The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Robert Turgeon - One of the best experts on this subject based on the ideXlab platform.
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passive phloem loading and long distance Transport in a synthetic tree on a chip
arXiv: Biological Physics, 2017Co-Authors: Jean Comtet, Robert Turgeon, Kaare H Jensen, Abraham D Stroock, A E HosoiAbstract:Vascular plants rely on differences of osmotic pressure to export sugars from regions of synthesis (mature leaves) to sugar sinks (roots, fruits). In this process, known as Munch pressure flow, the loading of sugars from photosynthetic cells to the export conduit (the phloem) is crucial, as it sets the pressure head necessary to power Long-Distance Transport. Whereas most herbaceous plants use active mechanisms to increase phloem concentration above that of the photosynthetic cells, in most tree species, for which Transport distances are largest, loading seems to occur via passive symplastic diffusion from the mesophyll to the phloem. Here, we use a synthetic microfluidic model of a passive loader to explore the nonlinear dynamics that arise during export and determine the ability of passive loading to drive Long-Distance Transport. We first demonstrate that in our device, phloem concentration is set by the balance between the resistances to diffusive loading from the source and convective export through the phloem. Convection-limited export corresponds to classical models of Munch Transport, where phloem concentration is close to that of the source; in contrast, diffusion-limited export leads to small phloem concentrations and weak scaling of flow rates with the hydraulic resistance. We then show that the effective regime of convection-limited export is predominant in plants with large Transport resistances and low xylem pressures. Moreover, hydrostatic pressures developed in our synthetic passive loader can reach botanically relevant values as high as 10 bars. We conclude that passive loading is sufficient to drive Long-Distance Transport in large plants, and that trees are well suited to take full advantage of passive phloem loading strategies.
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passive phloem loading and long distance Transport in a synthetic tree on a chip
Nature plants, 2017Co-Authors: Jean Comtet, Robert Turgeon, Kaare H Jensen, Abraham D Stroock, A E HosoiAbstract:Vascular plants rely on differences in osmotic pressure to export sugars from regions of synthesis (mature leaves) to sugar sinks (roots, fruits). In this process, known as Munch pressure flow, the loading of sugars from photosynthetic cells to the export conduit (the phloem) is crucial, as it sets the pressure head necessary to power Long-Distance Transport. Whereas most herbaceous plants use active mechanisms to increase phloem sugar concentration above that of the photosynthetic cells, in most tree species, for which Transport distances are largest, loading seems, counterintuitively, to occur by means of passive symplastic diffusion from the mesophyll to the phloem. Here, we use a synthetic microfluidic model of a passive loader to explore the non-linear dynamics that arise during export and determine the ability of passive loading to drive Long-Distance Transport. We first demonstrate that in our device, the phloem concentration is set by the balance between the resistances to diffusive loading from the source and convective export through the phloem. Convection-limited export corresponds to classical models of Munch Transport, where the phloem concentration is close to that of the source; in contrast, diffusion-limited export leads to small phloem concentrations and weak scaling of flow rates with hydraulic resistance. We then show that the effective regime of convection-limited export is predominant in plants with large Transport resistances and low xylem pressures. Moreover, hydrostatic pressures developed in our synthetic passive loader can reach botanically relevant values as high as 10 bars. We conclude that passive loading is sufficient to drive Long-Distance Transport in large plants, and that trees are well suited to take full advantage of passive phloem loading strategies.
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The Role of Phloem Loading Reconsidered
Plant physiology, 2010Co-Authors: Robert TurgeonAbstract:It is generally assumed that the primary role of phloem loading is to drive Long-Distance Transport by elevating hydrostatic pressure in sieve elements. This concept is consistent with the fact that, in many plants, energy is used to increase the concentrations of photoassimilates in the leaf phloem
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symplastic continuity between companion cells and the translocation stream long distance Transport is controlled by retention and retrieval mechanisms in the phloem
Plant Physiology, 2003Co-Authors: Brian G. Ayre, Felix Keller, Robert TurgeonAbstract:Substantial symplastic continuity appears to exist between companion cells (CCs) and sieve elements of the phloem, which suggests that small solutes within the CC are subject to indiscriminate Long-Distance Transport via the translocation stream. To test this hypothesis, the distributions of exotic and endogenous solutes synthesized in the CCs of minor veins were studied. Octopine, a charged molecule derived from arginine and pyruvate, was efficiently Transported through the phloem but was also transferred in substantial amounts to the apoplast, and presumably other non-phloem compartments. The disaccharide galactinol also accumulated in non-phloem compartments, but Long-Distance Transport was limited. Conversely, sucrose, raffinose, and especially stachyose demonstrated reduced accumulation and efficient Transport out of the leaf. We conclude that small metabolites in the cytosol of CCs do enter the translocation stream indiscriminately but are also subject to distributive forces, such as nonselective and carrier-mediated membrane Transport and symplastic dispersal, that may effectively clear a compound from the phloem or retain it for Long-Distance Transport. A model is proposed in which the Transport of oligosaccharides is an adaptive strategy to improve photoassimilate retention, and consequently translocation efficiency, in the phloem.
James C Carrington - One of the best experts on this subject based on the ideXlab platform.
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cell to cell and long distance Transport of viruses in plants
The Plant Cell, 1996Co-Authors: James C Carrington, Kristin D Kasschau, Sunita K Mahajan, Mary C SchaadAbstract:The idea that viruses move through plants in two distinct modes was accurately concluded by G. Samuel in a 1934 paper describing the Transport of tobacco mosaic virus (TMV) through solanaceous hosts: “lt is considered that these facts favour the theory of a slow cell to cell movement of the virus via the plasmodesmen, combined with a rapid distribution through the plant via the phloem” (Samuel, 1934). It is now firmly established that plant viruses move from cell to cell and over long distances by exploiting and modifying preexisting pathways for macromolecular movement within cells, between cells, and between organs. In this review, we focus on the roles of vira1 and host components in the movement of viruses through these pathways. Exhaustive coverage of all aspects of movement is not possible, but the reader is referred to several excellent reviews that emphasize various facets of shortand long-range virus Transport (Atabekov and Taliansky, 1990; Maule, 1991; Deom et al., 1992; Citovsky, 1993; Leisner and Turgeon, 1993; Lucas and Gilbertson, 1994; Lucas, 1995).
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long distance movement factor a Transport function of the potyvirus helper component proteinase
The Plant Cell, 1995Co-Authors: Stephen Cronin, Ruth Haldemancahill, Mary C Schaad, Jeanmarie Verchot, James C CarringtonAbstract:Transport of viruses from cell to cell in plants typically involves one or more viral proteins that supply dedicated movement functions. Transport from leaf to leaf through phloem, or Long-Distance Transport, is a poorly understood process with requirements differing from those of cell-to-cell movement. Through genetic analysis of tobacco etch virus (TEV; potyvirus group), a novel Long-Distance movement factor was identified that facilitates vascular-associated movement in tobacco. A mutation in the central region of the helper component proteinase (HC-Pro), a TEV-encoded protein with previously described activities in aphid-mediated transmission and polyprotein processing, inactivated Long-Distance movement. This mutant virus exhibited only minor defects in genome amplification and cell-to-cell movement functions. In situ histochemical analysis revealed that the mutant was capable of infecting mesophyll, bundle sheath, and phloem cells within inoculated leaves, suggesting that the Long-Distance movement block was associated with entry into or exit from sieve elements. The Long-Distance movement defect was specifically complemented by HC-Pro supplied in trans by a transgenic host. The data indicate that HC-Pro functions in one or more steps unique to Long-Distance Transport.
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capsid protein determinants involved in cell to cell and long distance movement of tobacco etch potyvirus
Virology, 1995Co-Authors: Valerian V Dolja, Ruth Haldemancahill, Amanda E Montgomery, Kathryn A Vandenbosch, James C CarringtonAbstract:Abstract The tobacco etch potyvirus (TEV) capsid protein (CP) is necessary for cell-to-cell and long distance Transport of the virus in plants. In this study, the Transport phenotypes of TEV mutants containing CPs with a substitution of the highly conserved Ser122 (termed S122W) within the core domain, or with a deletion of sequences encoding 17 amino acid residues comprising most of the variable C-terminal domain (ΔC), were analyzed. The S122W and ΔC mutant genomes were amplified to levels comparable to parental virus in protoplasts. The S122W mutant was encapsidation-defective, although in transgenic plants expressing wild-type CP a small number of virions were observed after prolonged incubation. Cells infected by the ΔC mutant produced virions, indicating that the C-terminal domain is not necessary for encapsidation. The mutants exhibited unique defects in cell-to-cell and long distance movement in plants. The S122W mutant was confined to single, primarily inoculated epidermal cells in nontransgenic plants, but the cell-to-cell movement defect was rescued efficiently by transgenic CP. Long distance movement of this mutant was also rescued in transgenic plants, but accumulation in systemically infected tissue was low compared to parental virus. The ΔC mutant exhibited a slow cell-to-cell movement phenotype in inoculated leaves and a complete inability to move systemically in nontransgenic plants. Transgenic CP was able to rescue partially the slow cell-to-cell movement defect of the ΔC mutant, but not the long distance Transport defect. Taken together with previous results, these data suggest that the core domain of TEV CP provides a function essential during cell-to-cell movement and that the variable N- and C-terminal regions exposed on the virion surface are necessary for long distance Transport. In addition, trans-inhibition models are presented to account for the widely differing transgenic complementation efficiencies of the various movement-defective mutants.
Yi Shen - One of the best experts on this subject based on the ideXlab platform.
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RNA Granules Hitchhike on Lysosomes for Long-Distance Transport, Using Annexin A11 as a Molecular Tether.
Cell, 2019Co-Authors: Ya-cheng Liao, Michael S. Fernandopulle, Guozhen Wang, Heejun Choi, Ling Hao, Catherine M. Drerup, Seema Qamar, Jonathon Nixon-abell, Rajan Patel, Yi ShenAbstract:Summary Long-Distance RNA Transport enables local protein synthesis at metabolically-active sites distant from the nucleus. This process ensures an appropriate spatial organization of proteins, vital to polarized cells such as neurons. Here, we present a mechanism for RNA Transport in which RNA granules “hitchhike” on moving lysosomes. In vitro biophysical modeling, live-cell microscopy, and unbiased proximity labeling proteomics reveal that annexin A11 (ANXA11), an RNA granule-associated phosphoinositide-binding protein, acts as a molecular tether between RNA granules and lysosomes. ANXA11 possesses an N-terminal low complexity domain, facilitating its phase separation into membraneless RNA granules, and a C-terminal membrane binding domain, enabling interactions with lysosomes. RNA granule Transport requires ANXA11, and amyotrophic lateral sclerosis (ALS)-associated mutations in ANXA11 impair RNA granule Transport by disrupting their interactions with lysosomes. Thus, ANXA11 mediates neuronal RNA Transport by tethering RNA granules to actively-Transported lysosomes, performing a critical cellular function that is disrupted in ALS.
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RNA Granules Hitchhike on Lysosomes for Long-Distance Transport, Using Annexin A11 as a Molecular Tether
SSRN Electronic Journal, 2019Co-Authors: Ya-cheng Liao, Michael S. Fernandopulle, Guozhen Wang, Heejun Choi, Ling Hao, Catherine M. Drerup, Seema Qamar, Jonathon Nixon-abell, Yi Shen, William MeadowsAbstract:Long-Distance RNA Transport plays a critical role in cells by enabling local protein translation at metabolically-active sites distant from the nucleus. This ensures an appropriate spatial organization of proteins, vital to polarized cells such as neurons. Here, we present a novel mechanism for RNA Transport, in which RNA granules indirectly “hitchhike” on moving lysosomes. In vitro biophysical modeling, live-cell microscopy, and unbiased proteomics reveal that annexin A11 (ANXA11), an RNA granule-associated phosphoinositide-binding protein, acts as an adaptor between RNA granules and lysosomes. ANXA11 possesses an Nterminal low complexity domain, facilitating its phase separation into membraneless RNA granules, and a C-terminal membrane binding domain, enabling interactions with lysosomes. ALS-associated mutations in ANXA11 decrease long-range Transport of RNA granules in neurons by disrupting their docking onto lysosomes. Thus, ANXA11 enables neuronal RNA Transport via lysosomal hitchhiking of RNA granules, performing a critical cellular function that is disrupted in ALS.
Soumaila Pagabeleguem - One of the best experts on this subject based on the ideXlab platform.
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quality of sterile male tsetse after long distance Transport as chilled irradiated pupae
PLOS Neglected Tropical Diseases, 2015Co-Authors: Momar Talla Seck, Soumaila Pagabeleguem, Baba Sall, Marc J B Vreysen, Assane Gueye Fall, Mireille Djimangali Bassene, Therese A R Diouf, Jeanbaptiste Rayaisse, Peter TakacAbstract:Background: Tsetse flies transmit trypanosomes that cause human and African animal trypanosomosis, a debilitating disease of humans (sleeping sickness) and livestock (nagana). An area-wide integrated pest management campaign against Glossina palpalis gambiensis has been implemented in Senegal since 2010 that includes a sterile insect technique (SIT) component. The SIT can only be successful when the sterile males that are destined for release have a flight ability, survival and competitiveness that are as close as possible to that of their wild male counterparts. Methodology/Principal Findings: Tests were developed to assess the quality of G. p. gambiensis males that emerged from pupae that were produced and irradiated in Burkina Faso and Slovakia (irradiation done in Seibersdorf, Austria) and Transported weekly under chilled conditions to Dakar, Senegal. For each consignment a sample of 50 pupae was used for a quality control test (QC group). To assess flight ability, the pupae were put in a cylinder filtering emerged flies that were able to escape the cylinder. The survival of these flyers was thereafter monitored under stress conditions (without feeding). Remaining pupae were emerged and released in the target area of the eradication programme (RF group). The following parameter values were obtained for the QC flies: average emergence rate more than 69%, median survival of 6 days, and average flight ability of more than 35%. The quality protocol was a good proxy of fly quality, explaining a large part of the variances of the examined parameters. Conclusions/Significance: The quality protocol described here will allow the accurate monitoring of the quality of shipped sterile male tsetse used in operational eradication programmes in the framework of the Pan-African Tsetse and Trypanosomosis Eradication Campaign. (Resume d'auteur)
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long distance Transport of irradiated male glossina palpalis gambiensis pupae and its impact on sterile male yield
Parasites & Vectors, 2015Co-Authors: Soumaila Pagabeleguem, Momar Talla Seck, Baba Sall, Marc J B Vreysen, Geoffrey Gimonneau, Assane Gueye Fall, Mireille Djimangali Bassene, Issa SidibeAbstract:Background The application of the sterile insect technique (SIT) requires mass-production of sterile males of good biological quality. The size of the project area will in most cases determine whether it is more cost effective to produce the sterile flies locally (and invest in a mass-rearing facility) or import the sterile flies from a mass-rearing facility that is located in another country. This study aimed at assessing the effect of long distance Transport of sterile male Glossina palpalis gambiensis pupae on adult male fly yield.
Matt Smith - One of the best experts on this subject based on the ideXlab platform.
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concomitant occurrence of anthropogenic air pollutants mineral dust and fungal spores during long distance Transport of ragweed pollen
Environmental Pollution, 2019Co-Authors: łukasz Grewling, Pawel Bogawski, Maciej Kryza, Donat Magyar, Branko Sikoparija, Carsten Ambelas Skjoth, Orsolya Udvardy, Malgorzata Werner, Matt SmithAbstract:Abstract Large-scale synoptic conditions are able to Transport considerable amounts of airborne particles over entire continents by creating substantial air mass movement. This phenomenon is observed in Europe in relation to highly allergenic ragweed (Ambrosia L.) pollen grains that are Transported from populations in Central Europe (mainly the Pannonian Plain and Balkans) to the North. The path taken by atmospheric ragweed pollen often passes through the highly industrialised mining region of Silesia in Southern Poland, considered to be one of the most polluted areas in the EU. It is hypothesized that chemical air pollutants released over Silesia could become mixed with biological material and be Transported to less polluted regions further North. We analysed levels of air pollution during episodes of Long-Distance Transport (LDT) of ragweed pollen to Poland. Results show that, concomitantly with pollen, the concentration of air pollutants with potential health-risk, i.e. SO2, and PM10, have also significantly increased (by 104% and 37%, respectively) in the receptor area (Western Poland). Chemical Transport modelling (EMEP) and air mass back-trajectory analysis (HYSPLIT) showed that potential sources of PM10 include Silesia, as well as mineral dust from the Ukrainian steppe and the Sahara Desert. In addition, atmospheric concentrations of other allergenic biological particles, i.e. Alternaria Nees ex Fr. spores, also increased markedly (by 115%) during LDT episodes. We suggest that the LDT episodes of ragweed pollen over Europe are not a “one-component” phenomenon, but are often related to elevated levels of chemical air pollutants and other biotic and abiotic components (fungal spores and desert dust).
