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Sample records for auxin transport gravity

  1. Critical consideration on the relationship between auxin transport and calcium transients in gravity perception of Arabidopsis seedlings

    Science.gov (United States)

    Toyota, Masatsugu; Furuichi, Takuya; Tatsumi, Hitoshi

    2008-01-01

    Plants regulate their growth and morphogenesis in response to gravity field, known as gravitropism. In the early process of gravitropism, changes in the gravity vector (gravistimulation) are transduced into certain intracellular signals, termed gravity perception. The plant hormone auxin is not only a crucial factor to represent gravitropism but also a potential signaling molecule for gravity perception. Another strong candidate for the signaling molecule is calcium ion of which cytoplasmic concentration ([Ca2+]c) is known to increase in response to gravistimulation. However, relationship between these two factors, say which is in the first place, has been controversial. This issue is addressed here mainly based on recent progress including our latest studies. Gravistimulation by turning plants 180° induced a two-peaked [Ca2+]c-increase lasting for several minutes in Arabidopsis seedlings expressing apoaequorin; only the second peak was sensitive to the gravistimulation. Peak amplitudes of the [Ca2+]c-increase were attenuated by the 10 µM auxin transport inhibitor (TIBA) and vesicle trafficking inhibitor (BFA), whereas the onset time and rate of rise of the second peak were not significantly altered. This result indicates that polar auxin transport is not involved in the initial phase of the second [Ca2+]c-increase. It is likely that the gravi-induced [Ca2+]c-increase constitutes an upstream event of the auxin transport, but may positively be modulated by auxin since its peak amplitude is attenuated by the inhibition of auxin transport. PMID:19513245

  2. Regulation of auxin transport during gravitropism

    Science.gov (United States)

    Rashotte, A.; Brady, S.; Kirpalani, N.; Buer, C.; Muday, G.

    Plants respond to changes in the gravity vector by differential growth across the gravity-stimulated organ. The plant hormone auxin, which is normally basipetally transported, changes in direction and auxin redistribution has been suggested to drive this differential growth or gravitropism. The mechanisms by which auxin transport directionality changes in response to a change in gravity vector are largely unknown. Using the model plant, Arabidopsis thaliana, we have been exploring several regulatory mechanisms that may control auxin transport. Mutations that alter protein phosphorylation suggest that auxin transport in arabidopsis roots may be controlled via phosphorylation and this signal may facilitate gravitropic bending. The protein kinase mutant pinoid (pid9) has reduced auxin transport; whereas the protein phosphatase mutant, rcn1, has elevated transport, suggesting reciprocal regulation of auxin transport by reversible protein phosphorylation. In both of these mutants, the auxin transport defects are accompanied by gravitropic defects, linking phosphorylation signaling to gravity-induced changes in auxin transport. Additionally, auxin transport may be regulated during gravity response by changes in an endogenous auxin efflux inhibitor. Flavonoids, such as quercetin and kaempferol, have been implicated in regulation of auxin transport in vivo and in vitro. Mutants that make no flavonoids have reduced root gravitropic bending. Furthermore, changes in auxin-induced gene expression and flavonoid accumulation patterns have been observed during gravity stimulation. Current studies are examining whether there are spatial and temporal changes in flavonoid accumulation that precede gravitropic bending and whether the absence of these changes are the cause of the altered gravity response in plants with mutations that block flavonoid synthesis. These results support the idea that auxin transport may be regulated during gravity response by several mechanisms including

  3. Auxin Transporters - Why So Many?

    Czech Academy of Sciences Publication Activity Database

    Zažímalová, Eva; Murphy, A. S.; Yang, H.; Hoyerová, Klára; Hošek, Petr

    2010-01-01

    Roč. 2, č. 3 (2010), s. 1-14 ISSN 1943-0264 R&D Projects: GA MŠk(CZ) LC06034 Institutional research plan: CEZ:AV0Z50380511 Keywords : Auxin transporters * auxin carriers * plant development Subject RIV: ED - Physiology Impact factor: 5.371, year: 2010

  4. Maintenance of asymmetric cellular localization of an auxin transport protein through interaction with the actin cytoskeleton

    Science.gov (United States)

    Muday, G. K.

    2000-01-01

    In shoots, polar auxin transport is basipetal (that is, from the shoot apex toward the base) and is driven by the basal localization of the auxin efflux carrier complex. The focus of this article is to summarize the experiments that have examined how the asymmetric distribution of this protein complex is controlled and the significance of this polar distribution. Experimental evidence suggests that asymmetries in the auxin efflux carrier may be established through localized secretion of Golgi vesicles, whereas an attachment of a subunit of the efflux carrier to the actin cytoskeleton may maintain this localization. In addition, the idea that this localization of the efflux carrier may control both the polarity of auxin movement and more globally regulate developmental polarity is explored. Finally, evidence indicating that the gravity vector controls auxin transport polarity is summarized and possible mechanisms for the environmentally induced changes in auxin transport polarity are discussed.

  5. The actin cytoskeleton may control the polar distribution of an auxin transport protein

    Science.gov (United States)

    Muday, G. K.; Hu, S.; Brady, S. R.; Davies, E. (Principal Investigator)

    2000-01-01

    The gravitropic bending of plants has long been linked to the changes in the transport of the plant hormone auxin. To understand the mechanism by which gravity alters auxin movement, it is critical to know how polar auxin transport is initially established. In shoots, polar auxin transport is basipetal (i.e., from the shoot apex toward the base). It is driven by the basal localization of the auxin efflux carrier complex. One mechanism for localizing this efflux carrier complex to the basal membrane may be through attachment to the actin cytoskeleton. The efflux carrier protein complex is believed to consist of several polypeptides, including a regulatory subunit that binds auxin transport inhibitors, such as naphthylphthalamic acid (NPA). Several lines of experimentation have been used to determine if the NPA binding protein interacts with actin filaments. The NPA binding protein has been shown to partition with the actin cytoskeleton during detergent extraction. Agents that specifically alter the polymerization state of the actin cytoskeleton change the amount of NPA binding protein and actin recovered in these cytoskeletal pellets. Actin-affinity columns were prepared with polymers of actin purified from zucchini hypocotyl tissue. NPA binding activity was eluted in a single peak from the actin filament column. Cytochalasin D, which fragments the actin cytoskeleton, was shown to reduce polar auxin transport in zucchini hypocotyls. The interaction of the NPA binding protein with the actin cytoskeleton may localize it in one plane of the plasma membrane, and thereby control the polarity of auxin transport.

  6. Molecular modeling of auxin transport inhibitors

    International Nuclear Information System (INIS)

    Gardner, G.; Black-Schaefer, C.; Bures, M.G.

    1990-01-01

    Molecular modeling techniques have been used to study the chemical and steric properties of auxin transport inhibitors. These bind to a specific site on the plant plasma membrane characterized by its affinity for N-1-naphthylphthalamic acid (NPA). A three-dimensional model was derived from critical features of ligands for the NPA receptor, and a suggested binding conformation is proposed. This model, along with three-dimensional structural searching techniques, was then used to search the Abbott corporate database of chemical structures. Of the 467 compounds that satisfied the search criteria, 77 representative molecules were evaluated for their ability to compete for [ 3 H]NPA binding to corn microsomal membranes. Nineteen showed activity that ranged from 16 to 85% of the maximum NPA binding. Four of the most active of these, from chemical classes not included in the original compound set, also inhibited polar auxin transport through corn coleoptile sections

  7. Species differences in ligand specificity of auxin-controlled elongation and auxin transport: comparing Zea and Vigna

    Science.gov (United States)

    Zhao, Hu; Hertel, Rainer; Ishikawa, Hideo; Evans, Michael L.

    2002-01-01

    The plant hormone auxin affects cell elongation in both roots and shoots. In roots, the predominant action of auxin is to inhibit cell elongation while in shoots auxin, at normal physiological levels, stimulates elongation. The question of whether the primary receptor for auxin is the same in roots and shoots has not been resolved. In addition to its action on cell elongation in roots and shoots, auxin is transported in a polar fashion in both organs. Although auxin transport is well characterized in both roots and shoots, there is relatively little information on the connection, if any, between auxin transport and its action on elongation. In particular, it is not clear whether the protein mediating polar auxin movement is separate from the protein mediating auxin action on cell elongation or whether these two processes might be mediated by one and the same receptor. We examined the identity of the auxin growth receptor in roots and shoots by comparing the response of roots and shoots of the grass Zea mays L. and the legume Vigna mungo L. to indole-3-acetic acid, 2-naphthoxyacetic acid, 4,6-dichloroindoleacetic acid, and 4,7-dichloroindoleacetic acid. We also studied whether or not a single protein might mediate both auxin transport and auxin action by comparing the polar transport of indole-3-acetic acid and 2-naphthoxyacetic acid through segments from Vigna hypocotyls and maize coleoptiles. For all of the assays performed (root elongation, shoot elongation, and polar transport) the action and transport of the auxin derivatives was much greater in the dicots than in the grass species. The preservation of ligand specificity between roots and shoots and the parallels in ligand specificity between auxin transport and auxin action on growth are consistent with the hypothesis that the auxin receptor is the same in roots and shoots and that this protein may mediate auxin efflux as well as auxin action in both organ types.

  8. Use of membrane vesicles as a simplified system for studying auxin transport of auxin: Progress report

    International Nuclear Information System (INIS)

    Goldsmith, M.H.M.

    1986-01-01

    Indoleacetic acid (IAA), the auxin regulating growth, is transported polarly in plants. IAA stimulates a rapid increase in the rate of electrogenic proton secretion by the plasma membrane. This not only increases the magnitude of the pH and electrical gradients providing the driving force for polar auxin transport and uptake of sugars, amino acids and inorganic ions, but, by acidifying the cell wall, also leads to growth. We find that auxin uptake by membrane vesicles isolated from actively growing plant tissues exhibits some of the same properties as by cells: the accumulation depends on the pH gradient, is saturable and specific for auxin, and enhanced by herbicides that inhibit polar auxin transport. We are using accumulation of a radioactive weak acid to quantify the pH gradient and distribution of fluorescent cyanine dyes to monitor the membrane potential. The magnitude of IAA accumulation exceeds that predicted from the pH gradient, and in the absence of a pH gradient, a membrane potential fails to support any auxin accumulation, leading to the conclusion that the transmembrane potential is not a significant driving force for auxin accumulation in this system. Since increasing the external ionic strength decreases saturable auxin accumulation, we are investigating how modifying the surface potential of the vesicles affects the interaction of the amphipathic IAA molecules with the membranes and whether protein modifying reagents affect the saturability and stimulation by NPA. These studies should provide information on the location and function of the auxin binding site and may enable us to identify the solubilized protein. 5 refs

  9. Auxin transport in the evolution of branching forms.

    Science.gov (United States)

    Harrison, C Jill

    2017-07-01

    Contents 545 I. 545 II. 546 III. 546 IV. 548 V. 548 VI. 549 VII. 549 Acknowledgements 549 References 549 SUMMARY: Branching is one of the most striking aspects of land plant architecture, affecting resource acquisition and yield. Polar auxin transport by PIN proteins is a primary determinant of flowering plant branching patterns regulating both branch initiation and branch outgrowth. Several lines of experimental evidence suggest that PIN-mediated polar auxin transport is a conserved regulator of branching in vascular plant sporophytes. However, the mechanisms of branching and auxin transport and relationships between the two are not well known outside the flowering plants, and the paradigm for PIN-regulated branching in flowering plants does not fit bryophyte gametophytes. The evidence reviewed here suggests that divergent auxin transport routes contributed to the diversification of branching forms in distinct land plant lineages. © 2016 The Authors. New Phytologist © 2016 New Phytologist Trust.

  10. Cytokinins and polar transport of auxin in axillary pea buds

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    Petr Kalousek

    2010-01-01

    Full Text Available The influence of cytokinin on auxin transport during release of axillary buds from apical dominance was studied. Expression of auxin-carrier coding genes PsAUX1 (AUXIN RESISTANT 1 and PsPIN1 (PIN-FORMED 1 was explored in axillary buds of the 2nd node of 7-day pea plants (Pisum sativum L. cv. Vladan after decapitation or after exogenous application of benzyladenine (6-benzylaminopurine onto axillary buds of intact plants. Localization of the PsPIN1 protein, the key factor for polar transport of auxin in axillary buds, was visualised by immunohistochemistry. After exogenous application of cytokinin the expression of PsAUX1 and PsPIN1 rapidly increased with a simultaneous rapid decrease in PsDRM1 and PsAD1 expression – genes related to bud dormancy. The same changes in expression were observed after decapitation, however they were markedly slower. The PsPIN1 auxin efflux carrier in the inhibited axillary buds of intact plants was localised in a non-polar manner. After exogenous application of cytokinin gradual polarisation of the PsPIN1 protein occurred on the basal pole of polar auxin transport competent cells. Despite the fact that direct auxin application to buds of intact plants led to an increase in PsAUX1 and PsPIN1 expression, the buds remained dormant (non-growing what was accompanied by persistent expression of the dormancy markers PsDRM1 and PsAD1. The results indicate a possible effect of cytokinins on biosynthesis, and/or transport of auxin in axillary buds and they highlight the importance of auxin-cytokinin crosstalk in the regulation of bud outgrowth after breaking of apical dominance.

  11. Patterning of leaf vein networks by convergent auxin transport pathways.

    Science.gov (United States)

    Sawchuk, Megan G; Edgar, Alexander; Scarpella, Enrico

    2013-01-01

    The formation of leaf vein patterns has fascinated biologists for centuries. Transport of the plant signal auxin has long been implicated in vein patterning, but molecular details have remained unclear. Varied evidence suggests a central role for the plasma-membrane (PM)-localized PIN-FORMED1 (PIN1) intercellular auxin transporter of Arabidopsis thaliana in auxin-transport-dependent vein patterning. However, in contrast to the severe vein-pattern defects induced by auxin transport inhibitors, pin1 mutant leaves have only mild vein-pattern defects. These defects have been interpreted as evidence of redundancy between PIN1 and the other four PM-localized PIN proteins in vein patterning, redundancy that underlies many developmental processes. By contrast, we show here that vein patterning in the Arabidopsis leaf is controlled by two distinct and convergent auxin-transport pathways: intercellular auxin transport mediated by PM-localized PIN1 and intracellular auxin transport mediated by the evolutionarily older, endoplasmic-reticulum-localized PIN6, PIN8, and PIN5. PIN6 and PIN8 are expressed, as PIN1 and PIN5, at sites of vein formation. pin6 synthetically enhances pin1 vein-pattern defects, and pin8 quantitatively enhances pin1pin6 vein-pattern defects. Function of PIN6 is necessary, redundantly with that of PIN8, and sufficient to control auxin response levels, PIN1 expression, and vein network formation; and the vein pattern defects induced by ectopic PIN6 expression are mimicked by ectopic PIN8 expression. Finally, vein patterning functions of PIN6 and PIN8 are antagonized by PIN5 function. Our data define a new level of control of vein patterning, one with repercussions on other patterning processes in the plant, and suggest a mechanism to select cell files specialized for vascular function that predates evolution of PM-localized PIN proteins.

  12. Patterning of leaf vein networks by convergent auxin transport pathways.

    Directory of Open Access Journals (Sweden)

    Megan G Sawchuk

    Full Text Available The formation of leaf vein patterns has fascinated biologists for centuries. Transport of the plant signal auxin has long been implicated in vein patterning, but molecular details have remained unclear. Varied evidence suggests a central role for the plasma-membrane (PM-localized PIN-FORMED1 (PIN1 intercellular auxin transporter of Arabidopsis thaliana in auxin-transport-dependent vein patterning. However, in contrast to the severe vein-pattern defects induced by auxin transport inhibitors, pin1 mutant leaves have only mild vein-pattern defects. These defects have been interpreted as evidence of redundancy between PIN1 and the other four PM-localized PIN proteins in vein patterning, redundancy that underlies many developmental processes. By contrast, we show here that vein patterning in the Arabidopsis leaf is controlled by two distinct and convergent auxin-transport pathways: intercellular auxin transport mediated by PM-localized PIN1 and intracellular auxin transport mediated by the evolutionarily older, endoplasmic-reticulum-localized PIN6, PIN8, and PIN5. PIN6 and PIN8 are expressed, as PIN1 and PIN5, at sites of vein formation. pin6 synthetically enhances pin1 vein-pattern defects, and pin8 quantitatively enhances pin1pin6 vein-pattern defects. Function of PIN6 is necessary, redundantly with that of PIN8, and sufficient to control auxin response levels, PIN1 expression, and vein network formation; and the vein pattern defects induced by ectopic PIN6 expression are mimicked by ectopic PIN8 expression. Finally, vein patterning functions of PIN6 and PIN8 are antagonized by PIN5 function. Our data define a new level of control of vein patterning, one with repercussions on other patterning processes in the plant, and suggest a mechanism to select cell files specialized for vascular function that predates evolution of PM-localized PIN proteins.

  13. S-nitrosylation mediates nitric oxide -auxin crosstalk in auxin signaling and polar auxin transport

    Science.gov (United States)

    Nitric oxide (NO) and auxin phytohormone cross talk has been implicated in plant development and growth. Addition and removal of NO moieties to cysteine residues of proteins, is termed S-nitrosylation and de-nitrosylation, respectively and functions as an on/off switch of protein activity. This dyna...

  14. Inhibition of polar calcium movement and gravitropism in roots treated with auxin-transport inhibitors

    Science.gov (United States)

    Lee, J. S.; Mulkey, T. J.; Evans, M. L.

    1984-01-01

    Primary roots of maize (Zea mays L.) and pea (Pisum sativum L.) exhibit strong positive gravitropism. In both species, gravistimulation induces polar movement of calcium across the root tip from the upper side to the lower side. Roots of onion (Allium cepa L.) are not responsive to gravity and gravistimulation induces little or no polar movement of calcium across the root tip. Treatment of maize or pea roots with inhibitors of auxin transport (morphactin, naphthylphthalamic acid, 2,3,5-triiodobenzoic acid) prevents both gravitropism and gravity-induced polar movement of calcium across the root tip. The results indicate that calcium movement and auxin movement are closely linked in roots and that gravity-induced redistribution of calcium across the root cap may play an important role in the development of gravitropic curvature.

  15. Cell wall pH and auxin transport velocity

    Science.gov (United States)

    Hasenstein, K. H.; Rayle, D.

    1984-01-01

    According to the chemiosmotic polar diffusion hypothesis, auxin pulse velocity and basal secretion should increase with decreasing cell wall pH. Experiments were designed to test this prediction. Avena coleoptile sections were preincubated in either fusicoccin (FC), cycloheximide, pH 4.0, or pH 8.0 buffer and subsequently their polar transport capacities were determined. Relative to controls, FC enhanced auxin (IAA) uptake while CHI and pH 8.0 buffer reduced IAA uptake. Nevertheless, FC reduced IAA pulse velocity while cycloheximide increased velocity. Additional experiments showed that delivery of auxin to receivers is enhanced by increased receiver pH. This phenomenon was overcome by a pretreatment of the tissue with IAA. Our data suggest that while acidic wall pH values facilitate cellular IAA uptake, they do not enhance pulse velocity or basal secretion. These findings are inconsistent with the chemiosmotic hypothesis for auxin transport.

  16. Polar transport in plants mediated by membrane transporters: focus on mechanisms of polar auxin transport.

    Science.gov (United States)

    Naramoto, Satoshi

    2017-12-01

    Directional cell-to-cell transport of functional molecules, called polar transport, enables plants to sense and respond to developmental and environmental signals. Transporters that localize to plasma membranes (PMs) in a polar manner are key components of these systems. PIN-FORMED (PIN) auxin efflux carriers, which are the most studied polar-localized PM proteins, are implicated in the polar transport of auxin that in turn regulates plant development and tropic growth. In this review, the regulatory mechanisms underlying polar localization of PINs, control of auxin efflux activity, and PIN abundance at PMs are considered. Up to date information on polar-localized nutrient transporters that regulate directional nutrient movement from soil into the root vasculature is also discussed. Copyright © 2017 Elsevier Ltd. All rights reserved.

  17. Flavonoids act as negative regulators of auxin transport in vivo in arabidopsis

    Science.gov (United States)

    Brown, D. E.; Rashotte, A. M.; Murphy, A. S.; Normanly, J.; Tague, B. W.; Peer, W. A.; Taiz, L.; Muday, G. K.

    2001-01-01

    Polar transport of the plant hormone auxin controls many aspects of plant growth and development. A number of synthetic compounds have been shown to block the process of auxin transport by inhibition of the auxin efflux carrier complex. These synthetic auxin transport inhibitors may act by mimicking endogenous molecules. Flavonoids, a class of secondary plant metabolic compounds, have been suggested to be auxin transport inhibitors based on their in vitro activity. The hypothesis that flavonoids regulate auxin transport in vivo was tested in Arabidopsis by comparing wild-type (WT) and transparent testa (tt4) plants with a mutation in the gene encoding the first enzyme in flavonoid biosynthesis, chalcone synthase. In a comparison between tt4 and WT plants, phenotypic differences were observed, including three times as many secondary inflorescence stems, reduced plant height, decreased stem diameter, and increased secondary root development. Growth of WT Arabidopsis plants on naringenin, a biosynthetic precursor to those flavonoids with auxin transport inhibitor activity in vitro, leads to a reduction in root growth and gravitropism, similar to the effects of synthetic auxin transport inhibitors. Analyses of auxin transport in the inflorescence and hypocotyl of independent tt4 alleles indicate that auxin transport is elevated in plants with a tt4 mutation. In hypocotyls of tt4, this elevated transport is reversed when flavonoids are synthesized by growth of plants on the flavonoid precursor, naringenin. These results are consistent with a role for flavonoids as endogenous regulators of auxin transport.

  18. Strigolactone Inhibition of Branching Independent of Polar Auxin Transport1[OPEN

    Science.gov (United States)

    Mason, Michael G.; Beveridge, Christine A.

    2015-01-01

    The outgrowth of axillary buds into branches is regulated systemically via plant hormones and the demand of growing shoot tips for sugars. The plant hormone auxin is thought to act via two mechanisms. One mechanism involves auxin regulation of systemic signals, cytokinins and strigolactones, which can move into axillary buds. The other involves suppression of auxin transport/canalization from axillary buds into the main stem and is enhanced by a low sink for auxin in the stem. In this theory, the relative ability of the buds and stem to transport auxin controls bud outgrowth. Here, we evaluate whether auxin transport is required or regulated during bud outgrowth in pea (Pisum sativum). The profound, systemic, and long-term effects of the auxin transport inhibitor N-1-naphthylphthalamic acid had very little inhibitory effect on bud outgrowth in strigolactone-deficient mutants. Strigolactones can also inhibit bud outgrowth in N-1-naphthylphthalamic acid-treated shoots that have greatly diminished auxin transport. Moreover, strigolactones can inhibit bud outgrowth despite a much diminished auxin supply in in vitro or decapitated plants. These findings demonstrate that auxin sink strength in the stem is not important for bud outgrowth in pea. Consistent with alternative mechanisms of auxin regulation of systemic signals, enhanced auxin biosynthesis in Arabidopsis (Arabidopsis thaliana) can suppress branching in yucca1D plants compared with wild-type plants, but has no effect on bud outgrowth in a strigolactone-deficient mutant background. PMID:26111543

  19. The exocyst complex contributes to PIN auxin efflux carrier recycling and polar auxin transport in Arabidopsis

    Czech Academy of Sciences Publication Activity Database

    Drdová, Edita; Synek, Lukáš; Pečenková, Tamara; Hála, Michal; Kulich, I.; Fowler, J.E.; Murphy, A.S.; Žárský, Viktor

    2013-01-01

    Roč. 73, č. 5 (2013), s. 709-719 ISSN 0960-7412 R&D Projects: GA ČR GPP501/11/P853; GA ČR(CZ) GAP305/11/1629; GA MŠk(CZ) LC06034; GA AV ČR KJB600380802 Grant - others:GA MŠk(CZ) ME10033 Institutional research plan: CEZ:AV0Z50380511 Keywords : exocyst * polar auxin transport * PIN recycling Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 6.815, year: 2013

  20. Phosphorylation of conserved PIN motifs directs Arabidopsis PIN1 polarity and auxin transport

    NARCIS (Netherlands)

    Huang, F.; Kemel Zago, M.; Abas, L.; van Marion, A.; Galván-Ampudia, C.S.; Offringa, R.

    2010-01-01

    Polar cell-to-cell transport of auxin by plasma membrane-localized PIN-FORMED (PIN) auxin efflux carriers generates auxin gradients that provide positional information for various plant developmental processes. The apical-basal polar localization of the PIN proteins that determines the direction of

  1. Auxin apical control of the auxin polar transport and its oscillation - a suggested cellular transduction mechanism

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    Tomasz J. Wodzicki

    2014-01-01

    Full Text Available The proposed hypothesis concerns the transduction of auxin molecular signals arriving from the apoplast at the plasma membrane or recognized by the proteineous receptors of the responding cell, to the concentration gradients oscillating in the supracellular space, associated usually with the specific plant growth and differentiation. Acting as an agonist from outside the target cell auxin stimulates in this cell: (1 the liberation of auxin from the cytosolic pool of its conjugates directly into the basipetal efflux; (2 the synthesis of new auxin which restores the cytosolic reserve of auxin conjugates. The functioning of such a system may be effective in a series of processes initiated by the changing concentration of cytosolic calcium. The hypothesis suggests a molecular mechanism for the development and effective operation of the morphogenetic field in the supracellular space of the plant body, such as the field resulting from auxin waves discovered in cambium.

  2. Auxin transport at cellular level: new insights supported by mathematical modelling

    Czech Academy of Sciences Publication Activity Database

    Hošek, Petr; Kubeš, Martin; Laňková, Martina; Dobrev, Petre; Klíma, Petr; Kohoutová, M.; Petrášek, Jan; Hoyerová, Klára; Jiřina, M.; Zažímalová, Eva

    2012-01-01

    Roč. 63, č. 10 (2012), s. 3815-3827 ISSN 0022-0957 R&D Projects: GA MŠk(CZ) LC06034; GA ČR GAP305/11/0797 Institutional research plan: CEZ:AV0Z50380511 Keywords : auxin metabolism * auxin transport * auxin transport inhibitors Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 5.242, year: 2012

  3. Gravistimulation changes expression of genes encoding putative carrier proteins of auxin polar transport in etiolated pea epicotyls

    Science.gov (United States)

    Hoshino, T.; Hitotsubashi, R.; Miyamoto, K.; Tanimoto, E.; Ueda, J.

    STS-95 space experiment has showed that auxin polar transport in etiolated epicotyls of pea (Pisum sativum L. cv. Alaska) seedlings is controlled by gravistimulation. In Arabidopsis thaliana auxin polar transport has considered to be regulated by efflux and influx carrier proteins in plasma membranes, AtPIN1 and AtAUX1, respectively. In order to know how gravistimuli control auxin polar transport in etiolated pea epicotyls at molecular levels, strenuous efforts have been made, resulting in successful isolation of full-length cDNAs of a putative auxin efflux and influx carriers, PsPIN2 and PsAUX1, respectively. Significantly high levels in homology were found on nucleotide and deduced amino acid sequences among PsPIN2, PsPIN1 (accession no. AY222857, Chawla and DeMason, 2003) and AtPINs, and also among PsAUX1, AtAUX1 and their related genes. Phylogenetic analyses based on the deduced amino acid sequences revealed that PsPIN2 belonged to a subclade including AtPIN3, AtPIN4 relating to lateral transport of auxin, while PsPIN1 belonged to the same clade as AtPIN1 relating to auxin polar transport. In the present study, we examined the effects of gravistimuli on the expression of PsPINs and PsAUX1 in etiolated pea seedlings by northern blot analysis. Expression of PsPIN1, PsPIN2 and PsAUX1 in hook region of 3.5-d-old etiolated pea seedlings grown under simulated microgravity conditions on a 3-D clinostat increased as compared with that of the seedlings grown under 1 g conditions. On the other hand, that of PsPIN1 and PsAUX1 in the 1st internode region under simulated microgravity conditions on a 3-D clinostat also increased, while that of PsPIN2 was affected little. These results suggest that expression of PsPIN1, PsPIN2 and PsAUX1 regulating polar/lateral transport of auxin is substantially under the control of gravity. A possible role of PsPINs and PsAUX1 of auxin polar transport in etiolated pea seedlings will also be discussed.

  4. Flux-based transport enhancement as a plausible unifying mechanism for auxin transport in meristem development.

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    Szymon Stoma

    2008-10-01

    Full Text Available Plants continuously generate new organs through the activity of populations of stem cells called meristems. The shoot apical meristem initiates leaves, flowers, and lateral meristems in highly ordered, spiralled, or whorled patterns via a process called phyllotaxis. It is commonly accepted that the active transport of the plant hormone auxin plays a major role in this process. Current hypotheses propose that cellular hormone transporters of the PIN family would create local auxin maxima at precise positions, which in turn would lead to organ initiation. To explain how auxin transporters could create hormone fluxes to distinct regions within the plant, different concepts have been proposed. A major hypothesis, canalization, proposes that the auxin transporters act by amplifying and stabilizing existing fluxes, which could be initiated, for example, by local diffusion. This convincingly explains the organised auxin fluxes during vein formation, but for the shoot apical meristem a second hypothesis was proposed, where the hormone would be systematically transported towards the areas with the highest concentrations. This implies the coexistence of two radically different mechanisms for PIN allocation in the membrane, one based on flux sensing and the other on local concentration sensing. Because these patterning processes require the interaction of hundreds of cells, it is impossible to estimate on a purely intuitive basis if a particular scenario is plausible or not. Therefore, computational modelling provides a powerful means to test this type of complex hypothesis. Here, using a dedicated computer simulation tool, we show that a flux-based polarization hypothesis is able to explain auxin transport at the shoot meristem as well, thus providing a unifying concept for the control of auxin distribution in the plant. Further experiments are now required to distinguish between flux-based polarization and other hypotheses.

  5. Acropetal Auxin Transport Inhibition Is Involved in Indeterminate But Not Determinate Nodule Formation

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    Jason L. P. Ng

    2018-02-01

    Full Text Available Legumes enter into a symbiotic relationship with nitrogen-fixing rhizobia, leading to nodule development. Two main types of nodules have been widely studied, indeterminate and determinate, which differ in the location of the first cell division in the root cortex, and persistency of the nodule meristem. Here, we compared the control of auxin transport, content, and response during the early stages of indeterminate and determinate nodule development in the model legumes Medicago truncatula and Lotus japonicus, respectively, to investigate whether differences in auxin transport control could explain the differences in the location of cortical cell divisions. While auxin responses were activated in dividing cortical cells during nodulation of both nodule types, auxin (indole-3-acetic acid content at the nodule initiation site was transiently increased in M. truncatula, but transiently reduced in L. japonicus. Root acropetal auxin transport was reduced in M. truncatula at the very start of nodule initiation, in contrast to a prolonged increase in acropetal auxin transport in L. japonicus. The auxin transport inhibitors 2,3,5-triiodobenzoic acid and 1-N-naphthylphthalamic acid (NPA only induced pseudonodules in legume species forming indeterminate nodules, but failed to elicit such structures in a range of species forming determinate nodules. The development of these pseudonodules in M. truncatula exhibited increased auxin responses in a small primordium formed from the pericycle, endodermis, and inner cortex, similar to rhizobia-induced nodule primordia. In contrast, a diffuse cortical auxin response and no associated cortical cell divisions were found in L. japonicus. Collectively, we hypothesize that a step of acropetal auxin transport inhibition is unique to the process of indeterminate nodule development, leading to auxin responses in pericycle, endodermis, and inner cortex cells, while increased auxin responses in outer cortex cells likely

  6. ZIFL1.1 transporter modulates polar auxin transport by stabilizing membrane abundance of multiple PINs in Arabidopsis root tip

    Science.gov (United States)

    Remy, Estelle; Baster, Pawel; Friml, Jiří; Duque, Paula

    2013-01-01

    Cell-to-cell directional flow of the phytohormone auxin is primarily established by polar localization of the PIN auxin transporters, a process tightly regulated at multiple levels by auxin itself. We recently reported that, in the context of strong auxin flows, activity of the vacuolar ZIFL1.1 transporter is required for fine-tuning of polar auxin transport rates in the Arabidopsis root. In particular, ZIFL1.1 function protects plasma-membrane stability of the PIN2 carrier in epidermal root tip cells under conditions normally triggering PIN2 degradation. Here, we show that ZIFL1.1 activity at the root tip also promotes PIN1 plasma-membrane abundance in central cylinder cells, thus supporting the notion that ZIFL1.1 acts as a general positive modulator of polar auxin transport in roots. PMID:23857365

  7. TWISTED DWARF1 Mediates the Action of Auxin Transport Inhibitors on Actin Cytoskeleton Dynamics

    Science.gov (United States)

    Bailly, Aurelien; Zwiewka, Marta; Sovero, Valpuri; Ge, Pei; Aryal, Bibek; Hao, Pengchao; Linnert, Miriam; Burgardt, Noelia Inés; Lücke, Christian; Weiwad, Matthias; Michel, Max; Weiergräber, Oliver H.; Pollmann, Stephan; Azzarello, Elisa; Fukao, Yoichiro; Hoffmann, Céline; Wedlich-Söldner, Roland

    2016-01-01

    Plant growth and architecture is regulated by the polar distribution of the hormone auxin. Polarity and flexibility of this process is provided by constant cycling of auxin transporter vesicles along actin filaments, coordinated by a positive auxin-actin feedback loop. Both polar auxin transport and vesicle cycling are inhibited by synthetic auxin transport inhibitors, such as 1-N-naphthylphthalamic acid (NPA), counteracting the effect of auxin; however, underlying targets and mechanisms are unclear. Using NMR, we map the NPA binding surface on the Arabidopsis thaliana ABCB chaperone TWISTED DWARF1 (TWD1). We identify ACTIN7 as a relevant, although likely indirect, TWD1 interactor, and show TWD1-dependent regulation of actin filament organization and dynamics and that TWD1 is required for NPA-mediated actin cytoskeleton remodeling. The TWD1-ACTIN7 axis controls plasma membrane presence of efflux transporters, and as a consequence act7 and twd1 share developmental and physiological phenotypes indicative of defects in auxin transport. These can be phenocopied by NPA treatment or by chemical actin (de)stabilization. We provide evidence that TWD1 determines downstream locations of auxin efflux transporters by adjusting actin filament debundling and dynamizing processes and mediating NPA action on the latter. This function appears to be evolutionary conserved since TWD1 expression in budding yeast alters actin polarization and cell polarity and provides NPA sensitivity. PMID:27053424

  8. N-MYC DOWN-REGULATED-LIKE Proteins Regulate Meristem Initiation by Modulating Auxin Transport and MAX2 Expression

    OpenAIRE

    Mudgil, Yashwanti; Ghawana, Sanjay; Jones, Alan M.

    2013-01-01

    Background N-MYC DOWN-REGULATED-LIKE (NDL) proteins interact with the G? subunit (AGB1) of the heterotrimeric G protein complex and play an important role in AGB1-dependent regulation of lateral root formation by affecting root auxin transport, auxin gradients and the steady-state levels of mRNA encoding the PIN-FORMED 2 and AUXIN 1 auxin transport facilitators. Auxin transport in aerial tissue follows different paths and utilizes different transporters than in roots; therefore, in the presen...

  9. The microtubule cytoskeleton does not integrate auxin transport and gravitropism in maize roots

    Science.gov (United States)

    Hasenstein, K. H.; Blancaflor, E. B.; Lee, J. S.

    1999-01-01

    The Cholodny-Went hypothesis of gravitropism suggests that the graviresponse is controlled by the distribution of auxin. However, the mechanism of auxin transport during the graviresponse of roots is still unresolved. To determine whether the microtubule (MT) cytoskeleton is participating in auxin transport, the cytoskeleton was examined and the movement of 3H-IAA measured in intact and excised taxol, oryzalin, and naphthylphthalamic acid (NPA)-treated roots of Zea mays cv. Merit. Taxol and oryzalin did not inhibit the graviresponse of roots but the auxin transport inhibitor NPA greatly inhibited both auxin transport and graviresponse. NPA had no effect on MT organization in vertical roots, but caused MT reorientation in horizontally placed roots. Regardless of treatment, the organization of MTs in intact roots differed from that in root segments. The MT inhibitors, taxol and oryzalin had opposite effects on the MTs, namely, depolymerization (oryzalin) and stabilization and thickening (taxol), but both treatments caused swelling of the roots. The data indicate that the MT cytoskeleton does not directly interfere with auxin transport or auxin-mediated growth responses in maize roots.

  10. myo-Inositol-1-phosphate synthase is required for polar auxin transport and organ development

    KAUST Repository

    Chen, Hao; Xiong, Liming

    2010-01-01

    , cotyledon venation patterning, root growth, and root cap development. The mutant roots are also agravitropic and have reduced basipetal auxin transport. mips1 mutants have significantly reduced levels of major phosphatidylinositols and exhibit much slower

  11. Simulation of organ patterning on the floral meristem using a polar auxin transport model.

    Directory of Open Access Journals (Sweden)

    Simon van Mourik

    Full Text Available An intriguing phenomenon in plant development is the timing and positioning of lateral organ initiation, which is a fundamental aspect of plant architecture. Although important progress has been made in elucidating the role of auxin transport in the vegetative shoot to explain the phyllotaxis of leaf formation in a spiral fashion, a model study of the role of auxin transport in whorled organ patterning in the expanding floral meristem is not available yet. We present an initial simulation approach to study the mechanisms that are expected to play an important role. Starting point is a confocal imaging study of Arabidopsis floral meristems at consecutive time points during flower development. These images reveal auxin accumulation patterns at the positions of the organs, which strongly suggests that the role of auxin in the floral meristem is similar to the role it plays in the shoot apical meristem. This is the basis for a simulation study of auxin transport through a growing floral meristem, which may answer the question whether auxin transport can in itself be responsible for the typical whorled floral pattern. We combined a cellular growth model for the meristem with a polar auxin transport model. The model predicts that sepals are initiated by auxin maxima arising early during meristem outgrowth. These form a pre-pattern relative to which a series of smaller auxin maxima are positioned, which partially overlap with the anlagen of petals, stamens, and carpels. We adjusted the model parameters corresponding to properties of floral mutants and found that the model predictions agree with the observed mutant patterns. The predicted timing of the primordia outgrowth and the timing and positioning of the sepal primordia show remarkable similarities with a developing flower in nature.

  12. Parasitic nematodes modulate PIN-mediated auxin transport to facilitate infection.

    Directory of Open Access Journals (Sweden)

    Wim Grunewald

    2009-01-01

    Full Text Available Plant-parasitic nematodes are destructive plant pathogens that cause significant yield losses. They induce highly specialized feeding sites (NFS in infected plant roots from which they withdraw nutrients. In order to establish these NFS, it is thought that the nematodes manipulate the molecular and physiological pathways of their hosts. Evidence is accumulating that the plant signalling molecule auxin is involved in the initiation and development of the feeding sites of sedentary plant-parasitic nematodes. Intercellular transport of auxin is essential for various aspects of plant growth and development. Here, we analysed the spatial and temporal expression of PIN auxin transporters during the early events of NFS establishment using promoter-GUS/GFP fusion lines. Additionally, single and double pin mutants were used in infection studies to analyse the role of the different PIN proteins during cyst nematode infection. Based on our results, we postulate a model in which PIN1-mediated auxin transport is needed to deliver auxin to the initial syncytial cell, whereas PIN3 and PIN4 distribute the accumulated auxin laterally and are involved in the radial expansion of the NFS. Our data demonstrate that cyst nematodes are able to hijack the auxin distribution network in order to facilitate the infection process.

  13. Parasitic nematodes modulate PIN-mediated auxin transport to facilitate infection.

    Science.gov (United States)

    Grunewald, Wim; Cannoot, Bernard; Friml, Jirí; Gheysen, Godelieve

    2009-01-01

    Plant-parasitic nematodes are destructive plant pathogens that cause significant yield losses. They induce highly specialized feeding sites (NFS) in infected plant roots from which they withdraw nutrients. In order to establish these NFS, it is thought that the nematodes manipulate the molecular and physiological pathways of their hosts. Evidence is accumulating that the plant signalling molecule auxin is involved in the initiation and development of the feeding sites of sedentary plant-parasitic nematodes. Intercellular transport of auxin is essential for various aspects of plant growth and development. Here, we analysed the spatial and temporal expression of PIN auxin transporters during the early events of NFS establishment using promoter-GUS/GFP fusion lines. Additionally, single and double pin mutants were used in infection studies to analyse the role of the different PIN proteins during cyst nematode infection. Based on our results, we postulate a model in which PIN1-mediated auxin transport is needed to deliver auxin to the initial syncytial cell, whereas PIN3 and PIN4 distribute the accumulated auxin laterally and are involved in the radial expansion of the NFS. Our data demonstrate that cyst nematodes are able to hijack the auxin distribution network in order to facilitate the infection process.

  14. Overexpression of the Auxin Binding PROTEIN1 Modulates PIN-Dependent Auxin Transport in Tobacco Cells

    Czech Academy of Sciences Publication Activity Database

    Čovanová, Milada; Sauer, M.; Rychtář, J.; Friml, J.; Petrášek, Jan; Zažímalová, Eva

    2013-01-01

    Roč. 8, č. 7 (2013) E-ISSN 1932-6203 R&D Projects: GA ČR(CZ) GAP305/11/0797; GA ČR(CZ) GPP501/12/P951 Institutional research plan: CEZ:AV0Z50380511 Keywords : ZEA - MAYS -L * PLANT HORMONE AUXIN * MEMBRANE H+-ATPASE Subject RIV: ED - Physiology Impact factor: 3.534, year: 2013

  15. Flavonoids and Auxin Transport Inhibitors Rescue Symbiotic Nodulation in the Medicago truncatula Cytokinin Perception Mutant cre1

    Science.gov (United States)

    Ng, Jason Liang Pin; Hassan, Samira; Truong, Thy T.; Hocart, Charles H.; Laffont, Carole; Frugier, Florian; Mathesius, Ulrike

    2015-01-01

    Initiation of symbiotic nodules in legumes requires cytokinin signaling, but its mechanism of action is largely unknown. Here, we tested whether the failure to initiate nodules in the Medicago truncatula cytokinin perception mutant cre1 (cytokinin response1) is due to its altered ability to regulate auxin transport, auxin accumulation, and induction of flavonoids. We found that in the cre1 mutant, symbiotic rhizobia cannot locally alter acro- and basipetal auxin transport during nodule initiation and that these mutants show reduced auxin (indole-3-acetic acid) accumulation and auxin responses compared with the wild type. Quantification of flavonoids, which can act as endogenous auxin transport inhibitors, showed a deficiency in the induction of free naringenin, isoliquiritigenin, quercetin, and hesperetin in cre1 roots compared with wild-type roots 24 h after inoculation with rhizobia. Coinoculation of roots with rhizobia and the flavonoids naringenin, isoliquiritigenin, and kaempferol, or with the synthetic auxin transport inhibitor 2,3,5,-triiodobenzoic acid, rescued nodulation efficiency in cre1 mutants and allowed auxin transport control in response to rhizobia. Our results suggest that CRE1-dependent cytokinin signaling leads to nodule initiation through the regulation of flavonoid accumulation required for local alteration of polar auxin transport and subsequent auxin accumulation in cortical cells during the early stages of nodulation. PMID:26253705

  16. Comprehensive analysis of the soybean (Glycine max GmLAX auxin transporter gene family

    Directory of Open Access Journals (Sweden)

    Chenglin eChai

    2016-03-01

    Full Text Available The phytohormone auxin plays a critical role in regulation of plant growth and development as well as plant responses to abiotic stresses. This is mainly achieved through its uneven distribution in plants via a polar auxin transport process. Auxin transporters are major players in polar auxin transport. The AUXIN RESISTANT 1 ⁄ LIKE AUX1 (AUX⁄LAX auxin influx carriers belong to the amino acid permease family of proton-driven transporters and function in the uptake of indole-3-acetic acid (IAA. In this study, genome-wide comprehensive analysis of the soybean AUX⁄LAX (GmLAX gene family, including phylogenic relationships, chromosome localization, and gene structure, were carried out. A total of 15 GmLAX genes, including seven duplicated gene pairs, were identified in the soybean genome. They were distributed on 10 chromosomes. Despite their higher percentage identities at the protein level, GmLAXs exhibited versatile tissue-specific expression patterns, indicating coordinated functioning during plant growth and development. Most GmLAXs were responsive to drought and dehydration stresses and auxin and abscisic acid (ABA stimuli, in a tissue- and/or time point- sensitive mode. Several GmLAX members were involved in responding to salt stress. Sequence analysis revealed that promoters of GmLAXs contained different combinations of stress-related cis-regulatory elements. These studies suggest that the soybean GmLAXs were under control of a very complex regulatory network, responding to various internal and external signals. This study helps to identity candidate GmLAXs for further analysis of their roles in soybean development and adaption to adverse environments.

  17. Excessive Cellular S-nitrosothiol Impairs Endocytosis of Auxin Efflux Transporter PIN2

    Directory of Open Access Journals (Sweden)

    Min Ni

    2017-11-01

    Full Text Available S-nitrosoglutathione reductase (GSNOR1 is the key enzyme that regulates cellular levels of S-nitrosylation across kingdoms. We have previously reported that loss of GSNOR1 resulted in impaired auxin signaling and compromised auxin transport in Arabidopsis, leading to the auxin-related morphological phenotypes. However, the molecular mechanism underpinning the compromised auxin transport in gsnor1-3 mutant is still unknown. Endocytosis of plasma-membrane (PM-localized efflux PIN proteins play critical roles in auxin transport. Therefore, we investigate whether loss of GSNOR1 function has any effects on the endocytosis of PIN-FORMED (PIN proteins. It was found that the endocytosis of either the endogenous PIN2 or the transgenically expressed PIN2-GFP was compromised in the root cells of gsnor1-3 seedlings relative to Col-0. The internalization of PM-associated PIN2 or PIN2-GFP into Brefeldin A (BFA bodies was significantly reduced in gsnor1-3 upon BFA treatment in a manner independent of de novo protein synthesis. In addition, the exogenously applied GSNO not only compromised the endocytosis of PIN2-GFP but also inhibited the root elongation in a concentration-dependent manner. Taken together, our results indicate that, besides the reduced PIN2 level, one or more compromised components in the endocytosis pathway could account for the reduced endocytosis of PIN2 in gsnor1-3.

  18. Regulation of ABCB1/PGP1-catalysed auxin transport by linker phosphorylation

    DEFF Research Database (Denmark)

    Henrichs, Sina; Wang, Bangjun; Fukao, Yoichiro

    2012-01-01

    Polar transport of the plant hormone auxin is controlled by PIN-and ABCB/PGP-efflux catalysts. PIN polarity is regulated by the AGC protein kinase, PINOID (PID), while ABCB activity was shown to be dependent on interaction with the FKBP42, TWISTED DWARF1 (TWD1). Using co-immunoprecipitation (co-I...

  19. Auxin uptake, transport and accumulation in relation to rooting and ageing of mung bean cuttings

    International Nuclear Information System (INIS)

    Jarvis, B.C.; Shaheed, A.I.

    1986-01-01

    The rooting response of mung bean cuttings (Phaseolus aureus Roxb. cv. Berkin) to indoleacetic acid (IAA) progressively declined when they were aged in water prior to auxin treatment. With increased duration of the ageing period the uptake of basally-supplied auxin by cuttings decreased. This correlated with diminished transpiration. Notwithstanding this decline in the uptake of IAA, a decreasing proportion of the acquired auxin was transported acropetally out of the hypocotyl with increasing age of the cuttings. Recovery of 14 C from cuttings 24 h after the foliar application of 14 C-IAA declined with increasing age of the cuttings. Furthermore, the total amount of radioactivity recovered in the hypocotyl diminished as a function of the increasing age of cuttings, as did the proportion of radioactivity located in the hypocotyl. (author)

  20. The arabidopsis thaliana AGRAVITROPIC 1 gene encodes a component of the polar-auxin-transport efflux carrier

    Science.gov (United States)

    Chen, R.; Hilson, P.; Sedbrook, J.; Rosen, E.; Caspar, T.; Masson, P. H.

    1998-01-01

    Auxins are plant hormones that mediate many aspects of plant growth and development. In higher plants, auxins are polarly transported from sites of synthesis in the shoot apex to their sites of action in the basal regions of shoots and in roots. Polar auxin transport is an important aspect of auxin functions and is mediated by cellular influx and efflux carriers. Little is known about the molecular identity of its regulatory component, the efflux carrier [Estelle, M. (1996) Current Biol. 6, 1589-1591]. Here we show that mutations in the Arabidopsis thaliana AGRAVITROPIC 1 (AGR1) gene involved in root gravitropism confer increased root-growth sensitivity to auxin and decreased sensitivity to ethylene and an auxin transport inhibitor, and cause retention of exogenously added auxin in root tip cells. We used positional cloning to show that AGR1 encodes a putative transmembrane protein whose amino acid sequence shares homologies with bacterial transporters. When expressed in Saccharomyces cerevisiae, AGR1 promotes an increased efflux of radiolabeled IAA from the cells and confers increased resistance to fluoro-IAA, a toxic IAA-derived compound. AGR1 transcripts were localized to the root distal elongation zone, a region undergoing a curvature response upon gravistimulation. We have identified several AGR1-related genes in Arabidopsis, suggesting a global role of this gene family in the control of auxin-regulated growth and developmental processes.

  1. N-MYC down-regulated-like proteins regulate meristem initiation by modulating auxin transport and MAX2 expression.

    Science.gov (United States)

    Mudgil, Yashwanti; Ghawana, Sanjay; Jones, Alan M

    2013-01-01

    N-MYC down-regulated-like (NDL) proteins interact with the Gβ subunit (AGB1) of the heterotrimeric G protein complex and play an important role in AGB1-dependent regulation of lateral root formation by affecting root auxin transport, auxin gradients and the steady-state levels of mRNA encoding the PIN-FORMED 2 and AUXIN 1 auxin transport facilitators. Auxin transport in aerial tissue follows different paths and utilizes different transporters than in roots; therefore, in the present study, we analyzed whether NDL proteins play an important role in AGB1-dependent, auxin-mediated meristem development. Expression levels of NDL gene family members need to be tightly regulated, and altered expression (both over-expression and down-regulation) confers ectopic growth. Over-expression of NDL1 disrupts vegetative and reproductive organ development. Reduced expression of the NDL gene family members results in asymmetric leaf emergence, twinning of rosette leaves, defects in leaf formation, and abnormal silique distribution. Reduced expression of the NDL genes in the agb1-2 (null allele) mutant rescues some of the abnormal phenotypes, such as silique morphology, silique distribution, and peduncle angle, suggesting that proper levels of NDL proteins are maintained by AGB1. We found that all of these abnormal aerial phenotypes due to altered NDL expression were associated with increases in basipetal auxin transport, altered auxin maxima and altered MAX2 expression within the inflorescence stem. NDL proteins, together with AGB1, act as positive regulators of meristem initiation and branching. AGB1 and NDL1 positively regulate basipetal inflorescence auxin transport and modulate MAX2 expression in shoots, which in turn regulates organ and lateral meristem formation by the establishment and maintenance of auxin gradients.

  2. N-MYC down-regulated-like proteins regulate meristem initiation by modulating auxin transport and MAX2 expression.

    Directory of Open Access Journals (Sweden)

    Yashwanti Mudgil

    Full Text Available N-MYC down-regulated-like (NDL proteins interact with the Gβ subunit (AGB1 of the heterotrimeric G protein complex and play an important role in AGB1-dependent regulation of lateral root formation by affecting root auxin transport, auxin gradients and the steady-state levels of mRNA encoding the PIN-FORMED 2 and AUXIN 1 auxin transport facilitators. Auxin transport in aerial tissue follows different paths and utilizes different transporters than in roots; therefore, in the present study, we analyzed whether NDL proteins play an important role in AGB1-dependent, auxin-mediated meristem development.Expression levels of NDL gene family members need to be tightly regulated, and altered expression (both over-expression and down-regulation confers ectopic growth. Over-expression of NDL1 disrupts vegetative and reproductive organ development. Reduced expression of the NDL gene family members results in asymmetric leaf emergence, twinning of rosette leaves, defects in leaf formation, and abnormal silique distribution. Reduced expression of the NDL genes in the agb1-2 (null allele mutant rescues some of the abnormal phenotypes, such as silique morphology, silique distribution, and peduncle angle, suggesting that proper levels of NDL proteins are maintained by AGB1. We found that all of these abnormal aerial phenotypes due to altered NDL expression were associated with increases in basipetal auxin transport, altered auxin maxima and altered MAX2 expression within the inflorescence stem.NDL proteins, together with AGB1, act as positive regulators of meristem initiation and branching. AGB1 and NDL1 positively regulate basipetal inflorescence auxin transport and modulate MAX2 expression in shoots, which in turn regulates organ and lateral meristem formation by the establishment and maintenance of auxin gradients.

  3. The Shape of an Auxin Pulse, and What It Tells Us about the Transport Mechanism.

    Directory of Open Access Journals (Sweden)

    Graeme Mitchison

    2015-10-01

    Full Text Available Auxin underlies many processes in plant development and physiology, and this makes it of prime importance to understand its movements through plant tissues. In stems and coleoptiles, classic experiments showed that the peak region of a pulse of radio-labelled auxin moves at a roughly constant velocity down a stem or coleoptile segment. As the pulse moves it becomes broader, at a roughly constant rate. It is shown here that this 'spreading rate' is larger than can be accounted for by a single channel model, but can be explained by coupling of channels with differing polar transport rates. An extreme case is where strongly polar channels are coupled to completely apolar channels, in which case auxin in the apolar part is 'dragged along' by the polar part in a somewhat diffuse distribution. The behaviour of this model is explored, together with others that can account for the experimentally observed spreading rates. It is also shown that saturation of carriers involved in lateral transport can explain the characteristic shape of pulses that result from uptake of large amounts of auxin.

  4. Arabidopsis N-MYC DOWNREGULATED-LIKE1, a positive regulator of auxin transport in a G protein-mediated pathway.

    Science.gov (United States)

    Mudgil, Yashwanti; Uhrig, Joachm F; Zhou, Jiping; Temple, Brenda; Jiang, Kun; Jones, Alan M

    2009-11-01

    Root architecture results from coordinated cell division and expansion in spatially distinct cells of the root and is established and maintained by gradients of auxin and nutrients such as sugars. Auxin is transported acropetally through the root within the central stele and then, upon reaching the root apex, auxin is transported basipetally through the outer cortical and epidermal cells. The two Gbetagamma dimers of the Arabidopsis thaliana heterotrimeric G protein complex are differentially localized to the central and cortical tissues of the Arabidopsis roots. A null mutation in either the single beta (AGB1) or the two gamma (AGG1 and AGG2) subunits confers phenotypes that disrupt the proper architecture of Arabidopsis roots and are consistent with altered auxin transport. Here, we describe an evolutionarily conserved interaction between AGB1/AGG dimers and a protein designated N-MYC DOWNREGULATED-LIKE1 (NDL1). The Arabidopsis genome encodes two homologs of NDL1 (NDL2 and NDL3), which also interact with AGB1/AGG1 and AGB1/AGG2 dimers. We show that NDL proteins act in a signaling pathway that modulates root auxin transport and auxin gradients in part by affecting the levels of at least two auxin transport facilitators. Reduction of NDL family gene expression and overexpression of NDL1 alter root architecture, auxin transport, and auxin maxima. AGB1, auxin, and sugars are required for NDL1 protein stability in regions of the root where auxin gradients are established; thus, the signaling mechanism contains feedback loops.

  5. Enquiry into the Topology of Plasma Membrane-Localized PIN Auxin Transport Components.

    Science.gov (United States)

    Nodzyński, Tomasz; Vanneste, Steffen; Zwiewka, Marta; Pernisová, Markéta; Hejátko, Jan; Friml, Jiří

    2016-11-07

    Auxin directs plant ontogenesis via differential accumulation within tissues depending largely on the activity of PIN proteins that mediate auxin efflux from cells and its directional cell-to-cell transport. Regardless of the developmental importance of PINs, the structure of these transporters is poorly characterized. Here, we present experimental data concerning protein topology of plasma membrane-localized PINs. Utilizing approaches based on pH-dependent quenching of fluorescent reporters combined with immunolocalization techniques, we mapped the membrane topology of PINs and further cross-validated our results using available topology modeling software. We delineated the topology of PIN1 with two transmembrane (TM) bundles of five α-helices linked by a large intracellular loop and a C-terminus positioned outside the cytoplasm. Using constraints derived from our experimental data, we also provide an updated position of helical regions generating a verisimilitude model of PIN1. Since the canonical long PINs show a high degree of conservation in TM domains and auxin transport capacity has been demonstrated for Arabidopsis representatives of this group, this empirically enhanced topological model of PIN1 will be an important starting point for further studies on PIN structure-function relationships. In addition, we have established protocols that can be used to probe the topology of other plasma membrane proteins in plants. Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.

  6. Action of Abscisic Acid on Auxin Transport and its Relation to Phototropism

    DEFF Research Database (Denmark)

    Naqvi, S. M.; Engvild, Kjeld Christensen

    1974-01-01

    The action of abscisic acid on the kinetics of auxin transport through Zea mays L. (cv. Goudster) coleoptiles has been investigated. Abscisic acid applied simultaneously with indoleacetic acid-2-14C in the donor block reduced the transport intensity without materially affecting the basipetal...... velocity or the uptake. No effect on acropetal transport was observed. The data have been used to discuss the similarities in effects of abscisic acid and visible radiation and a hypothesis is proposed to explain the phenomena of phototropism....

  7. Differential effects of auxin polar transport inhibitors on rooting in some Crassulaceae species

    Directory of Open Access Journals (Sweden)

    Marian Saniewski

    2014-07-01

    Full Text Available Effects of auxin polar transport inhibitors, 2,3,5-triio-dobenzoic acid (TIBA, 1-N-naphthylphthalamic acid (NPA and methyl 2-chloro-9-hydroxyfluorene-9-carboxylate (morphactin IT 3456, as a lanolin paste, on root formation in cuttings of some species of Crassulaceae, such as Bryophyllum daigremontianum, B. calycinum, Kalanchoe blossfeldiana and K. tubiflora, were studied. Cuttings of these plants were easily rooted in water without any treatment. TIBA and morphactin IT 3456 completely inhibited root formation in the cuttings of these plants but NPA did not when these inhibitors were applied around the stem below the leaves. When TIBA and morphactin were applied around the stem near the top, but leaves were present below the treatment, the root formation was observed in B. calycinum and K. blossfeldiana but in a smaller degree than in control cuttings. These results strongly suggest that endogenous auxin is required for root formation in cuttings of Crassulaceae plants. The differential mode of action of NPA is discussed together with its effect on auxin polar transport.

  8. The Arabidopsis concentration-dependent influx/efflux transporter ABCB4 regulates cellular auxin levels in the root epidermis

    Czech Academy of Sciences Publication Activity Database

    Kubeš, Martin; Yang, H.; Richter, G.L.; Cheng, Y.; Młodzińska, E.; Wang, X.; Blakeslee, J.J.; Carraro, N.; Petrášek, Jan; Zažímalová, Eva; Hoyerová, Klára; Ann Peer, W.; Murphy, A. S.

    2012-01-01

    Roč. 69, č. 4 (2012), s. 640-654 ISSN 0960-7412 R&D Projects: GA MŠk(CZ) LC06034; GA ČR(CZ) GAP305/11/0797 Institutional research plan: CEZ:AV0Z50380511 Keywords : auxin * auxin transporters * ATP-binding cassette B4 Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 6.582, year: 2012

  9. Differential auxin transport and accumulation in the stem base lead to profuse adventitious root primordia formation in the aerial roots (aer) mutant of tomato (Solanum lycopersicum L.).

    Science.gov (United States)

    Mignolli, F; Mariotti, L; Picciarelli, P; Vidoz, M L

    2017-06-01

    The aerial roots (aer) mutant of tomato is characterized by a profuse and precocious formation of adventitious root primordia along the stem. We demonstrated that auxin is involved in the aer phenotype but ruled out higher auxin sensitivity of mutant plants. Interestingly, polar auxin transport was altered in aer, as young seedlings showed a reduced response to an auxin transport inhibitor and higher expression of auxin export carriers SlPIN1 and SlPIN3. An abrupt reduction in transcripts of auxin efflux and influx genes in older aer hypocotyls caused a marked deceleration of auxin transport in more mature tissues. Indeed, in 20days old aer plants, the transport of labeled IAA was faster in apices than in hypocotyls, displaying an opposite trend in comparison to a wild type. In addition, auxin transport facilitators (SlPIN1, SlPIN4, SlLAX5) were more expressed in aer apices than in hypocotyls, suggesting that auxin moves faster from the upper to the lower part of the stem. Consequently, a significantly higher level of free and conjugated IAA was found at the base of aer stems with respect to their apices. This auxin accumulation is likely the cause of the aer phenotype. Copyright © 2017 Elsevier GmbH. All rights reserved.

  10. PIN6 auxin transporter at endoplasmic reticulum and plasma membrane mediates auxin homeostasis and organogenesis in Arabidopsis

    Czech Academy of Sciences Publication Activity Database

    Simon, S.; Skůpa, Petr; Viaene, T.; Zwiewka, M.; Tejos, R.; Klíma, Petr; Čarná, Mária; Rolčík, J.; De Rycke, R.; Moreno, I.; Dobrev, Petre; Orellana, A.; Zažímalová, Eva; Friml, J.

    2016-01-01

    Roč. 211, č. 1 (2016), s. 65-74 ISSN 0028-646X R&D Projects: GA MŠk(CZ) ED1.1.00/02.0068; GA ČR(CZ) GA16-10948S Institutional support: RVO:61389030 Keywords : auxin * endoplasmic reticulum (ER) * lateral root Subject RIV: ED - Physiology Impact factor: 7.330, year: 2016

  11. Gibberellins inhibit adventitious rooting in hybrid aspen and Arabidopsis by affecting auxin transport.

    Science.gov (United States)

    Mauriat, Mélanie; Petterle, Anna; Bellini, Catherine; Moritz, Thomas

    2014-05-01

    Knowledge of processes involved in adventitious rooting is important to improve both fundamental understanding of plant physiology and the propagation of numerous plants. Hybrid aspen (Populus tremula × tremuloïdes) plants overexpressing a key gibberellin (GA) biosynthesis gene (AtGA20ox1) grow rapidly but have poor rooting efficiency, which restricts their clonal propagation. Therefore, we investigated the molecular basis of adventitious rooting in Populus and the model plant Arabidopsis. The production of adventitious roots (ARs) in tree cuttings is initiated from the basal stem region, and involves the interplay of several endogenous and exogenous factors. The roles of several hormones in this process have been characterized, but the effects of GAs have not been fully investigated. Here, we show that a GA treatment negatively affects the numbers of ARs produced by wild-type hybrid aspen cuttings. Furthermore, both hybrid aspen plants and intact Arabidopsis seedlings overexpressing AtGA20ox1, PttGID1.1 or PttGID1.3 genes (with a 35S promoter) produce few ARs, although ARs develop from the basal stem region of hybrid aspen and the hypocotyl of Arabidopsis. In Arabidopsis, auxin and strigolactones are known to affect AR formation. Our data show that the inhibitory effect of GA treatment on adventitious rooting is not mediated by perturbation of the auxin signalling pathway, or of the strigolactone biosynthetic and signalling pathways. Instead, GAs appear to act by perturbing polar auxin transport, in particular auxin efflux in hybrid aspen, and both efflux and influx in Arabidopsis. © 2014 The Authors The Plant Journal © 2014 John Wiley & Sons Ltd.

  12. Distribution of indole-3-acetic acid in Petunia hybrida shoot tip cuttings and relationship between auxin transport, carbohydrate metabolism and adventitious root formation.

    OpenAIRE

    Ahkami, Amir H.; Melzer, Michael; Ghaffari, Mohammad R.; Pollmann, Stephan; Ghorbani, Majid; Shahinnia, Fahimeh; Hajirezaei, Mohammad R.; Druege, Uwe

    2013-01-01

    To determine the contribution of polar auxin transport (PAT) to auxin accumulation and to adventitious root (AR) formation in the stem base of Petunia hybrida shoot tip cuttings, the level of indole-3-acetic acid (IAA) was monitored in non-treated cuttings and cuttings treated with the auxin transport blocker naphthylphthalamic acid (NPA) and was complemented with precise anatomical studies. The temporal course of carbohydrates, amino acids and activities of controlling enzymes was also inves...

  13. Adaptation of root growth to increased ambient temperature requires auxin and ethylene coordination in Arabidopsis

    DEFF Research Database (Denmark)

    Fei, Qionghui; Wei, Shaodong; Zhou, Zhaoyang

    2017-01-01

    Key message: A fresh look at the roles of auxin, ethylene, and polar auxin transport during the plant root growth response to warmer ambient temperature (AT). Abstract: The ambient temperature (AT) affects plant growth and development. Plants can sense changes in the AT, but how this change......-naphthaleneacetic acid, but not indole-3-acetic acid (IAA). AUX1, PIN1, and PIN2 are involved in the ckrc1-1 root gravity response under increased AT. Furthermore, CKRC1-dependent auxin biosynthesis was critical for maintaining PIN1, PIN2, and AUX1 expression at elevated temperatures. Ethylene was also involved...... in this regulation through the ETR1 pathway. Higher AT can promote CKRC1-dependent auxin biosynthesis by enhancing ETR1-mediated ethylene signaling. Our research suggested that the interaction between auxin and ethylene and that the interaction-mediated polar auxin transport play important roles during the plant...

  14. Light-mediated polarization of the PIN3 auxin transporter for the phototropic response in Arabidopsis.

    OpenAIRE

    Ding Zhaojun; Galván-Ampudia Carlos S; Demarsy Emilie; Langowski Lukasz; Kleine-Vehn Jürgen; Fan Yuanwei; Morita Miyo T; Tasaka Masao; Fankhauser Christian; Offringa Remko; Friml Jirí

    2011-01-01

    Phototropism is an adaptation response through which plants grow towards the light. It involves light perception and asymmetric distribution of the plant hormone auxin. Here we identify a crucial part of the mechanism for phototropism revealing how light perception initiates auxin redistribution that leads to directional growth. We show that light polarizes the cellular localization of the auxin efflux carrier PIN3 in hypocotyl endodermis cells resulting in changes in auxin distribution and d...

  15. Characterization of transmembrane auxin transport in Arabidopsis suspension-cultured cells

    Czech Academy of Sciences Publication Activity Database

    Seifertová, Daniela; Skůpa, Petr; Rychtář, J.; Laňková, Martina; Pařezová, Markéta; Dobrev, Petre; Hoyerová, Klára; Petrášek, Jan; Zažímalová, Eva

    2014-01-01

    Roč. 171, č. 6 (2014), s. 429-437 ISSN 0176-1617 R&D Projects: GA ČR(CZ) GAP305/11/0797 Institutional support: RVO:61389030 Keywords : Auxin influx * Auxin efflux * Auxin metabolic profiling Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 2.557, year: 2014

  16. Arabidopsis N-MYC DOWNREGULATED-LIKE1, a Positive Regulator of Auxin Transport in a G Protein–Mediated Pathway[W

    Science.gov (United States)

    Mudgil, Yashwanti; Uhrig, Joachm F.; Zhou, Jiping; Temple, Brenda; Jiang, Kun; Jones, Alan M.

    2009-01-01

    Root architecture results from coordinated cell division and expansion in spatially distinct cells of the root and is established and maintained by gradients of auxin and nutrients such as sugars. Auxin is transported acropetally through the root within the central stele and then, upon reaching the root apex, auxin is transported basipetally through the outer cortical and epidermal cells. The two Gβγ dimers of the Arabidopsis thaliana heterotrimeric G protein complex are differentially localized to the central and cortical tissues of the Arabidopsis roots. A null mutation in either the single β (AGB1) or the two γ (AGG1 and AGG2) subunits confers phenotypes that disrupt the proper architecture of Arabidopsis roots and are consistent with altered auxin transport. Here, we describe an evolutionarily conserved interaction between AGB1/AGG dimers and a protein designated N-MYC DOWNREGULATED-LIKE1 (NDL1). The Arabidopsis genome encodes two homologs of NDL1 (NDL2 and NDL3), which also interact with AGB1/AGG1 and AGB1/AGG2 dimers. We show that NDL proteins act in a signaling pathway that modulates root auxin transport and auxin gradients in part by affecting the levels of at least two auxin transport facilitators. Reduction of NDL family gene expression and overexpression of NDL1 alter root architecture, auxin transport, and auxin maxima. AGB1, auxin, and sugars are required for NDL1 protein stability in regions of the root where auxin gradients are established; thus, the signaling mechanism contains feedback loops. PMID:19948787

  17. myo-Inositol-1-phosphate synthase is required for polar auxin transport and organ development

    KAUST Repository

    Chen, Hao

    2010-06-01

    myo-Inositol-1-phosphate synthase is a conserved enzyme that catalyzes the first committed and rate-limiting step in inositol biosynthesis. Despite its wide occurrence in all eukaryotes, the role of myo-inositol-1-phosphate synthase and de novo inositol biosynthesis in cell signaling and organism development has been unclear. In this study, we isolated loss-of-function mutants in the Arabidopsis MIPS1 gene from different ecotypes. It was found that all mips1 mutants are defective in embryogenesis, cotyledon venation patterning, root growth, and root cap development. The mutant roots are also agravitropic and have reduced basipetal auxin transport. mips1 mutants have significantly reduced levels of major phosphatidylinositols and exhibit much slower rates of endocytosis. Treatment with brefeldin A induces slower PIN2 protein aggregation in mips1, indicating altered PIN2 trafficking. Our results demonstrate that MIPS1 is critical for maintaining phosphatidylinositol levels and affects pattern formation in plants likely through regulation of auxin distribution. © 2010 by The American Society for Biochemistry and Molecular Biology, Inc.

  18. Diversification and expression of the PIN, AUX/LAX and ABCB families of putative auxin transporters in Populus

    Directory of Open Access Journals (Sweden)

    Nicola eCarraro

    2012-02-01

    Full Text Available Intercellular transport of the plant hormone auxin is mediated by three families of membrane-bound protein carriers, with the PIN and ABCB families coding primarily for efflux proteins and the AUX/LAX family coding for influx proteins. In the last decade our understanding of gene and protein function for these transporters in Arabidopsis has expanded rapidly but very little is known about their role in woody plant development. Here we present a comprehensive account of all three families in the model woody species Populus, including chromosome distribution, protein structure, quantitative gene expression, and evolutionary relationships. The PIN and AUX/LAX gene families in Populus comprise 16 and 8 members respectively, and show evidence for the retention of paralogs following a relatively recent whole genome duplication. There is also evidence for differential expression across tissues within many gene pairs. The ABCB family is previously undescribed in Populus and includes 20 members, showing a much deeper evolutionary history including both tandem and whole genome duplication as well as probable loss. A striking number of these transporters are expressed in developing Populus stems and we suggest that evolutionary and structural relationships with known auxin transporters in Arabidopsis can point toward candidate genes for further study in Populus. This is especially important for the ABCBs, which is a large family and includes members in Arabidopsis that are able to transport other substrates in addition to auxin. Protein modeling, sequence alignment and expression data all point to ABCB1.1 as a likely auxin transport protein in Populus. Given that basipetal auxin flow through the cambial zone shapes the development of woody stems, it is important that we identify the full complement of proteins involved in this process. This work should lay the foundation for studies targeting specific proteins for functional characterization and in situ

  19. Partial loss-of-function alleles reveal a role for GNOM in auxin transport-related, post-embryonic development of Arabidopsis

    DEFF Research Database (Denmark)

    Geldner, Niko; Richter, Sandra; Vieten, Anne

    2004-01-01

    The Arabidopsis GNOM gene encodes an ARF GDP/GTP exchange factor involved in embryonic axis formation and polar localisation of the auxin efflux regulator PIN1. To examine whether GNOM also plays a role in post-embryonic development and to clarify its involvement in auxin transport, we have...

  20. ROTUNDA3 function in plant development by phosphatase 2A-mediated regulation of auxin transporter recycling.

    Science.gov (United States)

    Karampelias, Michael; Neyt, Pia; De Groeve, Steven; Aesaert, Stijn; Coussens, Griet; Rolčík, Jakub; Bruno, Leonardo; De Winne, Nancy; Van Minnebruggen, Annemie; Van Montagu, Marc; Ponce, María Rosa; Micol, José Luis; Friml, Jiří; De Jaeger, Geert; Van Lijsebettens, Mieke

    2016-03-08

    The shaping of organs in plants depends on the intercellular flow of the phytohormone auxin, of which the directional signaling is determined by the polar subcellular localization of PIN-FORMED (PIN) auxin transport proteins. Phosphorylation dynamics of PIN proteins are affected by the protein phosphatase 2A (PP2A) and the PINOID kinase, which act antagonistically to mediate their apical-basal polar delivery. Here, we identified the ROTUNDA3 (RON3) protein as a regulator of the PP2A phosphatase activity in Arabidopsis thaliana. The RON3 gene was map-based cloned starting from the ron3-1 leaf mutant and found to be a unique, plant-specific gene coding for a protein with high and dispersed proline content. The ron3-1 and ron3-2 mutant phenotypes [i.e., reduced apical dominance, primary root length, lateral root emergence, and growth; increased ectopic stages II, IV, and V lateral root primordia; decreased auxin maxima in indole-3-acetic acid (IAA)-treated root apical meristems; hypergravitropic root growth and response; increased IAA levels in shoot apices; and reduced auxin accumulation in root meristems] support a role for RON3 in auxin biology. The affinity-purified PP2A complex with RON3 as bait suggested that RON3 might act in PIN transporter trafficking. Indeed, pharmacological interference with vesicle trafficking processes revealed that single ron3-2 and double ron3-2 rcn1 mutants have altered PIN polarity and endocytosis in specific cells. Our data indicate that RON3 contributes to auxin-mediated development by playing a role in PIN recycling and polarity establishment through regulation of the PP2A complex activity.

  1. OsPIN5b modulates rice (Oryza sativa) plant architecture and yield by changing auxin homeostasis, transport and distribution.

    Science.gov (United States)

    Lu, Guangwen; Coneva, Viktoriya; Casaretto, José A; Ying, Shan; Mahmood, Kashif; Liu, Fang; Nambara, Eiji; Bi, Yong-Mei; Rothstein, Steven J

    2015-09-01

    Plant architecture attributes such as tillering, plant height and panicle size are important agronomic traits that determine rice (Oryza sativa) productivity. Here, we report that altered auxin content, transport and distribution affect these traits, and hence rice yield. Overexpression of the auxin efflux carrier-like gene OsPIN5b causes pleiotropic effects, mainly reducing plant height, leaf and tiller number, shoot and root biomass, seed-setting rate, panicle length and yield parameters. Conversely, reduced expression of OsPIN5b results in higher tiller number, more vigorous root system, longer panicles and increased yield. We show that OsPIN5b is an endoplasmic reticulum (ER) -localized protein that participates in auxin homeostasis, transport and distribution in vivo. This work describes an example of an auxin-related gene where modulating its expression can simultaneously improve plant architecture and yield potential in rice, and reveals an important effect of hormonal signaling on these traits. © 2015 The Authors The Plant Journal © 2015 John Wiley & Sons Ltd.

  2. An auxin transport independent pathway is involved in phosphate stress-induced root architectural alterations in Arabidopsis. Identification of BIG as a mediator of auxin in pericycle cell activation.

    Science.gov (United States)

    López-Bucio, José; Hernández-Abreu, Esmeralda; Sánchez-Calderón, Lenin; Pérez-Torres, Anahí; Rampey, Rebekah A; Bartel, Bonnie; Herrera-Estrella, Luis

    2005-02-01

    Arabidopsis (Arabidopsis thaliana) plants display a number of root developmental responses to low phosphate availability, including primary root growth inhibition, greater formation of lateral roots, and increased root hair elongation. To gain insight into the regulatory mechanisms by which phosphorus (P) availability alters postembryonic root development, we performed a mutant screen to identify genetic determinants involved in the response to P deprivation. Three low phosphate-resistant root lines (lpr1-1 to lpr1-3) were isolated because of their reduced lateral root formation in low P conditions. Genetic and molecular analyses revealed that all lpr1 mutants were allelic to BIG, which is required for normal auxin transport in Arabidopsis. Detailed characterization of lateral root primordia (LRP) development in wild-type and lpr1 mutants revealed that BIG is required for pericycle cell activation to form LRP in both high (1 mm) and low (1 microm) P conditions, but not for the low P-induced alterations in primary root growth, lateral root emergence, and root hair elongation. Exogenously supplied auxin restored normal lateral root formation in lpr1 mutants in the two P treatments. Treatment of wild-type Arabidopsis seedlings with brefeldin A, a fungal metabolite that blocks auxin transport, phenocopies the root developmental alterations observed in lpr1 mutants in both high and low P conditions, suggesting that BIG participates in vesicular targeting of auxin transporters. Taken together, our results show that auxin transport and BIG function have fundamental roles in pericycle cell activation to form LRP and promote root hair elongation. The mechanism that activates root system architectural alterations in response to P deprivation, however, seems to be independent of auxin transport and BIG.

  3. Coevolving MAPK and PID phosphosites indicate an ancient environmental control of PIN auxin transporters in land plants.

    Science.gov (United States)

    Dory, Magdalena; Hatzimasoura, Elizabeth; Kállai, Brigitta M; Nagy, Szilvia K; Jäger, Katalin; Darula, Zsuzsanna; Nádai, Tímea V; Mészáros, Tamás; López-Juez, Enrique; Barnabás, Beáta; Palme, Klaus; Bögre, László; Ditengou, Franck A; Dóczi, Róbert

    2018-01-01

    Plant growth flexibly adapts to environmental conditions, implying cross-talk between environmental signalling and developmental regulation. Here, we show that the PIN auxin efflux carrier family possesses three highly conserved putative mitogen-activated protein kinase (MAPK) sites adjacent to the phosphorylation sites of the well-characterised AGC kinase PINOID, which regulates the polar localisation of PINs and directional auxin transport, thereby underpinning organ growth. The conserved sites of PIN1 are phosphorylated in vitro by two environmentally activated MAPKs, MPK4 and MPK6. In contrast to AGC kinases, MAPK-mediated phosphorylation of PIN1 at adjacent sites leads to a partial loss of the plasma membrane localisation of PIN1. MAPK-mediated modulation of PIN trafficking may participate in environmental adjustment of plant growth. © 2017 The Authors. FEBS Letters published by John Wiley & Sons Ltd on behalf of Federation of European Biochemical Societies.

  4. Arabidopsis thickvein mutation affects vein thickness and organ vascularization, and resides in a provascular cell-specific spermine synthase involved in vein definition and in polar auxin transport.

    Science.gov (United States)

    Clay, Nicole K; Nelson, Timothy

    2005-06-01

    Polar auxin transport has been implicated in the induction of vascular tissue and in the definition of vein positions. Leaves treated with chemical inhibitors of polar auxin transport exhibited vascular phenotypes that include increased vein thickness and vascularization. We describe a recessive mutant, thickvein (tkv), which develops thicker veins in leaves and in inflorescence stems. The increased vein thickness is attributable to an increased number of vascular cells. Mutant plants have smaller leaves and shorter inflorescence stems, and this reduction in organ size and height is accompanied by an increase in organ vascularization, which appears to be attributable to an increase in the recruitment of cells into veins. Furthermore, although floral development is normal, auxin transport in the inflorescence stem is significantly reduced in the mutant, suggesting that the defect in auxin transport is responsible for the vascular phenotypes. In the primary root, the veins appear morphologically normal, but root growth in the tkv mutant is hypersensitive to exogenous cytokinin. The tkv mutation was found to reside in the ACL5 gene, which encodes a spermine synthase and whose expression is specific to provascular cells. We propose that ACL5/TKV is involved in vein definition (defining the boundaries between veins and nonvein regions) and in polar auxin transport, and that polyamines are involved in this process.

  5. Fusarium oxysporum volatiles enhance plant growth via affecting auxin transport and signaling

    Directory of Open Access Journals (Sweden)

    Vasileios eBitas

    2015-11-01

    Full Text Available Volatile organic compounds (VOCs have well-documented roles in plant-plant communication and directing animal behavior. In this study, we examine the less understood roles of VOCs in plant-fungal relationships. Phylogenetically and ecologically diverse strains of Fusarium oxysporum, a fungal species complex that often resides in the rhizosphere of assorted plants, produce volatile compounds that augment shoot and root growth of Arabidopsis thaliana and tobacco. Growth responses of A. thaliana hormone signaling mutants and expression patterns of a GUS reporter gene under the auxin-responsive DR5 promoter supported the involvement of auxin signaling in F. oxysporum volatile-mediated growth enhancement. In addition, 1-naphthylthalamic acid, an inhibitor of auxin efflux, negated F. oxysporum volatile-mediated growth enhancement in both plants. Comparison of the profiles of volatile compounds produced by F. oxysporum strains that differentially affected plant growth suggests that the relative compositions of both growth inhibitory and stimulatory compounds may determine the degree of plant growth enhancement. Volatile-mediated signaling between fungi and plants may represent a potentially conserved, yet mostly overlooked, mechanism underpinning plant-fungus interactions and fungal niche adaption.

  6. Defining the selectivity of processes along the auxin response chain: a study using auxin analogues

    Czech Academy of Sciences Publication Activity Database

    Simon, Sibu; Kubeš, Martin; Baster, P.; Robert, S.; Dobrev, Petre; Friml, J.; Petrášek, Jan; Zažímalová, Eva

    2013-01-01

    Roč. 200, č. 4 (2013), s. 1034-1048 ISSN 0028-646X R&D Projects: GA ČR(CZ) GAP305/11/0797 Institutional research plan: CEZ:AV0Z50380511 Keywords : auxin analogues * auxin signalling * auxin transport Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 6.545, year: 2013

  7. The novel cyst nematode effector protein 19C07 interacts with the Arabidopsis auxin influx transporter LAX3 to control feeding site development.

    Science.gov (United States)

    Lee, Chris; Chronis, Demosthenis; Kenning, Charlotte; Peret, Benjamin; Hewezi, Tarek; Davis, Eric L; Baum, Thomas J; Hussey, Richard; Bennett, Malcolm; Mitchum, Melissa G

    2011-02-01

    Plant-parasitic cyst nematodes penetrate plant roots and transform cells near the vasculature into specialized feeding sites called syncytia. Syncytia form by incorporating neighboring cells into a single fused cell by cell wall dissolution. This process is initiated via injection of esophageal gland cell effector proteins from the nematode stylet into the host cell. Once inside the cell, these proteins may interact with host proteins that regulate the phytohormone auxin, as cellular concentrations of auxin increase in developing syncytia. Soybean cyst nematode (Heterodera glycines) Hg19C07 is a novel effector protein expressed specifically in the dorsal gland cell during nematode parasitism. Here, we describe its ortholog in the beet cyst nematode (Heterodera schachtii), Hs19C07. We demonstrate that Hs19C07 interacts with the Arabidopsis (Arabidopsis thaliana) auxin influx transporter LAX3. LAX3 is expressed in cells overlying lateral root primordia, providing auxin signaling that triggers the expression of cell wall-modifying enzymes, allowing lateral roots to emerge. We found that LAX3 and polygalacturonase, a LAX3-induced cell wall-modifying enzyme, are expressed in the developing syncytium and in cells to be incorporated into the syncytium. We observed no decrease in H. schachtii infectivity in aux1 and lax3 single mutants. However, a decrease was observed in both the aux1lax3 double mutant and the aux1lax1lax2lax3 quadruple mutant. In addition, ectopic expression of 19C07 was found to speed up lateral root emergence. We propose that Hs19C07 most likely increases LAX3-mediated auxin influx and may provide a mechanism for cyst nematodes to modulate auxin flow into root cells, stimulating cell wall hydrolysis for syncytium development.

  8. Gravitropism interferes with hydrotropism via counteracting auxin dynamics in cucumber roots: clinorotation and spaceflight experiments.

    Science.gov (United States)

    Morohashi, Keita; Okamoto, Miki; Yamazaki, Chiaki; Fujii, Nobuharu; Miyazawa, Yutaka; Kamada, Motoshi; Kasahara, Haruo; Osada, Ikuko; Shimazu, Toru; Fusejima, Yasuo; Higashibata, Akira; Yamazaki, Takashi; Ishioka, Noriaki; Kobayashi, Akie; Takahashi, Hideyuki

    2017-09-01

    Roots of land plants show gravitropism and hydrotropism in response to gravity and moisture gradients, respectively, for controlling their growth orientation. Gravitropism interferes with hydrotropism, although the mechanistic aspects are poorly understood. Here, we differentiated hydrotropism from gravitropism in cucumber roots by conducting clinorotation and spaceflight experiments. We also compared mechanisms regulating hydrotropism and auxin-regulated gravitropism. Clinorotated or microgravity (μG)-grown cucumber seedling roots hydrotropically bent toward wet substrate in the presence of moisture gradients, but they grew straight in the direction of normal gravitational force at the Earth's surface (1G) on the ground or centrifuge-generated 1G in space. The roots appeared to become hydrotropically more sensitive to moisture gradients under μG conditions in space. Auxin transport inhibitors significantly reduced the hydrotropic response of clinorotated seedling roots. The auxin efflux protein CsPIN5 was differentially expressed in roots of both clinorotated and μG-grown seedlings; with higher expression in the high-humidity (concave) side than the low-humidity (convex) side of hydrotropically responding roots. Our results suggest that roots become hydrotropically sensitive in μG, and CsPIN5-mediated auxin transport has an important role in inducing root hydrotropism. Thus, hydrotropic and gravitropic responses in cucumber roots may compete via differential auxin dynamics established in response to moisture gradients and gravity. © 2017 The Authors. New Phytologist © 2017 New Phytologist Trust.

  9. Transport and concentration of abscisic acid (ABA) and auxin (IAA) in deciduous and coniferous trees. Transport und Gehalt von Abscisinsaeure (ABA) und Auxin (IAA) in Laub- und Nadelblaettern

    Energy Technology Data Exchange (ETDEWEB)

    Hartung, W.

    1988-09-01

    Abscisic acid and indoleacetic acid were chosen to examine whether intact deciduous and coniferous tissues from spruce, hemlock fir, spinage, barley and sorrel or isolated mesophyll protoplasts from barley and closing cell preparations from Valerianella locusta are affected by sulphur dioxide in terms of changes in the concentration, transportation and distribution of such plant hormones. The distribution of phytohormones like ABA and IAA over the individual cell compartments is determined by the different pH gradients of the latter. Owing to their acidity these hormones are accumulated in alkaline cell inclusion bodies like chloroplasts and cytosol. Potentially acid air pollutants like SO{sub 2} and NO{sub x} lead to acidification of previously alkaline cell compartments, due to which fact the cellular pH gradients are reduced. This, in turn, gives rise to a redistribution of phytohormones to the effect that certain target cells such as closing cells of leaves or meristem cells come under the influence of altered hormone concentrations and compositions. This is bound to affect the processes controlling the development, growth and stress behaviour of plants. (orig.) With 55 refs., 2 tabs., 16 figs.

  10. Auxin transport in leafy pea stem cuttings is partially driven by photosynthesis

    International Nuclear Information System (INIS)

    Kumpula, C.L.; Potter, J.R.

    1987-01-01

    When 14 C-IAA was applied to the apex of disbudded leafy pea stem cuttings (15 cm long), the movement of 14 C-IAA to the base of the cuttings after 24 h was influenced by the photosynthetic rate. In the absence of photosynthesis, light did not influence 14 C-IAA movement. Photosynthesis was altered by varying light, CO 2 concentration, or stomatal aperature (blocked with an antitranspirant). Radioactivity (identified by co-chromatography) was 25, 60, and 5% IAA, IAA-aspartate, and indolealdehyde respectively regardless of treatment. Adventitious root formation was reduced 50 to 95% and movement of IAA was inhibited 50 to 70% by decreasing gross photosynthesis 90 to 100%. Apparently, photosynthesis partially drives the movement of IAA from the apex to the base where roots arise. This gives a probably role of photosynthesis in rooting, because in this system virtually no rooting will take place without exogenous auxin and at least a low level of gross photosynthesis

  11. GRAVITY PIPELINE TRANSPORT FOR HARDENING FILLING MIXTURES

    Directory of Open Access Journals (Sweden)

    Leonid KROUPNIK

    2015-12-01

    Full Text Available In underground mining of solid minerals becoming increasingly common development system with stowing hardening mixtures. In this case the natural ore array after it is replaced by an artificial excavation of solidified filling mixture consisting of binder, aggregates and water. Such a mixture is prepared on the surface on special stowing complexes and transported underground at special stowing pipelines. However, it is transported to the horizons of a few kilometers, which requires a sustainable mode of motion of such a mixture in the pipeline. Hardening stowing mixture changes its rheological characteristics over time, which complicates the calculation of the parameters of pipeline transportation. The article suggests a method of determining the initial parameters of such mixtures: the status coefficient, indicator of transportability, coefficient of hydrodynamic resistance to motion of the mixture. These indicators characterize the mixture in terms of the possibility to transport it through pipes. On the basis of these indicators is proposed methodology for calculating the parameters of pipeline transport hardening filling mixtures in drift mode when traffic on the horizontal part of the mixture under pressure column of the mixture in the vertical part of the backfill of the pipeline. This technique allows stable operation is guaranteed to provide pipeline transportation.

  12. Fluid/Gravity Correspondence, Second Order Transport and Gravitational Anomaly*,**

    Directory of Open Access Journals (Sweden)

    Megías Eugenio

    2014-03-01

    Full Text Available We study the transport properties of a relativistic fluid affected by chiral and gauge-gravitational anomalies. The computation is performed in the framework of the fluid/gravity correspondence for a 5 dim holographic model with Chern-Simons terms in the action. We find new anomalous and non anomalous transport coefficients, as well as new contributions to the existing ones coming from the mixed gauge-gravitational anomaly. Consequences for the shear waves dispersion relation are analyzed.

  13. A Transportable Gravity Gradiometer Based on Atom Interferometry

    Science.gov (United States)

    Yu, Nan; Thompson, Robert J.; Kellogg, James R.; Aveline, David C.; Maleki, Lute; Kohel, James M.

    2010-01-01

    A transportable atom interferometer-based gravity gradiometer has been developed at JPL to carry out measurements of Earth's gravity field at ever finer spatial resolutions, and to facilitate high-resolution monitoring of temporal variations in the gravity field from ground- and flight-based platforms. Existing satellite-based gravity missions such as CHAMP and GRACE measure the gravity field via precise monitoring of the motion of the satellites; i.e. the satellites themselves function as test masses. JPL's quantum gravity gradiometer employs a quantum phase measurement technique, similar to that employed in atomic clocks, made possible by recent advances in laser cooling and manipulation of atoms. This measurement technique is based on atomwave interferometry, and individual laser-cooled atoms are used as drag-free test masses. The quantum gravity gradiometer employs two identical atom interferometers as precision accelerometers to measure the difference in gravitational acceleration between two points (Figure 1). By using the same lasers for the manipulation of atoms in both interferometers, the accelerometers have a common reference frame and non-inertial accelerations are effectively rejected as common mode noise in the differential measurement of the gravity gradient. As a result, the dual atom interferometer-based gravity gradiometer allows gravity measurements on a moving platform, while achieving the same long-term stability of the best atomic clocks. In the laboratory-based prototype (Figure 2), the cesium atoms used in each atom interferometer are initially collected and cooled in two separate magneto-optic traps (MOTs). Each MOT, consisting of three orthogonal pairs of counter-propagating laser beams centered on a quadrupole magnetic field, collects up to 10(exp 9) atoms. These atoms are then launched vertically as in an atom fountain by switching off the magnetic field and introducing a slight frequency shift between pairs of lasers to create a moving

  14. Effects of ethylene on the kinetics of curvature and auxin redistribution in gravistimulated roots of Zea mays

    Science.gov (United States)

    Lee, J. S.; Evans, M. L.

    1990-01-01

    We tested the involvement of ethylene in maize (Zea mays L.) root gravitropism by measuring the kinetics of curvature and lateral auxin movement in roots treated with ethylene, inhibitors of ethylene synthesis, or inhibitors of ethylene action. In the presence of ethylene the latent period of gravitropic curvature appeared to be increased somewhat. However, ethylene-treated roots continued to curve after control roots had reached their final angle of curvature. Consequently, maximum curvature in the presence of ethylene was much greater in ethylene-treated roots than in controls. Inhibitors of ethylene biosynthesis or action had effects on the kinetics of curvature opposite to that of ethylene, i.e. the latent period appeared to be shortened somewhat while total curvature was reduced relative to that of controls. Label from applied 3H-indole-3-acetic acid was preferentially transported toward the lower side of stimulated roots. In parallel with effects on curvature, ethylene treatment delayed the development of gravity-induced asymmetric auxin movement across the root but extended its duration once initiated. The auxin transport inhibitor, 1-N-naphthylphthalamic acid reduced both gravitropic curvature and the effect of ethylene on curvature. Since neither ethylene nor inhibitors of ethylene biosynthesis or action prevented curvature, we conclude that ethylene does not mediate the primary differential growth response causing curvature. Because ethylene affects curvature and auxin transport in parallel, we suggest that ethylene modifies curvature by affecting gravity-induced lateral transport of auxin, perhaps by interfering with adaptation of the auxin transport system to the gravistimulus.

  15. Arabidopsis thickvein Mutation Affects Vein Thickness and Organ Vascularization, and Resides in a Provascular Cell-Specific Spermine Synthase Involved in Vein Definition and in Polar Auxin Transport1

    Science.gov (United States)

    Clay, Nicole K.; Nelson, Timothy

    2005-01-01

    Polar auxin transport has been implicated in the induction of vascular tissue and in the definition of vein positions. Leaves treated with chemical inhibitors of polar auxin transport exhibited vascular phenotypes that include increased vein thickness and vascularization. We describe a recessive mutant, thickvein (tkv), which develops thicker veins in leaves and in inflorescence stems. The increased vein thickness is attributable to an increased number of vascular cells. Mutant plants have smaller leaves and shorter inflorescence stems, and this reduction in organ size and height is accompanied by an increase in organ vascularization, which appears to be attributable to an increase in the recruitment of cells into veins. Furthermore, although floral development is normal, auxin transport in the inflorescence stem is significantly reduced in the mutant, suggesting that the defect in auxin transport is responsible for the vascular phenotypes. In the primary root, the veins appear morphologically normal, but root growth in the tkv mutant is hypersensitive to exogenous cytokinin. The tkv mutation was found to reside in the ACL5 gene, which encodes a spermine synthase and whose expression is specific to provascular cells. We propose that ACL5/TKV is involved in vein definition (defining the boundaries between veins and nonvein regions) and in polar auxin transport, and that polyamines are involved in this process. PMID:15894745

  16. 5'-azido-N-1-naphthylphthalamic acid, a photolabile analog of the auxin transport inhibitor, N-1-naphthylphthalamic acid: synthesis and binding properties

    International Nuclear Information System (INIS)

    Voet, J.G.; Howley, K.; Shumsky, J.S.

    1987-01-01

    The polar transport of the plant growth regulator, auxin (indole-3-acetic acid, IAAH), is thought to involve the participation of several proteins in the plasma membrane, including a specific, saturable, voltage independent H + /IAA - efflux carrier located preferentially at the basal end of each cell. Auxin transport is specifically inhibited by the herbicide, N-1-naphthylphthalamic acid (NPA), which binds specifically to a protein in the plasma membrane, thought to be either the IAA - efflux carrier or an allosteric effector protein. They have synthesized and characterized a photolabile analog of NPA, 5'-azido-N-1-naphthylphthalamic acid (Az-NPA). This potential photoaffinity label for the NPA binding protein competes with 3 H-NPA for binding sites on Curcurbita pepo L. (zucchini) stem cell membranes with K/sub j/ = 1.5 x 10 -7 M. The K/sub i/ for NPA under these conditions is 2 x 10 -8 M, indicating that the affinity of Az-NPA for the membranes is only 7.5 fold lower than NPA. While the binding of 4.6 x 10 -6 M Az-NPA to NPA binding sites is reversible in the dark, exposure to light results in a 30% loss in 3 H-NPA binding ability. Pretreatment with 10 -4 M NPA protects the membranes against photodestruction of 3 H-NPA binding sites by Az-NPA, supporting the conclusion that Az-NPA destroys these sites by specific covalent attachment

  17. Entrainment, transport and deposition of sediment by saline gravity currents

    Science.gov (United States)

    Zordan, Jessica; Juez, Carmelo; Schleiss, Anton J.; Franca, Mário J.

    2018-05-01

    Few studies have addressed simultaneously the feedback between the hydrodynamics of a gravity current and the geomorphological changes of a mobile bed. Hydrodynamic quantities such as turbulent and mean velocities, bed shear stress and turbulent stresses undoubtedly govern the processes of entrainment, transport and deposition. On the other hand, the incorporation of entrained sediment in the current may change its momentum by introducing extra internal stresses, introducing thus a feedback process. These two main questions are here investigated. Laboratory experiments of saline gravity currents, produced by lock-exchange, flowing over a mobile bed channel reach, are here reported. Different initial buoyancies of the current in the lock are tested together with three different grain sizes of the non-coherent sediment that form the erodible bed. Results from velocity measurements are combined with the visualization of the sediment movement in the mobile reach and with post-test topographic and photo surveys of the geomorphology modifications of the channel bed. Mean and turbulent velocities are measured and bed shear stress and Reynolds stresses are estimated. We show that the mean vertical component of the velocity and bed shear stress are highly correlated with the first instants of sediment entrainment. Vertical turbulent velocity is similarly related to entrainment, although with lower correlation values, contributing as well to the sediment movement. Bed shear stress and Reynolds shear stress measured near the bed are correlated with sediment entrainment for longer periods, indicating that these quantities are associated to distal transport as well. Geomorphological changes in the mobile bed are strongly related to the impulse caused by the bed shear stress on the sediment. On the other hand, we show that the nature of the grain of the mobile bed reach influences the hydrodynamics of the current which means that a feedback mechanisms between both occurs during

  18. Gravity sensing and signal transduction in vascular plant primary roots.

    Science.gov (United States)

    Baldwin, Katherine L; Strohm, Allison K; Masson, Patrick H

    2013-01-01

    During gravitropism, the potential energy of gravity is converted into a biochemical signal. How this transfer occurs remains one of the most exciting mysteries in plant cell biology. New experiments are filling in pieces of the puzzle. In this review, we introduce gravitropism and give an overview of what we know about gravity sensing in roots of vascular plants, with special highlight on recent papers. When plant roots are reoriented sideways, amyloplast resedimentation in the columella cells is a key initial step in gravity sensing. This process somehow leads to cytoplasmic alkalinization of these cells followed by relocalization of auxin efflux carriers (PINs). This changes auxin flow throughout the root, generating a lateral gradient of auxin across the cap that upon transmission to the elongation zone leads to differential cell elongation and gravibending. We will present the evidence for and against the following players having a role in transferring the signal from the amyloplast sedimentation into the auxin signaling cascade: mechanosensitive ion channels, actin, calcium ions, inositol trisphosphate, receptors/ligands, ARG1/ARL2, spermine, and the TOC complex. We also outline auxin transport and signaling during gravitropism.

  19. Phyllotaxis involves auxin drainage through leaf primordia

    DEFF Research Database (Denmark)

    Deb, Yamini; Marti, Dominik; Frenz, Martin

    2015-01-01

    The spatial arrangement of leaves and flowers around the stem, known as phyllotaxis, is controlled by an auxin-dependent reiterative mechanism that leads to regular spacing of the organs and thereby to remarkably precise phyllotactic patterns. The mechanism is based on the active cellular transport...... of phyllotaxis invoke the accumulation of auxin at leaf initials and removal of auxin through their developing vascular strand, the midvein. We have developed a precise microsurgical tool to ablate the midvein at high spatial and temporal resolution in order to test its function in leaf formation and phyllotaxis...

  20. Dynamic regulation of auxin oxidase and conjugating enzymes AtDAO1 and GH3 modulates auxin homeostasis.

    Science.gov (United States)

    Mellor, Nathan; Band, Leah R; Pěnčík, Aleš; Novák, Ondřej; Rashed, Afaf; Holman, Tara; Wilson, Michael H; Voß, Ute; Bishopp, Anthony; King, John R; Ljung, Karin; Bennett, Malcolm J; Owen, Markus R

    2016-09-27

    The hormone auxin is a key regulator of plant growth and development, and great progress has been made understanding auxin transport and signaling. Here, we show that auxin metabolism and homeostasis are also regulated in a complex manner. The principal auxin degradation pathways in Arabidopsis include oxidation by Arabidopsis thaliana gene DIOXYGENASE FOR AUXIN OXIDATION 1/2 (AtDAO1/2) and conjugation by Gretchen Hagen3s (GH3s). Metabolic profiling of dao1-1 root tissues revealed a 50% decrease in the oxidation product 2-oxoindole-3-acetic acid (oxIAA) and increases in the conjugated forms indole-3-acetic acid aspartic acid (IAA-Asp) and indole-3-acetic acid glutamic acid (IAA-Glu) of 438- and 240-fold, respectively, whereas auxin remains close to the WT. By fitting parameter values to a mathematical model of these metabolic pathways, we show that, in addition to reduced oxidation, both auxin biosynthesis and conjugation are increased in dao1-1 Transcripts of AtDAO1 and GH3 genes increase in response to auxin over different timescales and concentration ranges. Including this regulation of AtDAO1 and GH3 in an extended model reveals that auxin oxidation is more important for auxin homoeostasis at lower hormone concentrations, whereas auxin conjugation is most significant at high auxin levels. Finally, embedding our homeostasis model in a multicellular simulation to assess the spatial effect of the dao1-1 mutant shows that auxin increases in outer root tissues in agreement with the dao1-1 mutant root hair phenotype. We conclude that auxin homeostasis is dependent on AtDAO1, acting in concert with GH3, to maintain auxin at optimal levels for plant growth and development.

  1. Fluid/Gravity Correspondence, Second Order Transport and Gravitational Anomaly***

    Science.gov (United States)

    Megías, Eugenio; Pena-Benitez, Francisco

    2014-03-01

    We study the transport properties of a relativistic fluid affected by chiral and gauge-gravitational anomalies. The computation is performed in the framework of the fluid/gravity correspondence for a 5 dim holographic model with Chern-Simons terms in the action. We find new anomalous and non anomalous transport coefficients, as well as new contributions to the existing ones coming from the mixed gauge-gravitational anomaly. Consequences for the shear waves dispersion relation are analyzed. Talk given by E. Megías at the International Nuclear Physics Conference INPC 2013, 2-7 June 2013, Firenze, Italy.Supported by Plan Nacional de Altas Energías (FPA2009-07908, FPA2011-25948), Spanish MICINN Consolider-Ingenio 2010 Programme CPAN (CSD2007-00042), Comunidad de Madrid HEP-HACOS S2009/ESP-1473, Spanish MINECO's Centro de Excelencia Severo Ochoa Program (SEV-2012-0234, SEV-2012-0249), and the Juan de la Cierva Program.

  2. Single-cell-based system to monitor carrier driven cellular auxin homeostasis

    Science.gov (United States)

    2013-01-01

    Background Abundance and distribution of the plant hormone auxin play important roles in plant development. Besides other metabolic processes, various auxin carriers control the cellular level of active auxin and, hence, are major regulators of cellular auxin homeostasis. Despite the developmental importance of auxin transporters, a simple medium-to-high throughput approach to assess carrier activities is still missing. Here we show that carrier driven depletion of cellular auxin correlates with reduced nuclear auxin signaling in tobacco Bright Yellow-2 (BY-2) cell cultures. Results We developed an easy to use transient single-cell-based system to detect carrier activity. We use the relative changes in signaling output of the auxin responsive promoter element DR5 to indirectly visualize auxin carrier activity. The feasibility of the transient approach was demonstrated by pharmacological and genetic interference with auxin signaling and transport. As a proof of concept, we provide visual evidence that the prominent auxin transport proteins PIN-FORMED (PIN)2 and PIN5 regulate cellular auxin homeostasis at the plasma membrane and endoplasmic reticulum (ER), respectively. Our data suggest that PIN2 and PIN5 have different sensitivities to the auxin transport inhibitor 1-naphthylphthalamic acid (NPA). Also the putative PIN-LIKES (PILS) auxin carrier activity at the ER is insensitive to NPA in our system, indicating that NPA blocks intercellular, but not intracellular auxin transport. Conclusions This single-cell-based system is a useful tool by which the activity of putative auxin carriers, such as PINs, PILS and WALLS ARE THIN1 (WAT1), can be indirectly visualized in a medium-to-high throughput manner. Moreover, our single cell system might be useful to investigate also other hormonal signaling pathways, such as cytokinin. PMID:23379388

  3. Auxin Response Factors

    NARCIS (Netherlands)

    Roosjen, Mark; Paque, Sébastien; Weijers, Dolf

    2018-01-01

    The phytohormone auxin is involved in almost all developmental processes in land plants. Most, if not all, of these processes are mediated by changes in gene expression. Auxin acts on gene expression through a short nuclear pathway that converges upon the activation of a family of DNA-binding

  4. Gravity

    CERN Document Server

    Gamow, George

    2003-01-01

    A distinguished physicist and teacher, George Gamow also possessed a special gift for making the intricacies of science accessible to a wide audience. In Gravity, he takes an enlightening look at three of the towering figures of science who unlocked many of the mysteries behind the laws of physics: Galileo, the first to take a close look at the process of free and restricted fall; Newton, originator of the concept of gravity as a universal force; and Einstein, who proposed that gravity is no more than the curvature of the four-dimensional space-time continuum.Graced with the author's own draw

  5. What has been seen cannot be unseen-detecting auxin in vivo

    Czech Academy of Sciences Publication Activity Database

    Pařízková, Barbora; Pernisová, M.; Novák, Ondřej

    2017-01-01

    Roč. 18, č. 12 (2017), č. článku 2736. E-ISSN 1422-0067 R&D Projects: GA MŠk(CZ) LO1204; GA ČR GA16-01137S Institutional support: RVO:61389030 Keywords : Auxin * Auxin distribution * Auxin signalling * Auxin transport * Direct visualization * Indirect visualization * Receptor * Sensor Subject RIV: EB - Genetics ; Molecular Biology OBOR OECD: Plant sciences, botany Impact factor: 3.226, year: 2016

  6. Modelling of Arabidopsis LAX3 expression suggests auxin homeostasis.

    Science.gov (United States)

    Mellor, Nathan; Péret, Benjamin; Porco, Silvana; Sairanen, Ilkka; Ljung, Karin; Bennett, Malcolm; King, John

    2015-02-07

    Emergence of new lateral roots from within the primary root in Arabidopsis has been shown to be regulated by the phytohormone auxin, via the expression of the auxin influx carrier LAX3, mediated by the ARF7/19 IAA14 signalling module (Swarup et al., 2008). A single cell model of the LAX3 and IAA14 auxin response was formulated and used to demonstrate that hysteresis and bistability may explain the experimentally observed 'all-or-nothing' LAX3 spatial expression pattern in cortical cells containing a gradient of auxin concentrations. The model was tested further by using a parameter fitting algorithm to match model output with qRT-PCR mRNA expression data following exogenous auxin treatment. It was found that the model is able to show good agreement with the data, but only when the exogenous auxin signal is degraded over time, at a rate higher than that measured in the experimental medium, suggesting the triggering of an endogenous auxin homeostasis mechanism. Testing the model over a more physiologically relevant range of extracellular auxin shows bistability and hysteresis still occur when using the optimised parameters, providing the rate of LAX3 active auxin transport is sufficiently high relative to passive diffusion. Copyright © 2014 Elsevier Ltd. All rights reserved.

  7. Auxin Homeostasis in Arabidopsis Ovules Is Anther-Dependent at Maturation and Changes Dynamically upon Fertilization

    Directory of Open Access Journals (Sweden)

    Emma Larsson

    2017-10-01

    Full Text Available The plant hormone auxin is a vital component for plant reproduction as it regulates the development of both male and female reproductive organs, including ovules and gynoecia. Furthermore, auxin plays important roles in the development and growth of seeds and fruits. Auxin responses can be detected in ovules shortly after fertilization, and it has been suggested that this accumulation is a prerequisite for the developmental reprogramming of the ovules to seeds, and of the gynoecium to a fruit. However, the roles of auxin at the final stages of ovule development, and the sources of auxin leading to the observed responses in ovules after fertilization have remained elusive. Here we have characterized the auxin readout in Arabidopsis ovules, at the pre-anthesis, anthesis and in the immediate post-fertilization stages, using the R2D2 auxin sensor. In addition we have mapped the expression of auxin biosynthesis and conjugation genes, as well as that of auxin transporting proteins, during the same developmental stages. These analyses reveal specific spatiotemporal patterns of the different auxin homeostasis regulators. Auxin biosynthesis genes and auxin transport proteins define a pre-patterning of vascular cell identity in the pre-anthesis funiculus. Furthermore, our data suggests that auxin efflux from the ovule is restricted in an anther-dependent manner, presumably to synchronize reproductive organ development and thereby optimizing the chances of successful fertilization. Finally, de novo auxin biosynthesis together with reduced auxin conjugation and transport result in an enhanced auxin readout throughout the sporophytic tissues of the ovules soon after fertilization. Together, our results suggest a sophisticated set of regulatory cascades that allow successful fertilization and the subsequent transition of the female reproductive structures into seeds and fruits.

  8. Auxin efflux by PIN-FORMED proteins is activated by two different protein kinases, D6 PROTEIN KINASE and PINOID

    KAUST Repository

    Zourelidou, Melina; Absmanner, Birgit; Weller, Benjamin; Barbosa, Inê s CR; Willige, Bjö rn C; Fastner, Astrid; Streit, Verena; Port, Sarah A; Colcombet, Jean; de la Fuente van Bentem, Sergio; Hirt, Heribert; Kuster, Bernhard; Schulze, Waltraud X; Hammes, Ulrich Z; Schwechheimer, Claus

    2014-01-01

    The development and morphology of vascular plants is critically determined by synthesis and proper distribution of the phytohormone auxin. The directed cell-to-cell distribution of auxin is achieved through a system of auxin influx and efflux transporters. PIN-FORMED (PIN) proteins are proposed auxin efflux transporters, and auxin fluxes can seemingly be predicted based on the-in many cells-asymmetric plasma membrane distribution of PINs. Here, we show in a heterologous Xenopus oocyte system as well as in Arabidopsis thaliana inflorescence stems that PIN-mediated auxin transport is directly activated by D6 PROTEIN KINASE (D6PK) and PINOID (PID)/WAG kinases of the Arabidopsis AGCVIII kinase family. At the same time, we reveal that D6PKs and PID have differential phosphosite preferences. Our study suggests that PIN activation by protein kinases is a crucial component of auxin transport control that must be taken into account to understand auxin distribution within the plant.

  9. Auxin efflux by PIN-FORMED proteins is activated by two different protein kinases, D6 PROTEIN KINASE and PINOID

    KAUST Repository

    Zourelidou, Melina

    2014-06-19

    The development and morphology of vascular plants is critically determined by synthesis and proper distribution of the phytohormone auxin. The directed cell-to-cell distribution of auxin is achieved through a system of auxin influx and efflux transporters. PIN-FORMED (PIN) proteins are proposed auxin efflux transporters, and auxin fluxes can seemingly be predicted based on the-in many cells-asymmetric plasma membrane distribution of PINs. Here, we show in a heterologous Xenopus oocyte system as well as in Arabidopsis thaliana inflorescence stems that PIN-mediated auxin transport is directly activated by D6 PROTEIN KINASE (D6PK) and PINOID (PID)/WAG kinases of the Arabidopsis AGCVIII kinase family. At the same time, we reveal that D6PKs and PID have differential phosphosite preferences. Our study suggests that PIN activation by protein kinases is a crucial component of auxin transport control that must be taken into account to understand auxin distribution within the plant.

  10. gravity

    Indian Academy of Sciences (India)

    We study the cosmological dynamics for R p exp( λ R ) gravity theory in the metric formalism, using dynamical systems approach. Considering higher-dimensional FRW geometries in case of an imperfect fluid which has two different scale factors in the normal and extra dimensions, we find the exact solutions, and study its ...

  11. A comprehensive phylogeny of auxin homeostasis genes involved in adventitious root formation in carnation stem cuttings.

    Directory of Open Access Journals (Sweden)

    Ana Belén Sánchez-García

    Full Text Available Understanding the functional basis of auxin homeostasis requires knowledge about auxin biosynthesis, auxin transport and auxin catabolism genes, which is not always directly available despite the recent whole-genome sequencing of many plant species. Through sequence homology searches and phylogenetic analyses on a selection of 11 plant species with high-quality genome annotation, we identified the putative gene homologs involved in auxin biosynthesis, auxin catabolism and auxin transport pathways in carnation (Dianthus caryophyllus L.. To deepen our knowledge of the regulatory events underlying auxin-mediated adventitious root formation in carnation stem cuttings, we used RNA-sequencing data to confirm the expression profiles of some auxin homeostasis genes during the rooting of two carnation cultivars with different rooting behaviors. We also confirmed the presence of several auxin-related metabolites in the stem cutting tissues. Our findings offer a comprehensive overview of auxin homeostasis genes in carnation and provide a solid foundation for further experiments investigating the role of auxin homeostasis in the regulation of adventitious root formation in carnation.

  12. Influence of gravity on transport and retention of representative engineered nanoparticles in quartz sand.

    Science.gov (United States)

    Cai, Li; Zhu, Jinghan; Hou, Yanglong; Tong, Meiping; Kim, Hyunjung

    2015-10-01

    Four types of NPs: carbon nanotubes and graphene oxide (carbon-based NPs), titanium dioxide and zinc oxide metal-oxide NPs, were utilized to systematically determine the influence of gravity on the transport of NPs in porous media. Packed column experiments for two types of carbon-based NPs were performed under unfavorable conditions in both up-flow (gravity-negative) and down-flow (gravity-positive) orientations, while for two types of metal-oxide NPs, experiments were performed under both unfavorable and favorable conditions in both up-flow and down-flow orientations. Both breakthrough curves and retained profiles of two types of carbon-based NPs in up-flow orientation were equivalent to those in down-flow orientation, indicating that gravity had negligible effect on the transport and retention of carbon-based NPs under unfavorable conditions. In contrast, under both unfavorable and favorable conditions, the breakthrough curves for two types of metal-oxide NPs in down-flow orientation were lower relative to those in up-flow orientation, indicating that gravity could decrease the transport of metal-oxide NPs in porous media. The distinct effect of gravity on the transport and retention of carbon-based and metal-oxide NPs was mainly attributed to the contribution of gravity to the force balance on the NPs in quartz sand. The contribution of gravity was determined by the interplay of the density and sizes of NP aggregates under examined solution conditions. Copyright © 2015 Elsevier B.V. All rights reserved.

  13. Center for low-gravity fluid mechanics and transport phenomena

    Science.gov (United States)

    Kassoy, D. R.; Sani, R. L.

    1991-01-01

    Research projects in several areas are discussed. Mass transport in vapor phase systems, droplet collisions and coalescence in microgravity, and rapid solidification of undercooled melts are discussed.

  14. Diffusive smoothing of surfzone bathymetry by gravity-driven sediment transport

    Science.gov (United States)

    Moulton, M. R.; Elgar, S.; Raubenheimer, B.

    2012-12-01

    Gravity-driven sediment transport often is assumed to have a small effect on the evolution of nearshore morphology. Here, it is shown that down-slope gravity-driven sediment transport is an important process acting to smooth steep bathymetric features in the surfzone. Gravity-driven transport can be modeled as a diffusive term in the sediment continuity equation governing temporal (t) changes in bed level (h): ∂h/∂t ≈ κ ▽2h, where κ is a sediment diffusion coefficient that is a function of the bed shear stress (τb) and sediment properties, such as the grain size and the angle of repose. Field observations of waves, currents, and the evolution of large excavated holes (initially 10-m wide and 2-m deep, with sides as steep as 35°) in an energetic surfzone are consistent with diffusive smoothing by gravity. Specifically, comparisons of κ estimated from the measured bed evolution with those estimated with numerical model results for several transport theories suggest that gravity-driven sediment transport dominates the bed evolution, with κ proportional to a power of τb. The models are initiated with observed bathymetry and forced with observed waves and currents. The diffusion coefficients from the measurements and from the model simulations were on average of order 10-5 m2/s, implying evolution time scales of days for features with length scales of 10 m. The dependence of κ on τb varies for different transport theories and for high and low shear stress regimes. The US Army Corps of Engineers Field Research Facility, Duck, NC provided excellent logistical support. Funded by a National Security Science and Engineering Faculty Fellowship, a National Defense Science and Engineering Graduate Fellowship, and the Office of Naval Research.

  15. Correlations between gravitropic curvature and auxin movement across gravistimulated roots of Zea mays

    Science.gov (United States)

    Young, L. M.; Evans, M. L.; Hertel, R.

    1990-01-01

    We compared the kinetics of auxin redistribution across the caps of primary roots of 2-day-old maize (Zea mays, cv Merit) seedlings with the time course of gravitropic curvature. [3H] indoleacetic acid was applied to one side of the cap in an agar donor and radioactivity moving across the cap was collected in an agar receiver applied to the opposite side. Upon gravistimulation the roots first curved upward slightly, then returned to the horizontal and began curving downward, reaching a final angle of about 67 degrees. Movement of label across the caps of gravistimulated roots was asymmetric with preferential downward movement (ratio downward/upward = ca. 1.6, radioactivity collected during the 90 min following beginning of gravistimulation). There was a close correlation between the development of asymmetric auxin movement across the root cap and the rate of curvature, with both values increasing to a maximum and then declining as the roots approached the final angle of curvature. In roots preadapted to gravity (alternate brief stimulation on opposite flanks over a period of 1 hour) the initial phase of upward curvature was eliminated and downward bending began earlier than for controls. The correlation between asymmetric auxin movement and the kinetics of curvature also held in comparisons between control and preadapted roots. Both downward auxin transport asymmetry and downward curvature occurred earlier in preadapted roots than in controls. These findings are consistent with suggestions that the root cap is not only the site of perception but also the location of the initial redistribution of effectors that ultimately leads to curvature.

  16. Transcriptional feedback regulation of YUCCA genes in response to auxin levels in Arabidopsis.

    Science.gov (United States)

    Suzuki, Masashi; Yamazaki, Chiaki; Mitsui, Marie; Kakei, Yusuke; Mitani, Yuka; Nakamura, Ayako; Ishii, Takahiro; Soeno, Kazuo; Shimada, Yukihisa

    2015-08-01

    The IPyA pathway, the major auxin biosynthesis pathway, is transcriptionally regulated through a negative feedback mechanism in response to active auxin levels. The phytohormone auxin plays an important role in plant growth and development, and levels of active free auxin are determined by biosynthesis, conjugation, and polar transport. Unlike conjugation and polar transport, little is known regarding the regulatory mechanism of auxin biosynthesis. We discovered that expression of genes encoding indole-3-pyruvic acid (IPyA) pathway enzymes is regulated by elevated or reduced active auxin levels. Expression levels of TAR2, YUC1, YUC2, YUC4, and YUC6 were downregulated in response to synthetic auxins [1-naphthaleneacetic acid (NAA) and 2,4-dichlorophenoxyacetic acid (2,4-D)] exogenously applied to Arabidopsis thaliana L. seedlings. Concomitantly, reduced levels of endogenous indole-3-acetic acid (IAA) were observed. Alternatively, expression of these YUCCA genes was upregulated by the auxin biosynthetic inhibitor kynurenine in Arabidopsis seedlings, accompanied by reduced IAA levels. These results indicate that expression of YUCCA genes is regulated by active auxin levels. Similar results were also observed in auxin-overproduction and auxin-deficient mutants. Exogenous application of IPyA to Arabidopsis seedlings preincubated with kynurenine increased endogenous IAA levels, while preincubation with 2,4-D reduced endogenous IAA levels compared to seedlings exposed only to IPyA. These results suggest that in vivo conversion of IPyA to IAA was enhanced under reduced auxin levels, while IPyA to IAA conversion was depressed in the presence of excess auxin. Based on these results, we propose that the IPyA pathway is transcriptionally regulated through a negative feedback mechanism in response to active auxin levels.

  17. Pavement cells: a model system for non-transcriptional auxin signalling and crosstalks.

    Science.gov (United States)

    Chen, Jisheng; Wang, Fei; Zheng, Shiqin; Xu, Tongda; Yang, Zhenbiao

    2015-08-01

    Auxin (indole acetic acid) is a multifunctional phytohormone controlling various developmental patterns, morphogenetic processes, and growth behaviours in plants. The transcription-based pathway activated by the nuclear TRANSPORT INHIBITOR RESISTANT 1/auxin-related F-box auxin receptors is well established, but the long-sought molecular mechanisms of non-transcriptional auxin signalling remained enigmatic until very recently. Along with the establishment of the Arabidopsis leaf epidermal pavement cell (PC) as an exciting and amenable model system in the past decade, we began to gain insight into non-transcriptional auxin signalling. The puzzle-piece shape of PCs forms from intercalated or interdigitated cell growth, requiring local intra- and inter-cellular coordination of lobe and indent formation. Precise coordination of this interdigitated pattern requires auxin and an extracellular auxin sensing system that activates plasma membrane-associated Rho GTPases from plants and subsequent downstream events regulating cytoskeletal reorganization and PIN polarization. Apart from auxin, mechanical stress and cytokinin have been shown to affect PC interdigitation, possibly by interacting with auxin signals. This review focuses upon signalling mechanisms for cell polarity formation in PCs, with an emphasis on non-transcriptional auxin signalling in polarized cell expansion and pattern formation and how different auxin pathways interplay with each other and with other signals. © The Author 2015. Published by Oxford University Press on behalf of the Society for Experimental Biology. All rights reserved. For permissions, please email: journals.permissions@oup.com.

  18. Auxins in defense strategies

    Czech Academy of Sciences Publication Activity Database

    Čarná, Mária; Repka, V.; Skůpa, Petr; Šturdík, E.

    2014-01-01

    Roč. 69, č. 10 (2014), s. 1255-1263 ISSN 0006-3088 R&D Projects: GA TA ČR TA01011802 Institutional support: RVO:61389030 Keywords : auxin * defense responses * JA Subject RIV: GF - Plant Pathology, Vermin, Weed, Plant Protection Impact factor: 0.827, year: 2014

  19. Reduced Gravity Studies of Soret Transport Effects in Liquid Fuel Combustion

    Science.gov (United States)

    Shaw, Benjamin D.

    2004-01-01

    Soret transport, which is mass transport driven by thermal gradients, can be important in practical flames as well as laboratory flames by influencing transport of low molecular weight species (e.g., monatomic and diatomic hydrogen). In addition, gas-phase Soret transport of high molecular weight fuel species that are present in practical liquid fuels (e.g., octane or methanol) can be significant in practical flames (Rosner et al., 2000; Dakhlia et al., 2002) and in high pressure droplet evaporation (Curtis and Farrell, 1992), and it has also been shown that Soret transport effects can be important in determining oxygen diffusion rates in certain classes of microgravity droplet combustion experiments (Aharon and Shaw, 1998). It is thus useful to obtain information on flames under conditions where Soret effects can be clearly observed. This research is concerned with investigating effects of Soret transport on combustion of liquid fuels, in particular liquid fuel droplets. Reduced-gravity is employed to provide an ideal (spherically-symmetrical) experimental model with which to investigate effects of Soret transport on combustion. The research will involve performing reduced-gravity experiments on combustion of liquid fuel droplets in environments where Soret effects significantly influence transport of fuel and oxygen to flame zones. Experiments will also be performed where Soret effects are not expected to be important. Droplets initially in the 0.5 to 1 mm size range will be burned. Data will be obtained on influences of Soret transport on combustion characteristics (e.g., droplet burning rates, droplet lifetimes, gas-phase extinction, and transient flame behaviors) under simplified geometrical conditions that are most amenable to theoretical modeling (i.e., spherical symmetry). The experiments will be compared with existing theoretical models as well as new models that will be developed. Normal gravity experiments will also be performed.

  20. Magnetic Field and Gravity Effects on Peristaltic Transport of a Jeffrey Fluid in an Asymmetric Channel

    Directory of Open Access Journals (Sweden)

    A. M. Abd-Alla

    2014-01-01

    Full Text Available In this paper, the peristaltic flow of a Jeffrey fluid in an asymmetric channel has been investigated. Mathematical modeling is carried out by utilizing long wavelength and low Reynolds number assumptions. Closed form expressions for the pressure gradient, pressure rise, stream function, axial velocity, and shear stress on the channel walls have been computed numerically. Effects of the Hartmann number, the ratio of relaxation to retardation times, time-mean flow, the phase angle and the gravity field on the pressure gradient, pressure rise, streamline, axial velocity, and shear stress are discussed in detail and shown graphically. The results indicate that the effect of Hartmann number, ratio of relaxation to retardation times, time-mean flow, phase angle, and gravity field are very pronounced in the peristaltic transport phenomena. Comparison was made with the results obtained in the presence and absence of magnetic field and gravity field.

  1. Momentum and charge transport in non-relativistic holographic fluids from Hořava gravity

    Energy Technology Data Exchange (ETDEWEB)

    Davison, Richard A. [Department of Physics, Harvard University, Cambridge, MA 02138 (United States); Grozdanov, Sašo [Instituut-Lorentz for Theoretical Physics, Leiden University, Niels Bohrweg 2, Leiden 2333 CA (Netherlands); Janiszewski, Stefan [Department of Physics and Astronomy, University of Victoria, Victoria, BC, V8W 3P6 (Canada); Kaminski, Matthias [Department of Physics and Astronomy, University of Alabama, Tuscaloosa, AL 35487 (United States)

    2016-11-28

    We study the linearized transport of transverse momentum and charge in a conjectured field theory dual to a black brane solution of Hořava gravity with Lifshitz exponent z=1. As expected from general hydrodynamic reasoning, we find that both of these quantities are diffusive over distance and time scales larger than the inverse temperature. We compute the diffusion constants and conductivities of transverse momentum and charge, as well the ratio of shear viscosity to entropy density, and find that they differ from their relativistic counterparts. To derive these results, we propose how the holographic dictionary should be modified to deal with the multiple horizons and differing propagation speeds of bulk excitations in Hořava gravity. When possible, as a check on our methods and results, we use the covariant Einstein-Aether formulation of Hořava gravity, along with field redefinitions, to re-derive our results from a relativistic bulk theory.

  2. Auxin influx inhibitors 1-NOA, 2-NOA, and CHPAA interfere with membrane dynamics in tobacco cells

    Czech Academy of Sciences Publication Activity Database

    Laňková, Martina; Smith, R. S.; Pešek, Bedřich; Kubeš, Martin; Zažímalová, Eva; Petrášek, Jan; Hoyerová, Klára

    2010-01-01

    Roč. 61, č. 13 (2010), s. 3589-3598 ISSN 0022-0957 R&D Projects: GA AV ČR KJB600380702; GA MŠk(CZ) LC06034 Grant - others:_(CZ) CZ.2.16/3.1.00/21159 Institutional research plan: CEZ:AV0Z50380511 Keywords : Auxin efflux carrier * auxin influx carrier * auxin transport Subject RIV: EF - Botanics Impact factor: 4.818, year: 2010

  3. Clathrin-Mediated Auxin Efflux and Maxima Regulate Hypocotyl Hook Formation and Light-Stimulated Hook Opening in Arabidopsis.

    Science.gov (United States)

    Yu, Qinqin; Zhang, Ying; Wang, Juan; Yan, Xu; Wang, Chao; Xu, Jian; Pan, Jianwei

    2016-01-04

    The establishment of auxin maxima by PIN-FORMED 3 (PIN3)- and AUXIN RESISTANT 1/LIKE AUX1 (LAX) 3 (AUX1/LAX3)-mediated auxin transport is essential for hook formation in Arabidopsis hypocotyls. Until now, however, the underlying regulatory mechanism has remained poorly understood. Here, we show that loss of function of clathrin light chain CLC2 and CLC3 genes enhanced auxin maxima and thereby hook curvature, alleviated the inhibitory effect of auxin overproduction on auxin maxima and hook curvature, and delayed blue light-stimulated auxin maxima reduction and hook opening. Moreover, pharmacological experiments revealed that auxin maxima formation and hook curvature in clc2 clc3 were sensitive to auxin efflux inhibitors 1-naphthylphthalamic acid and 2,3,5-triiodobenzoic acid but not to the auxin influx inhibitor 1-naphthoxyacetic acid. Live-cell imaging analysis further uncovered that loss of CLC2 and CLC3 function impaired PIN3 endocytosis and promoted its lateralization in the cortical cells but did not affect AUX1 localization. Taken together, these results suggest that clathrin regulates auxin maxima and thereby hook formation through modulating PIN3 localization and auxin efflux, providing a novel mechanism that integrates developmental signals and environmental cues to regulate plant skotomorphogenesis and photomorphogenesis. Copyright © 2016 The Author. Published by Elsevier Inc. All rights reserved.

  4. A rho scaffold integrates the secretory system with feedback mechanisms in regulation of auxin distribution.

    Directory of Open Access Journals (Sweden)

    Ora Hazak

    2010-01-01

    Full Text Available Development in multicellular organisms depends on the ability of individual cells to coordinate their behavior by means of small signaling molecules to form correctly patterned tissues. In plants, a unique mechanism of directional transport of the signaling molecule auxin between cells connects cell polarity and tissue patterning and thus is required for many aspects of plant development. Direction of auxin flow is determined by polar subcellular localization of PIN auxin efflux transporters. Dynamic PIN polar localization results from the constitutive endocytic cycling to and from the plasma membrane, but it is not well understood how this mechanism connects to regulators of cell polarity. The Rho family small GTPases ROPs/RACs are master regulators of cell polarity, however their role in regulating polar protein trafficking and polar auxin transport has not been established. Here, by analysis of mutants and transgenic plants, we show that the ROP interactor and polarity regulator scaffold protein ICR1 is required for recruitment of PIN proteins to the polar domains at the plasma membrane. icr1 mutant embryos and plants display an a array of severe developmental aberrations that are caused by compromised differential auxin distribution. ICR1 functions at the plasma membrane where it is required for exocytosis but does not recycle together with PINs. ICR1 expression is quickly induced by auxin but is suppressed at the positions of stable auxin maxima in the hypophysis and later in the embryonic and mature root meristems. Our results imply that ICR1 is part of an auxin regulated positive feedback loop realized by a unique integration of auxin-dependent transcriptional regulation into ROP-mediated modulation of cell polarity. Thus, ICR1 forms an auxin-modulated link between cell polarity, exocytosis, and auxin transport-dependent tissue patterning.

  5. Antagonistic regulation of PIN phosphorylation by PP2A and PINOID directs auxin flux

    NARCIS (Netherlands)

    Michniewicz, M.; Zago, M.K.; Abas, L.; Weijers, D.; Schweighofer, A.; Meskiene, I.; Heisler, M.G.; Ohno, C.; Zhang, J.; Huang, F.; Schwab, R.; Weigel, D.; Meyerowitz, E.M.; Luschnig, C.; Offringa, R.; Friml, J.

    2007-01-01

    In plants, cell polarity and tissue patterning are connected by intercellular flow of the phytohormone auxin, whose directional signaling depends on polar subcellular localization of PIN auxin transport proteins. The mechanism of polar targeting of PINs or other cargos in plants is largely

  6. Modeling gravity effects on water retention and gas transport characteristics in plant growth substrates

    DEFF Research Database (Denmark)

    Deepagoda Thuduwe Kankanamge Kelum, Chamindu; Jones, Scott B.; Tuller, Markus

    2014-01-01

    utilization to conserve energy and to limit transport costs, native materials mined on Moon or Mars are of primary interest for plant growth media in a future outpost, while terrestrial porous substrates with optimal growth media characteristics will be useful for onboard plant growth during space missions....... Due to limited experimental opportunities and prohibitive costs, liquid and gas behavior in porous substrates under reduced gravity conditions has been less studied and hence remains poorly understood. Based on ground-based measurements, this study examined water retention, oxygen diffusivity and air...... that estimates the gas percolation threshold based on the pore size distribution. The model successfully captured measured data for all investigated media and demonstrated the implications of the poorly-understood shift in gas percolation threshold with improved gas percolation in reduced gravity. Finally, using...

  7. Effect of gravity on colloid transport through water-saturated columns packed with glass beads: modeling and experiments.

    Science.gov (United States)

    Chrysikopoulos, Constantinos V; Syngouna, Vasiliki I

    2014-06-17

    The role of gravitational force on colloid transport in water-saturated columns packed with glass beads was investigated. Transport experiments were performed with colloids (clays: kaolinite KGa-1b, montmorillonite STx-1b). The packed columns were placed in various orientations (horizontal, vertical, and diagonal) and a steady flow rate of Q = 1.5 mL/min was applied in both up-flow and down-flow modes. All experiments were conducted under electrostatically unfavorable conditions. The experimental data were fitted with a newly developed, analytical, one-dimensional, colloid transport model. The effect of gravity is incorporated in the mathematical model by combining the interstitial velocity (advection) with the settling velocity (gravity effect). The results revealed that flow direction influences colloid transport in porous media. The rate of particle deposition was shown to be greater for up-flow than for down-flow direction, suggesting that gravity was a significant driving force for colloid deposition.

  8. Genetic analysis of gravity signal transduction in roots

    Science.gov (United States)

    Masson, Patrick; Strohm, Allison; Baldwin, Katherine

    To grow downward into the soil, roots use gravity as a guide. Specialized cells, named stato-cytes, enable this directional growth response by perceiving gravity. Located in the columella region of the cap, these cells sense a reorientation of the root within the gravity field through the sedimentation of, and/or tension/pressure exerted by, dense amyloplasts. This process trig-gers a gravity signal transduction pathway that leads to a fast alkalinization of the cytoplasm and a change in the distribution of the plasma membrane-associated auxin-efflux carrier PIN3. The latter protein is uniformly distributed within the plasma membrane on all sides of the cell in vertically oriented roots. However, it quickly accumulates at the bottom side upon gravis-timulation. This process correlates with a preferential transport of auxin to the bottom side of the root cap, resulting in a lateral gradient across the tip. This gradient is then transported to the elongation zone where it promotes differential cellular elongation, resulting in downward curvature. We isolated mutations that affect gravity signal transduction at a step that pre-cedes cytoplasmic alkalinization and/or PIN3 relocalization and lateral auxin transport across the cap. arg1 and arl2 mutations identify a common genetic pathway that is needed for all three gravity-induced processes in the cap statocytes, indicating these genes function early in the pathway. On the other hand, adk1 affects gravity-induced PIN3 relocalization and lateral auxin transport, but it does not interfere with cytoplasmic alkalinization. ARG1 and ARL2 encode J-domain proteins that are associated with membranes of the vesicular trafficking path-way whereas ADK1 encodes adenosine kinase, an enzyme that converts adenosine derived from nucleic acid metabolism and the AdoMet cycle into AMP, thereby alleviating feedback inhibi-tion of this important methyl-donor cycle. Because mutations in ARG1 (and ARL2) do not completely eliminate

  9. The Arabidopsis LAZY1 Family Plays a Key Role in Gravity Signaling within Statocytes and in Branch Angle Control of Roots and Shoots.

    Science.gov (United States)

    Taniguchi, Masatoshi; Furutani, Masahiko; Nishimura, Takeshi; Nakamura, Moritaka; Fushita, Toyohito; Iijima, Kohta; Baba, Kenichiro; Tanaka, Hirokazu; Toyota, Masatsugu; Tasaka, Masao; Morita, Miyo Terao

    2017-08-01

    During gravitropism, the directional signal of gravity is perceived by gravity-sensing cells called statocytes, leading to asymmetric distribution of auxin in the responding organs. To identify the genes involved in gravity signaling in statocytes, we performed transcriptome analyses of statocyte-deficient Arabidopsis thaliana mutants and found two candidates from the LAZY1 family, AtLAZY1 / LAZY1-LIKE1 ( LZY1 ) and AtDRO3 / AtNGR1 / LZY2 We showed that LZY1 , LZY2 , and a paralog AtDRO1/AtNGR2/LZY3 are redundantly involved in gravitropism of the inflorescence stem, hypocotyl, and root. Mutations of LZY genes affected early processes in gravity signal transduction without affecting amyloplast sedimentation. Statocyte-specific expression of LZY genes rescued the mutant phenotype, suggesting that LZY genes mediate gravity signaling in statocytes downstream of amyloplast displacement, leading to the generation of asymmetric auxin distribution in gravity-responding organs. We also found that lzy mutations reversed the growth angle of lateral branches and roots. Moreover, expression of the conserved C-terminal region of LZY proteins also reversed the growth direction of primary roots in the lzy mutant background. In lateral root tips of lzy multiple mutants, asymmetric distribution of PIN3 and auxin response were reversed, suggesting that LZY genes regulate the direction of polar auxin transport in response to gravity through the control of asymmetric PIN3 expression in the root cap columella. © 2017 American Society of Plant Biologists. All rights reserved.

  10. Lifshitz black branes and DC transport coefficients in massive Einstein-Maxwell-dilaton gravity

    Science.gov (United States)

    Kuang, Xiao-Mei; Papantonopoulos, Eleftherios; Wu, Jian-Pin; Zhou, Zhenhua

    2018-03-01

    We construct analytical Lifshitz massive black brane solutions in massive Einstein-Maxwell-dilaton gravity theory. We also study the thermodynamics of these black brane solutions and obtain the thermodynamical stability conditions. On the dual nonrelativistic boundary field theory with Lifshitz symmetry, we analytically compute the DC transport coefficients, including the electric conductivity, thermoelectric conductivity, and thermal conductivity. The novel property of our model is that the massive term supports the Lifshitz black brane solutions with z ≠1 in such a way that the DC transport coefficients in the dual field theory are finite. We also find that the Wiedemann-Franz law in this dual boundary field theory is violated, which indicates that it may involve strong interactions.

  11. Genetic Analysis of Gravity Signal Transduction in Arabidopsis thaliana Seedlings

    Science.gov (United States)

    Boonsirichai, K.; Harrison, B.; Stanga, J.; Young, L.-S.; Neal, C.; Sabat, G.; Murthy, N.; Harms, A.; Sedbrook, J.; Masson, P.

    The primary roots of Arabidopsis thaliana seedlings respond to gravity stimulation by developing a tip curvature that results from differential cellular elongation on opposite flanks of the elongation zone. This curvature appears modulated by a lateral gradient of auxin that originates in the gravity-perceiving cells (statocytes) of the root cap through an apparent lateral repositioning of a component the auxin efflux carrier complex within these cells (Friml et al, 2002, Nature 415: 806-809). Unfortunately, little is known about the molecular mechanisms that govern early phases of gravity perception and signal transduction within the root-cap statocytes. We have used a molecular genetic approach to uncover some of these mechanisms. Mutations in the Arabidopsis ARG1 and ARL2 genes, which encode J-domain proteins, resulted in specific alterations in root and hypocotyl gravitropism, without pleiotropic phenotypes. Interestingly, ARG1 and ARL2 appear to function in the same genetic pathway. A combination of molecular genetic, biochemical and cell-biological approaches were used to demonstrate that ARG1 functions in early phases of gravity signal transduction within the root and hypocotyl statocytes, and is needed for efficient lateral auxin transport within the cap. The ARG1 protein is associated with components of the secretory and/or endosomal pathways, suggesting its role in the recycling of components of the auxin efflux carrier complex between plasma membrane and endosome (Boonsirichai et al, 2003, Plant Cell 15:2612-2625). Genetic modifiers of arg1-2 were isolated and shown to enhance the gravitropic defect of arg1-2, while resulting in little or no gravitropic defects in a wild type ARG1 background. A slight tendency for arg1-2;mar1-1 and arg1-2;mar2-1 double-mutant organs to display an opposite gravitropic response compared to wild type suggests that all three genes contribute to the interpretation of the gravity-vector information by seedling organs. The

  12. Shoot-supplied ammonium targets the root auxin influx carrier AUX1 and inhibits lateral root emergence in Arabidopsis

    KAUST Repository

    Li, Baohai

    2011-03-24

    Deposition of ammonium (NH4 +) from the atmosphere is a substantial environmental problem. While toxicity resulting from root exposure to NH4 + is well studied, little is known about how shoot-supplied ammonium (SSA) affects root growth. In this study, we show that SSA significantly affects lateral root (LR) development. We show that SSA inhibits lateral root primordium (LRP) emergence, but not LRP initiation, resulting in significantly impaired LR number. We show that the inhibition is independent of abscisic acid (ABA) signalling and sucrose uptake in shoots but relates to the auxin response in roots. Expression analyses of an auxin-responsive reporter, DR5:GUS, and direct assays of auxin transport demonstrated that SSA inhibits root acropetal (rootward) auxin transport while not affecting basipetal (shootward) transport or auxin sensitivity of root cells. Mutant analyses indicated that the auxin influx carrier AUX1, but not the auxin efflux carriers PIN-FORMED (PIN)1 or PIN2, is required for this inhibition of LRP emergence and the observed auxin response. We found that AUX1 expression was modulated by SSA in vascular tissues rather than LR cap cells in roots. Taken together, our results suggest that SSA inhibits LRP emergence in Arabidopsis by interfering with AUX1-dependent auxin transport from shoot to root. © 2011 Blackwell Publishing Ltd.

  13. Abscisic Acid Regulates Auxin Homeostasis in Rice Root Tips to Promote Root Hair Elongation

    Directory of Open Access Journals (Sweden)

    Tao Wang

    2017-06-01

    Full Text Available Abscisic acid (ABA plays an essential role in root hair elongation in plants, but the regulatory mechanism remains to be elucidated. In this study, we found that exogenous ABA can promote rice root hair elongation. Transgenic rice overexpressing SAPK10 (Stress/ABA-activated protein kinase 10 had longer root hairs; rice plants overexpressing OsABIL2 (OsABI-Like 2 had attenuated ABA signaling and shorter root hairs, suggesting that the effect of ABA on root hair elongation depends on the conserved PYR/PP2C/SnRK2 ABA signaling module. Treatment of the DR5-GUS and OsPIN-GUS lines with ABA and an auxin efflux inhibitor showed that ABA-induced root hair elongation depends on polar auxin transport. To examine the transcriptional response to ABA, we divided rice root tips into three regions: short root hair, long root hair and root tip zones; and conducted RNA-seq analysis with or without ABA treatment. Examination of genes involved in auxin transport, biosynthesis and metabolism indicated that ABA promotes auxin biosynthesis and polar auxin transport in the root tip, which may lead to auxin accumulation in the long root hair zone. Our findings shed light on how ABA regulates root hair elongation through crosstalk with auxin biosynthesis and transport to orchestrate plant development.

  14. ARG1 and ARL2 contribute to gravity signal transduction in the statocytes of Arabidopsis thaliana roots and hypocotyls

    Science.gov (United States)

    Masson, Patrick; Harrison, Benjamin; Stanga, John; Otegui, Marisa; Sedbrook, John

    Gravity is an important cue that plant organs use to guide their growth. Each organ is characterized by a defined gravity set point angle that dictates its optimal orientation within the gravity field. Specialized cells, named statocytes, enable this directional growth response by perceiving gravity via the sedimentation of, and/or tension/pressure exerted by, starch-filled plastids within their cytoplasm. Located in the columella region of the cap in roots and in the endodermis of hypocotyls and stems, these cells modulate the lateral transport of auxin across the corresponding organ in a gravistimulus-dependent manner. Upon plant reorientation within the gravity field, a gravity signal transduction pathway is activated within those cells, which in roots leads to a relocalization of the PIN3 auxin efflux carrier toward the lower membrane and an alkalinization of the cytoplasm. In turn, these events appear to promote a lateral transport of auxin toward the bottom side of the stimulated organ, which promotes a curvature. We previously uncovered ARG1 and ARL2 as essential contributors to these cellular processes. Mutations in these genes result in altered root and hypocotyl gravitropism. In roots, this abnormal growth behavior is associated with a lack of PIN3 relocalization within the statocytes and an absence of preferential downward auxin transport upon gravistimulation. These two genes encode paralogous J-domain proteins that are associated with the plasma membrane and other membranes of the vesicular trafficking pathway, and appear to modulate protein trafficking within the statocytes. An analysis of the root gravitropic phenotypes associated with different double mutant configurations affecting ARG1, ARL2 and PIN3 suggest that all three proteins function in a common gravity-signaling pathway. Surprisingly, when a mutation that affects starch biosynthesis (pgm) is introgressed into an arg1-2 mutant, the gravitropic defects are dramatically enhanced relative to

  15. Auxin inhibits endocytosis and promotes its own efflux from cells

    Czech Academy of Sciences Publication Activity Database

    Paciorek, T.; Zažímalová, Eva; Ruthardt, N.; Petrášek, Jan; Stierhof, Y. D.; Kleine-Vehn, J.; Morris, David; Emans, N.; Jürgens, G.; Geldner, N.; Friml, J.

    2005-01-01

    Roč. 435, č. 7046 (2005), s. 1251-1256 ISSN 0028-0836 R&D Projects: GA AV ČR IAA6038303 Institutional research plan: CEZ:AV0Z50380511 Keywords : Phytohormones * polar auxin transport * plasma membrane Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 29.273, year: 2005

  16. A recovery principle provides insight into auxin pattern control in the Arabidopsis root

    Science.gov (United States)

    Moore, Simon; Liu, Junli; Zhang, Xiaoxian; Lindsey, Keith

    2017-01-01

    Regulated auxin patterning provides a key mechanism for controlling root growth and development. We have developed a data-driven mechanistic model using realistic root geometry and formulated a principle to theoretically investigate quantitative auxin pattern recovery following auxin transport perturbation. This principle reveals that auxin patterning is potentially controlled by multiple combinations of interlinked levels and localisation of influx and efflux carriers. We demonstrate that (1) when efflux carriers maintain polarity but change levels, maintaining the same auxin pattern requires non-uniform and polar distribution of influx carriers; (2) the emergence of the same auxin pattern, from different levels of influx carriers with the same nonpolar localisation, requires simultaneous modulation of efflux carrier level and polarity; and (3) multiple patterns of influx and efflux carriers for maintaining an auxin pattern do not have spatially proportional correlation. This reveals that auxin pattern formation requires coordination between influx and efflux carriers. We further show that the model makes various predictions that can be experimentally validated. PMID:28220889

  17. Suppression of the auxin response pathway enhances susceptibility to Phytophthora cinnamomi while phosphite-mediated resistance stimulates the auxin signalling pathway

    Science.gov (United States)

    2014-01-01

    Background Phytophthora cinnamomi is a devastating pathogen worldwide and phosphite (Phi), an analogue of phosphate (Pi) is highly effective in the control of this pathogen. Phi also interferes with Pi starvation responses (PSR), of which auxin signalling is an integral component. In the current study, the involvement of Pi and the auxin signalling pathways in host and Phi-mediated resistance to P. cinnamomi was investigated by screening the Arabidopsis thaliana ecotype Col-0 and several mutants defective in PSR and the auxin response pathway for their susceptibility to this pathogen. The response to Phi treatment was also studied by monitoring its effect on Pi- and the auxin response pathways. Results Here we demonstrate that phr1-1 (phosphate starvation response 1), a mutant defective in response to Pi starvation was highly susceptible to P. cinnamomi compared to the parental background Col-0. Furthermore, the analysis of the Arabidopsis tir1-1 (transport inhibitor response 1) mutant, deficient in the auxin-stimulated SCF (Skp1 − Cullin − F-Box) ubiquitination pathway was also highly susceptible to P. cinnamomi and the susceptibility of the mutants rpn10 and pbe1 further supported a role for the 26S proteasome in resistance to P. cinnamomi. The role of auxin was also supported by a significant (P < 0.001) increase in susceptibility of blue lupin (Lupinus angustifolius) to P. cinnamomi following treatment with the inhibitor of auxin transport, TIBA (2,3,5-triiodobenzoic acid). Given the apparent involvement of auxin and PSR signalling in the resistance to P. cinnamomi, the possible involvement of these pathways in Phi mediated resistance was also investigated. Phi (especially at high concentrations) attenuates the response of some Pi starvation inducible genes such as AT4, AtACP5 and AtPT2 in Pi starved plants. However, Phi enhanced the transcript levels of PHR1 and the auxin responsive genes (AUX1, AXR1and AXR2), suppressed the primary root

  18. The effect of NGATHA altered activity in auxin signaling pathways within the Arabidopsis gynoecium

    Directory of Open Access Journals (Sweden)

    Irene eMartinez-Fernandez

    2014-05-01

    Full Text Available The four NGATHA genes (NGA form a small subfamily within the large family of B3-domain transcription factors of Arabidopsis thaliana. NGA genes act redundantly to direct the development of the apical tissues of the gynoecium, the style and the stigma. Previous studies indicate that NGA genes could exert this function at least partially by directing the synthesis of auxin at the distal end of the developing gynoecium through the upregulation of two different YUCCA genes, which encode flavin monooxygenases involved in auxin biosynthesis. We have compared three developing pistil transcriptome data sets from wildtype, nga quadruple mutants and a 35S::NGA3 line. The differentially expressed genes showed a significant enrichment for auxin-related genes, supporting the idea of NGA genes as major regulators of auxin accumulation and distribution within the developing gynoecium.We have introduced reporter lines for several of these differentially expressed genes involved in synthesis, transport and response to auxin in NGA gain- and loss-of-function backgrounds. We present here a detailed map of the response of these reporters to NGA misregulation that could help to clarify the role of NGA in auxin-mediated gynoecium morphogenesis. Our data point to a very reduced auxin synthesis in the developing apical gynoecium of nga mutants, likely responsible for the lack of DR5rev::GFP reporter activity observed in these mutants. In addition, NGA altered activity affects the expression of protein kinases that regulate the cellular localization of auxin efflux regulators, and thus likely impact auxin transport. Finally, protein accumulation in pistils of several ARFs was differentially affected by nga mutations or NGA overexpression, suggesting that these accumulation patterns depend not only on auxin distribution but could be also regulated by transcriptional networks involving NGA factors.

  19. Fluid/gravity correspondence: second order transport coefficients in compactified D4-branes

    International Nuclear Information System (INIS)

    Wu, Chao; Chen, Yidian; Huang, Mei

    2017-01-01

    We develop the boundary derivative expansion (BDE) formalism of fluid/gravity correspondence to nonconformal version through the compactified, near-extremal black D4-brane. We offer an explicit calculation of 9 second order transport coefficients, i.e., the τ π , τ π ∗ , τ Π , λ 1,2,3 and ξ 1,2,3 for the strongly coupled, uncharged and nonconformal relativistic fluid which is the holographic dual of compactified, near extremal black D4-brane. We also show that the nonconformal fluid considered in this work is free of causal problem and admits the Haack-Yarom relation 4λ 1 −λ 2 =2ητ π .

  20. Two Paralogous Genes Encoding Auxin Efflux Carrier Differentially Expressed in Bitter Gourd (Momordica charantia

    Directory of Open Access Journals (Sweden)

    Yi-Li Li

    2017-11-01

    Full Text Available The phytohormone auxin regulates various developmental programs in plants, including cell growth, cell division and cell differentiation. The auxin efflux carriers are essential for the auxin transport. To show an involvement of auxin transporters in the coordination of fruit development in bitter gourd, a juicy fruit, we isolated novel cDNAs (referred as McPIN encoding putative auxin efflux carriers, including McPIN1, McPIN2 (allele of McPIN1 and McPIN3, from developing fruits of bitter gourd. Both McPIN1 and McPIN3 genes possess six exons and five introns. Hydropathy analysis revealed that both polypeptides have two hydrophobic regions with five transmembrane segments and a predominantly hydrophilic core. Phylogenetic analyses revealed that McPIN1 shared the highest homology to the group of Arabidopsis, cucumber and tomato PIN1, while McPIN3 belonged to another group, including Arabidopsis and tomato PIN3 as well as PIN4. This suggests different roles for McPIN1 and McPIN3 in auxin transport involved in the fruit development of bitter gourd. Maximum mRNA levels for both genes were detected in staminate and pistillate flowers. McPIN1 is expressed in a particular period of early fruit development but McPIN3 continues to be expressed until the last stage of fruit ripening. Moreover, these two genes are auxin-inducible and qualified as early auxin-response genes. Their expression patterns suggest that these two auxin transporter genes play a pivotal role in fruit setting and development.

  1. Reduced expression of AtNUP62 nucleoporin gene affects auxin response in Arabidopsis

    DEFF Research Database (Denmark)

    Boeglin, Martin; Fuglsang, Anja Thoe; Luu, Doan Trung

    2016-01-01

    seedlings and at the adult stage in stipules of cauline leaves. The atnup62-1 mutant, harbouring a T-DNA insertion in intron 5, was identified as a knock-down mutant. It displayed developmental phenotypes that suggested defects in auxin transport or responsiveness. Atnup62 mutant plantlets were found...... to be hypersensitive to auxin, at the cotyledon and root levels. The phenotype of the AtNUP62-GFP overexpressing line further supported the existence of a link between AtNUP62 and auxin signalling. Furthermore, the atnup62 mutation led to an increase in the activity of the DR5 auxin-responsive promoter, and suppressed...

  2. Auxin as an inducer of asymmetrical division generating the subsidiary cells in stomatal complexes of Zea mays.

    Science.gov (United States)

    Livanos, Pantelis; Giannoutsou, Eleni; Apostolakos, Panagiotis; Galatis, Basil

    2015-01-01

    The data presented in this work revealed that in Zea mays the exogenously added auxins indole-3-acetic acid (IAA) and 1-napthaleneacetic acid (NAA), promoted the establishment of subsidiary cell mother cell (SMC) polarity and the subsequent subsidiary cell formation, while treatment with auxin transport inhibitors 2,3,5-triiodobenzoic acid (TIBA) and 1-napthoxyacetic acid (NOA) specifically blocked SMC polarization and asymmetrical division. Furthermore, in young guard cell mother cells (GMCs) the PIN1 auxin efflux carriers were mainly localized in the transverse GMC faces, while in the advanced GMCs they appeared both in the transverse and the lateral ones adjacent to SMCs. Considering that phosphatidyl-inositol-3-kinase (PI3K) is an active component of auxin signal transduction and that phospholipid signaling contributes in the establishment of polarity, treatments with the specific inhibitor of the PI3K LY294002 were carried out. The presence of LY294002 suppressed polarization of SMCs and prevented their asymmetrical division, whereas combined treatment with exogenously added NAA and LY294002 restricted the promotional auxin influence on subsidiary cell formation. These findings support the view that auxin is involved in Z. mays subsidiary cell formation, probably functioning as inducer of the asymmetrical SMC division. Collectively, the results obtained from treatments with auxin transport inhibitors and the appearance of PIN1 proteins in the lateral GMC faces indicate a local transfer of auxin from GMCs to SMCs. Moreover, auxin signal transduction seems to be mediated by the catalytic function of PI3K.

  3. The pea branching RMS2 gene encodes the PsAFB4/5 auxin receptor and is involved in an auxin-strigolactone regulation loop.

    Science.gov (United States)

    Ligerot, Yasmine; de Saint Germain, Alexandre; Waldie, Tanya; Troadec, Christelle; Citerne, Sylvie; Kadakia, Nikita; Pillot, Jean-Paul; Prigge, Michael; Aubert, Grégoire; Bendahmane, Abdelhafid; Leyser, Ottoline; Estelle, Mark; Debellé, Frédéric; Rameau, Catherine

    2017-12-01

    Strigolactones (SLs) are well known for their role in repressing shoot branching. In pea, increased transcript levels of SL biosynthesis genes are observed in stems of highly branched SL deficient (ramosus1 (rms1) and rms5) and SL response (rms3 and rms4) mutants indicative of negative feedback control. In contrast, the highly branched rms2 mutant has reduced transcript levels of SL biosynthesis genes. Grafting studies and hormone quantification led to a model where RMS2 mediates a shoot-to-root feedback signal that regulates both SL biosynthesis gene transcript levels and xylem sap levels of cytokinin exported from roots. Here we cloned RMS2 using synteny with Medicago truncatula and demonstrated that it encodes a putative auxin receptor of the AFB4/5 clade. Phenotypes similar to rms2 were found in Arabidopsis afb4/5 mutants, including increased shoot branching, low expression of SL biosynthesis genes and high auxin levels in stems. Moreover, afb4/5 and rms2 display a specific resistance to the herbicide picloram. Yeast-two-hybrid experiments supported the hypothesis that the RMS2 protein functions as an auxin receptor. SL root feeding using hydroponics repressed auxin levels in stems and down-regulated transcript levels of auxin biosynthesis genes within one hour. This auxin down-regulation was also observed in plants treated with the polar auxin transport inhibitor NPA. Together these data suggest a homeostatic feedback loop in which auxin up-regulates SL synthesis in an RMS2-dependent manner and SL down-regulates auxin synthesis in an RMS3 and RMS4-dependent manner.

  4. Gravity regulated genes in Arabidopsis thaliana (GENARA experiment)

    Science.gov (United States)

    Boucheron-Dubuisson, Elodie; Carnero-D&íaz, Eugénie; Medina, Francisco Javier; Gasset, Gilbert; Pereda-Loth, Veronica; Graziana, Annick; Mazars, Christian; Le Disquet, Isabelle; Eche, Brigitte; Grat, Sabine; Gauquelin-Koch, Guillemette

    2012-07-01

    In higher plants, post-embryonic development is possible through the expression of a set of genes constituting the morphogenetic program that contribute to the production of tissues and organs during the whole plant life cycle. Plant development is mainly controlled by internal factors such as phytohormones, as well as by environmental factors, among which gravity plays a key role (gravi-morphogenetic program). The GENARA space experiment has been designed with the goal of contributing to a better understanding of this gravi-morphogenetic program through the identification and characterization of some gravity regulated proteins (GR proteins) by using quantitative proteomic methods, and through the study of the impact of plant hormones on the expression of this program. Among plant hormones, auxin is the major regulator of organogenesis. In fact, it affects numerous plant developmental processes, e.g. cell division and elongation, autumnal loss of leaves, and the formation of buds, roots, flowers and fruits. Furthermore, it also plays a key role in the mechanisms of different tropisms (including gravitropism) that modulate fundamental features of plant growth. The expression of significant genes involved in auxin transport and in auxin signal perception in root cells is being studied in space-grown seedlings and compared with the corresponding ground controls. This experiment was scheduled to be performed in The European Modular Cultivation System (EMCS), a new facility for plant cultivation and Plant Molecular Biology studies, at ISS. However only one aspect of this experiment was flown and concerns the qualitative and quantitative changes in membrane proteins supposed to be mainly associated with cell signaling and has been called GENARA A. The second part dealing with the function of auxin in the gravi-morphogenetic program and the alterations induced by microgravity will be studied through mutants affected on biosynthesis, transport or perception of auxin in a

  5. Sensory role of actin in auxin-dependent responses of tobacco BY-2.

    Science.gov (United States)

    Huang, Xiang; Maisch, Jan; Nick, Peter

    2017-11-01

    Polar auxin transport depends on the polar localization of auxin-efflux carriers. The cycling of these carriers between cell interior and plasma membrane depends on actin. The dynamic of actin not only affects auxin transport, but also changes the auxin-responsiveness. To study the potential link between auxin responsiveness and actin dynamics, we investigated developmental responses of the non-transformed BY-2 (Nicotiana tabacum L. cv Bright Yellow 2) cell line and the transgenic BY-2 strain GF11 (stably transformed BY-2 cells with a GFP-fimbrin actin-binding domain 2 construct). The developmental process was divided into three distinct stages: cell cycling, cell elongation and file disintegration. Several phenotypes were measured to monitor the cellular responses to different concentrations of exogenous natural auxin (Indole-3-acetic acid, IAA). We found that auxin stimulated and prolonged the mitotic activity, and delayed the exit from the proliferation phase. However, both responses were suppressed in the GF11 line. At the stationary phase of the cultivation cycle, auxin strongly accelerated the cell file disintegration. Interestingly, it was not suppressed but progressed to a more complete disintegration in the GF11 line. During the cultivation cycle, we also followed the organization of actin in the GF11 line and did not detect any significant difference in actin organization from untreated control or exogenous IAA treatment. Therefore, our findings indicate that the specific differences observed in the GF11 line must be linked with a function of actin that is not structural. It means that there is a sensory role of actin for auxin signaling. Copyright © 2017 Elsevier GmbH. All rights reserved.

  6. Auxin molecular field maps define AUX1 selectivity: many auxin herbicides are not substrates

    Czech Academy of Sciences Publication Activity Database

    Hoyerová, Klára; Hošek, Petr; Quareshy, M.; Li, J.; Klíma, Petr; Kubeš, Martin; Yemm, A. A.; Neve, P.; Tripathi, A.; Bennett, M.J.; Napier, R. M.

    2018-01-01

    Roč. 217, č. 4 (2018), s. 1625-1639 ISSN 0028-646X R&D Projects: GA ČR(CZ) GA16-19557S; GA MŠk LD15137 Grant - others:OPPK(XE) CZ.2.16/3.1.00/21519 Institutional support: RVO:61389030 Keywords : auxin transport * cheminformatics * herbicide * herbicide resistance * molecular field maps * pharmacophore * structure–activity relationship * uptake carrier Subject RIV: ED - Physiology OBOR OECD: Cell biology Impact factor: 7.330, year: 2016

  7. Auxin: Harnessing a loose cannon

    NARCIS (Netherlands)

    Weijers, D.

    2015-01-01

    The auxin receptor TIR1 is an F-box protein functioning in a ubiquitin ligase complex to target repressors for degradation. It is itself an unstable protein, but newly identified mutations protect both TIR1 and its substrates from degradation. These mutations could help in identifying the substrates

  8. ADP1 Affects Plant Architecture by Regulating Local Auxin Biosynthesis

    Science.gov (United States)

    Li, Shibai; Qin, Genji; Novák, Ondřej; Pěnčík, Aleš; Ljung, Karin; Aoyama, Takashi; Liu, Jingjing; Murphy, Angus; Gu, Hongya; Tsuge, Tomohiko; Qu, Li-Jia

    2014-01-01

    Plant architecture is one of the key factors that affect plant survival and productivity. Plant body structure is established through the iterative initiation and outgrowth of lateral organs, which are derived from the shoot apical meristem and root apical meristem, after embryogenesis. Here we report that ADP1, a putative MATE (multidrug and toxic compound extrusion) transporter, plays an essential role in regulating lateral organ outgrowth, and thus in maintaining normal architecture of Arabidopsis. Elevated expression levels of ADP1 resulted in accelerated plant growth rate, and increased the numbers of axillary branches and flowers. Our molecular and genetic evidence demonstrated that the phenotypes of plants over-expressing ADP1 were caused by reduction of local auxin levels in the meristematic regions. We further discovered that this reduction was probably due to decreased levels of auxin biosynthesis in the local meristematic regions based on the measured reduction in IAA levels and the gene expression data. Simultaneous inactivation of ADP1 and its three closest homologs led to growth retardation, relative reduction of lateral organ number and slightly elevated auxin level. Our results indicated that ADP1-mediated regulation of the local auxin level in meristematic regions is an essential determinant for plant architecture maintenance by restraining the outgrowth of lateral organs. PMID:24391508

  9. A role for auxin redistribution in the responses of the root system architecture to phosphate starvation in Arabidopsis.

    Science.gov (United States)

    Nacry, Philippe; Canivenc, Geneviève; Muller, Bertrand; Azmi, Abdelkrim; Van Onckelen, Harry; Rossignol, Michel; Doumas, Patrick

    2005-08-01

    primordia emergence through increased accumulation of auxin or change in sensitivity to auxin in the primordia. Both the strong effect of 2,3,5-triiodobenzoic acid and the phenotype of the auxin-transport mutants (aux1, eir1) suggest that low P availability modifies local auxin concentrations within the root system through changes in auxin transport rather than auxin synthesis.

  10. A novel cell division factor from tobacco 2B-13 cells that induced cell division in auxin-starved tobacco BY-2 cells

    Science.gov (United States)

    Shimizu, Takashi; Eguchi, Kentaro; Nishida, Ikuo; Laukens, Kris; Witters, Erwin; van Onckelen, Harry; Nagata, Toshiyuki

    2006-06-01

    Effects of auxin as plant hormones are widespread; in fact in almost all aspects of plant growth and development auxin plays a pivotal role. Although auxin is required for propagating cell division in plant cells, its effect upon cell division is least understood. If auxin is depleted from the culture medium, cultured cells cease to divide. It has been demonstrated in this context that the addition of auxin to auxin-starved nondividing tobacco BY-2 cells induced semisynchronous cell division. On the other hand, there are some cell lines, named habituated cells, that can grow without auxin. The cause and reason for the habituated cells have not been clarified. A habituated cell line named 2B-13 is derived from the tobacco BY-2 cell line, which has been most intensively studied among plant cell lines. When we tried to find the difference between two cell lines of BY-2 and 2B-13 cells, we found that the addition of culture filtrated from the auxin-habituated 2B-13 cells induced semisynchronous cell division in auxin-starved BY-2 cells. The cell division factor (CDF) that is responsible for inducing cell division in auxin-starved BY-2 cells was purified to near-homogeneity by sequential passage through a hydroxyapatite column, a ConA Sepharose column and a Sephadex gel filtration column. The resulting purified fraction appeared as a single band of high molecular weight on sodium dodecyl sulfate-polyacrylamide gel electrophoresis gels by silver staining and was able to induce cell division in auxin-starved BY-2 cells. Identification of the protein by MALD-TOF-MS/MS revealed that it is structurally related to P-glycoprotein from Gossypioides kirkii, which belongs to ATP-binding cassette (ABC)-transporters. The significance of CDF as a possible ABC-transporter is discussed in relationship to auxin-autotrophic growth and auxin-signaling pathway.

  11. Aluminium-induced reduction of plant growth in alfalfa (Medicago sativa) is mediated by interrupting auxin transport and accumulation in roots

    Science.gov (United States)

    Wang, Shengyin; Ren, Xiaoyan; Huang, Bingru; Wang, Ge; Zhou, Peng; An, Yuan

    2016-01-01

    The objective of this study was to investigate Al3+-induced IAA transport, distribution, and the relation of these two processes to Al3+-inhibition of root growth in alfalfa. Alfalfa seedlings with or without apical buds were exposed to 0 or 100 μM AlCl3 and were foliar sprayed with water or 6 mg L−1 IAA. Aluminium stress resulted in disordered arrangement of cells, deformed cell shapes, altered cell structure, and a shorter length of the meristematic zone in root tips. Aluminium stress significantly decreased the IAA concentration in apical buds and root tips. The distribution of IAA fluorescence signals in root tips was disturbed, and the IAA transportation from shoot base to root tip was inhibited. The highest intensity of fluorescence signals was detected in the apical meristematic zone. Exogenous application of IAA markedly alleviated the Al3+-induced inhibition of root growth by increasing IAA accumulation and recovering the damaged cell structure in root tips. In addition, Al3+ stress up-regulated expression of AUX1 and PIN2 genes. These results indicate that Al3+-induced reduction of root growth could be associated with the inhibitions of IAA synthesis in apical buds and IAA transportation in roots, as well as the imbalance of IAA distribution in root tips. PMID:27435109

  12. Genetic Analysis of Gravity Signal Transduction in Arabidopsis Roots

    Science.gov (United States)

    Masson, Patrick; Strohm, Allison; Barker, Richard; Su, Shih-Heng

    Like most other plant organs, roots use gravity as a directional guide for growth. Specialized cells within the columella region of the root cap (the statocytes) sense the direction of gravity through the sedimentation of starch-filled plastids (amyloplasts). Amyloplast movement and/or pressure on sensitive membranes triggers a gravity signal transduction pathway within these cells, which leads to a fast transcytotic relocalization of plasma-membrane associated auxin-efflux carrier proteins of the PIN family (PIN3 and PIN7) toward the bottom membrane. This leads to a polar transport of auxin toward the bottom flank of the cap. The resulting lateral auxin gradient is then transmitted toward the elongation zones where it triggers a curvature that ultimately leads to a restoration of vertical downward growth. Our laboratory is using strategies derived from genetics and systems biology to elucidate the molecular mechanisms that modulate gravity sensing and signal transduction in the columella cells of the root cap. Our previous research uncovered two J-domain-containing proteins, ARG1 and ARL2, as contributing to this process. Mutations in the corresponding paralogous genes led to alterations of root and hypocotyl gravitropism accompanied by an inability for the statocytes to develop a cytoplasmic alkalinization, relocalize PIN3, and transport auxin laterally, in response to gravistimulation. Both proteins are associated peripherally to membranes belonging to various compartments of the vesicular trafficking pathway, potentially modulating the trafficking of defined proteins between plasma membrane and endosomes. MAR1 and MAR2, on the other end, are distinct proteins of the plastidic outer envelope protein import TOC complex (the transmembrane channel TOC75 and the receptor TOC132, respectively). Mutations in the corresponding genes enhance the gravitropic defects of arg1. Using transformation-rescue experiments with truncated versions of TOC132 (MAR2), we have shown

  13. Thermo-electric transport in gauge/gravity models with momentum dissipation

    Science.gov (United States)

    Amoretti, Andrea; Braggio, Alessandro; Maggiore, Nicola; Magnoli, Nicodemo; Musso, Daniele

    2014-09-01

    We present a systematic definition and analysis of the thermo-electric linear response in gauge/gravity systems focusing especially on models with massive gravity in the bulk and therefore momentum dissipation in the dual field theory. A precise treatment of finite counter-terms proves to be essential to yield a consistent physical picture whose hydrodynamic and beyond-hydrodynamics behaviors noticeably match with field theoretical expectations. The model furnishes a possible gauge/gravity description of the crossover from the quantum-critical to the disorder-dominated Fermi-liquid behaviors, as expected in graphene.

  14. Rice Dwarf Virus P2 Protein Hijacks Auxin Signaling by Directly Targeting the Rice OsIAA10 Protein, Enhancing Viral Infection and Disease Development.

    Directory of Open Access Journals (Sweden)

    Lian Jin

    2016-09-01

    Full Text Available The phytohormone auxin plays critical roles in regulating myriads of plant growth and developmental processes. Microbe infection can disturb auxin signaling resulting in defects in these processes, but the underlying mechanisms are poorly understood. Auxin signaling begins with perception of auxin by a transient co-receptor complex consisting of an F-box transport inhibitor response 1/auxin signaling F-box (TIR1/AFB protein and an auxin/indole-3-acetic acid (Aux/IAA protein. Auxin binding to the co-receptor triggers ubiquitination and 26S proteasome degradation of the Aux/IAA proteins, leading to subsequent events, including expression of auxin-responsive genes. Here we report that Rice dwarf virus (RDV, a devastating pathogen of rice, causes disease symptoms including dwarfing, increased tiller number and short crown roots in infected rice as a result of reduced sensitivity to auxin signaling. The RDV capsid protein P2 binds OsIAA10, blocking the interaction between OsIAA10 and OsTIR1 and inhibiting 26S proteasome-mediated OsIAA10 degradation. Transgenic rice plants overexpressing wild-type or a dominant-negative (degradation-resistant mutant of OsIAA10 phenocopy RDV symptoms are more susceptible to RDV infection; however, knockdown of OsIAA10 enhances the resistance of rice to RDV infection. Our findings reveal a previously unknown mechanism of viral protein reprogramming of a key step in auxin signaling initiation that enhances viral infection and pathogenesis.

  15. 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

  16. Transcriptomic analysis reveals ethylene as stimulator and auxin as regulator of adventitious root formation in petunia cuttings

    Science.gov (United States)

    Druege, Uwe; Franken, Philipp; Lischewski, Sandra; Ahkami, Amir H.; Zerche, Siegfried; Hause, Bettina; Hajirezaei, Mohammad R.

    2014-01-01

    Adventitious root (AR) formation in the stem base (SB) of cuttings is the basis for propagation of many plant species and petunia is used as model to study this developmental process. Following AR formation from 2 to 192 hours post-excision (hpe) of cuttings, transcriptome analysis by microarray revealed a change of the character of the rooting zone from SB to root identity. The greatest shift in the number of differentially expressed genes was observed between 24 and 72 hpe, when the categories storage, mineral nutrient acquisition, anti-oxidative and secondary metabolism, and biotic stimuli showed a notable high number of induced genes. Analyses of phytohormone-related genes disclosed multifaceted changes of the auxin transport system, auxin conjugation and the auxin signal perception machinery indicating a reduction in auxin sensitivity and phase-specific responses of particular auxin-regulated genes. Genes involved in ethylene biosynthesis and action showed a more uniform pattern as a high number of respective genes were generally induced during the whole process of AR formation. The important role of ethylene for stimulating AR formation was demonstrated by the application of inhibitors of ethylene biosynthesis and perception as well as of the precursor aminocyclopropane-1-carboxylic acid, all changing the number and length of AR. A model is proposed showing the putative role of polar auxin transport and resulting auxin accumulation in initiation of subsequent changes in auxin homeostasis and signal perception with a particular role of Aux/IAA expression. These changes might in turn guide the entrance into the different phases of AR formation. Ethylene biosynthesis, which is stimulated by wounding and does probably also respond to other stresses and auxin, acts as important stimulator of AR formation probably via the expression of ethylene responsive transcription factor genes, whereas the timing of different phases seems to be controlled by auxin. PMID

  17. Transcriptomic analysis reveals ethylene as stimulator and auxin as regulator of adventitious root formation in petunia cuttings.

    Science.gov (United States)

    Druege, Uwe; Franken, Philipp; Lischewski, Sandra; Ahkami, Amir H; Zerche, Siegfried; Hause, Bettina; Hajirezaei, Mohammad R

    2014-01-01

    Adventitious root (AR) formation in the stem base (SB) of cuttings is the basis for propagation of many plant species and petunia is used as model to study this developmental process. Following AR formation from 2 to 192 hours post-excision (hpe) of cuttings, transcriptome analysis by microarray revealed a change of the character of the rooting zone from SB to root identity. The greatest shift in the number of differentially expressed genes was observed between 24 and 72 hpe, when the categories storage, mineral nutrient acquisition, anti-oxidative and secondary metabolism, and biotic stimuli showed a notable high number of induced genes. Analyses of phytohormone-related genes disclosed multifaceted changes of the auxin transport system, auxin conjugation and the auxin signal perception machinery indicating a reduction in auxin sensitivity and phase-specific responses of particular auxin-regulated genes. Genes involved in ethylene biosynthesis and action showed a more uniform pattern as a high number of respective genes were generally induced during the whole process of AR formation. The important role of ethylene for stimulating AR formation was demonstrated by the application of inhibitors of ethylene biosynthesis and perception as well as of the precursor aminocyclopropane-1-carboxylic acid, all changing the number and length of AR. A model is proposed showing the putative role of polar auxin transport and resulting auxin accumulation in initiation of subsequent changes in auxin homeostasis and signal perception with a particular role of Aux/IAA expression. These changes might in turn guide the entrance into the different phases of AR formation. Ethylene biosynthesis, which is stimulated by wounding and does probably also respond to other stresses and auxin, acts as important stimulator of AR formation probably via the expression of ethylene responsive transcription factor genes, whereas the timing of different phases seems to be controlled by auxin.

  18. Transcriptomic analysis reveals ethylene as stimulator and auxin as regulator of adventitious root formation in petunia cuttings

    Directory of Open Access Journals (Sweden)

    Uwe eDruege

    2014-09-01

    Full Text Available Adventitious root (AR formation in the stem base of cuttings is the basis for propagation of many plant species and petunia is used as model to study this developmental process. Following AR formation from 2 to 192 hours after excision (hpe of cuttings, transcriptome analysis by microarray revealed a change of the character of the rooting zone from stem base to root identity. The greatest shift in the number of differentially expressed genes was observed between 24 and 72 hpe, when the categories storage, mineral nutrient acquisition, anti-oxidative and secondary metabolism, and biotic stimuli showed a notable high number of induced genes. Analyses of phytohormone-related genes disclosed multifaceted changes of the auxin transport system, auxin conjugation and the auxin signal perception machinery indicating a reduction in auxin sensitivity and phase-specific responses of particular auxin-regulated genes. Genes involved in ethylene biosynthesis and action showed a more uniform pattern as a high number of respective genes were generally induced during the whole process of AR formation. The important role of ethylene for stimulating AR formation was demonstrated by the application of inhibitors of ethylene biosynthesis and perception as well as of the precursor aminocyclopropane-1-carboxylic acid, all changing the number and length of AR. A model is proposed showing the putative role of polar auxin transport and resulting auxin accumulation in initiation of subsequent changes in auxin homeostasis and signal perception with a particular role of Aux/IAA expression. These changes might in turn guide the entrance into the different phases of AR formation. Ethylene biosynthesis, which is stimulated by wounding and does probably also respond to other stresses and auxin, acts as important stimulator of AR formation probably via the expression of ethylene responsive transcription factor genes, whereas the timing of different phases seems to be controlled

  19. Earth System Data Records of Mass Transport from Time-Variable Gravity Data

    Science.gov (United States)

    Zlotnicki, V.; Talpe, M.; Nerem, R. S.; Landerer, F. W.; Watkins, M. M.

    2014-12-01

    Satellite measurements of time variable gravity have revolutionized the study of Earth, by measuring the ice losses of Greenland, Antarctica and land glaciers, changes in groundwater including unsustainable losses due to extraction of groundwater, the mass and currents of the oceans and their redistribution during El Niño events, among other findings. Satellite measurements of gravity have been made primarily by four techniques: satellite tracking from land stations using either lasers or Doppler radio systems, satellite positioning by GNSS/GPS, satellite to satellite tracking over distances of a few hundred km using microwaves, and through a gravity gradiometer (radar altimeters also measure the gravity field, but over the oceans only). We discuss the challenges in the measurement of gravity by different instruments, especially time-variable gravity. A special concern is how to bridge a possible gap in time between the end of life of the current GRACE satellite pair, launched in 2002, and a future GRACE Follow-On pair to be launched in 2017. One challenge in combining data from different measurement systems consists of their different spatial and temporal resolutions and the different ways in which they alias short time scale signals. Typically satellite measurements of gravity are expressed in spherical harmonic coefficients (although expansions in terms of 'mascons', the masses of small spherical caps, has certain advantages). Taking advantage of correlations among spherical harmonic coefficients described by empirical orthogonal functions and derived from GRACE data it is possible to localize the otherwise coarse spatial resolution of the laser and Doppler derived gravity models. This presentation discusses the issues facing a climate data record of time variable mass flux using these different data sources, including its validation.

  20. Gene expression profile of zeitlupe/lov kelch protein1 T-DNA insertion mutants in Arabidopsis thaliana: Downregulation of auxin-inducible genes in hypocotyls.

    Science.gov (United States)

    Saitoh, Aya; Takase, Tomoyuki; Kitaki, Hiroyuki; Miyazaki, Yuji; Kiyosue, Tomohiro

    2015-01-01

    Elongation of hypocotyl cells has been studied as a model for elucidating the contribution of cellular expansion to plant organ growth. ZEITLUPE (ZTL) or LOV KELCH PROTEIN1 (LKP1) is a positive regulator of warmth-induced hypocotyl elongation under white light in Arabidopsis, although the molecular mechanisms by which it promotes hypocotyl cell elongation remain unknown. Microarray analysis showed that 134 genes were upregulated and 204 genes including 15 auxin-inducible genes were downregulated in the seedlings of 2 ztl T-DNA insertion mutants grown under warm conditions with continuous white light. Application of a polar auxin transport inhibitor, an auxin antagonist or an auxin biosynthesis inhibitor inhibited hypocotyl elongation of control seedlings to the level observed with the ztl mutant. Our data suggest the involvement of auxin and auxin-inducible genes in ZTL-mediated hypocotyl elongation.

  1. Vertical Transport of Momentum by the Inertial-Gravity Internal Waves in a Baroclinic Current

    Directory of Open Access Journals (Sweden)

    A. A. Slepyshev

    2017-08-01

    Full Text Available When the internal waves break, they are one of the sources of small-scale turbulence. Small-scale turbulence causes the vertical exchange in the ocean. However, internal waves with regard to the Earth rotation in the presence of vertically inhomogeneous two-dimensional current are able to contribute to the vertical transport. Free inertial-gravity internal waves in a baroclinic current in a boundless basin of a constant depth are considered in the Bussinesq approximation. Boundary value problem of linear approximation for the vertical velocity amplitude of internal waves has complex coefficients when current velocity component, which is transversal to the wave propagation direction, depends on the vertical coordinate (taking into account the rotation of the Earth. Eigenfunction and wave frequency are complex, and it is shown that a weak wave damping takes place. Dispersive relation and wave damping decrement are calculated in the linear approximation. At a fixed wave number damping decrement of the second mode is larger (in the absolute value than the one of the first mode. The equation for vertical velocity amplitude for real profiles of the Brunt – Vaisala frequency and current velocity are numerically solved according to implicit Adams scheme of the third order of accuracy. The dispersive curves of the first two modes do not reach inertial frequency in the low-frequency area due to the effect of critical layers in which wave frequency of the Doppler shift is equal to the inertial one. Termination of the second mode dispersive curves takes place at higher frequency than the one of the first mode. In the second order of the wave amplitude the Stokes drift speed is determined. It is shown that the Stokes drift speed, which is transversal to the wave propagation direction, differs from zero if the transversal component of current velocity depends on the vertical coordinate. In this case, the Stokes drift speed in the second mode is lower than

  2. PIN proteins perform a rate-limiting function in cellular auxin efflux

    Czech Academy of Sciences Publication Activity Database

    Petrášek, Jan; Mravec, J.; Bouchard, R.; Blakeslee, J.J.; Abas, M.; Seifertová, Daniela; Wisniewska, J.; Tadele, Z.; Kubeš, Martin; Čovanová, Milada; Dhonukshe, P.; Skůpa, Petr; Benková, E.; Perry, Lucie; Křeček, Pavel; Lee, O.R.; Fink, G.R.; Geisler, M.; Murphy, A.S.; Luschnig, C.; Zažímalová, Eva; Friml, J.

    2006-01-01

    Roč. 312, č. 5775 (2006), s. 914-918 ISSN 0036-8075 R&D Projects: GA AV ČR IAA6038303; GA MŠk(CZ) LC06034 Institutional research plan: CEZ:AV0Z50380511 Keywords : auxin transport * PIN proteins * PGP transporters * MDR Subject RIV: ED - Physiology Impact factor: 30.028, year: 2006

  3. The MEDIATOR genes MED12 and MED13 control Arabidopsis root system configuration influencing sugar and auxin responses.

    Science.gov (United States)

    Raya-González, Javier; López-Bucio, Jesús Salvador; Prado-Rodríguez, José Carlos; Ruiz-Herrera, León Francisco; Guevara-García, Ángel Arturo; López-Bucio, José

    2017-09-01

    Arabidopsis med12 and med13 mutants exhibit shoot and root phenotypes related to an altered auxin homeostasis. Sucrose supplementation reactivates both cell division and elongation in primary roots as well as auxin-responsive and stem cell niche gene expression in these mutants. An analysis of primary root growth of WT, med12, aux1-7 and med12 aux1 single and double mutants in response to sucrose and/or N-1-naphthylphthalamic acid (NPA) placed MED12 upstream of auxin transport for the sugar modulation of root growth. The MEDIATOR (MED) complex plays diverse functions in plant development, hormone signaling and biotic and abiotic stress tolerance through coordination of transcription. Here, we performed genetic, developmental, molecular and pharmacological analyses to characterize the role of MED12 and MED13 on the configuration of root architecture and its relationship with auxin and sugar responses. Arabidopsis med12 and med13 single mutants exhibit shoot and root phenotypes consistent with altered auxin homeostasis including altered primary root growth, lateral root development, and root hair elongation. MED12 and MED13 were required for activation of cell division and elongation in primary roots, as well as auxin-responsive and stem cell niche gene expression. Remarkably, most of these mutant phenotypes were rescued by supplying sucrose to the growth medium. The growth response of primary roots of WT, med12, aux1-7 and med12 aux1 single and double mutants to sucrose and application of auxin transport inhibitor N-1-naphthylphthalamic acid (NPA) revealed the correlation of med12 phenotype with the activity of the auxin intake permease and suggests that MED12 acts upstream of AUX1 in the root growth response to sugar. These data provide compelling evidence that MEDIATOR links sugar sensing to auxin transport and distribution during root morphogenesis.

  4. ACCERBATIN, a small molecule at the intersection of auxin and reactive oxygen species homeostasis with herbicidal properties.

    Science.gov (United States)

    Hu, Yuming; Depaepe, Thomas; Smet, Dajo; Hoyerova, Klara; Klíma, Petr; Cuypers, Ann; Cutler, Sean; Buyst, Dieter; Morreel, Kris; Boerjan, Wout; Martins, José; Petrášek, Jan; Vandenbussche, Filip; Van Der Straeten, Dominique

    2017-07-10

    The volatile two-carbon hormone ethylene acts in concert with an array of signals to affect etiolated seedling development. From a chemical screen, we isolated a quinoline carboxamide designated ACCERBATIN (AEX) that exacerbates the 1-aminocyclopropane-1-carboxylic acid-induced triple response, typical for ethylene-treated seedlings in darkness. Phenotypic analyses revealed distinct AEX effects including inhibition of root hair development and shortening of the root meristem. Mutant analysis and reporter studies further suggested that AEX most probably acts in parallel to ethylene signaling. We demonstrated that AEX functions at the intersection of auxin metabolism and reactive oxygen species (ROS) homeostasis. AEX inhibited auxin efflux in BY-2 cells and promoted indole-3-acetic acid (IAA) oxidation in the shoot apical meristem and cotyledons of etiolated seedlings. Gene expression studies and superoxide/hydrogen peroxide staining further revealed that the disrupted auxin homeostasis was accompanied by oxidative stress. Interestingly, in light conditions, AEX exhibited properties reminiscent of the quinoline carboxylate-type auxin-like herbicides. We propose that AEX interferes with auxin transport from its major biosynthesis sites, either as a direct consequence of poor basipetal transport from the shoot meristematic region, or indirectly, through excessive IAA oxidation and ROS accumulation. Further investigation of AEX can provide new insights into the mechanisms connecting auxin and ROS homeostasis in plant development and provide useful tools to study auxin-type herbicides. © The Author 2017. Published by Oxford University Press on behalf of the Society for Experimental Biology.

  5. Crystal Growth of ZnSe and Related Ternary Compound Semiconductors by Vapor Transport in Low Gravity

    Science.gov (United States)

    Su, Ching-Hua; Ramachandran, N.

    2013-01-01

    Crystals of ZnSe and related ternary compounds, such as ZnSeS and ZnSeTe, will be grown by physical vapor transport in the Material Science Research Rack (MSRR) on International Space Station (ISS). The objective of the project is to determine the relative contributions of gravity-driven fluid flows to the compositional distribution, incorporation of impurities and defects, and deviation from stoichiometry observed in the crystals grown by vapor transport as results of buoyance-driven convection and growth interface fluctuations caused by irregular fluid-flows on Earth. The investigation consists of extensive ground-based experimental and theoretical research efforts and concurrent flight experimentation. The objectives of the ground-based studies are (1) obtain the experimental data and conduct the analyses required to define the optimum growth parameters for the flight experiments, (2) perfect various characterization techniques to establish the standard procedure for material characterization, (3) quantitatively establish the characteristics of the crystals grown on Earth as a basis for subsequent comparative evaluations of the crystals grown in a low-gravity environment and (4) develop theoretical and analytical methods required for such evaluations. ZnSe and related ternary compounds have been grown by vapor transport technique with real time in-situ non-invasive monitoring techniques. The grown crystals have been characterized extensively by various techniques to correlate the grown crystal properties with the growth conditions.

  6. Characterization of auxin-binding proteins from zucchini plasma membrane

    Science.gov (United States)

    Hicks, G. R.; Rice, M. S.; Lomax, T. L.

    1993-01-01

    We have previously identified two auxin-binding polypeptides in plasma membrane (PM) preparations from zucchini (Cucurbita pepo L.) (Hicks et al. 1989, Proc. Natl. Acad. Sci. USA 86, 4948-4952). These polypeptides have molecular weights of 40 kDa and 42 kDa and label specifically with the photoaffinity auxin analog 5-N3-7-3H-IAA (azido-IAA). Azido-IAA permits both the covalent and radioactive tagging of auxin-binding proteins and has allowed us to characterize further the 40-kDa and 42-kDa polypeptides, including the nature of their attachment to the PM, their relationship to each other, and their potential function. The azido-IAA-labeled polypeptides remain in the pelleted membrane fraction following high-salt and detergent washes, which indicates a tight and possibly integral association with the PM. Two-dimensional electrophoresis of partially purified azido-IAA-labeled protein demonstrates that, in addition to the major isoforms of the 40-kDa and 42-kDa polypeptides, which possess isoelectric points (pIs) of 8.2 and 7.2, respectively, several less abundant isoforms that display unique pIs are apparent at both molecular masses. Tryptic and chymotryptic digestion of the auxin-binding proteins indicates that the 40-kDa and 42-kDa polypeptides are closely related or are modifications of the same polypeptide. Phase extraction with the nonionic detergent Triton X-114 results in partitioning of the azido-IAA-labeled polypeptides into the aqueous (hydrophilic) phase. This apparently paradoxical behavior is also exhibited by certain integral membrane proteins that aggregate to form channels. The results of gel filtration indicate that the auxin-binding proteins do indeed aggregate strongly and that the polypeptides associate to form a dimer or multimeric complex in vivo. These characteristics are consistent with the hypothesis that the 40-kDa and 42-kDa polypeptides are subunits of a multimeric integral membrane protein which has an auxin-binding site, and which may

  7. Halogenated auxins affect microtubules and root elongation in Lactuca sativa

    Science.gov (United States)

    Zhang, N.; Hasenstein, K. H.

    2000-01-01

    We studied the effect of 4,4,4-trifluoro-3-(indole-3-)butyric acid (TFIBA), a recently described root growth stimulator, and 5,6-dichloro-indole-3-acetic acid (DCIAA) on growth and microtubule (MT) organization in roots of Lactuca sativa L. DCIAA and indole-3-butyric acid (IBA) inhibited root elongation and depolymerized MTs in the cortex of the elongation zone, inhibited the elongation of stele cells, and promoted xylem maturation. Both auxins caused the plane of cell division to shift from anticlinal to periclinal. In contrast, TFIBA (100 micromolar) promoted elongation of primary roots by 40% and stimulated the elongation of lateral roots, even in the presence of IBA, the microtubular inhibitors oryzalin and taxol, or the auxin transport inhibitor naphthylphthalamic acid. However, TFIBA inhibited the formation of lateral root primordia. Immunostaining showed that TFIBA stabilized MTs orientation perpendicular to the root axis, doubled the cortical cell length, but delayed xylem maturation. The data indicate that the auxin-induced inhibition of elongation and swelling of roots results from reoriented phragmoplasts, the destabilization of MTs in elongating cells, and promotion of vessel formation. In contrast, TFIBA induced promotion of root elongation by enhancing cell length, prolonging transverse MT orientation, delaying cell and xylem maturation.

  8. Auxin transport routes in plant development

    Czech Academy of Sciences Publication Activity Database

    Petrášek, Jan; Friml, J.

    2009-01-01

    Roč. 136, č. 16 (2009), s. 2675-2688 ISSN 0950-1991 R&D Projects: GA AV ČR KJB600380604 Institutional research plan: CEZ:AV0Z50380511 Keywords : ROOT- HAIR DEVELOPMENT * ARABIDOPSIS-THALIANA * LATERAL ROOT Subject RIV: ED - Physiology Impact factor: 7.194, year: 2009

  9. Functionally different PIN proteins control auxin flux during bulbil development in Agave tequilana.

    Science.gov (United States)

    Abraham Juárez, María Jazmín; Hernández Cárdenas, Rocío; Santoyo Villa, José Natzul; O'Connor, Devin; Sluis, Aaron; Hake, Sarah; Ordaz-Ortiz, José; Terry, Leon; Simpson, June

    2015-07-01

    In Agave tequilana, reproductive failure or inadequate flower development stimulates the formation of vegetative bulbils at the bracteoles, ensuring survival in a hostile environment. Little is known about the signals that trigger this probably unique phenomenon in agave species. Here we report that auxin plays a central role in bulbil development and show that the localization of PIN1-related proteins is consistent with altered auxin transport during this process. Analysis of agave transcriptome data led to the identification of the A. tequilana orthologue of PIN1 (denoted AtqPIN1) and a second closely related gene from a distinct clade reported as 'Sister of PIN1' (denoted AtqSoPIN1). Quantitative real-time reverse transcription-PCR (RT-qPCR) analysis showed different patterns of expression for each gene during bulbil formation, and heterologous expression of the A. tequilana PIN1 and SoPIN1 genes in Arabidopsis thaliana confirmed functional differences between these genes. Although no free auxin was detected in induced pedicel samples, changes in the levels of auxin precursors were observed. Taken as a whole, the data support the model that AtqPIN1 and AtqSoPIN1 have co-ordinated but distinct functions in relation to auxin transport during the initial stages of bulbil formation. © The Author 2015. Published by Oxford University Press on behalf of the Society for Experimental Biology.

  10. A reappraisal of the role of abscisic acid and its interaction with auxin in apical dominance.

    Science.gov (United States)

    Cline, Morris G; Oh, Choonseok

    2006-10-01

    Evidence from pea rms1, Arabidopsis max4 and petunia dad1 mutant studies suggest an unidentified carotenoid-derived/plastid-produced branching inhibitor which moves acropetally from the roots to the shoots and interacts with auxin in the control of apical dominance. Since the plant hormone, abscisic acid (ABA), known to inhibit some growth processes, is also carotenoid derived/plastid produced, and because there has been indirect evidence for its involvement with branching, a re-examination of the role of ABA in apical dominance is timely. Even though it has been determined that ABA probably is not the second messenger for auxin in apical dominance and is not the above-mentioned unidentified branching inhibitor, the similarity of their derivation suggests possible relationships and/or interactions. The classic Thimann-Skoog auxin replacement test for apical dominance with auxin [0.5 % naphthalene acetic acid (NAA)] applied both apically and basally was combined in similar treatments with 1 % ABA in Ipomoea nil (Japanese Morning Glory), Solanum lycopersicum (Better Boy tomato) and Helianthus annuus (Mammoth Grey-striped Sunflower). Auxin, apically applied to the cut stem surface of decapitated shoots, strongly restored apical dominance in all three species, whereas the similar treatment with ABA did not. However, when ABA was applied basally, i.e. below the lateral bud of interest, there was a significant moderate repression of its outgrowth in Ipomoea and Solanum. There was also some additive repression when apical auxin and basal ABA treatments were combined in Ipomoea. The finding that basally applied ABA is able partially to restore apical dominance via acropetal transport up the shoot suggests possible interactions between ABA, auxin and the unidentified carotenoid-derived branching inhibitor that justify further investigation.

  11. Molecular mechanisms of root gravity sensing and signal transduction.

    Science.gov (United States)

    Strohm, Allison K; Baldwin, Katherine L; Masson, Patrick H

    2012-01-01

    Plants use gravity as a guide to direct their roots down into the soil to anchor themselves and to find resources needed for growth and development. In higher plants, the columella cells of the root tip form the primary site of gravity sensing, and in these cells the sedimentation of dense, starch-filled plastids (amyloplasts) triggers gravity signal transduction. This generates an auxin gradient across the root cap that is transmitted to the elongation zone where it promotes differential cell elongation, allowing the root to direct itself downward. It is still not well understood how amyloplast sedimentation leads to auxin redistribution. Models have been proposed to explain how mechanosensitive ion channels or ligand-receptor interactions could connect these events. Although their roles are still unclear, possible second messengers in this process include protons, Ca(2+), and inositol 1,4,5-triphosphate. Upon gravistimulation, the auxin efflux facilitators PIN3 and PIN7 relocalize to the lower side of the columella cells and mediate auxin redistribution. However, evidence for an auxin-independent secondary mechanism of gravity sensing and signal transduction suggests that this physiological process is quite complex. Furthermore, plants must integrate a variety of environmental cues, resulting in multifaceted relationships between gravitropism and other directional growth responses such as hydro-, photo-, and thigmotropism. Copyright © 2011 Wiley Periodicals, Inc.

  12. Effect of gravity on liquid plug transport through an airway bifurcation model.

    Science.gov (United States)

    Zheng, Y; Anderson, J C; Suresh, V; Grotberg, J B

    2005-10-01

    Many medical therapies require liquid plugs to be instilled into and delivered throughout the pulmonary airways. Improving these treatments requires a better understanding of how liquid distributes throughout these airways. In this study, gravitational and surface mechanisms determining the distribution of instilled liquids are examined experimentally using a bench-top model of a symmetrically bifurcating airway. A liquid plug was instilled into the parent tube and driven through the bifurcation by a syringe pump. The effect of gravity was adjusted by changing the roll angle (phi) and pitch angle (gamma) of the bifurcation (phi = gamma =0 deg was isogravitational). Phi determines the relative gravitational orientation of the two daughter tubes: when phi not equal to 0 deg, one daughter tube was lower (gravitationally favored) compared to the other. Gamma determines the component of gravity acting along the axial direction of the parent tube: when gamma not equal to 0 deg, a nonzero component of gravity acts along the axial direction of the parent tube. A splitting ratio Rs, is defined as the ratio of the liquid volume in the upper daughter to the lower just after plug splitting. We measured the splitting ratio, Rs, as a function of: the parent-tube capillary number (Cap); the Bond number (Bo); phi; gamma; and the presence of pre-existing plugs initially blocking either daughter tube. A critical capillary number (Cac) was found to exist below which no liquid entered the upper daughter (Rs = 0), and above which Rs increased and leveled off with Cap. Cac increased while Rs decreased with increasing phi, gamma, and Bo for blocked and unblocked cases at a given Cap > Ca,. Compared to the nonblockage cases, Rs decreased (increased) at a given Cap while Cac increased (decreased) with an upper (lower) liquid blockage. More liquid entered the unblocked daughter with a blockage in one daughter tube, and this effect was larger with larger gravity effect. A simple theoretical

  13. Abscisic acid regulates root growth under osmotic stress conditions via an interacting hormonal network with cytokinin, ethylene and auxin.

    Science.gov (United States)

    Rowe, James H; Topping, Jennifer F; Liu, Junli; Lindsey, Keith

    2016-07-01

    Understanding the mechanisms regulating root development under drought conditions is an important question for plant biology and world agriculture. We examine the effect of osmotic stress on abscisic acid (ABA), cytokinin and ethylene responses and how they mediate auxin transport, distribution and root growth through effects on PIN proteins. We integrate experimental data to construct hormonal crosstalk networks to formulate a systems view of root growth regulation by multiple hormones. Experimental analysis shows: that ABA-dependent and ABA-independent stress responses increase under osmotic stress, but cytokinin responses are only slightly reduced; inhibition of root growth under osmotic stress does not require ethylene signalling, but auxin can rescue root growth and meristem size; osmotic stress modulates auxin transporter levels and localization, reducing root auxin concentrations; PIN1 levels are reduced under stress in an ABA-dependent manner, overriding ethylene effects; and the interplay among ABA, ethylene, cytokinin and auxin is tissue-specific, as evidenced by differential responses of PIN1 and PIN2 to osmotic stress. Combining experimental analysis with network construction reveals that ABA regulates root growth under osmotic stress conditions via an interacting hormonal network with cytokinin, ethylene and auxin. © 2016 The Authors. New Phytologist © 2016 New Phytologist Trust.

  14. Agrobacterium T-DNA-encoded protein Atu6002 interferes with the host auxin response

    Science.gov (United States)

    Lacroix, Benoît; Gizatullina, Diana I.; Babst, Benjamin A.; Gifford, Andrew N.; Citovsky, Vitaly

    2013-01-01

    Summary Several genes in the Agrobacterium tumefaciens transferred (T) DNA encode proteins that are involved in developmental alterations leading to the formation of tumors in infected plants. We investigated the role of the protein encoded by the Atu6002 gene, the function of which is completely unknown. The Atu6002 expression occurs in Agrobacterium-induced tumors, and is also activated upon activation of plant cell division by growth hormones. Within the expressing plant cells, the Atu6002 protein is targeted to the plasma membrane. Interestingly, constitutive ectopic expression of Atu6002 in transgenic tobacco plants lead to a severe developmental phenotype characterized by stunted growth, shorter internodes, lanceolate leaves, increased branching, and modified flower morphology. These Atu6002-expressing plants also displayed impaired response to auxin. However, auxin cellular uptake and polar transport were not significantly inhibited in these plants, suggesting that Atu6002 interferes with auxin perception or signaling pathways. PMID:24128370

  15. Characterization of contaminant transport by gravity, capillarity and barometric pumping in heterogeneous vadose regimes. 1998 annual progress report

    International Nuclear Information System (INIS)

    Carrigan, C.R.; Hudson, G.B.

    1998-01-01

    'The intent of this research program is to obtain an improved understanding of vadose zone transport processes and to develop field and modeling techniques required to characterize contaminant transport in the unsaturated zone at DOE sites. For surface spills and near-surface leaks of chemicals, the vadose zone may well become a long-term source of contamination for the underlying water table. Transport of contaminants can occur in both the liquid and gas phases of the unsaturated zone. This transport occurs naturally as a result of diffusion, buoyancy forces (gravity), capillarity and barometric pressure variations. In some cases transport can be enhanced by anisotropies present in hydrologic regimes. This is particularly true for gas-phase transport which may be subject to vertical pumping resulting from atmospheric pressure changes. For liquid-phase flows, heterogeneity may enhance the downward transport of contaminants to the water table depending on soil properties and the scale of the surface spill or near-surface leak. Characterization techniques based upon the dynamics of transport processes are likely to yield a better understanding of the potential for contaminant transport at a specific site than methods depending solely on hydrologic properties derived from a borehole. Such dynamic-characterization techniques can be useful for evaluating sites where contamination presently exists as well as for providing an objective basis to evaluate the efficacy of proposed as well as implemented clean-up technologies. The real-time monitoring of processes that may occur during clean-up of tank waste and the mobility of contaminants beneath the Hanford storage tanks during sluicing operations is one example of how techniques developed in this effort can be applied to current remediation problems. In the future, such dynamic-characterization methods might also be used as part of the site-characterization process for determining suitable locations of new DOE facilities

  16. The acropetal effects of indole-3-acetic acid in isolated shoot segments of Acer pseudoplatanus L. II. Possible regulation by a vectorial fieid of auxin waves

    Directory of Open Access Journals (Sweden)

    Jacek A. Adamczyk

    2014-01-01

    Full Text Available The acropetal effects of auxin on elongation of axillary buds and on modulation of the wave-like pattern of basipetal efflux of natural auxin to agar from Acer pseudoplatanus L. shoots were studied. When synthetic IAA was applied to cut surfaces of one of two branches the elongation growth of buds situated on the opposite branch was retarded, suggesting regulation independent of the direct action of the molecules of the applied IAA. Oscillations in basipetal transport of natural auxin along the stem segments were observed corroborating the results of other authors using different tree species. Apical application of synthetic IAA for 1 hour to the lateral branch caused a phase shift of the wave-like pattern of basipetal efflux of natural auxin, when the stem segment above the treated branch was sectioned. The same effect was observed evoked by the laterally growing branch which is interpreted as an effect of natural auxin produced by the actively growing shoot. These modulations could be propagated acropetally at a rate excluding direct action of auxin molecules at the sites of measurement. The results seem to corroborate the hypothesis suggesting that auxin is involved in acropetal regulation of shoot apex growth through its effect upon modulation of the vectorial field which arises when the auxin-waves translocate in cambium.

  17. Roles of abscisic acid and auxin in shoot-supplied ammonium inhibition of root system development.

    Science.gov (United States)

    Li, Baohai; Li, Qing; Kronzucker, Herbert J; Shi, Weiming

    2011-10-01

    A plastic root system is a prerequisite for successful plant acclimation to variable environments. The normally functioning root system is the result of a complex interaction of root-borne signals and shoot-derived regulators. We recently demonstrated that AUX1, a well-studied component of auxin transport, mediates shoot-supplied ammonium (SSA) inhibition of lateral root (LR) formation in Arabidopsis. By contrast, the response did not involve ABA pathways, via which several other abiotic stresses affect LR formation. We proposed that SSA regulates LR emergence by interrupting AUX1-mediated auxin transport from shoot to root. Here, by analyzing both ABA- and auxin-related mutants, we show that AUX1 is also required for SSA-mediated suppression of primary root growth. Ammonium content in shoots was furthermore shown to increase linearly with shoot-, but not root-supplied, ammonium, suggesting it may represent the internal trigger for SSA inhibition of root development. Taken together, our data identify AUX1-mediated auxin transport as a key transmission step in the sensing of excessive ammonium exposure and its inhibitory effect on root development. 

  18. Demand estimation of bus as a public transport based on gravity model

    Directory of Open Access Journals (Sweden)

    Asmael Noor

    2018-01-01

    Full Text Available Bus as a public transport is a suitable service to meet the travel demand between any two zones. Baghdad faced with severe traffic problems along with the development in city size and economy. Passengers have to wait lots of time during commutation to work because of the serious traffic jams. In the last years, rate of car ownership has increased as income levels have gone up and cars have become a preferable mode of transport. Bus, as the only public mode of transport available, is suffering from inconvenience, slowness, and inflexibility. A big emphasis must be given to the public transport system because it introduces an active utilization of limited resources, energy and land. This study determines the demand of public routes for buses using boarding / alighting values to generate a model and assign these demand values to the bus network. Five public routes were selected to collect the required data. Ride check and Point check survey was conducted for each selected route. The results of this study were public demand assigned to the selected bus routes, dwell time, load factor and headway. It is observed that R1 and R3 have the heaviest travel demand; they need special study to improve bus performance and make better transit. The model developed with only limited data available to predict travel demand will assist transportation planners and related agencies in decision making.

  19. Arabidopsis TWISTED DWARF1 functionally interacts with Auxin Exporter ABCB1 on the root plasma membrane

    DEFF Research Database (Denmark)

    Wang, Bangjun; Bailly, Aurélien; Zwiewka, Marta

    2013-01-01

    Plant architecture is influenced by the polar, cell-to-cell transport of auxin that is primarily provided and regulated by plasma membrane efflux catalysts of the PIN-FORMED and B family of ABC transporter (ABCB) classes. The latter were shown to require the functionality of the FK506 binding pro...

  20. The Arabidopsis WRINKLED1 transcription factor affects auxin homeostasis in roots.

    Science.gov (United States)

    Kong, Que; Ma, Wei; Yang, Haibing; Ma, Guojie; Mantyla, Jenny J; Benning, Christoph

    2017-07-20

    WRINKLED1 (WRI1) is a key transcriptional regulator of fatty acid biosynthesis genes in diverse oil-containing tissues. Loss of function of Arabidopsis WRI1 leads to a reduction in the expression of genes for fatty acid biosynthesis and glycolysis, and concomitant strong reduction of seed oil content. The wri1-1 loss-of-function mutant shows reduced primary root growth and decreased acidification of the growth medium. The content of a conjugated form of the plant growth hormone auxin, indole-3-acetic acid (IAA)-Asp, was higher in wri1-1 plants compared with the wild-type. GH3.3, a gene encoding an enzyme involved in auxin degradation, displayed higher expression in the wri1-1 mutant. EMSAs demonstrated that AtWRI1 bound to the promoter of GH3.3. Specific AtWRI1-binding motifs were identified in the promoter of GH3.3. In addition, wri1-1 displayed decreased auxin transport. Expression of some PIN genes, which encode IAA carrier proteins, was reduced in wri1-1 plants as well. Correspondingly, AtWRI1 bound to the promoter regions of some PIN genes. It is well known that auxin exerts its maximum effects at a specific, optimal concentration in roots requiring a finely balanced auxin homeostasis. This process appears to be disrupted when the expression of WRI1 and in turn a subset of its target genes are misregulated, highlighting a role for WRI1 in root auxin homeostasis. © The Author 2017. Published by Oxford University Press on behalf of the Society for Experimental Biology.

  1. Lateral root initiation and formation within the parental root meristem of Cucurbita pepo: is auxin a key player?

    Science.gov (United States)

    Ilina, Elena L; Kiryushkin, Alexey S; Semenova, Victoria A; Demchenko, Nikolay P; Pawlowski, Katharina; Demchenko, Kirill N

    2018-04-19

    In some plant families, including Cucurbitaceae, initiation and development of lateral roots (LRs) occur in the parental root apical meristem. The objective of this study was to identify the general mechanisms underlying LR initiation (LRI). Therefore, the first cellular events leading to LRI as well as the role of auxin in this process were studied in the Cucurbita pepo root apical meristem. Transgenic hairy roots harbouring the auxin-responsive promoter DR5 fused to different reporter genes were used for visualizing of cellular auxin response maxima (ARMs) via confocal laser scanning microscopy and 3-D imaging. The effects of exogenous auxin and auxin transport inhibitors on root branching were analysed. The earliest LRI event involved a group of symmetric anticlinal divisions in pericycle cell files at a distance of 250-350 µm from the initial cells. The visualization of the ARMs enabled the precise detection of cells involved in determining the site of LR primordium formation. A local ARM appeared in sister cells of the pericycle and endodermis files before the first division. Cortical cells contributed to LR development after the anticlinal divisions in the pericycle via the formation of an ARM. Exogenous auxins did not increase the total number of LRs and did not affect the LRI index. Although exogenous auxin transport inhibitors acted in different ways, they all reduced the number of LRs formed. Literature data, as well as results obtained in this study, suggest that the formation of a local ARM before the first anticlinal formative divisions is the common mechanism underlying LRI in flowering plants. We propose that the mechanisms of the regulation of root branching are independent of the position of the LRI site relative to the parental root tip.

  2. A novel putative auxin carrier family regulates intracellular auxin homeostasis in plants

    Czech Academy of Sciences Publication Activity Database

    Barbez, E.; Kubeš, Martin; Rolčík, Jakub; Béziat, Ch.; Pěnčík, Aleš; Wang, B.; Rosquete, M. R.; Zhu, J.; Dobrev, Petre; Lee, Y.; Zažímalová, Eva; Petrášek, Jan; Geisler, M.; Friml, J.; Kleine-Vehn, J.

    2012-01-01

    Roč. 485, č. 7396 (2012), s. 119-124 ISSN 0028-0836 R&D Projects: GA MŠk(CZ) LC06034; GA ČR(CZ) GAP305/11/2476; GA ČR(CZ) GAP305/11/0797 Institutional research plan: CEZ:AV0Z50380511 Keywords : auxin * auxin homeostasis * PILS (PIN-likes) Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 38.597, year: 2012

  3. The Clubroot Pathogen (Plasmodiophora brassicae Influences Auxin Signaling to Regulate Auxin Homeostasis in Arabidopsis

    Directory of Open Access Journals (Sweden)

    Linda Jahn

    2013-11-01

    Full Text Available The clubroot disease, caused by the obligate biotrophic protist Plasmodiophora brassicae, affects cruciferous crops worldwide. It is characterized by root swellings as symptoms, which are dependent on the alteration of auxin and cytokinin metabolism. Here, we describe that two different classes of auxin receptors, the TIR family and the auxin binding protein 1 (ABP1 in Arabidopsis thaliana are transcriptionally upregulated upon gall formation. Mutations in the TIR family resulted in more susceptible reactions to the root pathogen. As target genes for the different pathways we have investigated the transcriptional regulation of selected transcriptional repressors (Aux/IAA and transcription factors (ARF. As the TIR pathway controls auxin homeostasis via the upregulation of some auxin conjugate synthetases (GH3, the expression of selected GH3 genes was also investigated, showing in most cases upregulation. A double gh3 mutant showed also slightly higher susceptibility to P. brassicae infection, while all tested single mutants did not show any alteration in the clubroot phenotype. As targets for the ABP1-induced cell elongation the effect of potassium channel blockers on clubroot formation was investigated. Treatment with tetraethylammonium (TEA resulted in less severe clubroot symptoms. This research provides evidence for the involvement of two auxin signaling pathways in Arabidopsis needed for the establishment of the root galls by P. brassicae.

  4. Localized iron supply triggers lateral root elongation in Arabidopsis by altering the AUX1-mediated auxin distribution.

    Science.gov (United States)

    Giehl, Ricardo F H; Lima, Joni E; von Wirén, Nicolaus

    2012-01-01

    Root system architecture depends on nutrient availability, which shapes primary and lateral root development in a nutrient-specific manner. To better understand how nutrient signals are integrated into root developmental programs, we investigated the morphological response of Arabidopsis thaliana roots to iron (Fe). Relative to a homogeneous supply, localized Fe supply in horizontally separated agar plates doubled lateral root length without having a differential effect on lateral root number. In the Fe uptake-defective mutant iron-regulated transporter1 (irt1), lateral root development was severely repressed, but a requirement for IRT1 could be circumvented by Fe application to shoots, indicating that symplastic Fe triggered the local elongation of lateral roots. The Fe-stimulated emergence of lateral root primordia and root cell elongation depended on the rootward auxin stream and was accompanied by a higher activity of the auxin reporter DR5-β-glucuronidase in lateral root apices. A crucial role of the auxin transporter AUXIN RESISTANT1 (AUX1) in Fe-triggered lateral root elongation was indicated by Fe-responsive AUX1 promoter activities in lateral root apices and by the failure of the aux1-T mutant to elongate lateral roots into Fe-enriched agar patches. We conclude that a local symplastic Fe gradient in lateral roots upregulates AUX1 to accumulate auxin in lateral root apices as a prerequisite for lateral root elongation.

  5. In vitro oxidation of indoleacetic acid by soluble auxin-oxidases and peroxidases from maize roots

    International Nuclear Information System (INIS)

    Beffa, R.; Martin, H.V.; Pilet, P.E.

    1990-01-01

    Soluble auxin-oxidases were extracted from Zea mays L. cv LG11 apical root segments and partially separated from peroxidases (EC 1.11.1.7) by size-exclusion chromatography. Auxin-oxidases were resolved into one main peak corresponding to a molecular mass of 32.5 kilodaltons and a minor peak at 54.5 kilodaltons. Peroxidases were separated into at least four peaks, with molecular masses from 32.5 to 78 kilodaltons. In vitro activity of indoleacetic acid-oxidases was dependent on the presence of MnCl 2 and p-coumaric acid. Compound(s) present in the crude extract and several synthetic auxin transport inhibitors (including 2,3,5-triiodobenzoic acid and N-1-naphthylphthalamic acid) inhibited auxin-oxidase activity, but had no effect on peroxidases. The products resulting from the in vitro enzymatic oxidation of [ 3 H]indoleacetic acid were separated by HPLC and the major metabolite was found to cochromatograph with indol-3yl-methanol

  6. Phloem development in nematode-induced feeding sites: The implications of auxin and cytokinin

    Directory of Open Access Journals (Sweden)

    Birgit eAbsmanner

    2013-07-01

    Full Text Available Sedentary plant parasitic nematodes such as root-knot nematodes and cyst nematodes induce giant cells or syncytia, respectively, in their host plant’s roots. These highly specialized structures serve as feeding sites from which exclusively the nematodes withdraw nutrients. While giant cells are symplastically isolated and obtain assimilates by transporter-mediated processes syncytia are massively connected to the phloem by plasmodesmata. To support the feeding sites and the nematode during their development, phloem is induced around syncytia and giant cells. In the case of syncytia the unloading phloem consists of sieve elements and companion cells and in the case of root knots it consists exclusively of sieve elements. We applied immunohistochemistry to identify the cells within the developing phloem that responded to auxin and cytokinin. Both feeding sites themselves did not respond to either hormone. We were able to show that in root knots an auxin response precedes the differentiation of these auxin responsive cells into phloem elements. This process appears to be independent of B-type Arabidopsis response regulators. Using additional markers for tissue identity we provide evidence that around giant cells protophloem is formed and proliferates dramatically. In contrast, the phloem around syncytia responded to both hormones. The presence of companion cells as well as hormone-responsive sieve elements suggests that metaphloem development occurs. The implication of auxin and cytokinin in the further development of the metaphloem is discussed.

  7. Auxin-induced nitric oxide, cGMP and gibberellins were involved in the gravitropism

    Science.gov (United States)

    Cai, Weiming; Hu, Liwei; Hu, Xiangyang; Cui, Dayong; Cai, Weiming

    Gravitropism is the asymmetric growth or curvature of plant organs in response to gravistimulation. There is a complex signal transduction cascade which involved in the differential growth of plants in response to changes in the gravity vector. The role of auxin in gravitropism has been demonstrated by many experiments, but little is known regarding the molecular details of such effects. In our studies before, mediation of the gravitropic bending of soybean roots and rice leaf sheath bases by nitric oxide, cGMP and gibberellins, are induced by auxin. The asymmetrical distribution of nitric oxide, cGMP and gibberellins resulted from the asymmetrical synthesis of them in bending sites. In soybean roots, inhibitions of NO and cGMP synthesis reduced differential NO and cGMP accumulation respectively, which both of these effects can lead to the reduction of gravitropic bending. Gibberellin-induced OsXET, OsEXPA4 and OsRWC3 were also found involved in the gravitropic bending. These data indicated that auxin-induced nitric oxide, cGMP and gibberellins were involved in the gravitropism. More experiments need to prove the more detailed mechanism of them.

  8. The Interaction between Auxin and Nitric Oxide Regulates Root Growth in Response to Iron Deficiency in Rice

    Directory of Open Access Journals (Sweden)

    Huwei Sun

    2017-12-01

    Full Text Available Fe deficiency (-Fe is a common abiotic stress that affects the root development of plants. Auxin and nitric oxide (NO are key regulator of root growth under -Fe. However, the interactions between auxin and NO regulate root growth in response to Fe deficiency are complex and unclear. In this study, the indole-3-acetic acid (IAA and NO levels in roots, and the responses of root growth in rice to different levels of Fe supply were investigated using wild type (WT, ospin1b and osnia2 mutants. -Fe promoted LR formation but inhibited seminal root elongation. IAA levels, [3H] IAA transport, and expression levels of PIN1a-c genes in roots were reduced under -Fe, suggesting that polar auxin transport from shoots to roots was decreased. Application of IAA to -Fe seedlings restored seminal root length, but not LR density, to levels similar to those under normal Fe (+Fe, and the seminal root length was shorter in two ospin1b mutants relative to WT under +Fe, but not under -Fe, confirming that auxin transport participates in -Fe-inhibited seminal root elongation. Moreover, -Fe-induced LR density and -Fe-inhibited seminal root elongation paralleled NO production in roots. Interestingly, similar NO accumulation and responses of LR density and root elongation were observed in osnia2 mutants compared to WT, and the higher expression of NOA gene under -Fe, suggesting that -Fe-induced NO was generated via the NO synthase-like pathway rather than the nitrate reductase pathway. However, IAA could restore the functions of NO in inhibiting seminal root elongation, but did not replace the role of NO-induced LR formation under -Fe. Overall, our findings suggested that NO functions downstream of auxin in regulating LR formation; NO-inhibited seminal root elongation by decreasing meristem activity in root tips under -Fe, with the involvement of auxin.

  9. Hormonal control of root development on epiphyllous plantlets of Bryophyllum (Kalanchoe) marnierianum: role of auxin and ethylene.

    Science.gov (United States)

    Kulka, Richard G

    2008-01-01

    Epiphyllous plantlets develop on leaves of Bryophyllum marnierianum when they are excised from the plant. Shortly after leaf excision, plantlet shoots develop from primordia located near the leaf margin. After the shoots have enlarged for several days, roots appear at their base. In this investigation, factors regulating plantlet root development were studied. The auxin transport inhibitor 2,3,5-triiodobenzoic acid (TIBA) abolished root formation without markedly affecting shoot growth. This suggested that auxin transport from the plantlet shoot induces root development. Excision of plantlet apical buds inhibits root development. Application of indole-3-acetic acid (IAA) in lanolin at the site of the apical buds restores root outgrowth. Naphthalene acetic acid (NAA), a synthetic auxin, reverses TIBA inhibition of plantlet root emergence on leaf explants. Both of these observations support the hypothesis that auxin, produced by the plantlet, induces root development. Exogenous ethylene causes precocious root development several days before that of a control without hormone. Ethylene treatment cannot bypass the TIBA block of root formation. Therefore, ethylene does not act downstream of auxin in root induction. However, ethylene amplifies the effects of low concentrations of NAA, which in the absence of ethylene do not induce roots. Ag(2)S(2)O(3), an ethylene blocker, and CoCl(2), an ethylene synthesis inhibitor, do not abolish plantlet root development. It is therefore unlikely that ethylene is essential for root formation. Taken together, the experiments suggest that roots develop when auxin transport from the shoot reaches a certain threshold. Ethylene may augment this effect by lowering the threshold and may come into play when the parent leaf senesces.

  10. Maize AUXIN-BINDING PROTEIN 1 and AUXIN-BINDING PROTEIN 4 impact on leaf growth, elongation, and seedling responsiveness to auxin and light

    Czech Academy of Sciences Publication Activity Database

    Jurišić-Knežev, Dejana; Čudejková, Mária; Zalabák, David; Hlobilová, Marta; Rolčík, Jakub; Pěnčík, Aleš; Bergougnoux, Véronique; Fellner, Martin

    2012-01-01

    Roč. 90, č. 10 (2012), s. 990-1006 ISSN 1916-2790 R&D Projects: GA MŠk(CZ) 1P05ME792 Institutional research plan: CEZ:AV0Z50380511 Keywords : auxin * auxin-binding protein * growth Subject RIV: EF - Botanics Impact factor: 1.225, year: 2012

  11. Roles of abscisic acid and auxin in shoot-supplied ammonium inhibition of root system development

    OpenAIRE

    Li, Baohai; Li, Qing; Kronzucker, Herbert J; Shi, Weiming

    2011-01-01

    A plastic root system is a prerequisite for successful plant acclimation to variable environments. The normally functioning root system is the result of a complex interaction of root-borne signals and shoot-derived regulators. We recently demonstrated that AUX1, a well-studied component of auxin transport, mediates shoot-supplied ammonium (SSA) inhibition of lateral root (LR) formation in Arabidopsis. By contrast, the response did not involve ABA pathways, via which several other abiotic stre...

  12. Onset of cell division in maize germination: action of auxins

    International Nuclear Information System (INIS)

    de Jimenez, E.S.; Baiza, A.; Aguilar, R.

    1987-01-01

    Seed germination implies metabolic reactivation, synthesis of macromolecules and onset of cell division. During maize germination, meristematic tissues of embryos re-initiate cell division asynchronically. Since auxins are known to stimulate cell division, they asked how auxins might regulate cell cycle re-initiation. Embryonic tissues were incubated with and without auxins. A pulse of either 3 H-thymidine or 32 P-ortophosphate was given to the tissues. Mitotic indexes were determined and % of labeled mitotic cells recorded. Results indicated that meristematic cells re-initiate cell division either from G 1 or G 2 phases. Auxin stimulated differentially the cell division process of these cells. 32 P incorporation into cytoplasmic or nucleic histones was measured. Auxins stimulated this incorporation. Active turnover of histone phosphorylation occurred simultaneously to the cell division process. It is suggested that auxins might regulate the cell cycle by phosphorylation-dephosphorylation of histones

  13. L-Cysteine inhibits root elongation through auxin/PLETHORA and SCR/SHR pathway in Arabidopsis thaliana.

    Science.gov (United States)

    Wang, Zhen; Mao, Jie-Li; Zhao, Ying-Jun; Li, Chuan-You; Xiang, Cheng-Bin

    2015-02-01

    L-Cysteine plays a prominent role in sulfur metabolism of plants. However, its role in root development is largely unknown. Here, we report that L-cysteine reduces primary root growth in a dosage-dependent manner. Elevating cellular L-cysteine level by exposing Arabidopsis thaliana seedlings to high L-cysteine, buthionine sulphoximine, or O-acetylserine leads to altered auxin maximum in root tips, the expression of quiescent center cell marker as well as the decrease of the auxin carriers PIN1, PIN2, PIN3, and PIN7 of primary roots. We also show that high L-cysteine significantly reduces the protein level of two sets of stem cell specific transcription factors PLETHORA1/2 and SCR/SHR. However, L-cysteine does not downregulate the transcript level of PINs, PLTs, or SCR/SHR, suggesting that an uncharacterized post-transcriptional mechanism may regulate the accumulation of PIN, PLT, and SCR/SHR proteins and auxin transport in the root tips. These results suggest that endogenous L-cysteine level acts to maintain root stem cell niche by regulating basal- and auxin-induced expression of PLT1/2 and SCR/SHR. L-Cysteine may serve as a link between sulfate assimilation and auxin in regulating root growth. © 2014 Institute of Botany, Chinese Academy of Sciences.

  14. [Aerobic methylobacteria are capable of synthesizing auxins].

    Science.gov (United States)

    Ivanova, E G; Doronina, N V; Trotsenko, Iu A

    2001-01-01

    Obligately and facultatively methylotrophic bacteria with different pathways of C1 metabolism were found to be able to produce auxins, particularly indole-3-acetic acid (IAA), in amounts of 3-100 micrograms/ml. Indole-3-pyruvic acid and indole-3-acetamide were detected only in methylobacteria with the serine pathway of C1 metabolism, Methylobacterium mesophilicum and Aminobacter aminovorans. The production of auxins by methylobacteria was stimulated by the addition of tryptophan to the growth medium and was inhibited by ammonium ions. The methylobacteria under study lacked tryptophan decarboxylase and tryptophan side-chain oxidase. At the same time, they were found to contain several aminotransferases. IAA is presumably synthesized by methylobacteria through indole-3-pyruvic acid.

  15. Points of regulation for auxin action

    Czech Academy of Sciences Publication Activity Database

    Zažímalová, Eva; Napier, R. M.

    2003-01-01

    Roč. 21, č. 7 (2003), s. 625-634 ISSN 0721-7714 R&D Projects: GA MŠk LN00A081 Grant - others:EU INCO COPERNICUS(XE) ERBIC15 CT98 0118 Institutional research plan: CEZ:AV0Z5038910 Keywords : Plant hormone * Homeostasis * Auxin Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 1.423, year: 2003

  16. Using ocean bottom pressure from the gravity recovery and climate experiment (GRACE) to estimate transport variability in the southern Indian Ocean

    Science.gov (United States)

    Makowski, Jessica K.; Chambers, Don P.; Bonin, Jennifer A.

    2015-06-01

    Previous studies have suggested that ocean bottom pressure (OBP) from the Gravity Recovery and Climate Experiment (GRACE) can be used to measure the depth-averaged, or barotropic, transport variability of the Antarctic Circumpolar Current (ACC). Here, we use GRACE OBP observations to calculate transport variability in a region of the southern Indian Ocean encompassing the major fronts of the ACC. We use a statistical analysis of a simulated GRACE-like data set to determine the uncertainty of the estimated transport for the 2003.0-2013.0 time period. We find that when the transport is averaged over 60° of longitude, the uncertainty (one standard error) is close to 1 Sv (1 Sv = 106 m3 s-1) for low-pass filtered transport, which is significantly smaller than the signal and lower than previous studies have found. The interannual variability is correlated with the Southern Annual mode (SAM) (0.61), but more highly correlated with circumpolar zonally averaged winds between 45°S and 65°S (0.88). GRACE transport reflects significant changes in transport between 2007 and 2009 that is observed in the zonal wind variations but not in the SAM index. We also find a statistically significant trend in transport (-1.0 ± 0.4 Sv yr-1, 90% confidence) that is correlated with a local deceleration in zonal winds related to an asymmetry in the SAM on multidecadal periods.

  17. Auxin production in the endosperm drives seed coat development in Arabidopsis

    Science.gov (United States)

    Figueiredo, Duarte D; Batista, Rita A; Roszak, Pawel J; Hennig, Lars; Köhler, Claudia

    2016-01-01

    In flowering plants, seed development is initiated by the fusion of the maternal egg and central cells with two paternal sperm cells, leading to the formation of embryo and endosperm, respectively. The fertilization products are surrounded by the maternally derived seed coat, whose development prior to fertilization is blocked by epigenetic regulators belonging to the Polycomb Group (PcG) protein family. Here we show that fertilization of the central cell results in the production of auxin and most likely its export to the maternal tissues, which drives seed coat development by removing PcG function. We furthermore show that mutants for the MADS-box transcription factor AGL62 have an impaired transport of auxin from the endosperm to the integuments, which results in seed abortion. We propose that AGL62 regulates auxin transport from the endosperm to the integuments, leading to the removal of the PcG block on seed coat development. DOI: http://dx.doi.org/10.7554/eLife.20542.001 PMID:27848912

  18. Sequential induction of auxin efflux and influx carriers regulates lateral root emergence.

    Science.gov (United States)

    Péret, Benjamin; Middleton, Alistair M; French, Andrew P; Larrieu, Antoine; Bishopp, Anthony; Njo, Maria; Wells, Darren M; Porco, Silvana; Mellor, Nathan; Band, Leah R; Casimiro, Ilda; Kleine-Vehn, Jürgen; Vanneste, Steffen; Sairanen, Ilkka; Mallet, Romain; Sandberg, Göran; Ljung, Karin; Beeckman, Tom; Benkova, Eva; Friml, Jiří; Kramer, Eric; King, John R; De Smet, Ive; Pridmore, Tony; Owen, Markus; Bennett, Malcolm J

    2013-10-22

    In Arabidopsis, lateral roots originate from pericycle cells deep within the primary root. New lateral root primordia (LRP) have to emerge through several overlaying tissues. Here, we report that auxin produced in new LRP is transported towards the outer tissues where it triggers cell separation by inducing both the auxin influx carrier LAX3 and cell-wall enzymes. LAX3 is expressed in just two cell files overlaying new LRP. To understand how this striking pattern of LAX3 expression is regulated, we developed a mathematical model that captures the network regulating its expression and auxin transport within realistic three-dimensional cell and tissue geometries. Our model revealed that, for the LAX3 spatial expression to be robust to natural variations in root tissue geometry, an efflux carrier is required--later identified to be PIN3. To prevent LAX3 from being transiently expressed in multiple cell files, PIN3 and LAX3 must be induced consecutively, which we later demonstrated to be the case. Our study exemplifies how mathematical models can be used to direct experiments to elucidate complex developmental processes.

  19. The role of auxin and cytokinin signalling in specifying the root architecture of Arabidopsis thaliana

    KAUST Repository

    Muraro, Daniele

    2013-01-01

    Auxin and cytokinin are key hormonal signals that control the cellular architecture of the primary root and the initiation of new lateral root organs in the plant Arabidopsis thaliana. Both developmental processes are regulated by cross-talk between these hormones and their signalling pathways. In this paper, sub-cellular and multi-cellular mathematical models are developed to investigate how interactions between auxin and cytokinin influence the size and location of regions of division and differentiation within the primary root, and describe how their cross-regulation may cause periodic branching of lateral roots. We show how their joint activity may influence tissue-specific oscillations in gene expression, as shown in Moreno-Risueno et al. (2010) and commented upon in Traas and Vernoux (2010), and we propose mechanisms that may generate synchronisation of such periodic behaviours inside a cell and with its neighbours. Using a multi-cellular model, we also analyse the roles of cytokinin and auxin in specifying the three main regions of the primary root (elongation, transition and division zones), our simulation results being in good agreement with independent experimental observations. We then use our model to generate testable predictions concerning the effect of varying the concentrations of the auxin efflux transporters on the sizes of the different root regions. In particular, we predict that over-expression of the transporters will generate a longer root with a longer elongation zone and a smaller division zone than that of a wild type root. This root will contain fewer cells than its wild type counterpart. We conclude that our model can provide a useful tool for investigating the response of cell division and elongation to perturbations in hormonal signalling. © 2012 Elsevier Ltd.

  20. The PIN1 family gene PvPIN1 is involved in auxin-dependent root emergence and tillering in switchgrass

    Directory of Open Access Journals (Sweden)

    Kaijie Xu

    2016-03-01

    Full Text Available Abstract Switchgrass (Panicum virgatum L.; family Poaceae is a warm-season C4 perennial grass. Tillering plays an important role in determining the morphology of aboveground parts and the final biomass yield of switchgrass. Auxin distribution in plants can affect a variety of important growth and developmental processes, including the regulation of shoot and root branching, plant resistance and biological yield. Auxin transport and gradients in plants are mediated by influx and efflux carriers. PvPIN1, a switchgrass PIN1-like gene that is involved in regulating polar transport, is a putative auxin efflux carrier. Neighbor-joining analysis using sequences deposited in NCBI databases showed that the PvPIN1gene belongs to the PIN1 family and is evolutionarily closer to the Oryza sativa japonica group. Tiller emergence and development was significantly promoted in plants subjected toPvPIN1 RNA interference (RNAi, which yielded a phenotype similar to that of wild-type plants treated with the auxin transport inhibitor TIBA (2,3,5-triiodobenzoic acid. A transgenic approach that inducedPvPIN1 gene overexpression or suppression altered tiller number and the shoot/root ratio. These data suggest that PvPIN1plays an important role in auxin-dependent adventitious root emergence and tillering.

  1. Massive Gravity

    OpenAIRE

    de Rham, Claudia

    2014-01-01

    We review recent progress in massive gravity. We start by showing how different theories of massive gravity emerge from a higher-dimensional theory of general relativity, leading to the Dvali–Gabadadze–Porrati model (DGP), cascading gravity, and ghost-free massive gravity. We then explore their theoretical and phenomenological consistency, proving the absence of Boulware–Deser ghosts and reviewing the Vainshtein mechanism and the cosmological solutions in these models. Finally, we present alt...

  2. Noncoding transcription by alternative rna polymerases dynamically regulates an auxin-driven chromatin loop

    KAUST Repository

    Ariel, Federico D.; Jé gu, Teddy; Latrasse, David; Romero-Barrios, Natali; Christ, Auré lie; Benhamed, Moussa; Crespi, Martí n D.

    2014-01-01

    The eukaryotic epigenome is shaped by the genome topology in three-dimensional space. Dynamic reversible variations in this epigenome structure directly influence the transcriptional responses to developmental cues. Here, we show that the Arabidopsis long intergenic noncoding RNA (lincRNA) APOLO is transcribed by RNA polymerases II and V in response to auxin, a phytohormone controlling numerous facets of plant development. This dual APOLO transcription regulates the formation of a chromatin loop encompassing the promoter of its neighboring gene PID, a key regulator of polar auxin transport. Altering APOLO expression affects chromatin loop formation, whereas RNA-dependent DNA methylation, active DNA demethylation, and Polycomb complexes control loop dynamics. This dynamic chromatin topology determines PID expression patterns. Hence, the dual transcription of a lincRNA influences local chromatin topology and directs dynamic auxin-controlled developmental outputs on neighboring genes. This mechanism likely underscores the adaptive success of plants in diverse environments and may be widespread in eukaryotes. © 2014 Elsevier Inc.

  3. A physico-genetic module for the polarisation of auxin efflux carriers PIN-FORMED (PIN)

    Science.gov (United States)

    Hernández-Hernández, Valeria; Barrio, Rafael A.; Benítez, Mariana; Nakayama, Naomi; Romero-Arias, José Roberto; Villarreal, Carlos

    2018-05-01

    Intracellular polarisation of auxin efflux carriers is crucial for understanding how auxin gradients form in plants. The polarisation dynamics of auxin efflux carriers PIN-FORMED (PIN) depends on both biomechanical forces as well as chemical, molecular and genetic factors. Biomechanical forces have shown to affect the localisation of PIN transporters to the plasma membrane. We propose a physico-genetic module of PIN polarisation that integrates biomechanical, molecular, and cellular processes as well as their non-linear interactions. The module was implemented as a discrete Boolean model and then approximated to a continuous dynamic system, in order to explore the relative contribution of the factors mediating PIN polarisation at the scale of single cell. Our models recovered qualitative behaviours that have been experimentally observed and enable us to predict that, in the context of PIN polarisation, the effects of the mechanical forces can predominate over the activity of molecular factors such as the GTPase ROP6 and the ROP-INTERACTIVE CRIB MOTIF-CONTAINING PROTEIN RIC1.

  4. Noncoding transcription by alternative rna polymerases dynamically regulates an auxin-driven chromatin loop

    KAUST Repository

    Ariel, Federico D.

    2014-08-01

    The eukaryotic epigenome is shaped by the genome topology in three-dimensional space. Dynamic reversible variations in this epigenome structure directly influence the transcriptional responses to developmental cues. Here, we show that the Arabidopsis long intergenic noncoding RNA (lincRNA) APOLO is transcribed by RNA polymerases II and V in response to auxin, a phytohormone controlling numerous facets of plant development. This dual APOLO transcription regulates the formation of a chromatin loop encompassing the promoter of its neighboring gene PID, a key regulator of polar auxin transport. Altering APOLO expression affects chromatin loop formation, whereas RNA-dependent DNA methylation, active DNA demethylation, and Polycomb complexes control loop dynamics. This dynamic chromatin topology determines PID expression patterns. Hence, the dual transcription of a lincRNA influences local chromatin topology and directs dynamic auxin-controlled developmental outputs on neighboring genes. This mechanism likely underscores the adaptive success of plants in diverse environments and may be widespread in eukaryotes. © 2014 Elsevier Inc.

  5. Hydrogen Gas Is Involved in Auxin-Induced Lateral Root Formation by Modulating Nitric Oxide Synthesis

    Directory of Open Access Journals (Sweden)

    Zeyu Cao

    2017-10-01

    Full Text Available Metabolism of molecular hydrogen (H2 in bacteria and algae has been widely studied, and it has attracted increasing attention in the context of animals and plants. However, the role of endogenous H2 in lateral root (LR formation is still unclear. Here, our results showed that H2-induced lateral root formation is a universal event. Naphthalene-1-acetic acid (NAA; the auxin analog was able to trigger endogenous H2 production in tomato seedlings, and a contrasting response was observed in the presence of N-1-naphthyphthalamic acid (NPA, an auxin transport inhibitor. NPA-triggered the inhibition of H2 production and thereafter lateral root development was rescued by exogenously applied H2. Detection of endogenous nitric oxide (NO by the specific probe 4-amino-5-methylamino-2′,7′-difluorofluorescein diacetate (DAF-FM DA and electron paramagnetic resonance (EPR analyses revealed that the NO level was increased in both NAA- and H2-treated tomato seedlings. Furthermore, NO production and thereafter LR formation induced by auxin and H2 were prevented by 2-4-carboxyphenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (cPTIO; a specific scavenger of NO and the inhibitor of nitrate reductase (NR; an important NO synthetic enzyme. Molecular evidence confirmed that some representative NO-targeted cell cycle regulatory genes were also induced by H2, but was impaired by the removal of endogenous NO. Genetic evidence suggested that in the presence of H2, Arabidopsis mutants nia2 (in particular and nia1 (two nitrate reductases (NR-defective mutants exhibited defects in lateral root length. Together, these results demonstrated that auxin-induced H2 production was associated with lateral root formation, at least partially via a NR-dependent NO synthesis.

  6. The role of auxin in temperature regulated hypocotyl elongation

    Energy Technology Data Exchange (ETDEWEB)

    Estelle, Mark [Univ. of California, San Diego, CA (United States)

    2015-10-02

    The major goal of this project was to determine how auxin mediates the response of Arabidopsis seedlings to increased ambient temperature. Previous studies have shown that the response is due, in part, to increased auxin biosynthesis via the IPA auxin biosynthetic pathway. This effect is related to increased transcription of genes that encode enzymes in this pathway. However, during the last year we have shown that transcription of key auxin regulated genes increases within minutes of a shift to elevated temperature. This response is probably to rapid to be explained by changes in the levels of auxin biosynthetic enzymes. Interestingly, we have recently discovered that temperature shift is associated with a rapid increase in the level of the auxin co-receptor TIR1. This change appears is the result of increased stability of the protein. At the same time, we have discovered that stability of TIR1 is dependent on the chaperone HSP9o and its co-chaperone SGT1. By using the specific HSP90 inhibitor GDA, we show that HSP90 is required for the temperature dependent change in TIR1 levels. We have also shown that HSP90 and SGT1 interact directly with TIR1. Our results also lead us to propose a new model in which the plant responds rapidly to changes in ambient temperature by directly regulating the TIR1/AFB receptor system, thus modulating the auxin signaling pathway.

  7. Sites and regulation of auxin biosynthesis in Arabidopsis roots.

    Science.gov (United States)

    Ljung, Karin; Hull, Anna K; Celenza, John; Yamada, Masashi; Estelle, Mark; Normanly, Jennifer; Sandberg, Göran

    2005-04-01

    Auxin has been shown to be important for many aspects of root development, including initiation and emergence of lateral roots, patterning of the root apical meristem, gravitropism, and root elongation. Auxin biosynthesis occurs in both aerial portions of the plant and in roots; thus, the auxin required for root development could come from either source, or both. To monitor putative internal sites of auxin synthesis in the root, a method for measuring indole-3-acetic acid (IAA) biosynthesis with tissue resolution was developed. We monitored IAA synthesis in 0.5- to 2-mm sections of Arabidopsis thaliana roots and were able to identify an important auxin source in the meristematic region of the primary root tip as well as in the tips of emerged lateral roots. Lower but significant synthesis capacity was observed in tissues upward from the tip, showing that the root contains multiple auxin sources. Root-localized IAA synthesis was diminished in a cyp79B2 cyp79B3 double knockout, suggesting an important role for Trp-dependent IAA synthesis pathways in the root. We present a model for how the primary root is supplied with auxin during early seedling development.

  8. Localized Iron Supply Triggers Lateral Root Elongation in Arabidopsis by Altering the AUX1-Mediated Auxin Distribution[C][W][OA

    Science.gov (United States)

    Giehl, Ricardo F.H.; Lima, Joni E.; von Wirén, Nicolaus

    2012-01-01

    Root system architecture depends on nutrient availability, which shapes primary and lateral root development in a nutrient-specific manner. To better understand how nutrient signals are integrated into root developmental programs, we investigated the morphological response of Arabidopsis thaliana roots to iron (Fe). Relative to a homogeneous supply, localized Fe supply in horizontally separated agar plates doubled lateral root length without having a differential effect on lateral root number. In the Fe uptake-defective mutant iron-regulated transporter1 (irt1), lateral root development was severely repressed, but a requirement for IRT1 could be circumvented by Fe application to shoots, indicating that symplastic Fe triggered the local elongation of lateral roots. The Fe-stimulated emergence of lateral root primordia and root cell elongation depended on the rootward auxin stream and was accompanied by a higher activity of the auxin reporter DR5-β-glucuronidase in lateral root apices. A crucial role of the auxin transporter AUXIN RESISTANT1 (AUX1) in Fe-triggered lateral root elongation was indicated by Fe-responsive AUX1 promoter activities in lateral root apices and by the failure of the aux1-T mutant to elongate lateral roots into Fe-enriched agar patches. We conclude that a local symplastic Fe gradient in lateral roots upregulates AUX1 to accumulate auxin in lateral root apices as a prerequisite for lateral root elongation. PMID:22234997

  9. ER-localized auxin transporter PIN8 regulates auxin homeostasis and male gametophyte development in Arabidopsis

    Czech Academy of Sciences Publication Activity Database

    Ding, Z.; Wang, B.; Moreno, I.; Dupľáková, Nikoleta; Sibu, S.; Carraro, N.; Reemmer, J.; Pěnčík, A.; Chen, X.; Tejos, R.; Skůpa, Petr; Pollmann, S.; Mravec, J.; Petrášek, Jan; Zažímalová, Eva; Honys, David; Rolčík, J.; Murphy, A.; Orellana, A.; Geisler, M.; Friml, J.

    2012-01-01

    Roč. 3, č. 941 (2012) ISSN 2041-1723 R&D Projects: GA MŠk(CZ) LC06034; GA ČR GA522/09/0858 Institutional research plan: CEZ:AV0Z50380511 Keywords : PLANT DEVELOPMENT * ENDOPLASMIC RETICULUM * POLLEN GERMINATION Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 10.015, year: 2012

  10. In-silico identification and phylogenetic analysis of auxin efflux ...

    African Journals Online (AJOL)

    The phytohormone auxin is crucial for plant growth and development. ... genome, which are similar in number with that of monocotyledonous plant Oryza sativa. ... are much closer to Sorghum bicolor and O. sativa PIN genes of the grass family.

  11. Plant development, auxin, and the subsystem incompleteness theorem.

    Science.gov (United States)

    Niklas, Karl J; Kutschera, Ulrich

    2012-01-01

    Plant morphogenesis (the process whereby form develops) requires signal cross-talking among all levels of organization to coordinate the operation of metabolic and genomic subsystems operating in a larger network of subsystems. Each subsystem can be rendered as a logic circuit supervising the operation of one or more signal-activated system. This approach simplifies complex morphogenetic phenomena and allows for their aggregation into diagrams of progressively larger networks. This technique is illustrated here by rendering two logic circuits and signal-activated subsystems, one for auxin (IAA) polar/lateral intercellular transport and another for IAA-mediated cell wall loosening. For each of these phenomena, a circuit/subsystem diagram highlights missing components (either in the logic circuit or in the subsystem it supervises) that must be identified experimentally if each of these basic plant phenomena is to be fully understood. We also illustrate the "subsystem incompleteness theorem," which states that no subsystem is operationally self-sufficient. Indeed, a whole-organism perspective is required to understand even the most simple morphogenetic process, because, when isolated, every biological signal-activated subsystem is morphogenetically ineffective.

  12. An Arabidopsis kinase cascade influences auxin-responsive cell expansion.

    Science.gov (United States)

    Enders, Tara A; Frick, Elizabeth M; Strader, Lucia C

    2017-10-01

    Mitogen-activated protein kinase (MPK) cascades are conserved mechanisms of signal transduction across eukaryotes. Despite the importance of MPK proteins in signaling events, specific roles for many Arabidopsis MPK proteins remain unknown. Multiple studies have suggested roles for MPK signaling in a variety of auxin-related processes. To identify MPK proteins with roles in auxin response, we screened mpk insertional alleles and identified mpk1-1 as a mutant that displays hypersensitivity in auxin-responsive cell expansion assays. Further, mutants defective in the upstream MAP kinase kinase MKK3 also display hypersensitivity in auxin-responsive cell expansion assays, suggesting that this MPK cascade affects auxin-influenced cell expansion. We found that MPK1 interacts with and phosphorylates ROP BINDING PROTEIN KINASE 1 (RBK1), a protein kinase that interacts with members of the Rho-like GTPases from Plants (ROP) small GTPase family. Similar to mpk1-1 and mkk3-1 mutants, rbk1 insertional mutants display auxin hypersensitivity, consistent with a possible role for RBK1 downstream of MPK1 in influencing auxin-responsive cell expansion. We found that RBK1 directly phosphorylates ROP4 and ROP6, supporting the possibility that RBK1 effects on auxin-responsive cell expansion are mediated through phosphorylation-dependent modulation of ROP activity. Our data suggest a MKK3 • MPK1 • RBK1 phosphorylation cascade that may provide a dynamic module for altering cell expansion. © 2017 The Authors The Plant Journal © 2017 John Wiley & Sons Ltd.

  13. Increased expression of the yeast multidrug resistance ABC transporter Pdr18 leads to increased ethanol tolerance and ethanol production in high gravity alcoholic fermentation

    Directory of Open Access Journals (Sweden)

    Teixeira Miguel C

    2012-07-01

    Full Text Available Abstract Background The understanding of the molecular basis of yeast tolerance to ethanol may guide the design of rational strategies to increase process performance in industrial alcoholic fermentations. A set of 21 genes encoding multidrug transporters from the ATP-Binding Cassette (ABC Superfamily and Major Facilitator Superfamily (MFS in S. cerevisiae were scrutinized for a role in ethanol stress resistance. Results A yeast multidrug resistance ABC transporter encoded by the PDR18 gene, proposed to play a role in the incorporation of ergosterol in the yeast plasma membrane, was found to confer resistance to growth inhibitory concentrations of ethanol. PDR18 expression was seen to contribute to decreased 3 H-ethanol intracellular concentrations and decreased plasma membrane permeabilization of yeast cells challenged with inhibitory ethanol concentrations. Given the increased tolerance to ethanol of cells expressing PDR18, the final concentration of ethanol produced during high gravity alcoholic fermentation by yeast cells devoid of PDR18 was lower than the final ethanol concentration produced by the corresponding parental strain. Moreover, an engineered yeast strain in which the PDR18 promoter was replaced in the genome by the stronger PDR5 promoter, leading to increased PDR18 mRNA levels during alcoholic fermentation, was able to attain a 6 % higher ethanol concentration and a 17 % higher ethanol production yield than the parental strain. The improved fermentative performance of yeast cells over-expressing PDR18 was found to correlate with their increased ethanol tolerance and ability to restrain plasma membrane permeabilization induced throughout high gravity fermentation. Conclusions PDR18 gene over-expression increases yeast ethanol tolerance and fermentation performance leading to the production of highly inhibitory concentrations of ethanol. PDR18 overexpression in industrial yeast strains appears to be a promising approach to

  14. Characterization of contaminant transport by gravity, capilliarity and barometric pumping in heterogeneous vadose regimes. 1997 annual progress report

    International Nuclear Information System (INIS)

    Carrigan, C.R.

    1997-01-01

    'Vadose regimes can be the sites of complex interactions between the atmosphere and groundwater. When a volatile contaminant exists as free product or in dissolved form in the vadose environment, upward transport can occur with the contaminant ultimately being vented as a vapor into the atmosphere. This transport happens naturally and can be enhanced by anisotropy resulting from heterogenities in the vadose regime. Several stages in the transport process are involved in going from a volatile, liquid state contaminant to a contaminant vapor vented at the surface. In a three-year effort, called the Vadose Zone Transport Study, the authors are investigating, with the aid of existing data, new field studies involving dissolved tracer gases and 3-D diagnostic computer simulations that provide a framework to interpret the observations, the detailed nature of each of these stages of transport in several different kinds of vadose regimes. They are emphasizing the impact of features specific to a site, that is, the local geology and hydrology, on each stage of the transport process. In particular they want to better understand how the time scales for (1) partitioning contaminants from the liquid to the vapor states and then (2) transporting the vapor out of the vadose regime are dependent on the specific character of a site. Such time-scale information will be important for evaluating the potential of contaminant sources as well as remediation strategies including natural remediation approaches.'

  15. Auxin regulation of cytokinin biosynthesis in Arabidopsis thaliana: A factor of potential importance for auxin-cytokinin-regulated development

    Czech Academy of Sciences Publication Activity Database

    Nordström, A.; Tarkowski, Petr; Tarkowská, Danuše; Norbaek, R.; Astot, C.; Doležal, Karel; Sandberg, G.

    2004-01-01

    Roč. 101, č. 21 (2004), s. 8039-8044 ISSN 0027-8424 Institutional research plan: CEZ:AV0Z5038910 Keywords : Arabidopsis * auxin * cytokinin * biosynthesis Subject RIV: EF - Botanics Impact factor: 10.452, year: 2004

  16. Nonlocal gravity

    CERN Document Server

    Mashhoon, Bahram

    2017-01-01

    Relativity theory is based on a postulate of locality, which means that the past history of the observer is not directly taken into account. This book argues that the past history should be taken into account. In this way, nonlocality---in the sense of history dependence---is introduced into relativity theory. The deep connection between inertia and gravitation suggests that gravity could be nonlocal, and in nonlocal gravity the fading gravitational memory of past events must then be taken into account. Along this line of thought, a classical nonlocal generalization of Einstein's theory of gravitation has recently been developed. A significant consequence of this theory is that the nonlocal aspect of gravity appears to simulate dark matter. According to nonlocal gravity theory, what astronomers attribute to dark matter should instead be due to the nonlocality of gravitation. Nonlocality dominates on the scale of galaxies and beyond. Memory fades with time; therefore, the nonlocal aspect of gravity becomes wea...

  17. Massive gravity from bimetric gravity

    International Nuclear Information System (INIS)

    Baccetti, Valentina; Martín-Moruno, Prado; Visser, Matt

    2013-01-01

    We discuss the subtle relationship between massive gravity and bimetric gravity, focusing particularly on the manner in which massive gravity may be viewed as a suitable limit of bimetric gravity. The limiting procedure is more delicate than currently appreciated. Specifically, this limiting procedure should not unnecessarily constrain the background metric, which must be externally specified by the theory of massive gravity itself. The fact that in bimetric theories one always has two sets of metric equations of motion continues to have an effect even in the massive gravity limit, leading to additional constraints besides the one set of equations of motion naively expected. Thus, since solutions of bimetric gravity in the limit of vanishing kinetic term are also solutions of massive gravity, but the contrary statement is not necessarily true, there is no complete continuity in the parameter space of the theory. In particular, we study the massive cosmological solutions which are continuous in the parameter space, showing that many interesting cosmologies belong to this class. (paper)

  18. Gravity-dependent differentiation and root coils in Arabidopsis thaliana wild type and phospholipase-A-I knockdown mutant grown on the International Space Station.

    Science.gov (United States)

    Scherer, G F E; Pietrzyk, P

    2014-01-01

    Arabidopsis roots on 45° tilted agar in 1-g grow in wave-like figures. In addition to waves, formation of root coils is observed in several mutants compromised in gravitropism and/or auxin transport. The knockdown mutant ppla-I-1 of patatin-related phospholipase-A-I is delayed in root gravitropism and forms increased numbers of root coils. Three known factors contribute to waving: circumnutation, gravisensing and negative thigmotropism. In microgravity, deprivation of wild type (WT) and mutant roots of gravisensing and thigmotropism and circumnutation (known to slow down in microgravity, and could potentially lead to fewer waves or increased coiling in both WT and mutant). To resolve this, mutant ppla-I-1 and WT were grown in the BIOLAB facility in the International Space Station. In 1-g, roots of both types only showed waving. In the first experiment in microgravity, the mutant after 9 days formed far more coils than in 1-g but the WT also formed several coils. After 24 days in microgravity, in both types the coils were numerous with slightly more in the mutant. In the second experiment, after 9 days in microgravity only the mutant formed coils and the WT grew arcuated roots. Cell file rotation (CFR) on the mutant root surface in microgravity decreased in comparison to WT, and thus was not important for coiling. Several additional developmental responses (hypocotyl elongation, lateral root formation, cotyledon expansion) were found to be gravity-influenced. We tentatively discuss these in the context of disturbances in auxin transport, which are known to decrease through lack of gravity. © 2013 German Botanical Society and The Royal Botanical Society of the Netherlands.

  19. Arabidopsis thaliana plants lacking the ARP2/3 complex show defects in cell wall assembly and auxin distribution.

    Science.gov (United States)

    Pratap Sahi, Vaidurya; Cifrová, Petra; García-González, Judith; Kotannal Baby, Innu; Mouillé, Gregory; Gineau, Emilie; Müller, Karel; Baluška, František; Soukup, Aleš; Petrášek, Jan; Schwarzerová, Katerina

    2017-12-25

    The cytoskeleton plays an important role in the synthesis of plant cell walls. Both microtubules and actin cytoskeleton are known to be involved in the morphogenesis of plant cells through their role in cell wall building. The role of ARP2/3-nucleated actin cytoskeleton in the morphogenesis of cotyledon pavement cells has been described before. Seedlings of Arabidopsis mutants lacking a functional ARP2/3 complex display specific cell wall-associated defects. In three independent Arabidopsis mutant lines lacking subunits of the ARP2/3 complex, phenotypes associated with the loss of the complex were analysed throughout plant development. Organ size and anatomy, cell wall composition, and auxin distribution were investigated. ARP2/3-related phenotype is associated with changes in cell wall composition, and the phenotype is manifested especially in mature tissues. Cell walls of mature plants contain less cellulose and a higher amount of homogalacturonan, and display changes in cell wall lignification. Vascular bundles of mutant inflorescence stems show a changed pattern of AUX1-YFP expression. Plants lacking a functional ARP2/3 complex have decreased basipetal auxin transport. The results suggest that the ARP2/3 complex has a morphogenetic function related to cell wall synthesis and auxin transport. © The Author(s) 2017. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  20. The Role of Auxin in Cell Wall Expansion.

    Science.gov (United States)

    Majda, Mateusz; Robert, Stéphanie

    2018-03-22

    Plant cells are surrounded by cell walls, which are dynamic structures displaying a strictly regulated balance between rigidity and flexibility. Walls are fairly rigid to provide support and protection, but also extensible, to allow cell growth, which is triggered by a high intracellular turgor pressure. Wall properties regulate the differential growth of the cell, resulting in a diversity of cell sizes and shapes. The plant hormone auxin is well known to stimulate cell elongation via increasing wall extensibility. Auxin participates in the regulation of cell wall properties by inducing wall loosening. Here, we review what is known on cell wall property regulation by auxin. We focus particularly on the auxin role during cell expansion linked directly to cell wall modifications. We also analyze downstream targets of transcriptional auxin signaling, which are related to the cell wall and could be linked to acid growth and the action of wall-loosening proteins. All together, this update elucidates the connection between hormonal signaling and cell wall synthesis and deposition.

  1. 14 CFR 29.27 - Center of gravity limits.

    Science.gov (United States)

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Center of gravity limits. 29.27 Section 29... AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Flight General § 29.27 Center of gravity limits. The extreme forward and aft centers of gravity and, where critical, the extreme lateral centers of gravity...

  2. Gravity brake

    Science.gov (United States)

    Lujan, Richard E.

    2001-01-01

    A mechanical gravity brake that prevents hoisted loads within a shaft from free-falling when a loss of hoisting force occurs. A loss of hoist lifting force may occur in a number of situations, for example if a hoist cable were to break, the brakes were to fail on a winch, or the hoist mechanism itself were to fail. Under normal hoisting conditions, the gravity brake of the invention is subject to an upward lifting force from the hoist and a downward pulling force from a suspended load. If the lifting force should suddenly cease, the loss of differential forces on the gravity brake in free-fall is translated to extend a set of brakes against the walls of the shaft to stop the free fall descent of the gravity brake and attached load.

  3. Analogue Gravity

    Directory of Open Access Journals (Sweden)

    Barceló Carlos

    2005-12-01

    Full Text Available Analogue models of (and for gravity have a long and distinguished history dating back to the earliest years of general relativity. In this review article we will discuss the history, aims, results, and future prospects for the various analogue models. We start the discussion by presenting a particularly simple example of an analogue model, before exploring the rich history and complex tapestry of models discussed in the literature. The last decade in particular has seen a remarkable and sustained development of analogue gravity ideas, leading to some hundreds of published articles, a workshop, two books, and this review article. Future prospects for the analogue gravity programme also look promising, both on the experimental front (where technology is rapidly advancing and on the theoretical front (where variants of analogue models can be used as a springboard for radical attacks on the problem of quantum gravity.

  4. Inhibitors of plant hormone transport

    Czech Academy of Sciences Publication Activity Database

    Klíma, Petr; Laňková, Martina; Zažímalová, Eva

    2016-01-01

    Roč. 253, č. 6 (2016), s. 1391-1404 ISSN 0033-183X R&D Projects: GA MŠk(CZ) LD15088 Institutional support: RVO:61389030 Keywords : polar auxin transport * acid-binding protein * gnom arf-gef * equilibrative nucleoside transporter * efflux carrier polarity * plasma-membrane-protein * cultured tobacco cells * arabidopsis-thaliana * gravitropic response * brefeldin-a * Plant hormones * Transport * Inhibitors * Auxin * Cytokinins * Strigolactones * Abscisic acid * Cell biology Subject RIV: ED - Physiology Impact factor: 2.870, year: 2016

  5. Cytokinin response factors regulate PIN-FORMED auxin transporters

    Czech Academy of Sciences Publication Activity Database

    Šimášková, M.; O'Brien, J.A.; Khan, M.; Van Noorden, G.; Ötvös, K.; Vieten, A.; De Clercq, E.; Van Haperen, J.M.A.; Cuesta, C.; Hoyerová, Klára; Vanneste, S.; Marhavý, P.; Wabnik, K.; Van Breusegem, F.; Nowack, M.; Murphy, A.; Friml, J.; Weijers, D.; Beeckman, T.; Benková, E.

    2015-01-01

    Roč. 6, NOV (2015), s. 8717 ISSN 2041-1723 Institutional support: RVO:61389030 Keywords : ARABIDOPSIS -THALIANA * ROOT-MERISTEM * TRANSCRIPTION FACTORS Subject RIV: ED - Physiology Impact factor: 11.329, year: 2015

  6. Auxin transport inhibitor induced low complexity petiolated leaves ...

    Indian Academy of Sciences (India)

    2013-04-15

    Apr 15, 2013 ... 2SKA Institution for Research, Education and Development (SKAIRED), 4/11 Sarv Priya Vihar, ... ing plants (angiosperms), born orderly on their stem nodes. ..... First-strand cDNAs were generated by using the oligo.

  7. Quantum Gravity

    OpenAIRE

    Alvarez, Enrique

    2004-01-01

    Gravitons should have momentum just as photons do; and since graviton momentum would cause compression rather than elongation of spacetime outside of matter; it does not appear that gravitons are compatible with Swartzchild's spacetime curvature. Also, since energy is proportional to mass, and mass is proportional to gravity; the energy of matter is proportional to gravity. The energy of matter could thus contract space within matter; and because of the inter-connectedness of space, cause the...

  8. Effects of auxins and cytokinins on tomato callus from anthers

    Directory of Open Access Journals (Sweden)

    Janina H. Rogozińska

    2015-01-01

    Full Text Available An investigation was carried out on growth substance requirements of tomato callus derived from anthers for culture in vitro. Linsmaier and Skoog (1965 medium was used with various levels of auxins (IAA and NAA and cytokinins (K and BAP. The results show that cytokinin is an absolute requirement for callus growth irrespective of the auxin level. The optimum concentration of auxin in combination with cytokinin was found to be 5 μM of NAA or 25 μM of IAA, with 5 μM of K or BAP. Callus growth on media with NAA and cytokinin was superior to that on IAA, amounting to 6.05 g per piece on medium with 5 μM of NAA and BAP. Tissues grown on this medium have the highest water content. At the onset of culture the tissue is characterized by weak growth and attains its maximal increase in fresh weight after 6 weeks.

  9. Auxin Response Factors (ARFs are potential mediators of auxin action in tomato response to biotic and abiotic stress (Solanum lycopersicum.

    Directory of Open Access Journals (Sweden)

    Sarah Bouzroud

    Full Text Available Survival biomass production and crop yield are heavily constrained by a wide range of environmental stresses. Several phytohormones among which abscisic acid (ABA, ethylene and salicylic acid (SA are known to mediate plant responses to these stresses. By contrast, the role of the plant hormone auxin in stress responses remains so far poorly studied. Auxin controls many aspects of plant growth and development, and Auxin Response Factors play a key role in the transcriptional activation or repression of auxin-responsive genes through direct binding to their promoters. As a mean to gain more insight on auxin involvement in a set of biotic and abiotic stress responses in tomato, the present study uncovers the expression pattern of SlARF genes in tomato plants subjected to biotic and abiotic stresses. In silico mining of the RNAseq data available through the public TomExpress web platform, identified several SlARFs as responsive to various pathogen infections induced by bacteria and viruses. Accordingly, sequence analysis revealed that 5' regulatory regions of these SlARFs are enriched in biotic and abiotic stress-responsive cis-elements. Moreover, quantitative qPCR expression analysis revealed that many SlARFs were differentially expressed in tomato leaves and roots under salt, drought and flooding stress conditions. Further pointing to the putative role of SlARFs in stress responses, quantitative qPCR expression studies identified some miRNA precursors as potentially involved in the regulation of their SlARF target genes in roots exposed to salt and drought stresses. These data suggest an active regulation of SlARFs at the post-transcriptional level under stress conditions. Based on the substantial change in the transcript accumulation of several SlARF genes, the data presented in this work strongly support the involvement of auxin in stress responses thus enabling to identify a set of candidate SlARFs as potential mediators of biotic and abiotic

  10. Analogue Gravity

    Directory of Open Access Journals (Sweden)

    Carlos Barceló

    2011-05-01

    Full Text Available Analogue gravity is a research programme which investigates analogues of general relativistic gravitational fields within other physical systems, typically but not exclusively condensed matter systems, with the aim of gaining new insights into their corresponding problems. Analogue models of (and for gravity have a long and distinguished history dating back to the earliest years of general relativity. In this review article we will discuss the history, aims, results, and future prospects for the various analogue models. We start the discussion by presenting a particularly simple example of an analogue model, before exploring the rich history and complex tapestry of models discussed in the literature. The last decade in particular has seen a remarkable and sustained development of analogue gravity ideas, leading to some hundreds of published articles, a workshop, two books, and this review article. Future prospects for the analogue gravity programme also look promising, both on the experimental front (where technology is rapidly advancing and on the theoretical front (where variants of analogue models can be used as a springboard for radical attacks on the problem of quantum gravity.

  11. Scattering of internal gravity waves

    OpenAIRE

    Leaman Nye, Abigail

    2011-01-01

    Internal gravity waves play a fundamental role in the dynamics of stably stratified regions of the atmosphere and ocean. In addition to the radiation of momentum and energy remote from generation sites, internal waves drive vertical transport of heat and mass through the ocean by wave breaking and the mixing subsequently produced. Identifying regions where internal gravity waves contribute to ocean mixing and quantifying this mixing are therefore important for accurate climate ...

  12. Comprehensive RNA-Seq Analysis on the Regulation of Tomato Ripening by Exogenous Auxin.

    Directory of Open Access Journals (Sweden)

    Jiayin Li

    Full Text Available Auxin has been shown to modulate the fruit ripening process. However, the molecular mechanisms underlying auxin regulation of fruit ripening are still not clear. Illumina RNA sequencing was performed on mature green cherry tomato fruit 1 and 7 days after auxin treatment, with untreated fruit as a control. The results showed that exogenous auxin maintained system 1 ethylene synthesis and delayed the onset of system 2 ethylene synthesis and the ripening process. At the molecular level, genes associated with stress resistance were significantly up-regulated, but genes related to carotenoid metabolism, cell degradation and energy metabolism were strongly down-regulated by exogenous auxin. Furthermore, genes encoding DNA demethylases were inhibited by auxin, whereas genes encoding cytosine-5 DNA methyltransferases were induced, which contributed to the maintenance of high methylation levels in the nucleus and thus inhibited the ripening process. Additionally, exogenous auxin altered the expression patterns of ethylene and auxin signaling-related genes that were induced or repressed in the normal ripening process, suggesting significant crosstalk between these two hormones during tomato ripening. The present work is the first comprehensive transcriptome analysis of auxin-treated tomato fruit during ripening. Our results provide comprehensive insights into the effects of auxin on the tomato ripening process and the mechanism of crosstalk between auxin and ethylene.

  13. Enhanced Conjugation of Auxin by GH3 Enzymes Leads to Poor Adventitious Rooting in Carnation Stem Cuttings

    Directory of Open Access Journals (Sweden)

    Antonio Cano

    2018-04-01

    Full Text Available Commercial carnation (Dianthus caryophyllus cultivars are vegetatively propagated from axillary stem cuttings through adventitious rooting; a process which is affected by complex interactions between nutrient and hormone levels and is strongly genotype-dependent. To deepen our understanding of the regulatory events controlling this process, we performed a comparative study of adventitious root (AR formation in two carnation cultivars with contrasting rooting performance, “2101–02 MFR” and “2003 R 8”, as well as in the reference cultivar “Master”. We provided molecular evidence that localized auxin response in the stem cutting base was required for efficient adventitious rooting in this species, which was dynamically established by polar auxin transport from the leaves. In turn, the bad-rooting behavior of the “2003 R 8” cultivar was correlated with enhanced synthesis of indole-3-acetic acid conjugated to aspartic acid by GH3 proteins in the stem cutting base. Treatment of stem cuttings with a competitive inhibitor of GH3 enzyme activity significantly improved rooting of “2003 R 8”. Our results allowed us to propose a working model where endogenous auxin homeostasis regulated by GH3 proteins accounts for the cultivar dependency of AR formation in carnation stem cuttings.

  14. Enhanced Conjugation of Auxin by GH3 Enzymes Leads to Poor Adventitious Rooting in Carnation Stem Cuttings.

    Science.gov (United States)

    Cano, Antonio; Sánchez-García, Ana Belén; Albacete, Alfonso; González-Bayón, Rebeca; Justamante, María Salud; Ibáñez, Sergio; Acosta, Manuel; Pérez-Pérez, José Manuel

    2018-01-01

    Commercial carnation ( Dianthus caryophyllus ) cultivars are vegetatively propagated from axillary stem cuttings through adventitious rooting; a process which is affected by complex interactions between nutrient and hormone levels and is strongly genotype-dependent. To deepen our understanding of the regulatory events controlling this process, we performed a comparative study of adventitious root (AR) formation in two carnation cultivars with contrasting rooting performance, "2101-02 MFR" and "2003 R 8", as well as in the reference cultivar "Master". We provided molecular evidence that localized auxin response in the stem cutting base was required for efficient adventitious rooting in this species, which was dynamically established by polar auxin transport from the leaves. In turn, the bad-rooting behavior of the "2003 R 8" cultivar was correlated with enhanced synthesis of indole-3-acetic acid conjugated to aspartic acid by GH3 proteins in the stem cutting base. Treatment of stem cuttings with a competitive inhibitor of GH3 enzyme activity significantly improved rooting of "2003 R 8". Our results allowed us to propose a working model where endogenous auxin homeostasis regulated by GH3 proteins accounts for the cultivar dependency of AR formation in carnation stem cuttings.

  15. Efficient C1-continuous phase-potential upwind (C1-PPU) schemes for coupled multiphase flow and transport with gravity

    Science.gov (United States)

    Jiang, Jiamin; Younis, Rami M.

    2017-10-01

    In the presence of counter-current flow, nonlinear convergence problems may arise in implicit time-stepping when the popular phase-potential upwinding (PPU) scheme is used. The PPU numerical flux is non-differentiable across the co-current/counter-current flow regimes. This may lead to cycles or divergence in the Newton iterations. Recently proposed methods address improved smoothness of the numerical flux. The objective of this work is to devise and analyze an alternative numerical flux scheme called C1-PPU that, in addition to improving smoothness with respect to saturations and phase potentials, also improves the level of scalar nonlinearity and accuracy. C1-PPU involves a novel use of the flux limiter concept from the context of high-resolution methods, and allows a smooth variation between the co-current/counter-current flow regimes. The scheme is general and applies to fully coupled flow and transport formulations with an arbitrary number of phases. We analyze the consistency property of the C1-PPU scheme, and derive saturation and pressure estimates, which are used to prove the solution existence. Several numerical examples for two- and three-phase flows in heterogeneous and multi-dimensional reservoirs are presented. The proposed scheme is compared to the conventional PPU and the recently proposed Hybrid Upwinding schemes. We investigate three properties of these numerical fluxes: smoothness, nonlinearity, and accuracy. The results indicate that in addition to smoothness, nonlinearity may also be critical for convergence behavior and thus needs to be considered in the design of an efficient numerical flux scheme. Moreover, the numerical examples show that the C1-PPU scheme exhibits superior convergence properties for large time steps compared to the other alternatives.

  16. Quantum Gravity

    International Nuclear Information System (INIS)

    Giribet, G E

    2005-01-01

    Claus Kiefer presents his book, Quantum Gravity, with his hope that '[the] book will convince readers of [the] outstanding problem [of unification and quantum gravity] and encourage them to work on its solution'. With this aim, the author presents a clear exposition of the fundamental concepts of gravity and the steps towards the understanding of its quantum aspects. The main part of the text is dedicated to the analysis of standard topics in the formulation of general relativity. An analysis of the Hamiltonian formulation of general relativity and the canonical quantization of gravity is performed in detail. Chapters four, five and eight provide a pedagogical introduction to the basic concepts of gravitational physics. In particular, aspects such as the quantization of constrained systems, the role played by the quadratic constraint, the ADM decomposition, the Wheeler-de Witt equation and the problem of time are treated in an expert and concise way. Moreover, other specific topics, such as the minisuperspace approach and the feasibility of defining extrinsic times for certain models, are discussed as well. The ninth chapter of the book is dedicated to the quantum gravitational aspects of string theory. Here, a minimalistic but clear introduction to string theory is presented, and this is actually done with emphasis on gravity. It is worth mentioning that no hard (nor explicit) computations are presented, even though the exposition covers the main features of the topic. For instance, black hole statistical physics (within the framework of string theory) is developed in a pedagogical and concise way by means of heuristical arguments. As the author asserts in the epilogue, the hope of the book is to give 'some impressions from progress' made in the study of quantum gravity since its beginning, i.e., since the end of 1920s. In my opinion, Kiefer's book does actually achieve this goal and gives an extensive review of the subject. (book review)

  17. ARG1 (altered response to gravity) encodes a DnaJ-like protein that potentially interacts with the cytoskeleton

    Science.gov (United States)

    Sedbrook, J. C.; Chen, R.; Masson, P. H.

    1999-01-01

    Gravitropism allows plant organs to direct their growth at a specific angle from the gravity vector, promoting upward growth for shoots and downward growth for roots. Little is known about the mechanisms underlying gravitropic signal transduction. We found that mutations in the ARG1 locus of Arabidopsis thaliana alter root and hypocotyl gravitropism without affecting phototropism, root growth responses to phytohormones or inhibitors of auxin transport, or starch accumulation. The positional cloning of ARG1 revealed a DnaJ-like protein containing a coiled-coil region homologous to coiled coils found in cytoskeleton-interacting proteins. These data suggest that ARG1 participates in a gravity-signaling process involving the cytoskeleton. A combination of Northern blot studies and analysis of ARG1-GUS fusion-reporter expression in transgenic plants demonstrated that ARG1 is expressed in all organs. Ubiquitous ARG1 expression in Arabidopsis and the identification of an ortholog in Caenorhabditis elegans suggest that ARG1 is involved in other essential processes.

  18. Auxin and ABA act as central regulators of developmental networks associated with paradormancy in Canada thistle (Cirsium arvense)

    KAUST Repository

    Anderson, James V.

    2012-05-13

    Abstract Dormancy in underground vegetative buds of Canada thistle, an herbaceous perennial weed, allows escape from current control methods and contributes to its invasive nature. In this study, ∼65 % of root sections obtained from greenhouse propagated Canada thistle produced new vegetative shoots by 14 days post-sectioning. RNA samples obtained from sectioned roots incubated 0, 24, 48, and 72 h at 25°C under 16:8 h light-dark conditions were used to construct four MID-tagged cDNA libraries. Analysis of in silico data obtained using Roche 454 GS-FLX pyrosequencing technologies identified molecular networks associated with paradormancy release in underground vegetative buds of Canada thistle. Sequencing of two replicate plates produced ∼2.5 million ESTs with an average read length of 362 bases. These ESTs assembled into 67358 unique sequences (21777 contigs and 45581 singlets) and annotation against the Arabidopsis database identified 15232 unigenes. Among the 15232 unigenes, we identified processes enriched with transcripts involved in plant hormone signaling networks. To follow-up on these results, we examined hormone profiles in roots, which identified changes in abscisic acid (ABA) and ABA metabolites, auxins, and cytokinins post-sectioning. Transcriptome and hormone profiling data suggest that interaction between auxin- and ABA-signaling regulate paradormancy maintenance and release in underground adventitious buds of Canada thistle. Our proposed model shows that sectioning-induced changes in polar auxin transport alters ABA metabolism and signaling, which further impacts gibberellic acid signaling involving interactions between ABA and FUSCA3. Here we report that reduced auxin and ABA-signaling, in conjunction with increased cytokinin biosynthesis post-sectioning supports a model where interactions among hormones drives molecular networks leading to cell division, differentiation, and vegetative outgrowth. ©Springer-Verlag (outside the USA) 2012.

  19. Exogenous auxin represses soybean seed germination through decreasing the gibberellin/abscisic acid (GA/ABA) ratio

    OpenAIRE

    Shuai, Haiwei; Meng, Yongjie; Luo, Xiaofeng; Chen, Feng; Zhou, Wenguan; Dai, Yujia; Qi, Ying; Du, Junbo; Yang, Feng; Liu, Jiang; Yang, Wenyu; Shu, Kai

    2017-01-01

    Auxin is an important phytohormone which mediates diverse development processes in plants. Published research has demonstrated that auxin induces seed dormancy. However, the precise mechanisms underlying the effect of auxin on seed germination need further investigation, especially the relationship between auxins and both abscisic acid (ABA) and gibberellins (GAs), the latter two phytohormones being the key regulators of seed germination. Here we report that exogenous auxin treatment represse...

  20. In-silico identification and phylogenetic analysis of auxin efflux ...

    African Journals Online (AJOL)

    ufuoma

    2014-01-08

    Jan 8, 2014 ... PIN proteins of Arabidopsis viz., PIN1,PIN4 and PIN7 show plasma membrane .... The central hydrophilic loop is dynamic in nature and differs from each other in terms ... research of this plant at the molecular level. Auxin efflux.

  1. The role of auxins in somatic embryogenesis of Abies alba

    Czech Academy of Sciences Publication Activity Database

    Vondráková, Zuzana; Eliášová, Kateřina; Fischerová, Lucie; Vágner, Martin

    2011-01-01

    Roč. 6, č. 4 (2011), s. 587-596 ISSN 1895-104X R&D Projects: GA MŠk OC 158 Institutional research plan: CEZ:AV0Z50380511 Keywords : Auxin inhibitor * Fir * Phytohormone Subject RIV: EF - Botanics Impact factor: 1.000, year: 2011

  2. Identification and expression analysis of primary auxin-responsive ...

    Indian Academy of Sciences (India)

    2013-12-09

    Dec 9, 2013 ... Previous research has demonstrated that auxin induces and regulates the .... three main-stem nodes stage seedlings were prepared for the. IAA treatment ... For semi- quantitative RT-PCR analysis, first-strand cDNA was syn-.

  3. Lateral root formation and the multiple roles of auxin

    NARCIS (Netherlands)

    Du, Yujuan; Scheres, Ben

    2018-01-01

    Root systems can display variable architectures that contribute to survival strategies of plants. The model plant Arabidopsis thaliana possesses a tap root system, in which the primary root and lateral roots (LRs) are major architectural determinants. The phytohormone auxin fulfils multiple roles

  4. Effects of auxins on in vitro reserve compounds of Phalaenopsis ...

    African Journals Online (AJOL)

    SAM

    2014-03-26

    Mar 26, 2014 ... division rate, which is related to auxin induction of cell proliferation (Hartig and ..... to support plant respiration and growth through the night, and several projects ... Four basic carbon partitioning strategies may occur in CAM species: ME ... their cellular and temporal expression patterns must be defined.

  5. Why plants need more than one type of auxin

    Czech Academy of Sciences Publication Activity Database

    Simon, Sibu; Petrášek, Jan

    2011-01-01

    Roč. 180, č. 3 (2011), s. 454-460 ISSN 0168-9452 R&D Projects: GA MŠk(CZ) LC06034 Institutional research plan: CEZ:AV0Z50380511 Keywords : Auxin * IAA * 4-Cl-IAA * IBA * PAA Subject RIV: ED - Physiology Impact factor: 2.945, year: 2011

  6. effects of different concentrations of auxins on rooting and root

    African Journals Online (AJOL)

    Preferred Customer

    ABSTRACT: The effect of auxins and their different concentrations on rooting and root ... primary root length and the longest primary root was recorded with the ... ceuticals, lubricants, foods, electrical insulators, .... stem cuttings of jojoba treated with IBA and NAA, .... increasing cell division and enlargement at each.

  7. Simulating Gravity

    Science.gov (United States)

    Pipinos, Savas

    2010-01-01

    This article describes one classroom activity in which the author simulates the Newtonian gravity, and employs the Euclidean Geometry with the use of new technologies (NT). The prerequisites for this activity were some knowledge of the formulae for a particle free fall in Physics and most certainly, a good understanding of the notion of similarity…

  8. Cellular gravity

    NARCIS (Netherlands)

    F.C. Gruau; J.T. Tromp (John)

    1999-01-01

    textabstractWe consider the problem of establishing gravity in cellular automata. In particular, when cellular automata states can be partitioned into empty, particle, and wall types, with the latter enclosing rectangular areas, we desire rules that will make the particles fall down and pile up on

  9. Gravitropism in higher plant shoots. VI. Changing sensitivity to auxin in gravistimulated soybean hypocotyls

    Science.gov (United States)

    Rorabaugh, P. A.; Salisbury, F. B.

    1989-01-01

    Although the Cholodny-Went model of auxin redistribution has been used to explain the transduction phase of gravitropism for over 60 years, problems are apparent, especially with dicot stems. An alternative to an auxin gradient is a physiological gradient in which lower tissues of a horizontal stem become more sensitive than upper tissues to auxin already present. Changes in tissue sensitivity to auxin were tested by immersing marked Glycine max Merrill (soybean) hypocotyl sections in buffered auxin solutions (0, 10(-8) to 10(-2) molar indoleacetic acid) and observing bending and growth of upper and lower surfaces. The two surfaces of horizontal hypocotyl sections responded differently to the same applied auxin stimulus; hypocotyls bent up (lower half grew more) in buffer alone or in low auxin levels, but bent down (upper half grew more) in high auxin. Dose-response curves were evaluated with Michaelis-Menten kinetics, with auxin-receptor binding analogous to enzyme-substrate binding. Vmax for the lower half was usually greater than that for the upper half, which could indicate more binding sites in the lower half. Km of the upper half was always greater than that of the lower half (unmeasurably low), which could indicate that upper-half binding sites had a much lower affinity for auxin than lower-half sites. Dose-response curves were also obtained for sections scrubbed' (cuticle abraded) on top or bottom before immersion in auxin, and gravitropic memory' experiments of L. Brauner and A. Hagar (1958 Planta 51: 115-147) were duplicated. [1-14C]Indoleacetic acid penetration was equal into the two halves, and endogenous plus exogenously supplied (not radiolabeled) free auxin in the two halves (by gas chromatography-selected ion monitoring-mass spectrometry) was also equal. Thus, differential growth occurred without free auxin redistribution, contrary to Cholodny-Went but in agreement with a sensitivity model.

  10. Auxinic herbicides, mechanisms of action, and weed resistance: A look into recent plant science advances

    Directory of Open Access Journals (Sweden)

    Pedro Jacob Christoffoleti

    2015-08-01

    Full Text Available Auxin governs dynamic cellular processes involved at several stages of plant growth and development. In this review, we discuss the mechanisms employed by auxin in light of recent scientific advances, with a focus on synthetic auxins as herbicides and synthetic auxin resistance mechanisms. Two auxin receptors were reported. The plasma membrane receptor ABP1 (Auxin Binding Protein 1 alters the structure and arrangement of actin filaments and microtubules, leading to plant epinasty and reducing peroxisomes and mitochondria mobility in the cell environment. The second auxin receptor is the gene transcription pathway regulated by the SCFTir/AFB ubiquitination complex, which destroys transcription repressor proteins that interrupt Auxin Response Factor (ARF activation. As a result mRNA related with Abscisic Acid (ABA and ethylene are transcribed, producing high quantities of theses hormones. Their associated action leads to high production of Reactive Oxygen Species (ROS, leading to tissue and plant death. Recently, another ubiquitination pathway which is described as a new auxin signaling route is the F-box protein S-Phase Kinase-Associated Protein 2A (SKP2A. It is active in cell division regulation and there is evidence that auxin herbicides can deregulate the SKP2A pathway, which leads to severe defects in plant development. In this discussion, we propose that SFCSKP2A auxin binding site alteration could be a new auxinic herbicide resistance mechanism, a concept which may contribute to the current progress in plant biology in its quest to clarify the many questions that still surround auxin herbicide mechanisms of action and the mechanisms of weed resistance.

  11. Role of chloride ions in the promotion of auxin-induced growth of maize coleoptile segments.

    Science.gov (United States)

    Burdach, Zbigniew; Kurtyka, Renata; Siemieniuk, Agnieszka; Karcz, Waldemar

    2014-10-01

    The mechanism of auxin action on ion transport in growing cells has not been determined in detail. In particular, little is known about the role of chloride in the auxin-induced growth of coleoptile cells. Moreover, the data that do exist in the literature are controversial. This study describes experiments that were carried out with maize (Zea mays) coleoptile segments, this being a classical model system for studies of plant cell elongation growth. Growth kinetics or growth and pH changes were recorded in maize coleoptiles using two independent measuring systems. The growth rate of the segments was measured simultaneously with medium pH changes. Membrane potential changes in parenchymal cells of the segments were also determined for chosen variants. The question of whether anion transport is involved in auxin-induced growth of maize coleoptile segments was primarily studied using anion channel blockers [anthracene-9-carboxylic acid (A-9-C) and 4,4'-diisothiocyanatostilbene-2,2'-disulphonic acid (DIDS)]. In addition, experiments in which KCl was replaced by KNO3 were also performed. Both anion channel blockers, added at 0·1 mm, diminished indole-3-acetic acid (IAA)-induced elongation growth by ~30 %. Medium pH changes measured simultaneously with growth indicated that while DIDS stopped IAA-induced proton extrusion, A-9-C diminished it by only 50 %. Addition of A-9-C to medium containing 1 mm KCl did not affect the characteristic kinetics of IAA-induced membrane potential changes, while in the presence of 10 mm KCl the channel blocker stopped IAA-induced membrane hyperpolarization. Replacement of KCl with KNO3 significantly decreased IAA-induced growth and inhibited proton extrusion. In contrast to the KCl concentration, the concentration of KNO3 did not affect the growth-stimulatory effect of IAA. For comparison, the effects of the cation channel blocker tetraethylammonium chloride (TEA-Cl) on IAA-induced growth and proton extrusion were also determined. TEA

  12. Quantum gravity

    International Nuclear Information System (INIS)

    Isham, C.

    1989-01-01

    Gravitational effects are seen as arising from a curvature in spacetime. This must be reconciled with gravity's apparently passive role in quantum theory to achieve a satisfactory quantum theory of gravity. The development of grand unified theories has spurred the search, with forces being of equal strength at a unification energy of 10 15 - 10 18 GeV, with the ''Plank length'', Lp ≅ 10 -35 m. Fundamental principles of general relativity and quantum mechanics are outlined. Gravitons are shown to have spin-0, as mediators of gravitation force in the classical sense or spin-2 which are related to the quantisation of general relativity. Applying the ideas of supersymmetry to gravitation implies partners for the graviton, especially the massless spin 3/2 fermion called a gravitino. The concept of supersymmetric strings is introduced and discussed. (U.K.)

  13. Quantum gravity

    International Nuclear Information System (INIS)

    Markov, M.A.; West, P.C.

    1984-01-01

    This book discusses the state of the art of quantum gravity, quantum effects in cosmology, quantum black-hole physics, recent developments in supergravity, and quantum gauge theories. Topics considered include the problems of general relativity, pregeometry, complete cosmological theories, quantum fluctuations in cosmology and galaxy formation, a new inflationary universe scenario, grand unified phase transitions and the early Universe, the generalized second law of thermodynamics, vacuum polarization near black holes, the relativity of vacuum, black hole evaporations and their cosmological consequences, currents in supersymmetric theories, the Kaluza-Klein theories, gauge algebra and quantization, and twistor theory. This volume constitutes the proceedings of the Second Seminar on Quantum Gravity held in Moscow in 1981

  14. Is nonrelativistic gravity possible?

    International Nuclear Information System (INIS)

    Kocharyan, A. A.

    2009-01-01

    We study nonrelativistic gravity using the Hamiltonian formalism. For the dynamics of general relativity (relativistic gravity) the formalism is well known and called the Arnowitt-Deser-Misner (ADM) formalism. We show that if the lapse function is constrained correctly, then nonrelativistic gravity is described by a consistent Hamiltonian system. Surprisingly, nonrelativistic gravity can have solutions identical to relativistic gravity ones. In particular, (anti-)de Sitter black holes of Einstein gravity and IR limit of Horava gravity are locally identical.

  15. Auxin-induced modifications of cell wall polysaccharides in cat coleoptile segments. Effect of galactose

    International Nuclear Information System (INIS)

    Yamamoto, R.; Masuda, Y.

    1984-01-01

    Galactose inhibits auxin-induced cell elongation in oat coleoptile segments. Cell elongation induced by exogenously applied auxin is controlled by factors such as auxin uptake, cell wall loosening, osmotic concentration of sap and hydraulic conductivity. However, galactose does not have any effect on these factors. The results discussed in this paper led to the conclusion that galactose does not affect cell wall loosening which controls rapid growth, but inhibits cell wall synthesis which is required to maintain long-term growth

  16. Do Phytotropins Inhibit Auxin Efflux by Impairing Vesicle Traffic?

    Czech Academy of Sciences Publication Activity Database

    Petrášek, Jan; Černá, A.; Schwarzerová, K.; Elčkner, Miroslav; Morris, David; Zažímalová, Eva

    2003-01-01

    Roč. 131, č. 1 (2003), s. 254-263 ISSN 0032-0889 R&D Projects: GA MŠk LN00A081 Grant - others:EU INCO COPERNICUS(XE) ERBIC15 CT98 0118 Institutional research plan: CEZ:AV0Z5038910 Keywords : 1-N-naphthylphthalamic acid * BY-2 tobacco * auxin efflux Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 5.634, year: 2003

  17. The allelochemical MDCA inhibits lignification and affects auxin homeostasis

    Czech Academy of Sciences Publication Activity Database

    Steenackers, W.; Cesarino, I.; Klíma, Petr; Quareshy, M.; Vanholme, R.; Corneillie, S.; Kumpf, R. P.; Van De Wouwer, D.; Ljung, K.; Goeminne, G.; Novák, Ondřej; Zažímalová, Eva; Napier, R.; Boerjan, W.; Vanholme, B.

    2016-01-01

    Roč. 172, č. 2 (2016), s. 874-888 ISSN 0032-0889 R&D Projects: GA ČR(CZ) GA16-10948S; GA MŠk(CZ) LO1204 Grant - others:OPPK(XE) CZ.2.16/3.1.00/21519 Institutional support: RVO:61389030 Keywords : auxin biosynthesis * lignification * Asparagus officinalis Subject RIV: ED - Physiology Impact factor: 6.456, year: 2016

  18. Computational Modeling of Auxin: A Foundation for Plant Engineering.

    Science.gov (United States)

    Morales-Tapia, Alejandro; Cruz-Ramírez, Alfredo

    2016-01-01

    Since the development of agriculture, humans have relied on the cultivation of plants to satisfy our increasing demand for food, natural products, and other raw materials. As we understand more about plant development, we can better manipulate plants to fulfill our particular needs. Auxins are a class of simple metabolites that coordinate many developmental activities like growth and the appearance of functional structures in plants. Computational modeling of auxin has proven to be an excellent tool in elucidating many mechanisms that underlie these developmental events. Due to the complexity of these mechanisms, current modeling efforts are concerned only with single phenomena focused on narrow spatial and developmental contexts; but a general model of plant development could be assembled by integrating the insights from all of them. In this perspective, we summarize the current collection of auxin-driven computational models, focusing on how they could come together into a single model for plant development. A model of this nature would allow researchers to test hypotheses in silico and yield accurate predictions about the behavior of a plant under a given set of physical and biochemical constraints. It would also provide a solid foundation toward the establishment of plant engineering, a proposed discipline intended to enable the design and production of plants that exhibit an arbitrarily defined set of features.

  19. Investigating a Potential Auxin-Related Mode of Hormetic/Inhibitory Action of the Phytotoxin Parthenin.

    Science.gov (United States)

    Belz, Regina G

    2016-01-01

    Parthenin is a metabolite of Parthenium hysterophorus and is believed to contribute to the weed's invasiveness via allelopathy. Despite the potential of parthenin to suppress competitors, low doses stimulate plant growth. This biphasic action was hypothesized to be auxin-like and, therefore, an auxin-related mode of parthenin action was investigated using two approaches: joint action experiments with Lactuca sativa, and dose-response experiments with auxin/antiauxin-resistant Arabidopsis thaliana genotypes. The joint action approach comprised binary mixtures of subinhibitory doses of the auxin 3-indoleacetic acid (IAA) mixed with parthenin or one of three reference compounds [indole-3-butyric acid (IBA), 2,3,5-triiodobenzoic acid (TIBA), 2-(p-chlorophenoxy)-2-methylpropionic acid (PCIB)]. The reference compounds significantly interacted with IAA at all doses, but parthenin interacted only at low doses indicating that parthenin hormesis may be auxin-related, in contrast to its inhibitory action. The genetic approach investigated the response of four auxin/antiauxin-resistant mutants and a wildtype to parthenin or two reference compounds (IAA, PCIB). The responses of mutant plants to the reference compounds confirmed previous reports, but differed from the responses observed for parthenin. Parthenin stimulated and inhibited all mutants independent of resistance. This provided no indication for an auxin-related action of parthenin. Therefore, the hypothesis of an auxin-related inhibitory action of parthenin was rejected in two independent experimental approaches, while the hypothesis of an auxin-related stimulatory effect could not be rejected.

  20. Noncommutative gravity

    International Nuclear Information System (INIS)

    Schupp, P.

    2007-01-01

    Heuristic arguments suggest that the classical picture of smooth commutative spacetime should be replaced by some kind of quantum / noncommutative geometry at length scales and energies where quantum as well as gravitational effects are important. Motivated by this idea much research has been devoted to the study of quantum field theory on noncommutative spacetimes. More recently the focus has started to shift back to gravity in this context. We give an introductory overview to the formulation of general relativity in a noncommutative spacetime background and discuss the possibility of exact solutions. (author)

  1. 14 CFR 27.1519 - Weight and center of gravity.

    Science.gov (United States)

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Weight and center of gravity. 27.1519 Section 27.1519 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION... Operating Limitations § 27.1519 Weight and center of gravity. The weight and center of gravity limitations...

  2. 14 CFR 25.27 - Center of gravity limits.

    Science.gov (United States)

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Center of gravity limits. 25.27 Section 25... AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES Flight General § 25.27 Center of gravity limits. The extreme forward and the extreme aft center of gravity limitations must be established for each practicably...

  3. 14 CFR 29.1519 - Weight and center of gravity.

    Science.gov (United States)

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Weight and center of gravity. 29.1519 Section 29.1519 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION... Operating Limitations § 29.1519 Weight and center of gravity. The weight and center of gravity limitations...

  4. 14 CFR 23.1519 - Weight and center of gravity.

    Science.gov (United States)

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Weight and center of gravity. 23.1519 Section 23.1519 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION... Limitations and Information § 23.1519 Weight and center of gravity. The weight and center of gravity...

  5. Effects of cations on hormone transport in primary roots of Zea mays

    Science.gov (United States)

    Hasenstein, K. H.; Evans, M. L.

    1988-01-01

    We examined the influence of aluminum and calcium (and certain other cations) on hormone transport in corn roots. When aluminum was applied unilaterally to the caps of 15 mm apical root sections the roots curved strongly away from the aluminum. When aluminum was applied unilaterally to the cap and 3H-indole-3-acetic acid was applied to the basal cut surface twice as much radioactivity (assumed to be IAA) accumulated on the concave side of the curved root as on the convex side. Auxin transport in the apical region of intact roots was preferentially basipetal, with a polarity (basipetal transport divided by acropetal transport) of 6.3. In decapped 5 mm apical root segments, auxin transport was acropetally polar (polarity = 0.63). Application of aluminum to the root cap strongly promoted acropetal transport of auxin reducing polarity from 6.3 to 2.1. Application of calcium to the root cap enhanced basipetal movement of auxin, increasing polarity from 6.3 to 7.6. Application of the calcium chelator, ethylene-glycol-bis-(beta-aminoethylether)-N,N,N',N'-tetraacetic acid, greatly decreased basipetal auxin movement, reducing polarity from 6.3 to 3.7. Transport of label after application of tritiated abscisic acid showed no polarity and was not affected by calcium or aluminum. The results indicate that the root cap is particularly important in maintaining basipetal polarity of auxin transport in primary roots of corn. The induction of root curvature by unilateral application of aluminum or calcium to root caps is likely to result from localized effects of these ions on auxin transport. The findings are discussed relative to the possible role of calcium redistribution in the gravitropic curvature of roots and the possibility of calmodulin involvement in the action of calcium and aluminum on auxin transport.

  6. Conformal Gravity

    International Nuclear Information System (INIS)

    Hooft, G.

    2012-01-01

    The dynamical degree of freedom for the gravitational force is the metric tensor, having 10 locally independent degrees of freedom (of which 4 can be used to fix the coordinate choice). In conformal gravity, we split this field into an overall scalar factor and a nine-component remainder. All unrenormalizable infinities are in this remainder, while the scalar component can be handled like any other scalar field such as the Higgs field. In this formalism, conformal symmetry is spontaneously broken. An imperative demand on any healthy quantum gravity theory is that black holes should be described as quantum systems with micro-states as dictated by the Hawking-Bekenstein theory. This requires conformal symmetry that may be broken spontaneously but not explicitly, and this means that all conformal anomalies must cancel out. Cancellation of conformal anomalies yields constraints on the matter sector as described by some universal field theory. Thus black hole physics may eventually be of help in the construction of unified field theories. (author)

  7. The ARG1-LIKE2 gene of Arabidopsis functions in a gravity signal transduction pathway that is genetically distinct from the PGM pathway

    Science.gov (United States)

    Guan, Changhui; Rosen, Elizabeth S.; Boonsirichai, Kanokporn; Poff, Kenneth L.; Masson, Patrick H.

    2003-01-01

    The arl2 mutants of Arabidopsis display altered root and hypocotyl gravitropism, whereas their inflorescence stems are fully gravitropic. Interestingly, mutant roots respond like the wild type to phytohormones and an inhibitor of polar auxin transport. Also, their cap columella cells accumulate starch similarly to wild-type cells, and mutant hypocotyls display strong phototropic responses to lateral light stimulation. The ARL2 gene encodes a DnaJ-like protein similar to ARG1, another protein previously implicated in gravity signal transduction in Arabidopsis seedlings. ARL2 is expressed at low levels in all organs of seedlings and plants. arl2-1 arg1-2 double mutant roots display kinetics of gravitropism similar to those of single mutants. However, double mutants carrying both arl2-1 and pgm-1 (a mutation in the starch-biosynthetic gene PHOSPHOGLUCOMUTASE) at the homozygous state display a more pronounced root gravitropic defect than the single mutants. On the other hand, seedlings with a null mutation in ARL1, a paralog of ARG1 and ARL2, behave similarly to the wild type in gravitropism and other related assays. Taken together, the results suggest that ARG1 and ARL2 function in the same gravity signal transduction pathway in the hypocotyl and root of Arabidopsis seedlings, distinct from the pathway involving PGM.

  8. Southern Africa Gravity Data

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data base (14,559 records) was received in January 1986. Principal gravity parameters include elevation and observed gravity. The observed gravity values are...

  9. NGS Absolute Gravity Data

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The NGS Absolute Gravity data (78 stations) was received in July 1993. Principal gravity parameters include Gravity Value, Uncertainty, and Vertical Gradient. The...

  10. Auxin-binding pocket of ABP1 is crucial for its gain-of-function cellular and developmental roles

    Czech Academy of Sciences Publication Activity Database

    Grones, P.; Chen, X.; Simon, S.; Kaufmann, W.A.; De Rycke, R.; Nodzyński, T.; Zažímalová, Eva; Friml, J.

    2015-01-01

    Roč. 66, č. 16 (2015), s. 5055-5065 ISSN 0022-0957 Institutional support: RVO:61389030 Keywords : Auxin * ABP1 * Auxin binding Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 5.677, year: 2015

  11. Patterns of auxin and abscisic acid movement in the tips of gravistimulated primary roots of maize

    Science.gov (United States)

    Young, L. M.; Evans, M. L.

    1996-01-01

    Because both abscisic acid (ABA) and auxin (IAA) have been suggested as possible chemical mediators of differential growth during root gravitropism, we compared with redistribution of label from applied 3H-IAA and 3H-ABA during maize root gravitropism and examined the relative basipetal movement of 3H-IAA and 3H-ABA applied to the caps of vertical roots. Lateral movement of 3H-ABA across the tips of vertical roots was non-polar and about 2-fold greater than lateral movement of 3H-IAA (also non-polar). The greater movement of ABA was not due to enhanced uptake since the uptake of 3H-IAA was greater than that of 3H-ABA. Basipetal movement of label from 3H-IAA or 3H-ABA applied to the root cap was determined by measuring radioactivity in successive 1 mm sections behind the tip 90 minutes after application. ABA remained largely in the first mm (point of application) whereas IAA was concentrated in the region 2-4 mm from the tip with substantial levels found 7-8 mm from the tip. Pretreatment with inhibitors of polar auxin transport decreased both gravicurvature and the basipetal movement of IAA. When roots were placed horizontally, the movement of 3H-IAA from top to bottom across the cap was enhanced relative to movement from bottom to top whereas the pattern of movement of label from 3H-ABA was unaffected. These results are consistent with the hypothesis that IAA plays a role in root gravitropism but contrary to the idea that gravi-induced asymmetric distribution of ABA contributes to the response.

  12. A mutation in the Arabidopsis HYL1 gene encoding a dsRNA binding protein affects responses to abscisic acid, auxin, and cytokinin

    Science.gov (United States)

    Lu, C.; Fedoroff, N.

    2000-01-01

    Both physiological and genetic evidence indicate interconnections among plant responses to different hormones. We describe a pleiotropic recessive Arabidopsis transposon insertion mutation, designated hyponastic leaves (hyl1), that alters the plant's responses to several hormones. The mutant is characterized by shorter stature, delayed flowering, leaf hyponasty, reduced fertility, decreased rate of root growth, and an altered root gravitropic response. It also exhibits less sensitivity to auxin and cytokinin and hypersensitivity to abscisic acid (ABA). The auxin transport inhibitor 2,3,5-triiodobenzoic acid normalizes the mutant phenotype somewhat, whereas another auxin transport inhibitor, N-(1-naph-thyl)phthalamic acid, exacerbates the phenotype. The gene, designated HYL1, encodes a 419-amino acid protein that contains two double-stranded RNA (dsRNA) binding motifs, a nuclear localization motif, and a C-terminal repeat structure suggestive of a protein-protein interaction domain. We present evidence that the HYL1 gene is ABA-regulated and encodes a nuclear dsRNA binding protein. We hypothesize that the HYL1 protein is a regulatory protein functioning at the transcriptional or post-transcriptional level.

  13. Expression of a gymnosperm PIN homologous gene correlates with auxin immunolocalization pattern at cotyledon formation and in demarcation of the procambium during Picea abies somatic embryo development and in seedling tissues.

    Science.gov (United States)

    Palovaara, Joakim; Hallberg, Henrik; Stasolla, Claudio; Luit, Bert; Hakman, Inger

    2010-04-01

    In seed plants, the body organization is established during embryogenesis and is uniform across gymnosperms and angiosperms, despite differences during early embryogeny. Evidence from angiosperms implicates the plant hormone auxin and its polar transport, mainly established by the PIN family of auxin efflux transporters, in the patterning of embryos. Here, PaPIN1 from Norway spruce (Picea abies [L.] Karst.), a gene widely expressed in conifer tissues and organs, was characterized and its expression and localization patterns were determined with reverse transcription polymerase chain reaction and in situ hybridization during somatic embryo development and in seedlings. PaPIN1 shares the predicted structure of other PIN proteins, but its central hydrophilic loop is longer than most PINs. In phylogenetic analyses, PaPIN1 clusters with Arabidopsis thaliana (L.) Heynh. PIN3, PIN4 and PIN7, but its expression pattern also suggests similarity to PIN1. The PaPIN1 expression signal was high in the protoderm of pre-cotyledonary embryos, but not if embryos were pre-treated with the auxin transport inhibitor N-1-naphthylphthalamic acid (NPA). This, together with a high auxin immunolocalization signal in this cell layer, suggests a role of PaPIN1 during cotyledon formation. At later stages, high PaPIN1 expression was observed in differentiating procambium, running from the tip of incipient cotyledons down through the embryo axis and to the root apical meristem (RAM), although the mode of RAM specification in conifer embryos differs from that of most angiosperms. Also, the PaPIN1 in situ signal was high in seedling root tips including root cap columella cells. The results thus suggest that PaPIN1 provides an ancient function associated with auxin transport and embryo pattern formation prior to the separation of angiosperms and gymnosperms, in spite of some morphological differences.

  14. Newtonian gravity in loop quantum gravity

    OpenAIRE

    Smolin, Lee

    2010-01-01

    We apply a recent argument of Verlinde to loop quantum gravity, to conclude that Newton's law of gravity emerges in an appropriate limit and setting. This is possible because the relationship between area and entropy is realized in loop quantum gravity when boundaries are imposed on a quantum spacetime.

  15. Isolation and characterization of an auxin-inducible glutathione S-transferase gene of Arabidopsis thaliana

    NARCIS (Netherlands)

    Kop, D.A.M. van der; Schuyer, M.; Scheres, B.J.G.; Zaal, B.J. van der; Hooykaas, P.J.J.

    1996-01-01

    Genes homologous to the auxin-inducible Nt103 glutathione S-transferase (GST) gene of tobacco, were isolated from a genomic library of Arabidopsis thaliana. We isolated a λ clone containing an auxin-inducible gene, At103-1a, and part of a constitutively expressed gene, At103-1b. The coding regions

  16. A noncanonical auxin-sensing mechanism is required for organ morphogenesis in arabidopsis

    NARCIS (Netherlands)

    Simonini, Sara; Deb, Joyita; Moubayidin, Laila; Stephenson, Pauline; Valluru, Manoj; Freire-Rios, Alejandra; Sorefan, Karim; Weijers, Dolf; Friml, Jiří; Østergaard, Lars

    2016-01-01

    Tissue patterning in multicellular organisms is the output of precise spatio–temporal regulation of gene expression coupled with changes in hormone dynamics. In plants, the hormone auxin regulates growth and development at every stage of a plant’s life cycle. Auxin signaling occurs through

  17. Single-cell-based system to monitor carrier driven cellular auxin homeostasis

    Czech Academy of Sciences Publication Activity Database

    Barbez, E.; Laňková, Martina; Pařezová, Markéta; Maizel, A.; Zažímalová, Eva; Petrášek, Jan; Friml, J.; Kleine-Vehn, J.

    2013-01-01

    Roč. 13, FEB 4 (2013) ISSN 1471-2229 R&D Projects: GA ČR(CZ) GAP305/11/0797; GA ČR(CZ) GAP305/11/2476 Institutional research plan: CEZ:AV0Z50380511 Keywords : Auxin homeostasis * DR5 * Auxin carrier Subject RIV: ED - Physiology Impact factor: 3.942, year: 2013

  18. A complex molecular interplay of auxin and ethylene signaling pathways is involved in Arabidopsis growth promotion by Burkholderia phytofirmans PsJN

    Directory of Open Access Journals (Sweden)

    María Josefina Poupin

    2016-04-01

    Full Text Available Modulation of phytohormones homeostasis is one of the proposed mechanisms to explain plant growth promotion induced by beneficial rhizobacteria (PGPR. However, there is still limited knowledge about the molecular signals and pathways underlying these beneficial interactions. Even less is known concerning the interplay between phytohormones in plants inoculated with PGPR. Auxin and ethylene are crucial hormones in the control of plant growth and development, and recent studies report an important and complex crosstalk between them in the regulation of different plant developmental processes. The objective of this work was to study the role of both hormones in the growth promotion of Arabidopsis thaliana plants induced by the well-known PGPR Burkholderia phytofirmans PsJN. For this, the spatiotemporal expression patterns of several genes related to auxin biosynthesis, perception and response and ethylene biosynthesis were studied, finding that most of these genes showed specific transcriptional regulations after inoculation in roots and shoots. PsJN-growth promotion was not observed in Arabidopsis mutants with an impaired ethylene (ein2-1 or auxin (axr1-5 signaling. Even, PsJN did not promote growth in an ethylene overproducer (eto2, indicating that a fine regulation of both hormones signaling and homeostasis is necessary to induce growth of the aerial and root tissues. Auxin polar transport is also involved in growth promotion, since PsJN did not promote primary root growth in the pin2 mutant or under chemical inhibition of transport in wild type plants. Finally, a key role for ethylene biosynthesis was found in the PsJN-mediated increase in root hair number. These results not only give new insights of PGPR regulation of plant growth but also are also useful to understand key aspects of Arabidopsis growth control.

  19. Phosphorylation of ribosomal proteins induced by auxins in maize embryonic tissues

    International Nuclear Information System (INIS)

    Perez, L.; Aguilar, R.; Mendez, A.P.; de Jimenez, E.S.

    1990-01-01

    The effect of auxin on ribosomal protein phosphorylation of germinating maize (Zea mays) tissues was investigated. Two-dimensional gel electrophoresis and autoradiography of [ 32 P] ribosomal protein patterns for natural and synthetic auxin-treated tissues were performed. Both the rate of 32 P incorporation and the electrophoretic patterns were dependent on 32 P pulse length, suggesting that active protein phosphorylation-dephosphorylation occurred in small and large subunit proteins, in control as well as in auxin-treated tissues. The effect of ribosomal protein phosphorylation on in vitro translation was tested. Measurements of poly(U) translation rates as a function of ribosome concentration provided apparent K m values significantly different for auxin-treated and nontreated tissues. These findings suggest that auxin might exert some kind of translational control by regulating the phosphorylated status of ribosomal proteins

  20. Auxin-BR Interaction Regulates Plant Growth and Development

    Science.gov (United States)

    Tian, Huiyu; Lv, Bingsheng; Ding, Tingting; Bai, Mingyi; Ding, Zhaojun

    2018-01-01

    Plants develop a high flexibility to alter growth, development, and metabolism to adapt to the ever-changing environments. Multiple signaling pathways are involved in these processes and the molecular pathways to transduce various developmental signals are not linear but are interconnected by a complex network and even feedback mutually to achieve the final outcome. This review will focus on two important plant hormones, auxin and brassinosteroid (BR), based on the most recent progresses about these two hormone regulated plant growth and development in Arabidopsis, and highlight the cross-talks between these two phytohormones. PMID:29403511

  1. Auxin and plant morphogenesis - a model of regulation

    Directory of Open Access Journals (Sweden)

    Stefan Zajączkowski

    2015-01-01

    Full Text Available In the presented model cells of the plant body form a spatial medium in which three-dimensional morphogenic waves of auxin are propagated. Points in the same phase of oscillation form isophasic surfaces and the vectors of wave propagation form a three-dimensional vector field. The vectors in the case of local inhomogeneities of the medium deviate from organ polarity, providing positional information recognized by cells. Models of functioning of such a supracellular oscillatory system in regulation of tissue differentiation, tropic responses and plant form are discussed.

  2. UGT74D1 is a novel auxin glycosyltransferase from Arabidopsis thaliana.

    Directory of Open Access Journals (Sweden)

    Shang-Hui Jin

    Full Text Available Auxin is one type of phytohormones that plays important roles in nearly all aspects of plant growth and developmental processes. The glycosylation of auxins is considered to be an essential mechanism to control the level of active auxins. Thus, the identification of auxin glycosyltransferases is of great significance for further understanding the auxin regulation. In this study, we biochemically screened the group L of Arabidopsis thaliana glycosyltransferase superfamily for enzymatic activity toward auxins. UGT74D1 was identified to be a novel auxin glycosyltransferase. Through HPLC and LC-MS analysis of reaction products in vitro by testing eight substrates including auxins and other compounds, we found that UGT74D1 had a strong glucosylating activity toward indole-3-butyric acid [IBA], indole-3-propionic acid [IPA], indole-3-acetic acid [IAA] and naphthaleneacetic acid [NAA], catalyzing them to form corresponding glucose esters. Biochemical characterization showed that this enzyme had a maximum activity in HEPES buffer at pH 6.0 and 37°C. In addition, the enzymatic activity analysis of crude protein and the IBA metabolite analysis from transgenic Arabidopsis plants overexpressing UGT74D1 gene were also carried out. Experimental results indicated that over-production of the UGT74D1 in plants indeed led to increased level of the glucose conjugate of IBA. Moreover, UGT74D1 overexpression lines displayed curling leaf phenotype, suggesting a physiological role of UGT74D1 in affecting the activity of auxins. Our current data provide a new target gene for further genetic studies to understand the auxin regulation by glycosylation in plants.

  3. Gravity-induced asymmetric distribution of a plant growth hormone

    Science.gov (United States)

    Bandurski, R. S.; Schulze, A.; Momonoki, Y.

    1984-01-01

    Dolk (1936) demonstrated that gravistimulation induced an asymmetric distribution of auxin in a horizontally-placed shoot. An attempt is made to determine where and how that asymmetry arises, and to demonstrate that the endogenous auxin, indole-3-acetic acid, becomes asymmetrically distributed in the cortical cells of the Zea mays mesocotyl during 3 min of geostimulation. Further, indole-3-acetic acid derived by hydrolysis of an applied transport form of the hormone, indole-3-acetyl-myo-inositol, becomes asymmetrically distributed within 15 min of geostimulus time. From these and prior data is developed a working theory that the gravitational stimulus induces a selective leakage, or secretion, of the hormone from the vascular tissue to the cortical cells of the mesocotyl.

  4. The Cause of Gravity

    OpenAIRE

    Byrne, Michael

    1999-01-01

    Einstein said that gravity is an acceleration like any other acceleration. But gravity causes relativistic effects at non-relativistic speeds; so gravity could have relativistic origins. And since the strong force is thought to cause most of mass, and mass is proportional to gravity; the strong force is therefore also proportional to gravity. The strong force could thus cause relativistic increases of mass through the creation of virtual gluons; along with a comparable contraction of space ar...

  5. Effects of auxin and copper on growth of saffron

    Directory of Open Access Journals (Sweden)

    Mozafar Sharifi

    2014-03-01

    Full Text Available Saffron is known as one of the most common spices and medicinal plant in the world. Little information is available on the effects of copper and growth regulators on morphological characteristics of saffron. The aim of this study was to evaluate the influence of different concentrations of copper and auxin on morphological properties of root and leaf of saffron. This study was arranged as a factorial experiment in greenhouse condition and in hydroponic system. Copper was used in copper sulfate (CuSO4 form (0, 0.02, 0.1 and 0.2 mg/L and auxin in naphthalene acetic acid (NAA form (0, 1 and 2 g/L. Results showed that interaction of Naphthalene acetic acid 1 g/L and copper sulfate 0.1 mg/L increased root number, as well as root and leaf dry weight. Furthermore, naphthalene acetic acid 1 and 2 g/L in most treatments reduced the number of buds. Copper concentration of corm was increased in 0.2 mg/L copper sulfate.

  6. Lateral root formation and the multiple roles of auxin.

    Science.gov (United States)

    Du, Yujuan; Scheres, Ben

    2018-01-04

    Root systems can display variable architectures that contribute to survival strategies of plants. The model plant Arabidopsis thaliana possesses a tap root system, in which the primary root and lateral roots (LRs) are major architectural determinants. The phytohormone auxin fulfils multiple roles throughout LR development. In this review, we summarize recent advances in our understanding of four aspects of LR formation: (i) LR positioning, which determines the spatial distribution of lateral root primordia (LRP) and LRs along primary roots; (ii) LR initiation, encompassing the activation of nuclear migration in specified lateral root founder cells (LRFCs) up to the first asymmetric cell division; (iii) LR outgrowth, the 'primordium-intrinsic' patterning of de novo organ tissues and a meristem; and (iv) LR emergence, an interaction between LRP and overlaying tissues to allow passage through cell layers. We discuss how auxin signaling, embedded in a changing developmental context, plays important roles in all four phases. In addition, we discuss how rapid progress in gene network identification and analysis, modeling, and four-dimensional imaging techniques have led to an increasingly detailed understanding of the dynamic regulatory networks that control LR development. © The Author(s) 2017. Published by Oxford University Press on behalf of the Society for Experimental Biology. All rights reserved. For permissions, please email: journals.permissions@oup.com.

  7. Wall to membrane linkers, stretch activated channels, and the detection of tension, voltage, temperature, auxin, and pH

    Science.gov (United States)

    Pickard, B. G.

    1992-01-01

    Introduction. The higher plant is a heterogeneous, mechanically prestressed structure continually subject to shifting forces. When a cell grows in a plant at gravitropic equilibrium, it must create localized maxima of shear in walls of neighboring cells. Such mechanical stress and strain are likely detected in a variety of ways. However, tension-sensitive ion channels are of particular interest because it appears that they are elaborately evolved for sensory function. We hypothesize that 1) the patchy patterns of high shear are focused via wall-to-membrane linkers onto the plasma membrane, where 2) they are translated by mechanosensory cation channels into corresponding patterns of high cytosolic Ca2+, which 3) initiate local enhancement of wall expansion. Further, we hypothesize that the local promotion of enhancement is achieved at least in part by local intensification of auxin transport across the plasma membrane. By implication, when an organ is asymmetrically pressed, rubbed, or bent or when it is displaced in the gravitational field, the net asymmetry of shear stress occurring across the organ would lead to asymmetric redistribution of auxin and corrective asymmetric growth. We shall describe a representative mechanosensitive Ca(2+) -selective cation channel (MCaC) with susceptibilities to xenobiotics implicating it as a force transducer in thigmo- and gravitropism. Then, we shall consider whether a putative wall-to-membrane linker (WML) could be a key feature of the molecular architecture permitting the stress distributed in the wall system to be focused on the channels.

  8. UV-B Radiation Induces Root Bending Through the Flavonoid-Mediated Auxin Pathway in Arabidopsis.

    Science.gov (United States)

    Wan, Jinpeng; Zhang, Ping; Wang, Ruling; Sun, Liangliang; Wang, Wenying; Zhou, Huakun; Xu, Jin

    2018-01-01

    Ultraviolet (UV)-B radiation-induced root bending has been reported; however, the underlying mechanisms largely remain unclear. Here, we investigate whether and how auxin and flavonoids are involved in UV-B radiation-induced root bending in Arabidopsis using physiological, pharmacological, and genetic approaches. UV-B radiation modulated the direction of root growth by decreasing IAA biosynthesis and affecting auxin distribution in the root tips, where reduced auxin accumulation and asymmetric auxin distribution were observed. UV-B radiation increased the distribution of auxin on the nonradiated side of the root tips, promoting growth and causing root bending. Further analysis indicated that UV-B induced an asymmetric accumulation of flavonoids; this pathway is involved in modulating the accumulation and asymmetric distribution of auxin in root tips and the subsequent redirection of root growth by altering the distribution of auxin carriers in response to UV-B radiation. Taken together, our results indicate that UV-B radiation-induced root bending occurred through a flavonoid-mediated phototropic response to UV-B radiation.

  9. Transportation

    National Research Council Canada - National Science Library

    Adams, James; Carr, Ron; Chebl, Maroun; Coleman, Robert; Costantini, William; Cox, Robert; Dial, William; Jenkins, Robert; McGovern, James; Mueller, Peter

    2006-01-01

    ...., trains, ships, etc.) and maximizing intermodal efficiency. A healthy balance must be achieved between the flow of international commerce and security requirements regardless of transportation mode...

  10. Chiral gravity, log gravity, and extremal CFT

    International Nuclear Information System (INIS)

    Maloney, Alexander; Song Wei; Strominger, Andrew

    2010-01-01

    We show that the linearization of all exact solutions of classical chiral gravity around the AdS 3 vacuum have positive energy. Nonchiral and negative-energy solutions of the linearized equations are infrared divergent at second order, and so are removed from the spectrum. In other words, chirality is confined and the equations of motion have linearization instabilities. We prove that the only stationary, axially symmetric solutions of chiral gravity are BTZ black holes, which have positive energy. It is further shown that classical log gravity--the theory with logarithmically relaxed boundary conditions--has finite asymptotic symmetry generators but is not chiral and hence may be dual at the quantum level to a logarithmic conformal field theories (CFT). Moreover we show that log gravity contains chiral gravity within it as a decoupled charge superselection sector. We formally evaluate the Euclidean sum over geometries of chiral gravity and show that it gives precisely the holomorphic extremal CFT partition function. The modular invariance and integrality of the expansion coefficients of this partition function are consistent with the existence of an exact quantum theory of chiral gravity. We argue that the problem of quantizing chiral gravity is the holographic dual of the problem of constructing an extremal CFT, while quantizing log gravity is dual to the problem of constructing a logarithmic extremal CFT.

  11. Transportation

    International Nuclear Information System (INIS)

    Anon.

    1998-01-01

    Here is the decree of the thirtieth of July 1998 relative to road transportation, to trade and brokerage of wastes. It requires to firms which carry out a road transportation as well as to traders and to brokers of wastes to declare their operations to the prefect. The declaration has to be renewed every five years. (O.M.)

  12. The Arabidopsis gene DIG6 encodes a large 60S subunit nuclear export GTPase 1 that is involved in ribosome biogenesis and affects multiple auxin-regulated development processes

    KAUST Repository

    Zhao, Huayan

    2015-08-13

    The circularly permuted GTPase large subunit GTPase 1 (LSG1) is involved in the maturation step of the 60S ribosome and is essential for cell viability in yeast. Here, an Arabidopsis mutant dig6 (drought inhibited growth of lateral roots) was isolated. The mutant exhibited multiple auxin-related phenotypes, which included reduced lateral root number, altered leaf veins, and shorter roots. Genetic mapping combined with next-generation DNA sequencing identified that the mutation occurred in AtLSG1-2. This gene was highly expressed in regions of auxin accumulation. Ribosome profiling revealed that a loss of function of AtLSG1-2 led to decreased levels of monosomes, further demonstrating its role in ribosome biogenesis. Quantitative proteomics showed that the expression of certain proteins involved in ribosome biogenesis was differentially regulated, indicating that ribosome biogenesis processes were impaired in the mutant. Further investigations showed that an AtLSG1-2 deficiency caused the alteration of auxin distribution, response, and transport in plants. It is concluded that AtLSG1-2 is integral to ribosome biogenesis, consequently affecting auxin homeostasis and plant development.

  13. The Arabidopsis gene DIG6 encodes a large 60S subunit nuclear export GTPase 1 that is involved in ribosome biogenesis and affects multiple auxin-regulated development processes

    KAUST Repository

    Zhao, Huayan; Lü , Shiyou; Li, Ruixi; Chen, Tao; Zhang, Huoming; Cui, Peng; Ding, Feng; Liu, Pei; Wang, Guangchao; Xia, Yiji; Running, Mark P.; Xiong, Liming

    2015-01-01

    The circularly permuted GTPase large subunit GTPase 1 (LSG1) is involved in the maturation step of the 60S ribosome and is essential for cell viability in yeast. Here, an Arabidopsis mutant dig6 (drought inhibited growth of lateral roots) was isolated. The mutant exhibited multiple auxin-related phenotypes, which included reduced lateral root number, altered leaf veins, and shorter roots. Genetic mapping combined with next-generation DNA sequencing identified that the mutation occurred in AtLSG1-2. This gene was highly expressed in regions of auxin accumulation. Ribosome profiling revealed that a loss of function of AtLSG1-2 led to decreased levels of monosomes, further demonstrating its role in ribosome biogenesis. Quantitative proteomics showed that the expression of certain proteins involved in ribosome biogenesis was differentially regulated, indicating that ribosome biogenesis processes were impaired in the mutant. Further investigations showed that an AtLSG1-2 deficiency caused the alteration of auxin distribution, response, and transport in plants. It is concluded that AtLSG1-2 is integral to ribosome biogenesis, consequently affecting auxin homeostasis and plant development.

  14. Light and gravity signals synergize in modulating plant development

    Science.gov (United States)

    Vandenbrink, Joshua P.; Kiss, John Z.; Herranz, Raul; Medina, F. Javier

    2014-01-01

    Tropisms are growth-mediated plant movements that help plants to respond to changes in environmental stimuli. The availability of water and light, as well as the presence of a constant gravity vector, are all environmental stimuli that plants sense and respond to via directed growth movements (tropisms). The plant response to gravity (gravitropism) and the response to unidirectional light (phototropism) have long been shown to be interconnected growth phenomena. Here, we discuss the similarities in these two processes, as well as the known molecular mechanisms behind the tropistic responses. We also highlight research done in a microgravity environment in order to decouple two tropisms through experiments carried out in the absence of a significant unilateral gravity vector. In addition, alteration of gravity, especially the microgravity environment, and light irradiation produce important effects on meristematic cells, the undifferentiated, highly proliferating, totipotent cells which sustain plant development. Microgravity produces the disruption of meristematic competence, i.e., the decoupling of cell proliferation and cell growth, affecting the regulation of the cell cycle and ribosome biogenesis. Light irradiation, especially red light, mediated by phytochromes, has an activating effect on these processes. Phytohormones, particularly auxin, also are key mediators in these alterations. Upcoming experiments on the International Space Station will clarify some of the mechanisms and molecular players of the plant responses to these environmental signals involved in tropisms and the cell cycle. PMID:25389428

  15. Light and gravity signals synergize in modulating plant development

    Directory of Open Access Journals (Sweden)

    Joshua P. Vandenbrink

    2014-10-01

    Full Text Available Tropisms are growth-mediated plant movements that help plants to respond to changes in environmental stimuli. The availability of water and light, as well as the presence of a constant gravity vector, are all environmental stimuli that plants sense and respond to via directed growth movements (tropisms. The plant response to gravity (gravitropism and the response to unidirectional light (phototropism have long been shown to be interconnected growth phenomena. Here, we discuss the similarities in these two processes, as well as the known molecular mechanisms behind the tropistic responses. We also highlight experiments done in a microgravity environment in order to decouple two tropisms through experiments carried out in the absence of a significant unilateral gravity vector. In addition, alteration of gravity, especially the microgravity environment, and light irradiation produce important effects on meristematic cells, the undifferentiated, highly proliferating, totipotent cells which sustain plant development. Microgravity produces the disruption of meristematic competence, i.e. the decoupling of cell proliferation and cell growth, affecting the regulation of cell cycle and ribosome biogenesis. Light irradiation, especially red light, mediated by phytochromes, has an activating effect on these processes. Phytohormones, particularly auxin, are key mediators in these alterations. Upcoming experiments on the International Space Station will clarify some of the unknown mechanisms and molecular players of the plant responses to these environmental signals involved in tropisms and the cell cycle.

  16. Exogenous auxin represses soybean seed germination through decreasing the gibberellin/abscisic acid (GA/ABA) ratio.

    Science.gov (United States)

    Shuai, Haiwei; Meng, Yongjie; Luo, Xiaofeng; Chen, Feng; Zhou, Wenguan; Dai, Yujia; Qi, Ying; Du, Junbo; Yang, Feng; Liu, Jiang; Yang, Wenyu; Shu, Kai

    2017-10-03

    Auxin is an important phytohormone which mediates diverse development processes in plants. Published research has demonstrated that auxin induces seed dormancy. However, the precise mechanisms underlying the effect of auxin on seed germination need further investigation, especially the relationship between auxins and both abscisic acid (ABA) and gibberellins (GAs), the latter two phytohormones being the key regulators of seed germination. Here we report that exogenous auxin treatment represses soybean seed germination by enhancing ABA biosynthesis, while impairing GA biogenesis, and finally decreasing GA 1 /ABA and GA 4 /ABA ratios. Microscope observation showed that auxin treatment delayed rupture of the soybean seed coat and radicle protrusion. qPCR assay revealed that transcription of the genes involved in ABA biosynthetic pathway was up-regulated by application of auxin, while expression of genes involved in GA biosynthetic pathway was down-regulated. Accordingly, further phytohormone quantification shows that auxin significantly increased ABA content, whereas the active GA 1 and GA 4 levels were decreased, resulting insignificant decreases in the ratiosGA 1 /ABA and GA 4 /ABA.Consistent with this, ABA biosynthesis inhibitor fluridone reversed the delayed-germination phenotype associated with auxin treatment, while paclobutrazol, a GA biosynthesis inhibitor, inhibited soybean seed germination. Altogether, exogenous auxin represses soybean seed germination by mediating ABA and GA biosynthesis.

  17. Control of cytokinin and auxin homeostasis in cyanobacteria and algae

    Czech Academy of Sciences Publication Activity Database

    Žižková, Eva; Kubeš, Martin; Dobrev, Petre; Přibyl, Pavel; Šimura, J.; Zahajská, Lenka; Záveská Drábková, Lenka; Novák, Ondřej; Motyka, Václav

    2017-01-01

    Roč. 119, č. 1 (2017), s. 151-166 ISSN 0305-7364 R&D Projects: GA ČR(CZ) GA16-14649S; GA ČR GA15-22322S; GA MŠk(CZ) LO1204 Institutional support: RVO:61389030 ; RVO:67985939 Keywords : solid-phase extraction * performance liquid-chromatography * yucca flavin monooxygenases * tandem mass-spectrometry * abscisic-acid * arabidopsis-thaliana * indole-3-acetic-acid iaa * endogenous cytokinins * chlorella-vulgaris * phenylacetic acid * Cytokinin * auxin * cyanobacteria * algae * metabolism * cytokinin oxidase/dehydrogenase * cytokinin 2-methylthioderivatives * trans-zeatin * indole-3-acetic acid * tRNA Subject RIV: EF - Botanics OBOR OECD: Plant sciences, botany Impact factor: 4.041, year: 2016

  18. A genomics approach to understanding the role of auxin in apple (Malus x domestica) fruit size control.

    Science.gov (United States)

    Devoghalaere, Fanny; Doucen, Thomas; Guitton, Baptiste; Keeling, Jeannette; Payne, Wendy; Ling, Toby John; Ross, John James; Hallett, Ian Charles; Gunaseelan, Kularajathevan; Dayatilake, G A; Diak, Robert; Breen, Ken C; Tustin, D Stuart; Costes, Evelyne; Chagné, David; Schaffer, Robert James; David, Karine Myriam

    2012-01-13

    Auxin is an important phytohormone for fleshy fruit development, having been shown to be involved in the initial signal for fertilisation, fruit size through the control of cell division and cell expansion, and ripening related events. There is considerable knowledge of auxin-related genes, mostly from work in model species. With the apple genome now available, it is possible to carry out genomics studies on auxin-related genes to identify genes that may play roles in specific stages of apple fruit development. High amounts of auxin in the seed compared with the fruit cortex were observed in 'Royal Gala' apples, with amounts increasing through fruit development. Injection of exogenous auxin into developing apples at the start of cell expansion caused an increase in cell size. An expression analysis screen of auxin-related genes involved in auxin reception, homeostasis, and transcriptional regulation showed complex patterns of expression in each class of gene. Two mapping populations were phenotyped for fruit size over multiple seasons, and multiple quantitative trait loci (QTLs) were observed. One QTL mapped to a region containing an Auxin Response Factor (ARF106). This gene is expressed during cell division and cell expansion stages, consistent with a potential role in the control of fruit size. The application of exogenous auxin to apples increased cell expansion, suggesting that endogenous auxin concentrations are at least one of the limiting factors controlling fruit size. The expression analysis of ARF106 linked to a strong QTL for fruit weight suggests that the auxin signal regulating fruit size could partially be modulated through the function of this gene. One class of gene (GH3) removes free auxin by conjugation to amino acids. The lower expression of these GH3 genes during rapid fruit expansion is consistent with the apple maximising auxin concentrations at this point.

  19. Quantum W3 gravity

    International Nuclear Information System (INIS)

    Schoutens, K.; van Nieuwenhuizen, P.; State Univ. of New York, Stony Brook, NY

    1991-11-01

    We briefly review some results in the theory of quantum W 3 gravity in the chiral gauge. We compare them with similar results in the analogous but simpler cases of d = 2 induced gauge theories and d = 2 induced gravity

  20. Urine specific gravity test

    Science.gov (United States)

    ... medlineplus.gov/ency/article/003587.htm Urine specific gravity test To use the sharing features on this page, please enable JavaScript. Urine specific gravity is a laboratory test that shows the concentration ...

  1. Cadiz, California Gravity Data

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The gravity station data (32 records) were gathered by Mr. Seth I. Gutman for AridTech Inc., Denver, Colorado using a Worden Prospector gravity meter. This data base...

  2. Andes 1997 Gravity Data

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Central Andes gravity data (6,151 records) were compiled by Professor Gotze and the MIGRA Group. This data base was received in April, 1997. Principal gravity...

  3. DNAG Gravity Data

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Decade of North American Geology (DNAG) gravity grid values, spaced at 6 km, were used to produce the Gravity Anomaly Map of North America (1987; scale...

  4. Gravity wave astronomy

    International Nuclear Information System (INIS)

    Pinheiro, R.

    1979-01-01

    The properties and production of gravitational radiation are described. The prospects for their detection are considered including the Weber apparatus and gravity-wave telescopes. Possibilities of gravity-wave astronomy are noted

  5. Northern Oklahoma Gravity Data

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The gravity station data (710 records) were compiled by Professor Ahern. This data base was received in June 1992. Principal gravity parameters include latitude,...

  6. Idaho State Gravity Data

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The gravity station data (24,284 records) were compiled by the U. S. Geological Survey. This data base was received on February 23, 1993. Principal gravity...

  7. Transportation

    National Research Council Canada - National Science Library

    Allshouse, Michael; Armstrong, Frederick Henry; Burns, Stephen; Courts, Michael; Denn, Douglas; Fortunato, Paul; Gettings, Daniel; Hansen, David; Hoffman, D. W; Jones, Robert

    2007-01-01

    .... The ability of the global transportation industry to rapidly move passengers and products from one corner of the globe to another continues to amaze even those wise to the dynamics of such operations...

  8. Comparison of auxin activty in tumourous and normal callus cultures from sunflower and tobacco plants

    Directory of Open Access Journals (Sweden)

    Z. Chirek

    2015-01-01

    Full Text Available In normal and tumourous calluses of sunflower and tobacco the level of extractable auxins was determined by Avena coleoptile straight growth test. Auxin activity was detected practically in two zones: I - at position with Rf 0.2-0.4 and II - at position with Rf 0.6-0.9. The tumour tissues of sunflower and tobacco plants, representing different types of neoplastic growth exhibit a 3 times higher auxin activity as compared with that of the corresponding normal tissues. Tobacco tissues, on the other hand, had a higher auxin level than the corresponding sunflower tissues and they exhibited different proportions in the activity of zones I and II, which points to a dominance of genetic regulation of hormone metabolism in these plants.

  9. Inter-regulation of the unfolded protein response and auxin signaling

    Czech Academy of Sciences Publication Activity Database

    Chen, Y.N.; Aung, K.; Rolčík, Jakub; Walicki, K.; Friml, J.; Brandizzi, F.

    2014-01-01

    Roč. 77, č. 1 (2014), s. 97-107 ISSN 0960-7412 Institutional support: RVO:61389030 Keywords : endoplasmic reticulum stress * unfolded protein response * auxin response Subject RIV: ED - Physiology Impact factor: 5.972, year: 2014

  10. The role of auxin and cytokinin signalling in specifying the root architecture of Arabidopsis thaliana

    KAUST Repository

    Muraro, Daniele; Byrne, Helen; King, John; Bennett, Malcolm

    2013-01-01

    these hormones and their signalling pathways. In this paper, sub-cellular and multi-cellular mathematical models are developed to investigate how interactions between auxin and cytokinin influence the size and location of regions of division and differentiation

  11. Influence of time of auxin application on wheat haploid embrio formation

    Directory of Open Access Journals (Sweden)

    Prodanović Slaven

    2005-01-01

    Full Text Available A hybrid interspecies zygote appears after crosses between wheat and maize Zygote derived after usual self-fertilization in wheat is dividing by mitotic divisions into embryo. However, interspecies zygote aborts soon. Auxin treatment is widely used to promote its development. Growth hormones auxins have stimulative ortoxic effects on plant tissue sin relation to its concentration and the time of application. In this paper the effect of time of auxin dicamba application on embryo in wheat x maize crosses was investigated. Chromosomes of pollen donor parent are eliminated quickly in cells of such embryos and they become haploid. It was concluded that for the production of haploid embryos the best time for auxin application is one day after pollination with maize.

  12. Strings and quantum gravity

    International Nuclear Information System (INIS)

    Vega, H.J. de

    1990-01-01

    One of the main challenges in theoretical physics today is the unification of all interactions including gravity. At present, string theories appear as the most promising candidates to achieve such a unification. However, gravity has not completely been incorporated in string theory, many technical and conceptual problems remain and a full quantum theory of gravity is still non-existent. Our aim is to properly understand strings in the context of quantum gravity. Attempts towards this are reviewed. (author)

  13. Concerted transcription of auxin and carbohydrate homeostasis-related genes underlies improved adventitious rooting of microcuttings derived from far-red treated Eucalyptus globulus Labill mother plants.

    Science.gov (United States)

    Ruedell, Carolina Michels; de Almeida, Márcia Rodrigues; Fett-Neto, Arthur Germano

    2015-12-01

    Economically important plant species, such as Eucalyptus globulus, are often rooting recalcitrant. We have previously shown that far-red light enrichment applied to E. globulus donor-plants improved microcutting rooting competence and increased rooting zone/shoot carbohydrate ratio. To better understand this developmental response, the relative expression profiles of genes involved in auxin signaling (ARF6, ARF8, AGO1), biosynthesis (YUC3) and transport (AUX1, PIN1, PIN2); sucrose cleavage (SUS1, CWINV1), transport (SUC5), hexose phosphorylation (HXK1, FLN1) and starch biosynthesis (SS3) were quantified during adventitious rooting of E. globulus microcuttings derived from donor plants exposed to far-red or white light. Expression of auxin transport-related genes increased in the first days of root induction. Far-red enrichment of donor plants induced ARF6, ARF8 and AGO1 in microcuttings. The first two gene products could activate GH3 and other rooting related genes, whereas AGO1 deregulation of the repressor ARF17 may relief rooting inhibition. Increased sink strength at the basal stem with sucrose unloading in root tissue mediated by SUC and subsequent hydrolysis by SUS1 were also supported by gene expression profile. Fructose phosphorylation and starch biosynthesis could also contribute to proper carbon allocation at the site of rooting, as evidenced by increased expression of related genes. These data are in good agreement with increased contents of hexoses and starch at the cutting base severed from far-red exposed donor plants. To sum up, pathways integrating auxin and carbohydrate metabolism were activated in microcuttings derived from donor plants exposed to far red light enrichment, thereby improving rooting response in E. globulus. Copyright © 2015 Elsevier Masson SAS. All rights reserved.

  14. Transcriptome analysis of the rhizosphere bacterium Azospirillum brasilense reveals an extensive auxin response.

    Science.gov (United States)

    Van Puyvelde, Sandra; Cloots, Lore; Engelen, Kristof; Das, Frederik; Marchal, Kathleen; Vanderleyden, Jos; Spaepen, Stijn

    2011-05-01

    The rhizosphere bacterium Azospirillum brasilense produces the auxin indole-3-acetic acid (IAA) through the indole-3-pyruvate pathway. As we previously demonstrated that transcription of the indole-3-pyruvate decarboxylase (ipdC) gene is positively regulated by IAA, produced by A. brasilense itself or added exogenously, we performed a microarray analysis to study the overall effects of IAA on the transcriptome of A. brasilense. The transcriptomes of A. brasilense wild-type and the ipdC knockout mutant, both cultured in the absence and presence of exogenously added IAA, were compared.Interfering with the IAA biosynthesis/homeostasis in A. brasilense through inactivation of the ipdC gene or IAA addition results in much broader transcriptional changes than anticipated. Based on the multitude of changes observed by comparing the different transcriptomes, we can conclude that IAA is a signaling molecule in A. brasilense. It appears that the bacterium, when exposed to IAA, adapts itself to the plant rhizosphere, by changing its arsenal of transport proteins and cell surface proteins. A striking example of adaptation to IAA exposure, as happens in the rhizosphere, is the upregulation of a type VI secretion system (T6SS) in the presence of IAA. The T6SS is described as specifically involved in bacterium-eukaryotic host interactions. Additionally, many transcription factors show an altered regulation as well, indicating that the regulatory machinery of the bacterium is changing.

  15. Geometric Liouville gravity

    International Nuclear Information System (INIS)

    La, H.

    1992-01-01

    A new geometric formulation of Liouville gravity based on the area preserving diffeo-morphism is given and a possible alternative to reinterpret Liouville gravity is suggested, namely, a scalar field coupled to two-dimensional gravity with a curvature constraint

  16. Covariant w∞ gravity

    NARCIS (Netherlands)

    Bergshoeff, E.; Pope, C.N.; Stelle, K.S.

    1990-01-01

    We discuss the notion of higher-spin covariance in w∞ gravity. We show how a recently proposed covariant w∞ gravity action can be obtained from non-chiral w∞ gravity by making field redefinitions that introduce new gauge-field components with corresponding new gauge transformations.

  17. Induced quantum conformal gravity

    International Nuclear Information System (INIS)

    Novozhilov, Y.V.; Vassilevich, D.V.

    1988-11-01

    Quantum gravity is considered as induced by matter degrees of freedom and related to the symmetry breakdown in the low energy region of a non-Abelian gauge theory of fundamental fields. An effective action for quantum conformal gravity is derived where both the gravitational constant and conformal kinetic term are positive. Relation with induced classical gravity is established. (author). 15 refs

  18. Quantum Gravity Phenomenology

    OpenAIRE

    Amelino-Camelia, Giovanni

    2003-01-01

    Comment: 9 pages, LaTex. These notes were prepared while working on an invited contribution to the November 2003 issue of Physics World, which focused on quantum gravity. They intend to give a non-technical introduction (accessible to readers from outside quantum gravity) to "Quantum Gravity Phenomenology"

  19. Gravity is Geometry.

    Science.gov (United States)

    MacKeown, P. K.

    1984-01-01

    Clarifies two concepts of gravity--those of a fictitious force and those of how space and time may have geometry. Reviews the position of Newton's theory of gravity in the context of special relativity and considers why gravity (as distinct from electromagnetics) lends itself to Einstein's revolutionary interpretation. (JN)

  20. Ethylene-auxin interactions regulate lateral root initiation and emergence in Arabidopsis thaliana.

    Science.gov (United States)

    Ivanchenko, Maria G; Muday, Gloria K; Dubrovsky, Joseph G

    2008-07-01

    Plant root systems display considerable plasticity in response to endogenous and environmental signals. Auxin stimulates pericycle cells within elongating primary roots to enter de novo organogenesis, leading to the establishment of new lateral root meristems. Crosstalk between auxin and ethylene in root elongation has been demonstrated, but interactions between these hormones in root branching are not well characterized. We find that enhanced ethylene synthesis, resulting from the application of low concentrations of the ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC), promotes the initiation of lateral root primordia. Treatment with higher doses of ACC strongly inhibits the ability of pericycle cells to initiate new lateral root primordia, but promotes the emergence of existing lateral root primordia: behaviour that is also seen in the eto1 mutation. These effects are correlated with decreased pericycle cell length and increased lateral root primordia cell width. When auxin is applied simultaneously with ACC, ACC is unable to prevent the auxin stimulation of lateral root formation in the root tissues formed prior to ACC exposure. However, in root tissues formed after transfer to ACC, in which elongation is reduced, auxin does not rescue the ethylene inhibition of primordia initiation, but instead increases it by several fold. Mutations that block auxin responses, slr1 and arf7 arf19, render initiation of lateral root primordia insensitive to the promoting effect of low ethylene levels, and mutations that inhibit ethylene-stimulated auxin biosynthesis, wei2 and wei7, reduce the inhibitory effect of higher ethylene levels, consistent with ethylene regulating root branching through interactions with auxin.

  1. Dynamic Modeling of Indole Glucosinolate Hydrolysis and Its Impact on Auxin Signaling

    Directory of Open Access Journals (Sweden)

    Daniel Vik

    2018-04-01

    Full Text Available Plants release chemicals to deter attackers. Arabidopsis thaliana relies on multiple defense compounds, including indol-3-ylmethyl glucosinolate (I3G, which upon hydrolysis initiated by myrosinase enzymes releases a multitude of bioactive compounds, among others, indole-3-acetonitrile and indole-3-acetoisothiocyanate. The highly unstable isothiocyanate rapidly reacts with other molecules. One of the products, indole-3-carbinol, was reported to inhibit auxin signaling through binding to the TIR1 auxin receptor. On the contrary, the nitrile product of I3G hydrolysis can be converted by nitrilase enzymes to form the primary auxin molecule, indole-3-acetic acid, which activates TIR1. This suggests that auxin signaling is subject to both antagonistic and protagonistic effects of I3G hydrolysis upon attack. We hypothesize that I3G hydrolysis and auxin signaling form an incoherent feedforward loop and we build a mathematical model to examine the regulatory network dynamics. We use molecular docking to investigate the possible antagonistic properties of different I3G hydrolysis products by competitive binding to the TIR1 receptor. Our simulations reveal an uncoupling of auxin concentration and signaling, and we determine that enzyme activity and antagonist binding affinity are key parameters for this uncoupling. The molecular docking predicts that several I3G hydrolysis products strongly antagonize auxin signaling. By comparing a tissue disrupting attack – e.g., by chewing insects or necrotrophic pathogens that causes rapid release of I3G hydrolysis products – to sustained cell-autonomous I3G hydrolysis, e.g., upon infection by biotrophic pathogens, we find that each scenario gives rise to distinct auxin signaling dynamics. This suggests that plants have different defense versus growth strategies depending on the nature of the attack.

  2. Auxin-dependent compositional change in Mediator in ARF7- and ARF19-mediated transcription.

    Science.gov (United States)

    Ito, Jun; Fukaki, Hidehiro; Onoda, Makoto; Li, Lin; Li, Chuanyou; Tasaka, Masao; Furutani, Masahiko

    2016-06-07

    Mediator is a multiprotein complex that integrates the signals from transcription factors binding to the promoter and transmits them to achieve gene transcription. The subunits of Mediator complex reside in four modules: the head, middle, tail, and dissociable CDK8 kinase module (CKM). The head, middle, and tail modules form the core Mediator complex, and the association of CKM can modify the function of Mediator in transcription. Here, we show genetic and biochemical evidence that CKM-associated Mediator transmits auxin-dependent transcriptional repression in lateral root (LR) formation. The AUXIN/INDOLE 3-ACETIC ACID 14 (Aux/IAA14) transcriptional repressor inhibits the transcriptional activity of its binding partners AUXIN RESPONSE FACTOR 7 (ARF7) and ARF19 by making a complex with the CKM-associated Mediator. In addition, TOPLESS (TPL), a transcriptional corepressor, forms a bridge between IAA14 and the CKM component MED13 through the physical interaction. ChIP assays show that auxin induces the dissociation of MED13 but not the tail module component MED25 from the ARF7 binding region upstream of its target gene. These findings indicate that auxin-induced degradation of IAA14 changes the module composition of Mediator interacting with ARF7 and ARF19 in the upstream region of their target genes involved in LR formation. We suggest that this regulation leads to a quick switch of signal transmission from ARFs to target gene expression in response to auxin.

  3. Expression Profiling of Strawberry Allergen Fra a during Fruit Ripening Controlled by Exogenous Auxin.

    Science.gov (United States)

    Ishibashi, Misaki; Yoshikawa, Hiroki; Uno, Yuichi

    2017-06-02

    Strawberry fruit contain the allergenic Fra a proteins, members of the pathogenesis-related 10 protein family that causes oral allergic syndrome symptoms. Fra a proteins are involved in the flavonoid biosynthesis pathway, which might be important for color development in fruits. Auxin is an important plant hormone in strawberry fruit that controls fruit fleshiness and ripening. In this study, we treated strawberry fruits with exogenous auxin or auxin inhibitors at pre- and post-harvest stages, and analyzed Fra a transcriptional and translational expression levels during fruit development by real-time PCR and immunoblotting. Pre-harvest treatment with 1-naphthaleneacetic acid (NAA) alone did not affect Fra a expression, but applied in conjunction with achene removal NAA promoted fruit pigmentation and Fra a protein accumulation. The response was developmental stage-specific: Fra a 1 was highly expressed in immature fruit, whereas Fra a 2 was expressed in young to ripe fruit. In post-harvest treatments, auxin did not contribute to Fra a induction. Auxin inhibitors delayed fruit ripening; as a result, they seemed to influence Fra a 1 expression. Thus, Fra a expression was not directly regulated by auxin, but might be associated with the ripening process and/or external factors in a paralog-specific manner.

  4. Low temperature sensing in tulip (Tulipa gesneriana L.) is mediated through an increased response to auxin.

    Science.gov (United States)

    Rietveld, P L; Wilkinson, C; Franssen, H M; Balk, P A; van der Plas, L H; Weisbeek, P J; Douwe de Boer, A

    2000-03-01

    Tulip (Tulipa gesneriana L.) is a bulbous plant species that requires a period of low temperature for proper growth and flowering. The mechanism of sensing the low temperature period is unknown. The study presented in this paper shows that the essential developmental change in tulip bulbs during cold treatment is an increase in sensitivity to the phytohormone auxin. This is demonstrated using a model system consisting of isolated internodes grown on tissue culture medium containing different combinations of the phytohormones auxin and gibberellin. Using mathematical modelling, equations taken from the field of enzyme kinetics were fitted through the data. By doing so it became apparent that longer periods of low temperature resulted in an increased maximum response at a lower auxin concentration. Besides the cold treatment, gibberellin also enhances the response to auxin in the internodes in this in vitro system. A working model describing the relationship between the cold requirement, gibberellin action and auxin sensitivity is put forward. Possible analogies with other cold-requiring processes such as vernalization and stratification, and the interaction of auxin and gibberellin in the stalk elongation process in other plant species are discussed.

  5. Autoradiographic studies with the 14C-IAA in relation to synergism between auxin and non-auxin chemicals in the rooting of bean (Phaseolus vulgaris L.) cuttings

    International Nuclear Information System (INIS)

    Chaudhury, K.G.; Basu, R.N.

    1980-01-01

    Indole and α-naphthol significantly synergized the IAA-induced rooting of P. vulqaris cuttings. The pattern of incorporation of radiocarbon of IAA-I- 14 C and IAA-2- 14 C supplied to the base of the cuttings was, however, not altered by the synergists and the same radioactive metabolites were located on the radioautograms of ethanolic extracts of the hypocotyls of cuttings under the different treatments. The results thereby discount the possibility of formation of bioactive complexes between auxins and synergists as the mechanism of synergism in rooting. The synergists, however, influenced the extent of incorporation of radiocarbon of the labelled auxin molecules into some of the radioactive metabolites. (auth.)

  6. Scales of gravity

    International Nuclear Information System (INIS)

    Dvali, Gia; Kolanovic, Marko; Nitti, Francesco; Gabadadze, Gregory

    2002-01-01

    We propose a framework in which the quantum gravity scale can be as low as 10 -3 eV. The key assumption is that the standard model ultraviolet cutoff is much higher than the quantum gravity scale. This ensures that we observe conventional weak gravity. We construct an explicit brane-world model in which the brane-localized standard model is coupled to strong 5D gravity of infinite-volume flat extra space. Because of the high ultraviolet scale, the standard model fields generate a large graviton kinetic term on the brane. This kinetic term 'shields' the standard model from the strong bulk gravity. As a result, an observer on the brane sees weak 4D gravity up to astronomically large distances beyond which gravity becomes five dimensional. Modeling quantum gravity above its scale by the closed string spectrum we show that the shielding phenomenon protects the standard model from an apparent phenomenological catastrophe due to the exponentially large number of light string states. The collider experiments, astrophysics, cosmology and gravity measurements independently point to the same lower bound on the quantum gravity scale, 10 -3 eV. For this value the model has experimental signatures both for colliders and for submillimeter gravity measurements. Black holes reveal certain interesting properties in this framework

  7. Plasma membrane NADH oxidase of maize roots responds to gravity and imposed centrifugal forces

    Science.gov (United States)

    Bacon, E.; Morre, D. J.

    2001-01-01

    NADH oxidase activities measured with excised roots of dark-grown maize (Zea mays) seedlings and with isolated plasma membrane vesicles from roots of dark-grown maize oscillated with a regular period length of 24 min and were inhibited by the synthetic auxin 2,4-dichlorophenoxyacetic [correction of dichorophenoxyacetic] acid. The activities also responded to orientation with respect to gravity and to imposed centrifugal forces. Turning the roots upside down resulted in stimulation of the activity with a lag of about 10 min. Returning the sections to the normal upright position resulted in a return to initial rates. The activity was stimulated reversibly to a maximum of about 2-fold with isolated plasma membrane vesicles, when subjected to centrifugal forces of 25 to 250 x g for 1 to 4 min duration. These findings are the first report of a gravity-responsive enzymatic activity of plant roots inhibited by auxin and potentially related to the gravity-induced growth response. c2001 Editions scientifiques et medicales Elsevier SAS.

  8. Molecular cloning and characterization of the genes encoding an auxin efflux carrier and the auxin influx carriers associated with the adventitious root formation in mango (Mangifera indica L.) cotyledon segments.

    Science.gov (United States)

    Li, Yun-He; Zou, Ming-Hong; Feng, Bi-Hong; Huang, Xia; Zhang, Zhi; Sun, Guang-Ming

    2012-06-01

    Polar auxin transport (PAT) plays an important role in the adventitious root formation of mango cotyledon segments, but the molecular mechanism remains unclear. In this study, we cloned a gene encoding an auxin efflux carrier (designated as MiPIN1), and we cloned four genes encoding auxin influx carriers (designated as MiAUX1, MiAUX2, MiAUX3 and MiAUX4). The results of a phylogenetic tree analysis indicated that MiPIN1 and the MiAUXs belong to plant PIN and AUXs/LAXs groups. Quantitative real-time PCR indicated that the expression of MiPIN1 and the MiAUXs was lowest at 0 days but sharply increased on and after day 4. During the root formation in the mango cotyledon segments, the MiPIN1 expression in the distal cut surface (DCS) was always higher than the expression in the proximal cut surface (PCS) whereas the expression of the MiAUXs in the PCS was usually higher than in the DCS. This expression pattern might be result in the PAT from the DCS to the PCS, which is essential for the adventitious root formation in the PCS. Our previous study indicated that a pre-treatment of embryos with indole-3-butyric acid (IBA) significantly promoted adventitious rooting in PCS whereas a pre-treatment with 2,3,5-triiodobenzoic acid (TIBA) completely inhibited this rooting. In this study, however, IBA and TIBA pre-treatments slightly changed the expression of MiPIN1. In contrast, while the MiAUX3 and MiAUX4 expression levels were significantly up-regulated by the IBA pre-treatment, the expression levels were down-regulated by the TIBA pre-treatment. These findings imply that MiAUX3 and MiAUX4 are more sensitive to the IBA and TIBA treatments and that they might play important roles during adventitious root formation in mango cotyledon segments. Copyright © 2012 Elsevier Masson SAS. All rights reserved.

  9. Integration of Auxin and Salt Signals by the NAC Transcription Factor NTM2 during Seed Germination in Arabidopsis1[W

    Science.gov (United States)

    Park, Jungmin; Kim, Youn-Sung; Kim, Sang-Gyu; Jung, Jae-Hoon; Woo, Je-Chang; Park, Chung-Mo

    2011-01-01

    Seed germination is regulated through elaborately interacting signaling networks that integrate diverse environmental cues into hormonal signaling pathways. Roles of gibberellic acid and abscisic acid in germination have been studied extensively using Arabidopsis (Arabidopsis thaliana) mutants having alterations in seed germination. Auxin has also been implicated in seed germination. However, how auxin influences germination is largely unknown. Here, we demonstrate that auxin is linked via the IAA30 gene with a salt signaling cascade mediated by the NAM-ATAF1/2-CUC2 transcription factor NTM2/Arabidopsis NAC domain-containing protein 69 (for NAC with Transmembrane Motif1) during seed germination. Germination of the NTM2-deficient ntm2-1 mutant seeds exhibited enhanced resistance to high salinity. However, the salt resistance disappeared in the ntm2-1 mutant overexpressing the IAA30 gene, which was induced by salt in a NTM2-dependent manner. Auxin exhibited no discernible effects on germination under normal growth conditions. Under high salinity, however, whereas exogenous application of auxin further suppressed the germination of control seeds, the auxin effects were reduced in the ntm2-1 mutant. Consistent with the inhibitory effects of auxin on germination, germination of YUCCA 3-overexpressing plants containing elevated levels of active auxin was more severely influenced by salt. These observations indicate that auxin delays seed germination under high salinity through cross talk with the NTM2-mediated salt signaling in Arabidopsis. PMID:21450938

  10. Functional Characterization of PaLAX1, a Putative Auxin Permease, in Heterologous Plant Systems1[W][OA

    Science.gov (United States)

    Hoyerová, Klára; Perry, Lucie; Hand, Paul; Laňková, Martina; Kocábek, Tomáš; May, Sean; Kottová, Jana; Pačes, Jan; Napier, Richard; Zažímalová, Eva

    2008-01-01

    We have isolated the cDNA of the gene PaLAX1 from a wild cherry tree (Prunus avium). The gene and its product are highly similar in sequences to both the cDNAs and the corresponding protein products of AUX/LAX-type genes, coding for putative auxin influx carriers. We have prepared and characterized transformed Nicotiana tabacum and Arabidopsis thaliana plants carrying the gene PaLAX1. We have proved that constitutive overexpression of PaLAX1 is accompanied by changes in the content and distribution of free indole-3-acetic acid, the major endogenous auxin. The increase in free indole-3-acetic acid content in transgenic plants resulted in various phenotype changes, typical for the auxin-overproducing plants. The uptake of synthetic auxin, 2,4-dichlorophenoxyacetic acid, was 3 times higher in transgenic lines compared to the wild-type lines and the treatment with the auxin uptake inhibitor 1-naphthoxyacetic acid reverted the changes caused by the expression of PaLAX1. Moreover, the agravitropic response could be restored by expression of PaLAX1 in the mutant aux1 plants, which are deficient in auxin influx carrier activity. Based on our data, we have concluded that the product of the gene PaLAX1 promotes the uptake of auxin into cells, and, as a putative auxin influx carrier, it affects the content and distribution of free endogenous auxin in transgenic plants. PMID:18184737

  11. Assaying Auxin Receptor Activity Using SPR Assays with F-Box Proteins and Aux/IAA Degrons.

    Science.gov (United States)

    Quareshy, Mussa; Uzunova, Veselina; Prusinska, Justyna M; Napier, Richard M

    2017-01-01

    The identification of TIR1 as an auxin receptor combined with advanced biophysical instrumentation has led to the development of real-time activity assays for auxins. Traditionally, molecules have been assessed for auxinic activity using bioassays, and agrochemical compound discovery continues to be based on "spray and pray" technologies. Here, we describe the methodology behind an SPR-based assay that uses TIR1 and related F-box proteins with surface plasmon resonance spectrometry for rapid compound screening. In addition, methods for collecting kinetic binding data and data processing are given so that they may support programs for rational design of novel auxin ligands.

  12. Einstein gravity emerging from quantum weyl gravity

    International Nuclear Information System (INIS)

    Zee, A.

    1983-01-01

    We advocate a conformal invariant world described by the sum of the Weyl, Dirac, and Yang-Mills action. Quantum fluctuations bring back Einstein gravity so that the long-distance phenomenology is as observed. Formulas for the induced Newton's constant and Eddington's constant are derived in quantized Weyl gravity. We show that the analogue of the trace anomaly for the Weyl action is structurally similar to that for the Yang-Mills action

  13. Transportation

    Science.gov (United States)

    2007-01-01

    Faculty ii INDUSTRY TRAVEL Domestic Assistant Deputy Under Secretary of Defense (Transportation Policy), Washington, DC Department of...developed between the railroad and trucking industries. Railroads: Today’s seven Class I freight railroad systems move 42% of the nation’s intercity ...has been successfully employed in London to reduce congestion and observed by this industry study during its travels . It is currently being

  14. Sterol Methyl Oxidases Affect Embryo Development via Auxin-Associated Mechanisms.

    Science.gov (United States)

    Zhang, Xia; Sun, Shuangli; Nie, Xiang; Boutté, Yohann; Grison, Magali; Li, Panpan; Kuang, Susu; Men, Shuzhen

    2016-05-01

    Sterols are essential molecules for multiple biological processes, including embryogenesis, cell elongation, and endocytosis. The plant sterol biosynthetic pathway is unique in the involvement of two distinct sterol 4α-methyl oxidase (SMO) families, SMO1 and SMO2, which contain three and two isoforms, respectively, and are involved in sequential removal of the two methyl groups at C-4. In this study, we characterized the biological functions of members of the SMO2 gene family. SMO2-1 was strongly expressed in most tissues during Arabidopsis (Arabidopsis thaliana) development, whereas SMO2-2 showed a more specific expression pattern. Although single smo2 mutants displayed no obvious phenotype, the smo2-1 smo2-2 double mutant was embryonic lethal, and the smo2-1 smo2-2/+ mutant was dwarf, whereas the smo2-1/+ smo2-2 mutant exhibited a moderate phenotype. The phenotypes of the smo2 mutants resembled those of auxin-defective mutants. Indeed, the expression of DR5rev:GFP, an auxin-responsive reporter, was reduced and abnormal in smo2-1 smo2-2 embryos. Furthermore, the expression and subcellular localization of the PIN1 auxin efflux facilitator also were altered. Consistent with these observations, either the exogenous application of auxin or endogenous auxin overproduction (YUCCA9 overexpression) partially rescued the smo2-1 smo2-2 embryonic lethality. Surprisingly, the dwarf phenotype of smo2-1 smo2-2/+ was completely rescued by YUCCA9 overexpression. Gas chromatography-mass spectrometry analysis revealed a substantial accumulation of 4α-methylsterols, substrates of SMO2, in smo2 heterozygous double mutants. Together, our data suggest that SMO2s are important for correct sterol composition and function partially through effects on auxin accumulation, auxin response, and PIN1 expression to regulate Arabidopsis embryogenesis and postembryonic development. © 2016 American Society of Plant Biologists. All Rights Reserved.

  15. Sterol Methyl Oxidases Affect Embryo Development via Auxin-Associated Mechanisms1

    Science.gov (United States)

    Zhang, Xia; Sun, Shuangli; Nie, Xiang; Boutté, Yohann; Grison, Magali; Li, Panpan; Kuang, Susu

    2016-01-01

    Sterols are essential molecules for multiple biological processes, including embryogenesis, cell elongation, and endocytosis. The plant sterol biosynthetic pathway is unique in the involvement of two distinct sterol 4α-methyl oxidase (SMO) families, SMO1 and SMO2, which contain three and two isoforms, respectively, and are involved in sequential removal of the two methyl groups at C-4. In this study, we characterized the biological functions of members of the SMO2 gene family. SMO2-1 was strongly expressed in most tissues during Arabidopsis (Arabidopsis thaliana) development, whereas SMO2-2 showed a more specific expression pattern. Although single smo2 mutants displayed no obvious phenotype, the smo2-1 smo2-2 double mutant was embryonic lethal, and the smo2-1 smo2-2/+ mutant was dwarf, whereas the smo2-1/+ smo2-2 mutant exhibited a moderate phenotype. The phenotypes of the smo2 mutants resembled those of auxin-defective mutants. Indeed, the expression of DR5rev:GFP, an auxin-responsive reporter, was reduced and abnormal in smo2-1 smo2-2 embryos. Furthermore, the expression and subcellular localization of the PIN1 auxin efflux facilitator also were altered. Consistent with these observations, either the exogenous application of auxin or endogenous auxin overproduction (YUCCA9 overexpression) partially rescued the smo2-1 smo2-2 embryonic lethality. Surprisingly, the dwarf phenotype of smo2-1 smo2-2/+ was completely rescued by YUCCA9 overexpression. Gas chromatography-mass spectrometry analysis revealed a substantial accumulation of 4α-methylsterols, substrates of SMO2, in smo2 heterozygous double mutants. Together, our data suggest that SMO2s are important for correct sterol composition and function partially through effects on auxin accumulation, auxin response, and PIN1 expression to regulate Arabidopsis embryogenesis and postembryonic development. PMID:27006488

  16. YUCCA6 over-expression demonstrates auxin function in delaying leaf senescence in Arabidopsis thaliana

    KAUST Repository

    Kim, Jeong Im

    2011-04-21

    The Arabidopsis thaliana YUCCA family of flavin monooxygenase proteins catalyses a rate-limiting step in de novo auxin biosynthesis. A YUCCA6 activation mutant, yuc6-1D, has been shown to contain an elevated free IAA level and to display typical high-auxin phenotypes. It is reported here that Arabidopsis plants over-expressing YUCCA6, such as the yuc6-1D activation mutant and 35S:YUC6 transgenic plants, displayed dramatic longevity. In addition, plants over-expressing YUCCA6 exhibited classical, delayed dark-induced and hormone-induced senescence in assays using detached rosette leaves. However, plants over-expressing an allele of YUCCA6, that carries mutations in the NADPH cofactor binding site, exhibited neither delayed leaf senescence phenotypes nor phenotypes typical of auxin overproduction. When the level of free IAA was reduced in yuc6-1D by conjugation to lysine, yuc6-1D leaves senesced at a rate similar to the wild-type leaves. Dark-induced senescence in detached leaves was accompanied by a decrease in their free IAA content, by the reduced expression of auxin biosynthesis enzymes such as YUCCA1 and YUCCA6 that increase cellular free IAA levels, and by the increased expression of auxin-conjugating enzymes encoded by the GH3 genes that reduce the cellular free auxin levels. Reduced transcript abundances of SAG12, NAC1, and NAC6 during senescence in yuc6-1D compared with the wild type suggested that auxin delays senescence by directly or indirectly regulating the expression of senescence-associated genes. 2011 The Author(s).

  17. Is auxin involved in the induction of genetic instability in barley homeotic double mutants?

    Science.gov (United States)

    Šiukšta, Raimondas; Vaitkūnienė, Virginija; Rančelis, Vytautas

    2018-02-01

    The triggers of genetic instability in barley homeotic double mutants are tweaky spike -type mutations associated with an auxin imbalance in separate spike phytomeres. Barley homeotic tweaky spike;Hooded (tw;Hd) double mutants are characterized by an inherited instability of spike and flower development, which is absent in the single parental constituents. The aim of the present study was to show that the trigger of genetic instability in the double mutants is the tw mutations, which are associated with an auxin imbalance in the developing spikes. Their pleiotropic effects on genes related to spike/flower development may cause the genetic instability of double mutants. The study of four double-mutant groups composed of different mutant alleles showed that the instability arose only if the mutant allele tw was a constituent of the double mutants. Application of auxin inhibitors and 2,4-dichlorophenoxyacetic acid (2,4-D) demonstrated the relationship of the instability of the double mutants and the phenotype of the tw mutants to auxin imbalance. 2,4-D induced phenocopies of the tw mutation in wild-type plants and rescued the phenotypes of three allelic tw mutants. The differential display (dd-PCR) method allowed the identification of several putative candidate genes in tw that may be responsible for the initiation of instability in the double mutants by pleiotropic variations of their expression in the tw mutant associated with auxin imbalance in the developing spikes. The results of the present study linked the genetic instability of homeotic double mutants with an auxin imbalance caused by one of the constituents (tw). The genetic instability of the double mutants in relation to auxin imbalance was studied for the first time. A matrocliny on instability expression was also observed.

  18. AUXIN BINDING PROTEIN 4 is involved in the Ca2+/auxin-regulated expression of ZCAX3 gene in maize (Zea mays)

    Czech Academy of Sciences Publication Activity Database

    Jurišić-Knežev, Dejana; Bergougnoux, Véronique; Milde, D.; Fellner, Martin

    2014-01-01

    Roč. 92, č. 5 (2014), s. 332-339 ISSN 1916-2790 R&D Projects: GA MŠk 1P05ME792 Institutional support: RVO:61389030 Keywords : auxin-binding protein * ABP4 * AtCAX1 Subject RIV: EF - Botanics Impact factor: 1.278, year: 2014

  19. Lower dimensional gravity

    International Nuclear Information System (INIS)

    Brown, J.D.

    1988-01-01

    This book addresses the subject of gravity theories in two and three spacetime dimensions. The prevailing philosophy is that lower dimensional models of gravity provide a useful arena for developing new ideas and insights, which are applicable to four dimensional gravity. The first chapter consists of a comprehensive introduction to both two and three dimensional gravity, including a discussion of their basic structures. In the second chapter, the asymptotic structure of three dimensional Einstein gravity with a negative cosmological constant is analyzed. The third chapter contains a treatment of the effects of matter sources in classical two dimensional gravity. The fourth chapter gives a complete analysis of particle pair creation by electric and gravitational fields in two dimensions, and the resulting effect on the cosmological constant

  20. Gravity interpretation via EULDPH

    International Nuclear Information System (INIS)

    Ebrahimzadeh Ardestani, V.

    2003-01-01

    Euler's homogeneity equation for determining the coordinates of the source body especially to estimate the depth (EULDPH) is discussed at this paper. This method is applied to synthetic and high-resolution real data such as gradiometric or microgravity data. Low-quality gravity data especially in the areas with a complex geology structure has rarely been used. The Bouguer gravity anomalies are computed from absolute gravity data after the required corrections. Bouguer anomaly is transferred to residual gravity anomaly. The gravity gradients are estimated from residual anomaly values. Bouguer anomaly is the gravity gradients, using EULDPH. The coordinates of the perturbing body will be determined. Two field examples one in the east of Tehran (Mard Abad) where we would like to determine the location of the anomaly (hydrocarbon) and another in the south-east of Iran close to the border with Afghanistan (Nosrat Abad) where we are exploring chromite are presented

  1. Gravity effects on endogenous movements

    Science.gov (United States)

    Johnsson, Anders; Antonsen, Frank

    Gravity effects on endogenous movements A. Johnsson * and F. Antonsen *+ * Department of Physics, Norwegian University of Science and Technology,NO-7491, Trond-heim, Norway, E-mail: anders.johnsson@ntnu.no + Present address: Statoil Research Center Trondheim, NO-7005, Trondheim, Norway Circumnutations in stems/shoots exist in many plants and often consists of more or less regular helical movements around the plumb line under Earth conditions. Recent results on circumnu-tations of Arabidopsis in space (Johnsson et al. 2009) showed that minute amplitude oscilla-tions exist in weightlessness, but that centripetal acceleration (mimicking the gravity) amplified and/or created large amplitude oscillations. Fundamental mechanisms underlying these results will be discussed by modeling the plant tissue as a cylinder of cells coupled together. As a starting point we have modeled (Antonsen 1998) standing waves on a ring of biological cells, as first discussed in a classical paper (Turing 1952). If the coupled cells can change their water content, an `extension' wave could move around the ring. We have studied several, stacked rings of cells coupled into a cylinder that together represent a cylindrical plant tissue. Waves of extensions travelling around the cylinder could then represent the observable circumnutations. The coupling between cells can be due to cell-to-cell diffusion, or to transport via channels, and the coupling can be modeled to vary in both longitudinal and transversal direction of the cylinder. The results from ISS experiments indicate that this cylindrical model of coupled cells should be able to 1) show self-sustained oscillations without the impact of gravity (being en-dogenous) and 2) show how an environmental factor like gravity can amplify or generate the oscillatory movements. Gravity has been introduced in the model by a negative, time-delayed feed-back transport across the cylinder. This represents the physiological reactions to acceler

  2. Anomalies and gravity

    International Nuclear Information System (INIS)

    Mielke, Eckehard W.

    2006-01-01

    Anomalies in Yang-Mills type gauge theories of gravity are reviewed. Particular attention is paid to the relation between the Dirac spin, the axial current j5 and the non-covariant gauge spin C. Using diagrammatic techniques, we show that only generalizations of the U(1)- Pontrjagin four-form F and F = dC arise in the chiral anomaly, even when coupled to gravity. Implications for Ashtekar's canonical approach to quantum gravity are discussed

  3. SEPALLATA1/2-suppressed mature apples have low ethylene, high auxin and reduced transcription of ripening-related genes

    Science.gov (United States)

    Schaffer, Robert J.; Ireland, Hilary S.; Ross, John J.; Ling, Toby J.; David, Karine M.

    2012-01-01

    Background and aims Fruit ripening is an important developmental trait in fleshy fruits, making the fruit palatable for seed dispersers. In some fruit species, there is a strong association between auxin concentrations and fruit ripening. We investigated the relationship between auxin concentrations and the onset of ethylene-related ripening in Malus × domestica (apples) at both the hormone and transcriptome levels. Methodology Transgenic apples suppressed for the SEPALLATA1/2 (SEP1/2) class of gene (MADS8/9) that showed severely reduced ripening were compared with untransformed control apples. In each apple type, free indole-3-acetic acid (IAA) concentrations were measured during early ripening. The changes observed in auxin were assessed in light of global changes in gene expression. Principal results It was found that mature MADS8/9-suppressed apples had a higher concentration of free IAA. This was associated with increased expression of the auxin biosynthetic genes in the indole-3-acetamide pathway. Additionally, in the MADS8/9-suppressed apples, there was less expression of the GH3 auxin-conjugating enzymes. A number of genes involved in the auxin-regulated transcription (AUX/IAA and ARF classes of genes) were also observed to change in expression, suggesting a mechanism for signal transduction at the start of ripening. Conclusions The delay in ripening observed in MADS8/9-suppressed apples may be partly due to high auxin concentrations. We propose that, to achieve low auxin associated with fruit maturation, the auxin homeostasis is controlled in a two-pronged manner: (i) by the reduction in biosynthesis and (ii) by an increase in auxin conjugation. This is associated with the change in expression of auxin-signalling genes and the up-regulation of ripening-related genes. PMID:23346344

  4. Pengaruh penambahan auxin terhadap pertunasan dan perakaran kopi arabika perbanyakan Somatic Embryogenesis (The effects of shooting and rooting of arabica coffee propagation through Embryogenesis Somatic auxin uses.

    Directory of Open Access Journals (Sweden)

    Rina Arimarsetiowati

    2012-08-01

    Full Text Available Plantlet that has developed shoots and roots will have a high level adaptation in the field. The objective of this experiment was to improve the ability of planlet in shooting and rooting so that it is ready for acclimatization in the field. The increase ability in shooting and rooting of the planlet were conducted by adding various types of auxin in the media. The arabica coffee embryo of clone AS 2K which has entered the phase of the cotyledons was transfered into the treatment media containing half-strength of MS (Murashige & Skoog macro and micro nutrient, vitamin B5, 30 g/L glucose, 100 ml/L coconut water, 50 mg/L AgNO3 added with the combination of IAA, IBA and NAA. The research was conducted by using completely randomized design with seven combined treatment i.e. 0.1 mg/L IBA, 0.1 mg/L NAA, 0.1 mg/L IAA; 0 , 1 mg/L IBA + 0.1 mg/L NAA, 0.1 mg/L IBA + 0.1 mg/L IAA, 0.1 mg/L NAA + 0.1 mg/L IAA; without auxin. There were 12 replications in every treatment and each replication consisted of five cotyledonary embryos. The parameters of observation were the root length, leaf number, leaf area, stem diameter, and height of plantlets. The observations were conducted in eighth weeks after cotyledonary embryo had shoots. The results showed that in the number of leaves and height of planlet parameters, the treatment without auxin was the best result compared to planlet with auxin addition. The addition of auxin varians and their combination did not significantly influent leaf area, root length and stem diameter parameters. The medium tested was optimum for the growth of shoots and roots of AS 2K arabica coffee.

  5. Overexpression of GbWRKY1 positively regulates the Pi starvation response by alteration of auxin sensitivity in Arabidopsis.

    Science.gov (United States)

    Xu, Li; Jin, Li; Long, Lu; Liu, Linlin; He, Xin; Gao, Wei; Zhu, Longfu; Zhang, Xianlong

    2012-12-01

    Overexpression of a cotton defense-related gene GbWRKY1 in Arabidopsis resulted in modification of the root system by enhanced auxin sensitivity to positively regulate the Pi starvation response. GbWRKY1 was a cloned WRKY transcription factor from Gossypium barbadense, which was firstly identified as a defense-related gene and showed moderate similarity with AtWRKY75 from Arabidopsis thaliana. Overexpression of GbWRKY1 in Arabidopsis resulted in attenuated Pi starvation stress symptoms, including reduced accumulation of anthocyanin and impaired density of lateral roots (LR) in low Pi stress. The study also indicated that overexpression of GbWRKY1 caused plants constitutively exhibited Pi starvation response including increased development of LR, relatively high level of total P and Pi, high expression level of some high-affinity Pi transporters and phosphatases as well as enhanced accumulation of acid phosphatases activity during Pi-sufficient. It was speculated that GbWRKY1 may act as a positive regulator in the Pi starvation response as well as AtWRKY75. GbWRKY1 probably involves in the modulation of Pi homeostasis and participates in the Pi allocation and remobilization but do not accumulate more Pi in Pi-deficient condition, which was different from the fact that AtWRKY75 influenced the Pi status of the plant during Pi deprivation by increasing root surface area and accumulation of more Pi. Otherwise, further study suggested that the overexpression plants were more sensitive to auxin than wild-type and GbWRKY1 may partly influence the LPR1-dependent (low phosphate response 1) Pi starvation signaling pathway and was putatively independent of SUMO E3 ligase SIZ1 and PHR1 (phosphate starvation response 1) in response to Pi starvation.

  6. influence of gravity

    Directory of Open Access Journals (Sweden)

    Animesh Mukherjee

    1991-01-01

    Full Text Available Based upon Biot's [1965] theory of initial stresses of hydrostatic nature produced by the effect of gravity, a study is made of surface waves in higher order visco-elastic media under the influence of gravity. The equation for the wave velocity of Stonely waves in the presence of viscous and gravitational effects is obtained. This is followed by particular cases of surface waves including Rayleigh waves and Love waves in the presence of viscous and gravity effects. In all cases the wave-velocity equations are found to be in perfect agreement with the corresponding classical results when the effects of gravity and viscosity are neglected.

  7. Gravity inversion code

    International Nuclear Information System (INIS)

    Burkhard, N.R.

    1979-01-01

    The gravity inversion code applies stabilized linear inverse theory to determine the topography of a subsurface density anomaly from Bouguer gravity data. The gravity inversion program consists of four source codes: SEARCH, TREND, INVERT, and AVERAGE. TREND and INVERT are used iteratively to converge on a solution. SEARCH forms the input gravity data files for Nevada Test Site data. AVERAGE performs a covariance analysis on the solution. This document describes the necessary input files and the proper operation of the code. 2 figures, 2 tables

  8. Classical Weyl transverse gravity

    Energy Technology Data Exchange (ETDEWEB)

    Oda, Ichiro [University of the Ryukyus, Department of Physics, Faculty of Science, Nishihara, Okinawa (Japan)

    2017-05-15

    We study various classical aspects of the Weyl transverse (WTDiff) gravity in a general space-time dimension. First of all, we clarify a classical equivalence among three kinds of gravitational theories, those are, the conformally invariant scalar tensor gravity, Einstein's general relativity and the WTDiff gravity via the gauge-fixing procedure. Secondly, we show that in the WTDiff gravity the cosmological constant is a mere integration constant as in unimodular gravity, but it does not receive any radiative corrections unlike the unimodular gravity. A key point in this proof is to construct a covariantly conserved energy-momentum tensor, which is achieved on the basis of this equivalence relation. Thirdly, we demonstrate that the Noether current for the Weyl transformation is identically vanishing, thereby implying that the Weyl symmetry existing in both the conformally invariant scalar tensor gravity and the WTDiff gravity is a ''fake'' symmetry. We find it possible to extend this proof to all matter fields, i.e. the Weyl-invariant scalar, vector and spinor fields. Fourthly, it is explicitly shown that in the WTDiff gravity the Schwarzschild black hole metric and a charged black hole one are classical solutions to the equations of motion only when they are expressed in the Cartesian coordinate system. Finally, we consider the Friedmann-Lemaitre-Robertson-Walker (FLRW) cosmology and provide some exact solutions. (orig.)

  9. Manipulation of Auxin Response Factor 19 affects seed size in the woody perennial Jatropha curcas

    Science.gov (United States)

    Sun, Yanwei; Wang, Chunming; Wang, Ning; Jiang, Xiyuan; Mao, Huizhu; Zhu, Changxiang; Wen, Fujiang; Wang, Xianghua; Lu, Zhijun; Yue, Genhua; Xu, Zengfu; Ye, Jian

    2017-01-01

    Seed size is a major determinant of seed yield but few is known about the genetics controlling of seed size in plants. Phytohormones cytokinin and brassinosteroid were known to be involved in the regulation of herbaceous plant seed development. Here we identified a homolog of Auxin Response Factor 19 (JcARF19) from a woody plant Jatropha curcas and genetically demonstrated its functions in controlling seed size and seed yield. Through Virus Induced Gene Silencing (VIGS), we found that JcARF19 was a positive upstream modulator in auxin signaling and may control plant organ size in J. curcas. Importantly, transgenic overexpression of JcARF19 significantly increased seed size and seed yield in plants Arabidopsis thaliana and J. curcas, indicating the importance of auxin pathway in seed yield controlling in dicot plants. Transcripts analysis indicated that ectopic expression of JcARF19 in J. curcas upregulated auxin responsive genes encoding essential regulators in cell differentiation and cytoskeletal dynamics of seed development. Our data suggested the potential of improving seed traits by precisely engineering auxin signaling in woody perennial plants. PMID:28102350

  10. Perturbation of Auxin Homeostasis and Signaling by PINOID Overexpression Induces Stress Responses in Arabidopsis

    Directory of Open Access Journals (Sweden)

    Kumud Saini

    2017-08-01

    Full Text Available Under normal and stress conditions plant growth require a complex interplay between phytohormones and reactive oxygen species (ROS. However, details of the nature of this crosstalk remain elusive. Here, we demonstrate that PINOID (PID, a serine threonine kinase of the AGC kinase family, perturbs auxin homeostasis, which in turn modulates rosette growth and induces stress responses in Arabidopsis plants. Arabidopsis mutants and transgenic plants with altered PID expression were used to study the effect on auxin levels and stress-related responses. In the leaves of plants with ectopic PID expression an accumulation of auxin, oxidative burst and disruption of hormonal balance was apparent. Furthermore, PID overexpression led to the accumulation of antioxidant metabolites, while pid knockout mutants showed only moderate changes in stress-related metabolites. These physiological changes in the plants overexpressing PID modulated their response toward external drought and osmotic stress treatments when compared to the wild type. Based on the morphological, transcriptome, and metabolite results, we propose that perturbations in the auxin hormone levels caused by PID overexpression, along with other hormones and ROS downstream, cause antioxidant accumulation and modify growth and stress responses in Arabidopsis. Our data provide further proof for a strong correlation between auxin and stress biology.

  11. Effect of auxins and associated biochemical changes during clonal propagation of the biofuel plant - Jatropha curcas

    Energy Technology Data Exchange (ETDEWEB)

    Kochhar, Sunita; Singh, S.P.; Kochhar, V.K. [National Botanical Research Institute, Lucknow 226001 (India)

    2008-12-15

    Rooting and sprouting behaviour of stem cuttings of biofuel plant Jatropha curcas and their performance under field conditions have been studied in relation to auxin application. Pretreatment with indole-3-butyric acid (IBA) and 1-naphthalene acetic acid (NAA) increased both the rooting and sprouting. Sprouting of buds on the cuttings preceded rooting. The rooting and sprouting in J. curcas was more with IBA than NAA. The endogenous auxin contents were found to increase almost 15 days prior to rooting, indicating that mobilization of auxin rather than the absolute contents of auxin may be involved in root initiation. Indole acetic acid oxidase (IAA-oxidase) seems to be involved for triggering and initiating the roots/root primordia, whereas peroxidase is involved in both root initiation and the elongation processes as supported by the peroxidase and IAA-oxidase isoenzyme analysis in the cuttings. The clonally propagated plants (cutting-raised plants) performed better in the field as compared to those raised from the seeds. The plants produced from auxin-treated cuttings produced fruits and seeds in the same year as compared to the plants raised from seeds or from untreated or control cuttings that did not produce any seeds in 1 year of this study. Jatropha plants in general produce seeds after 2-3 years. (author)

  12. Influence of External Nitrogen on Nitrogenase Enzyme Activity and Auxin Production in Herbaspirillum seropedicae (Z78).

    Science.gov (United States)

    Yin, Tan Tzy; Pin, Ui Li; Ghazali, Amir Hamzah Ahmad

    2015-04-01

    The production of nitrogenase enzyme and auxins by free living diazotrophs has the potential to influence the growth of host plants. In this study, diazotrophs were grown in the presence of various concentrations of nitogen (N) to determine the optimal concentration of N for microbial growth stimulation, promotion of gaseous N (N2) fixation, and phytohormone production. Therefore, we investigate whether different levels of N supplied to Herbaspirillum seropedicae (Z78) have significant effects on nitrogenase activity and auxin production. The highest nitrogenase activity and the lowest auxin production of H. seropedicae (Z78) were both recorded at 0 gL(-1) of NH4Cl. Higher levels of external N caused a significant decrease in the nitrogenase activity and an increased production of auxins. In a subsequent test, two different inoculum sizes of Z78 (10(6) and 10(12) cfu/ml) were used to study the effect of different percentages of acetylene on nitrogenase activity of the inoculum via the acetylene reduction assay (ARA). The results showed that the optimal amount of acetylene required for nitrogenase enzyme activity was 5% for the 10(6) cfu/ml inoculum, whereas the higher inoculum size (10(12) cfu/ml) required at least 10% of acetylene for optimal nitrogenase activity. These findings provide a clearer understanding of the effects of N levels on diazotrophic nitrogenase activity and auxin production, which are important factors influencing plant growth.

  13. Morphophysiology, Phenotypic and Molecular Diversity of Auxin-induced Passiflora mucronata Lam. (Passifloraceae).

    Science.gov (United States)

    França, Juliany M; Venial, Lucimara R; Costa, Eloá B; Schmildt, Edilson R; Schmildt, Omar; Bernardes, Paula M; Tatagiba, Sandro D; Lopes, José C; Ferreira, Marcia F S; Alexandre, Rodrigo S

    2018-01-01

    Genetic diversity allows identification of potential intraspecific genotypes in the genus Passiflora. The objective of this study was to examine the morphological and genetic diversity of auxin-induced Passiflora mucronata. The experiments were arranged in a complete randomized block design, with a 9 x 2 factorial arrangement (nine genotypes x presence and absence of auxin, indole-3-butyric acid (IBA)), with four replicates of 16 cuttings. The rooting and vegetative growth responses were variable. Genotype 5 was more responsive in the absence of IBA and genotypes 3, 8 and 9 were more responsive in the presence of IBA. Auxin increased rooting rate and percentage, reducing the average time of root protrusion in eight days. IBA also contributed to increase photosynthesis and dry root and shoot mass in 55.55 and 44.44% of the genotypes, respectively. The highest relative contribution to phenotypic diversity in the absence of auxin was rate (38.75%) and percentage (20.27%) of rooting, whereas in the presence of auxin was stomatal conductance (23.19%) and root dry mass (20.91%). Similarity was found for phenotypic and molecular divergence in the presence of IBA, in which genotypes 1 and 6; genotypes 5, 8 and 9; and genotype 3 were clustered in distinct groups.

  14. Function of type-2 Arabidopsis hemoglobin in the auxin-mediated formation of embryogenic cells during morphogenesis

    DEFF Research Database (Denmark)

    Elhiti, Mohamed; Hebelstrup, Kim; Wang, Aiming

    2013-01-01

    Suppression of the Arabidopsis GLB2, a type-2 nonsymbiotic hemoglobin, enhances somatic embryogenesis by increasing auxin production. In the glb2 knock-out line (GLB2 -/-) polarization of PIN1 proteins and auxin maxima occurred at the base of the cotyledons of the zygotic explants, which are the ...

  15. Auxin increases the hydrogen peroxide (H2O2) concentration in tomato (Solanum lycopersicum) root tips while inhibiting root growth

    NARCIS (Netherlands)

    Ivanchenko, Maria G.; den Os, Desiree; Monshausen, Gabriele B.; Dubrovsky, Joseph G.; Bednarova, Andrea; Krishnan, Natraj

    2013-01-01

    The hormone auxin and reactive oxygen species (ROS) regulate root elongation, but the interactions between the two pathways are not well understood. The aim of this study was to investigate how auxin interacts with ROS in regulating root elongation in tomato, Solanum lycopersicum. Wild-type and

  16. Interior Alaska Bouguer Gravity Anomaly

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — A 1 kilometer Complete Bouguer Anomaly gravity grid of interior Alaska. Only those grid cells within 10 kilometers of a gravity data point have gravity values....

  17. Consistency of orthodox gravity

    Energy Technology Data Exchange (ETDEWEB)

    Bellucci, S. [INFN, Frascati (Italy). Laboratori Nazionali di Frascati; Shiekh, A. [International Centre for Theoretical Physics, Trieste (Italy)

    1997-01-01

    A recent proposal for quantizing gravity is investigated for self consistency. The existence of a fixed-point all-order solution is found, corresponding to a consistent quantum gravity. A criterion to unify couplings is suggested, by invoking an application of their argument to more complex systems.

  18. Generalized pure Lovelock gravity

    Science.gov (United States)

    Concha, Patrick; Rodríguez, Evelyn

    2017-11-01

    We present a generalization of the n-dimensional (pure) Lovelock Gravity theory based on an enlarged Lorentz symmetry. In particular, we propose an alternative way to introduce a cosmological term. Interestingly, we show that the usual pure Lovelock gravity is recovered in a matter-free configuration. The five and six-dimensional cases are explicitly studied.

  19. Generalized pure Lovelock gravity

    Directory of Open Access Journals (Sweden)

    Patrick Concha

    2017-11-01

    Full Text Available We present a generalization of the n-dimensional (pure Lovelock Gravity theory based on an enlarged Lorentz symmetry. In particular, we propose an alternative way to introduce a cosmological term. Interestingly, we show that the usual pure Lovelock gravity is recovered in a matter-free configuration. The five and six-dimensional cases are explicitly studied.

  20. Evidence That Chlorinated Auxin Is Restricted to the Fabaceae But Not to the Fabeae1[OPEN

    Science.gov (United States)

    McAdam, Scott A.M.; McAdam, Erin L.

    2015-01-01

    Auxin is a pivotal plant hormone, usually occurring in the form of indole-3-acetic acid (IAA). However, in maturing pea (Pisum sativum) seeds, the level of the chlorinated auxin, 4-chloroindole-3-acetic acid (4-Cl-IAA), greatly exceeds that of IAA. A key issue is how plants produce halogenated compounds such as 4-Cl-IAA. To better understand this topic, we investigated the distribution of the chlorinated auxin. We show for the first time, to our knowledge, that 4-Cl-IAA is found in the seeds of Medicago truncatula, Melilotus indicus, and three species of Trifolium. Furthermore, we found no evidence that Pinus spp. synthesize 4-Cl-IAA in seeds, contrary to a previous report. The evidence indicates a single evolutionary origin of 4-Cl-IAA synthesis in the Fabaceae, which may provide an ideal model system to further investigate the action and activity of halogenating enzymes in plants. PMID:25971549

  1. A synthetic auxin (NAA) suppresses secondary wall cellulose synthesis and enhances elongation in cultured cotton fiber.

    Science.gov (United States)

    Singh, Bir; Cheek, Hannah D; Haigler, Candace H

    2009-07-01

    Use of a synthetic auxin (naphthalene-1-acetic acid, NAA) to start (Gossypium hirsutum) ovule/fiber cultures hindered fiber secondary wall cellulose synthesis compared with natural auxin (indole-3-acetic acid, IAA). In contrast, NAA promoted fiber elongation and ovule weight gain, which resulted in larger ovule/fiber units. To reach these conclusions, fiber and ovule growth parameters were measured and cell wall characteristics were examined microscopically. The differences in fiber from NAA and IAA culture were underpinned by changes in the expression patterns of marker genes for three fiber developmental stages (elongation, the transition stage, and secondary wall deposition), and these gene expression patterns were also analyzed quantitatively in plant-grown fiber. The results demonstrate that secondary wall cellulose synthesis: (1) is under strong transcriptional control that is influenced by auxin; and (2) must be specifically characterized in the cotton ovule/fiber culture system given the many protocol variables employed in different laboratories.

  2. Function of the auxin-responsive gene TaSAUR75 under salt and drought stress

    Directory of Open Access Journals (Sweden)

    Yuan Guo

    2018-04-01

    Full Text Available Small auxin-upregulated RNAs (SAURs are genes regulated by auxin and environmental factors. In this study, we identified a SAUR gene in wheat, TaSAUR75. Under salt stress, TaSAUR75 is downregulated in wheat roots. Subcellular localization revealed that TaSAUR75 was localized in both the cytoplasm and nucleus. Overexpression of TaSAUR75 increased drought and salt tolerance in Arabidopsis. Transgenic lines showed higher root length and survival rate and higher expression of some stress-responsive genes than control plants under salt and drought stress. Less H2O2 accumulated in transgenic lines than in control plants under drought stress. Our findings reveal a positive regulatory role of the auxin-responsive gene TaSAUR75 in plant responses to drought and salt stress and provide a candidate gene for improvement of abiotic stress tolerance in crop breeding.

  3. The diageotropica mutant of tomato lacks high specific activity auxin sites

    International Nuclear Information System (INIS)

    Hicks, G.R.; Lomax, T.L.; Rayle, D.L.

    1989-01-01

    Tomato (Lycopersicum esculentum, Mill) plants homozygous for the single gene diageotropica (dgt) mutation have reduced shoot growth, abnormal vascular tissue, altered leaf morphology, and lack of lateral root branching. These and other morphological and physiological abnormalities suggest that dgt plants are unable to respond to the plant growth hormone auxin (indole-3-acetic acid, IAA). The photoaffinity auxin analogue 3 H-5N 3 -IAA specifically labels a polypeptide doublet of 40 ad 42 kD in membrane preparations from stems of the parental variety VFN8, but not from stems of dgt. In elongation tests, excised dgt roots respond in the same manner to IAA an VFN8 roots. These data suggest that the two polypeptides are part of a physiologically important auxin receptor system which is altered in a tissue-specific manner in the mutant

  4. The chloroindole auxins of pea, strong plant growth hormones or endogenous herbicides

    International Nuclear Information System (INIS)

    Engvild, K.C.

    1994-02-01

    In this work the three theses below are discussed: 1) Identification and quantitative determination of the very strong plant hormone, the auxin 4-chloroindole-3-acetic acid methyl ester, in immature seeds of Pisum, Vicia, Lathyrus, and Lens spp. by incorporation of radioactive 36 Cl, thin layer chromatography, autoradiography, colour reactions, and gas chromatography/mass spectrometry. 2) The strong biological activity of 4-chloroindole-3-acetic acid and its analogues and its ability to induce strong, almost irreversible, ethylene evolution. 3) The possible role of chloroindole auxin in plants, particularly if it might be the hypothetical death hormone, secreted from developing seeds, which induces senescence and kills the mother plant at maturity; if plants generally have several auxin types, growth promoters and endogenous herbicides; and if other chlorine-containing plant hormones occur in developing seeds of other crop species. (au) (7 tabs., 8 ills., 144 refs.)

  5. Expression profiling of AUXIN RESPONSE FACTOR genes during somatic embryogenesis induction in Arabidopsis.

    Science.gov (United States)

    Wójcikowska, Barbara; Gaj, Małgorzata D

    2017-06-01

    Extensive modulation of numerous ARF transcripts in the embryogenic culture of Arabidopsis indicates a substantial role of auxin signaling in the mechanism of somatic embryogenesis induction. Somatic embryogenesis (SE) is induced by auxin in plants and auxin signaling is considered to play a key role in the molecular mechanism that controls the embryogenic transition of plant somatic cells. Accordingly, the expression of AUXIN RESPONSE FACTOR (ARF) genes in embryogenic culture of Arabidopsis was analyzed. The study revealed that 14 of the 22 ARFs were transcribed during SE in Arabidopsis. RT-qPCR analysis indicated that the expression of six ARFs (ARF5, ARF6, ARF8, ARF10, ARF16, and ARF17) was significantly up-regulated, whereas five other genes (ARF1, ARF2, ARF3, ARF11, and ARF18) were substantially down-regulated in the SE-induced explants. The activity of ARFs during SE was also monitored with GFP reporter lines and the ARFs that were expressed in areas of the explants engaged in SE induction were detected. A functional test of ARFs transcribed during SE was performed and the embryogenic potential of the arf mutants and overexpressor lines was evaluated. ARFs with a significantly modulated expression during SE coupled with an impaired embryogenic response of the relevant mutant and/or overexpressor line, including ARF1, ARF2, ARF3, ARF5, ARF6, ARF8, and ARF11 were indicated as possibly being involved in SE induction. The study provides evidence that embryogenic induction strongly depends on ARFs, which are key regulators of the auxin signaling. Some clues on the possible functions of the candidate ARFs, especially ARF5, in the mechanism of embryogenic transition are discussed. The results provide guidelines for further research on the auxin-related functional genomics of SE and the developmental plasticity of somatic cells.

  6. An auxin responsive CLE gene regulates shoot apical meristem development in Arabidopsis

    Directory of Open Access Journals (Sweden)

    Hongyan eGuo

    2015-05-01

    Full Text Available Plant hormone auxin regulates most, if not all aspects of plant growth and development, including lateral root formation, organ pattering, apical dominance and tropisms. Peptide hormones are peptides with hormone activities. Some of the functions of peptide hormones in regulating plant growth and development are similar to that of auxin, however, the relationship between auxin and peptide hormones remains largely unknown. Here we report the identification of OsCLE48, a rice (Oryza sativa CLE (CLAVATA3/ENDOSPERM SURROUNDING REGION gene, as an auxin response gene, and the functional characterization of OsCLE48 in Arabidopsis and rice. OsCLE48 encodes a CLE peptide hormone that is similar to Arabidopsis CLEs. RT-PCR analysis showed that OsCLE48 was induced by exogenously application of IAA (indole-3-acetic acid, a naturally occurred auxin. Expression of integrated OsCLE48p:GUS reporter gene in transgenic Arabidopsis plants was also induced by exogenously IAA treatment. These results indicate that OsCLE48 is an auxin responsive gene. Histochemical staining showed that GUS activity was detected in all the tissue and organs of the OsCLE48p:GUS transgenic Arabidopsis plants. Expression of OsCLE48 under the control of the 35S promoter in Arabidopsis inhibited shoot apical meristem development. Expression of OsCLE48 under the control of the CLV3 native regulatory elements almost completely complemented clv3-2 mutant phenotypes, suggesting that OsCLE48 is functionally similar to CLV3. On the other hand, expression of OsCLE48 under the control of the 35S promoter in Arabidopsis has little, if any effects on root apical meristem development, and transgenic rice plants overexpressing OsCLE48 are morphologically indistinguishable from wild type plants, suggesting that the functions of some CLE peptides may not be fully conserved in Arabidopsis and rice.

  7. Investigating organic molecules responsible of auxin-like activity of humic acid fraction extracted from vermicompost

    Energy Technology Data Exchange (ETDEWEB)

    Scaglia, Barbara, E-mail: barbara.scaglia@unimi.it [Gruppo Ricicla Labs – DiSAA, Università degli Studi di Milano, Via Celoria 2 (Italy); Nunes, Ramom Rachide; Rezende, Maria Olímpia Oliveira [Laboratório de Química Ambiental, Universidade de São Paulo, Instituto de Química de São Carlos, Avenida Trabalhador São Carlense, 400, São Carlos (Brazil); Tambone, Fulvia [Gruppo Ricicla Labs – DiSAA, Università degli Studi di Milano, Via Celoria 2 (Italy); Adani, Fabrizio, E-mail: fabrizio.adani@unimi.it [Gruppo Ricicla Labs – DiSAA, Università degli Studi di Milano, Via Celoria 2 (Italy)

    2016-08-15

    This work studied the auxin-like activity of humic acids (HA) obtained from vermicomposts produced using leather wastes plus cattle dung at different maturation stages (fresh, stable and mature). Bioassays were performed by testing HA concentrations in the range of 100–6000 mg carbon L{sup −1}. {sup 13}C CPMAS-NMR and GC–MS instrumental methods were used to assess the effect of biological processes and starting organic mixtures on HA composition. Not all HAs showed IAA-like activity and in general, IAA-like activity increased with the length of the vermicomposting process. The presence of leather wastes was not necessary to produce the auxin-like activity of HA, since HA extracted from a mix of cattle manure and sawdust, where no leather waste was added, showed IAA-like activity as well. CPMAS {sup 13}CNMR revealed that HAs were similar independently of the mix used and that the humification process involved the increasing concentration of pre-existing alkali soluble fractions in the biomass. GC/MS allowed the identification of the molecules involved in IAA-like effects: carboxylic acids and amino acids. The concentration of active molecules, rather than their simple presence in HA, determined the bio-stimulating effect, and a good linear regression between auxin-like activity and active stimulating molecules concentration was found (R{sup 2} = − 0.85; p < 0.01, n = 6). - Highlights: • Vermicomposting converts waste into organic fertilizer. • Vermicomposts can have biostimulating effect for the presence of hormone-like molecules. • Auxine-like activity was associated to the vermicompost humic acid fraction (HA). • HA carboxylic acids and amino acids, were reported to act as auxin-like molecules. • A linear regression was found between molecules and auxin-like activity.

  8. Gravity/Fluid Correspondence and Its Application on Bulk Gravity with U(1) Gauge Field

    International Nuclear Information System (INIS)

    Hu, Ya-Peng; Zhang, Jian-Hui

    2014-01-01

    As the long wavelength limit of the AdS/CFT correspondence, the gravity/fluid correspondence has been shown to be a useful tool for extracting properties of the fluid on the boundary dual to the gravity in the bulk. In this paper, after briefly reviewing the algorithm of gravity/fluid correspondence, we discuss the results of its application on bulk gravity with a U(1) gauge field. In the presence of a U(1) gauge field, the dual fluid possesses more interesting properties such as its charge current. Furthermore, an external field A_μ"e"x"t could affect the charge current, and the U(1) Chern-Simons term also induces extra structures to the dual current giving anomalous transport coefficients.

  9. Simple Identification of the Neutral Chlorinated Auxin in Pea by Thin Layer Chromatography

    DEFF Research Database (Denmark)

    Engvild, Kjeld Christensen

    1980-01-01

    to small volumes and chromatographed in CHCl3 or CCl4 solvent systems separating the chlorinated auxin from indoleacetonitrile and the methyl or ethyl esters of indoleacetic acid. Colour reaction was carried out with some of the Salkowski FeCl3 sprays of which Ehmann's FeCl3/dimethylaminobenzaldehyde......One of the neutral chlorinated auxins of immature pea seeds was readily identified by thin layer procedures simple enough to serve in student's laboratory courses. 4-Chloroindole-3-acetic acid methyl ester was extracted from 50 g of commercial, frozen peas by either water or acetone, concentrated...

  10. GRAVI-2 space experiment: investigating statoliths displacement and location effects on early stages of gravity perception pathways in lentil roots.

    Science.gov (United States)

    Bizet, François; Eche, Brigitte; Pereda Loth, Veronica; Badel, Eric; Legue, Valerie; Brunel, Nicole; Label, Philippe; Gérard, Joëlle

    2016-07-01

    The plants ability to orient their growth with respect to external stimuli such as gravity is a key factor for survival and acclimation to their environment. Belowground, plant roots modulate their growth towards gravity, allowing soil exploration and uptake of water and nutrients. In roots, gravity sensing cells called statocytes are located in the center of the root cap. Statocytes contain starch-filled plastids denser than the cytoplasm, which sedimentation along the direction of gravity is widely accepted as being involved into early stages of gravity perception (the starch-statolith hypothesis; Sack, 1991). Root gravitropism following statoliths displacement is based on auxin redistribution in the root apex, inducing differential growth between the root upward and downward sides. However at the cell scale, the chain of transduction starting from statoliths displacement and leading to auxin redistribution remains poorly documented. Signaling molecules such as calcium, reactive oxygen species, nitric oxide and inositol 1,4,5-triphosphate are serious candidates previously shown to be involved within minutes before modification of the expression of auxin-related genes (Morita, 2010; Sato et al., 2015). Here, we observe and quantify statoliths displacements and locations at various levels of gravity to investigate two hypothesis: (i) Are contacts between statoliths and the endoplasmic reticulum necessary to induce gravitropism? (ii) Are very low displacements of statoliths sufficient to initiate transduction pathways such as the calcium's one? These questionings have led to an experiment called GRAVI-2 which took place aboard the ISS in 2014. During the experiment, lentil roots were grown in the European modular cultivation system for several hours in microgravity and were then submitted to short high gravity stimulus (5 and 15 minutes at 2 g) before the return to Earth for analyses. Ongoing cytological measurements will reveal the effects of statoliths

  11. Lattice gravity and strings

    International Nuclear Information System (INIS)

    Jevicki, A.; Ninomiya, M.

    1985-01-01

    We are concerned with applications of the simplicial discretization method (Regge calculus) to two-dimensional quantum gravity with emphasis on the physically relevant string model. Beginning with the discretization of gravity and matter we exhibit a discrete version of the conformal trace anomaly. Proceeding to the string problem we show how the direct approach of (finite difference) discretization based on Nambu action corresponds to unsatisfactory treatment of gravitational degrees. Based on the Regge approach we then propose a discretization corresponding to the Polyakov string. In this context we are led to a natural geometric version of the associated Liouville model and two-dimensional gravity. (orig.)

  12. The Future of Gravity

    CERN Multimedia

    CERN. Geneva

    2007-01-01

    Of the four fundamental forces, gravity has been studied the longest, yet gravitational physics is one of the most rapidly developing areas of science today. This talk will give a broad brush survey of the past achievements and future prospects of general relativistic gravitational physics. Gravity is a two frontier science being important on both the very largest and smallest length scales considered in contemporary physics. Recent advances and future prospects will be surveyed in precision tests of general relativity, gravitational waves, black holes, cosmology and quantum gravity. The aim will be an overview of a subject that is becoming increasingly integrated with experiment and other branches of physics.

  13. Scaling in quantum gravity

    Directory of Open Access Journals (Sweden)

    J. Ambjørn

    1995-07-01

    Full Text Available The 2-point function is the natural object in quantum gravity for extracting critical behavior: The exponential falloff of the 2-point function with geodesic distance determines the fractal dimension dH of space-time. The integral of the 2-point function determines the entropy exponent γ, i.e. the fractal structure related to baby universes, while the short distance behavior of the 2-point function connects γ and dH by a quantum gravity version of Fisher's scaling relation. We verify this behavior in the case of 2d gravity by explicit calculation.

  14. Plant-plant interactions influence developmental phase transitions, grain productivity and root system architecture in Arabidopsis via auxin and PFT1/MED25 signalling.

    Science.gov (United States)

    Muñoz-Parra, Edith; Pelagio-Flores, Ramón; Raya-González, Javier; Salmerón-Barrera, Guadalupe; Ruiz-Herrera, León Francisco; Valencia-Cantero, Eduardo; López-Bucio, José

    2017-09-01

    Transcriptional regulation of gene expression influences plant growth, environmental interactions and plant-plant communication. Here, we report that population density is a key factor for plant productivity and a major root architectural determinant in Arabidopsis thaliana. When grown in soil at varied densities from 1 to 32 plants, high number of individuals decreased stem growth and accelerated senescence, which negatively correlated with total plant biomass and seed production at the completion of the life cycle. Root morphogenesis was also a major trait modulated by plant density, because an increasing number of individuals grown in vitro showed repression of primary root growth, lateral root formation and root hair development while affecting auxin-regulated gene expression and the levels of auxin transporters PIN1 and PIN2. We also found that mutation of the Mediator complex subunit PFT1/MED25 renders plants insensitive to high density-modulated root traits. Our results suggest that plant density is critical for phase transitions, productivity and root system architecture and reveal a role of Mediator in self-plant recognition. © 2017 John Wiley & Sons Ltd.

  15. Inhibition of primary roots and stimulation of lateral root development in Arabidopsis thaliana by the rhizobacterium Serratia marcescens 90-166 is through both auxin-dependent and -independent signaling pathways.

    Science.gov (United States)

    Shi, Chun-Lin; Park, Hyo-Bee; Lee, Jong Suk; Ryu, Sangryeol; Ryu, Choong-Min

    2010-03-01

    The rhizobacterium Serratia marcescens strain 90-166 was previously reported to promote plant growth and induce resistance in Arabidopsis thaliana. In this study, the influence of strain 90-166 on root development was studied in vitro. We observed inhibition of primary root elongation, enhanced lateral root emergence, and early emergence of second order lateral roots after inoculation with strain 90-166 at a certain distance from the root. Using the DR5::GUS transgenic A. thaliana plant and an auxin transport inhibitor, N-1-naphthylphthalamic acid, the altered root development was still elicited by strain 90-166, indicating that this was not a result of changes in plant auxin levels. Intriguingly, indole-3-acetic acid, a major auxin chemical, was only identified just above the detection limit in liquid culture of strain 90-166 using liquid chromatography-mass spectrometry. Focusing on bacterial determinants of the root alterations, we found that primary root elongation was inhibited in seedlings treated with cell supernatant (secreted compounds), while lateral root formation was induced in seedlings treated with lysate supernatant (intracellular compounds). Further study revealed that the alteration of root development elicited by strain 90-166 involved the jasmonate, ethylene, and salicylic acid signaling pathways. Collectively, our results suggest that strain 90-166 can contribute to plant root development via multiple signaling pathways.

  16. Gravity-induced differentiations and deficiency in flower formation observed on Columbus experiment WAICO1

    Science.gov (United States)

    Scherer, Günther; Pietrzyk, Peter

    The Arabidopsis Atpla-I-3 knockout mutant (gene nr. At1g61859) is deficient in gravitropism and phototropism indicating a defect in the auxin transport system. The mutant roots form higher numbers of root coils on 45° angle tilted agar. Root tip coils exhibit right-handed spiral pattern of the rhizodermis cells suggesting that torsion of rhizodermis cells could provide a driving force for asymmetrical growth and coiling. WAICO1 was designed to test whether the tendency to for coils by asymmetric tip growth may be provided by torsion of external rhizodermis cells or, alternatively, the asymmetric growth is driven by intrinsic forces in the root. Coil formation is often increased in root agravitropic mutants so that an increase of coils by lack of gravity -and thus absence of gravisensing -was the favoured working hypothesis. Two agar boxes each of wild type and mutant seedlings were grown inside of an outer growth container at 22.5° C in constant light and at a 45° angle tilted, in the 1G rotor and in the microgravity rotor. At first, the samples grown in microgravity could be retrieved from orbit as cooled (4° -8° C) material. They were investigated by microscopy and compared to photographs made in orbit of 1G and µG plants by astronaut. Plants first grown in 1G were retrieved much later (see below). Mutant and wt formed high numbers of coils in microgravity, whereas in 1G none were observed which is comparable to growth experiments on the ground. However, the mutant developed a lower percentage of spiral pattern in the rhizodermal cells despite an even higher number of coils as observed in the wt. The results show that asymmetrical growth of root tips is an intrinsic property and independent of forces that may be exerted by the rhizodermal pattern. Surprisingly, in both wild type and mutant a much higher number of lateral roots were found in µG-grown plants than in plants grown in the 1G-centrifuge after 12 d, suggesting that gravity suppresses lateral root

  17. Changes in auxin level in the course of growth of a sunflower crown-gall suspension culture

    Directory of Open Access Journals (Sweden)

    Zofia Chirek

    2014-01-01

    Full Text Available The auxin level in the cell mass and culture medium was determined by means of the Avena straight caleoptile test in various periods of the suspension culture cycle of the sunflower crown-gall tumour. The investigations were performed in the course of the zero passage (PO and first one (Pl, differing in their time of duration of maximum growth and its intensity. In both passages the intra- and extra-cellular auxin levels reach values of the same order. At the beginning of the maximal growth phase the activity corresponding to IAA in the cells prevails over that of the other auxin-like compounds. This disproportion diminishes with further development of the culture, and with the beginning of the stationary phase the cellular IAA level is lower than that of the remaining auxin-like compounds. The short phase of maximal growth (PO occurs with an auxin level decreasing in the cell mass and increasing in the medium, and towards the end of the cycle these levels become equal. During the long phase of maximal growth (Pl the total amount of auxins in the cells increases and is 2-3 times higher than in the medium, whereas IAA in the cells remains at a constant level. These results suggest that the participation of IAA in the intracellular pool of auxin-like substances is decisive for the mitotic activity of the cells and maintenance of growth in the culture.

  18. Gravity Data for Egypt

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The gravity station data (71 records) were gathered by various governmental organizations (and academia) using a variety of methods. This data base was received in...

  19. New massive gravity

    NARCIS (Netherlands)

    Bergshoeff, Eric A.; Hohm, Olaf; Townsend, Paul K.

    2012-01-01

    We present a brief review of New Massive Gravity, which is a unitary theory of massive gravitons in three dimensions obtained by considering a particular combination of the Einstein-Hilbert and curvature squared terms.

  20. DMA Antarctic Gravity Data

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The gravity station data (65,164 records) were gathered by various governmental organizations (and academia) using a variety of methods. The data base was received...

  1. Gravity Data for Minnesota

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The gravity station data (55,907 records) were gathered by various governmental organizations (and academia) using a variety of methods. This data base was received...

  2. Stability in designer gravity

    International Nuclear Information System (INIS)

    Hertog, Thomas; Hollands, Stefan

    2005-01-01

    We study the stability of designer gravity theories, in which one considers gravity coupled to a tachyonic scalar with anti-de Sitter (AdS) boundary conditions defined by a smooth function W. We construct Hamiltonian generators of the asymptotic symmetries using the covariant phase space method of Wald et al and find that they differ from the spinor charges except when W = 0. The positivity of the spinor charge is used to establish a lower bound on the conserved energy of any solution that satisfies boundary conditions for which W has a global minimum. A large class of designer gravity theories therefore have a stable ground state, which the AdS/CFT correspondence indicates should be the lowest energy soliton. We make progress towards proving this by showing that minimum energy solutions are static. The generalization of our results to designer gravity theories in higher dimensions involving several tachyonic scalars is discussed

  3. Carroll versus Galilei gravity

    Energy Technology Data Exchange (ETDEWEB)

    Bergshoeff, Eric [Centre for Theoretical Physics, University of Groningen,Nijenborgh 4, 9747 AG Groningen (Netherlands); Gomis, Joaquim [Departament de Física Cuàntica i Astrofísica and Institut de Ciències del Cosmos,Universitat de Barcelona,Martí i Franquès 1, E-08028 Barcelona (Spain); Rollier, Blaise [Centre for Theoretical Physics, University of Groningen,Nijenborgh 4, 9747 AG Groningen (Netherlands); Rosseel, Jan [Faculty of Physics, University of Vienna,Boltzmanngasse 5, A-1090 Vienna (Austria); Veldhuis, Tonnis ter [Centre for Theoretical Physics, University of Groningen,Nijenborgh 4, 9747 AG Groningen (Netherlands)

    2017-03-30

    We consider two distinct limits of General Relativity that in contrast to the standard non-relativistic limit can be taken at the level of the Einstein-Hilbert action instead of the equations of motion. One is a non-relativistic limit and leads to a so-called Galilei gravity theory, the other is an ultra-relativistic limit yielding a so-called Carroll gravity theory. We present both gravity theories in a first-order formalism and show that in both cases the equations of motion (i) lead to constraints on the geometry and (ii) are not sufficient to solve for all of the components of the connection fields in terms of the other fields. Using a second-order formalism we show that these independent components serve as Lagrange multipliers for the geometric constraints we found earlier. We point out a few noteworthy differences between Carroll and Galilei gravity and give some examples of matter couplings.

  4. Discrete quantum gravity

    International Nuclear Information System (INIS)

    Williams, Ruth M

    2006-01-01

    A review is given of a number of approaches to discrete quantum gravity, with a restriction to those likely to be relevant in four dimensions. This paper is dedicated to Rafael Sorkin on the occasion of his sixtieth birthday

  5. Carbon monoxide interacts with auxin and nitric oxide to cope with iron deficiency in Arabidopsis

    Science.gov (United States)

    To clarify the roles of CO, NO and auxin in the plant response to iron deficiency and to establish how the signaling molecules interact to enhance Fe acquisition, we conducted physiological, genetic, and molecular analyses that compared the responses of various Arabidopsis mutants, including hy1 (CO...

  6. YUCCA6 over-expression demonstrates auxin function in delaying leaf senescence in Arabidopsis thaliana

    KAUST Repository

    Kim, Jeong Im; Murphy, Angus S.; Baek, Dongwon; Lee, Shin-Woo; Yun, Dae-Jin; Bressan, Ray A.; Narasimhan, Meena L.

    2011-01-01

    The Arabidopsis thaliana YUCCA family of flavin monooxygenase proteins catalyses a rate-limiting step in de novo auxin biosynthesis. A YUCCA6 activation mutant, yuc6-1D, has been shown to contain an elevated free IAA level and to display typical

  7. Possible Interactions between the Biosynthetic Pathways of Indole Glucosinolate and Auxin

    Directory of Open Access Journals (Sweden)

    Siva K. Malka

    2017-12-01

    Full Text Available Glucosinolates (GLS are a group of plant secondary metabolites mainly found in Cruciferous plants, share a core structure consisting of a β-thioglucose moiety and a sulfonated oxime, but differ by a variable side chain derived from one of the several amino acids. These compounds are hydrolyzed upon cell damage by thioglucosidase (myrosinase, and the resulting degradation products are toxic to many pathogens and herbivores. Human beings use these compounds as flavor compounds, anti-carcinogens, and bio-pesticides. GLS metabolism is complexly linked to auxin homeostasis. Indole GLS contributes to auxin biosynthesis via metabolic intermediates indole-3-acetaldoxime (IAOx and indole-3-acetonitrile (IAN. IAOx is proposed to be a metabolic branch point for biosynthesis of indole GLS, IAA, and camalexin. Interruption of metabolic channeling of IAOx into indole GLS leads to high-auxin production in GLS mutants. IAN is also produced as a hydrolyzed product of indole GLS and metabolized to IAA by nitrilases. In this review, we will discuss current knowledge on involvement of GLS in auxin homeostasis.

  8. A Plant Phytosulfokine Peptide Initiates Auxin-Dependent Immunity through Cytosolic Ca2+ Signaling in Tomato.

    Science.gov (United States)

    Zhang, Huan; Hu, Zhangjian; Lei, Cui; Zheng, Chenfei; Wang, Jiao; Shao, Shujun; Li, Xin; Xia, Xiaojian; Cai, Xinzhong; Zhou, Jie; Zhou, Yanhong; Yu, Jingquan; Foyer, Christine H; Shi, Kai

    2018-03-01

    Phytosulfokine (PSK) is a disulfated pentapeptide that is an important signaling molecule. Although it has recently been implicated in plant defenses to pathogen infection, the mechanisms involved remain poorly understood. Using surface plasmon resonance and gene silencing approaches, we showed that the tomato ( Solanum lycopersicum ) PSK receptor PSKR1, rather than PSKR2, functioned as the major PSK receptor in immune responses. Silencing of PSK signaling genes rendered tomato more susceptible to infection by the economically important necrotrophic pathogen Botrytis cinerea Analysis of tomato mutants defective in either defense hormone biosynthesis or signaling demonstrated that PSK-induced immunity required auxin biosynthesis and associated defense pathways. Here, using aequorin-expressing tomato plants, we provide evidence that PSK perception by tomato PSKR1 elevated cytosolic [Ca 2+ ], leading to auxin-dependent immune responses via enhanced binding activity between calmodulins and the auxin biosynthetic YUCs. Thus, our data demonstrate that PSK acts as a damage-associated molecular pattern and is perceived mainly by PSKR1, which increases cytosolic [Ca 2+ ] and activates auxin-mediated pathways that enhance immunity of tomato plants to B. cinerea . © 2018 American Society of Plant Biologists. All rights reserved.

  9. Influence of the origin of stem cutting, season of collection and auxin ...

    African Journals Online (AJOL)

    Influence of the origin of stem cutting, season of collection and auxin application on the vegetative propagation of African Sandalwood ( Osyris lanceolata ) in Tanzania: scientific paper. ... The high nutrition status and low nitrogen content of basal portions may play a role in enhancing their performance. Thus when raising O.

  10. Biochemical activity of auxins in dependence of their structures in Wolffia arrhiza (L. Wimm.

    Directory of Open Access Journals (Sweden)

    Romuald Czerpak

    2011-01-01

    Full Text Available Wolffia arrhiza (L. Wimm. (Lemnaceae as a mixotrophic plant reacts considerably weaker to used auxins with different chemical structures than typical photosynthetic vascular plants and algae especially from Chlorophyta. Among used auxin compounds, the highest stimulative activity on W. arrhiza growth and biochemical parameters which were analysed in biomass, can be attributed to phenylacetic acid (PAA, a somewhat smaller to indole-3-acetic acid (IAA and the smallest to 2-naphthaleneacetic acid (NAA used in optimal concentration of 10-6 M, in comparison with the control culture, devoid of exogenous auxins. The investigated auxins, especially PAA and IAA, were found to have the most powerful stimulative activity (prevailingly between the 10th and the 15th day of cultivation on the content of reducing sugars between 127 and 169%, chlorophyll a and b from 117 to 125%, total carotenoids from 115 to 132% and net photosynthetic rate from 127 to 144% in comparison with the control culture, which was treated as 100% for reference. However, the content of water-soluble proteins as well as nucleic acids (DNA and RNA in the biomass of W. arrhiza was less effectively stimulated, hardly from 110 to 116% when compared to the control culture (100%.

  11. Diurnal variation of cytokinin, auxin and abscisic acid levels in tobacco leaves

    Czech Academy of Sciences Publication Activity Database

    Nováková, Marie; Motyka, Václav; Dobrev, Petre; Malbeck, Jiří; Gaudinová, Alena

    2005-01-01

    Roč. 56, č. 421 (2005), s. 2877-2883 ISSN 0022-0957 R&D Projects: GA ČR GA206/03/0369; GA MŠk LN00A081 Institutional research plan: CEZ:AV0Z50380511 Keywords : abscisic acid * auxin * cytokinin Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 3.336, year: 2005

  12. Evolution and structural diversification of PILS putative auxin carriers in plants

    Czech Academy of Sciences Publication Activity Database

    Feraru, E.; Vosolsobě, S.; Feraru, M.; Petrášek, Jan; Kleine-Vehn, J.

    2012-01-01

    Roč. 3, č. 227 (2012) ISSN 1664-462X R&D Projects: GA ČR(CZ) GAP305/11/2476 Institutional support: RVO:61389030 Keywords : PILS proteins * auxin * evolution Subject RIV: EB - Genetics ; Molecular Biology http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3470039/pdf/fpls-03-00227.pdf

  13. Changes in cytokinin and auxin concentrations in seaweed concentrates when stored at an elevated temperature

    Czech Academy of Sciences Publication Activity Database

    Stirk, W. A.; Arthur, G. D.; Lourens, A. F.; Novák, Ondřej; Strnad, Miroslav; van Staden, J.

    2004-01-01

    Roč. 16, č. 1 (2004), s. 31-39 ISSN 0022-3646 R&D Projects: GA ČR GA522/03/0323 Institutional research plan: CEZ:AV0Z5038910 Keywords : accelerated storage * auxins * cytokinins Subject RIV: EF - Botanics Impact factor: 2.490, year: 2004

  14. Endogenous cytokinins, auxins, and abscisic acid in red algae from Brazil

    Czech Academy of Sciences Publication Activity Database

    Yokoya, N. S.; Stirk, W. A.; van Staden, J.; Novák, Ondřej; Turečková, Veronika; Pěnčík, Aleš; Strnad, Miroslav

    2010-01-01

    Roč. 46, č. 6 (2010), s. 1198-1205 ISSN 0022-3646 R&D Projects: GA ČR GA301/08/1649 Institutional research plan: CEZ:AV0Z50380511 Keywords : ENDOGENOUS * CYTOKININS * AUXINS * ABSCISIC ACID * RED * ALGAE * BRAZIL Subject RIV: EF - Botanics Impact factor: 2.239, year: 2010

  15. 7-Rhamnosylated Flavonols Modulate Homeostasis of the Plant Hormone Auxin and Affect Plant Development

    Czech Academy of Sciences Publication Activity Database

    Kuhn, B.M.; Errafi, S.; Bucher, R.; Dobrev, Petre; Geisler, M.; Bigler, L.; Zažímalová, Eva; Ringli, Ch.

    2016-01-01

    Roč. 291, č. 10 (2016), s. 5385-5395 ISSN 0021-9258 R&D Projects: GA ČR(CZ) GAP305/11/0797 Institutional support: RVO:61389030 Keywords : Arabidopsis thaliana * auxin * flavonoid Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 4.125, year: 2016

  16. Identification and Expression Profiling of the Auxin Response Factors in Dendrobium officinale under Abiotic Stresses.

    Science.gov (United States)

    Chen, Zhehao; Yuan, Ye; Fu, Di; Shen, Chenjia; Yang, Yanjun

    2017-05-04

    Auxin response factor (ARF) proteins play roles in plant responses to diverse environmental stresses by binding specifically to the auxin response element in the promoters of target genes. Using our latest public Dendrobium transcriptomes, a comprehensive characterization and analysis of 14 DnARF genes were performed. Three selected DnARFs , including DnARF1 , DnARF4 , and DnARF6 , were confirmed to be nuclear proteins according to their transient expression in epidermal cells of Nicotiana benthamiana leaves. Furthermore, the transcription activation abilities of DnARF1 , DnARF4 , and DnARF6 were tested in a yeast system. Our data showed that DnARF6 is a transcriptional activator in Dendrobium officinale . To uncover the basic information of DnARF gene responses to abiotic stresses, we analyzed their expression patterns under various hormones and abiotic treatments. Based on our data, several hormones and significant stress responsive DnARF genes have been identified. Since auxin and ARF genes have been identified in many plant species, our data is imperative to reveal the function of ARF mediated auxin signaling in the adaptation to the challenging Dendrobium environment.

  17. Endogenous auxin regulates the sensitivity of Dendrobium (cv. Miss Teen) flower pedicel abscission to ethylene

    NARCIS (Netherlands)

    Rungruchkanont, K.; Ketsa, S.; Chatchawankanphanich, O.; Doorn, van W.G.

    2007-01-01

    Dendrobium flower buds and flowers have an abscission zone at the base of the pedicel (flower stalk). Ethylene treatment of cv. Miss Teen inflorescences induced high rates of abscission in flower buds but did not affect abscission once the flowers had opened. It is not known if auxin is a regulator

  18. Auxin is required for pollination-induced ovary growth in Dendrobium orchids

    NARCIS (Netherlands)

    Ketsa, S.; Wisutiamonkul, A.; Doorn, van W.G.

    2006-01-01

    In Dendrobium and other orchids the ovule becomes mature long after pollination, whereas the ovary starts growing within two days of pollination. The signalling pathway that induces rapid ovary growth after pollination has remained elusive. We placed the auxin antagonist ¿-(p-chlorophenoxy)

  19. Cytokinin, auxin and physiological polarity in the aquatic carnivorous plants Aldrovanda vesiculosa and Utricularia australis

    Czech Academy of Sciences Publication Activity Database

    Šimura, Jan; Spíchal, Lukáš; Adamec, Lubomír; Pěnčík, A.; Rolčík, Jakub; Novák, Ondřej; Strnad, Miroslav

    2016-01-01

    Roč. 117, č. 6 (2016), s. 1037-1044 ISSN 0305-7364 R&D Projects: GA MŠk(CZ) LO1204; GA MŠk LK21306 Institutional support: RVO:61389030 ; RVO:67985939 Keywords : Auxin * Aldrovanda vesiculosa * cytokinin Subject RIV: EF - Botanics Impact factor: 4.041, year: 2016

  20. Ultra-rapid auxin metabolite profiling for high-throughput mutant screening in Arabidopsis

    Czech Academy of Sciences Publication Activity Database

    Pěnčík, Aleš; Casanova-Sáez, R.; Pilařová, V.; Žukauskaitė, Asta; Pinto, R.; Micol, J.L.; Ljung, K.; Novák, Ondřej

    2018-01-01

    Roč. 69, č. 10 (2018), s. 2569-2579 ISSN 0022-0957 R&D Projects: GA ČR(CZ) GJ17-21581Y Institutional support: RVO:61389030 Keywords : Arabidopsis thaliana * auxin * metabolite profiling * multivariate data analysis * mutant * screening Subject RIV: ED - Physiology OBOR OECD: Plant sciences, botany Impact factor: 5.830, year: 2016

  1. The earth's shape and gravity

    CERN Document Server

    Garland, G D; Wilson, J T

    2013-01-01

    The Earth's Shape and Gravity focuses on the progress of the use of geophysical methods in investigating the interior of the earth and its shape. The publication first offers information on gravity, geophysics, geodesy, and geology and gravity measurements. Discussions focus on gravity measurements and reductions, potential and equipotential surfaces, absolute and relative measurements, and gravity networks. The text then elaborates on the shape of the sea-level surface and reduction of gravity observations. The text takes a look at gravity anomalies and structures in the earth's crust; interp

  2. Streaming gravity mode instability

    International Nuclear Information System (INIS)

    Wang Shui.

    1989-05-01

    In this paper, we study the stability of a current sheet with a sheared flow in a gravitational field which is perpendicular to the magnetic field and plasma flow. This mixing mode caused by a combined role of the sheared flow and gravity is named the streaming gravity mode instability. The conditions of this mode instability are discussed for an ideal four-layer model in the incompressible limit. (author). 5 refs

  3. On higher derivative gravity

    International Nuclear Information System (INIS)

    Accioly, A.J.

    1987-01-01

    A possible classical route conducting towards a general relativity theory with higher-derivatives starting, in a sense, from first principles, is analysed. A completely causal vacuum solution with the symmetries of the Goedel universe is obtained in the framework of this higher-derivative gravity. This very peculiar and rare result is the first known vcuum solution of the fourth-order gravity theory that is not a solution of the corresponding Einstein's equations.(Author) [pt

  4. What Is Gravity?

    Science.gov (United States)

    Nelson, George

    2004-01-01

    Gravity is the name given to the phenomenon that any two masses, like you and the Earth, attract each other. One pulls on the Earth and the Earth pulls on one the same amount. And one does not have to be touching. Gravity acts over vast distances, like the 150 million kilometers (93 million miles) between the Earth and the Sun or the billions of…

  5. Automated borehole gravity meter system

    International Nuclear Information System (INIS)

    Lautzenhiser, Th.V.; Wirtz, J.D.

    1984-01-01

    An automated borehole gravity meter system for measuring gravity within a wellbore. The gravity meter includes leveling devices for leveling the borehole gravity meter, displacement devices for applying forces to a gravity sensing device within the gravity meter to bring the gravity sensing device to a predetermined or null position. Electronic sensing and control devices are provided for (i) activating the displacement devices, (ii) sensing the forces applied to the gravity sensing device, (iii) electronically converting the values of the forces into a representation of the gravity at the location in the wellbore, and (iv) outputting such representation. The system further includes electronic control devices with the capability of correcting the representation of gravity for tidal effects, as well as, calculating and outputting the formation bulk density and/or porosity

  6. Complete disintegration of the microtubular cytoskeleton precedes its auxin-mediated reconstruction in postmitotic maize root cells

    Science.gov (United States)

    Baluska, F.; Barlow, P. W.; Volkmann, D.

    1996-01-01

    The inhibitory action of 0.1 microM auxin (IAA) on maize root growth was closely associated with a rapid and complete disintegration of the microtubular (MT) cytoskeleton, as visualized by indirect immunofluorescence of tubulin, throughout the growth region. After 30 min of this treatment, only fluorescent spots were present in root cells, accumulating either around nuclei or along cell walls. Six h later, in addition to some background fluorescence, dense but partially oriented oblique or longitudinal arrays of cortical MTs (CMTs) were found in most growing cells of the root apex. After 24 h of treatment, maize roots had adapted to the auxin, as inferred from the slowly recovering elongation rate and from the reassembly of a dense and well-ordered MT cytoskeleton which showed only slight deviations from that of the control root cells. Taxol pretreatment (100 microM, 24 h) prevented not only the rapid auxin-mediated disintegration of the MT cytoskeleton but also a reorientation of the CMT arrays, from transversal to longitudinal. The only tissue to show MTs in their cells throughout the auxin treatment was the epidermis. Significant resistance of transverse CMT arrays in these cells towards auxin was confirmed using a higher auxin concentration (100 microM, 24 h). The latter auxin dose also revealed inter-tissue-specific responses to auxin: outer cortical cell files reoriented their CMTs from the transversal to longitudinal orientation, whereas inner cortical cell files lost their MTs. This high auxin-mediated response, associated with the swelling of root apices, was abolished with the pretreatment of maize root with taxol.

  7. Molecular and biochemical evidence for the involvement of calcium/calmodulin in auxin action

    Science.gov (United States)

    Yang, T.; Poovaiah, B. W.

    2000-01-01

    The use of (35)S-labeled calmodulin (CaM) to screen a corn root cDNA expression library has led to the isolation of a CaM-binding protein, encoded by a cDNA with sequence similarity to small auxin up RNAs (SAURs), a class of early auxin-responsive genes. The cDNA designated as ZmSAUR1 (Zea mays SAURs) was expressed in Escherichia coli, and the recombinant protein was purified by CaM affinity chromatography. The CaM binding assay revealed that the recombinant protein binds to CaM in a calcium-dependent manner. Deletion analysis revealed that the CaM binding site was located at the NH(2)-terminal domain. A synthetic peptide of amino acids 20-45, corresponding to the potential CaM binding region, was used for calcium-dependent mobility shift assays. The synthetic peptide formed a stable complex with CaM only in the presence of calcium. The CaM affinity assay indicated that ZmSAUR1 binds to CaM with high affinity (K(d) approximately 15 nM) in a calcium-dependent manner. Comparison of the NH(2)-terminal portions of all of the characterized SAURs revealed that they all contain a stretch of the basic alpha-amphiphilic helix similar to the CaM binding region of ZmSAUR1. CaM binds to the two synthetic peptides from the NH(2)-terminal regions of Arabidopsis SAUR-AC1 and soybean 10A5, suggesting that this is a general phenomenon for all SAURs. Northern analysis was carried out using the total RNA isolated from auxin-treated corn coleoptile segments. ZmSAUR1 gene expression began within 10 min, increased rapidly between 10 and 60 min, and peaked around 60 min after 10 microM alpha-naphthaleneacetic acid treatment. These results indicate that ZmSAUR1 is an early auxin-responsive gene. The CaM antagonist N-(6-aminohexyl)5-chloro-1-naphthalenesulfonamide hydrochloride inhibited the auxin-induced cell elongation but not the auxin-induced expression of ZmSAUR1. This suggests that calcium/CaM do not regulate ZmSAUR1 at the transcriptional level. CaM binding to ZmSAUR1 in a calcium

  8. Gravity Before Einstein and Schwinger Before Gravity

    Science.gov (United States)

    Trimble, Virginia L.

    2012-05-01

    Julian Schwinger was a child prodigy, and Albert Einstein distinctly not; Schwinger had something like 73 graduate students, and Einstein very few. But both thought gravity was important. They were not, of course, the first, nor is the disagreement on how one should think about gravity that is being highlighted here the first such dispute. The talk will explore, first, several of the earlier dichotomies: was gravity capable of action at a distance (Newton), or was a transmitting ether required (many others). Did it act on everything or only on solids (an odd idea of the Herschels that fed into their ideas of solar structure and sunspots)? Did gravitational information require time for its transmission? Is the exponent of r precisely 2, or 2 plus a smidgeon (a suggestion by Simon Newcomb among others)? And so forth. Second, I will try to say something about Scwinger's lesser known early work and how it might have prefigured his "source theory," beginning with "On the Interaction of Several Electrons (the unpublished, 1934 "zeroth paper," whose title somewhat reminds one of "On the Dynamics of an Asteroid," through his days at Berkeley with Oppenheimer, Gerjuoy, and others, to his application of ideas from nuclear physics to radar and of radar engineering techniques to problems in nuclear physics. And folks who think good jobs are difficult to come by now might want to contemplate the couple of years Schwinger spent teaching elementary physics at Purdue before moving on to the MIT Rad Lab for war work.

  9. Extended Theories of Gravity

    International Nuclear Information System (INIS)

    Capozziello, Salvatore; De Laurentis, Mariafelicia

    2011-01-01

    Extended Theories of Gravity can be considered as a new paradigm to cure shortcomings of General Relativity at infrared and ultraviolet scales. They are an approach that, by preserving the undoubtedly positive results of Einstein’s theory, is aimed to address conceptual and experimental problems recently emerged in astrophysics, cosmology and High Energy Physics. In particular, the goal is to encompass, in a self-consistent scheme, problems like inflation, dark energy, dark matter, large scale structure and, first of all, to give at least an effective description of Quantum Gravity. We review the basic principles that any gravitational theory has to follow. The geometrical interpretation is discussed in a broad perspective in order to highlight the basic assumptions of General Relativity and its possible extensions in the general framework of gauge theories. Principles of such modifications are presented, focusing on specific classes of theories like f(R)-gravity and scalar–tensor gravity in the metric and Palatini approaches. The special role of torsion is also discussed. The conceptual features of these theories are fully explored and attention is paid to the issues of dynamical and conformal equivalence between them considering also the initial value problem. A number of viability criteria are presented considering the post-Newtonian and the post-Minkowskian limits. In particular, we discuss the problems of neutrino oscillations and gravitational waves in extended gravity. Finally, future perspectives of extended gravity are considered with possibility to go beyond a trial and error approach.

  10. The Acid Growth Theory of auxin-induced cell elongation is alive and well

    Science.gov (United States)

    Rayle, D. L.; Cleland, R. E.

    1992-01-01

    Plant cells elongate irreversibly only when load-bearing bonds in the walls are cleaved. Auxin causes the elongation of stem and coleoptile cells by promoting wall loosening via cleavage of these bonds. This process may be coupled with the intercalation of new cell wall polymers. Because the primary site of auxin action appears to be the plasma membrane or some intracellular site, and wall loosening is extracellular, there must be communication between the protoplast and the wall. Some "wall-loosening factor" must be exported from auxin-impacted cells, which sets into motion the wall loosening events. About 20 years ago, it was suggested that the wall-loosening factor is hydrogen ions. This idea and subsequent supporting data gave rise to the Acid Growth Theory, which states that when exposed to auxin, susceptible cells excrete protons into the wall (apoplast) at an enhanced rate, resulting in a decrease in apoplastic pH. The lowered wall pH then activates wall-loosening processes, the precise nature of which is unknown. Because exogenous acid causes a transient (1-4 h) increase in growth rate, auxin must also mediate events in addition to wall acidification for growth to continue for an extended period of time. These events may include osmoregulation, cell wall synthesis, and maintenance of the capacity of walls to undergo acid-induced wall loosening. At present, we do not know if these phenomena are tightly coupled to wall acidification or if they are the products of multiple independent signal transduction pathways.

  11. Auxins differentially regulate root system architecture and cell cycle protein levels in maize seedlings.

    Science.gov (United States)

    Martínez-de la Cruz, Enrique; García-Ramírez, Elpidio; Vázquez-Ramos, Jorge M; Reyes de la Cruz, Homero; López-Bucio, José

    2015-03-15

    Maize (Zea mays) root system architecture has a complex organization, with adventitious and lateral roots determining its overall absorptive capacity. To generate basic information about the earlier stages of root development, we compared the post-embryonic growth of maize seedlings germinated in water-embedded cotton beds with that of plants obtained from embryonic axes cultivated in liquid medium. In addition, the effect of four different auxins, namely indole-3-acetic acid (IAA), 1-naphthaleneacetic acid (NAA), indole-3-butyric acid (IBA) and 2,4-dichlorophenoxyacetic acid (2,4-D) on root architecture and levels of the heat shock protein HSP101 and the cell cycle proteins CKS1, CYCA1 and CDKA1 were analyzed. Our data show that during the first days after germination, maize seedlings develop several root types with a simultaneous and/or continuous growth. The post-embryonic root development started with the formation of the primary root (PR) and seminal scutellar roots (SSR) and then continued with the formation of adventitious crown roots (CR), brace roots (BR) and lateral roots (LR). Auxins affected root architecture in a dose-response fashion; whereas NAA and IBA mostly stimulated crown root formation, 2,4-D showed a strong repressing effect on growth. The levels of HSP101, CKS1, CYCA1 and CDKA in root and leaf tissues were differentially affected by auxins and interestingly, HSP101 registered an auxin-inducible and root specific expression pattern. Taken together, our results show the timing of early branching patterns of maize and indicate that auxins regulate root development likely through modulation of the HSP101 and cell cycle proteins. Copyright © 2014 Elsevier GmbH. All rights reserved.

  12. Mars geodesy, rotation and gravity

    International Nuclear Information System (INIS)

    Rosenblatt, Pascal; Dehant, Veronique

    2010-01-01

    This review provides explanations of how geodesy, rotation and gravity can be addressed using radioscience data of an orbiter around a planet or of the lander on its surface. The planet Mars is the center of the discussion. The information one can get from orbitography and radioscience in general concerns the global static gravitational field, the time variation of the gravitational field induced by mass exchange between the atmosphere and the ice caps, the time variation of the gravitational field induced by the tides, the secular changes in the spacecraft's orbit induced by the little moons of Mars named Phobos and Deimos, the gravity induced by particular targets, the Martian ephemerides, and Mars' rotation and orientation. The paper addresses as well the determination of the geophysical parameters of Mars and, in particular, the state of Mars' core and its size, which is important for understanding the planet's evolution. Indeed, the state and dimension of the core determined from the moment of inertia and nutation depend in turn on the percentage of light elements in the core as well as on the core temperature, which is related to heat transport in the mantle. For example, the radius of the core has implications for possible mantle convection scenarios and, in particular, for the presence of a perovskite phase transition at the bottom of the mantle. This is also important for our understanding of the large volcanic province Tharsis on the surface of Mars. (invited reviews)

  13. Knocking down expression of the auxin-amidohydrolase IAR3 alters defense responses in Solanaceae family plants

    Czech Academy of Sciences Publication Activity Database

    D'Ippolito, S.; Vaňková, Radomíra; Joosten, M.H.A.J.; Casalongue, C.A.; Fiol, D.F.

    2016-01-01

    Roč. 253, DEC (2016), s. 31-39 ISSN 0168-9452 Institutional support: RVO:61389030 Keywords : Auxin * Biotic stress * Cladosporium fulvum Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 3.437, year: 2016

  14. Stimulatory effect of auxins and cytokinins on carotenes, with differential effects on xanthophylls in the green alga Chlorella pyrenoidosa Chick.

    Directory of Open Access Journals (Sweden)

    Romuald Czerpak

    2014-01-01

    Full Text Available Research concerning the influence of auxins and cytokinins on the content of carotenoids in Chlorella pyrenoidosa (Chlorophyceae has been conducted. The strongest stimulating effect on carotenoids content in Ch. pyrenoidosa biomass was exerted by cytokinins (N-6-benzylaminopurine and N-6-furfurylaminopurine and allantoin, weaker by auxins and their chemical analogues, and the weakest by tryptamine and 2,4-dichlorophenoxyacetic acid compared to the control. Under the influence of cytokinins the content of α- and β-carotene have been stimulated several times stronger than by auxins, and especially 2,4- dichlorophenoxyacetic acid and tryptamine. However, oxygen-rich xanthophylls content was most strongly reduced by cytokinins (60-70% in relation to the control in the 20 day lasting of Ch. pyrenoidosa cultivation, similarly to auxins: 1-naphthaleneacetic acid, indole-3-butyric acid, 2,4- dichlorophenoxyacetic acid.

  15. Predicting specific gravity and viscosity of biodiesel fuels

    OpenAIRE

    Tesfa, Belachew; Mishra, Rakesh; Gu, Fengshou; Ball, Andrew

    2009-01-01

    Biodiesel is a promising non-toxic and biodegradable alternative fuel in transport sector. Of all the biodiesel properties, specific gravity and viscosity are the most significant for the effects they have on the utilization of biodiesel fuels in unmodified engines. This paper presents models, which have been derived from experimental data, for predicting the specific gravity and dynamic viscosity of biodiesel at various temperatures and fractions. In addition a model has also been developed ...

  16. Quantum Gravity Experiments

    Directory of Open Access Journals (Sweden)

    Cahill R. T.

    2015-10-01

    Full Text Available A new quantum gravity experiment is reported with the data confirming the generali- sation of the Schrödinger equation to include the interaction of the wave function with dynamical space. Dynamical space turbulence, via this interaction process, raises and lowers the energy of the electron wave function, which is detected by observing conse- quent variations in the electron quantum barrier tunnelling rate in reverse-biased Zener diodes. This process has previously been reported and enabled the measurement of the speed of the dynamical space flow, which is consistent with numerous other detection experiments. The interaction process is dependent on the angle between the dynamical space flow velocity and the direction of the electron flow in the diode, and this depen- dence is experimentally demonstrated. This interaction process explains gravity as an emergent quantum process, so unifying quantum phenomena and gravity. Gravitational waves are easily detected.

  17. Gravity and strings

    CERN Document Server

    Ortín, Tomás

    2015-01-01

    Self-contained and comprehensive, this definitive new edition of Gravity and Strings is a unique resource for graduate students and researchers in theoretical physics. From basic differential geometry through to the construction and study of black-hole and black-brane solutions in quantum gravity - via all the intermediate stages - this book provides a complete overview of the intersection of gravity, supergravity, and superstrings. Now fully revised, this second edition covers an extensive array of topics, including new material on non-linear electric-magnetic duality, the electric-tensor formalism, matter-coupled supergravity, supersymmetric solutions, the geometries of scalar manifolds appearing in 4- and 5-dimensional supergravities, and much more. Covering reviews of important solutions and numerous solution-generating techniques, and accompanied by an exhaustive index and bibliography, this is an exceptional reference work.

  18. Solitons in Newtonian gravity

    International Nuclear Information System (INIS)

    Goetz, G.

    1988-01-01

    It is shown that the plane-wave solutions for the equations governing the motion of a self-gravitating isothermal fluid in Newtonian hydrodynamics are generated by a sine-Gordon equation which is solvable by an 'inverse scattering' transformation. A transformation procedure is outlined by means of which one can construct solutions of the gravity system out of a pair of solutions of the sine-Gordon equation, which are interrelated via an auto-Baecklund transformation. In general the solutions to the gravity system are obtained in a parametric representation in terms of characteristic coordinates. All solutions of the gravity system generated by the one-and two-soliton solutions of the sine-Gordon equation can be constructed explicitly. These might provide models for the evolution of flat structures as they are predicted to arise in the process of galaxy formation. (author)

  19. Stochastic quantum gravity

    International Nuclear Information System (INIS)

    Rumpf, H.

    1987-01-01

    We begin with a naive application of the Parisi-Wu scheme to linearized gravity. This will lead into trouble as one peculiarity of the full theory, the indefiniteness of the Euclidean action, shows up already at this level. After discussing some proposals to overcome this problem, Minkowski space stochastic quantization will be introduced. This will still not result in an acceptable quantum theory of linearized gravity, as the Feynman propagator turns out to be non-causal. This defect will be remedied only after a careful analysis of general covariance in stochastic quantization has been performed. The analysis requires the notion of a metric on the manifold of metrics, and a natural candidate for this is singled out. With this a consistent stochastic quantization of Einstein gravity becomes possible. It is even possible, at least perturbatively, to return to the Euclidean regime. 25 refs. (Author)

  20. No slip gravity

    Science.gov (United States)

    Linder, Eric V.

    2018-03-01

    A subclass of the Horndeski modified gravity theory we call No Slip Gravity has particularly interesting properties: 1) a speed of gravitational wave propagation equal to the speed of light, 2) equality between the effective gravitational coupling strengths to matter and light, Gmatter and Glight, hence no slip between the metric potentials, yet difference from Newton's constant, and 3) suppressed growth to give better agreement with galaxy clustering observations. We explore the characteristics and implications of this theory, and project observational constraints. We also give a simple expression for the ratio of the gravitational wave standard siren distance to the photon standard candle distance, in this theory and others, and enable a direct comparison of modified gravity in structure growth and in gravitational waves, an important crosscheck.

  1. The quantization of gravity

    CERN Document Server

    Gerhardt, Claus

    2018-01-01

    A unified quantum theory incorporating the four fundamental forces of nature is one of the major open problems in physics. The Standard Model combines electro-magnetism, the strong force and the weak force, but ignores gravity. The quantization of gravity is therefore a necessary first step to achieve a unified quantum theory. In this monograph a canonical quantization of gravity has been achieved by quantizing a geometric evolution equation resulting in a gravitational wave equation in a globally hyperbolic spacetime. Applying the technique of separation of variables we obtain eigenvalue problems for temporal and spatial self-adjoint operators where the temporal operator has a pure point spectrum with eigenvalues $\\lambda_i$ and related eigenfunctions, while, for the spatial operator, it is possible to find corresponding eigendistributions for each of the eigenvalues $\\lambda_i$, if the Cauchy hypersurface is asymptotically Euclidean or if the quantized spacetime is a black hole with a negative cosmological ...

  2. Interactions between ethylene and auxin are crucial to the control of grape (Vitis vinifera L.) berry ripening.

    Science.gov (United States)

    Böttcher, Christine; Burbidge, Crista A; Boss, Paul K; Davies, Christopher

    2013-12-23

    Fruit development is controlled by plant hormones, but the role of hormone interactions during fruit ripening is poorly understood. Interactions between ethylene and the auxin indole-3-acetic acid (IAA) are likely to be crucial during the ripening process, since both hormones have been shown to be implicated in the control of ripening in a range of different fruit species. Grapevine (Vitis vinifera L.) homologues of the TRYPTOPHAN AMINOTRANSFERASE RELATED (TAR) and YUCCA families, functioning in the only characterized pathway of auxin biosynthesis, were identified and the expression of several TAR genes was shown to be induced by the pre-ripening application of the ethylene-releasing compound Ethrel. The induction of TAR expression was accompanied by increased IAA and IAA-Asp concentrations, indicative of an upregulation of auxin biosynthesis and conjugation. Exposure of ex planta, pre-ripening berries to the ethylene biosynthesis inhibitor aminoethoxyvinylglycine resulted in decreased IAA and IAA-Asp concentrations. The delayed initiation of ripening observed in Ethrel-treated berries might therefore represent an indirect ethylene effect mediated by increased auxin concentrations. During berry development, the expression of three TAR genes and one YUCCA gene was upregulated at the time of ripening initiation and/or during ripening. This increase in auxin biosynthesis gene expression was preceded by high expression levels of the ethylene biosynthesis genes 1-aminocyclopropane-1-carboxylate synthase and 1-aminocyclopropane-1-carboxylate oxidase. In grape berries, members of both gene families involved in the two-step pathway of auxin biosynthesis are expressed, suggesting that IAA is produced through the combined action of TAR and YUCCA proteins in developing berries. The induction of TAR expression by Ethrel applications and the developmental expression patterns of auxin and ethylene biosynthesis genes indicate that elevated concentrations of ethylene prior to the

  3. [Identification of an auxin response factor-like protein cDNA from mango cotyledon section].

    Science.gov (United States)

    Xiao, Jie-Ning; Huang, Xue-Lin; Huang, Xia; Li, Xiao-Ju

    2004-01-01

    Auxin-responsive elements (AuxRE) interact with a new class of plant-specific transcription factors, auxin response factors (ARFs). Some of ARFs have been shown to repress or activate expression of genes with an AuxRE promotor element. In Arabidopsis, ARFs play important roles in early embryo development and vascular strand formation (ARF5), floral patterning (ARF3) and photo- and gravitropic responses (ARF7). Two cut surfaces (distal and proximal) of mango (Mangifera indica L. var. Zi-Hua) cotyledon showed different patterns of adventitious root formation, with only the proximal cut surface, but not the distal one, could be induced to form the roots. Thus, the mango cotyledon is a good system for studying adventitious root formation. A cDNA fragment homologous to the Arabidopsis auxin response factor-like protein and relates to adventitious root formation from the cut sections were isolated using suppressive subtractive hybridization (SSH). Two cDNA clones, designated as MiARF1 (mango auxin response factor 1 gene, GenBank accession number AY255705) and MiARF2 (mango auxin response factor 2 gene, GenBank accession number is AY300808), were identified by 3'RACE. MiARF1, 3 272bp long, contains an open reading frame (ORF) of 2 523bp, 5'UTR of 285bp and 3'UTR of 464bp, MiARF2, 1 474bp long, contains an ORF of 981bp, 5' UTR of 285bp and 3'UTR of 208bp. The deduced MiARF1 and MiARF2 are homologues of auxin response factor (ARF) family of transcriptional regulators, and show high similarity to ARF of Arabidopsis in conserved domains. The motifs of MiARF1 EL-WHACAGPL in DBD (DNA binding domain) and GDDPW in IV domain are identical to that of ARF-like protein of Arabidopsis. MiARF2 is identical to MiARF1 in a large part of DBD, but lacks a carboxyl-terminal domain containing conserved motifs III and IV. Virtual Northern blot showed that the expression of MiARF2 was high in rooting tissue of cultured cotyledon sections but low in non-rooting tissue, and the MiARF1 was

  4. Airborne Gravity: NGS' Gravity Data for EN08 (2013)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Airborne gravity data for New York, Vermont, New Hampshire, Massachusettes, Maine, and Canada collected in 2013 over 1 survey. This data set is part of the Gravity...

  5. Airborne Gravity: NGS' Gravity Data for TS01 (2014)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Airborne gravity data for Puerto Rico and the Virgin Islands collected in 2009 over 1 survey. This data set is part of the Gravity for the Re-definition of the...

  6. Airborne Gravity: NGS' Gravity Data for AN08 (2016)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Airborne gravity data for Alaska collected in 2016 over one survey. This data set is part of the Gravity for the Re-definition of the American Vertical Datum...

  7. Airborne Gravity: NGS' Gravity Data for CN02 (2013 & 2014)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Airborne gravity data for Nebraska collected in 2013 & 2014 over 3 surveys. This data set is part of the Gravity for the Re-definition of the American Vertical...

  8. Airborne Gravity: NGS' Gravity Data for EN01 (2011)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Airborne gravity data for New York, Canada, and Lake Ontario collected in 2011 over 1 survey. This data set is part of the Gravity for the Re-definition of the...

  9. Airborne Gravity: NGS' Gravity Data for AN03 (2010)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Airborne gravity data for Alaska collected in 2010 and 2012 over 2 surveys. This data set is part of the Gravity for the Re-definition of the American Vertical Datum...

  10. Airborne Gravity: NGS' Gravity Data for EN06 (2016)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Airborne gravity data for Maine, Canada, and the Atlantic Ocean collected in 2012 over 2 surveys. This data set is part of the Gravity for the Re-definition of the...

  11. Airborne Gravity: NGS' Gravity Data for ES01 (2013)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Airborne gravity data for Florida, the Bahamas, and the Atlantic Ocean collected in 2013 over 1 survey. This data set is part of the Gravity for the Re-definition of...

  12. A Combined Gravity Compensation Method for INS Using the Simplified Gravity Model and Gravity Database.

    Science.gov (United States)

    Zhou, Xiao; Yang, Gongliu; Wang, Jing; Wen, Zeyang

    2018-05-14

    In recent decades, gravity compensation has become an important way to reduce the position error of an inertial navigation system (INS), especially for a high-precision INS, because of the extensive application of high precision inertial sensors (accelerometers and gyros). This paper first deducts the INS's solution error considering gravity disturbance and simulates the results. Meanwhile, this paper proposes a combined gravity compensation method using a simplified gravity model and gravity database. This new combined method consists of two steps all together. Step 1 subtracts the normal gravity using a simplified gravity model. Step 2 first obtains the gravity disturbance on the trajectory of the carrier with the help of ELM training based on the measured gravity data (provided by Institute of Geodesy and Geophysics; Chinese Academy of sciences), and then compensates it into the error equations of the INS, considering the gravity disturbance, to further improve the navigation accuracy. The effectiveness and feasibility of this new gravity compensation method for the INS are verified through vehicle tests in two different regions; one is in flat terrain with mild gravity variation and the other is in complex terrain with fierce gravity variation. During 2 h vehicle tests, the positioning accuracy of two tests can improve by 20% and 38% respectively, after the gravity is compensated by the proposed method.

  13. Miniaturised Gravity Sensors for Remote Gravity Surveys.

    Science.gov (United States)

    Middlemiss, R. P.; Bramsiepe, S. G.; Hough, J.; Paul, D. J.; Rowan, S.; Samarelli, A.; Hammond, G.

    2016-12-01

    Gravimetry lets us see the world from a completely different perspective. The ability to measure tiny variations in gravitational acceleration (g), allows one to see not just the Earth's gravitational pull, but the influence of smaller objects. The more accurate the gravimeter, the smaller the objects one can see. Gravimetry has applications in many different fields: from tracking magma moving under volcanoes before eruptions; to locating hidden tunnels. The top commercial gravimeters weigh tens of kg and cost at least $100,000, limiting the situations in which they can be used. By contrast, smart phones use a MEMS (microelectromechanical system) accelerometer that can measure the orientation of the device. These are not nearly sensitive or stable enough to be used for the gravimetry but they are cheap, light-weight and mass-producible. At Glasgow University we have developed a MEMS device with both the stability and sensitivity for useful gravimetric measurements. This was demonstrated by a measurement of the Earth tides - the first time this has been achieved with a MEMS sensor. A gravimeter of this size opens up the possiblility for new gravity imaging modalities. Thousands of gravimeters could be networked over a survey site, storing data on an SD card or communicating wirelessly to a remote location. These devices could also be small enough to be carried by a UAVs: airborne gravity surveys could be carried out at low altitude by mulitple UAVs, or UAVs could be used to deliver ground based gravimeters to remote or inaccessible locations.

  14. Surfing surface gravity waves

    Science.gov (United States)

    Pizzo, Nick

    2017-11-01

    A simple criterion for water particles to surf an underlying surface gravity wave is presented. It is found that particles travelling near the phase speed of the wave, in a geometrically confined region on the forward face of the crest, increase in speed. The criterion is derived using the equation of John (Commun. Pure Appl. Maths, vol. 6, 1953, pp. 497-503) for the motion of a zero-stress free surface under the action of gravity. As an example, a breaking water wave is theoretically and numerically examined. Implications for upper-ocean processes, for both shallow- and deep-water waves, are discussed.

  15. Towards a quantum gravity

    International Nuclear Information System (INIS)

    Romney, B.; Barrau, A.; Vidotto, F.; Le Meur, H.; Noui, K.

    2011-01-01

    The loop quantum gravity is the only theory that proposes a quantum description of space-time and therefore of gravitation. This theory predicts that space is not infinitely divisible but that is has a granular structure at the Planck scale (10 -35 m). Another feature of loop quantum gravity is that it gets rid of the Big-Bang singularity: our expanding universe may come from the bouncing of a previous contracting universe, in this theory the Big-Bang is replaced with a big bounce. The loop quantum theory predicts also the huge number of quantum states that accounts for the entropy of large black holes. (A.C.)

  16. Terrestrial gravity data analysis for interim gravity model improvement

    Science.gov (United States)

    1987-01-01

    This is the first status report for the Interim Gravity Model research effort that was started on June 30, 1986. The basic theme of this study is to develop appropriate models and adjustment procedures for estimating potential coefficients from terrestrial gravity data. The plan is to use the latest gravity data sets to produce coefficient estimates as well as to provide normal equations to NASA for use in the TOPEX/POSEIDON gravity field modeling program.

  17. The aux1 gene of the Ri plasmid is sufficient to confer auxin autotrophy in tobacco BY-2 cells.

    Science.gov (United States)

    Nemoto, Keiichirou; Hara, Masamitsu; Goto, Shingo; Kasai, Kouji; Seki, Hikaru; Suzuki, Masashi; Oka, Atsuhiro; Muranaka, Toshiya; Mano, Yoshihiro

    2009-05-01

    Tobacco (Nicotiana tabacum) Bright Yellow-2 (BY-2) cells are rapidly proliferating meristematic cells that require auxin for culture in vitro. We have established several transgenic BY-2 cell lines that carry the T-DNA of Agrobacterium rhizogenes 15834, which harbors an agropine-type root-inducing (Ri) plasmid. Two of these lines, BYHR-3 and BYHR-7, were used to test the role of auxin in the proliferation of plant cells. The lines grew rapidly in Linsmaier-Skoog (LS) medium lacking auxin and other phytohormones. The TR-DNA, containing the aux1 (tryptophan monooxygenase) and aux2 (indoleacetamide hydrolase) genes, was present in the genomes of both transgenic lines, whereas the TL-DNA, containing the rolA, B, C and D genes, was present in the genome of BYHR-7 but not BYHR-3. Since the introduction of the rolABCD genes alone did not affect the auxin requirement of BY-2 cells, the aux1 and aux2 genes, but not the rolABCD genes, appear to be relevant to the auxin autotrophy of these transgenic lines. Furthermore, the overexpression of aux1 allowed BY-2 cells to grow rapidly in the absence of auxin, suggesting the existence in plant cells of an unidentified gene whose product is functionally equivalent or similar to that of aux2 of the Ri plasmid.

  18. Gravity Data for South America

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The gravity station data (152,624 records) were compiled by the University of Texas at Dallas. This data base was received in June 1992. Principal gravity parameters...

  19. Interior Alaska Gravity Station Data

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The gravity station data total 9416 records. This data base was received in March 1997. Principal gravity parameters include Free-air Anomalies which have been...

  20. Gravity Station Data for Spain

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The gravity station data total 28493 records. This data base was received in April 1997. Principal gravity parameters include Free-air Anomalies which have been...

  1. Gravity Station Data for Portugal

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The gravity station data total 3064 records. This data base was received in April 1997. Principal gravity parameters include Free-air Anomalies which have been...

  2. Massive Conformal Gravity

    International Nuclear Information System (INIS)

    Faria, F. F.

    2014-01-01

    We construct a massive theory of gravity that is invariant under conformal transformations. The massive action of the theory depends on the metric tensor and a scalar field, which are considered the only field variables. We find the vacuum field equations of the theory and analyze its weak-field approximation and Newtonian limit.

  3. Colossal creations of gravity

    DEFF Research Database (Denmark)

    Skielboe, Andreas

    Gravity governs the evolution of the universe on the largest scales, and powers some of the most extreme objects at the centers of galaxies. Determining the masses and kinematics of galaxy clusters provides essential constraints on the large-scale structure of the universe, and act as direct probes...

  4. A Trick of Gravity

    Science.gov (United States)

    Newburgh, Ronald

    2010-01-01

    It's both surprising and rewarding when an old, standard problem reveals a subtlety that expands its pedagogic value. I realized recently that the role of gravity in the range equation for a projectile is not so simple as first appears. This realization may be completely obvious to others but was quite new to me.

  5. Discrete Lorentzian quantum gravity

    NARCIS (Netherlands)

    Loll, R.

    2000-01-01

    Just as for non-abelian gauge theories at strong coupling, discrete lattice methods are a natural tool in the study of non-perturbative quantum gravity. They have to reflect the fact that the geometric degrees of freedom are dynamical, and that therefore also the lattice theory must be formulated

  6. Loop quantum gravity

    International Nuclear Information System (INIS)

    Pullin, J.

    2015-01-01

    Loop quantum gravity is one of the approaches that are being studied to apply the rules of quantum mechanics to the gravitational field described by the theory of General Relativity . We present an introductory summary of the main ideas and recent results. (Author)

  7. A finite quantum gravity

    International Nuclear Information System (INIS)

    Meszaros, A.

    1984-05-01

    In case the graviton has a very small non-zero mass, the existence of six additional massive gravitons with very big masses leads to a finite quantum gravity. There is an acausal behaviour on the scales that is determined by the masses of additional gravitons. (author)

  8. Venus - Ishtar gravity anomaly

    Science.gov (United States)

    Sjogren, W. L.; Bills, B. G.; Mottinger, N. A.

    1984-01-01

    The gravity anomaly associated with Ishtar Terra on Venus is characterized, comparing line-of-sight acceleration profiles derived by differentiating Pioneer Venus Orbiter Doppler residual profiles with an Airy-compensated topographic model. The results are presented in graphs and maps, confirming the preliminary findings of Phillips et al. (1979). The isostatic compensation depth is found to be 150 + or - 30 km.

  9. Torsion induces gravity

    International Nuclear Information System (INIS)

    Aros, Rodrigo; Contreras, Mauricio

    2006-01-01

    In this work the Poincare-Chern-Simons and anti-de Sitter-Chern-Simons gravities are studied. For both, a solution that can be cast as a black hole with manifest torsion is found. Those solutions resemble Schwarzschild and Schwarzschild-AdS solutions, respectively

  10. Discrete quantum gravity

    International Nuclear Information System (INIS)

    Williams, J.W.

    1992-01-01

    After a brief introduction to Regge calculus, some examples of its application is quantum gravity are described in this paper. In particular, the earliest such application, by Ponzano and Regge, is discussed in some detail and it is shown how this leads naturally to current work on invariants of three-manifolds

  11. Loop Quantum Gravity

    Directory of Open Access Journals (Sweden)

    Rovelli Carlo

    1998-01-01

    Full Text Available The problem of finding the quantum theory of the gravitational field, and thus understanding what is quantum spacetime, is still open. One of the most active of the current approaches is loop quantum gravity. Loop quantum gravity is a mathematically well-defined, non-perturbative and background independent quantization of general relativity, with its conventional matter couplings. Research in loop quantum gravity today forms a vast area, ranging from mathematical foundations to physical applications. Among the most significant results obtained are: (i The computation of the physical spectra of geometrical quantities such as area and volume, which yields quantitative predictions on Planck-scale physics. (ii A derivation of the Bekenstein-Hawking black hole entropy formula. (iii An intriguing physical picture of the microstructure of quantum physical space, characterized by a polymer-like Planck scale discreteness. This discreteness emerges naturally from the quantum theory and provides a mathematically well-defined realization of Wheeler's intuition of a spacetime ``foam''. Long standing open problems within the approach (lack of a scalar product, over-completeness of the loop basis, implementation of reality conditions have been fully solved. The weak part of the approach is the treatment of the dynamics: at present there exist several proposals, which are intensely debated. Here, I provide a general overview of ideas, techniques, results and open problems of this candidate theory of quantum gravity, and a guide to the relevant literature.

  12. Analyzing Cell Wall Elasticity After Hormone Treatment: An Example Using Tobacco BY-2 Cells and Auxin.

    Science.gov (United States)

    Braybrook, Siobhan A

    2017-01-01

    Atomic force microscopy, and related nano-indentation techniques, is a valuable tool for analyzing the elastic properties of plant cell walls as they relate to changes in cell wall chemistry, changes in development, and response to hormones. Within this chapter I will describe a method for analyzing the effect of the phytohormone auxin on the cell wall elasticity of tobacco BY-2 cells. This general method may be easily altered for different experimental systems and hormones of interest.

  13. A concise flow synthesis of indole-3-carboxylic ester and its derivatisation to an auxin mimic

    Directory of Open Access Journals (Sweden)

    Marcus Baumann

    2017-11-01

    Full Text Available An assembled suite of flow-based transformations have been used to rapidly scale-up the production of a novel auxin mimic-based herbicide which was required for preliminary field trials. The overall synthetic approach and optimisation studies are described along with a full description of the final reactor configurations employed for the synthesis as well as the downstream processing of the reaction streams.

  14. Short-term salt stress in Brassica rapa seedlings causes alterations in auxin metabolism

    Czech Academy of Sciences Publication Activity Database

    Pavlović, I.; Pěnčík, Aleš; Novák, Ondřej; Vujčić, V.; Radić Brkanac, S.; Lepeduš, H.; Strnad, Miroslav; Salopek-Sondi, B.

    2018-01-01

    Roč. 125, APR (2018), s. 74-84 ISSN 0981-9428 R&D Projects: GA MŠk(CZ) LO1204; GA ČR(CZ) GA17-06613S Institutional support: RVO:61389030 Keywords : Auxin metabolism * Brassica rapa ssp. pekinensis * Growth inhibition * Principal component analysis * Reactive oxygen species * Short-term salinity stress * Stress hormones Subject RIV: EB - Genetics ; Molecular Biology OBOR OECD: Plant sciences, botany Impact factor: 2.724, year: 2016

  15. Cytokinins and auxins control the expression of a gene in Nicotiana plumbaginifolia cells by feedback regulation.

    Science.gov (United States)

    Dominov, J A; Stenzler, L; Lee, S; Schwarz, J J; Leisner, S; Howell, S H

    1992-01-01

    Both cytokinin (N6-benzyladenine [BA]) and auxin (2,4-dichlorophenoxyacetic acid [2,4-D]) stimulate the accumulation of an mRNA, represented by the cDNA pLS216, in Nicotiana plumbaginifolia suspension culture cells. The kinetics of RNA accumulation were different for the two hormones; however, the response to both was transient, and the magnitude of the response was dose dependent. Runoff transcription experiments demonstrated that the transient appearance of the RNA could be accounted for by feedback regulation of transcription and not by the induction of an RNA degradation system. The feedback mechanism appeared to desensitize the cells to further exposure of the hormone. In particular, cells became refractory to the subsequent addition of 2,4-D after the initial RNA accumulation response subsided. A very different response was observed when the second hormone was added to cells that had been desensitized to the first hormone. Under such conditions, BA produced a heightened response in cells desensitized to 2,4-D and vice versa. These findings support a model in which cytokinin further enhances the auxin response or prevents its feedback inhibition. The hormone-induced RNA accumulation was blocked by the protein kinase inhibitor staurosporin. On the other hand, the protein phosphatase inhibitor okadaic acid stimulated expression, and, in particular, okadaic acid was able to stimulate RNA accumulation in cells desensitized to auxin. This suggests that hormone activation involves phosphorylation of critical proteins on the hormone signaling pathway, whereas feedback inhibition may involve dephosphorylation of these proteins. The sequence of pLS216 is similar to genes in other plants that are stimulated by multiple agonists such as auxins, elicitors, and heavy metals, and to the gene encoding the stringent starvation protein in Escherichia coli. It is proposed that this gene family in various plants be called multiple stimulus response (msr) genes. PMID:1498603

  16. Effect of root application of 6-benzylamine purine on auxin transport in Malus domestica

    International Nuclear Information System (INIS)

    Stutte, G.

    1987-01-01

    The effect of 6-benzylamine purine (BA) on movement of napthalene acetic acid (NAA) applied to the shoot was investigated. Three-month-old York apple seedlings in sand culture were placed under mercury halide lamps (285 μmol m -2 s -1 ) at 22 0 C for 24 hours; then 13.8, 27.5 or 55 μMol of BA was applied as a soil drench. [ 14 C]-NAA was injected into the shoot at petiole base of 4th mature leaf. After 24 hours plants were harvested and movement of label acropetally to new shoot growth and basipetally to old shoot growth or roots determined. Seventeen (S.E. 3.3) percent of applied label was recovered away from application site. In controls, 67% of 14 C that moved was recovered from new shoot growth, 9% in roots and 24% in old shoot tissue. The 13.8 μMol treatment resulted in 37% of label being recovered in root tissue and 48% in new growth. The 27.5 and 55 μMol applications increased the amount recovered in old shoot tissue but did not increase labelling of root tissues

  17. Auxin transport, metabolism, and signalling during nodule initiation: indeterminate and determinate nodules

    NARCIS (Netherlands)

    Kohlen, W.; Ng, Jason Liang Pin; Deinum, E.E.; Mathesius, Ulrike

    2018-01-01

    Most legumes can form a unique type of lateral organ on their roots: root nodules. These structures host symbiotic nitrogen-fixing bacteria called rhizobia. Several different types of nodules can be found in nature, but the two best-studied types are called indeterminate and determinate nodules.

  18. Polar transport of plant hormone auxin – the role of PIN-FORMED (PIN) proteins

    Czech Academy of Sciences Publication Activity Database

    Zažímalová, Eva; Křeček, Pavel; Skůpa, Petr; Hoyerová, Klára; Petrášek, Jan

    2007-01-01

    Roč. 64, č. 13 (2007), s. 1621-1637 ISSN 1420-682X R&D Projects: GA AV ČR IAA6038303; GA AV ČR KJB600380604; GA MŠk(CZ) LC06034 Institutional research plan: CEZ:AV0Z50380511 Source of funding: V - iné verejné zdroje ; V - iné verejné zdroje ; V - iné verejné zdroje Keywords : Plant hormone * phytohormone * plant growth regulator Subject RIV: ED - Physiology Impact factor: 5.239, year: 2007

  19. Auxin transport inhibitors impair vesicle motility and actin cytoskeleton dynamics in diverse eukaryotes

    Czech Academy of Sciences Publication Activity Database

    Dhonukshe, P.; Grigoriev, I.; Fischer, R.; Tominaga, M.; Robinson, D.G.; Hašek, Jiří; Paciorek, T.; Petrášek, Jan; Seifertová, Daniela; Tejos, R.; Meisel, L.A.; Zažímalová, Eva; Gadella, T.W.J.; Stierhof, Y. D.; Ueda, T.; Oiwa, K.; Akhmanova, A.; Brock, R.; Spang, A.; Friml, J.

    2008-01-01

    Roč. 105, č. 11 (2008), s. 4489-4494 ISSN 0027-8424 R&D Projects: GA ČR GA204/05/0838; GA AV ČR(CZ) IAA601630703; GA MŠk(CZ) LC06034; GA AV ČR KJB600380604 Institutional research plan: CEZ:AV0Z50200510; CEZ:AV0Z50380511 Keywords : pin proteins * plant development * vesicle traffic Subject RIV: EE - Microbiology, Virology Impact factor: 9.380, year: 2008

  20. Quantum Gravity Effects in Cosmology

    Directory of Open Access Journals (Sweden)

    Gu Je-An

    2018-01-01

    Full Text Available Within the geometrodynamic approach to quantum cosmology, we studied the quantum gravity effects in cosmology. The Gibbons-Hawking temperature is corrected by quantum gravity due to spacetime fluctuations and the power spectrum as well as any probe field will experience the effective temperature, a quantum gravity effect.

  1. Even-dimensional topological gravity from Chern-Simons gravity

    International Nuclear Information System (INIS)

    Merino, N.; Perez, A.; Salgado, P.

    2009-01-01

    It is shown that the topological action for gravity in 2n-dimensions can be obtained from the (2n+1)-dimensional Chern-Simons gravity genuinely invariant under the Poincare group. The 2n-dimensional topological gravity is described by the dynamics of the boundary of a (2n+1)-dimensional Chern-Simons gravity theory with suitable boundary conditions. The field φ a , which is necessary to construct this type of topological gravity in even dimensions, is identified with the coset field associated with the non-linear realizations of the Poincare group ISO(d-1,1).

  2. GEODYNAMIC WAVES AND GRAVITY

    Directory of Open Access Journals (Sweden)

    A. V. Vikulin

    2014-01-01

    Full Text Available  Gravity phenomena related to the Earth movements in the Solar System and through the Galaxy are reviewed. Such movements are manifested by geological processes on the Earth and correlate with geophysical fields of the Earth. It is concluded that geodynamic processes and the gravity phenomena (including those of cosmic nature are related.  The state of the geomedium composed of blocks is determined by stresses with force moment and by slow rotational waves that are considered as a new type of movements [Vikulin, 2008, 2010]. It is shown that the geomedium has typical rheid properties [Carey, 1954], specifically an ability to flow while being in the solid state [Leonov, 2008]. Within the framework of the rotational model with a symmetric stress tensor, which is developed by the authors [Vikulin, Ivanchin, 1998; Vikulin et al., 2012a, 2013], such movement of the geomedium may explain the energy-saturated state of the geomedium and a possibility of its movements in the form of vortex geological structures [Lee, 1928]. The article discusses the gravity wave detection method based on the concept of interactions between gravity waves and crustal blocks [Braginsky et al., 1985]. It is concluded that gravity waves can be recorded by the proposed technique that detects slow rotational waves. It is shown that geo-gravitational movements can be described by both the concept of potential with account of gravitational energy of bodies [Kondratyev, 2003] and the nonlinear physical acoustics [Gurbatov et al., 2008]. Based on the combined description of geophysical and gravitational wave movements, the authors suggest a hypothesis about the nature of spin, i.e. own moment as a demonstration of the space-time ‘vortex’ properties.  

  3. Evidence That Chlorinated Auxin Is Restricted to the Fabaceae But Not to the Fabeae.

    Science.gov (United States)

    Lam, Hong Kiat; McAdam, Scott A M; McAdam, Erin L; Ross, John J

    2015-07-01

    Auxin is a pivotal plant hormone, usually occurring in the form of indole-3-acetic acid (IAA). However, in maturing pea (Pisum sativum) seeds, the level of the chlorinated auxin, 4-chloroindole-3-acetic acid (4-Cl-IAA), greatly exceeds that of IAA. A key issue is how plants produce halogenated compounds such as 4-Cl-IAA. To better understand this topic, we investigated the distribution of the chlorinated auxin. We show for the first time, to our knowledge, that 4-Cl-IAA is found in the seeds of Medicago truncatula, Melilotus indicus, and three species of Trifolium. Furthermore, we found no evidence that Pinus spp. synthesize 4-Cl-IAA in seeds, contrary to a previous report. The evidence indicates a single evolutionary origin of 4-Cl-IAA synthesis in the Fabaceae, which may provide an ideal model system to further investigate the action and activity of halogenating enzymes in plants. © 2015 American Society of Plant Biologists. All Rights Reserved.

  4. GTPase ROP2 binds and promotes activation of target of rapamycin, TOR, in response to auxin.

    Science.gov (United States)

    Schepetilnikov, Mikhail; Makarian, Joelle; Srour, Ola; Geldreich, Angèle; Yang, Zhenbiao; Chicher, Johana; Hammann, Philippe; Ryabova, Lyubov A

    2017-04-03

    Target of rapamycin (TOR) promotes reinitiation at upstream ORFs (uORFs) in genes that play important roles in stem cell regulation and organogenesis in plants. Here, we report that the small GTPase ROP2, if activated by the phytohormone auxin, promotes activation of TOR, and thus translation reinitiation of uORF-containing mRNAs. Plants with high levels of active ROP2, including those expressing constitutively active ROP2 (CA-ROP2), contain high levels of active TOR ROP2 physically interacts with and, when GTP-bound, activates TOR in vitro TOR activation in response to auxin is abolished in ROP-deficient rop2 rop6 ROP4 RNAi plants. GFP-TOR can associate with endosome-like structures in ROP2-overexpressing plants, indicating that endosomes mediate ROP2 effects on TOR activation. CA-ROP2 is efficient in loading uORF-containing mRNAs onto polysomes and stimulates translation in protoplasts, and both processes are sensitive to TOR inhibitor AZD-8055. TOR inactivation abolishes ROP2 regulation of translation reinitiation, but not its effects on cytoskeleton or intracellular trafficking. These findings imply a mode of translation control whereby, as an upstream effector of TOR, ROP2 coordinates TOR function in translation reinitiation pathways in response to auxin. © 2017 The Authors.

  5. Biosynthetic pathway of the phytohormone auxin in insects and screening of its inhibitors.

    Science.gov (United States)

    Suzuki, Hiroyoshi; Yokokura, Junpei; Ito, Tsukasa; Arai, Ryoma; Yokoyama, Chiaki; Toshima, Hiroaki; Nagata, Shinji; Asami, Tadao; Suzuki, Yoshihito

    2014-10-01

    Insect galls are abnormal plant tissues induced by galling insects. The galls are used for food and habitation, and the phytohormone auxin, produced by the insects, may be involved in their formation. We found that the silkworm, a non-galling insect, also produces an active form of auxin, indole-3-acetic acid (IAA), by de novo synthesis from tryptophan (Trp). A detailed metabolic analysis of IAA using IAA synthetic enzymes from silkworms indicated an IAA biosynthetic pathway composed of a three-step conversion: Trp → indole-3-acetaldoxime → indole-3-acetaldehyde (IAAld) → IAA, of which the first step is limiting IAA production. This pathway was shown to also operate in gall-inducing sawfly. Screening of a chemical library identified two compounds that showed strong inhibitory activities on the conversion step IAAld → IAA. The inhibitors can be efficiently used to demonstrate the importance of insect-synthesized auxin in gall formation in the future. Copyright © 2014 Elsevier Ltd. All rights reserved.

  6. Specific photoaffinity labeling of two plasma membrane polypeptides with an azido auxin

    International Nuclear Information System (INIS)

    Hicks, G.R.; Rayle, D.L.; Jones, A.M.; Lomax, T.L.

    1989-01-01

    Plasma membrane vesicles were isolated from zucchini (Cucurbita pepo) hypocotyl tissue by aqueous phase partitioning and assessed for homogeneity by the use of membrane-specific enzyme assays. The highly pure plasma membrane vesicles maintained a pH differential across the membrane and accumulated a tritiated azido analogue of 3-indoleacetic acid (IAA), 5-azido-[7- 3 H]IAA([ 3 H]N 3 IAA), in a manner similar to the accumulation of [ 3 H]IAA. The association of the [ 3 H]N 3 IAA with membrane vesicles was saturable and subject to competition by IAA and auxin analogues. Auxin-binding proteins were photoaffinity labeled by addition of [ 3 H]N 3 IAA to plasma membrane vesicles prior to exposure to UV light and detected by subsequent NaDodSO 4 /PAGE and fluorography. When the reaction temperature was lowered to -196 degree C, high-specific-activity labeling of a 40-kDa and a 42-kDa polypeptide was observed. Collectively, these results suggest that the radiolabeled polypeptides are auxin receptors. The covalent nature of the label should facilitate purification and further characterization of the receptors

  7. Changes in auxin activity in tumourous and normal tobacco calluses treated with morphactin IT 3233

    Directory of Open Access Journals (Sweden)

    Z. Chirek

    2015-01-01

    Full Text Available The addition of morphactin IT 3233 in 1-40 mg/dm3 concentrations to the medium inhibited the growth in vitro of normal and tumourous tobacco calluses. The auxin activity (estimated by the Avena coleoptile straight growth test of the acid ether extracts from these tissues increased. The activity of zone I (Rf 0.2-0.4, 0.5, solvent system: butanol:water:ammonia 10:10:1 in normal tissues increased more intensively than that of zone II (Rf 0.6-0.8, 0.9. In tumourous tissues, however, these changes were smaller and they concerned merely zone I of auxin activity (Rf 0.0-0.5. It seems that the mechanism of morphactin activity in both kinds of tissue is different. It may be supposed that the excessive accumulation of auxins induces growth inhibition of tissues. A previously found increase in the activity of IAA-oxidase influenced by morphactin might be considered as an adaptation to a higher level of IAA.

  8. Identification, isolation and expression analysis of auxin response factor (ARF) genes in Solanum lycopersicum.

    Science.gov (United States)

    Wu, Jian; Wang, Feiyan; Cheng, Lin; Kong, Fuling; Peng, Zhen; Liu, Songyu; Yu, Xiaolin; Lu, Gang

    2011-11-01

    Auxin response factors (ARFs) encode transcriptional factors that bind specifically to the TGTCTC-containing auxin response elements found in the promoters of primary/early auxin response genes that regulate plant development. In this study, investigation of the tomato genome revealed 21 putative functional ARF genes (SlARFs), a number comparable to that found in Arabidopsis (23) and rice (25). The full cDNA sequences of 15 novel SlARFs were isolated and delineated by sequencing of PCR products. A comprehensive genome-wide analysis of this gene family is presented, including the gene structures, chromosome locations, phylogeny, and conserved motifs. In addition, a comparative analysis between ARF family genes in tomato and maize was performed. A phylogenetic tree generated from alignments of the full-length protein sequences of 21 OsARFs, 23 AtARFs, 31 ZmARFs, and 21 SlARFs revealed that these ARFs were clustered into four major groups. However, we could not find homologous genes in rice, maize, or tomato with AtARF12-15 and AtARF20-23. The expression patterns of tomato ARF genes were analyzed by quantitative real-time PCR. Our comparative analysis will help to define possible functions for many of these newly isolated ARF-family genes in plant development.

  9. Atom Interferometer Technologies in Space for Gravity Mapping and Gravity Science

    Science.gov (United States)

    Williams, Jason; Chiow, Sheng-Wey; Kellogg, James; Kohel, James; Yu, Nan

    2015-05-01

    Atom interferometers utilize the wave-nature of atomic gases for precision measurements of inertial forces, with potential applications ranging from gravity mapping for planetary science to unprecedented tests of fundamental physics with quantum gases. The high stability and sensitivity intrinsic to these devices already place them among the best terrestrial sensors available for measurements of gravitational accelerations, rotations, and gravity gradients, with the promise of several orders of magnitude improvement in their detection sensitivity in microgravity. Consequently, multiple precision atom-interferometer-based projects are under development at the Jet Propulsion Laboratory, including a dual-atomic-species interferometer that is to be integrated into the Cold Atom Laboratory onboard the International Space Station and a highly stable gravity gradiometer in a transportable design relevant for earth science measurements. We will present JPL's activities in the use of precision atom interferometry for gravity mapping and gravitational wave detection in space. Our recent progresses bringing the transportable JPL atom interferometer instrument to be competitive with the state of the art and simulations of the expected capabilities of a proposed flight project will also be discussed. This research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.

  10. Holography, Gravity and Condensed Matter

    Energy Technology Data Exchange (ETDEWEB)

    Hartnoll, Sean [Stanford Univ., CA (United States). Dept. of Physics

    2017-12-20

    Over the five years of funding from this grant, I produced 26 publications. These include a book-long monograph on "Holographic Quantum Matter" that is currently in press with MIT press. The remainder were mostly published in Physical Review Letters, the Journal of High Energy Physics, Nature Physics, Classical and Quantum Gravity and Physical Review B. Over this period, the field of holography applied to condensed matter physics developed from a promising theoretical approach to a mature conceptual and practical edifice, whose ideas were realized in experiments. My own work played a central role in this development. In particular, in the final year of this grant, I co-authored two experimental papers in which ideas that I had developed in earlier years were shown to usefully describe transport in strongly correlated materials — these papers were published in Science and in the Proceedings of the National Academy of Sciences (obviously my contribution to these papers was theoretical). My theoretical work in this period developed several new directions of research that have proven to be influential. These include (i) The construction of highly inhomogeneous black hole event horizons, realizing disordered fixed points and describing new regimes of classical gravity, (ii) The conjecture of a bound on diffusivities that could underpin transport in strongly interacting media — an idea which may be proven in the near future and has turned out to be intimately connected to studies of quantum chaos in black holes and strongly correlated media, (iii) The characterization of new forms of hydrodynamic transport, e.g. with phase-disordered order parameters. These studies pertain to key open questions in our understanding of how non-quasiparticle, intrinsically strongly interacting systems can behave. In addition to the interface between holography and strongly interacting condensed matter systems, I made several advances on understanding the role of entanglement in quantum

  11. Metastable gravity on classical defects

    International Nuclear Information System (INIS)

    Ringeval, Christophe; Rombouts, Jan-Willem

    2005-01-01

    We discuss the realization of metastable gravity on classical defects in infinite-volume extra dimensions. In dilatonic Einstein gravity, it is found that the existence of metastable gravity on the defect core requires violation of the dominant energy condition for codimension N c =2 defects. This is illustrated with a detailed analysis of a six-dimensional hyperstring minimally coupled to dilaton gravity. We present the general conditions under which a codimension N c >2 defect admits metastable modes, and find that they differ from lower codimensional models in that, under certain conditions, they do not require violation of energy conditions to support quasilocalized gravity

  12. New auxin analogs with growth-promoting effects in intact plants reveal a chemical strategy to improve hormone delivery.

    Science.gov (United States)

    Savaldi-Goldstein, Sigal; Baiga, Thomas J; Pojer, Florence; Dabi, Tsegeye; Butterfield, Cristina; Parry, Geraint; Santner, Aaron; Dharmasiri, Nihal; Tao, Yi; Estelle, Mark; Noel, Joseph P; Chory, Joanne

    2008-09-30

    Plant growth depends on the integration of environmental cues and phytohormone-signaling pathways. During seedling emergence, elongation of the embryonic stem (hypocotyl) serves as a readout for light and hormone-dependent responses. We screened 10,000 chemicals provided exogenously to light-grown seedlings and identified 100 compounds that promote hypocotyl elongation. Notably, one subset of these chemicals shares structural characteristics with the synthetic auxins, 2,4-dichlorophenoxyacetic acid (2,4-D), and 1-naphthaleneacetic acid (1-NAA); however, traditional auxins (e.g., indole-3-acetic acid [IAA], 2,4-D, 1-NAA) have no effect on hypocotyl elongation. We show that the new compounds act as "proauxins" akin to prodrugs. Our data suggest that these compounds diffuse efficiently to the hypocotyls, where they undergo cleavage at varying rates, releasing functional auxins. To investigate this principle, we applied a masking strategy and designed a pro-2,4-D. Unlike 2,4-D alone, this pro-2,4-D enhanced hypocotyl elongation. We further demonstrated the utility of the proauxins by characterizing auxin responses in light-grown hypocotyls of several auxin receptor mutants. These new compounds thus provide experimental access to a tissue previously inaccessible to exogenous application of auxins. Our studies exemplify the combined power of chemical genetics and biochemical analyses for discovering and refining prohormone analogs with selective activity in specific plant tissues. In addition to the utility of these compounds for addressing questions related to auxin and light-signaling interactions, one can envision using these simple principles to study other plant hormone and small molecule responses in temporally and spatially controlled ways.

  13. Deliberate ROS production and auxin synergistically trigger the asymmetrical division generating the subsidiary cells in Zea mays stomatal complexes.

    Science.gov (United States)

    Livanos, Pantelis; Galatis, Basil; Apostolakos, Panagiotis

    2016-07-01

    Subsidiary cell generation in Poaceae is an outstanding example of local intercellular stimulation. An inductive stimulus emanates from the guard cell mother cells (GMCs) towards their laterally adjacent subsidiary cell mother cells (SMCs) and triggers the asymmetrical division of the latter. Indole-3-acetic acid (IAA) immunolocalization in Zea mays protoderm confirmed that the GMCs function as local sources of auxin and revealed that auxin is polarly accumulated between GMCs and SMCs in a timely-dependent manner. Besides, staining techniques showed that reactive oxygen species (ROS) exhibit a closely similar, also time-dependent, pattern of appearance suggesting ROS implication in subsidiary cell formation. This phenomenon was further investigated by using the specific NADPH-oxidase inhibitor diphenylene iodonium, the ROS scavenger N-acetyl-cysteine, menadione which leads to ROS overproduction, and H2O2. Treatments with diphenylene iodonium, N-acetyl-cysteine, and menadione specifically blocked SMC polarization and asymmetrical division. In contrast, H2O2 promoted the establishment of SMC polarity and subsequently subsidiary cell formation in "younger" protodermal areas. Surprisingly, H2O2 favored the asymmetrical division of the intervening cells of the stomatal rows leading to the creation of extra apical subsidiary cells. Moreover, H2O2 altered IAA localization, whereas synthetic auxin analogue 1-napthaleneacetic acid enhanced ROS accumulation. Combined treatments with ROS modulators along with 1-napthaleneacetic acid or 2,3,5-triiodobenzoic acid, an auxin efflux inhibitor, confirmed the crosstalk between ROS and auxin functioning during subsidiary cell generation. Collectively, our results demonstrate that ROS are critical partners of auxin during development of Z. mays stomatal complexes. The interplay between auxin and ROS seems to be spatially and temporarily regulated.

  14. Quantum gravity from noncommutative spacetime

    International Nuclear Information System (INIS)

    Lee, Jungjai; Yang, Hyunseok

    2014-01-01

    We review a novel and authentic way to quantize gravity. This novel approach is based on the fact that Einstein gravity can be formulated in terms of a symplectic geometry rather than a Riemannian geometry in the context of emergent gravity. An essential step for emergent gravity is to realize the equivalence principle, the most important property in the theory of gravity (general relativity), from U(1) gauge theory on a symplectic or Poisson manifold. Through the realization of the equivalence principle, which is an intrinsic property in symplectic geometry known as the Darboux theorem or the Moser lemma, one can understand how diffeomorphism symmetry arises from noncommutative U(1) gauge theory; thus, gravity can emerge from the noncommutative electromagnetism, which is also an interacting theory. As a consequence, a background-independent quantum gravity in which the prior existence of any spacetime structure is not a priori assumed but is defined by using the fundamental ingredients in quantum gravity theory can be formulated. This scheme for quantum gravity can be used to resolve many notorious problems in theoretical physics, such as the cosmological constant problem, to understand the nature of dark energy, and to explain why gravity is so weak compared to other forces. In particular, it leads to a remarkable picture of what matter is. A matter field, such as leptons and quarks, simply arises as a stable localized geometry, which is a topological object in the defining algebra (noncommutative *-algebra) of quantum gravity.

  15. Quantum gravity from noncommutative spacetime

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jungjai [Daejin University, Pocheon (Korea, Republic of); Yang, Hyunseok [Korea Institute for Advanced Study, Seoul (Korea, Republic of)

    2014-12-15

    We review a novel and authentic way to quantize gravity. This novel approach is based on the fact that Einstein gravity can be formulated in terms of a symplectic geometry rather than a Riemannian geometry in the context of emergent gravity. An essential step for emergent gravity is to realize the equivalence principle, the most important property in the theory of gravity (general relativity), from U(1) gauge theory on a symplectic or Poisson manifold. Through the realization of the equivalence principle, which is an intrinsic property in symplectic geometry known as the Darboux theorem or the Moser lemma, one can understand how diffeomorphism symmetry arises from noncommutative U(1) gauge theory; thus, gravity can emerge from the noncommutative electromagnetism, which is also an interacting theory. As a consequence, a background-independent quantum gravity in which the prior existence of any spacetime structure is not a priori assumed but is defined by using the fundamental ingredients in quantum gravity theory can be formulated. This scheme for quantum gravity can be used to resolve many notorious problems in theoretical physics, such as the cosmological constant problem, to understand the nature of dark energy, and to explain why gravity is so weak compared to other forces. In particular, it leads to a remarkable picture of what matter is. A matter field, such as leptons and quarks, simply arises as a stable localized geometry, which is a topological object in the defining algebra (noncommutative *-algebra) of quantum gravity.

  16. The gravity field and GGOS

    DEFF Research Database (Denmark)

    Forsberg, René; Sideris, M.G.; Shum, C.K.

    2005-01-01

    The gravity field of the earth is a natural element of the Global Geodetic Observing System (GGOS). Gravity field quantities are like spatial geodetic observations of potential very high accuracy, with measurements, currently at part-per-billion (ppb) accuracy, but gravity field quantities are also...... unique as they can be globally represented by harmonic functions (long-wavelength geopotential model primarily from satellite gravity field missions), or based on point sampling (airborne and in situ absolute and superconducting gravimetry). From a GGOS global perspective, one of the main challenges...... is to ensure the consistency of the global and regional geopotential and geoid models, and the temporal changes of the gravity field at large spatial scales. The International Gravity Field Service, an umbrella "level-2" IAG service (incorporating the International Gravity Bureau, International Geoid Service...

  17. Investigating gravity waves evidences in the Venus upper atmosphere

    Science.gov (United States)

    Migliorini, Alessandra; Altieri, Francesca; Shakun, Alexey; Zasova, Ludmila; Piccioni, Giuseppe; Bellucci, Giancarlo; Grassi, Davide

    2014-05-01

    We present a method to investigate gravity waves properties in the upper mesosphere of Venus, through the O2 nightglow observations acquired with the imaging spectrometer VIRTIS on board Venus Express. Gravity waves are important dynamical features that transport energy and momentum. They are related to the buoyancy force, which lifts air particles. Then, the vertical displacement of air particles produces density changes that cause gravity to act as restoring force. Gravity waves can manifest through fluctuations on temperature and density fields, and hence on airglow intensities. We use the O2 nightglow profiles showing double peaked structures to study the influence of gravity waves in shaping the O2 vertical profiles and infer the waves properties. In analogy to the Earth's and Mars cases, we use a well-known theory to model the O2 nightglow emissions affected by gravity waves propagation. Here we propose a statistical discussion of the gravity waves characteristics, namely vertical wavelength and wave amplitude, with respect to local time and latitude. The method is applied to about 30 profiles showing double peaked structures, and acquired with the VIRTIS/Venus Express spectrometer, during the mission period from 2006-07-05 to 2008-08-15.

  18. Free surface flows under compensated gravity conditions

    CERN Document Server

    Dreyer, Miachel E

    2007-01-01

    This book considers the behavior of fluids in a low-gravity environment with special emphasis on application in PMD (propellant management device) systems . In the compensated gravity environment of a spacecraft, the hydrostatic pressure decreases to very low values depending on the residual acceleration, and surface tension forces become dominant. Consequently, surface tension can be used to transport and position liquids if the residual acceleration and the resulting hydrostatic pressure are small compared to the capillary pressure. One prominent application is the use of PMDs in surface-tension satellite tanks. PMDs must ensure that the tank outlet is covered with liquid whenever outflow is demanded. Furthermore, PMDs are used to ensure expulsion and refilling of tanks for liquids and gases for life support, reactants, and experiment supplies. Since most of the PMD designs are not testable on ground and thus rely on analytical or numerical concepts, this book treats three different flow problems with analy...

  19. Cosmological Tests of Gravity

    CERN Multimedia

    CERN. Geneva

    2017-01-01

    Extensions of Einstein’s theory of General Relativity are under investigation as a potential explanation of the accelerating expansion rate of the universe. I’ll present a cosmologist’s overview of attempts to test these ideas in an efficient and unbiased manner. I’ll start by introducing the bestiary of alternative gravity theories that have been put forwards. This proliferation of models motivates us to develop model-independent, agnostic tools for comparing the theory space to cosmological data. I’ll introduce the effective field theory for cosmological perturbations, a framework designed to unify modified gravity theories in terms of a manageable set of parameters. Having outlined the formalism, I’ll talk about the current constraints on this framework, and the improvements expected from the next generation of large galaxy clustering, weak lensing and intensity mapping experiments.

  20. The relativistic gravity train

    Science.gov (United States)

    Seel, Max

    2018-05-01

    The gravity train that takes 42.2 min from any point A to any other point B that is connected by a straight-line tunnel through Earth has captured the imagination more than most other applications in calculus or introductory physics courses. Brachystochron and, most recently, nonlinear density solutions have been discussed. Here relativistic corrections are presented. It is discussed how the corrections affect the time to fall through Earth, the Sun, a white dwarf, a neutron star, and—the ultimate limit—the difference in time measured by a moving, a stationary and the fiducial observer at infinity if the density of the sphere approaches the density of a black hole. The relativistic gravity train can serve as a problem with approximate and exact analytic solutions and as numerical exercise in any introductory course on relativity.

  1. Antimatter gravity experiment

    International Nuclear Information System (INIS)

    Brown, R.E.; Camp, J.B.; Darling, T.W.

    1990-01-01

    An experiment is being developed to measure the acceleration of the antiproton in the gravitational field of the earth. Antiprotons of a few MeV from the LEAR facility at CERN will be slowed, captured, cooled to a temperature of about 10 K, and subsequently launched a few at a time into a drift tube where the effect of gravity on their motion will be determined by a time-of-flight method. Development of the experiment is proceeding at Los Alamos using normal matter. The fabrication of a drift tube that will produce a region of space in which gravity is the dominant force on moving ions is of major difficulty. This involves a study of methods of minimizing the electric fields produced by spatially varying work functions on conducting surfaces. Progress in a number of areas is described, with stress on the drift-tube development

  2. Lectures on Quantum Gravity

    CERN Document Server

    Gomberoff, Andres

    2006-01-01

    The 2002 Pan-American Advanced Studies Institute School on Quantum Gravity was held at the Centro de Estudios Cientificos (CECS),Valdivia, Chile, January 4-14, 2002. The school featured lectures by ten speakers, and was attended by nearly 70 students from over 14 countries. A primary goal was to foster interaction and communication between participants from different cultures, both in the layman’s sense of the term and in terms of approaches to quantum gravity. We hope that the links formed by students and the school will persist throughout their professional lives, continuing to promote interaction and the essential exchange of ideas that drives research forward. This volume contains improved and updated versions of the lectures given at the School. It has been prepared both as a reminder for the participants, and so that these pedagogical introductions can be made available to others who were unable to attend. We expect them to serve students of all ages well.

  3. Topics in quantum gravity

    Energy Technology Data Exchange (ETDEWEB)

    Lamon, Raphael

    2010-06-29

    Quantum gravity is an attempt to unify general relativity with quantum mechanics which are the two highly successful fundamental theories of theoretical physics. The main difficulty in this unification arises from the fact that, while general relativity describes gravity as a macroscopic geometrical theory, quantum mechanics explains microscopic phenomena. As a further complication, not only do both theories describe different scales but also their philosophical ramifications and the mathematics used to describe them differ in a dramatic way. Consequently, one possible starting point of an attempt at a unification is quantum mechanics, i.e. particle physics, and try to incorporate gravitation. This pathway has been chosen by particle physicists which led to string theory. On the other hand, loop quantum gravity (LQG) chooses the other possibility, i.e. it takes the geometrical aspects of gravity seriously and quantizes geometry. The first part of this thesis deals with a generalization of loop quantum cosmology (LQC) to toroidal topologies. LQC is a quantization of homogenous solutions of Einstein's field equations using tools from LQG. First the general concepts of closed topologies is introduced with special emphasis on Thurston's theorem and its consequences. It is shown that new degrees of freedom called Teichmueller parameters come into play and their dynamics can be described by a Hamiltonian. Several numerical solutions for a toroidal universe are presented and discussed. Following the guidelines of LQG this dynamics are rewritten using the Ashtekar variables and numerical solutions are shown. However, in order to find a suitable Hilbert space a canonical transformation must be performed. On the other hand this transformation makes the quantization of geometrical quantities less tractable such that two different ways are presented. It is shown that in both cases the spectrum of such geometrical operators depends on the initial value problem

  4. Tensor Galileons and gravity

    Energy Technology Data Exchange (ETDEWEB)

    Chatzistavrakidis, Athanasios [Van Swinderen Institute for Particle Physics and Gravity, University of Groningen,Nijenborgh 4, 9747 AG Groningen (Netherlands); Khoo, Fech Scen [Department of Physics and Earth Sciences, Jacobs University Bremen,Campus Ring 1, 28759 Bremen (Germany); Roest, Diederik [Van Swinderen Institute for Particle Physics and Gravity, University of Groningen,Nijenborgh 4, 9747 AG Groningen (Netherlands); Schupp, Peter [Department of Physics and Earth Sciences, Jacobs University Bremen,Campus Ring 1, 28759 Bremen (Germany)

    2017-03-13

    The particular structure of Galileon interactions allows for higher-derivative terms while retaining second order field equations for scalar fields and Abelian p-forms. In this work we introduce an index-free formulation of these interactions in terms of two sets of Grassmannian variables. We employ this to construct Galileon interactions for mixed-symmetry tensor fields and coupled systems thereof. We argue that these tensors are the natural generalization of scalars with Galileon symmetry, similar to p-forms and scalars with a shift-symmetry. The simplest case corresponds to linearised gravity with Lovelock invariants, relating the Galileon symmetry to diffeomorphisms. Finally, we examine the coupling of a mixed-symmetry tensor to gravity, and demonstrate in an explicit example that the inclusion of appropriate counterterms retains second order field equations.

  5. Topics in quantum gravity

    International Nuclear Information System (INIS)

    Lamon, Raphael

    2010-01-01

    Quantum gravity is an attempt to unify general relativity with quantum mechanics which are the two highly successful fundamental theories of theoretical physics. The main difficulty in this unification arises from the fact that, while general relativity describes gravity as a macroscopic geometrical theory, quantum mechanics explains microscopic phenomena. As a further complication, not only do both theories describe different scales but also their philosophical ramifications and the mathematics used to describe them differ in a dramatic way. Consequently, one possible starting point of an attempt at a unification is quantum mechanics, i.e. particle physics, and try to incorporate gravitation. This pathway has been chosen by particle physicists which led to string theory. On the other hand, loop quantum gravity (LQG) chooses the other possibility, i.e. it takes the geometrical aspects of gravity seriously and quantizes geometry. The first part of this thesis deals with a generalization of loop quantum cosmology (LQC) to toroidal topologies. LQC is a quantization of homogenous solutions of Einstein's field equations using tools from LQG. First the general concepts of closed topologies is introduced with special emphasis on Thurston's theorem and its consequences. It is shown that new degrees of freedom called Teichmueller parameters come into play and their dynamics can be described by a Hamiltonian. Several numerical solutions for a toroidal universe are presented and discussed. Following the guidelines of LQG this dynamics are rewritten using the Ashtekar variables and numerical solutions are shown. However, in order to find a suitable Hilbert space a canonical transformation must be performed. On the other hand this transformation makes the quantization of geometrical quantities less tractable such that two different ways are presented. It is shown that in both cases the spectrum of such geometrical operators depends on the initial value problem. Furthermore, we

  6. Simplicial quantum gravity

    International Nuclear Information System (INIS)

    Hartle, J.B.

    1985-01-01

    Simplicial approximation and the ideas associated with the Regge calculus provide a concrete way of implementing a sum over histories formulation of quantum gravity. A simplicial geometry is made up of flat simplices joined together in a prescribed way together with an assignment of lengths to their edges. A sum over simplicial geometries is a sum over the different ways the simplices can be joined together with an integral over their edge lengths. The construction of the simplicial Euclidean action for this approach to quantum general relativity is illustrated. The recovery of the diffeomorphism group in the continuum limit is discussed. Some possible classes of simplicial complexes with which to define a sum over topologies are described. In two dimensional quantum gravity it is argued that a reasonable class is the class of pseudomanifolds

  7. Instantons and gravity

    International Nuclear Information System (INIS)

    Konopleva, N.P.

    1996-01-01

    The problems of application of nonperturbative quantization methods in the theories of the gauge fields and gravity are discussed. Unification of interactions is considered in the framework of the geometrical gauge fields theory. Vacuum conception in the unified theory of interactions and instantons role in the vacuum structure are analyzed. The role of vacuum solutions of Einstein equations in definition of the gauge field vacuum is demonstrated

  8. Gravity, Time, and Lagrangians

    Science.gov (United States)

    Huggins, Elisha

    2010-01-01

    Feynman mentioned to us that he understood a topic in physics if he could explain it to a college freshman, a high school student, or a dinner guest. Here we will discuss two topics that took us a while to get to that level. One is the relationship between gravity and time. The other is the minus sign that appears in the Lagrangian. (Why would one…

  9. Spontaneously generated gravity

    International Nuclear Information System (INIS)

    Zee, A.

    1981-01-01

    We show, following a recent suggestion of Adler, that gravity may arise as a consequence of dynamical symmetry breaking in a scale- and gauge-invariant world. Our calculation is not tied to any specific scheme of dynamical symmetry breaking. A representation for Newton's coupling constant in terms of flat-space quantities is derived. The sign of Newton's coupling constant appears to depend on infrared details of the symmetry-breaking mechanism

  10. Loop Quantum Gravity.

    Science.gov (United States)

    Rovelli, Carlo

    2008-01-01

    The problem of describing the quantum behavior of gravity, and thus understanding quantum spacetime , is still open. Loop quantum gravity is a well-developed approach to this problem. It is a mathematically well-defined background-independent quantization of general relativity, with its conventional matter couplings. Today research in loop quantum gravity forms a vast area, ranging from mathematical foundations to physical applications. Among the most significant results obtained so far are: (i) The computation of the spectra of geometrical quantities such as area and volume, which yield tentative quantitative predictions for Planck-scale physics. (ii) A physical picture of the microstructure of quantum spacetime, characterized by Planck-scale discreteness. Discreteness emerges as a standard quantum effect from the discrete spectra, and provides a mathematical realization of Wheeler's "spacetime foam" intuition. (iii) Control of spacetime singularities, such as those in the interior of black holes and the cosmological one. This, in particular, has opened up the possibility of a theoretical investigation into the very early universe and the spacetime regions beyond the Big Bang. (iv) A derivation of the Bekenstein-Hawking black-hole entropy. (v) Low-energy calculations, yielding n -point functions well defined in a background-independent context. The theory is at the roots of, or strictly related to, a number of formalisms that have been developed for describing background-independent quantum field theory, such as spin foams, group field theory, causal spin networks, and others. I give here a general overview of ideas, techniques, results and open problems of this candidate theory of quantum gravity, and a guide to the relevant literature.

  11. Loop Quantum Gravity

    Directory of Open Access Journals (Sweden)

    Rovelli Carlo

    2008-07-01

    Full Text Available The problem of describing the quantum behavior of gravity, and thus understanding quantum spacetime, is still open. Loop quantum gravity is a well-developed approach to this problem. It is a mathematically well-defined background-independent quantization of general relativity, with its conventional matter couplings. Today research in loop quantum gravity forms a vast area, ranging from mathematical foundations to physical applications. Among the most significant results obtained so far are: (i The computation of the spectra of geometrical quantities such as area and volume, which yield tentative quantitative predictions for Planck-scale physics. (ii A physical picture of the microstructure of quantum spacetime, characterized by Planck-scale discreteness. Discreteness emerges as a standard quantum effect from the discrete spectra, and provides a mathematical realization of Wheeler’s “spacetime foam” intuition. (iii Control of spacetime singularities, such as those in the interior of black holes and the cosmological one. This, in particular, has opened up the possibility of a theoretical investigation into the very early universe and the spacetime regions beyond the Big Bang. (iv A derivation of the Bekenstein–Hawking black-hole entropy. (v Low-energy calculations, yielding n-point functions well defined in a background-independent context. The theory is at the roots of, or strictly related to, a number of formalisms that have been developed for describing background-independent quantum field theory, such as spin foams, group field theory, causal spin networks, and others. I give here a general overview of ideas, techniques, results and open problems of this candidate theory of quantum gravity, and a guide to the relevant literature.

  12. Semiclassical unimodular gravity

    International Nuclear Information System (INIS)

    Fiol, Bartomeu; Garriga, Jaume

    2010-01-01

    Classically, unimodular gravity is known to be equivalent to General Relativity (GR), except for the fact that the effective cosmological constant Λ has the status of an integration constant. Here, we explore various formulations of unimodular gravity beyond the classical limit. We first consider the non-generally covariant action formulation in which the determinant of the metric is held fixed to unity. We argue that the corresponding quantum theory is also equivalent to General Relativity for localized perturbative processes which take place in generic backgrounds of infinite volume (such as asymptotically flat spacetimes). Next, using the same action, we calculate semiclassical non-perturbative quantities, which we expect will be dominated by Euclidean instanton solutions. We derive the entropy/area ratio for cosmological and black hole horizons, finding agreement with GR for solutions in backgrounds of infinite volume, but disagreement for backgrounds with finite volume. In deriving the above results, the path integral is taken over histories with fixed 4-volume. We point out that the results are different if we allow the 4-volume of the different histories to vary over a continuum range. In this ''generalized'' version of unimodular gravity, one recovers the full set of Einstein's equations in the classical limit, including the trace, so Λ is no longer an integration constant. Finally, we consider the generally covariant theory due to Henneaux and Teitelboim, which is classically equivalent to unimodular gravity. In this case, the standard semiclassical GR results are recovered provided that the boundary term in the Euclidean action is chosen appropriately

  13. Granular Superconductors and Gravity

    Science.gov (United States)

    Noever, David; Koczor, Ron

    1999-01-01

    As a Bose condensate, superconductors provide novel conditions for revisiting previously proposed couplings between electromagnetism and gravity. Strong variations in Cooper pair density, large conductivity and low magnetic permeability define superconductive and degenerate condensates without the traditional density limits imposed by the Fermi energy (approx. 10(exp -6) g cu cm). Recent experiments have reported anomalous weight loss for a test mass suspended above a rotating Type II, YBCO superconductor, with a relatively high percentage change (0.05-2.1%) independent of the test mass' chemical composition and diamagnetic properties. A variation of 5 parts per 104 was reported above a stationary (non-rotating) superconductor. In experiments using a sensitive gravimeter, bulk YBCO superconductors were stably levitated in a DC magnetic field and exposed without levitation to low-field strength AC magnetic fields. Changes in observed gravity signals were measured to be less than 2 parts in 108 of the normal gravitational acceleration. Given the high sensitivity of the test, future work will examine variants on the basic magnetic behavior of granular superconductors, with particular focus on quantifying their proposed importance to gravity.

  14. Venus gravity fields

    Science.gov (United States)

    Sjogren, W. L.; Ananda, M.; Williams, B. G.; Birkeland, P. W.; Esposito, P. S.; Wimberly, R. N.; Ritke, S. J.

    1981-01-01

    Results of Pioneer Venus Orbiter observations concerning the gravity field of Venus are presented. The gravitational data was obtained from reductions of Doppler radio tracking data for the Orbiter, which is in a highly eccentric orbit with periapsis altitude varying from 145 to 180 km and nearly fixed periapsis latitude of 15 deg N. The global gravity field was obtained through the simultaneous estimation of the orbit state parameters and gravity coefficients from long-period variations in orbital element rates. The global field has been described with sixth degree and order spherical harmonic coefficients, which are capable of resolving the three major topographical features on Venus. Local anomalies have been mapped using line-of-sight accelerations derived from the Doppler residuals between 40 deg N and 10 deg S latitude at approximately 300 km spatial resolution. Gravitational data is observed to correspond to topographical data obtained by radar altimeter, with most of the gravitational anomalies about 20-30 milligals. Simulations evaluating the isostatic states of two topographic features indicate that at least partial isostasy prevails, with the possibility of complete compensation.

  15. Polar gravity fields from GOCE and airborne gravity

    DEFF Research Database (Denmark)

    Forsberg, René; Olesen, Arne Vestergaard; Yidiz, Hasan

    2011-01-01

    Airborne gravity, together with high-quality surface data and ocean satellite altimetric gravity, may supplement GOCE to make consistent, accurate high resolution global gravity field models. In the polar regions, the special challenge of the GOCE polar gap make the error characteristics...... of combination models especially sensitive to the correct merging of satellite and surface data. We outline comparisons of GOCE to recent airborne gravity surveys in both the Arctic and the Antarctic. The comparison is done to new 8-month GOCE solutions, as well as to a collocation prediction from GOCE gradients...... in Antarctica. It is shown how the enhanced gravity field solutions improve the determination of ocean dynamic topography in both the Arctic and in across the Drake Passage. For the interior of Antarctica, major airborne gravity programs are currently being carried out, and there is an urgent need...

  16. Grapevine rootstocks differentially affect the rate of ripening and modulate auxin-related genes in Cabernet Sauvignon berries

    Directory of Open Access Journals (Sweden)

    Massimiliano eCorso

    2016-02-01

    Full Text Available In modern viticulture, grafting commercial grapevine varieties on interspecific rootstocks is a common practice required for conferring resistance to many biotic and abiotic stresses. Nevertheless, the use of rootstocks to gain these essential traits is also known to impact grape berry development and quality, although the underlying mechanisms are still poorly understood. In grape berries, the onset of ripening (véraison is regulated by a complex network of mobile signals including hormones such as auxins, ethylene, abscisic acid and brassinosteroids. Recently, a new rootstock, designated M4, was selected based on its enhanced tolerance to water stress and medium vigour. This study investigates the effect of M4 on Cabernet Sauvignon (CS berry development in comparison to the commercial 1103P rootstock. Physical and biochemical parameters showed that the ripening rate of CS berries is faster when grafted onto M4. A multifactorial analysis performed on mRNA-Seq data obtained from skin and pulp of berries grown in both graft combinations revealed that genes controlling auxin action (ARF and Aux/IAA represent one of main categories affected by the rootstock genotype. Considering that the level of auxin tightly regulates the transcription of these genes, we investigated the behaviour of the main gene families involved in auxin biosynthesis and conjugation. Molecular and biochemical analyses confirmed a link between the rate of berry development and the modulation of auxin metabolism. Moreover the data indicate that this phenomenon appears to be particularly pronounced in skin tissue in comparison to the flesh.

  17. Grapevine Rootstocks Differentially Affect the Rate of Ripening and Modulate Auxin-Related Genes in Cabernet Sauvignon Berries.

    Science.gov (United States)

    Corso, Massimiliano; Vannozzi, Alessandro; Ziliotto, Fiorenza; Zouine, Mohamed; Maza, Elie; Nicolato, Tommaso; Vitulo, Nicola; Meggio, Franco; Valle, Giorgio; Bouzayen, Mondher; Müller, Maren; Munné-Bosch, Sergi; Lucchin, Margherita; Bonghi, Claudio

    2016-01-01

    In modern viticulture, grafting commercial grapevine varieties on interspecific rootstocks is a common practice required for conferring resistance to many biotic and abiotic stresses. Nevertheless, the use of rootstocks to gain these essential traits is also known to impact grape berry development and quality, although the underlying mechanisms are still poorly understood. In grape berries, the onset of ripening (véraison) is regulated by a complex network of mobile signals including hormones such as auxins, ethylene, abscisic acid, and brassinosteroids. Recently, a new rootstock, designated M4, was selected based on its enhanced tolerance to water stress and medium vigor. This study investigates the effect of M4 on Cabernet Sauvignon (CS) berry development in comparison to the commercial 1103P rootstock. Physical and biochemical parameters showed that the ripening rate of CS berries is faster when grafted onto M4. A multifactorial analysis performed on mRNA-Seq data obtained from skin and pulp of berries grown in both graft combinations revealed that genes controlling auxin action (ARF and Aux/IAA) represent one of main categories affected by the rootstock genotype. Considering that the level of auxin tightly regulates the transcription of these genes, we investigated the behavior of the main gene families involved in auxin biosynthesis and conjugation. Molecular and biochemical analyses confirmed a link between the rate of berry development and the modulation of auxin metabolism. Moreover, the data indicate that this phenomenon appears to be particularly pronounced in skin tissue in comparison to the flesh.

  18. Genome-Wide Characterization and Expression Profiling of the AUXIN RESPONSE FACTOR (ARF) Gene Family in Eucalyptus grandis

    Science.gov (United States)

    Yu, Hong; Soler, Marçal; Mila, Isabelle; San Clemente, Hélène; Savelli, Bruno; Dunand, Christophe; Paiva, Jorge A. P.; Myburg, Alexander A.; Bouzayen, Mondher; Grima-Pettenati, Jacqueline; Cassan-Wang, Hua

    2014-01-01

    Auxin is a central hormone involved in a wide range of developmental processes including the specification of vascular stem cells. Auxin Response Factors (ARF) are important actors of the auxin signalling pathway, regulating the transcription of auxin-responsive genes through direct binding to their promoters. The recent availability of the Eucalyptus grandis genome sequence allowed us to examine the characteristics and evolutionary history of this gene family in a woody plant of high economic importance. With 17 members, the E. grandis ARF gene family is slightly contracted, as compared to those of most angiosperms studied hitherto, lacking traces of duplication events. In silico analysis of alternative transcripts and gene truncation suggested that these two mechanisms were preeminent in shaping the functional diversity of the ARF family in Eucalyptus. Comparative phylogenetic analyses with genomes of other taxonomic lineages revealed the presence of a new ARF clade found preferentially in woody and/or perennial plants. High-throughput expression profiling among different organs and tissues and in response to environmental cues highlighted genes expressed in vascular cambium and/or developing xylem, responding dynamically to various environmental stimuli. Finally, this study allowed identification of three ARF candidates potentially involved in the auxin-regulated transcriptional program underlying wood formation. PMID:25269088

  19. Genome-wide characterization and expression profiling of the AUXIN RESPONSE FACTOR (ARF gene family in Eucalyptus grandis.

    Directory of Open Access Journals (Sweden)

    Hong Yu

    Full Text Available Auxin is a central hormone involved in a wide range of developmental processes including the specification of vascular stem cells. Auxin Response Factors (ARF are important actors of the auxin signalling pathway, regulating the transcription of auxin-responsive genes through direct binding to their promoters. The recent availability of the Eucalyptus grandis genome sequence allowed us to examine the characteristics and evolutionary history of this gene family in a woody plant of high economic importance. With 17 members, the E. grandis ARF gene family is slightly contracted, as compared to those of most angiosperms studied hitherto, lacking traces of duplication events. In silico analysis of alternative transcripts and gene truncation suggested that these two mechanisms were preeminent in shaping the functional diversity of the ARF family in Eucalyptus. Comparative phylogenetic analyses with genomes of other taxonomic lineages revealed the presence of a new ARF clade found preferentially in woody and/or perennial plants. High-throughput expression profiling among different organs and tissues and in response to environmental cues highlighted genes expressed in vascular cambium and/or developing xylem, responding dynamically to various environmental stimuli. Finally, this study allowed identification of three ARF candidates potentially involved in the auxin-regulated transcriptional program underlying wood formation.

  20. Gravity signatures of terrane accretion

    Science.gov (United States)

    Franco, Heather; Abbott, Dallas

    1999-01-01

    In modern collisional environments, accreted terranes are bracketed by forearc gravity lows, a gravitational feature which results from the abandonment of the original trench and the initiation of a new trench seaward of the accreted terrane. The size and shape of the gravity low depends on the type of accreted feature and the strength of the formerly subducting plate. Along the Central American trench, the accretion of Gorgona Island caused a seaward trench jump of 48 to 66 km. The relict trench axes show up as gravity lows behind the trench with minimum values of -78 mgal (N of Gorgona) and -49 mgal (S of Gorgona) respectively. These forearc gravity lows have little or no topographic expression. The active trench immediately seaward of these forearc gravity lows has minimum gravity values of -59 mgal (N of Gorgona) and -58 mgal (S of Gorgona), respectively. In the north, the active trench has a less pronounced gravity low than the sediment covered forearc. In the Mariana arc, two Cretaceous seamounts have been accreted to the Eocene arc. The northern seamount is most likely a large block, the southern seamount may be a thrust slice. These more recent accretion events have produced modest forearc topographic and gravity lows in comparison with the topographic and gravity lows within the active trench. However, the minimum values of the Mariana forearc gravity lows are modest only by comparison to the Mariana Trench (-216 mgal); their absolute values are more negative than at Gorgona Island (-145 to -146 mgal). We speculate that the forearc gravity lows and seaward trench jumps near Gorgona Island were produced by the accretion of a hotspot island from a strong plate. The Mariana gravity lows and seaward trench jumps (or thrust slices) were the result of breaking a relatively weak plate close to the seamount edifice. These gravity lows resulting from accretion events should be preserved in older accreted terranes.

  1. Development of Erect Leaves in a Modern Maize Hybrid is Associated with Reduced Responsiveness to Auxin and Light of Young Seedlings in vitro

    Czech Academy of Sciences Publication Activity Database

    Fellner, Martin; Ford, E.D.; Van Volkenburgh, E.

    2006-01-01

    Roč. 1, č. 4 (2006), s. 201-211 ISSN 1559-2316 R&D Projects: GA MŠk 1P05ME792 Institutional research plan: CEZ:AV0Z50380511 Keywords : auxin * auxin-binding protein * growth * leaf angle * light * maize Subject RIV: EF - Botanics

  2. Auxin-cytokinin synergism in vitro for producing genetically stable plants of Ruta graveolens using shoot tip meristems

    Directory of Open Access Journals (Sweden)

    Mohammad Faisal

    2018-02-01

    Full Text Available An efficient micropropagation protocol was developed for Ruta graveolens Linn. using shoot tip meristems derived from a 4-month-old field grown plant. In vitro shoot regeneration and proliferation was accomplished on Murashige and Skoogs (MS semi-solid medium in addition to different doses of cytokinins viz.6- benzyl adenine (BA, Kinetin (Kn or 2-isopetynyl adenine (2iP, singly or in combination with auxins viz. indole-3-acetic acid (IAA, indole-3-butyric acid (IBA or α-naphthalene acetic acid (NAA. Highest regeneration frequency (27.6% was obtained on (MS medium composed of BA (10 µM with maximum number (9.4 of shoots and 4.3 cm shoot length after 4 weeks of incubation. Among various combinations tried best regeneration frequency (71% of multiple shoot formation with highest number (12.6 of shoots per shoot tip explants were achieved in MS medium augmented with a combination BA (10.0 µM and NAA (2.5 µM after 4 weeks of incubation. The optimum frequency (97% of rhizogenesis was achieved on half-strength MS medium having 0.5 µM IBA after 4 weeks of incubation. Tissue culture raised plantlets with 5–7 fully opened leaves with healthy root system were successfully acclimatized off in Soilrite™ with 80% survival rate followed by transportation to normal soil under natural light. Genetic stability among in vitro raised progeny was evaluated by ISSR and RAPD markers. The entire banding pattern revealed from in vitro regenerated plants was monomorphic to the donor. The present protocol provides an alternative option for commercial propagation and fruitful setting up of genetically uniform progeny for sustainable utilization and germplasm preservation.

  3. Cosmological tests of modified gravity.

    Science.gov (United States)

    Koyama, Kazuya

    2016-04-01

    We review recent progress in the construction of modified gravity models as alternatives to dark energy as well as the development of cosmological tests of gravity. Einstein's theory of general relativity (GR) has been tested accurately within the local universe i.e. the Solar System, but this leaves the possibility open that it is not a good description of gravity at the largest scales in the Universe. This being said, the standard model of cosmology assumes GR on all scales. In 1998, astronomers made the surprising discovery that the expansion of the Universe is accelerating, not slowing down. This late-time acceleration of the Universe has become the most challenging problem in theoretical physics. Within the framework of GR, the acceleration would originate from an unknown dark energy. Alternatively, it could be that there is no dark energy and GR itself is in error on cosmological scales. In this review, we first give an overview of recent developments in modified gravity theories including f(R) gravity, braneworld gravity, Horndeski theory and massive/bigravity theory. We then focus on common properties these models share, such as screening mechanisms they use to evade the stringent Solar System tests. Once armed with a theoretical knowledge of modified gravity models, we move on to discuss how we can test modifications of gravity on cosmological scales. We present tests of gravity using linear cosmological perturbations and review the latest constraints on deviations from the standard [Formula: see text]CDM model. Since screening mechanisms leave distinct signatures in the non-linear structure formation, we also review novel astrophysical tests of gravity using clusters, dwarf galaxies and stars. The last decade has seen a number of new constraints placed on gravity from astrophysical to cosmological scales. Thanks to on-going and future surveys, cosmological tests of gravity will enjoy another, possibly even more, exciting ten years.

  4. Comparative effects of auxin and abscisic acid on growth, hydrogen ion efflux and gravitropism in primary roots of maize

    Science.gov (United States)

    Evans, M. L.; Mulkey, T. J.

    1984-01-01

    In order to test the idea that auxin action on root growth may be mediated by H(+) movement, the correlation of auxin action on growth and H(+) movement in roots was examined along with changes in H(+) efflux patterns associated with the asymmetric growth which occurs during gravitropism. The effects of indoleacetic acid (IAA) and abscisic acid (AbA) on growth, H(+) secretion, and gravitropism in roots were compared. Results show a close correlation existent between H(+) efflux and growth in maize roots. In intact roots there is strong H(+) efflux from the elongation zone. Growth-promoting concentrations of IAA stimulate H(+) efflux. During gravitropism the H(+) efflux from the elongation zone becomes asymmetric; the evidence indicates that auxin redistribution contributes to the development of acid efflux asymmetry. That AbA stimulates root growth is reflected in its ability to stimulate H(+) efflux from apical root segments.

  5. Isolation and screening of rhizobia for auxin biosynthesis and growth promotion of mung bean (Vigna radiata L. seedlings under axenic conditions

    Directory of Open Access Journals (Sweden)

    Muhammad Ashfaq Anjum, Zahir Ahmad Zahir, Muhammad Arshad and Muhammad Ashraf

    2011-04-01

    Full Text Available A series of screening experiments to evaluate the effectiveness of rhizobia for producing auxins and improvegrowth and nodulation of mungbean (Vigna radiata L. were carried out under axenic conditions. Forty fouriolatess of rhizobia were isolated using standard procedures. Auxin biosynthesis by these rhizobial isolates wasdetermined in the absence and presence of L-Trp, a physiological precursor of auxins. Rhizobial isolates variedwidely in auxins biosynthesis capabilities. On the basis of auxins biosynthesis, a pouch experiment was conductedfor screening thirty four efficient isolates of rhizobia for the growth promotion of mung bean. Results of pouch studyshowed that inoculation with selected rhizobial isolates increased the root /shoot length, fresh, and dry shoot weightof mung bean up to 33, 59, 71, 148, 107 and 188%, respectively, over untreated control. Further studies are neededunder glasshouse and field conditions for confirmation of these results.

  6. Bringing Gravity to Space

    Science.gov (United States)

    Norsk, P.; Shelhamer, M.

    2016-01-01

    This panel will present NASA's plans for ongoing and future research to define the requirements for Artificial Gravity (AG) as a countermeasure against the negative health effects of long-duration weightlessness. AG could mitigate the gravity-sensitive effects of spaceflight across a host of physiological systems. Bringing gravity to space could mitigate the sensorimotor and neuro-vestibular disturbances induced by G-transitions upon reaching a planetary body, and the cardiovascular deconditioning and musculoskeletal weakness induced by weightlessness. Of particular interest for AG during deep-space missions is mitigation of the Visual Impairment Intracranial Pressure (VIIP) syndrome that the majority of astronauts exhibit in space to varying degrees, and which presumably is associated with weightlessness-induced fluid shift from lower to upper body segments. AG could be very effective for reversing the fluid shift and thus help prevent VIIP. The first presentation by Dr. Charles will summarize some of the ground-based and (very little) space-based research that has been conducted on AG by the various space programs. Dr. Paloski will address the use of AG during deep-space exploration-class missions and describe the different AG scenarios such as intra-vehicular, part-of-vehicle, or whole-vehicle centrifugations. Dr. Clement will discuss currently planned NASA research as well as how to coordinate future activities among NASA's international partners. Dr. Barr will describe some possible future plans for using space- and ground-based partial-G analogs to define the relationship between physiological responses and G levels between 0 and 1. Finally, Dr. Stenger will summarize how the human cardiovascular system could benefit from intermittent short-radius centrifugations during long-duration missions.

  7. Is Gravity an Entropic Force?

    Directory of Open Access Journals (Sweden)

    Shan Gao

    2011-04-01

    Full Text Available The remarkable connections between gravity and thermodynamics seem to imply that gravity is not fundamental but emergent, and in particular, as Verlinde suggested, gravity is probably an entropic force. In this paper, we will argue that the idea of gravity as an entropic force is debatable. It is shown that there is no convincing analogy between gravity and entropic force in Verlinde’s example. Neither holographic screen nor test particle satisfies all requirements for the existence of entropic force in a thermodynamics system. Furthermore, we show that the entropy increase of the screen is not caused by its statistical tendency to increase entropy as required by the existence of entropic force, but in fact caused by gravity. Therefore, Verlinde’s argument for the entropic origin of gravity is problematic. In addition, we argue that the existence of a minimum size of spacetime, together with the Heisenberg uncertainty principle in quantum theory, may imply the fundamental existence of gravity as a geometric property of spacetime. This may provide a further support for the conclusion that gravity is not an entropic force.

  8. Active Response Gravity Offload System

    Science.gov (United States)

    Valle, Paul; Dungan, Larry; Cunningham, Thomas; Lieberman, Asher; Poncia, Dina

    2011-01-01

    The Active Response Gravity Offload System (ARGOS) provides the ability to simulate with one system the gravity effect of planets, moons, comets, asteroids, and microgravity, where the gravity is less than Earth fs gravity. The system works by providing a constant force offload through an overhead hoist system and horizontal motion through a rail and trolley system. The facility covers a 20 by 40-ft (approximately equals 6.1 by 12.2m) horizontal area with 15 ft (approximately equals4.6 m) of lifting vertical range.

  9. Teleparallel equivalent of Lovelock gravity

    Science.gov (United States)

    González, P. A.; Vásquez, Yerko

    2015-12-01

    There is a growing interest in modified gravity theories based on torsion, as these theories exhibit interesting cosmological implications. In this work inspired by the teleparallel formulation of general relativity, we present its extension to Lovelock gravity known as the most natural extension of general relativity in higher-dimensional space-times. First, we review the teleparallel equivalent of general relativity and Gauss-Bonnet gravity, and then we construct the teleparallel equivalent of Lovelock gravity. In order to achieve this goal, we use the vielbein and the connection without imposing the Weitzenböck connection. Then, we extract the teleparallel formulation of the theory by setting the curvature to null.

  10. The gravity apple tree

    International Nuclear Information System (INIS)

    Aldama, Mariana Espinosa

    2015-01-01

    The gravity apple tree is a genealogical tree of the gravitation theories developed during the past century. The graphic representation is full of information such as guides in heuristic principles, names of main proponents, dates and references for original articles (See under Supplementary Data for the graphic representation). This visual presentation and its particular classification allows a quick synthetic view for a plurality of theories, many of them well validated in the Solar System domain. Its diachronic structure organizes information in a shape of a tree following similarities through a formal concept analysis. It can be used for educational purposes or as a tool for philosophical discussion. (paper)

  11. Diversification, phylogeny and evolution of auxin response factor (ARF) family: insights gained from analyzing maize ARF genes.

    Science.gov (United States)

    Wang, Yijun; Deng, Dexiang; Shi, Yating; Miao, Nan; Bian, Yunlong; Yin, Zhitong

    2012-03-01

    Auxin response factors (ARFs), member of the plant-specific B3 DNA binding superfamily, target specifically to auxin response elements (AuxREs) in promoters of primary auxin-responsive genes and heterodimerize with Aux/IAA proteins in auxin signaling transduction cascade. In previous research, we have isolated and characterized maize Aux/IAA genes in whole-genome scale. Here, we report the comprehensive analysis of ARF genes in maize. A total of 36 ARF genes were identified and validated from the B73 maize genome through an iterative strategy. Thirty-six maize ARF genes are distributed in all maize chromosomes except chromosome 7. Maize ARF genes expansion is mainly due to recent segmental duplications. Maize ARF proteins share one B3 DNA binding domain which consists of seven-stranded β sheets and two short α helixes. Twelve maize ARFs with glutamine-rich middle regions could be as activators in modulating expression of auxin-responsive genes. Eleven maize ARF proteins are lack of homo- and heterodimerization domains. Putative cis-elements involved in phytohormones and light signaling responses, biotic and abiotic stress adaption locate in promoters of maize ARF genes. Expression patterns vary greatly between clades and sister pairs of maize ARF genes. The B3 DNA binding and auxin response factor domains of maize ARF proteins are primarily subjected to negative selection during selective sweep. The mixed selective forces drive the diversification and evolution of genomic regions outside of B3 and ARF domains. Additionally, the dicot-specific proliferation of ARF genes was detected. Comparative genomics analysis indicated that maize, sorghum and rice duplicate chromosomal blocks containing ARF homologs are highly syntenic. This study provides insights into the distribution, phylogeny and evolution of ARF gene family.

  12. Dual DNA binding property of ABA insensitive 3 like factors targeted to promoters responsive to ABA and auxin.

    Science.gov (United States)

    Nag, Ronita; Maity, Manas Kanti; Dasgupta, Maitrayee

    2005-11-01

    The ABA responsive ABI3 and the auxin responsive ARF family of transcription factors bind the CATGCATG (Sph) and TGTCTC core motifs in ABA and auxin response elements (ABRE and AuxRE), respectively. Several evidences indicate ABI3s to act downstream to auxin too. Because DNA binding domain of ABI3s shows significant overlap with ARFs we enquired whether auxin responsiveness through ABI3s could be mediated by their binding to canonical AuxREs. Investigations were undertaken through in vitro gel mobility shift assays (GMSA) using the DNA binding domain B3 of PvAlf (Phaseolus vulgaris ABI3 like factor) and upstream regions of auxin responsive gene GH3 (-267 to -141) and ABA responsive gene Em (-316 to -146) harboring AuxRE and ABRE, respectively. We demonstrate that B3 domain of PvAlf could bind AuxRE only when B3 was associated with its flanking domain B2 (B2B3). Such strict requirement of B2 domain was not observed with ABRE, where B3 could bind with or without being associated with B2. This dual specificity in DNA binding of ABI3s was also demonstrated with nuclear extracts of cultured cells of Arachis hypogea. Supershift analysis of ABRE and AuxRE bound nuclear proteins with antibodies raised against B2B3 domains of PvAlf revealed that ABI3 associated complexes were detectable in association with both cis elements. Competition GMSA confirmed the same complexes to bind ABRE and AuxRE. This dual specificity of ABI3 like factors in DNA binding targeted to natural promoters responsive to ABA and auxin suggests them to have a potential role in conferring crosstalk between these two phytohormones.

  13. Airborne Gravity: NGS' Gravity Data for AN05 (2011)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Airborne gravity data for Alaska collected in 2011 over 1 survey. This data set is part of the Gravity for the Re-definition of the American Vertical Datum (GRAV-D)...

  14. Airborne Gravity: NGS' Gravity Data for AN06 (2011)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Airborne gravity data for Alaska collected in 2011 over 1 survey. This data set is part of the Gravity for the Re-definition of the American Vertical Datum (GRAV-D)...

  15. Airborne Gravity: NGS' Gravity Data for CS08 (2015)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Airborne gravity data for CS08 collected in 2006 over 1 survey. This data set is part of the Gravity for the Re-definition of the American Vertical Datum (GRAV-D)...

  16. Airborne Gravity: NGS' Gravity Data for AS02 (2010)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Airborne gravity data for Alaska collected in 2010 over 2 surveys. This data set is part of the Gravity for the Re-definition of the American Vertical Datum (GRAV-D)...

  17. Airborne Gravity: NGS' Gravity Data for ES02 (2013)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Airborne gravity data for Florida and the Gulf of Mexico collected in 2013 over 1 survey. This data set is part of the Gravity for the Re-definition of the American...

  18. Airborne Gravity: NGS' Gravity Data for AN04 (2010)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Airborne gravity data for Alaska collected in 2010 over 1 survey. This data set is part of the Gravity for the Re-definition of the American Vertical Datum (GRAV-D)...

  19. Airborne Gravity: NGS' Gravity Data for CS05 (2014)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Airborne gravity data for Texas collected in 2014 over 2 surveys. This data set is part of the Gravity for the Re-definition of the American Vertical Datum (GRAV-D)...

  20. Airborne Gravity: NGS' Gravity Data for CS07 (2014 & 2016)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Airborne gravity data for Texas collected in 2014 & 2016 over 3 surveys,TX14-2, TX16-1 and TX16-2. This data set is part of the Gravity for the Re-definition of...