

    OpenAIRE

    Batashev, Denis R.; Pakhomova, Marina V.; Razumovskaya, Anna V.; Voitsekhovskaja, Olga V.; Gamalei, Yuri V.

    2013-01-01

    The discovery of abundant plasmodesmata at the bundle sheath/phloem interface in Oleaceae (Gamalei, 1974) and Cucurbitaceae (Turgeon et al., 1975) raised the questions as to whether these plasmodesmata are functional in phloem loading and how widespread symplasmic loading would be. Analysis of over 800 dicot species allowed the definition of “open” and “closed” types of the minor vein phloem depending on the abundance of plasmodesmata between companion cells and bundle sheath (Gamalei, 1989, ...

  12. Plasmodesmatal Dynamics in Both Woody Poplar and Herbaceous Winter Wheat Under Controlled Short Day and in Field Winter Period

    Institute of Scientific and Technical Information of China (English)

    JIANLing-Cheng; WANGHong

    2004-01-01

    Electron microscopic observation revealed that poplar (Populus deltoides Marsh.) and winterwheat ( Triticum aestivum L. cv. Seward 80004) plasmodesmatal structures significantly changed undershort day (SD, 8 h light) and in winter period, and such changes differed also noticeably between these twowoody and herbaceous plants. Under long day (LD, 16 h light), many plasmodesmata with strong stainappeared in the cell wall of both poplar apical buds and winter wheat young leaf tissues, and connections ofcytoplasmic endoplasmic reticulum (ER) with the ER in some plasmodesmata were observed. In addition,the typical “neck type” plasmodesmata were observed in winter wheat young leaf tissues, and their centraldesmotubules (appressed-ER) could be clearly identified. Under SD, many poplar plasmodesmata showedonly a partial structure in the cell wall and appeared to be discontinued; some plasmodesmata swelled in themid-wall, forming the cavity, and no appressed-ER appeared, in winter wheat, however, no noticeablealterations of plasmodesmata occurred, and the plasmodesmatal structure essentially remained the sameas it was under LD. In winter period, poplar plasmodesmata had a similar morphology as those observedunder SD, however, winter wheat manifested at least two types of significant plasmodesmatal alterations:one plugged by electron-dense materials and the other of reduced neck region compared to those underLD. The above dynamic difference of the two species plasmodesmata under SD and winter period revealedthe difference of their dormancy development under those environmental conditions.

  13. Identification of a Functional Plasmodesmal Localization Signal in a Plant Viral Cell-To-Cell-Movement Protein

    Directory of Open Access Journals (Sweden)

    Cheng Yuan

    2016-01-01

    Full Text Available Our fundamental knowledge of the protein-sorting pathways required for plant cell-to-cell trafficking and communication via the intercellular connections termed plasmodesmata has been severely limited by the paucity of plasmodesmal targeting sequences that have been identified to date. To address this limitation, we have identified the plasmodesmal localization signal (PLS in the Tobacco mosaic virus (TMV cell-to-cell-movement protein (MP, which has emerged as the paradigm for dissecting the molecular details of cell-to-cell transport through plasmodesmata. We report here the identification of a bona fide functional TMV MP PLS, which encompasses amino acid residues between positions 1 and 50, with residues Val-4 and Phe-14 potentially representing critical sites for PLS function that most likely affect protein conformation or protein interactions. We then demonstrated that this PLS is both necessary and sufficient for protein targeting to plasmodesmata. Importantly, as TMV MP traffics to plasmodesmata by a mechanism that is distinct from those of the three plant cell proteins in which PLSs have been reported, our findings provide important new insights to expand our understanding of protein-sorting pathways to plasmodesmata.

  14. Potato spindle tuber viroid detection in phloem exudates and guttation fluid of tomato plants (Solanum lycopersicum)

    Science.gov (United States)

    Potato spindle tuber viroid (PSTVd) is a single-stranded, non protein-encoding, covalently-closed circular RNA molecule (359nt) that infects many horticultural and agricultural crops. PSTVd is mechanically transmitted, replicates in the nucleus, and moves cell-to-cell through plasmodesmata. Though i...

  15. Diffusion or bulk flow

    DEFF Research Database (Denmark)

    Schulz, Alexander

    2015-01-01

    oligomerization, and leads to a high sugar accumulation in the phloem, even though the phloem is not symplasmically isolated, but well coupled by plasmodesmata (PD). Hence the mode polymer-trap mode is also designated active symplasmic loading. For woody angiosperms and gymnosperms an alternate loading mode...

  16. Pit membranes of Ephedra resemble gymnosperms more than angiosperms

    Science.gov (United States)

    Roland Dute; Lauren Bowen; Sarah Schier; Alexa Vevon; Troy Best; Maria Auad; Thomas Elder; Pauline Bouche; Steven Jansen

    2014-01-01

    Bordered pit pairs of Ephedra species were characterized using different types of microscopy. Pit membranes contained tori that did not stain for lignin. SEM and AFM views of the torus surface showed no plasmodesmatal openings, but branched, secondary plasmodesmata were occasionally noted using TEM in conjunction with ultrathin sections. The margo consisted of radial...

  17. In vivo quantification of cell coupling in plants with different phloem-loading strategies.

    Science.gov (United States)

    Liesche, Johannes; Schulz, Alexander

    2012-05-01

    Uptake of photoassimilates into the leaf phloem is the key step in carbon partitioning and phloem transport. Symplasmic and apoplasmic loading strategies have been defined in different plant taxa based on the abundance of plasmodesmata between mesophyll and phloem. For apoplasmic loading to occur, an absence of plasmodesmata is a sufficient but not a necessary criterion, as passage of molecules through plasmodesmata might well be blocked or restricted. Here, we present a noninvasive, whole-plant approach to test symplasmic coupling and quantify the intercellular flux of small molecules using photoactivation microscopy. Quantification of coupling between all cells along the prephloem pathways of the apoplasmic loader Vicia faba and Nicotiana tabacum showed, to our knowledge for the first time in vivo, that small solutes like sucrose can diffuse through plasmodesmata up to the phloem sieve element companion cell complex (SECCC). As expected, the SECCC was found to be symplasmically isolated for small solutes. In contrast, the prephloem pathway of the symplasmic loader Cucurbita maxima was found to be well coupled with the SECCC. Phloem loading in gymnosperms is not well understood, due to a profoundly different leaf anatomy and a scarcity of molecular data compared with angiosperms. A cell-coupling analysis for Pinus sylvestris showed high symplasmic coupling along the entire prephloem pathway, comprising at least seven cell border interfaces between mesophyll and sieve elements. Cell coupling together with measurements of leaf sap osmolality indicate a passive symplasmic loading type. Similarities and differences of this loading type with that of angiosperm trees are discussed.

  18. Plasmodesmal-mediated cell-to-cell transport in wheat roots is modulated by anaerobic stress

    Science.gov (United States)

    Cleland, R. E.; Fujiwara, T.; Lucas, W. J.

    1994-01-01

    Cell-to-cell transport of small molecules and ions occurs in plants through plasmodesmata. Plant roots are frequently subjected to localized anaerobic stress, with a resultant decrease in ATP. In order to determine the effect of this stress on plasmodesmal transport, fluorescent dyes of increasing molecular weight (0.46 to 1OkDa) were injected into epidermal and cortical cells of 3-day-old wheat roots, and their movement into neighboring cells was determined by fluorescence microscopy. Anaerobiosis was generated by N2 gas or simulated by the presence of sodium azide, both of which reduced the ATP levels in the tissue by over 80%. In the absence of such stress, the upper limit for movement, or size exclusion limit (SEL), of cortical plasmodesmata was roots, indicating that plasmodesmata may be conduits for nucleotide (ATP and ADP) exchange between cells. Upon imposition of stress, the SEL rose to between 5 and 10 kDa. This response of plasmodesmata to a decrease in the level of ATP suggests that they are constricted by an ATP-dependent process so as to maintain a restricted SEL. When roots are subjected to anaerobic stress, an increase in SEL may permit enhanced delivery of sugars to the affected cells of the root where anaerobic respiration could regenerate the needed ATP.

  19. MADS on the move : a study on MADS domain protein function and movement during floral development in Arabidopsis thaliana

    NARCIS (Netherlands)

    Urbanus, S.L.

    2010-01-01

    In this thesis we investigated the behaviour of fluorescently-tagged MADS domain proteins during floral development in the model plant Arabidopsis thaliana, and explored the importance of intercellular transport via plasmodesmata for MADS domain transcription factor functioning. The MADS domain tran

  20. The conundrum of a unique protein encoded by citrus tristeza virus that is dispensable for infection of most hosts yet shows characteristics of a viral movement protein.

    Science.gov (United States)

    Bak, Aurélie; Folimonova, Svetlana Y

    2015-11-01

    Citrus tristeza virus (CTV), one of the most economically important viruses, produces a unique protein, p33, which is encoded only in the genomes of isolates of CTV. Recently, we demonstrated that membrane association of the p33 protein confers virus ability to extend its host range. In this work we show that p33 shares characteristics of viral movement proteins. Upon expression in a host cell, the protein localizes to plasmodesmata and displays the ability to form extracellular tubules. Furthermore, p33 appears to traffic via the cellular secretory pathway and the actin network to plasmodesmata locations and is likely being recycled through the endocytic pathway. Finally, our study reveals that p33 colocalizes with a putative movement protein of CTV, the p6 protein. These results suggest a potential role of p33 as a noncanonical viral movement protein, which mediates virus translocation in the specific hosts.

  1. Quantification of plant cell coupling with live-cell microscopy

    DEFF Research Database (Denmark)

    Liesche, Johannes; Schulz, Alexander

    2015-01-01

    cell wall interface. Transport through plasmodesmata, the cell wall channels that directly connect plant cells, is regulated not only by a fixed size exclusion limit, but also by physiological and pathological adaptation. The noninvasive approach described here offers the possibility of precisely......Movement of nutrients and signaling compounds from cell to cell is an essential process for plant growth and development. To understand processes such as carbon allocation, cell communication, and reaction to pathogen attack it is important to know a specific molecule’s capacity to pass a specific...... determining the plasmodesmata-mediated cell wall permeability for small molecules in living cells. The method is based on photoactivation of the fluorescent tracer caged fluorescein. Non-fluorescent caged fluorescein is applied to a target tissue, where it is taken up passively into all cells. Imaged...

  2. Plasmodesmal Targeting and Accumulation of TMV Movement Protein.

    Science.gov (United States)

    Wright, Kathryn M; Chapman, Sean; Roberts, Alison G

    2007-05-01

    The interaction between tobacco mosaic virus and its host plant cells has been intensively studied as a model for macromolecular trafficking. The observation that GFP-labelled TMV movement protein localises to microtubules led to the suggestion that microtubules are required for the cell to cell movement of the virus. In a recent paper we have demonstrated that the targeting of TMV movement protein to plasmodesmata requires the actin and ER networks, which supports previous evidence from our laboratory that showed that disruption of microtubules did not prevent cell to cell movement of TMV virus, and that a mutated movement protein, which did not localise to micro-tubules, showed enhanced viral movement. In this addendum we speculate where the TMV movement protein accumulates within plasmodesmata, and the relationship of this accumulation to the cell to cell movement of the virus.

  3. Diffusion and bulk flow in phloem loading: A theoretical analysis of the polymer trap mechanism for sugar transport in plants

    Science.gov (United States)

    Dölger, Julia; Rademaker, Hanna; Liesche, Johannes; Schulz, Alexander; Bohr, Tomas

    2014-10-01

    Plants create sugar in the mesophyll cells of their leaves by photosynthesis. This sugar, mostly sucrose, has to be loaded via the bundle sheath into the phloem vascular system (the sieve elements), where it is distributed to growing parts of the plant. We analyze the feasibility of a particular loading mechanism, active symplasmic loading, also called the polymer trap mechanism, where sucrose is transformed into heavier sugars, such as raffinose and stachyose, in the intermediary-type companion cells bordering the sieve elements in the minor veins of the phloem. Keeping the heavier sugars from diffusing back requires that the plasmodesmata connecting the bundle sheath with the intermediary cell act as extremely precise filters, which are able to distinguish between molecules that differ by less than 20% in size. In our modeling, we take into account the coupled water and sugar movement across the relevant interfaces, without explicitly considering the chemical reactions transforming the sucrose into the heavier sugars. Based on the available data for plasmodesmata geometry, sugar concentrations, and flux rates, we conclude that this mechanism can in principle function, but that it requires pores of molecular sizes. Comparing with the somewhat uncertain experimental values for sugar export rates, we expect the pores to be only 5%-10% larger than the hydraulic radius of the sucrose molecules. We find that the water flow through the plasmodesmata, which has not been quantified before, contributes only 10%-20% to the sucrose flux into the intermediary cells, while the main part is transported by diffusion. On the other hand, the subsequent sugar translocation into the sieve elements would very likely be carried predominantly by bulk water flow through the plasmodesmata. Thus, in contrast to apoplasmic loaders, all the necessary water for phloem translocation would be supplied in this way with no need for additional water uptake across the plasma membranes of the

  4. Cytopathological evidence for transport of phytoplasma in infected plants

    Directory of Open Access Journals (Sweden)

    Anna Rudzińska-Langwald

    2014-01-01

    Full Text Available Pleomorphic phytoplasmas were observed in sieve tubes, companion cells and in phloem parenchyma of Tagetes patula L., Helichrysum bracteatum Willd. and Gladiolus sp. L. plants with morphological changes typical for phytoplasma infection. In the pores of the sieve plate phytoplasma cells were seen which suggests that the vertical transport of this pathogen goes in the sieve tubes of infected plants throughout the sieve tube pores. The contact of the sieve tube with the neighbouring cells goes through the plasmodesmata, but no changes of the plasmodesmata were observed in the phloem of infected plants. The size and structure of unchanged plasmodesmata does not allow passing through such big structures like phytoplasma. Instead close contact between phytoplasma cells and vertical sieve tube walls takes place. Damages to the cell wall were observed forming cavities in which the phytoplasma cells were present. The damages of parenchyma and companion cells walls also were seen. In cells where the damages of the walls were observed phytoplasmas were present. The phytoplasma cells were sporadically seen also in the intercellular spaces of parenchyma. These data suggest that horizontal transport depends on damages to the infected plant cell walls caused by the phytoplasma itself.

  5. Lipid Raft, Regulator of Plasmodesmal Callose Homeostasis

    Directory of Open Access Journals (Sweden)

    Arya Bagus Boedi Iswanto

    2017-04-01

    Full Text Available Abstract: The specialized plasma membrane microdomains known as lipid rafts are enriched by sterols and sphingolipids. Lipid rafts facilitate cellular signal transduction by controlling the assembly of signaling molecules and membrane protein trafficking. Another specialized compartment of plant cells, the plasmodesmata (PD, which regulates the symplasmic intercellular movement of certain molecules between adjacent cells, also contains a phospholipid bilayer membrane. The dynamic permeability of plasmodesmata (PDs is highly controlled by plasmodesmata callose (PDC, which is synthesized by callose synthases (CalS and degraded by β-1,3-glucanases (BGs. In recent studies, remarkable observations regarding the correlation between lipid raft formation and symplasmic intracellular trafficking have been reported, and the PDC has been suggested to be the regulator of the size exclusion limit of PDs. It has been suggested that the alteration of lipid raft substances impairs PDC homeostasis, subsequently affecting PD functions. In this review, we discuss the substantial role of membrane lipid rafts in PDC homeostasis and provide avenues for understanding the fundamental behavior of the lipid raft–processed PDC.

  6. Tobacco mosaic virus movement protein enhances the spread of RNA silencing.

    Directory of Open Access Journals (Sweden)

    Hannes Vogler

    2008-04-01

    Full Text Available Eukaryotic cells restrain the activity of foreign genetic elements, including viruses, through RNA silencing. Although viruses encode suppressors of silencing to support their propagation, viruses may also exploit silencing to regulate host gene expression or to control the level of their accumulation and thus to reduce damage to the host. RNA silencing in plants propagates from cell to cell and systemically via a sequence-specific signal. Since the signal spreads between cells through plasmodesmata like the viruses themselves, virus-encoded plasmodesmata-manipulating movement proteins (MP may have a central role in compatible virus:host interactions by suppressing or enhancing the spread of the signal. Here, we have addressed the propagation of GFP silencing in the presence and absence of MP and MP mutants. We show that the protein enhances the spread of silencing. Small RNA analysis indicates that MP does not enhance the silencing pathway but rather enhances the transport of the signal through plasmodesmata. The ability to enhance the spread of silencing is maintained by certain MP mutants that can move between cells but which have defects in subcellular localization and do not support the spread of viral RNA. Using MP expressing and non-expressing virus mutants with a disabled silencing suppressing function, we provide evidence indicating that viral MP contributes to anti-viral silencing during infection. Our results suggest a role of MP in controlling virus propagation in the infected host by supporting the spread of silencing signal. This activity of MP involves only a subset of its properties implicated in the spread of viral RNA.

  7. Cytology of the minor-vein phloem in 320 species from the subclass Asteridae suggests a high diversity of phloem-loading modes

    Directory of Open Access Journals (Sweden)

    Denis R. Batashev

    2013-08-01

    Full Text Available The discovery of abundant plasmodesmata at the bundle sheath/phloem interface in Oleaceae (Gamalei, 1974 and Cucurbitaceae (Turgeon et al., 1975 opened the questions whether these plasmodesmata are functional in phloem loading and how widespread is symplasmic loading. Analysis of over 800 dicot species allowed the definition of ‘open’ and ‘closed’ types of the minor vein phloem depending on the abundance of plasmodesmata between companion cells and bundle sheath (Gamalei, 1989; 1990. These types corresponded to potential symplasmic and apoplasmic phloem loaders, respectively; however, this definition covered a spectrum of diverse structures of phloem endings. Here, a review of detailed cytological analyses of minor veins in 320 species from the subclass Asteridae is presented, including data on several cell types and their combinations which have not been reported previously. The percentage of Asteridae species with ‘open’ minor vein cytology which also contain sieve-element-companion cell complexes with ‘closed’ cytology, i.e. that show specialization for both symplasmic and apoplasmic phloem loading, was determined. Along with recent data confirming the dissimilar functional specialization of structurally different parts of minor vein phloem in the stachyose-translocating species Alonsoa meridionalis (Voitsekhovskaja et al., 2009, these findings suggest that apoplasmic loading is indispensable in a large group of species previously classified as putative symplasmic loaders. Altogether, this study provides formal classifications of companion cells and of minor veins, respectively, in 24 families of the Asteridae based on their structural features, opening the way to a close investigation of the relationship between structure and function in phloem loading.

  8. Histone H3 Interacts and Colocalizes with the Nuclear Shuttle Protein and the Movement Protein of a Geminivirus ▿ †

    Science.gov (United States)

    Zhou, Yanchen; Rojas, Maria R.; Park, Mi-Ri; Seo, Young-Su; Lucas, William J.; Gilbertson, Robert L.

    2011-01-01

    Geminiviruses are plant-infecting viruses with small circular single-stranded DNA genomes. These viruses utilize nuclear shuttle proteins (NSPs) and movement proteins (MPs) for trafficking of infectious DNA through the nuclear pore complex and plasmodesmata, respectively. Here, a biochemical approach was used to identify host factors interacting with the NSP and MP of the geminivirus Bean dwarf mosaic virus (BDMV). Based on these studies, we identified and characterized a host nucleoprotein, histone H3, which interacts with both the NSP and MP. The specific nature of the interaction of histone H3 with these viral proteins was established by gel overlay and in vitro and in vivo coimmunoprecipitation (co-IP) assays. The NSP and MP interaction domains were mapped to the N-terminal region of histone H3. These experiments also revealed a direct interaction between the BDMV NSP and MP, as well as interactions between histone H3 and the capsid proteins of various geminiviruses. Transient-expression assays revealed the colocalization of histone H3 and NSP in the nucleus and nucleolus and of histone H3 and MP in the cell periphery and plasmodesmata. Finally, using in vivo co-IP assays with a Myc-tagged histone H3, a complex composed of histone H3, NSP, MP, and viral DNA was recovered. Taken together, these findings implicate the host factor histone H3 in the process by which an infectious geminiviral DNA complex forms within the nucleus for export to the cell periphery and cell-to-cell movement through plasmodesmata. PMID:21900168

  9. Cytology of the minor-vein phloem in 320 species from the subclass Asteridae suggests a high diversity of phloem-loading modes†

    Science.gov (United States)

    Batashev, Denis R.; Pakhomova, Marina V.; Razumovskaya, Anna V.; Voitsekhovskaja, Olga V.; Gamalei, Yuri V.

    2013-01-01

    The discovery of abundant plasmodesmata at the bundle sheath/phloem interface in Oleaceae (Gamalei, 1974) and Cucurbitaceae (Turgeon et al., 1975) raised the questions as to whether these plasmodesmata are functional in phloem loading and how widespread symplasmic loading would be. Analysis of over 800 dicot species allowed the definition of “open” and “closed” types of the minor vein phloem depending on the abundance of plasmodesmata between companion cells and bundle sheath (Gamalei, 1989, 1990). These types corresponded to potential symplasmic and apoplasmic phloem loaders, respectively; however, this definition covered a spectrum of diverse structures of phloem endings. Here, a review of detailed cytological analyses of minor veins in 320 species from the subclass Asteridae is presented, including data on companion cell types and their combinations which have not been reported previously. The percentage of Asteridae species with “open” minor vein cytology which also contain sieve-element-companion cell complexes with “closed” cytology, i.e., that show specialization for both symplasmic and apoplasmic phloem loading, was determined. Along with recent data confirming the dissimilar functional specialization of structurally different parts of minor vein phloem in the stachyose-translocating species Alonsoa meridionalis (Voitsekhovskaja et al., 2009), these findings suggest that apoplasmic loading is indispensable in a large group of species previously classified as putative symplasmic loaders. Altogether, this study provides formal classifications of companion cells and of minor veins, respectively, in 24 families of the Asteridae based on their structural features, opening the way to a close investigation of the relationship between structure and function in phloem loading. PMID:23970890

  10. Cytology of the minor-vein phloem in 320 species from the subclass Asteridae suggests a high diversity of phloem-loading modes.

    Science.gov (United States)

    Batashev, Denis R; Pakhomova, Marina V; Razumovskaya, Anna V; Voitsekhovskaja, Olga V; Gamalei, Yuri V

    2013-01-01

    The discovery of abundant plasmodesmata at the bundle sheath/phloem interface in Oleaceae (Gamalei, 1974) and Cucurbitaceae (Turgeon et al., 1975) raised the questions as to whether these plasmodesmata are functional in phloem loading and how widespread symplasmic loading would be. Analysis of over 800 dicot species allowed the definition of "open" and "closed" types of the minor vein phloem depending on the abundance of plasmodesmata between companion cells and bundle sheath (Gamalei, 1989, 1990). These types corresponded to potential symplasmic and apoplasmic phloem loaders, respectively; however, this definition covered a spectrum of diverse structures of phloem endings. Here, a review of detailed cytological analyses of minor veins in 320 species from the subclass Asteridae is presented, including data on companion cell types and their combinations which have not been reported previously. The percentage of Asteridae species with "open" minor vein cytology which also contain sieve-element-companion cell complexes with "closed" cytology, i.e., that show specialization for both symplasmic and apoplasmic phloem loading, was determined. Along with recent data confirming the dissimilar functional specialization of structurally different parts of minor vein phloem in the stachyose-translocating species Alonsoa meridionalis (Voitsekhovskaja et al., 2009), these findings suggest that apoplasmic loading is indispensable in a large group of species previously classified as putative symplasmic loaders. Altogether, this study provides formal classifications of companion cells and of minor veins, respectively, in 24 families of the Asteridae based on their structural features, opening the way to a close investigation of the relationship between structure and function in phloem loading.

  11. Diffusion and bulk flow in phloem loading

    DEFF Research Database (Denmark)

    Dölger, Julia; Rademaker, Hanna; Liesche, Johannes

    2014-01-01

    loading mechanism, active symplasmic loading, also called the polymer trap mechanism, where sucrose is transformed into heavier sugars, such as raffinose and stachyose, in the intermediary-type companion cells bordering the sieve elements in the minor veins of the phloem. Keeping the heavier sugars from......%-20% to the sucrose flux into the intermediary cells, while the main part is transported by diffusion. On the other hand, the subsequent sugar translocation into the sieve elements would very likely be carried predominantly by bulk water flow through the plasmodesmata. Thus, in contrast to apoplasmic loaders, all...

  12. Quantification of plant cell coupling with live-cell microscopy

    DEFF Research Database (Denmark)

    Liesche, Johannes; Schulz, Alexander

    2015-01-01

    cell wall interface. Transport through plasmodesmata, the cell wall channels that directly connect plant cells, is regulated not only by a fixed size exclusion limit, but also by physiological and pathological adaptation. The noninvasive approach described here offers the possibility of precisely......Movement of nutrients and signaling compounds from cell to cell is an essential process for plant growth and development. To understand processes such as carbon allocation, cell communication, and reaction to pathogen attack it is important to know a specific molecule’s capacity to pass a specific...

  13. 胞间连丝——植物细胞间交流的纳米通道%Plasmodesmata—the nanotubes for intercellular communication of plants

    Institute of Scientific and Technical Information of China (English)

    段茜茜; 王冬梅

    2017-01-01

    有效的细胞间交流对单细胞生物和多细胞生物的生存至关重要.因为植物细胞被包裹在坚硬的细胞壁内,细胞质内容物的直接胞间交流只能通过胞间连丝,一种连接相邻细胞胞质的膜内衬纳米通道来实现.研究表明,这种膜内衬胞间通道在动物中有与之相似的通道纳米管.它们都能促进各种形式的大分子的交流,同时也使一些病原物利用这些通道从一个宿主细胞移动到另一个细胞.然而,宿主免疫监督系统也已经进化出了多种策略去防止病原物对其利用.最近的一些研究表明,胞间连丝在植物的先天免疫反应中扮演着重要角色,通过此种监督机制把胞间连丝与免疫信号转导通路融为一体.本文主要讨论胞间连丝在细胞间物质交流过程中的调控机制.%Effective intercellular communication is critical for the survival of both unicellular and multicellular organisms. Because plant cells are encased in rigid cell walls, direct cell-to-cell exchange of cytoplasmic con-tent is only possible through plasmodesmata, membrane-lined nanotubes that connect the cytoplasm of adjacent cells. Studies have shown that such membrane-lined intercellular channels have some similar channels which called tunneling nanotubes in animals. They all facilitate the exchange of various forms of macromolecules, but at the same time make some microbial pathogens to exploit those channels to move from one host cell to anoth-er. However, host immune surveillance system may have also evolved strategies to offset such exploitation of them by the pathogen. Some recent discoveries suggest that cellular connectivity via plasmodesmata plays an important role in innate immune responses, and plants integrated plasmodesmata into immune signaling path-ways through the supervision mechanism. In this article, the regulation mechanism of plasmodesmata in inter-cellular communication were discussed.

  14. Ultrastructure of Gladiolus x hybridus root endodermis

    Directory of Open Access Journals (Sweden)

    Anna Rudzińska-Langwald

    2014-01-01

    Full Text Available Gladiolus.x hybridus Van Houtte roots had primary, secondary and tertiary endodermis depending on the distance from the root apex. Free calcium ions were localized with the method of Slocum and Roux (1982. Electron microscopic observations revealed that electron dense calcium antimonite deposits were localized in some endodermis cells. Endodermis cells situated above xylem elements were rich in calcium antimonate deposits in contrary to those situated above the phloem elements and passage cells. The cells rich in calcium ions were present both in endodermis 11 and III stage of development. Localization of calcium deposits was on plasma membrane and tonoplast. There were also numerous calcium antimonate deposits in vacuoles. Dictiosome's cisterns and Golgi derived vesicles show presence of calcium ions. Calcium rich endodermis cells had plastids with antimonate deposits present in their tylacoids lumen. Plasmode-smata looked the same in all endodermis cells, but those from calcium rich endodermis cells had calcium antimonate deposits in the lumen of plasmodesmata.

  15. Cytorhabdovirus P3 genes encode 30K-like cell-to-cell movement proteins.

    Science.gov (United States)

    Mann, Krin S; Bejerman, Nicolas; Johnson, Karyn N; Dietzgen, Ralf G

    2016-02-01

    Plant viruses encode movement proteins (MP) to facilitate cell-to-cell transport through plasmodesmata. In this study, using trans-complementation of a movement-defective turnip vein-clearing tobamovirus (TVCV) replicon, we show for the first time for cytorhabdoviruses (lettuce necrotic yellows virus (LNYV) and alfalfa dwarf virus (ADV)) that their P3 proteins function as MP similar to the TVCV P30 protein. All three MP localized to plasmodesmata when ectopically expressed. In addition, we show that these MP belong to the 30K superfamily since movement was inhibited by mutation of an aspartic acid residue in the critical 30K-specific LxD/N50-70G motif. We also report that Nicotiana benthamiana microtubule-associated VOZ1-like transcriptional activator interacts with LNYV P3 and TVCV P30 but not with ADV P3 or any of the MP point mutants. This host protein, which is known to interact with P3 of sonchus yellow net nucleorhabdovirus, may be involved in aiding the cell-to-cell movement of LNYV and TVCV.

  16. Symplasmic transport and phloem loading in gymnosperm leaves.

    Science.gov (United States)

    Liesche, Johannes; Martens, Helle Juel; Schulz, Alexander

    2011-01-01

    Despite more than 130 years of research, phloem loading is far from being understood in gymnosperms. In part this is due to the special architecture of their leaves. They differ from angiosperm leaves among others by having a transfusion tissue between bundle sheath and the axial vascular elements. This article reviews the somewhat inaccessible and/or neglected literature and identifies the key points for pre-phloem transport and loading of photoassimilates. The pre-phloem pathway of assimilates is structurally characterized by a high number of plasmodesmata between all cell types starting in the mesophyll and continuing via bundle sheath, transfusion parenchyma, Strasburger cells up to the sieve elements. Occurrence of median cavities and branching indicates that primary plasmodesmata get secondarily modified and multiplied during expansion growth. Only functional tests can elucidate whether this symplasmic pathway is indeed continuous for assimilates, and if phloem loading in gymnosperms is comparable with the symplasmic loading mode in many angiosperm trees. In contrast to angiosperms, the bundle sheath has properties of an endodermis and is equipped with Casparian strips or other wall modifications that form a domain border for any apoplasmic transport. It constitutes a key point of control for nutrient transport, where the opposing flow of mineral nutrients and photoassimilates has to be accommodated in each single cell, bringing to mind the principle of a revolving door. The review lists a number of experiments needed to elucidate the mode of phloem loading in gymnosperms.

  17. SURFACE INTERACTIONS OF THE EPIPHYTIC MACROALGA HINCKSIA MITCHELLIAE (PHAEOPHYCEAE) WITH THE SHOALGRASS HALODULE WRIGHTII (CYMODOCEACEAE)(1).

    Science.gov (United States)

    Papini, Alessio; Sordo, Laura; Mosti, Stefano

    2011-02-01

    Meadows of Halodule wrightii (Cymodoceaceae) underwent a decline in a tidal flat located at Paranaguá Bay (Parana, SE Brazil). This decline appeared to be related to an overgrowth of the epiphytic macroalga Hincksia mitchelliae (Harv.) P. C. Silva (Phaeophyceae). In order to characterize the type of epiphytism between the alga and its plant host, we compared two samples from the beginning and end of the algal overgrowth via electron and optical microscopes. The investigation revealed that at both sampling periods, there was an epiphytism of type II, which is due to an infection of epiphytes strongly attached to the surface of the host but not associated to any apparent direct host-tissue damage. The presence of plasmodesmata between the cells of Hincksia only in the late stage of the host-epiphyte interaction indicated a change in the vegetative organization of Hincksia in relation to its host to improve nutrient absorption and distribution through the epiphyte cells. This is the first report on plasmodesmata in H. mitchelliae. The proposed mechanisms with which the algal epiphytes lead seagrasses to death are shadowing by adhesion on Halodule surface and disruption of its osmoregulatory system. Our findings have implications for the conservation and management strategies of seagrass ecosystems.

  18. Starch Mobilization in Ultradried Seed of Maize (Zea mays L.) During Germination

    Institute of Scientific and Technical Information of China (English)

    Xiao-Feng WANG; Xin-Ming JING; Jian LIN

    2005-01-01

    The effects of ultradry storage on the starch mobilization in maize (Zea mays L.) seed after aging were investigated. The results indicated that there were no significant differences in the content of ATP,starch, and soluble sugar, as well as the activity of amylase, between ultradried seeds and seeds stored at -20 ℃ during germination. These results were consistent with the higher level of vigor of the ultradried seed. Sieve tube introduction of a fluorescence dye (carboxyl fluoresceindiacetate) and laser confocal microscopy were used to study the development of plasmodesmata in the ultradried seeds. The results indicated that plasmodesmata developed well in ultradried seeds. Fluorescence analysis also showed that the fluorescence intensity in the radicle of ultradried seeds was stronger than that in seeds with a higher moisture content. This suggests that ultradry treatment has no adverse effects on the seeds. After seed imbibition, cell orgaelles could be resumed. It is concluded that ultradry seed storage is beneficial for maintaining seed vigor and that starchy mobilization proceeds regularly during germination.

  19. Cytochemical localization of calcium in cap cells of primary roots of Zea mays L

    Science.gov (United States)

    Moore, R.

    1986-01-01

    The distribution of calcium (Ca) in caps of vertically- and horizontally-oriented roots of Zea mays was monitored to determine its possible role in root graviresponsiveness. A modification of the antimonate precipitation procedure was used to localize Ca in situ. In vertically-oriented roots, the presumed graviperceptive (i.e., columella) cells were characterized by minimal and symmetric staining of the plasmalemma and mitochondria. No precipitate was present in plasmodesmata or cell walls. Within 5 min after horizontal reorientation, staining was associated with the portion of the cell wall adjacent to the distal end of the cell. This asymmetric staining persisted throughout the onset of gravicurvature. No staining of lateral cell walls of columella cells was observed at any stage of gravicurvature, suggesting that a lateral flow of Ca through the columella tissue of horizontally-oriented roots does not occur. The outermost peripheral cells of roots oriented horizontally and vertically secrete Ca through plasmodesmata-like structures in their cell walls. These results are discussed relative to proposed roles of root-cap Ca in root gravicurvature.

  20. Integument cell gelatinisation-the fate of the integumentary cells in Hieracium and Pilosella (Asteraceae).

    Science.gov (United States)

    Płachno, Bartosz J; Świątek, Piotr; Kozieradzka-Kiszkurno, Małgorzata; Szeląg, Zbigniew; Stolarczyk, Piotr

    2017-05-15

    Members of the genera Hieracium and Pilosella are model plants that are used to study the mechanisms of apomixis. In order to have a proper understanding of apomixis, knowledge about the relationship between the maternal tissue and the gametophyte is needed. In the genus Pilosella, previous authors have described the specific process of the "liquefaction" of the integument cells that surround the embryo sac. However, these observations were based on data only at the light microscopy level. The main aim of our paper was to investigate the changes in the integument cells at the ultrastructural level in Pilosella officinarum and Hieracium alpinum. We found that the integument peri-endothelial zone in both species consisted of mucilage cells. The mucilage was deposited as a thick layer between the plasma membrane and the cell wall. The mucilage pushed the protoplast to the centre of the cell, and cytoplasmic bridges connected the protoplast to the plasmodesmata through the mucilage layers. Moreover, an elongation of the plasmodesmata was observed in the mucilage cells. The protoplasts had an irregular shape and were finally degenerated. After the cell wall breakdown of the mucilage cells, lysigenous cavities that were filled with mucilage were formed.

  1. GBNV encoded movement protein (NSm) remodels ER network via C-terminal coiled coil domain

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Pratibha; Savithri, H.S., E-mail: bchss@biochem.iisc.ernet.in

    2015-08-15

    Plant viruses exploit the host machinery for targeting the viral genome–movement protein complex to plasmodesmata (PD). The mechanism by which the non-structural protein m (NSm) of Groundnut bud necrosis virus (GBNV) is targeted to PD was investigated using Agrobacterium mediated transient expression of NSm and its fusion proteins in Nicotiana benthamiana. GFP:NSm formed punctuate structures that colocalized with mCherry:plasmodesmata localized protein 1a (PDLP 1a) confirming that GBNV NSm localizes to PD. Unlike in other movement proteins, the C-terminal coiled coil domain of GBNV NSm was shown to be involved in the localization of NSm to PD, as deletion of this domain resulted in the cytoplasmic localization of NSm. Treatment with Brefeldin A demonstrated the role of ER in targeting GFP NSm to PD. Furthermore, mCherry:NSm co-localized with ER–GFP (endoplasmic reticulum targeting peptide (HDEL peptide fused with GFP). Co-expression of NSm with ER–GFP showed that the ER-network was transformed into vesicles indicating that NSm interacts with ER and remodels it. Mutations in the conserved hydrophobic region of NSm (residues 130–138) did not abolish the formation of vesicles. Additionally, the conserved prolines at positions 140 and 142 were found to be essential for targeting the vesicles to the cell membrane. Further, systematic deletion of amino acid residues from N- and C-terminus demonstrated that N-terminal 203 amino acids are dispensable for the vesicle formation. On the other hand, the C-terminal coiled coil domain when expressed alone could also form vesicles. These results suggest that GBNV NSm remodels the ER network by forming vesicles via its interaction through the C-terminal coiled coil domain. Interestingly, NSm interacts with NP in vitro and coexpression of these two proteins in planta resulted in the relocalization of NP to PD and this relocalization was abolished when the N-terminal unfolded region of NSm was deleted. Thus, the NSm

  2. Importance of symplasmic communication in cell differentiation.

    Science.gov (United States)

    Marzec, Marek; Kurczynska, Ewa

    2014-01-01

    Symplasmic communication via plasmodesmata (PD) is part of the system of information exchange between plant cells. Molecules that pass through the PD include ions, some hormones, minerals, amino acids, and sugars but also proteins, transcription factors, and different classes of RNA, and as such PD can participate in the coordination of plant growth and development. This review summarizes the current literature on this subject and the role of PD in signal exchange, the importance of symplasmic communication and symplasmic domains in plant cell differentiation, and highlights the future prospective in the exploration of PD functions in plants. Moreover, this review also describes the potential use of barley root epidermis and non-zygotic embryogenesis in study of symplasmic communication during cell differentiation.

  3. Cell-to-cell communication in plants, animals, and fungi: a comparative review

    Science.gov (United States)

    Bloemendal, Sandra; Kück, Ulrich

    2013-01-01

    Cell-to-cell communication is a prerequisite for differentiation and development in multicellular organisms. This communication has to be tightly regulated to ensure that cellular components such as organelles, macromolecules, hormones, or viruses leave the cell in a precisely organized way. During evolution, plants, animals, and fungi have developed similar ways of responding to this biological challenge. For example, in higher plants, plasmodesmata connect adjacent cells and allow communication to regulate differentiation and development. In animals, two main general structures that enable short- and long-range intercellular communication are known, namely gap junctions and tunneling nanotubes, respectively. Finally, filamentous fungi have also developed specialized structures called septal pores that allow intercellular communication via cytoplasmic flow. This review summarizes the underlying mechanisms for intercellular communication in these three eukaryotic groups and discusses its consequences for the regulation of differentiation and developmental processes.

  4. Permeability of cork for water and ethanol.

    Science.gov (United States)

    Fonseca, Ana Luisa; Brazinha, Carla; Pereira, Helena; Crespo, Joao G; Teodoro, Orlando M N D

    2013-10-01

    Transport properties of natural (noncompressed) cork were evaluated for water and ethanol in both vapor and liquid phases. The permeability for these permeants has been measured, as well as the sorption and diffusion coefficients. This paper focuses on the differences between the transport of gases' relevant vapors and their liquids (water and ethanol) through cork. A transport mechanism of vapors and liquids is proposed. Experimental evidence shows that both vapors and liquids permeate not only through the small channels across the cells (plasmodesmata), as in the permeation of gases, but also through the walls of cork cells by sorption and diffusion as in dense membranes. The present study also shows that cork permeability for gases was irreversibly and drastically decreased after cork samples were exposed to ethanol or water in liquid phase.

  5. Plant Vascular Biology 2010

    Energy Technology Data Exchange (ETDEWEB)

    Ding, Biao

    2014-11-17

    This grant supported the Second International Conference on Plant Vascular Biology (PVB 2010) held July 24-28, 2010 on the campus of Ohio State University, Columbus, Ohio. Biao Ding (Ohio State University; OSU) and David Hannapel (Iowa State University; ISU) served as co-chairs of this conference. Biao Ding served as the local organizer. PVB is defined broadly here to include studies on the biogenesis, structure and function of transport systems in plants, under conditions of normal plant growth and development as well as of plant interactions with pathogens. The transport systems cover broadly the xylem, phloem, plasmodesmata and vascular cell membranes. The PVB concept has emerged in recent years to emphasize the integrative nature of the transport systems and approaches to investigate them.

  6. Diffusion and bulk flow in phloem loading - a theoretical analysis of the polymer trap mechanism

    CERN Document Server

    Dölger, Julia; Liesche, Johannes; Schulz, Alexander; Bohr, Tomas

    2014-01-01

    Plants create sugar in the mesophyll cells of their leaves by photosynthesis. This sugar, mostly sucrose, has to be loaded via the bundle sheath into the phloem vascular system (the sieve elements), where it is distributed to growing parts of the plant. We analyse the feasibility of a particular loading mechanism, active symplasmic loading, also called the polymer trap mechanism, where sucrose is transformed into heavier sugars, such as raffinose and stachyose, in the intermediary-type companion cells bordering the sieve elements in the minor veins of the phloem. Keeping the heavier sugars from diffusing back requires that the plasmodesmata connecting the bundle sheath with the intermediary cell act as extremely precise filters, which are able to distinguish between molecules that differ by less than 20% in size. In our modeling, we take into account the coupled water and sugar movement across the relevant interfaces, without explicitly considering the chemical reactions transforming the sucrose into the heav...

  7. Characterization of a proposed dichorhavirus associated with the citrus leprosis disease and analysis of the host response.

    Science.gov (United States)

    Cruz-Jaramillo, José Luis; Ruiz-Medrano, Roberto; Rojas-Morales, Lourdes; López-Buenfil, José Abel; Morales-Galván, Oscar; Chavarín-Palacio, Claudio; Ramírez-Pool, José Abrahán; Xoconostle-Cázares, Beatriz

    2014-07-07

    The causal agents of Citrus leprosis are viruses; however, extant diagnostic methods to identify them have failed to detect known viruses in orange, mandarin, lime and bitter orange trees with severe leprosis symptoms in Mexico, an important citrus producer. Using high throughput sequencing, a virus associated with citrus leprosis was identified, belonging to the proposed Dichorhavirus genus. The virus was termed Citrus Necrotic Spot Virus (CNSV) and contains two negative-strand RNA components; virions accumulate in the cytoplasm and are associated with plasmodesmata-channels interconnecting neighboring cells-suggesting a mode of spread within the plant. The present study provides insights into the nature of this pathogen and the corresponding plant response, which is likely similar to other pathogens that do not spread systemically in plants.

  8. Cell-to-cell communication in plants, animals, and fungi: a comparative review.

    Science.gov (United States)

    Bloemendal, Sandra; Kück, Ulrich

    2013-01-01

    Cell-to-cell communication is a prerequisite for differentiation and development in multicellular organisms. This communication has to be tightly regulated to ensure that cellular components such as organelles, macromolecules, hormones, or viruses leave the cell in a precisely organized way. During evolution, plants, animals, and fungi have developed similar ways of responding to this biological challenge. For example, in higher plants, plasmodesmata connect adjacent cells and allow communication to regulate differentiation and development. In animals, two main general structures that enable short- and long-range intercellular communication are known, namely gap junctions and tunneling nanotubes, respectively. Finally, filamentous fungi have also developed specialized structures called septal pores that allow intercellular communication via cytoplasmic flow. This review summarizes the underlying mechanisms for intercellular communication in these three eukaryotic groups and discusses its consequences for the regulation of differentiation and developmental processes.

  9. Characterizing pathways by which gravitropic effectors could move from the root cap to the root of primary roots of Zea mays

    Science.gov (United States)

    Moore, R.; McClelen, C. E.

    1989-01-01

    Plasmodesmata linking the root cap and root in primary roots Zea mays are restricted to approx. 400 protodermal cells bordering approx. 110000 microns2 of the calyptrogen of the root cap. This area is less than 10% of the cross-sectional area of the root-tip at the cap junction. Therefore, gravitropic effectors moving from the root cap to the root can move symplastically only through a relatively small area in the centre of the root. Decapped roots are non-responsive to gravity. However, decapped roots whose caps are replaced immediately after decapping are strongly graviresponsive. Thus, gravicurvature occurs only when the root cap contacts the root, and symplastic continuity between the cap and root is not required for gravicurvature. Completely removing mucilage from the root tip renders the root non-responsive to gravity. Taken together, these data suggest that gravitropic effectors move apoplastically through mucilage from the cap to the root.

  10. Ultracytochemical Localization and Functional Analysis of ATPase During the Endosperm Development in Oryza sativa L.

    Institute of Scientific and Technical Information of China (English)

    WEI Cun-xu; LAN Sheng-yin; XU Zhen-xiu

    2003-01-01

    Ultracytochemical localization of ATPase during development of rice endosperm was performed using a lead phosphate precipitation technique. The results indicated that, at the coenocyte and ceilularization stages, active ATPase was mainly distributed in an embryo sac wall, nucleus, and plasma membrane. At the early stage of development and differentiation, active ATPase was observed in the plasma membrane. At the grain filling stage, ATPase was highly active in the plasma membrane, intercellular space, and plasmodesmata in aleurone, moderately active on the plasma membrane in subaleurone. In starchy endosperm, ATPase was localized in the plasma membrane and degenerated nucleus. ATPase activity also appeared around vacuole and protein body in endosperm cell. The relationships between the ultracytochemical localization of ATPase and its function during the development of rice endosperm were discussed. Overall, ATPase was involved in the process of nutrition absorption and protein synthesis.

  11. Eduard Strasburger (1844-1912): founder of modern plant cell biology.

    Science.gov (United States)

    Volkmann, Dieter; Baluška, František; Menzel, Diedrik

    2012-10-01

    Eduard Strasburger, director of the Botany Institute and the Botanical Garden at the University of Bonn from 1881 to 1912, was one of the most admirable scientists in the field of plant biology, not just as the founder of modern plant cell biology but in addition as an excellent teacher who strongly believed in "education through science." He contributed to plant cell biology by discovering the discrete stages of karyokinesis and cytokinesis in algae and higher plants, describing cytoplasmic streaming in different systems, and reporting on the growth of the pollen tube into the embryo sac and guidance of the tube by synergides. Strasburger raised many problems which are hot spots in recent plant cell biology, e.g., structure and function of the plasmodesmata in relation to phloem loading (Strasburger cells) and signaling, mechanisms of cell plate formation, vesicle trafficking as a basis for most important developmental processes, and signaling related to fertilization.

  12. Micromorphology and ultrastructure of the floral nectaries of Viola odorata L. (Violaceae

    Directory of Open Access Journals (Sweden)

    Natalia Wiśniewska

    2015-05-01

    Full Text Available In Viola odorata two inferior anthers have connective appendages (nectaries projecting into the corolla spur. Nectaries are approx. 4 mm long, elongate, with the top of the nectary bending to the lateral wall of the spur. In the top part and in the abaxial surface of middle part of the nectary all cells have papillae. Nectar is secreted through the modified stomata distributed mainly in the top of nectary The nectary consists of single-layered epidermis, nectary parenchyma and subnectary parenchyma. Features of the nectary parenchyma cells, like dense cytoplasm containing numerous mitochondria and large nuclei, are connected with high metabolic cell activity. The vascularization includes both phloem and xylem. A slight amount of starch in the nectary cells, the profusion of plasmodesmata connecting secretory cells and the presence of vascular bundles suggest that sugars secreted in the nectar were delivered by the phloem sap.

  13. Membrane-Transport Systems for Sucrose in Relation to Whole-Plant Carbon Partitioning

    Institute of Scientific and Technical Information of China (English)

    Brian G. Ayre

    2011-01-01

    T Sucrose is the principal product of photosynthesis used for the distribution of assimilated carbon in plants. Transport mechanisms and efficiency influence photosynthetic productivity by relieving product inhibition and contribute to plant vigor by controlling source/sink relationships and biomass partitioning. Sucrose is synthesized in the cytoplasm and may move cell to cell through plasmodesmata or may cross membranes to be compartmentalized or exported to the apoplasm for uptake into adjacent cells. As a relatively large polar compound, sucrose requires proteins to facilitate efficient membrane transport. Transport across the tonoplast by facilitated diffusion, antiport with protons, and symport with protons have been proposed; for transport across plasma membranes, symport with protons and a mechanism resembling facilitated diffusion are evident. Despite decades of research, only symport with protons is well established at the molecular level. This review aims to integrate recent and older studies on sucrose flux across membranes with principles of whole-plant carbon partitioning.

  14. Ultrastructural observations reveal the presence of channels between cork cells.

    Science.gov (United States)

    Teixeira, Rita Teresa; Pereira, Helena

    2009-12-01

    The ultrastructure of phellem cells of Quercus suber L. (cork oak) and Calotropis procera (Ait) R. Br. were analyzed using electron transmission microscopy to determine the presence or absence of plasmodesmata (PD). Different types of Q. suber cork samples were studied: one year shoots; virgin cork (first periderm), reproduction cork (traumatic periderm), and wet cork. The channel structures of PD were found in all the samples crossing adjacent cell walls through the suberin layer of the secondary wall. Calotropis phellem also showed PD crossing the cell walls of adjacent cells but in fewer numbers compared to Q. suber. In one year stems of cork oak, it was possible to follow the physiologically active PD with ribosomic accumulation next to the aperture of the channel seen in the phellogen cells to the completely obstructed channels in the dead cells that characterize the phellem tissue.

  15. Mechanoreceptor Cells on the Tertiary Pulvini of Mimosa pudica L.

    Science.gov (United States)

    Visnovitz, Tamás; Világi, Ildikó; Varró, Petra; Kristóf, Zoltán

    2007-11-01

    Special red cells were found on the adaxial surface of tertiary pulvini of Mimosa pudica and experiments performed to determine the origin and function of these cells. Using anatomical (light, scanning electron and transmission electron microscopy) and electrophysiological techniques, we have demonstrated that these red cells are real mechanoreceptor cells. They can generate receptor potential following mechanical stimuli and they are in connection with excitable motor cells (through plasmodesmata). We also provide evidence that these red cells are derived from stomatal subsidiary cells and not guard cells. As histochemical studies show red cells contain tannin, which is important in development of action potentials and movements of plants. These cells could be one of unidentified mechanoreceptors of mimosa.

  16. Super-resolution imaging with Pontamine Fast Scarlet 4BS enables direct visualization of cellulose orientation and cell connection architecture in onion epidermis cells

    DEFF Research Database (Denmark)

    Liesche, Johannes; Ziomkiewicz, Iwona; Schulz, Alexander

    2013-01-01

    of cellulose fibril orientation and growth. The fluorescent dye Pontamine Fast Scarlet 4BS (PFS) was shown to stain cellulose with high specificity and could be used to visualize cellulose bundles in cell walls of Arabidopsis root epidermal cells with confocal microscopy. The resolution limit of confocal...... as alternatives 3D-structured illumination microscopy (3D-SIM) and confocal microscopy, combined with image deconvolution. Both methods offer lower resolution than STORM, but enable 3D imaging. While 3D-SIM produced strong artifacts, deconvolution gave good results. The resolution was improved over conventional...... confocal microscopy and the approach could be used to demonstrate differences in fibril orientation in different layers of the cell wall as well as particular cellulose fortifications around plasmodesmata. Conclusions Super-resolution light microscopy of PFS-stained cellulose fibrils is possible...

  17. 黄瓜韧皮部的类血影蛋白%Spectrin-like Protein in the Phloem of Cucumis sativus

    Institute of Scientific and Technical Information of China (English)

    邢立静; 花宝光; 娄成后

    2002-01-01

    Spectrin-like protein has been found in a variety of plant cells. In this study, electron microscopic observation of immuno-gold labelled preparations from the leaf petiole of cucumber (Cucumis sativus L.) shows that it also exists in the sieve element-companion cell (SE-CC) complex, being widely distributed in P-protein filaments and sieve element reticulum (SER), in the cytoplasm and mitochondrial membrane of companion cell (CC) and in the branched plasmodesmata between sieve element (SE) and CC as well. The results suggest that this protein could be synthesized in CC and transferred to SE through plasmodesmata. Western blotting showed that spectrin-like protein existed in the protein of phloem exudate of cucumber, and its molecular weight was about 260 kD.%以黄瓜(Cucumis sativus L.)叶柄为实验材料,应用胶体金免疫电镜技术证明类血影蛋白存在于韧皮部的筛管-伴胞复合体中,广泛分布于筛分子中的韧皮蛋白纤丝以及筛分子网络结构上,并且分布在伴胞的细胞质和线粒体膜以及筛分子与伴胞之间的分支状胞间连丝上,表明该蛋白可能由伴胞合成并经由二者之间的胞间连丝运输到筛分子中.用免疫印迹技术证明,黄瓜韧皮部汁液蛋白中存在类血影蛋白,其分子量约为260 kD,与动物细胞中血影蛋白的分子量接近.

  18. Phloem long-distance delivery of FLOWERING LOCUS T (FT) to the apex.

    Science.gov (United States)

    Yoo, Soo-Cheul; Chen, Cheng; Rojas, Maria; Daimon, Yasufumi; Ham, Byung-Kook; Araki, Takashi; Lucas, William J

    2013-08-01

    Cucurbita moschata FLOWERING LOCUS T-LIKE 2 (hereafter FTL2) and Arabidopsis thaliana (Arabidopsis) FLOWERING LOCUS T (FT), components of the plant florigenic signaling system, move long-distance through the phloem from source leaves to the vegetative apex where they mediate floral induction. The mechanisms involved in long-distance trafficking of FT/FTL2 remain to be elucidated. In this study, we identified the critical motifs on both FT and FTL2 required for cell-to-cell trafficking through mutant analyses using a zucchini yellow mosaic virus expression vector. Western blot analysis, performed on phloem sap collected from just beneath the vegetative apex of C. moschata plants, established that all mutant proteins tested retained the ability to enter the phloem translocation stream. However, immunolocalization studies revealed that a number of these FTL2/FT mutants were defective in the post-phloem zone, suggesting that a regulation mechanism for FT trafficking exists in the post-phloem unloading step. The selective movements of FT/FTL2 were further observed by microinjection and trichome rescue studies, which revealed that FT/FTL2 has the ability to dilate plasmodesmata microchannels during the process of cell-to-cell trafficking, and various mutants were compromised in their capacity to traffic through plasmodesmata. Based on these findings, a model is presented to account for the mechanism by which FT/FTL2 enters the phloem translocation stream and subsequently exits the phloem and enters the apical tissue, where it initiates the vegetative to floral transition.

  19. A xylem sap retrieval pathway in rice leaf blades: evidence of a role for endocytosis?

    Science.gov (United States)

    Botha, C E J; Aoki, N; Scofield, G N; Liu, L; Furbank, R T; White, R G

    2008-01-01

    The structure and transport properties of pit membranes at the interface between the metaxylem and xylem parenchyma cells and the possible role of these pit membranes in solute transfer to the phloem were investigated. Electron microscopy revealed a fibrillar, almost tubular matrix within the pit membrane structure between the xylem vessels and xylem parenchyma of leaf blade bundles in rice (Oryza sativa). These pits are involved primarily with regulating water flux to the surrounding xylem parenchyma cells. Vascular parenchyma cells contain large mitochondrial populations, numerous dictyosomes, endomembrane complexes, and vesicles in close proximity to the pit membrane. Taken collectively, this suggests that endocytosis may occur at this interface. A weak solution of 5,6-carboxyfluorescein diacetate (5,6-CFDA) was applied to cut ends of leaves and, after a minimum of 30 min, the distribution of the fluorescent cleavage product, 5,6-carboxyfluorescein (5,6-CF), was observed using confocal microscopy. Cleavage of 5,6-CFDA occurred within the xylem parenchyma cells, and the non-polar 5,6-CF was then symplasmically transported to other parenchyma elements and ultimately, via numerous pore plasmodesmata, to adjacent thick-walled sieve tubes. Application of Lucifer Yellow, and, separately, Texas Red-labelled dextran (10 kDa) to the transpiration stream, confirmed that these membrane-impermeant probes could only have been offloaded from the xylem via the xylem vessel-xylem parenchyma pit membranes, suggesting endocytotic transmembrane transfer of these membrane-impermeant fluorophores. Accumulation within the thick-walled sieve tubes, but not in thin-walled sieve tubes, confirms the presence of a symplasmic phloem loading pathway, via pore plasmodesmata between xylem parenchyma and thick-walled sieve tubes, but not thin-walled sieve tubes.

  20. A protein kinase binds the C-terminal domain of the readthrough protein of Turnip yellows virus and regulates virus accumulation

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez-Medina, Caren; Boissinot, Sylvaine [UMR 1131 SVQV INRA-UDS, 28 rue de Herrlisheim, 68021 Colmar (France); Chapuis, Sophie [Institut de Biologie Moléculaire des Plantes, Laboratoire propre du CNRS conventionné avec l’Université de Strasbourg, 12 rue du Général Zimmer, 67084 Strasbourg (France); Gereige, Dalya; Rastegar, Maryam; Erdinger, Monique [UMR 1131 SVQV INRA-UDS, 28 rue de Herrlisheim, 68021 Colmar (France); Revers, Frédéric [INRA, Université de Bordeaux, UMR 1332 de Biologie du Fruit et Pathologie, 33882 Villenave d’Ornon (France); Ziegler-Graff, Véronique [Institut de Biologie Moléculaire des Plantes, Laboratoire propre du CNRS conventionné avec l’Université de Strasbourg, 12 rue du Général Zimmer, 67084 Strasbourg (France); Brault, Véronique, E-mail: veronique.brault@colmar.inra.fr [UMR 1131 SVQV INRA-UDS, 28 rue de Herrlisheim, 68021 Colmar (France)

    2015-12-15

    Turnip yellows virus (TuYV), a phloem-limited virus, encodes a 74 kDa protein known as the readthrough protein (RT) involved in virus movement. We show here that a TuYV mutant deleted of the C-terminal part of the RT protein (TuYV-∆RT{sub Cter}) was affected in long-distance trafficking in a host-specific manner. By using the C-terminal domain of the RT protein as a bait in a yeast two-hybrid screen of a phloem cDNA library from Arabidopsis thaliana we identified the calcineurin B-like protein-interacting protein kinase-7 (AtCIPK7). Transient expression of a GFP:CIPK7 fusion protein in virus-inoculated Nicotiana benthamiana leaves led to local increase of wild-type TuYV accumulation, but not that of TuYV-∆RT{sub Cter}. Surprisingly, elevated virus titer in inoculated leaves did not result in higher TuYV accumulation in systemic leaves, which indicates that virus long-distance movement was not affected. Since GFP:CIPK7 was localized in or near plasmodesmata, CIPK7 could negatively regulate TuYV export from infected cells. - Highlights: • The C-terminal domain of TuYV-RT is required for long-distance movement. • CIPK7 from Arabidopsis interacts with RT{sub Cter} in yeast and in plants. • CIPK7 overexpression increases virus titer locally but not virus systemic movement. • CIPK7 localizes to plasmodesmata. • CIPK7 could be a defense protein regulating virus export.

  1. Subcellular localization and functional domain studies of DEFECTIVE KERNEL1 in maize and Arabidopsis suggest a model for aleurone cell fate specification involving CRINKLY4 and SUPERNUMERARY ALEURONE LAYER1.

    Science.gov (United States)

    Tian, Qing; Olsen, Lene; Sun, Beimeng; Lid, Stein Erik; Brown, Roy C; Lemmon, Betty E; Fosnes, Kjetil; Gruis, Darren Fred; Opsahl-Sorteberg, Hilde-Gunn; Otegui, Marisa S; Olsen, Odd-Arne

    2007-10-01

    DEFECTIVE KERNEL1 (DEK1), which consists of a membrane-spanning region (DEK1-MEM) and a calpain-like Cys proteinase region (DEK1-CALP), is essential for aleurone cell formation at the surface of maize (Zea mays) endosperm. Immunolocalization and FM4-64 dye incubation experiments showed that DEK1 and CRINKLY4 (CR4), a receptor kinase implicated in aleurone cell fate specification, colocalized to plasma membrane and endosomes. SUPERNUMERARY ALEURONE LAYER1 (SAL1), a negative regulator of aleurone cell fate encoding a class E vacuolar sorting protein, colocalized with DEK1 and CR4 in endosomes. Immunogold localization, dual-axis electron tomography, and diffusion of fluorescent dye tracers showed that young aleurone cells established symplastic subdomains through plasmodesmata of larger dimensions than those connecting starchy endosperm cells and that CR4 preferentially associated with plasmodesmata between aleurone cells. Genetic complementation experiments showed that DEK1-CALP failed to restore wild-type phenotypes in maize and Arabidopsis thaliana dek1 mutants, and DEK1-MEM also failed to restore wild-type phenotypes in Arabidopsis dek1-1 mutants. Instead, ectopic expression of DEK1-MEM under the control of the cauliflower mosaic virus 35S promoter gave a dominant negative phenotype. These data suggest a model for aleurone cell fate specification in which DEK1 perceives and/or transmits a positional signal, CR4 promotes the lateral movement of aleurone signaling molecules between aleurone cells, and SAL1 maintains the proper plasma membrane concentration of DEK1 and CR4 proteins via endosome-mediated recycling/degradation.

  2. Intracellular distribution, cell-to-cell trafficking and tubule-inducing activity of the 50 kDa movement protein of Apple chlorotic leaf spot virus fused to green fluorescent protein.

    Science.gov (United States)

    Satoh, H; Matsuda, H; Kawamura, T; Isogai, M; Yoshikawa, N; Takahashi, T

    2000-08-01

    The 50 kDa protein (50KP) encoded by ORF2 of Apple chlorotic leaf spot virus (ACLSV) fused to green fluorescent protein (GFP) was expressed transiently in cells of Nicotiana occidentalis and Chenopodium quinoa leaves. Its intracellular distribution, cell-to-cell trafficking in leaf epidermis and tubule formation on the surface of protoplasts were analysed. The 50KP-GFP fluorescence was distributed as small irregular spots or a fibrous network structure on the periphery of epidermal cells and protoplasts of both plant species. In leaf epidermis of N. occidentalis, the protein spread from the cells that produced it into neighbouring cells in both young and mature leaves and targetted plasmodesmata in these cells. In contrast, GFP was restricted to single cells in most cases in mature leaves. When 50KP and GFP were co-expressed in leaf epidermis of N. occidentalis, GFP spread more widely from the initial cells that produced it than when GFP was expressed alone, suggesting that 50KP facilitated the cell-to-cell trafficking of GFP. 50KP-GFP was able to complement local spread of 50KP-deficient virus when expressed transiently in leaf epidermis of C. quinoa. Expression of 50KP-GFP in protoplasts resulted in the production of tubular structures protruding from the surface. Mutational analyses showed that the C-terminal region (aa 287-457) was not essential for localization to plasmodesmata, cell-to-cell trafficking, complementation of movement of 50KP-deficient virus or tubule formation on protoplasts. In contrast, deletions in the N-terminal region resulted in the complete disruption of all these activities.

  3. 鹤顶兰胚囊发育的超微结构观察%Ultrastructural Observation on Embryo Sac Development in Phaius tankervilliae (Aiton) BI.

    Institute of Scientific and Technical Information of China (English)

    李冬妹; 伍成厚; 叶秀粦; 梁承邺

    2012-01-01

    Embryo sac development in Phaius tankervilliae (Aiton) Bl. Was observed under transmission electron microscope. Three phases of functional megaspore and two phases of mature embryo sac were captured in this study. At the functional megaspore and 4-nucleate embryo sac stages, plasmodesmata were present between nucellar cells and embryo sac at the chalazal end. Plasmodesmata are cellular communicating junctions that link adjacent cells to form symplast of a plant. They provide a direct channel for material transport and signal transduction,therefore megagametogenesis is not at an absolutely insulated situation. A big vacuole was observed at the early stage of functional megaspore before it disappeared during the first mitotic division. However,many small vacuoles appeared at the interspaces of separating chromosomes. Distinct vacuoles were also observed in the synergid cells and egg cell during the early stage of mature embryo sac,but vanished when synergid cells degenerated. The change of vacuoles probably resulted from the cell physiological change. Our results may provide insights into reproductive biology of Phaius tankervilliae.%运用电子显微镜技术对鹤顶兰(Phaius tankervilliae(Aiton)BI.)胚囊发育过程中功能大孢子、二核胚囊、四核胚囊、成熟胚囊的超微结构进行观察,捕捉到了功能大孢子的三个阶段、成熟胚囊的两个阶段,进一步积累了鹤顶兰生殖生物学研究的基础资料.在功能大孢子、四核胚囊时期的合点端壁上可观察到胞间连丝,与体细胞间有物质及信息的交换,胚囊发育并非处于完全“隔离”状态.功能大孢子早期可见明显大液泡,随后进入第一次有丝分裂时大液泡消失,移向两极的染色体之间可见大量体积较小的液泡,成熟胚囊前期助细胞及卵细胞内也可见明显液泡,但当助细胞解体时,卵细胞内的大液泡也消失,液泡形态的变化可能是细胞生理状态发生改变的结果.

  4. TYLCV-Is movement in planta does not require V2 protein

    Energy Technology Data Exchange (ETDEWEB)

    Hak, Hagit [Institute of Plant Sciences, Agricultural Research Organization, The Volcani Center, Bet Dagan (Israel); Department of Biological Chemistry, The Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem (Israel); Levy, Yael; Chandran, Sam A.; Belausov, Eduard [Institute of Plant Sciences, Agricultural Research Organization, The Volcani Center, Bet Dagan (Israel); Loyter, Abraham [Department of Biological Chemistry, The Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem (Israel); Lapidot, Moshe [Institute of Plant Sciences, Agricultural Research Organization, The Volcani Center, Bet Dagan (Israel); Gafni, Yedidya, E-mail: ygafni@volcani.agri.gov.il [Institute of Plant Sciences, Agricultural Research Organization, The Volcani Center, Bet Dagan (Israel)

    2015-03-15

    Tomato yellow leaf curl virus (TYLCV), a major tomato pathogen causing extensive crop losses, is a whitefly-transmitted geminivirus. V2 mutants of TYLCV-Is and related viruses tend to induce symptomless infection with attenuated viral DNA levels, while accumulating close to wild-type DNA levels in protoplasts, suggesting V2 as a movement protein. The discovery of plant-silencing mechanisms and viral silencing suppressors, V2 included, led us to reconsider V2's involvement in viral movement. We studied two mutant versions of the virus, one impaired in V2 silencing-suppression activity, and another carrying a non-translatable V2. While both mutant viruses spread in the infected plant to newly emerged leaves at the same rate as the wild-type virus, their DNA-accumulation levels were tenfold lower than in the wild-type virus. Thus, we suggest that the setback in virus proliferation, previously ascribed to a movement impediment, is due to lack of silencing-suppression activity. - Highlights: • TYLCV-Is V2 protein is localized in distinct microbodies throughout the cell cytoplasm, around the nucleus and in association with cytoplasmic strands but is not associated with the plasmodesmata. • Disruption of RNA-silencing suppression activity of TYLCV-Is V2 protein causes low titer of the virus in the infected plants. • The movement of TYLCV-Is in planta does not require a functional V2 protein.

  5. Exploring the role of lipids in intercellular conduits: breakthroughs in the pipeline

    Directory of Open Access Journals (Sweden)

    Elise eDelage

    2013-12-01

    Full Text Available It has been known for more than a century that most of the plant cells are connected to their neighbors through membranous pores perforating the cell wall, namely plasmodesmata (PDs. The recent discovery of tunneling nanotubes (TNTs, thin membrane bridges established between distant mammalian cells, suggests that intercellular communication mediated through cytoplasmic continuity could be a conserved feature of eukaryotic organisms. Although TNTs differ from PDs in their formation and architecture, both are characterized by a continuity of the plasma membrane between two cells, delimiting a nanotubular channel supported by actin-based cytoskeleton. Due to this unusual membrane organization, lipids are likely to play critical roles in the formation and stability of intercellular conduits like TNTs and PDs, but also in regulating the transfer through these structures. While it is crucial for a better understanding of those fascinating communication highways, the study of TNT lipid composition and dynamics turned out to be extremely challenging. The present review aims to give an overview of the recent findings in this context. We will also discuss some of the promising imaging approaches, which might be the key for future breakthroughs in the field and could also benefit the research on PDs.

  6. The paraveinal mesophyll of soybean leaves in relation to assimilate transfer and compartmentation : I. Ultrastructure and histochemistry during vegetative development.

    Science.gov (United States)

    Franceschi, V R; Giaquinta, R T

    1983-04-01

    The paraveinal mesophyll (PVM) is a unique and specialized, one-cell-thick tissue spanning the vascular bundles at the level of the phloem in soybean (Glycine max) (L.) Merr.) leaves. Its position within the leaf dictates that all photosynthate produced in the palisade and spongy mesophyll must pass through this specialized layer enroute to the phloem. Symplastic continuity, via plasmodesmata, exists between the PVM and bundle sheath, palisade parenchyma and spongy mesophyll. During leaf ontogeny the PVM is the first tissue to differentiate and at maturity these cells are six to eight times larger than other mesophyll cells, are highly vacuolate, and are interconnected by tubular arms. The PVM undergoes several unique structural and metabolic modifications during leaf development. The PVM cytoplasm, in vegetative plants, is dense, enriched in rough endoplasmic reticulum and dictyosomes, but contains few, small starch-free chloroplasts and few microbodies. Unlike the tonoplast of mesophyll cells, the tonoplast of the PVM is unusually thick and dense-staining. During leaf development the vacuoles of PVM cells accumulate a glycoprotein derived from the dictyosomes which reacts with the protein staining reagents, mercuric bromophenol blue and sulfaflavine, and is degraded by Pronase. Both the vacuolar material and tonoplast are also stained by phosphotungstic acid, which at low pH is relatively selective for glycoprotein. A unique role of the PVM in the transport and compartmentation of nitrogen reserves in soybeans is discussed.

  7. Ultrastructural Alteration of Maize Plants Infected with the Maize Rough Dwarf Virus

    Institute of Scientific and Technical Information of China (English)

    LI Zhao-hui; GUO Xing-qi; YE Bao-hua; GUO Yan-kui

    2002-01-01

    The ultrastruetural alteration of maize plants infected with the maize rough dwarf virus (MRDV) was studied with transmission electron microscopy. The results revealed that aggregates of virus particles, with a diameter of 60nm, were found in the root cell, and always distributed near the vacuole membrane. However, no such particles were checked in leaf cells. Moreover, no virus was observed in choroplasts,mitochondria nuclei, plasmodesmata or intercellular canal of all kinds of infected cells of maize, either.Structures of various organelles changed in the infected leaf and root cells of maize. An inward collapse and localized splitting of the tonoplast were observed, the chloropoast structure was destroyed by MRDV, and the number of destroyed or dysplasia chloroplast in leaf cells with serious symptoms was more than that in leaves without symptoms. The matrix of mitochondria in cells infected by MRDV decreased and some of them expanded and destructed. Nuclei was abnormal and the nuclear membrane was broken, In addition, the infected cells were characterized by a voluminous cytoplasm containing hypertrophied endoplasmic reticulum, with rich ribosome content and lots of starch grain.

  8. Tomato leaf spatial expression of stress-induced Asr genes.

    Science.gov (United States)

    Maskin, Laura; Maldonado, Sara; Iusem, Norberto D

    2008-12-01

    Asr1 and Asr2 are water stress-inducible genes belonging to the Asr gene family, which transcriptionally regulate a sugar transporter gene, at least in grape. Using an in situ RNA hybridization methodology, we determined that, in basal conditions, expression of Asr2 in tomato leaves is detected in the phloem tissue, particularly in companion phloem cells. When plants are exposed to water stress, Asr2 expression is contained in companion cells but expands occasionally to mesophyll cells. In contrast, Asr1 transcript localization seems to be sparse in leaf vascular tissue under both non-stress and stress conditions. The occurrence of Asr transcripts precisely in companion cells is in accordance with the cell type specificity reported for hexose-transporter protein molecules in grape encoded by the only Asr-target gene known to date. The results are discussed in light of the reported scarcity of plasmodesmata between companion cells and the rest of leaf tissue in the family Solanaceae.

  9. A New Subfamily of Sucrose Transporters, SUT4, with Low Affinity/High Capacity Localized in Enucleate Sieve Elements of Plants

    Science.gov (United States)

    Weise, Andreas; Barker, Laurence; Kühn, Christina; Lalonde, Sylvie; Buschmann, Henrik; Frommer, Wolf B.; Ward, John M.

    2000-01-01

    A new subfamily of sucrose transporters from Arabidopsis (AtSUT4), tomato (LeSUT4), and potato (StSUT4) was isolated, demonstrating only 47% similarity to the previously characterized SUT1. SUT4 from two plant species conferred sucrose uptake activity when expressed in yeast. The Km for sucrose uptake by AtSUT4 of 11.6 ± 0.6 mM was ∼10-fold greater than for all other plant sucrose transporters characterized to date. An ortholog from potato had similar kinetic properties. Thus, SUT4 corresponds to the low-affinity/high-capacity saturable component of sucrose uptake found in leaves. In contrast to SUT1, SUT4 is expressed predominantly in minor veins in source leaves, where high-capacity sucrose transport is needed for phloem loading. In potato and tomato, SUT4 was immunolocalized specifically to enucleate sieve elements, indicating that like SUT1, macromolecular trafficking is required to transport the mRNA or the protein from companion cells through plasmodesmata into the sieve elements. PMID:10948254

  10. Potential involvement of a cucumber homolog of phloem protein 1 in the long-distance movement of Cucumber mosaic virus particles.

    Science.gov (United States)

    Requena, A; Simón-Buela, L; Salcedo, G; García-Arenal, F

    2006-07-01

    The systemic movement of Cucumber mosaic virus (CMV) in cucumber plants was analyzed. The structure that is translocated and its putative interactions with phloem components were analyzed in phloem exudate (PE) samples, which reflect sieve tubes stream composition. Rate zonal centrifugation and electron-microscopy analyses of PE from CMV-infected plants showed that CMV moves through sieve tubes as virus particles. Gel overlay assays revealed that CMV particles interact with a PE protein, p48. The amino-acid sequence of several tryptic peptides of p48 was determined. Partial amino-acid sequence of p48 showed it was a cucumber homolog of phloem protein 1 (PP1) from pumpkin, with which p48 also shares several chemical properties. PP1 from pumpkin has plasmodesmata-gating ability and translocates in sieve tubes. Encapsidated CMV RNA in PE samples from infected plants was less accessible to digestion by RNase A than RNA in purified CMV particles, a property that was reconstituted by the in vitro interaction of purified CMV particles and protein p48. These results indicate that the interaction with p48 modifies CMV particle structure and suggest that CMV particles interact with the cucumber homolog of PP1 during translocation in the sieve tubes.

  11. Intracellular Transport of Plant Viruses: Finding the Door out of the Cell

    Institute of Scientific and Technical Information of China (English)

    James E. Schoelz; Phillip A. Harries; Richard S. Nelson

    2011-01-01

    Plant viruses are a class of plant pathogens that specialize in movement from cell to cell.As part of their arsenal for infection of plants,every virus encodes a movement protein (MP),a protein dedicated to enlarging the pore size of plasmodesmata (PD) and actively transporting the viral nucleic acid into the adjacent cell.As our knowledge of intercellular transport has increased,it has become apparent that viruses must also use an active mechanism to target the virus from their site of replication within the cell to the PD.Just as viruses are too large to fit through an unmodified plasmodesma,they are also too large to be freely diffused through the cytoplasm of the cell.Evidence has accumulated now for the involvement of other categories of viral proteins in intracellular movement in addition to the MP,including viral proteins originally associated with replication or gene expression.In this review,we will discuss the strategies that viruses use for intracellular movement from the replication site to the PD,in particular focusing on the role of host membranes for intracellular transport and the coordinated interactions between virus proteins within cells that are necessary for successful virus spread.

  12. A family of plasmodesmal proteins with receptor-like properties for plant viral movement proteins.

    Science.gov (United States)

    Amari, Khalid; Boutant, Emmanuel; Hofmann, Christina; Schmitt-Keichinger, Corinne; Fernandez-Calvino, Lourdes; Didier, Pascal; Lerich, Alexander; Mutterer, Jérome; Thomas, Carole L; Heinlein, Manfred; Mély, Yves; Maule, Andrew J; Ritzenthaler, Christophe

    2010-09-23

    Plasmodesmata (PD) are essential but poorly understood structures in plant cell walls that provide symplastic continuity and intercellular communication pathways between adjacent cells and thus play fundamental roles in development and pathogenesis. Viruses encode movement proteins (MPs) that modify these tightly regulated pores to facilitate their spread from cell to cell. The most striking of these modifications is observed for groups of viruses whose MPs form tubules that assemble in PDs and through which virions are transported to neighbouring cells. The nature of the molecular interactions between viral MPs and PD components and their role in viral movement has remained essentially unknown. Here, we show that the family of PD-located proteins (PDLPs) promotes the movement of viruses that use tubule-guided movement by interacting redundantly with tubule-forming MPs within PDs. Genetic disruption of this interaction leads to reduced tubule formation, delayed infection and attenuated symptoms. Our results implicate PDLPs as PD proteins with receptor-like properties involved the assembly of viral MPs into tubules to promote viral movement.

  13. Citrus leaf blotch virus invades meristematic regions in Nicotiana benthamiana and citrus.

    Science.gov (United States)

    Agüero, Jesús; Vives, María Carmen; Velázquez, Karelia; Ruiz-Ruiz, Susana; Juárez, Jose; Navarro, Luis; Moreno, Pedro; Guerri, José

    2013-08-01

    To invade systemically host plants, viruses need to replicate in the infected cells, spread to neighbouring cells through plasmodesmata and move to distal parts of the plant via sieve tubes to start new infection foci. To monitor the infection of Nicotiana benthamiana plants by Citrus leaf blotch virus (CLBV), leaves were agroinoculated with an infectious cDNA clone of the CLBV genomic RNA expressing green fluorescent protein (GFP) under the transcriptional control of a duplicate promoter of the coat protein subgenomic RNA. Fluorescent spots first appeared in agroinfiltrated leaves 11-12 days after infiltration, indicating CLBV replication. Then, after entering the phloem vascular system, CLBV was unloaded in the upper parts of the plant and invaded all tissues, including flower organs and meristems. GFP fluorescence was not visible in citrus plants infected with CLBV-GFP. Therefore, to detect CLBV in meristematic regions, Mexican lime (Citrus aurantifolia) plants were graft inoculated with CLBV, with Citrus tristeza virus (CTV), a virus readily eliminated by shoot-tip grafting in vitro, or with both simultaneously. Although CLBV was detected by hybridization and real-time reverse transcription-polymerase chain reaction (RT-PCR) in 0.2-mm shoot tips in all CLBV-inoculated plants, CTV was not detected. These results explain the difficulty in eliminating CLBV by shoot-tip grafting in vitro. © 2013 BSPP AND JOHN WILEY & SONS LTD.

  14. Mobile gene silencing in Arabidopsis is regulated by hydrogen peroxide

    Directory of Open Access Journals (Sweden)

    Dacheng Liang

    2014-12-01

    Full Text Available In plants and nematodes, RNAi can spread from cells from which it is initiated to other cells in the organism. The underlying mechanism controlling the mobility of RNAi signals is not known, especially in the case of plants. A genetic screen designed to recover plants impaired in the movement but not the production or effectiveness of the RNAi signal identified RCI3, which encodes a hydrogen peroxide (H2O2-producing type III peroxidase, as a key regulator of silencing mobility in Arabidopsis thaliana. Silencing initiated in the roots of rci3 plants failed to spread into leaf tissue or floral tissue. Application of exogenous H2O2 reinstated the spread in rci3 plants and accelerated it in wild-type plants. The addition of catalase or MnO2, which breaks down H2O2, slowed the spread of silencing in wild-type plants. We propose that endogenous H2O2, under the control of peroxidases, regulates the spread of gene silencing by altering plasmodesmata permeability through remodelling of local cell wall structure, and may play a role in regulating systemic viral defence.

  15. Symplastic domains in the Arabidopsis shoot apical meristem correlate with PDLP1 expression patterns

    Science.gov (United States)

    Bayer, Emmanuelle; Thomas, Carole

    2008-01-01

    Symplastic domains in plants are defined by spatial limitations on cell-to-cell communication through plasmodesmata (Pds) and establish tissue boundaries necessary for metabolic and developmental programming. With the exception of the physical closure of Pds by callose, the cues and the processes for creating symplastic domains remain poorly understood. Recently, we identified a novel family of eight proteins, called Pd-located protein 1 (PDLP1). These proteins span the plasma membrane within Pds and likely form part of a signal transduction system that perceives external signals to regulate molecular trafficking between cells. For two members of this family that have high expression in the shoot apex we show that they have defined and partially overlapping tissue-specific expression patterns that correlate in part with previously defined symplastic domains. The importance of non-cell-autonomous proteins in shoot development and of the spatial rules that govern leaf and floral development highlight the need to have a clearer understanding of symplastic domains. PMID:19704520

  16. Downregulation of the NbNACa1 gene encoding a movement-protein-interacting protein reduces cell-to-cell movement of Brome mosaic virus in Nicotiana benthamiana.

    Science.gov (United States)

    Kaido, Masanori; Inoue, Yosuke; Takeda, Yoshika; Sugiyama, Kazuhiko; Takeda, Atsushi; Mori, Masashi; Tamai, Atsushi; Meshi, Tetsuo; Okuno, Tetsuro; Mise, Kazuyuki

    2007-06-01

    The 3a movement protein (MP) plays a central role in the movement of the RNA plant virus, Brome mosaic virus (BMV). To identify host factor genes involved in viral movement, a cDNA library of Nicotiana benthamiana, a systemic host for BMV, was screened with far-Western blotting using a recombinant BMV MP as probe. One positive clone encoded a protein with sequence similarity to the alpha chain of nascent-polypeptide-associated complex from various organisms, which is proposed to contribute to the fidelity of translocation of newly synthesized proteins. The orthologous gene from N. benthamiana was designated NbNACa1. The binding of NbNACa1 to BMV MP was confirmed in vivo with an agroinfiltration-immunoprecipitation assay. To investigate the involvement of NbNACa1 in BMV multiplication, NbNACa1-silenced (GSNAC) transgenic N. benthamiana plants were produced. Downregulation of NbNACa1 expression reduced virus accumulation in inoculated leaves but not in protoplasts. A microprojectile bombardment assay to monitor BMV-MP-assisted viral movement demonstrated reduced virus spread in GSNAC plants. The localization to the cell wall of BMV MP fused to green fluorescent protein was delayed in GSNAC plants. From these results, we propose that NbNACa1 is involved in BMV cell-to-cell movement through the regulation of BMV MP localization to the plasmodesmata.

  17. Cytological investigations of mesophyll of Phaseolus vulgaris L. 'Red Kidney' infected with PVS

    Directory of Open Access Journals (Sweden)

    Krystyna Brzezicka-Szymczyk

    2013-12-01

    Full Text Available We have put under cytological observation 2-, 4-, and 8-day fragments of mesophyll of the leaves Phaseolus 'Red Kidney' infected with PVS. In the necrosis caused by PVS can be distinguished a necrotic centre, a seminecrotic zone, and a belt of terminal cells. The necrotic centre is the most changed area whose cells are most often decayed. In the seminecrotic zone, the presence of viruses in the cell causes some pathological changes. The ER canals assume the shape of swollen cisterns. The chloroplasts reacts with the softening of granas, the growth of starch granules and plastoglobules content as well as with the presence of proteinaceous fibrous structures. The karyolymph and mitochondrium matrix become elucidated. The continuity of plasmalemma and tonoplast become interrupted. Virus particles appear in the area of cytoplasm of seminecrotic zone and in the necrotic centre, they are dispersed or rarely arranged in aggregations which often are in contact with tonoplast. We have observed virus packs enclosed with lipoproteid membrane. Viruses were not stated in the terminal zone. We have ascertained the intensive development of cell walls in the cells of terminal and seminecrotic zones. A lobar or punctual way of the development appeared in different areas of the cell wall and was found independently in various cells. The modified areas included as well plasmodesmata. The above observations enable us to presume that the cells of necrotic centre and seminecrotic zone are the place of replication and assembling of viruses and is responsible for the mechanical localization of virus infection.

  18. The mechanism by which an asymmetric distribution of plant growth hormone is attained

    Science.gov (United States)

    Bandurski, Robert S.; Schulze, Aga; Jensen, Philip; Desrosiers, Mark; Epel, Bernard; Kowalczyk, Stanley

    Zea mays (sweet corn) seedlings attain an asymmetric distribution of the growth hormone indole-3-acetic acid (IAA) within 3 minutes following a gravity stimulus. Both free and esterified IAA (that is total IAA) accumulate to a greater extent in the lower half of the mesocotyl cortex of a horizontally placed seedling than in the upper half. Thus, changes in the ratio of free IAA to ester IAA cannot account for the asymmetric distribution. Our studies demonstrate there is no de novo synthesis of IAA in young seedlings. We conclude that asymmetric IAA distribution is attained by a gravity-induced, potential-regulated gating of the movement of IAA from kernel to shoot and from stele to cortex. As a working theory, which we call the Potential Gating Theory, we propose that perturbation of the plant's bioelectric field, induced by gravity, causes opening and closing of transport channels in the plasmodesmata connecting the vascular stele to the surrounding cortical tissues. This results in asymmetric growth hormone distribution which results in the asymmetric growth characteristic of the gravitropic response.

  19. Phytotoxicity, accumulation and transport of silver nanoparticles by Arabidopsis thaliana.

    Science.gov (United States)

    Geisler-Lee, Jane; Wang, Qiang; Yao, Ying; Zhang, Wen; Geisler, Matt; Li, Kungang; Huang, Ying; Chen, Yongsheng; Kolmakov, Andrei; Ma, Xingmao

    2013-05-01

    The widespread availability of nano-enabled products in the global market may lead to the release of a substantial amount of engineered nanoparticles in the environment, which frequently display drastically different physiochemical properties than their bulk counterparts. The purpose of the study was to evaluate the impact of citrate-stabilised silver nanoparticles (AgNPs) on the plant Arabidopsis thaliana at three levels, physiological phytotoxicity, cellular accumulation and subcellular transport of AgNPs. The monodisperse AgNPs of three different sizes (20, 40 and 80 nm) aggregated into much larger sizes after mixing with quarter-strength Hoagland solution and became polydisperse. Immersion in AgNP suspension inhibited seedling root elongation and demonstrated a linear dose-response relationship within the tested concentration range. The phytotoxic effect of AgNPs could not be fully explained by the released silver ions. Plants exposed to AgNP suspensions bioaccumulated higher silver content than plants exposed to AgNO3 solutions (Ag(+) representative), indicating AgNP uptake by plants. AgNP toxicity was size and concentration dependent. AgNPs accumulated progressively in this sequence: border cells, root cap, columella and columella initials. AgNPs were apoplastically transported in the cell wall and found aggregated at plasmodesmata. In all the three levels studied, AgNP impacts differed from equivalent dosages of AgNO3.

  20. Role of Rice stripe virus NSvc4 in cell-to-cell movement and symptom development in Nicotiana benthamiana

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    Yi eXu

    2012-12-01

    Full Text Available Our previous work has demonstrated that the NSvc4 protein of Rice stripe virus (RSV functions as a cell-to-cell movement protein. However, the mechanisms whereby RSV traffics through plasmodesmata (PD are unknown. Here we provide evidence that the NSvc4 moves on the actin filament and endoplasmic reticulum (ER network, but not microtubules, to reach cell wall PD. Disruption of cytoskeleton using different inhibitors altered NSvc4 localization to PD, thus impeding RSV infection of Nicotiana benthamiana. Sequence analyses and deletion mutagenesis experiment revealed that the N-terminal 125 amino acids (AAs of the NSvc4 determine PD targeting and that a transmembrane domain spanning AAs 106 to 125 is critical for PD localization. We also found that the NSvc4 protein can localize to chloroplasts in infected cells. Analyses using deletion mutants revealed that the N-terminal 73 AAs are essential for chloroplast localization. Furthermore, expression of NSvc4 from a Potato virus X (PVX vector resulted in more severe disease symptoms than PVX alone in systemically infected N. benthamiana leaves. Expression of NSvc4 in Spodoptera frugiperda 9 (Sf-9 cells did not elicit tubule formation, but instead resulted in punctate foci at the plasma membrane. These findings shed new light on our understanding of the movement mechanisms whereby RSV infects host plants.

  1. Two basic (hydrophilic) regions in the movement protein of Parietaria mottle virus have RNA binding activity and are required for cell-to-cell transport.

    Science.gov (United States)

    Martínez, Carolina; Coll-Bonfill, Nuria; Aramburu, Jose; Pallás, Vicente; Aparicio, Frederic; Galipienso, Luis

    2014-05-12

    The movement protein (MP) of parietaria mottle virus (PMoV) is required for virus cell-to-cell movement. Bioinformatics analysis identified two hydrophilic non-contiguous regions (R1 and R2) rich in the basic amino acids lysine and arginine and with the predicted secondary structure of an α-helix. Different approaches were used to determine the implication of the R1 and R2 regions in RNA binding, plasmodesmata (PD) targeting and cell-to-cell movement. EMSA (Electrophoretic Mobility Shift Assay) showed that both regions have RNA-binding activity whereas that mutational analysis reported that either deletion of any of these regions, or loss of the basic amino acids, interfered with the viral intercellular movement. Subcellular localization studies showed that PMoV MP locates at PD. Mutants designed to impeded cell-to-cell movement failed to accumulate at PD indicating that basic residues in both R1 and R2 are critical for binding the MP at PD.

  2. To Gate, or Not to Gate: Regulatory Mechanisms for Intercellular Protein Transport and Virus Movement in Plants

    Institute of Scientific and Technical Information of China (English)

    Shoko Ueki; Vitaly Citovsky

    2011-01-01

    Cell-to-cell signal transduction is vital for orchestrating the whole-body physiology of multi-cellular organisms,and many endogenous macromolecules,proteins,and nucleic acids function as such transported signals.In plants,many of these molecules are transported through plasmodesmata (Pd),the cell wall-spanning channel structures that interconnect plant cells.Furthermore,Pd also act as conduits for cell-to-cell movement of most plant viruses that have evolved to pirate these channels to spread the infection.Pd transport is presumed to be highly selective,and only a limited repertoire of molecules is transported through these channels.Recent studies have begun to unravel mechanisms that actively regulate the opening of the Pd channel to allow traffic.This macromolecular transport between cells comprises two consecutive steps:intracellular targeting to Pd and translocation through the channel to the adjacent cell.Here,we review the current knowledge of molecular species that are transported though Pd and the mechanisms that control this traffic.Generally,Pd traffic can occur by passive diffusion through the trans-Pd cytoplasm or through the membrane/lumen of the trans-Pd ER,or by active transport that includes protein-protein interactions.It is this latter mode of Pd transport that is involved in intercellular traffic of most signal molecules and is regulated by distinct and sometimes interdependent mechanisms,which represent the focus of this article.

  3. The reorganization of root anatomy and ultrastructure of syncytial cells in tomato (Lycopersicon esculentum Mill. infected with potato cyst nematode (Globodera rostochiensis Woll.

    Directory of Open Access Journals (Sweden)

    Sylwia Fudali

    2011-01-01

    Full Text Available The sequence of anatomical and ultrastructural events leading to the syncytium development in tomato roots infected with Globodera rostochiensis was examined. The syncytia were preferentially induced in cortical or pericyclic cells in the elongation zone of root. They developed towards the vascular cylinder by incorporation of new cells via local cell wall breakdown. After surrounding primary phloem bundle and reaching xylem tracheary elements syncytia spread along vascular cylinder. Roots in primary state of growth seemed to be the best place for syncytium induction as syncytia formed in the zone of secondary growth were less hypertrophied. At the ultrastructural level syncytial elements were characterized by strong hypertrophy, breakdown of central vacuole, increased volume of cytoplasm, proliferation of organelles, and enlargement of nuclei. On the syncytial wall adjoining vessels the cell wall ingrowths were formed, while the syncytial walls at interface of phloem were considerably thickened. They lacked of functional plasmodesmata and did not form any ingrowths. Using immunofluorescent-labelling and immunogold-labelling methods tomato expansin 5 protein was localized in nematode infected roots. The distribution of LeEXP A5 was restricted only to the walls of syncytia. The protein distribution pattern indicated that LeEXP A5 could mediates cell wall expansion during hypertrophy of syncytial elements.

  4. Correlative imaging of fluorescent proteins in resin-embedded plant material.

    Science.gov (United States)

    Bell, Karen; Mitchell, Steve; Paultre, Danae; Posch, Markus; Oparka, Karl

    2013-04-01

    Fluorescent proteins (FPs) were developed for live-cell imaging and have revolutionized cell biology. However, not all plant tissues are accessible to live imaging using confocal microscopy, necessitating alternative approaches for protein localization. An example is the phloem, a tissue embedded deep within plant organs and sensitive to damage. To facilitate accurate localization of FPs within recalcitrant tissues, we developed a simple method for retaining FPs after resin embedding. This method is based on low-temperature fixation and dehydration, followed by embedding in London Resin White, and avoids the need for cryosections. We show that a palette of FPs can be localized in plant tissues while retaining good structural cell preservation, and that the polymerized block face can be counterstained with cell wall probes. Using this method we have been able to image green fluorescent protein-labeled plasmodesmata to a depth of more than 40 μm beneath the resin surface. Using correlative light and electron microscopy of the phloem, we were able to locate the same FP-labeled sieve elements in semithin and ultrathin sections. Sections were amenable to antibody labeling, and allowed a combination of confocal and superresolution imaging (three-dimensional-structured illumination microscopy) on the same cells. These correlative imaging methods should find several uses in plant cell biology.

  5. Tobacco mosaic virus (TMV) replicase and movement protein function synergistically in facilitating TMV spread by lateral diffusion in the plasmodesmal desmotubule of Nicotiana benthamiana.

    Science.gov (United States)

    Guenoune-Gelbart, Dana; Elbaum, Michael; Sagi, Guy; Levy, Amit; Epel, Bernard L

    2008-03-01

    Virus spread through plasmodesmata (Pd) is mediated by virus-encoded movement proteins (MPs) that modify Pd structure and function. The MP of Tobacco mosaic virus ((TMV)MP) is an endoplasmic reticulum (ER) integral membrane protein that binds viral RNA (vRNA), forming a vRNA:MP:ER complex. It has been hypothesized that (TMV)MP causes Pd to dilate, thus potentiating a cytoskeletal mediated sliding of the vRNA:MP:ER complex through Pd; in the absence of MP, by contrast, the ER cannot move through Pd. An alternate model proposes that cell-to-cell spread takes place by diffusion of the MP:vRNA complex in the ER membranes which traverse Pd. To test these models, we measured the effect of (TMV)MP and replicase expression on cell-to-cell spread of several green fluorescent protein-fused probes: a soluble cytoplasmic protein, two ER lumen proteins, and two ER membrane-bound proteins. Our data support the diffusion model in which a complex that includes ER-embedded MP, vRNA, and other components diffuses in the ER membrane within the Pd driven by the concentration gradient between an infected cell and adjacent noninfected cells. The data also suggest that the virus replicase and MP function together in altering Pd conductivity.

  6. Tobacco mutants with reduced microtubule dynamics are less susceptible to TMV.

    Science.gov (United States)

    Ouko, Maurice O; Sambade, Adrian; Brandner, Katrin; Niehl, Annette; Peña, Eduardo; Ahad, Abdul; Heinlein, Manfred; Nick, Peter

    2010-06-01

    A panel of seven SR1 tobacco mutants (ATER1 to ATER7) derived via T-DNA activation tagging and screening for resistance to a microtubule assembly inhibitor, ethyl phenyl carbamate, were used to study the role of microtubules during infection and spread of tobacco mosaic virus (TMV). In one of these lines, ATER2, alpha-tubulin is shifted from the tyrosinylated into the detyrosinated form, and the microtubule plus-end marker GFP-EB1 moves significantly slower when expressed in the background of the ATER2 mutant as compared with the SR1 wild type. The efficiency of cell-to-cell movement of TMV encoding GFP-tagged movement protein (MP-GFP) is reduced in ATER2 accompanied by a reduced association of MP-GFP with plasmodesmata. This mutant is also more tolerant to viral infection as compared with the SR1 wild type, implying that reduced microtubule dynamics confer a comparative advantage in face of TMV infection.

  7. Characterization of somatic embryo attached structures in Feijoa sellowiana Berg. (Myrtaceae).

    Science.gov (United States)

    Correia, Sandra M; Canhoto, Jorge M

    2010-06-01

    The presence of an attached organ to somatic embryos of angiosperms connecting the embryo to the supporting tissue has been a subject of controversy. This study shows that 67% of the morphologically normal somatic embryos of Feijoa sellowiana possess this type of organ and that its formation was not affected by culture media composition. Histological and ultrastructural analysis indicated that the attached structures of somatic embryos displayed a great morphological diversity ranging from a few cells to massive and columnar structures. This contrast with the simple suspensors observed in zygotic embryos which were only formed by five cells. As well as the suspensor of zygotic embryos, somatic embryo attached structures undergo a process of degeneration in later stages of embryo development. Other characteristic shared by zygotic suspensors and somatic embryo attached structures was the presence of thick cell walls surrounding the cells. Elongated thin filaments were often associated with the structures attached to somatic embryos, whereas in other cases, tubular cells containing starch grains connected the embryo to the supporting tissue. These characteristics associated with the presence of plasmodesmata in the cells of the attached structures seem to indicate a role on embryo nutrition. However, cell proliferation in the attached structures resulting into new somatic embryos may also suggest a more complex relationship between the embryo and the structures connecting it to the supporting tissue.

  8. SHOOT MERISTEMLESS trafficking controls axillary meristem formation, meristem size and organ boundaries in Arabidopsis.

    Science.gov (United States)

    Balkunde, Rachappa; Kitagawa, Munenori; Xu, Xianfeng Morgan; Wang, Jing; Jackson, David

    2017-05-01

    The shoot stem cell niche, contained within the shoot apical meristem (SAM) is maintained in Arabidopsis by the homeodomain protein SHOOT MERISTEMLESS (STM). STM is a mobile protein that traffics cell-to-cell, presumably through plasmodesmata. In maize, the STM homolog KNOTTED1 shows clear differences between mRNA and protein localization domains in the SAM. However, the STM mRNA and protein localization domains are not obviously different in Arabidopsis, and the functional relevance of STM mobility is unknown. Using a non-mobile version of STM (2xNLS-YFP-STM), we show that STM mobility is required to suppress axillary meristem formation during embryogenesis, to maintain meristem size, and to precisely specify organ boundaries throughout development. STM and organ boundary genes CUP SHAPED COTYLEDON1 (CUC1), CUC2 and CUC3 regulate each other during embryogenesis to establish the embryonic SAM and to specify cotyledon boundaries, and STM controls CUC expression post-embryonically at organ boundary domains. We show that organ boundary specification by correct spatial expression of CUC genes requires STM mobility in the meristem. Our data suggest that STM mobility is critical for its normal function in shoot stem cell control. © 2017 The Authors The Plant Journal © 2017 John Wiley & Sons Ltd.

  9. Dielectric properties of biological tissues in which cells are connected by communicating junctions

    Science.gov (United States)

    Asami, Koji

    2007-06-01

    The frequency dependence of the complex permittivity of biological tissues has been simulated using a simple model that is a cubic array of spherical cells in a parallel plate capacitor. The cells are connected by two types of communicating junctions: one is a membrane-lined channel for plasmodesmata in plant tissues, and the other is a conducting patch of adjoining plasma membranes for gap junctions in animal tissues. Both junctions provided similar effects on the dielectric properties of the tissue model. The model without junction showed a dielectric relaxation (called β-dispersion) that was expected from an interfacial polarization theory for a concentrated suspension of spherical cells. The dielectric relaxation was the same as that of the model in which neighbouring cells were connected by junctions perpendicular to the applied electric field. When neighbouring cells were connected by junctions parallel to the applied electric field or in all directions, a dielectric relaxation appeared at a lower frequency side in addition to the β-dispersion, corresponding to the so called α-dispersion. When junctions were randomly introduced at varied probabilities Pj, the low-frequency (LF) relaxation curve became broader, especially at Pj of 0.2-0.5, and its intensity was proportional to Pj up to 0.7. The intensity and the characteristic frequency of the LF relaxation both decreased with decreasing junction conductance. The simulations indicate that communicating junctions are important for understanding the LF dielectric relaxation in tissues.

  10. Parallels and distinctions in the direct cell-to-cell spread of the plant and animal viruses.

    Science.gov (United States)

    Ritzenthaler, Christophe

    2011-11-01

    The paradigm that viruses can move directly, and in some cases covertly, between contacting target cells is now well established for several virus families. The underlying mechanisms of cell-to-cell spread, however, remain to be fully elucidated and may differ substantially depending on the viral exit/entry route and the cellular tropism. Here, two divergent cell-to-cell spread mechanisms are exemplified: firstly by human retroviruses, which rely upon transient adhesive structures that form between polarized immune cells termed virological synapses, and secondly by herpesviruses that depend predominantly on pre-existing stable cellular contacts, but may also form virological synapses. Plant viruses can also spread directly between contacting cells, but are obliged by the rigid host cell wall to move across pore structures termed plasmodesmata. This review will focus primarily on recent advances in our understanding of animal virus cell-to-cell spread using examples from these two virus families to highlight differences and similarities, and will conclude by comparing and contrasting the cell-to-cell spread of animal and plant viruses. Copyright © 2011 Elsevier B.V. All rights reserved.

  11. Lost in Transit: Long-Distance Trafficking and Phloem Unloading of Protein Signals in Arabidopsis Homografts[OPEN

    Science.gov (United States)

    Gustin, Marie-Paule; Molnar, Attila; Oparka, Karl J.

    2016-01-01

    In addition to moving sugars and nutrients, the phloem transports many macromolecules. While grafting and aphid stylectomy experiments have identified many macromolecules that move in the phloem, the functional significance of phloem transport of these remains unclear. To gain insight into protein trafficking, we micrografted Arabidopsis thaliana scions expressing GFP-tagged chloroplast transit peptides under the 35S promoter onto nontransgenic rootstocks. We found that plastids in the root tip became fluorescent 10 d after grafting. We obtained identical results with the companion cell-specific promoter SUC2 and with signals that target proteins to peroxisomes, actin, and the nucleus. We were unable to detect the respective mRNAs in the rootstock, indicating extensive movement of proteins in the phloem. Outward movement from the root protophloem was restricted to the pericycle-endodermis boundary, identifying plasmodesmata at this interface as control points in the exchange of macromolecules between stele and cortex. Intriguingly, signals directing proteins to the endoplasmic reticulum and Golgi apparatus from membrane-bound ribosomes were not translocated to the root. It appears that many organelle-targeting sequences are insufficient to prevent the loss of their proteins into the translocation stream. Thus, nonspecific loss of proteins from companion cells to sieve elements may explain the plethora of macromolecules identified in phloem sap. PMID:27600534

  12. Changes in Cell Ultrastructure in Maize Leaves Infected by Maize Dwarf Mosaic Virus

    Institute of Scientific and Technical Information of China (English)

    GUO Xing-qi; ZHU Xiao-ping; ZHANG Jie-dao; GUO Yan-kui

    2003-01-01

    Ultrastructural alterations in foliar cells were studied in leaves of resistant maize varietyLuyu16 and susceptible maize inbred line Luyuan92 infected by maize dwarf mosaic virus Shandong isolate(MDMV-SD), respectively. The results showed that marked cytopathological alterations were observed both inresistant plants and in susceptible plants, compared with that in healthy plants. However, some ultrastructur-al alterations, which observed in resistant plants, were different from those in susceptible plants. In resistantplants, which infected with the virus, the main organelles, including chloroplasts and mitochondria, wereslightly destroyed, the amount of mitochondria and peroxisome were increased. A few or no plasmodesmatawere observed. There were three kinds of inclusions including pinwheel, bundle and laminated aggregate, andthe virus particles in the cytoplasm. In susceptible plants, which infected with the virus, the chloroplasts wereheavily disrupted, including thylakoid swelling and envelope broking. The virus particles were more than thosein the resistant variety. Four kinds of inclusions including pinwheel, bundle, laminated aggregate and highelecton-dense body appeared in cytoplasm. Plasmodesmata and plasma membrane were abundant, and therewere frequent invaginations of the plasma membrane that led to the formation of vesicles and myelin-likestructures.

  13. Fusion to GFP blocks intercellular trafficking of the sucrose transporter SUT1 leading to accumulation in companion cells

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    Walsh Rama

    2003-12-01

    Full Text Available Abstract Background Plant phloem consists of an interdependent cell pair, the sieve element / companion cell complex. Sucrose transporters are localized to enucleate sieve elements (SE, despite being transcribed in companion cells (CC. Due to the high turnover of SUT1, sucrose transporter mRNA or protein must traffic from CC to SE via the plasmodesmata. Localization of SUT mRNA at plasmodesmatal orifices connecting CC and SE suggests RNA transport, potentially mediated by RNA binding proteins. In many organisms, polar RNA transport is mediated through RNA binding proteins interacting with the 3'-UTR and controlling localized protein synthesis. To study mechanisms for trafficking of SUT1, GFP-fusions with and without 3'-UTR were expressed in transgenic plants. Results In contrast to plants expressing GFP from the strong SUC2 promoter, in RolC-controlled expression GFP is retained in companion cells. The 3'-UTR of SUT1 affected intracellular distribution of GFP but was insufficient for trafficking of SUT1, GFP or their fusions to SEs. Fusion of GFP to SUT1 did however lead to accumulation of SUT1-GFP in the CC, indicating that trafficking was blocked while translational inhibition of SUT1 mRNA was released in CCs. Conclusion A fusion with GFP prevents targeting of the sucrose transporter SUT1 to the SE while leading to accumulation in the CC. The 3'-UTR of SUT1 is insufficient for mobilization of either the fusion or GFP alone. It is conceivable that SUT1-GFP protein transport through PD to SE was blocked due to the presence of GFP, resulting in retention in CC particles. Alternatively, SUT1 mRNA transport through the PD could have been blocked due to insertion of GFP between the SUT1 coding sequence and 3'-UTR.

  14. Bud development in corydalis (Corydalis bracteata) requires low temperature: a study of developmental and carbohydrate changes

    Science.gov (United States)

    Khodorova, Nadejda V.; Miroslavov, Evgeniy A.; Shavarda, Alexey L.; Laberche, Jean-Claude; Boitel-Conti, Michèle

    2010-01-01

    Background and Aims Spring geophytes require a period of low temperature for proper flower development but the mechanism that underlies the relationship between cold treatment and flowering remains unknown. The present study aims to compare the developmental anatomy and carbohydrate content of the tuberous geophyte Corydalis bracteata growing under natural winter conditions from 10 to −10 °C (field-grown) and under a mild temperature regime of 18 °C (indoor-grown plants). Methods Samples were studied under light and electron microscopy. A histochemical test (periodic acid – Schiff's) was employed to identify starch in sectioned material. Sugars were analysed by capillary gas chromatography. Apoplastic wash fluid was prepared. Key Results Under natural conditions, shoots were elongated, and buds gained in dry mass and developed normally. For indoor-grown plants, these parameters were lower in value and, from December, a progressive necrosis of flower buds was observed. The tuber consisted of the new developing one, which was connected to the bud, and the old tuber with its starch reserve. Due to the absence of plasmodesmata between new and old tuber cells, sugar transport cannot be through the symplast. Thus, a potential apoplastic route is proposed from old tuber phloem parenchyma cells to the adjacent new tuber cells. Sugar content in buds during the autumn months (September–November) was lower for indoor-grown plants than control plants, whereas the sugar content in tubers during the same period was similar for plants from both temperature treatments. However, the amount of apoplastic sugars in tubers of field-grown plants was almost 15-fold higher than in indoor-grown tubers. Conclusions The results suggest that low temperature activates the apoplastic route of sugar transport in C. bracteata tubers and a consequent carbohydrate delivery to the bud. In the absence of cold treatment, the carbohydrate reserve is locked in old tuber cells so the nutrient

  15. Does Don Fisher's high-pressure manifold model account for phloem transport and resource partitioning?

    Science.gov (United States)

    Patrick, John W

    2013-01-01

    The pressure flow model of phloem transport envisaged by Münch (1930) has gained wide acceptance. Recently, however, the model has been questioned on structural and physiological grounds. For instance, sub-structures of sieve elements may reduce their hydraulic conductances to levels that impede flow rates of phloem sap and observed magnitudes of pressure gradients to drive flow along sieve tubes could be inadequate in tall trees. A variant of the Münch pressure flow model, the high-pressure manifold model of phloem transport introduced by Donald Fisher may serve to reconcile at least some of these questions. To this end, key predicted features of the high-pressure manifold model of phloem transport are evaluated against current knowledge of the physiology of phloem transport. These features include: (1) An absence of significant gradients in axial hydrostatic pressure in sieve elements from collection to release phloem accompanied by transport properties of sieve elements that underpin this outcome; (2) Symplasmic pathways of phloem unloading into sink organs impose a major constraint over bulk flow rates of resources translocated through the source-path-sink system; (3) Hydraulic conductances of plasmodesmata, linking sieve elements with surrounding phloem parenchyma cells, are sufficient to support and also regulate bulk flow rates exiting from sieve elements of release phloem. The review identifies strong circumstantial evidence that resource transport through the source-path-sink system is consistent with the high-pressure manifold model of phloem transport. The analysis then moves to exploring mechanisms that may link demand for resources, by cells of meristematic and expansion/storage sinks, with plasmodesmal conductances of release phloem. The review concludes with a brief discussion of how these mechanisms may offer novel opportunities to enhance crop biomass yields.

  16. Citrus tristeza virus p23: a unique protein mediating key virus-host interactions

    Directory of Open Access Journals (Sweden)

    Ricardo eFlores

    2013-05-01

    Full Text Available The large RNA genome of CTV (ca. 20 kb contains 12 open reading frames (ORFs, with the 3’-terminal one corresponding to a protein of 209 amino acids (p23 that is expressed from an abundant subgenomic RNA. p23, an RNA-binding protein with a putative Zn-finger domain and some basic motifs, is unique to CTV because no homologues have been found in other closteroviruses, including the type species of the genus Beet yellows virus (despite both viruses having many homologous genes. Consequently, p23 might have evolved for the specific interaction of CTV with its citrus hosts. From a functional perspective p23 has been involved in many roles: i regulation of the asymmetrical accumulation of CTV RNA strands, ii induction of the seedling yellows syndrome in sour orange and grapefruit, iii intracellular suppression of RNA silencing, iv elicitation of CTV-like symptoms when expressed ectopically as a transgene in several Citrus spp., and v enhancement of systemic infection (and virus accumulation in sour orange and CTV release from the phloem in p23-expressing transgenic sweet and sour orange. Moreover, transformation of Mexican lime with intron-hairpin constructs designed for the co-inactivation of p23 and the two other CTV silencing suppressors results in complete resistance against the homologous virus. From a cellular point of view, recent data indicate that p23 accumulates preferentially in the nucleolus, being the first closterovirus protein with such a subcellular localization, as well as in plasmodesmata. These major accumulation sites most likely determine some of the functional roles of p23.

  17. Regulation of HbPIP2;3, a Latex-Abundant Water Transporter, Is Associated with Latex Dilution and Yield in the Rubber Tree (Hevea brasiliensis Muell. Arg.).

    Science.gov (United States)

    An, Feng; Zou, Zhi; Cai, Xiuqing; Wang, Jin; Rookes, James; Lin, Weifu; Cahill, David; Kong, Lingxue

    2015-01-01

    Rubber tree (Hevea brasiliensis) latex, the source of natural rubber, is synthesised in the cytoplasm of laticifers. Efficient water inflow into laticifers is crucial for latex flow and production since it is the determinant of the total solid content of latex and its fluidity after tapping. As the mature laticifer vessel rings are devoid of plasmodesmata, water exchange between laticifers and surrounding cells is believed to be governed by plasma membrane intrinsic proteins (PIPs). To identify the most important PIP aquaporin in the water balance of laticifers, the transcriptional profiles of ten-latex-expressed PIPs were analysed. One of the most abundant transcripts, designated HbPIP2;3, was characterised in this study. When tested in Xenopus laevis oocytes HbPIP2;3 showed a high efficiency in increasing plasmalemma water conductance. Expression analysis indicated that the HbPIP2;3 gene was preferentially expressed in latex, and the transcripts were up-regulated by both wounding and exogenously applied Ethrel (a commonly-used ethylene releaser). Although regular tapping up-regulated the expression of HbPIP2;3 during the first few tappings of the virginal rubber trees, the transcriptional kinetics of HbPIP2;3 to Ethrel stimulation in the regularly tapped tree exhibited a similar pattern to that of the previously reported HbPIP2;1 in the virginal rubber trees. Furthermore, the mRNA level of HbPIP2;3 was associated with clonal yield potential and the Ethrel stimulation response. Together, these results have revealed the central regulatory role of HbPIP2;3 in laticifer water balance and ethylene stimulation of latex production in Hevea.

  18. The Arabidopsis class VIII myosin ATM2 is involved in endocytosis.

    Science.gov (United States)

    Sattarzadeh, Amirali; Franzen, Rainer; Schmelzer, Elmon

    2008-06-01

    Members of the class XI of the myosin superfamily comprising higher plant, actin-based molecular motors have been shown to be involved in peroxisome and Golgi vesicle trafficking comparable to yeast and animal class V myosins. The tasks of the second class of myosins of higher plants, class VIII, are unclear. In this study the class VIII myosin ATM2 from the model plant Arabidopsis thaliana was selected for the examination of cargo specificity in vivo. Fluorescent protein-fusion plasmid constructs with fragments of the ATM2 cDNA were generated and used for Agrobacterium tumefaciens-based transient transformation of Nicotiana benthamiana leaves. The resulting subcellular localization patterns were recorded by live imaging with confocal laser scanning microscopy (CLSM) in epidermal leaf cells. Expression of a nearly full-length construct displayed labeling of filaments and vesicles, a head + neck fragment led to decoration of filaments only. However, expression of fluorescent protein-tagged C-terminal tail domain constructs labeled vesicular structures of different appearance. Most importantly, coexpression of different RFP/YFP-ATM2 tail fusion proteins showed colocalization and, hence, binding to the same type of vesicular target. Further coexpression experiments of RFP/YFP-ATM2 tail fusion proteins with the endosomal marker FYVE and the endosomal tracer FM4-64 demonstrated colocalization with endosomes. Colocalization was also detected by expression of the CFP-tagged membrane receptor BRI1 as marker, which is constantly recycled via endosomes. Occasionally the ATM2 tail targeted to sites at the plasma membrane closely resembling the pattern obtained upon expression of the YFP-ATM1 C-terminal tail. ATM1 is known for its localization at the plasma membrane at sites of plasmodesmata. Copyright 2008 Wiley-Liss, Inc.

  19. Multi-Scale Characean Experimental System: From Electrophysiology of Membrane Transporters to Cell-to-Cell Connectivity, Cytoplasmic Streaming and Auxin Metabolism

    Science.gov (United States)

    Beilby, Mary J.

    2016-01-01

    The morphology of characean algae could be mistaken for a higher plant: stem-like axes with leaf-like branchlets anchored in the soil by root-like rhizoids. However, all of these structures are made up of giant multinucleate cells separated by multicellular nodal complexes. The excised internodal cells survive long enough for the nodes to give rise to new thallus. The size of the internodes and their thick cytoplasmic layer minimize impalement injury and allow specific micro-electrode placement. The cell structure can be manipulated by centrifugation, perfusion of cell contents or creation of cytoplasmic droplets, allowing access to both vacuolar and cytoplasmic compartments and both sides of the cell membranes. Thousands of electrical measurements on intact or altered cells and cytoplasmic droplets laid down basis to modern plant electrophysiology. Furthermore, the giant internodal cells and whole thalli facilitate research into many other plant properties. As nutrients have to be transported from rhizoids to growing parts of the thallus and hormonal signals need to pass from cell to cell, Characeae possess very fast cytoplasmic streaming. The mechanism was resolved in the characean model. Plasmodesmata between the internodal cells and nodal complexes facilitate transport of ions, nutrients and photosynthates across the nodes. The internal structure was found to be similar to those of higher plants. Recent experiments suggest a strong circadian influence on metabolic pathways producing indole-3-acetic acid (IAA) and serotonin/melatonin. The review will discuss the impact of the characean models arising from fragments of cells, single cells, cell-to-cell transport or whole thalli on understanding of plant evolution and physiology. PMID:27504112

  20. Characterization, localization, and seasonal changes of the sucrose transporter FeSUT1 in the phloem of Fraxinus excelsior.

    Science.gov (United States)

    Öner-Sieben, Soner; Rappl, Christine; Sauer, Norbert; Stadler, Ruth; Lohaus, Gertrud

    2015-08-01

    Trees are generally assumed to be symplastic phloem loaders. A typical feature for most wooden species is an open minor vein structure with symplastic connections between mesophyll cells and phloem cells, which allow sucrose to move cell-to-cell through the plasmodesmata into the phloem. Fraxinus excelsior (Oleaceae) also translocates raffinose family oligosaccharides in addition to sucrose. Sucrose concentration was recently shown to be higher in the phloem sap than in the mesophyll cells. This suggests the involvement of apoplastic steps and the activity of sucrose transporters in addition to symplastic phloem-loading processes. In this study, the sucrose transporter FeSUT1 from F. excelsior was analysed. Heterologous expression in baker's yeast showed that FeSUT1 mediates the uptake of sucrose. Immunohistochemical analyses revealed that FeSUT1 was exclusively located in phloem cells of minor veins and in the transport phloem of F. excelsior. Further characterization identified these cells as sieve elements and possibly ordinary companion cells but not as intermediary cells. The localization and expression pattern point towards functions of FeSUT1 in phloem loading of sucrose as well as in sucrose retrieval. FeSUT1 is most likely responsible for the observed sucrose gradient between mesophyll and phloem. The elevated expression level of FeSUT1 indicated an increased apoplastic carbon export activity from the leaves during spring and late autumn. It is hypothesized that the importance of apoplastic loading is high under low-sucrose conditions and that the availability of two different phloem-loading mechanisms confers advantages for temperate woody species like F. excelsior.

  1. Rice dwarf phytoreovirus segment S6-encoded nonstructural protein has a cell-to-cell movement function.

    Science.gov (United States)

    Li, Yi; Bao, Yi M; Wei, Chun H; Kang, Zhen S; Zhong, Yong W; Mao, Peng; Wu, Gang; Chen, Zhang L; Schiemann, Joachim; Nelson, Richard S

    2004-05-01

    Rice dwarf virus (RDV) is a member of the genus Phytoreovirus, which is composed of viruses with segmented double-stranded RNA genomes. Proteins that support the intercellular movement of these viruses in the host have not been identified. Microprojectile bombardment was used to determine which open reading frames (ORFs) support intercellular movement of a heterologous virus. A plasmid containing an infectious clone of Potato virus X (PVX) defective in cell-to-cell movement and expressing either beta-glucuronidase or green fluorescent protein (GFP) was used for cobombardment with plasmids containing ORFs from RDV gene segments S1 through S12 onto leaves of Nicotiana benthamiana. Cell-to-cell movement of the movement-defective PVX was restored by cobombardment with a plasmid containing S6. In the absence of S6, no other gene segment supported movement. Identical results were obtained with Nicotiana tabacum, a host that allows fewer viruses to infect and spread within its tissue. S6 supported the cell-to-cell movement of the movement-defective PVX in sink and source leaves of N. benthamiana. A mutant S6 lacking the translation start codon did not complement the cell-to-cell movement of the movement-defective PVX. An S6 protein product (Pns6)-enhanced GFP fusion was observed near or within cell walls of epidermal cells from N. tabacum. By immunocytochemistry, unfused Pns6 was localized to plasmodesmata in rice leaves infected with RDV. S6 thus encodes a protein with characteristics identical to those of other viral proteins required for the cell-to-cell movement of their genome and therefore is likely required for the cell-to-cell movement of RDV.

  2. Multi-scale characean experimental system: from electrophysiology of membrane transporters to cell-to-cell connectivity, cytoplasmic streaming and auxin metabolism.

    Directory of Open Access Journals (Sweden)

    Mary Jane Beilby

    2016-07-01

    Full Text Available The morphology of characean algae could be mistaken for a higher plant: stem-like axes with leaf-like branchlets anchored in the soil by root-like rhizoids. However, all of these structures are made up of giant multinucleate cells separated by multicellular nodal complexes. The excised internodal cells survive long enough for the nodes to give rise to new thallus. The size of the internodes and their thick cytoplasmic layer minimize impalement injury and allow specific micro-electrode placement. The cell structure can be manipulated by centrifugation, perfusion of cell contents or creation of cytoplasmic droplets, allowing access to both vacuolar and cytoplasmic compartments and both sides of the cell membranes. Thousands of electrical measurements on intact or altered cells and cytoplasmic droplets laid down basis to modern plant electrophysiology. Furthermore, the giant internodal cells and whole thalli facilitate research into many other plant properties. As nutrients have to be transported from rhizoids to growing parts of the thallus and hormonal signals need to pass from cell to cell, Characeae possess very fast cytoplasmic streaming. The mechanism was resolved in the characean model. Plasmodesmata between the internodal cells and nodal complexes facilitate transport of ions, nutrients and photosynthates across the nodes. The internal structure was found to be similar to those of higher plants. Recent experiments suggest a strong circadian influence on metabolic pathways producing indole-3-acetic acid (IAA and serotonin/melatonin. The review will discuss the impact of the characean models arising from fragments of cells, single cells, cell-to-cell transport or whole thalli on understanding of plant evolution and physiology.

  3. Multi-Scale Characean Experimental System: From Electrophysiology of Membrane Transporters to Cell-to-Cell Connectivity, Cytoplasmic Streaming and Auxin Metabolism.

    Science.gov (United States)

    Beilby, Mary J

    2016-01-01

    The morphology of characean algae could be mistaken for a higher plant: stem-like axes with leaf-like branchlets anchored in the soil by root-like rhizoids. However, all of these structures are made up of giant multinucleate cells separated by multicellular nodal complexes. The excised internodal cells survive long enough for the nodes to give rise to new thallus. The size of the internodes and their thick cytoplasmic layer minimize impalement injury and allow specific micro-electrode placement. The cell structure can be manipulated by centrifugation, perfusion of cell contents or creation of cytoplasmic droplets, allowing access to both vacuolar and cytoplasmic compartments and both sides of the cell membranes. Thousands of electrical measurements on intact or altered cells and cytoplasmic droplets laid down basis to modern plant electrophysiology. Furthermore, the giant internodal cells and whole thalli facilitate research into many other plant properties. As nutrients have to be transported from rhizoids to growing parts of the thallus and hormonal signals need to pass from cell to cell, Characeae possess very fast cytoplasmic streaming. The mechanism was resolved in the characean model. Plasmodesmata between the internodal cells and nodal complexes facilitate transport of ions, nutrients and photosynthates across the nodes. The internal structure was found to be similar to those of higher plants. Recent experiments suggest a strong circadian influence on metabolic pathways producing indole-3-acetic acid (IAA) and serotonin/melatonin. The review will discuss the impact of the characean models arising from fragments of cells, single cells, cell-to-cell transport or whole thalli on understanding of plant evolution and physiology.

  4. A set of fluorescent protein-based markers expressed from constitutive and arbuscular mycorrhiza-inducible promoters to label organelles, membranes and cytoskeletal elements in Medicago truncatula.

    Science.gov (United States)

    Ivanov, Sergey; Harrison, Maria J

    2014-12-01

    Medicago truncatula is widely used for analyses of arbuscular mycorrhizal (AM) symbiosis and nodulation. To complement the genetic and genomic resources that exist for this species, we generated fluorescent protein fusions that label the nucleus, endoplasmic reticulum, Golgi apparatus, trans-Golgi network, plasma membrane, apoplast, late endosome/multivesicular bodies (MVB), transitory late endosome/ tonoplast, tonoplast, plastids, mitochondria, peroxisomes, autophagosomes, plasmodesmata, actin, microtubules, periarbuscular membrane (PAM) and periarbuscular apoplastic space (PAS) and expressed them from the constitutive AtUBQ10 promoter and the AM symbiosis-specific MtBCP1 promoter. All marker constructs showed the expected expression patterns and sub-cellular locations in M. truncatula root cells. As a demonstration of their utility, we used several markers to investigate AM symbiosis where root cells undergo major cellular alterations to accommodate their fungal endosymbiont. We demonstrate that changes in the position and size of the nuclei occur prior to hyphal entry into the cortical cells and do not require DELLA signaling. Changes in the cytoskeleton, tonoplast and plastids also occur in the colonized cells and in contrast to previous studies, we show that stromulated plastids are abundant in cells with developing and mature arbuscules, while lens-shaped plastids occur in cells with degenerating arbuscules. Arbuscule development and secretion of the PAM creates a periarbuscular apoplastic compartment which has been assumed to be continuous with apoplast of the cell. However, fluorescent markers secreted to the periarbuscular apoplast challenge this assumption. This marker resource will facilitate cell biology studies of AM symbiosis, as well as other aspects of legume biology. © 2014 The Authors The Plant Journal © 2014 John Wiley & Sons Ltd.

  5. Localization and movement of mineral oil in plants by fluorescence and confocal microscopy.

    Science.gov (United States)

    Tan, B L; Sarafis, V; Beattie, G A C; White, R; Darley, E M; Spooner-Hart, R

    2005-10-01

    Fluorescence and confocal laser scanning microscopy were explored to investigate the movement and localization of mineral oils in citrus. In a laboratory experiment, fluorescence microscopy observation indicated that when a 'narrow' distillation fraction of an nC23 horticultural mineral oil was applied to adaxial and opposing abaxial leaf surfaces of potted orange [Citrus x aurantium L. (Sapindales: Rutaceae)] trees, oil penetrated steadily into treated leaves and, subsequently, moved to untreated petioles of the leaves and adjacent untreated stems. In another experiment, confocal laser scanning microscopy was used to visualize the penetration into, and the subsequent cellular distribution of, an nC24 agricultural mineral oil in C. trifoliata L. seedlings. Oil droplets penetrated or diffused into plants via both stomata and the cuticle of leaves and stems, and then moved within intercellular spaces and into various cells including phloem and xylem. Oil accumulated in droplets in intercellular spaces and within cells near the cell membrane. Oil entered cells without visibly damaging membranes or causing cell death. In a field experiment with mature orange trees, droplets of an nC23 horticultural mineral oil were observed, by fluorescence microscopy, in phloem sieve elements in spring flush growth produced 4-5 months and 16-17 months after the trees were sprayed with oil. These results suggest that movement of mineral oil in plants is both apoplastic via intercellular spaces and symplastic via plasmodesmata. The putative pattern of the translocation of mineral oil in plants and its relevance to oil-induced chronic phytotoxicity are discussed.

  6. BIOSECURITY FOR REDUCING OCHRATOXIN A PRODUCTIVITY AND THEIR IMPACT ON GERMINATION AND ULTRASTRUCTURES OF GERMINATED WHEAT GRAINS

    Directory of Open Access Journals (Sweden)

    M.M.

    2012-08-01

    Full Text Available Ochratoxin A (OTA is a secondary metabolite of some fungi that causes very serious problems for plants, animals and humans. Various microorganisms such as bacteria and microscopic fungi have been tested for their abilities to prevent ochratoxin A contamination or detoxify foods. In this study, Saccharomyces cerevisiae and Lactobacillus bulgaricus reduced OTA production by Aspergillus ochraceus to 40.88 µg/ml ( productivity 60.69% and 13.80 µg/ml (productivity 20.48% respectively compared with the control (67.35 µg/ml (productivity 100%. The results clearly indicated that the seed germinibility in the presence of OTA was decreased with increasing concentration, whereas the germinibility was uncompletely ceased at high concentration (67.35 µg/ml of OTA. The maximum amount of germination was observed in control (without OTA treatment and at low concentration (13.80 µg/ml within 4 days. Antioxidant enzymes catalase and peroxidase decreased in germinated grains treated with OTA. Catalase was 18.12 U/ml in grains treated with low concentration (13.80 µg/ml of OTA while at high concentration (67.35 µg/ml, it was 12.23 U/ml compared with the control (20.33 U/ml. On the other hand, peroxidase decreased only in germinated grains treated with high concentration of OTA. The ultrastructural studies indicate that there were dramatic differences between the cells of root system of wheat seedlings of grains treated and untreated with the OTA. Cell ultrastructures of treated grains with OTA showed that the cytoplasmic membrane collapses away from the cell wall. Plasmodesmata threads were appeared in untreated cells but not formed in treated cells.

  7. The stable association of virion with the triple-gene-block protein 3-based complex of Bamboo mosaic virus.

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    Yuan-Lin Chou

    Full Text Available The triple-gene-block protein 3 (TGBp3 of Bamboo mosaic virus (BaMV is an integral endoplasmic reticulum (ER membrane protein which is assumed to form a membrane complex to deliver the virus intracellularly. However, the virus entity that is delivered to plasmodesmata (PD and its association with TGBp3-based complexes are not known. Results from chemical extraction and partial proteolysis of TGBp3 in membrane vesicles revealed that TGBp3 has a right-side-out membrane topology; i.e., TGBp3 has its C-terminal tail exposed to the outer surface of ER. Analyses of the TGBp3-specific immunoprecipitate of Sarkosyl-extracted TGBp3-based complex revealed that TGBp1, TGBp2, TGBp3, capsid protein (CP, replicase and viral RNA are potential constituents of virus movement complex. Substantial co-fractionation of TGBp2, TGBp3 and CP, but not TGBp1, in the early eluted gel filtration fractions in which virions were detected after TGBp3-specific immunoprecipitation suggested that the TGBp2- and TGBp3-based complex is able to stably associate with the virion. This notion was confirmed by immunogold-labeling transmission electron microscopy (TEM of the purified virions. In addition, mutational and confocal microscopy analyses revealed that TGBp3 plays a key role in virus cell-to-cell movement by enhancing the TGBp2- and TGBp3-dependent PD localization of TGBp1. Taken together, our results suggested that the cell-to-cell movement of potexvirus requires stable association of the virion cargo with the TGBp2- and TGBp3-based membrane complex and recruitment of TGBp1 to the PD by this complex.

  8. Does Don Fisher’s high-pressure manifold model account for phloem transport and resource partitioning?

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    John William Patrick

    2013-06-01

    Full Text Available The pressure flow model of phloem transport envisaged by Münch (1930 has gained wide acceptance. Recently, however, the model has been questioned on structural and physiological grounds. For instance, sub-structures of sieve elements may reduce their hydraulic conductances to levels that impede flow rates of phloem sap and observed magnitudes of pressure gradients to drive flow along sieve tubes could be inadequate in tall trees. A variant of the Münch pressure flow model, the high-pressure manifold model of phloem transport introduced by Donald Fisher may serve to reconcile at least some of these questions. To this end, key predicted features of the high-pressure manifold model of phloem transport are evaluated against current knowledge of the physiology of phloem transport. These features include: (1 An absence of significant gradients in axial hydrostatic pressure in sieve elements from collection to release phloem accompanied by transport properties of sieve elements that underpin this outcome; (2 Symplasmic pathways of phloem unloading into sink organs impose a major constraint over bulk flow rates of resources translocated through the source-path-sink system; (3 Hydraulic conductances of plasmodesmata, linking sieve elements with surrounding phloem parenchyma cells, are sufficient to support and also regulate bulk flow rates exiting from sieve elements of release phloem. The review identifies strong circumstantial evidence that resource transport through the source-path-sink system is consistent with the high-pressure manifold model of phloem transport. The analysis then moves to exploring mechanisms that may link demand for resources, by cells of meristematic and expansion/storage sinks, with plasmodesmatal conductances of release phloem. The review concludes with a brief discussion of how these mechanisms may offer novel opportunities to enhance crop biomass yields.

  9. Arabidopsis thaliana is a susceptible host plant for the holoparasite Cuscuta spec.

    Science.gov (United States)

    Birschwilks, Mandy; Sauer, Norbert; Scheel, Dierk; Neumann, Stefanie

    2007-10-01

    Arabidopsis thaliana and Cuscuta spec. represent a compatible host-parasite combination. Cuscuta produces a haustorium that penetrates the host tissue. In early stages of development the searching hyphae on the tip of the haustorial cone are connected to the host tissue by interspecific plasmodesmata. Ten days after infection, translocation of the fluorescent dyes, Texas Red (TR) and 5,6-carboxyfluorescein (CF), demonstrates the existence of a continuous connection between xylem and phloem of the host and parasite. Cuscuta becomes the dominant sink in this host-parasite system. Transgenic Arabidopsis plants expressing genes encoding the green fluorescent protein (GFP; 27 kDa) or a GFP-ubiquitin fusion (36 kDa), respectively, under the companion cell (CC)-specific AtSUC2 promoter were used to monitor the transfer of these proteins from the host sieve elements to those of Cuscuta. Although GFP is transferred unimpedly to the parasite, the GFP-ubiquitin fusion could not be detected in Cuscuta. A translocation of the GFP-ubiquitin fusion protein was found to be restricted to the phloem of the host, although a functional symplastic pathway exists between the host and parasite, as demonstrated by the transport of CF. These results indicate a peripheral size exclusion limit (SEL) between 27 and 36 kDa for the symplastic connections between host and Cuscuta sieve elements. Forty-six accessions of A. thaliana covering the entire range of its genetic diversity, as well as Arabidopsis halleri, were found to be susceptible towards Cuscuta reflexa.

  10. Storage sites in seeds of Caesalpinia echinata and C. ferrea (Leguminosae with considerations on nutrients flow

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    Simone de Pádua Teixeira

    2008-02-01

    Full Text Available The seeds of Caesalpinia echinata and C. ferrea behaved as typical endospermic seeds, despite their different morphological classification (exendospermic seeds were described for C. echinata and endospermic seeds for C. ferrea. Then, the aim of this work was to compare, under ultrastructural and histochemical terms, the nature of the storage substances and their accumulation sites, as well as the nutrient flow in seeds of these species. Cotyledons in C. echinata accumulate carbohydrates, lipids and proteins, which are mobilized from the outer to the inner parts as revealed by the position of plasmodesmata. Endosperm in C. ferrea accumulates carbohydrates and in C. echinata accumulates substances during the initial embryogenic phases. Such tissue develops a chalazal haustorium that is responsible for the transport of substances into the endosperm itself and from it into the embryo, confirmed by the presence of transference cells.As sementes de Caesalpinia echinata e C. ferrea comportam-se como endospérmicas, apesar de descritas na literatura como exendospérmicas e endospérmicas, respectivamente. Desta forma, o objetivo deste trabalho foi comparar, em termos ultra-estrutural e histoquímico, a natureza das substâncias de reserva e seus tecidos acumuladores, bem como o fluxo de nutrientes nas sementes destas espécies. Os cotilédones em C. echinata acumulam carboidratos, lipídios e proteínas, mobilizados da periferia para o centro, como visto pelo posicionamento dos plasmodesmas. O endosperma em C. ferrea acumula carboidratos e lipídios, e em C. echinata, acumula substâncias nos estádios iniciais da embriogênese. Este tecido desenvolve um haustório calazal agressivo, que transporta substâncias para o endosperma propriamente dito e deste para o embrião, fato confirmado pela presença de células de transferência no endosperma.

  11. Narrow-Leafed Lupin (Lupinus angustifolius) β1- and β6-Conglutin Proteins Exhibit Antifungal Activity, Protecting Plants against Necrotrophic Pathogen Induced Damage from Sclerotinia sclerotiorum and Phytophthora nicotianae

    Science.gov (United States)

    Jimenez-Lopez, Jose C.; Melser, Su; DeBoer, Kathleen; Thatcher, Louise F.; Kamphuis, Lars G.; Foley, Rhonda C.; Singh, Karam B.

    2016-01-01

    Vicilins (7S globulins) are seed storage proteins and constitute the main protein family in legume seeds, particularly in narrow-leafed lupin (Lupinus angustifolius L.; NLL), where seven vicilin genes, called β1- to β7-conglutin have been identified. Vicilins are involved in germination processes supplying amino acids for seedling growth and plant development, as well as in some cases roles in plant defense and protection against pathogens. The roles of NLL β-conglutins in plant defense are unknown. Here the potential role of five NLL β-conglutin family members in protection against necrotrophic fungal pathogens was investigated and it was demonstrated that recombinant purified 6xHis-tagged β1- and β6-conglutin proteins exhibited the strongest in vitro growth inhibitory activity against a range of necrotrophic fungal pathogens compared to β2, β3, and β4 conglutins. To examine activity in vivo, two representative necrotrophic pathogens, the fungus Sclerotinia sclerotiorum and oomycete Phytophthora nicotianae were used. Transient expression of β1- and β6-conglutin proteins in Nicotiana benthamiana leaves demonstrated in vivo growth suppression of both of these pathogens, resulting in low percentages of hyphal growth and elongation in comparison to control treated leaves. Cellular studies using β1- and β6-GFP fusion proteins showed these conglutins localized to the cell surface including plasmodesmata. Analysis of cellular death following S. sclerotiorum or P. nicotianae revealed both β1- and β6-conglutins suppressed pathogen induced cell death in planta and prevented pathogen induced suppression of the plant oxidative burst as determined by protein oxidation in infected compared to mock-inoculated leaves. PMID:28018392

  12. Ionic self-complementarity induces amyloid-like fibril formation in an isolated domain of a plant copper metallochaperone protein

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    Salom David

    2004-06-01

    Full Text Available Abstract Background Arabidopsis thaliana copper metallochaperone CCH is a functional homologue of yeast antioxidant ATX1, involved in cytosolic copper transport. In higher plants, CCH has to be transported to specialised cells through plasmodesmata, being the only metallochaperone reported to date that leaves the cell where it is synthesised. CCH has two different domains, the N-terminal domain conserved among other copper-metallochaperones and a C-terminal domain absent in all the identified non-plant metallochaperones. The aim of the present study was the biochemical and biophysical characterisation of the C-terminal domain of the copper metallochaperone CCH. Results The conformational behaviour of the isolated C-domain in solution is complex and implies the adoption of mixed conformations in different environments. The ionic self-complementary peptide KTEAETKTEAKVDAKADVE, derived from the C-domain of CCH, adopts and extended conformation in solution with a high content in β-sheet structure that induces a pH-dependent fibril formation. Freeze drying electron microscopy studies revealed the existence of well ordered amyloid-like fibrils in preparations from both the C-domain and its derivative peptide. Conclusion A number of proteins related with copper homeostasis have a high tendency to form fibrils. The determinants for fibril formation, as well as the possible physiological role are not fully understood. Here we show that the plant exclusive C-domain of the copper metallochaperone CCH has conformational plasticity and forms fibrils at defined experimental conditions. The putative influence of these properties with plant copper delivery will be addressed in the future.

  13. New insight into silica deposition in horsetail (Equisetum arvense

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    Exley Christopher

    2011-07-01

    Full Text Available Abstract Background The horsetails (Equisetum sp are known biosilicifiers though the mechanism underlying silica deposition in these plants remains largely unknown. Tissue extracts from horsetails grown hydroponically and also collected from the wild were acid-digested in a microwave oven and their silica 'skeletons' visualised using the fluor, PDMPO, and fluorescence microscopy. Results Silica deposits were observed in all plant regions from the rhizome through to the stem, leaf and spores. Numerous structures were silicified including cell walls, cell plates, plasmodesmata, and guard cells and stomata at varying stages of differentiation. All of the major sites of silica deposition in horsetail mimicked sites and structures where the hemicellulose, callose is known to be found and these serendipitous observations of the coincidence of silica and callose raised the possibility that callose might be templating silica deposition in horsetail. Hydroponic culture of horsetail in the absence of silicic acid resulted in normal healthy plants which, following acid digestion, showed no deposition of silica anywhere in their tissues. To test the hypothesis that callose might be templating silica deposition in horsetail commercially available callose was mixed with undersaturated and saturated solutions of silicic acid and the formation of silica was demonstrated by fluorimetry and fluorescence microscopy. Conclusions The initiation of silica formation by callose is the first example whereby any biomolecule has been shown to induce, as compared to catalyse, the formation of silica in an undersaturated solution of silicic acid. This novel discovery allowed us to speculate that callose and its associated biochemical machinery could be a missing link in our understanding of biosilicification.

  14. METABOLIC ENGINEERING OF RAFFINOSE-FAMILY OLIGOSACCHARIDES IN THE PHLOEM REVEALS ALTERATIONS IN CARBON PARTITIONING AND ENHANCES RESISTANCE TO GREEN PEACH APHID

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    Te eCao

    2013-07-01

    Full Text Available Many plants employ energized loading strategies to accumulate osmotically-active solutes into the phloem of source organs to accentuate the hydrostatic pressure gradients that drive the flow of water, nutrients and signals from source to sinks. Proton-coupled symport of sugars from the apoplasm into the phloem symplasm is the best studied phloem-loading mechanism. As an alternative, numerous species use a polymer trapping mechanism to load through symplasm: sucrose enters the phloem through specialized plasmodesmata and is converted to raffinose-family oligosaccharides (RFOs which accumulate because of their larger size. In this study, metabolic engineering was used to generate RFOs at the inception of the translocation stream of Arabidopsis thaliana, which loads from the apoplasm and transports predominantly sucrose, and the fate of the sugars throughout the plant determined. Three genes, GALACTINOL SYNTHASE, RAFFINOSE SYNTHASE and STACHYOSE SYNTHASE, were expressed from promoters specific to the companion cells of minor veins. Two transgenic lines homozygous for all three genes (GRS63 and GRS47 were selected for further analysis. Three-week-old plants of both lines had RFO levels approaching 50% of total soluble sugar. RFOs were also identified in exudates from excised leaves of transgenic plants whereas levels were negligible in exudates from wild type (WT leaves. Differences in starch accumulation between WT and GRS63 and GRS47 lines were not observed. Similarly, there were no differences in vegetative growth between WT and engineered plants, but the latter flowered slightly earlier. Finally, since the sugar composition of the translocation stream appeared altered, we tested for an impact on green peach aphid (Myzus persicae Sulzer feeding. When given a choice between WT and transgenic plants, green peach aphids preferred settling on the WT plants. Furthermore, green peach aphid fecundity was lower on the transgenic plants compared to the WT

  15. The Arabidopsis synaptotagmin SYTA regulates the cell-to-cell movement of diverse plant viruses

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    Asako eUchiyama

    2014-11-01

    Full Text Available Synaptotagmins are a large gene family in animals that have been extensively characterized due to their role as calcium sensors to regulate synaptic vesicle exocytosis and endocytosis in neurons, and dense core vesicle exocytosis for hormone secretion from neuroendocrine cells. Thought to be exclusive to animals, synaptotagmins have recently been characterized in Arabidopsis thaliana, in which they comprise a five gene family. Using infectivity and leaf-based functional assays, we have shown that Arabidopsis SYTA regulates endocytosis and marks an endosomal vesicle recycling pathway to regulate movement protein-mediated trafficking of the Begomovirus Cabbage leaf curl virus (CaLCuV and the Tobamovirus Tobacco mosaic virus (TMV through plasmodesmata (Lewis and Lazarowitz, 2010. To determine whether SYTA has a central role in regulating the cell-to-cell trafficking of a wider range of diverse plant viruses, we extended our studies here to examine the role of SYTA in the cell-to-cell movement of additional plant viruses that employ different modes of movement, namely the Potyvirus Turnip mosaic virus (TuMV, the Caulimovirus Cauliflower mosaic virus (CaMV and the Tobamovirus Turnip vein clearing virus (TVCV, which in contrast to TMV does efficiently infect Arabidopsis. We found that both TuMV and TVCV systemic infection, and the cell-to-cell trafficking of the their movement proteins, were delayed in the Arabidopsis Col-0 syta-1 knockdown mutant. In contrast, CaMV systemic infection was not inhibited in syta-1. Our studies show that SYTA is a key regulator of plant virus intercellular movement, being necessary for the ability of diverse cell-to-cell movement proteins encoded by Begomoviruses (CaLCuV MP, Tobamoviruses (TVCV and TMV 30K protein and Potyviruses (TuMV P3N-PIPO to alter PD and thereby mediate virus cell-to-cell spread.

  16. Proteolytic processing of CmPP36, a protein from the cytochrome b(5) reductase family, is required for entry into the phloem translocation pathway.

    Science.gov (United States)

    Xoconostle-Cázares, B; Ruiz-Medrano, R; Lucas, W J

    2000-12-01

    Cucurbita maxima (pumpkin) phloem sap contains a 31 kDa protein that cross-reacts with antibodies directed against the red clover necrotic mosaic virus movement protein (RCNMV MP). Microsequence data from phloem-purified 31 kDa protein were used to isolate a complementary DNA: the open reading frame encodes a 36 kDa protein belonging to the cytochrome b(5) reductase (Cb5R) family; the gene was termed CmPP36. Western analyses established that CmPP36, RCNMV MP and CmPP16 (Xoconostle-Cázares et al., 1999, Science 283, 94-98) are immunologically related, probably due to a common epitope, represented by the NADH(+)-binding domain of CmPP36. An N-terminal 5 kDa membrane-targeting domain is cleaved to produce the 31 kDa Delta N-CmPP36 detected in the phloem sap. Microinjection experiments established that Delta N-CmPP36, but not CmPP36, is able to interact with plasmodesmata to mediate its cell-to-cell transport. Thus, intercellular movement of CmPP36 requires proteolytic processing in the companion cell to produce a soluble, movement-competent, protein. In contrast to RCNMV and CmPP16, Delta N-CmPP36 interacts with but does not mediate the trafficking of RNA. Northern and in situ RT-PCR studies established that CmPP36 mRNA is present in all plant organs, being highly abundant within vascular tissues. In roots of hydroponically grown pumpkin plants, CmPP36 mRNA levels respond to changes in available iron in the culture solution. Finally, enzymatic assays established that both CmPP36 and Delta N-CmPP36 could reduce Fe(3+)-citrate and Fe(3+)-EDTA in the presence of NADH(+). These findings are discussed in terms of the possible roles played by CmPP36 in phloem function.

  17. Cellular and Pectin Dynamics during Abscission Zone Development and Ripe Fruit Abscission of the Monocot Oil Palm

    Science.gov (United States)

    Roongsattham, Peerapat; Morcillo, Fabienne; Fooyontphanich, Kim; Jantasuriyarat, Chatchawan; Tragoonrung, Somvong; Amblard, Philippe; Collin, Myriam; Mouille, Gregory; Verdeil, Jean-Luc; Tranbarger, Timothy J.

    2016-01-01

    The oil palm (Elaeis guineensis Jacq.) fruit primary abscission zone (AZ) is a multi-cell layered boundary region between the pedicel (P) and mesocarp (M) tissues. To examine the cellular processes that occur during the development and function of the AZ cell layers, we employed multiple histological and immunohistochemical methods combined with confocal, electron and Fourier-transform infrared (FT-IR) microspectroscopy approaches. During early fruit development and differentiation of the AZ, the orientation of cell divisions in the AZ was periclinal compared with anticlinal divisions in the P and M. AZ cell wall width increased earlier during development suggesting cell wall assembly occurred more rapidly in the AZ than the adjacent P and M tissues. The developing fruit AZ contain numerous intra-AZ cell layer plasmodesmata (PD), but very few inter-AZ cell layer PD. In the AZ of ripening fruit, PD were less frequent, wider, and mainly intra-AZ cell layer localized. Furthermore, DAPI staining revealed nuclei are located adjacent to PD and are remarkably aligned within AZ layer cells, and remain aligned and intact after cell separation. The polarized accumulation of ribosomes, rough endoplasmic reticulum, mitochondria, and vesicles suggested active secretion at the tip of AZ cells occurred during development which may contribute to the striated cell wall patterns in the AZ cell layers. AZ cells accumulated intracellular pectin during development, which appear to be released and/or degraded during cell separation. The signal for the JIM5 epitope, that recognizes low methylesterified and un-methylesterified homogalacturonan (HG), increased in the AZ layer cell walls prior to separation and dramatically increased on the separated AZ cell surfaces. Finally, FT-IR microspectroscopy analysis indicated a decrease in methylesterified HG occurred in AZ cell walls during separation, which may partially explain an increase in the JIM5 epitope signal. The results obtained

  18. Expression of self-complementary hairpin RNA under the control of the rolC promoter confers systemic disease resistance to plum pox virus without preventing local infection

    Directory of Open Access Journals (Sweden)

    Spena Angelo

    2003-06-01

    Full Text Available Abstract Background Homology-dependent selective degradation of RNA, or post-transcriptional gene silencing (PTGS, is involved in several biological phenomena, including adaptative defense mechanisms against plant viruses. Small interfering RNAs mediate the selective degradation of target RNA by guiding a multicomponent RNAse. Expression of self-complementary hairpin RNAs within two complementary regions separated by an intron elicits PTGS with high efficiency. Plum pox virus (PPV is the etiological agent of sharka disease in Drupaceae, although it can also be transmitted to herbaceous species (e.g. Nicotiana benthamiana. Once inside the plant, PPV is transmitted via plasmodesmata from cell to cell, and at longer distances, via phloem. The rolC promoter drives expression in phloem cells. RolC expression is absent in both epidermal and mesophyll cells. The aim of the present study was to confer systemic disease resistance without preventing local viral infection. Results In the ihprolC-PP197 gene (intron hair pin rolC PPV 197, a 197 bp sequence homologous to the PPV RNA genome (from base 134 to 330 was placed as two inverted repeats separated by the DNA sequence of the rolA intron. This hairpin construct is under the control of the rolC promoter.N. benthamiana plants transgenic for the ihprolC-PP197 gene contain siRNAs homologous to the 197 bp sequence. The transgenic progeny of ihprolC-PP197 plants are resistant to PPV systemic infection. Local infection is unaffected. Most (80% transgenic plants are virus free and symptomless. Some plants (20% contain virus in uninoculated apical leaves; however they show only mild symptoms of leaf mottling. PPV systemic resistance cosegregates with the ihprolC-PP197 transgene and was observed in progeny plants of all independent transgenic lines analyzed. SiRNAs of 23–25 nt homologous to the PPV sequence used in the ihprolC-PP197 construct were detected in transgenic plants before and after inoculation

  19. FUNCTION OF PHLOEM-BORNE INFORMATION MACROMOLECULES IN INTEGRATING PLANT GROWTH & DEVELOPMENT

    Energy Technology Data Exchange (ETDEWEB)

    William J. Lucas

    2012-11-12

    Studies on higher plants have revealed the operation of cell-to-cell and long-distance communication networks that mediate the transport of information macromolecules, such as proteins and RNA. Based on the findings from this DOE-funded project and results from other groups, it is now well established that the enucleate sieve tube system of the angiosperms contains a complex set of proteins including RNA binding proteins as well as a unique population of RNA molecules, comprised of both mRNA and small RNA species. Hetero-grafting experiments demonstrated that delivery of such RNA molecules, into the scion, is highly correlated with changes in developmental phenotypes. Furthermore, over the course of this project, our studies showed that plasmodesmata and the phloem are intimately involved in the local and systemic spread of sequence-specific signals that underlie gene silencing in plants. Major advances were also made in elucidating the underlying mechanisms that operate to mediate the selective entry and exit of proteins and RNA into and out of the phloem translocation stream. Our pioneering studies identified the first plant protein with the capacity to both bind specifically to small RNA molecules (si-RNA) and mediate in the cell-to-cell movement of such siRNA. Importantly, studies conducted with support from this DOE program also yielded a detailed characterization of the first phloem-mobile RNP complex isolated from pumpkin, namely the CmRBP50-RNP complex. This RNP complex was shown to bind, in a sequence-specific manner, to a set of transcripts encoding for transcription factors. The remarkable stability of this CmRBP50-RNP complex allows for long-distance delivery of bound transcripts from mature leaves into developing tissues and organs. Knowledge gained from this project can be used to exert control over the long-distance signaling networks used by plants to integrate their physiological and developmental programs at a whole plant level. Eventually, this

  20. The exogenous particles of heavy metals and/or radionuclide interaction with cellular organelles in Phragmites australis (Cav.) Steudel leaf

    Science.gov (United States)

    Corneanu, Gabriel; Corneanu, Mihaela; Craciun, Constantin; Tripon, Septimiu

    2013-04-01

    Phragmites australis (Cav.) Steudel (reed), is a phytoremediatory species, meet in the swampy areas, being a hypperaccumulator for chromium (Calheiros et al., 2008; Ait Ali et al., 2004, a/o). In nature there are cytotypes with a different somatic chromosome number (6x - 16x), with a good adaptation at various environmental conditions. Weis and Weis (2004) consider that reed is an invasive species, sequester more metals than some native species and recommended to use it, in wetlands, for phytoremediation and marsh restoration. Researches performed by Hakmaoui et al. (2007) regarding the ultrastructural effect of cadmium and cooper on reed, evidenced the presence of the ferritin aggregates in the chloroplast stroma, as well as some reversible modifications in chloroplast. In this paper, the ultrastructural features of the leaf in three Phragmites australis genotypes, from the Middle Jiu river valley (Gorj county, Romania), were analyzed: Control (Ţânţăreni village); a population from neighbourhood of TEPP-Turceni; and other population developed at the basis a sterile waste dump of 40 years-old (near Cocoreni village). The heavy metal and radionuclide content of the soil was different in the three sites, with the lowest values in Control and the highest values for many heavy metals (Zn, Mn, Ni, Co, Cd) and radionuclide's (U-238, Ra-226, Pb-210, Bi-214, Pb-214, U-235, Ac-228, Pb-212, Cs-137) on the sterile waste dump. The analysis of the ultrastructural features of the leaf in mature plants revealed some differences between the three Phragmites australis genotypes. The ultrastructural investigations underlined the adaptation of this species against the stress factors (heavy metals and radionuclides). The exogenous particles penetrated the foliar tissue through the epidermis and stomata, being spread in the cells, at the plasmodesmata level, through endoplasmic reticulum, and through the vascular system. The exogenous particles were present on the endoplasmic

  1. Application of chitosan and chitosan nanoparticles for the control of Fusarium head blight of wheat (Fusarium graminearum) in vitro and greenhouse.

    Science.gov (United States)

    Kheiri, A; Moosawi Jorf, S A; Malihipour, A; Saremi, H; Nikkhah, M

    2016-12-01

    Fusarium head blight (FHB) disease caused by Fusarium graminearum is one of the most important diseases of wheat in humid and warm areas. This disease significantly reduces yield as well as seed quality. The aim of this work was to evaluate the possibility of control of FHB by chitosan (CS) and chitosan nanoparticles (CS/NPs). In vitro, the application of various concentrations of CS and CS/NPs showed significant inhibition of both radial mycelial growth and number of colonies formed against F. graminearum. The application of 1000 and 5000ppm concentration of CS and CS/NPs produced maximum inhibition of radial mycelial growth in comparison to the control, respectively. The microscopic examination, of treated F. graminearum with the CS and CS/NPs, showed dehydration and deformation in mycelial growth and some hyphae were collapsed. The maximum percentage reduction number of colonies was observed in 5000ppm concentration of both CS and CS/NPs. To test the effect of CS and CS/NPs on spore germination, four concentrations were used for 4 and 24h incubation. The 24h incubation of F. graminearum spores with a 5000ppm solution of CS greatly reduced the number of germinating spores. In greenhouse trials, the disease severity percentage was low when CS and CS/NPs were applied before fungus inoculation on the plants and 1000ppm concentration. The spores of F. graminearum germinated on the anther, hyphae penetrated into anther and colonized the palea, lemma and glume after 24 and 72 hpi, respectively. Wherease, the spikelets treated with CS and CS/NPs were infected slowly. Light microscopy and TEM observations indicated that mycelium penetrated into the cells through stoma and transited to other cells by cell wall or plasmodesmata. Mycelial growth caused conidia into cells but CS and CS/NPs prevented of it's growth. Results showed that CS and CS/NPs could be a useful biological pesticide for controlling FHB. Copyright © 2016 Elsevier B.V. All rights reserved.

  2. A photoperiod-responsive protein compendium and conceptual proteome roadmap outline in maize grown in growth chambers with controlled conditions.

    Science.gov (United States)

    Li, You-Zhi; Fan, Xian-Wei; Chen, Qiang; Zhong, Hao

    2017-01-01

    Maize (Zea mays L.) is one of the major staple food crops of the world. However, high photoperiod sensitivity, especially for tropical germplasms, impedes attempts to improve maize agronomical traits by integration of tropical and temperate maize germplasms. Physiological and phenotypic responses of maize to photoperiod have widely been investigated based on multi-site field observations; however, proteome-based responsive mechanisms under controlled photoperiod regimes, nutrient and moisture soils are not yet well understood. In the present study, we sequenced and analyzed six proteomes of tropically-adapted and photoperiod-sensitive M9 inbred line at the vegetative 3 stage and proteomes from tropically-adapted and photoperiod-sensitive Shuang M9 (SM9) inbred line at the vegetative-tasseling stage. All plants were grown in growth chambers with controlled soil and temperature and three photoperiod regimes, a short photoperiod (SP) of 10 h light/14 h dark, a control neutral photoperiod (NP) of 12 h light/12 h dark, and a long photoperiod (LP) of 16 h light/8 h dark for a daily cycle. We identified 4,395 proteins of which 401 and 425 differentially-expressed proteins (DPs) were found in abundance in M9 leaves and in SM9 leaves as per SP/LP vs. NP, respectively. Some DPs showed responses to both SP and LP while some only responded to either SP or LP, depending on M9 or SM9. Our study showed that the photoperiodic response pathway, circadian clock rhythm, and high light density/intensity crosstalk with each other, but apparently differ from dark signaling routes. Photoperiod response involves light-responsive or dark-responsive proteins or both. The DPs positioned on the signaling routes from photoperiod changes to RNA/DNA responses involve the mago nashi homolog and glycine-rich RNA-binding proteins. Moreover, the cell-to-cell movement of ZCN14 through plasmodesmata is likely blocked under a 16-h-light LP. Here, we propose a photoperiodic model based on our findings

  3. Crinivirus replication and host interactions

    Directory of Open Access Journals (Sweden)

    Zsofia A Kiss

    2013-05-01

    Full Text Available Criniviruses comprise one of the genera within the family Closteroviridae. Members in this family are restricted to the phloem and rely on whitefly vectors of the genera Bemisia and/or Trialeurodes for plant-to-plant transmission. All criniviruses have bipartite, positive-sense ssRNA genomes, although there is an unconfirmed report of one having a tripartite genome. Lettuce infectious yellows virus (LIYV is the type species of the genus, the best studied so far of the criniviruses and the first for which a reverse genetics system was available. LIYV RNA 1 encodes for proteins predicted to be involved in replication, and alone is competent for replication in protoplasts. Replication results in accumulation of cytoplasmic vesiculated membranous structures which are characteristic of most studied members of the Closteroviridae. These membranous structures, often referred to as BYV-type vesicles, are likely sites of RNA replication. LIYV RNA 2 is replicated in trans when co-infecting cells with RNA 1, but is temporally delayed relative to RNA1. Efficient RNA 2 replication also is dependent on the RNA 1-encoded RNA binding protein, P34. No LIYV RNA 2-encoded proteins have been shown to affect RNA replication, but at least four, CP, CPm, Hsp70h, and p59 are virion structural components and CPm is a determinant of whitefly transmissibility. Roles of other LIYV RNA 2-encoded proteins are largely as yet unknown, but P26 is a non-virion protein that accumulates in cells as characteristic plasmalemma deposits which in plants are localized within phloem parenchyma and companion cells over plasmodesmata connections to sieve elements. The two remaining crinivirus-conserved RNA 2-encoded proteins are P5 and P9. P5 is 39 amino acid protein and is encoded at the 5’ end of RNA 2 as ORF1 and is part of the hallmark closterovirus gene array. The orthologous gene in BYV has been shown to play a role in cell-to-cell movement and indicated to be localized to the

  4. Discussion on the Problem of Salt Gland of Glycine soja%关于野大豆盐腺问题的探讨

    Institute of Scientific and Technical Information of China (English)

    周三; 赵可夫

    2003-01-01

    Glycine soja Sieb. et Zucc. plants living in saline soil in three provinces of China were treated with different salinity concentrations under different laboratory culture conditions (including solution, sand and field cultivation). The attachment shape and distribution on the surface of stalk and leaf of G. soja plants were observed with scanning electron microscopy (SEM), and the ultrastructure of glandular hair with transmission electron microscopy (TEM). Na+ and Cl- contents in the secretion of the leaf surface and inside the leaf of G. soja subjected to different treatments were measured. The Na+ relative contents in glandular cells, epidermal cells and mesophyllous cells of leaves under different salinities were determined by X-ray microanalysis. Results show that only glandular and epidermal hair exist on the surface attachments of leaves and stalks of G. soja plants. These glandular hair were similar in shape to some salt glands of Gramineae halophytes, and they attached to the vein on the leaf surface. The cell structure of the glandular hair showed the characteristics of common salt glands, such as big vacuoles, dense cytoplasm, a great deal of mitochondria, chloroplast, plasmodesmata and thicker cell walls, etc. The results of Na+ and Cl- contents in the leaf secretion and inside the leaf showed that the glandular hair executed the function of salt-secretion, and when treated with the salt gland inhibitor the salt-secretion process was inhibited. As a result, Na+ and Cl- were mainly accumulated inside G. soja leaves. The results of Na+ X-ray microanalysis under different salinities proved that the three cells of the glandular hair, especially the top cell, possessed strong competence for Na+ accumulation. Above all, the glandular hair were the salt gland, and no other kind of salt glands were found on G. soja plants. The secreting mechanism of the salt gland was also discussed.%以中国3个省的盐生野大豆(Glycine soja Sieb. et Zucc.)为材料,在

  5. Structure and Development of Endosperm Transfer Cells in Wheat%小麦胚乳传递细胞发育的结构观察

    Institute of Scientific and Technical Information of China (English)

    王慧慧; 王峰; 刘大同; 顾蕴洁; 王忠

    2011-01-01

    In developing wheat caryopsis,grain filling nutrients transport into the endosperm via endosperm transfer cells(ETCs).The developmental extent of ETCs is in close relation to yield and qualities of wheat.In this paper we investigated the developmental process and structural features of ETCs in wheat systematically by the combination of light microscopy and transmission electron microscopy.Main results were as follows:(1) ETCs occured in the endosperm epidermis bordering the endosperm cavity and were the first cell type histologically differentiated during endosperm development.ETCs could be divided into two subtypes: outer 1~2 layer of aleurone transfer cells and inner 1~2 layer of starchy endosperm transfer cells.(2) As caryopsis matured,the nuclei of starchy endosperm transfer cells disappeared,while the nuclei of aleurone transfer cells remained intact.(3) The development of ETCs showed obvious polarity and the pattern of temporal and spatial gradient.(4) Aleurone transfer cells had dense cytoplasm rich in rough endoplasmic reticulum,mitochondria,dictyosomes and lipid bodies;their plasma membrane wrinkled and in some region evaginated to form numerous plasmatubules.(5) Starchy endosperm transfer cells had sparse cytoplasm rich in amyloplasts and were highly vacuolated.(6) Lots of plasmodesmata penetrated into adjoining primary walls of ETCs where thickening and wall ingrowths didn't occur.(7) Mitochondria in ETCs showed polarized distribution,and most of them lied in the proximity of plasma membrane.The structural features of ETCs suggested that they may play a role in nutrients transportation into the endosperm both via apoplastic and symplastic pathway.%为从细胞学方面了解小麦产量和品质的形成机制,以扬麦5号为材料,利用光镜和透射电镜观察了小麦颖果发育过程中胚乳传递细胞的结构变化,并探讨了胚乳传递细胞的生理功能。结果表明:(1)胚乳传递细胞

  6. Uptake and Transport of Calcium in Plants%植物钙素吸收和运转

    Institute of Scientific and Technical Information of China (English)

    杨洪强; 接玉玲

    2005-01-01

    近年来,钙素在植物体内的吸收和运输研究主要集中在细胞和分子水平,但整株水平上的研究也同样重要.整株水平上的钙吸收和运输包括根细胞的钙吸收、钙离子横向穿过根系并进入木质部、在木质部运输、从木质部移出并进入叶片或果实及在叶片或果实中运转分配等环节,既经过质外体也穿越共质体.钙离子通道、Ca2+-ATP酶和Ca2+/H+反向转运器等参与根细胞的钙吸收.在钙离子横向穿根进入木质部的过程中,需要穿越内皮层和木质部薄壁细胞组织.根系内皮层凯氏带阻挡了Ca2+沿质外体途径由内皮层外侧向内侧的移动,部分Ca2+由此通过离子通道流进内皮层细胞而转入共质体并到达木质部薄壁细胞组织,而由木质部薄壁细胞组织进入中柱质外体可能需要Ca2+-ATP酶驱动;还有一些Ca2+由内皮层细胞运出,沿内皮层内侧的质外体途径进入木质部导管,并通过导管运向枝干.钙离子以螯合态的形式在枝干导管运输;水流速率是影响钙离子沿导管运输的关键因子.钙离子在果实和叶片中的运输和分配不仅通过质外体途径也通过共质体途径.%Recently, research on Ca2+ transport in plants has been focused on cellular and molecular level.But the uptake, transport and distribution are also very important for calcium to accomplish its function at whole plant level. There are many cells along the way of transport of Ca2+ from root to shoot, and Ca2+ passes either through the cytoplasm of cells linked by plasmodesmata (the symplast) or through the spaces between cells (the apoplast), which include Ca2+ uptake by root cells, Ca2+ transport from root cortex to and through the xylem, and then out of it into leaves or fruits. Ca2+ channels, Ca2+/H+ antiporter and Ca2+-ATPase play roles in the uptake and transport of Ca2+ in root cells. To be transported from root surface to xylem,Ca2+ needs to traverse endodermal cells and

  7. Anatomia e desenvolvimento ontogenético de Coffea arabica L. var. typica Cramer Anatomy and ontogenetical development of Coffea arabica L. var. typica Cramer

    Directory of Open Access Journals (Sweden)

    D. M. Dedecca

    1957-01-01

    storage. With the aid of a special technique plasmodesmata can be detected in the primary-pit-fields of the endosperm cell walls. The endosperm tissue seems to present differences in the structure and chemical composition of its various layers; thus, at the level of the embryo cavity the cells are flattened and elongated constituting a region which probably désintégrâtes during embryo development. The outer layers represented by hard endosperm slough away as a cap that involves the cotyledons of seedlings obtained from completely naked seeds. This cap resembles the seed parchment in gross morphology. The inner layers are considered soft endosperm. As to the chemical composition, the endosperm cells besides Water, contains protein, the alkaloids caféine and coffearine, oil, sugar, dextrins, pentosans, cellulose, caffetannic acids, minerals, various acids and minor constituents. The small embryo, localized at the bottom of the seed, on its convex surface is represented by an hypocotyl and two adherent cordiform cotyledons. Very seldom there is the occurrence of embryo with 3 or 4 cotyledons.