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Sample records for leaf elongation zone

  1. Characterization of Fructan from Mature Leaf Blades and Elongation Zones of Developing Leaf Blades of Wheat, Tall Fescue, and Timothy 1

    PubMed Central

    Spollen, William G.; Nelson, Curtis J.

    1988-01-01

    Water-soluble carbohydrate composition of mature (ceased expanding) leaf blades and the elongation zone of developing leaf blades was characterized in wheat (Triticum aestivum L.), tall fescue (Festuca arundinacea Schreb.), and timothy (Phleum pratense L.). These species were chosen because they differ in mean degree of polymerization (DP) of fructan in the mature leaf blade. Our objective was to compare the nature and DP of the fructan. Vegetative plants were grown with a 14-hour photoperiod and constant 21°C at the leaf base. Gel permeation chromatography of leaf blade extracts showed that the apparent mean fructan DP increased in the order wheat < tall fescue < timothy. Apparent mean DP of elongation zone fructan was higher than that of leaf blade fructan in wheat and timothy, but the reverse occurred for tall fescue. Low DP (≤10) and high DP (>10) pools were found in both tissues of tall fescue and wheat, but concentration of low DP fructan was very low in either tissue of timothy. All three species have high DP fructan. Comigration with standards on thin-layer chromotography showed that wheat contained 1-kestose and a noninulin fructan oligomer series. Tall fescue contained neokestose, 1-kestose and higher oligosaccharides that comigrated with neokestose-based compounds and inulins. Thin-layer chromatography showed that small amounts of fructose-containing oligosaccharides were present in timothy. Images Fig. 2 Fig. 3 PMID:16666465

  2. Transition zone cells reach G2 phase before initiating elongation in maize root apex.

    PubMed

    Alarcón, M Victoria; Salguero, Julio

    2017-06-15

    Root elongation requires cell divisions in the meristematic zone and cell elongation in the elongation zone. The boundary between dividing and elongating cells is called the transition zone. In the meristem zone, initial cells are continuously dividing, but on the basal side of the meristem cells exit the meristem through the transition zone and enter in the elongation zone, where they stop division and rapidly elongate. Throughout this journey cells are accompanied by changes in cell cycle progression. Flow cytometry analysis showed that meristematic cells are in cycle, but exit when they enter the elongation zone. In addition, the percentage of cells in G2 phase (4C) strongly increased from the meristem to the elongation zone. However, we did not observe remarkable changes in the percentage of cells in cell cycle phases along the entire elongation zone. These results suggest that meristematic cells in maize root apex stop the cell cycle in G2 phase after leaving the meristem. © 2017. Published by The Company of Biologists Ltd.

  3. Leaf Length Tracker: a novel approach to analyse leaf elongation close to the thermal limit of growth in the field.

    PubMed

    Nagelmüller, Sebastian; Kirchgessner, Norbert; Yates, Steven; Hiltpold, Maya; Walter, Achim

    2016-03-01

    Leaf growth in monocot crops such as wheat and barley largely follows the daily temperature course, particularly under cold but humid springtime field conditions. Knowledge of the temperature response of leaf extension, particularly variations close to the thermal limit of growth, helps define physiological growth constraints and breeding-related genotypic differences among cultivars. Here, we present a novel method, called 'Leaf Length Tracker' (LLT), suitable for measuring leaf elongation rates (LERs) of cereals and other grasses with high precision and high temporal resolution under field conditions. The method is based on image sequence analysis, using a marker tracking approach to calculate LERs. We applied the LLT to several varieties of winter wheat (Triticum aestivum), summer barley (Hordeum vulgare), and ryegrass (Lolium perenne), grown in the field and in growth cabinets under controlled conditions. LLT is easy to use and we demonstrate its reliability and precision under changing weather conditions that include temperature, wind, and rain. We found that leaf growth stopped at a base temperature of 0°C for all studied species and we detected significant genotype-specific differences in LER with rising temperature. The data obtained were statistically robust and were reproducible in the tested environments. Using LLT, we were able to detect subtle differences (sub-millimeter) in leaf growth patterns. This method will allow the collection of leaf growth data in a wide range of future field experiments on different graminoid species or varieties under varying environmental or treatment conditions.

  4. Leaf Length Tracker: a novel approach to analyse leaf elongation close to the thermal limit of growth in the field

    PubMed Central

    Kirchgessner, Norbert; Yates, Steven; Hiltpold, Maya; Walter, Achim

    2016-01-01

    Leaf growth in monocot crops such as wheat and barley largely follows the daily temperature course, particularly under cold but humid springtime field conditions. Knowledge of the temperature response of leaf extension, particularly variations close to the thermal limit of growth, helps define physiological growth constraints and breeding-related genotypic differences among cultivars. Here, we present a novel method, called ‘Leaf Length Tracker’ (LLT), suitable for measuring leaf elongation rates (LERs) of cereals and other grasses with high precision and high temporal resolution under field conditions. The method is based on image sequence analysis, using a marker tracking approach to calculate LERs. We applied the LLT to several varieties of winter wheat (Triticum aestivum), summer barley (Hordeum vulgare), and ryegrass (Lolium perenne), grown in the field and in growth cabinets under controlled conditions. LLT is easy to use and we demonstrate its reliability and precision under changing weather conditions that include temperature, wind, and rain. We found that leaf growth stopped at a base temperature of 0°C for all studied species and we detected significant genotype-specific differences in LER with rising temperature. The data obtained were statistically robust and were reproducible in the tested environments. Using LLT, we were able to detect subtle differences (sub-millimeter) in leaf growth patterns. This method will allow the collection of leaf growth data in a wide range of future field experiments on different graminoid species or varieties under varying environmental or treatment conditions. PMID:26818912

  5. Is elongation-induced leaf emergence beneficial for submerged Rumex species?

    PubMed Central

    Pierik, R.; van Aken, J. M.; Voesenek, L. A. C. J.

    2009-01-01

    Background and Aims Plant species from various taxa ‘escape’ from low oxygen conditions associated with submergence by a suite of traits collectively called the low oxygen escape syndrome (LOES). The expression of these traits is associated with costs and benefits. Thus far, remarkably few studies have dealt with the expected benefits of the LOES. Methods Young plants were fully submerged at initial depths of 450 mm (deep) or 150–240 mm (shallow). Rumex palustris leaf tips emerged from the shallow flooding within a few days, whereas a slight lowering of shallow flooding was required to expose R. acetosa leaf tips to the atmosphere. Shoot biomass and petiole porosity were measured for all species, and treatments and data from the deep and shallow submergence treatments were compared with non-flooded controls. Key Results R. palustris is characterized by submergence-induced enhanced petiole elongation. R. acetosa lacked this growth response. Upon leaf tip emergence, R. palustris increased its biomass, whereas R. acetosa did not. Furthermore, petiole porosity in R. palustris was twice as high as in R. acetosa. Conclusions Leaf emergence restores gas exchange between roots and the atmosphere in R. palustris. This occurs to a much lesser extent in R. acetosa and is attributable to its lower petiole porosity and therefore limited internal gas transport. Leaf emergence resulting from fast petiole elongation appears to benefit biomass accumulation if these plants contain sufficient aerenchyma in petioles and roots to facilitate internal gas exchange. PMID:18697756

  6. Gibberellic acid and dwarfism effects on the growth dynamics of B73 maize (Zea mays L.) leaf blades: a transient increase in apoplastic peroxidase activity precedes cessation of cell elongation.

    PubMed

    de Souza, I R; MacAdam, J W

    2001-08-01

    The relationship between apoplastic peroxidase (EC 1.11.1.7) activity and cessation of growth in maize (Zea mays L.) leaf blades was investigated by altering elongation zone length. Apoplastic peroxidase activity in the elongation and secondary cell wall deposition zones of elongating leaf blades of the maize inbred line B73 was used as a control and compared to leaves of the dwarf mutant D8-81127, a near-isogenic line of B73 unresponsive to gibberellins, and to leaves of B73 plants to which gibberellic acid (GA(3)) had been applied via root uptake. Elongation zone length was increased by treatment with GA(3) through an increase in cell number as well as increased final cell length. The shorter elongation zone of dwarf leaves occurred primarily through reduced final cell length. Although elongation zone length differed among dwarf, control, and GA(3)-treated leaf blades, in all three treatments a transient increase in apoplastic peroxidase activity preceded a reduction in the segmental elongation rate in leaves. A peroxidase isoenzyme with pI 7.0 occurred in the leaf elongation zone during growth deceleration in all three treatments, and its activity decreased as growth displaced tissue into the region of secondary cell wall deposition. Growth cessation for all treatments coincided with the first appearance of peroxidase isozymes with pIs of 5.6 and 5.7. Based on the activity of particular isozymes relative to growth and differentiation, the pI 7.0 isoenzyme is most likely to be involved in cessation of cell elongation, while isozymes with pIs 5.6 and 5.7 are likely to be active in lignification.

  7. Rapid changes in leaf elongation, ABA and water status during the recovery phase following application of water stress in two durum wheat varieties differing in drought tolerance.

    PubMed

    Mahdid, Mohamed; Kameli, Abdelkrim; Ehlert, Christina; Simonneau, Thierry

    2011-10-01

    This study aims to investigate the role of Abscisic acid (ABA) in water potential and turgor variations as well as growth recovery during the first phase of a rapid water stress induced by PEG6000. Two wheat varieties (Triticum durum L.), MBB (more tolerant) and OZ (less productive under drought), were grown in aerated nutrient solutions. Leaf elongation kinetics of the growing leaf 3 was estimated using LVDT. Water potential was measured using a pressure chamber; osmotic potential was estimated from expressed sap of elongation zone, turgor pressure of the same zone of leaf three was estimated directly by pressure probe. Growth rapidly ceased for a period of about one hour after the addition of PEG, gradual recovery was then observed for about 2 h. A significant difference was found in the % recovery of Leaf Elongation Rate (LER) and ABA between the two varieties, leading to better water status in MBB compared to OZ. The results of this study showed the possible role of ABA on growth resumption by the increase of relative water content and turgor via osmotic adjustment during the stress period in the leaves, which indicates the importance of OA in the resumption of LER even in the short term under conditions of water deficit. Full recovery of turgor but not of LER at the end stress period suggested the possible effect on cell wall extensibility (hardening) even at short term resulting from the rapid accumulation of ABA.

  8. The boundary of the meristematic and elongation zones in roots: endoreduplication precedes rapid cell expansion.

    PubMed

    Hayashi, Kohma; Hasegawa, Junko; Matsunaga, Sachihiro

    2013-10-14

    Plant roots consist of a meristematic zone of mitotic cells and an elongation zone of rapidly expanding cells, in which DNA replication often occurs without cell division, a process known as endoreduplication. The duration of the cell cycle and DNA replication, as measured by 5-ethynyl-2'-deoxy-uridine (EdU) incorporation, differed between the two regions (17 h in the meristematic zone, 30 h in the elongation zone). Two distinct subnuclear patterns of EdU signals, whole and speckled, marked nuclei undergoing DNA replication at early and late S phase, respectively. The boundary region between the meristematic and elongation zones was analysed by a combination of DNA replication imaging and optical estimation of the amount of DNA in each nucleus (C-value). We found a boundary cell with 4C nuclei exhibiting the whole pattern of EdU signals. Analyses of cells in the boundary region revealed that endoreduplication precedes rapid cell elongation in roots.

  9. Movement of endogenous calcium in the elongating zone of graviresponding roots of Zea mays

    NASA Technical Reports Server (NTRS)

    Moore, R.; Cameron, I. L.; Smith, N. K.

    1989-01-01

    Endogenous calcium (Ca) accumulates along the lower side of the elongating zone of horizontally oriented roots of Zea mays cv. Yellow Dent. This accumulation of Ca correlates positively with the onset of gravicurvature, and occurs in the cytoplasm, cell walls and mucilage of epidermal cells. Corresponding changes in endogenous Ca do not occur in cortical cells of the elongating zone of intact roots. These results indicate that the calcium asymmetries associated with root gravicurvature occur in the outermost layers of the root.

  10. Movement of endogenous calcium in the elongating zone of graviresponding roots of Zea mays

    NASA Technical Reports Server (NTRS)

    Moore, R.; Cameron, I. L.; Smith, N. K.

    1989-01-01

    Endogenous calcium (Ca) accumulates along the lower side of the elongating zone of horizontally oriented roots of Zea mays cv. Yellow Dent. This accumulation of Ca correlates positively with the onset of gravicurvature, and occurs in the cytoplasm, cell walls and mucilage of epidermal cells. Corresponding changes in endogenous Ca do not occur in cortical cells of the elongating zone of intact roots. These results indicate that the calcium asymmetries associated with root gravicurvature occur in the outermost layers of the root.

  11. Polar transport of 45Ca2+ across the elongation zone of gravistimulated roots

    NASA Technical Reports Server (NTRS)

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

    1985-01-01

    The movement of calcium across the elongation zone of gravistimulated primary roots of maize (Zea mays L.) was measured using 45Ca2+. Radioactive calcium was applied to one side of the elongation zone about 4 mm back from the root tip and the distribution of radioactivity across the root in the region of application was determined using scintillation spectrometry. The movement of 45Ca2+ across the elongation zone was non-polar in vertically oriented roots. In gravistimulated roots the movement of label was polarized with about twice as much label moving from top to bottom as from bottom to top. A variety of treatments which interfere with gravitropism was found to eliminate the polar movement of 45Ca2+ across the elongation zone. In maize cultivars which require light for gravitropic competency, dark grown roots exhibited neither gravitropism nor polar movement of 45Ca2+ across the elongation zone. Upon illumination the roots developed but gravitropic competency and gravity-induced polar movement of 45Ca2+ across the elongation zone. Similarly, roots of light-grown seedlings lost both gravitropic competency and 45Ca2+ transport polarity upon transfer to the dark. The results indicate a close correlation between calcium movement and gravitropism in primary roots in maize.

  12. Polar transport of 45Ca2+ across the elongation zone of gravistimulated roots.

    PubMed

    Lee, J S; Evans, M L

    1985-01-01

    The movement of calcium across the elongation zone of gravistimulated primary roots of maize (Zea mays L.) was measured using 45Ca2+. Radioactive calcium was applied to one side of the elongation zone about 4 mm back from the root tip and the distribution of radioactivity across the root in the region of application was determined using scintillation spectrometry. The movement of 45Ca2+ across the elongation zone was non-polar in vertically oriented roots. In gravistimulated roots the movement of label was polarized with about twice as much label moving from top to bottom as from bottom to top. A variety of treatments which interfere with gravitropism was found to eliminate the polar movement of 45Ca2+ across the elongation zone. In maize cultivars which require light for gravitropic competency, dark grown roots exhibited neither gravitropism nor polar movement of 45Ca2+ across the elongation zone. Upon illumination the roots developed but gravitropic competency and gravity-induced polar movement of 45Ca2+ across the elongation zone. Similarly, roots of light-grown seedlings lost both gravitropic competency and 45Ca2+ transport polarity upon transfer to the dark. The results indicate a close correlation between calcium movement and gravitropism in primary roots in maize.

  13. Polar transport of 45Ca2+ across the elongation zone of gravistimulated roots

    NASA Technical Reports Server (NTRS)

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

    1985-01-01

    The movement of calcium across the elongation zone of gravistimulated primary roots of maize (Zea mays L.) was measured using 45Ca2+. Radioactive calcium was applied to one side of the elongation zone about 4 mm back from the root tip and the distribution of radioactivity across the root in the region of application was determined using scintillation spectrometry. The movement of 45Ca2+ across the elongation zone was non-polar in vertically oriented roots. In gravistimulated roots the movement of label was polarized with about twice as much label moving from top to bottom as from bottom to top. A variety of treatments which interfere with gravitropism was found to eliminate the polar movement of 45Ca2+ across the elongation zone. In maize cultivars which require light for gravitropic competency, dark grown roots exhibited neither gravitropism nor polar movement of 45Ca2+ across the elongation zone. Upon illumination the roots developed but gravitropic competency and gravity-induced polar movement of 45Ca2+ across the elongation zone. Similarly, roots of light-grown seedlings lost both gravitropic competency and 45Ca2+ transport polarity upon transfer to the dark. The results indicate a close correlation between calcium movement and gravitropism in primary roots in maize.

  14. Tubulin cytoskeleton in elongation zone of Arabidopsis root is affected by clinorotation

    NASA Astrophysics Data System (ADS)

    Shevchenko, G.; Kalinina, Ya.; Kordyum, E.

    Our aim is to find out how clinorotation influences root growth For this purpose we followed the dynamics of tubulin cytoskeleton cortical and endoplasmic microtubules in cells from elongation zone of Arabidopsis roots transfected with GFP-MAP4 3 day old seedlings In distal part of elongation zone in epidermal cells mainly distinct endoplasmic microtubules were observed Prominent cortical microtubules start to be evident in cells in central elongation zone Under clinorotation clusters formed by MAP4 appear in all parts of elongation zone evidencing that microtubule arrangement is somehow distorted there Application of cytochalasin D which disrupts proper functioning of actin cytoskeleton in controls affected mainly the endoplasmic microtubules in cells with isotropic growth where MAP4 was clustered Under clinorotation disruption of actin cytoskeleton by cytochalasin D caused appearance of MAP4 clusters in cells growing anisotropically In those cells cortical microtubules are affected as well as endoplasmic Due to the fact that cortical microtubules are responsible for ordered growth of plant cell and are arranged into a robust structure change of their organization under clinorotation could impact cell growth This proves that cells in elongation zone switching their growth mode from isotropic to anisotropic are rather sensitive to altered gravity The fact that more severe distortion of cortical microtubules was noted in cells with damaged actin microfilaments proves mutually related functioning of actin and tubulin cytoskeletons under clinorotation

  15. The role of the distal elongation zone in the response of maize roots to auxin and gravity

    NASA Technical Reports Server (NTRS)

    Ishikawa, H.; Evans, M. L.

    1993-01-01

    We used a video digitizer system to (a) measure changes in the pattern of longitudinal surface extension in primary roots of maize (Zea mays L.) upon application and withdrawal of auxin and (b) compare these patterns during gravitropism in control roots and roots pretreated with auxin. Special attention was paid to the distal elongation zone (DEZ), arbitrarily defined as the region between the meristem and the point within the elongation zone at which the rate of elongation reaches 0.3 of the peak rate. For roots in aqueous solution, the basal limit of the DEZ is about 2.5 mm behind the tip of the root cap. Auxin suppressed elongation throughout the elongation zone, but, after 1 to 3 h, elongation resumed, primarily as a result of induction of rapid elongation in the DEZ. Withdrawal of auxin during the period of strong inhibition resulted in exceptionally rapid elongation attributable to the initiation of rapid elongation in the DEZ plus recovery in the main elongation zone. Gravistimulation of auxin-inhibited roots induced rapid elongation in the DEZ along the top of the root. This resulted in rapid gravitropism even though the elongation rate of the root was zero before gravistimulation. The results indicate that cells of the DEZ differ from cells in the bulk of the elongation zone with respect to auxin sensitivity and that DEZ cells play an important role in gravitropism.

  16. The role of the distal elongation zone in the response of maize roots to auxin and gravity

    NASA Technical Reports Server (NTRS)

    Ishikawa, H.; Evans, M. L.

    1993-01-01

    We used a video digitizer system to (a) measure changes in the pattern of longitudinal surface extension in primary roots of maize (Zea mays L.) upon application and withdrawal of auxin and (b) compare these patterns during gravitropism in control roots and roots pretreated with auxin. Special attention was paid to the distal elongation zone (DEZ), arbitrarily defined as the region between the meristem and the point within the elongation zone at which the rate of elongation reaches 0.3 of the peak rate. For roots in aqueous solution, the basal limit of the DEZ is about 2.5 mm behind the tip of the root cap. Auxin suppressed elongation throughout the elongation zone, but, after 1 to 3 h, elongation resumed, primarily as a result of induction of rapid elongation in the DEZ. Withdrawal of auxin during the period of strong inhibition resulted in exceptionally rapid elongation attributable to the initiation of rapid elongation in the DEZ plus recovery in the main elongation zone. Gravistimulation of auxin-inhibited roots induced rapid elongation in the DEZ along the top of the root. This resulted in rapid gravitropism even though the elongation rate of the root was zero before gravistimulation. The results indicate that cells of the DEZ differ from cells in the bulk of the elongation zone with respect to auxin sensitivity and that DEZ cells play an important role in gravitropism.

  17. The boundary of the meristematic and elongation zones in roots: endoreduplication precedes rapid cell expansion

    PubMed Central

    Hayashi, Kohma; Hasegawa, Junko; Matsunaga, Sachihiro

    2013-01-01

    Plant roots consist of a meristematic zone of mitotic cells and an elongation zone of rapidly expanding cells, in which DNA replication often occurs without cell division, a process known as endoreduplication. The duration of the cell cycle and DNA replication, as measured by 5-ethynyl-2′-deoxy-uridine (EdU) incorporation, differed between the two regions (17 h in the meristematic zone, 30 h in the elongation zone). Two distinct subnuclear patterns of EdU signals, whole and speckled, marked nuclei undergoing DNA replication at early and late S phase, respectively. The boundary region between the meristematic and elongation zones was analysed by a combination of DNA replication imaging and optical estimation of the amount of DNA in each nucleus (C-value). We found a boundary cell with 4C nuclei exhibiting the whole pattern of EdU signals. Analyses of cells in the boundary region revealed that endoreduplication precedes rapid cell elongation in roots. PMID:24121463

  18. The Interplay between Carbon Availability and Growth in Different Zones of the Growing Maize Leaf1[OPEN

    PubMed Central

    Arrivault, Stéphanie; Lohse, Marc A.; Feil, Regina; Krohn, Nicole; Encke, Beatrice; Nunes-Nesi, Adriano; Fernie, Alisdair R.; Stitt, Mark

    2016-01-01

    Plants assimilate carbon in their photosynthetic tissues in the light. However, carbon is required during the night and in nonphotosynthetic organs. It is therefore essential that plants manage their carbon resources spatially and temporally and coordinate growth with carbon availability. In growing maize (Zea mays) leaf blades, a defined developmental gradient facilitates analyses in the cell division, elongation, and mature zones. We investigated the responses of the metabolome and transcriptome and polysome loading, as a qualitative proxy for protein synthesis, at dusk, dawn, and 6, 14, and 24 h into an extended night, and tracked whole-leaf elongation over this time course. Starch and sugars are depleted by dawn in the mature zone, but only after an extension of the night in the elongation and division zones. Sucrose (Suc) recovers partially between 14 and 24 h into the extended night in the growth zones, but not the mature zone. The global metabolome and transcriptome track these zone-specific changes in Suc. Leaf elongation and polysome loading in the growth zones also remain high at dawn, decrease between 6 and 14 h into the extended night, and then partially recover, indicating that growth processes are determined by local carbon status. The level of Suc-signaling metabolite trehalose-6-phosphate, and the trehalose-6-phosphate:Suc ratio are much higher in growth than mature zones at dusk and dawn but fall in the extended night. Candidate genes were identified by searching for transcripts that show characteristic temporal response patterns or contrasting responses to carbon starvation in growth and mature zones. PMID:27582314

  19. Salinity-induced inhibition of leaf elongation in maize is not mediated by changes in cell wall acidification capacity.

    PubMed

    Neves-Piestun, B G; Bernstein, N

    2001-03-01

    The physiological mechanisms underlying leaf growth inhibition under salt stress are not fully understood. Apoplastic pH is considered to play an important role in cell wall loosening and tissue growth and was demonstrated to be altered by several growth-limiting environmental conditions. In this study we have evaluated the possibility that inhibition of maize (Zea mays) leaf elongation by salinity is mediated by changes in growing cell wall acidification capacity. The kinetics of extended apoplast pH changes by leaf tissue of known expansion rates and extent of growth reduction under stress was investigated (in vivo) and was found similar for non-stressed and salt-stressed tissues at all examined apoplast salinity levels (0.1, 5, 10, or 25 mM NaCl). A similar rate of spontaneous acidification for the salt and control treatments was demonstrated also in in situ experiments. Unlike growing cells that acidified the external medium, mature nongrowing cells caused medium alkalinization. The kinetics of pH changes by mature tissue was also unchanged by salt stress. Fusicoccin, an enhancer of plasmalemma H(+)-ATPase activity level, greatly stimulated elongation growth and acidification rate to a similar extent in the control and salt treatments. That the ability of the growing tissue to acidify the apoplast did not change under same salt stress conditions that induced inhibition of tissue elongation rate suggests that salinity does not inhibit cell growth by impairing the acidification process or reducing the inherent capacity for cell wall acidification.

  20. Salinity-Induced Inhibition of Leaf Elongation in Maize Is Not Mediated by Changes in Cell Wall Acidification Capacity1

    PubMed Central

    Neves-Piestun, Beatriz G.; Bernstein, Nirit

    2001-01-01

    The physiological mechanisms underlying leaf growth inhibition under salt stress are not fully understood. Apoplastic pH is considered to play an important role in cell wall loosening and tissue growth and was demonstrated to be altered by several growth-limiting environmental conditions. In this study we have evaluated the possibility that inhibition of maize (Zea mays) leaf elongation by salinity is mediated by changes in growing cell wall acidification capacity. The kinetics of extended apoplast pH changes by leaf tissue of known expansion rates and extent of growth reduction under stress was investigated (in vivo) and was found similar for non-stressed and salt-stressed tissues at all examined apoplast salinity levels (0.1, 5, 10, or 25 mm NaCl). A similar rate of spontaneous acidification for the salt and control treatments was demonstrated also in in situ experiments. Unlike growing cells that acidified the external medium, mature nongrowing cells caused medium alkalinization. The kinetics of pH changes by mature tissue was also unchanged by salt stress. Fusicoccin, an enhancer of plasmalemma H+-ATPase activity level, greatly stimulated elongation growth and acidification rate to a similar extent in the control and salt treatments. That the ability of the growing tissue to acidify the apoplast did not change under same salt stress conditions that induced inhibition of tissue elongation rate suggests that salinity does not inhibit cell growth by impairing the acidification process or reducing the inherent capacity for cell wall acidification. PMID:11244121

  1. Organelle sedimentation in gravitropic roots of Limnobium is restricted to the elongation zone

    NASA Technical Reports Server (NTRS)

    Sack, F. D.; Kim, D.; Stein, B.

    1994-01-01

    Roots of the aquatic angiosperm Limnobium spongia (Bosc) Steud. were evaluated by light and electron microscopy to determine the distribution of organelle sedimentation towards gravity. Roots of Limnobium are strongly gravitropic. The rootcap consists of only two layers of cells. Although small amyloplasts are present in the central cap cells, no sedimentation of any organelle, including amyloplasts, was found. In contrast, both amyloplasts and nuclei sediment consistently and completely in cells of the elongation zone. Sedimentation occurs in one cell layer of the cortex just outside the endodermis. Sedimentation of both amyloplasts and nuclei begins in cells that are in their initial stages of elongation and persists at least to the level of the root where root hairs emerge. This is the first modern report of the presence of sedimentation away from, but not in, the rootcap. It shows that sedimentation in the rootcap is not necessary for gravitropic sensing in at least one angiosperm. If amyloplast sedimentation is responsible for gravitropic sensing, then the site of sensing in Limnobium roots is the elongation zone and not the rootcap. These data do not necessarily conflict with the hypothesis that sensing occurs in the cap in other roots, since Limnobium roots are exceptional in rootcap origin and structure, as well as in the distribution of organelle sedimentation. Similarly, if nuclear sedimentation is involved in gravitropic sensing, then nuclear mass would function in addition to, not instead of, that of amyloplasts.

  2. Organelle sedimentation in gravitropic roots of Limnobium is restricted to the elongation zone

    NASA Technical Reports Server (NTRS)

    Sack, F. D.; Kim, D.; Stein, B.

    1994-01-01

    Roots of the aquatic angiosperm Limnobium spongia (Bosc) Steud. were evaluated by light and electron microscopy to determine the distribution of organelle sedimentation towards gravity. Roots of Limnobium are strongly gravitropic. The rootcap consists of only two layers of cells. Although small amyloplasts are present in the central cap cells, no sedimentation of any organelle, including amyloplasts, was found. In contrast, both amyloplasts and nuclei sediment consistently and completely in cells of the elongation zone. Sedimentation occurs in one cell layer of the cortex just outside the endodermis. Sedimentation of both amyloplasts and nuclei begins in cells that are in their initial stages of elongation and persists at least to the level of the root where root hairs emerge. This is the first modern report of the presence of sedimentation away from, but not in, the rootcap. It shows that sedimentation in the rootcap is not necessary for gravitropic sensing in at least one angiosperm. If amyloplast sedimentation is responsible for gravitropic sensing, then the site of sensing in Limnobium roots is the elongation zone and not the rootcap. These data do not necessarily conflict with the hypothesis that sensing occurs in the cap in other roots, since Limnobium roots are exceptional in rootcap origin and structure, as well as in the distribution of organelle sedimentation. Similarly, if nuclear sedimentation is involved in gravitropic sensing, then nuclear mass would function in addition to, not instead of, that of amyloplasts.

  3. The Regulation of Growth in the Distal Elongation Zone of Maize Roots

    NASA Technical Reports Server (NTRS)

    Evans, Michael L.

    1998-01-01

    The major goals of the proposed research were 1. To develop specialized software for automated whole surface root expansion analysis and to develop technology for controlled placement of surface electrodes for analysis of relationships between root growth and root pH and electrophysiological properties. 2. To measure surface pH patterns and determine the possible role of proton flux in gravitropic sensing or response, and 3. To determine the role of auxin transport in establishment of patterns of proton flux and electrical gradients during the gravitropic response of roots with special emphasis on the role of the distal elongation zone in the early phases of the gravitropic response.

  4. Analysis of changes in relative elemental growth rate patterns in the elongation zone of Arabidopsis roots upon gravistimulation

    NASA Technical Reports Server (NTRS)

    Mullen, J. L.; Ishikawa, H.; Evans, M. L.

    1998-01-01

    Although Arabidopsis is an important system for studying root physiology, the localized growth patterns of its roots have not been well defined, particularly during tropic responses. In order to characterize growth rate profiles along the apex of primary roots of Arabidopsis thaliana (L.) Heynh (ecotype Columbia) we applied small charcoal particles to the root surface and analyzed their displacement during growth using an automated video digitizer system with custom software for tracking the markers. When growing vertically, the maximum elongation rate occurred 481 +/- 50 microns back from the extreme tip of the root (tip of root cap), and the elongation zone extended back to 912 +/- 137 microns. The distal elongation zone (DEZ) has previously been described as the apical region of the elongation zone in which the relative elemental growth rate (REGR) is < or = 30% of the peak rate in the central elongation zone. By this definition, our data indicate that the basal limit of the DEZ was located 248 +/- 30 microns from the root tip. However, after gravistimulation, the growth patterns of the root changed. Within the first hour of graviresponse, the basal limit of the DEZ and the position of peak REGR shifted apically on the upper flank of the root. This was due to a combination of increased growth in the DEZ and growth inhibition in the central elongation zone. On the lower flank, the basal limit of the DEZ shifted basipetally as the REGR decreased. These factors set up the gradient of growth rate across the root, which drives curvature.

  5. Analysis of changes in relative elemental growth rate patterns in the elongation zone of Arabidopsis roots upon gravistimulation

    NASA Technical Reports Server (NTRS)

    Mullen, J. L.; Ishikawa, H.; Evans, M. L.

    1998-01-01

    Although Arabidopsis is an important system for studying root physiology, the localized growth patterns of its roots have not been well defined, particularly during tropic responses. In order to characterize growth rate profiles along the apex of primary roots of Arabidopsis thaliana (L.) Heynh (ecotype Columbia) we applied small charcoal particles to the root surface and analyzed their displacement during growth using an automated video digitizer system with custom software for tracking the markers. When growing vertically, the maximum elongation rate occurred 481 +/- 50 microns back from the extreme tip of the root (tip of root cap), and the elongation zone extended back to 912 +/- 137 microns. The distal elongation zone (DEZ) has previously been described as the apical region of the elongation zone in which the relative elemental growth rate (REGR) is < or = 30% of the peak rate in the central elongation zone. By this definition, our data indicate that the basal limit of the DEZ was located 248 +/- 30 microns from the root tip. However, after gravistimulation, the growth patterns of the root changed. Within the first hour of graviresponse, the basal limit of the DEZ and the position of peak REGR shifted apically on the upper flank of the root. This was due to a combination of increased growth in the DEZ and growth inhibition in the central elongation zone. On the lower flank, the basal limit of the DEZ shifted basipetally as the REGR decreased. These factors set up the gradient of growth rate across the root, which drives curvature.

  6. Cytoplasmic calcium levels in protoplasts from the cap and elongation zone of maize roots

    NASA Technical Reports Server (NTRS)

    Kiss, H. G.; Evans, M. L.; Johnson, J. D.

    1991-01-01

    Calcium has been implicated as a key component in the signal transduction process of root gravitropism. We measured cytoplasmic free calcium in protoplasts isolated from the elongation zone and cap of primary roots of light-grown, vertically oriented seedlings of Zea mays L. Protoplasts were loaded with the penta-potassium salts of fura-2 and indo-1 by incubation in acidic solutions of these calcium indicators. Loading increased with decreasing pH but the pH dependence was stronger for indo-1 than for fura-2. In the case of fura-2, loading was enhanced only at the lowest pH (4.5) tested. Dyes loaded in this manner were distributed predominantly in the cytoplasm as indicated by fluorescence patterns. As an alternative method of loading, protoplasts were incubated with the acetoxymethylesters of fura-2 and indo-1. Protoplasts loaded by this method exhibited fluorescence both in the cytoplasm and in association with various organelles. Cytoplasmic calcium levels measured using spectrofluorometry, were found to be 160 +/- 40 nM and 257 +/- 27 nM, respectively, in populations of protoplasts from the root cap and elongation zone. Cytoplasmic free calcium did not increase upon addition of calcium to the incubation medium, indicating that the passive permeability to calcium was low.

  7. Distribution of Calcium Ions in Cells of the Root Distal Elongation Zone Under Clinorotation

    NASA Astrophysics Data System (ADS)

    Sobol, Margarita; Kordyum, Elizabeth

    2009-01-01

    Currently, calcium ions are known to play a crucial role in the vital activity of plant cells and in stimulus-response coupling for many environmental signals, altered gravity included. The available data on changes in Ca2 + distribution and concentration in the cells of different organisms influenced by altered gravity allow to suggest that microgravity affects the calcium messenger system, and provide new insight for the understanding of calcium-and gravity-dependent cellular processes. We have studied with confocal microscopy the distribution and relative content of calcium ions in the Beta vulgaris root distal elongation zone cells grown under slow horizontal clinorotation, reproducing one of the microgravity particularities, namely the absence of an orienting action of the gravity vector, compared to control conditions. We demonstrate that Ca2 + relative content is 1.3 times higher in the roots of seedlings grown upwards and 1.2 times higher in the seedlings grown downwards compared to the control. Based on obtained data, taking into account the specific physiological properties of cells in the distal elongation zone, it is supposed that, under clinorotation, enhanced Ca2 + relative content affects Ca2 + -dependent cytoskeleton reorganization involved in cell gravisensing in altered gravity.

  8. Distinct bacterial communities dominate tropical and temperate zone leaf litter.

    PubMed

    Kim, Mincheol; Kim, Woo-Sung; Tripathi, Binu M; Adams, Jonathan

    2014-05-01

    Little is known of the bacterial community of tropical rainforest leaf litter and how it might differ from temperate forest leaf litter and from the soils underneath. We sampled leaf litter in a similarly advanced stage of decay, and for comparison, we also sampled the surface layer of soil, at three tropical forest sites in Malaysia and four temperate forest sites in South Korea. Illumina sequencing targeting partial bacterial 16S ribosomal ribonucleic acid (rRNA) gene revealed that the bacterial community composition of both temperate and tropical litter is quite distinct from the soils underneath. Litter in both temperate and tropical forest was dominated by Proteobacteria and Actinobacteria, while soil is dominated by Acidobacteria and, to a lesser extent, Proteobacteria. However, bacterial communities of temperate and tropical litter clustered separately from one another on an ordination. The soil bacterial community structures were also distinctive to each climatic zone, suggesting that there must be a climate-specific biogeographical pattern in bacterial community composition. The differences were also found in the level of diversity. The temperate litter has a higher operational taxonomic unit (OTU) diversity than the tropical litter, paralleling the trend in soil diversity. Overall, it is striking that the difference in community composition between the leaf litter and the soil a few centimeters underneath is about the same as that between leaf litter in tropical and temperate climates, thousands of kilometers apart. However, one substantial difference was that the leaf litter of two tropical forest sites, Meranti and Forest Research Institute Malaysia (FRIM), was overwhelmingly dominated by the single genus Burkholderia, at 37 and 23 % of reads, respectively. The 454 sequencing result showed that most Burkholderia species in tropical leaf litter belong to nonpathogenic "plant beneficial" lineages. The differences from the temperate zone in the bacterial

  9. Dissecting a new connection between cytokinin and jasmonic acid in control of leaf growth

    USDA-ARS?s Scientific Manuscript database

    Plant growth is mediated by two cellular processes: division and elongation. The maize leaf is an excellent model to study plant growth since these processes are spatially separated into discreet zones - a division zone (DZ), transition zone (TZ), and elongation zone (EZ) - at the base of the leaf. ...

  10. Gibberellin-Regulation and Genetic Variations in Leaf Elongation for Tall Fescue in Association with Differential Gene Expression Controlling Cell Expansion

    PubMed Central

    Xu, Qian; Krishnan, Sanalkumar; Merewitz, Emily; Xu, Jichen; Huang, Bingru

    2016-01-01

    Leaf elongation rate (LER) is an important factor controlling plant growth and productivity. The objective of this study was to determine whether genetic variation in LER for a fast-growing (‘K-31’), and a dwarf cultivar (‘Bonsai’) of tall fescue (Festuca arundinacea) and gibberellic acid (GA) regulation of LER were associated with differential expression of cell-expansion genes. Plants were treated with GA3, trinexapac-ethyl (TE) (GA inhibitor), or water (untreated control) in a hydroponic system. LER of ‘K-31’ was 63% greater than that of ‘Bonsai’, which corresponded with 32% higher endogenous GA4 content in leaf and greater cell elongation and production rates under the untreated control condition. Exogenous application of GA3 significantly enhanced LER while TE treatment inhibited leaf elongation due to GA3-stimulation or TE-inhibition of cell elongation and production rate in leaves for both cultivars. Real-time quantitative polymerase chain reaction analysis revealed that three α-expansins, one β-expansin, and three xyloglucan endotransglycosylase (XET) genes were associated with GA-stimulation of leaf elongation, of which, the differential expression of EXPA4 and EXPA7 was related to the genotypic variation in LER of two cultivars. Those differentially-expressed expansin and XET genes could play major roles in genetic variation and GA-regulated leaf elongation in tall fescue. PMID:27457585

  11. Strigolactones contribute to shoot elongation and to the formation of leaf margin serrations in Medicago truncatula R108.

    PubMed

    Lauressergues, Dominique; André, Olivier; Peng, Jianling; Wen, Jiangqi; Chen, Rujin; Ratet, Pascal; Tadege, Million; Mysore, Kirankumar S; Rochange, Soizic F

    2015-03-01

    Strigolactones were recently identified as a new class of plant hormones involved in the control of shoot branching. The characterization of strigolactone mutants in several species has progressively revealed their contribution to several other aspects of development in roots and shoots. In this article, we characterize strigolactone-deficient and strigolactone-insensitive mutants of the model legume Medicago truncatula for aerial developmental traits. The most striking mutant phenotype observed was compact shoot architecture. In contrast with what was reported in other species, this could not be attributed to enhanced shoot branching, but was instead due to reduced shoot elongation. Another notable feature was the modified leaf shape in strigolactone mutants: serrations at the leaf margin were smaller in the mutants than in wild-type plants. This phenotype could be rescued in a dose-dependent manner by exogenous strigolactone treatments of strigolactone-deficient mutants, but not of strigolactone-insensitive mutants. Treatment with the auxin transport inhibitor N-1-naphthylphtalamic acid resulted in smooth leaf margins, opposite to the effect of strigolactone treatment. The contribution of strigolactones to the formation of leaf serrations in M. truncatula R108 line represents a novel function of these hormones, which has not been revealed by the analysis of strigolactone mutants in other species.

  12. Distribution of electrolytes in cells of the tomato root elongation zone during a gravitropic response

    NASA Astrophysics Data System (ADS)

    Klymchuk, Dmytro

    It is known that gravitropic response of etiolated seedlings is accompanied with asymmetrical distribution of auxins. The higher amount of auxins in the tissues of the lower sides of gravistimulated organs induces cell elongation in shoots and inhibits cell elongation in roots. In spite on the progress in understanding of the auxin-mediated effects on plant growth and development, there is no a complete conception concerning of gravitropic response mechanism. This investigation aims to determine whether the growth response of tomato seedlings on reorientation to the horizontal induces alterations in distribution of electrolytes in cells of the main root elongation zone, the site where induction of the curvature takes place. Tomato (Lycopersicon esculentum, Rio Grande) seedlings were grown on agar surface in 10 cm Petri dishes. The gravitropic response of seedlings was evaluated by the angle of gravitropic curvature after the roots were reoriented 90° from the vertical. Root segments of several mm basipetal to the root tip were fixed in liquid nitrogen, freeze-substituted with Lowicril K11M at -35° C. Sections 100 and 1000 nm thick were cut using LKB Ultrotome V, collected by dry method and analyzed in the 6060 LA SEM at accelerating voltage 15 kV. Using different modes of X-ray microanalysis (X-ray map, - line and -point analysis), distribution of the physiologically relevant ions (Na, P, K, Ca) in cells of surface layers of the upper and lower root sides were investigated. The peculiarities in localization of the electrolytes in different subcellular compartments as well as distribution in the direction between upper and lower sides of the root curvature are discussed.

  13. Interrelation between microtubules and microfilaments in the elongation zone of Arabidopsis root under clinorotation

    NASA Astrophysics Data System (ADS)

    Shevchenko, G. V.; Kalinina, Ya. M.; Kordyum, E. L.

    Arabidopsis thaliana plants stably transformed with a MAP4-GFP construct were grown under slow clinorotation to characterize the role of tubulin microtubules in cell growth and gravisensing in the distal elongation zone (DEZ) of the root. Plants were treated with actin and tubulin disrupting drugs to investigate the changes in microtubule distribution and orientation between clinostat grown and control plants. It has been shown that organization of microtubules in the meristem and DEZ of Arabidopsis seedling root is interrelated with the organization of microfilaments. Cooperation between cytoskeleton elements is dependent upon the type of cell differential growth and aimed to provide the stabilization of cell growth on earth. In contrast, under clinorotation the cross-talk between microtubules and microfilaments was less pronounced. This phenomenon suggests the existence of complex mechanism for regulation of microtubules and microfilaments which is probably, unmasked in simulated microgravity.

  14. Elongation growth of the leaf sheath base of Avena sativa seedlings: regulation by hormones and sucrose

    NASA Technical Reports Server (NTRS)

    Brock, T. G.; Kaufman, P. B.

    1991-01-01

    The leaf sheath base of the seedling of Avena sativa was characterized for growth response to hormones and sucrose. Six day old plants, raised under a 10:14 hr light:dark cycle, were excised at the coleoptilar node and 1 cm above the node for treatment. The growth of the leaf sheath base was promoted by gibberellic acid (GA3) and this response was dose dependent. The lag to response initiation was approximately 4 hr. Growth with or without GA3 (10 micromoles) was transient, diminishing appreciably after 48 hr. The addition of 10 mM sucrose greatly prolonged growth; the effect of GA3 and sucrose was additive. Neither indole-3-acetic acid (IAA) nor the cytokinin N6-benzyladenine (BA), alone or in combination, promoted the growth of leaf sheath bases. However, both significantly inhibited the action of GA3. The inhibitory effect of IAA was dose dependent and was not affected by the addition of BA or sucrose. These results indicate that the growth of leaf sheath bases of Avena sativa is promoted specifically by gibberellin, that this action depends on the availability of carbohydrates from outside of the leaf sheath base, and that the promotional effect of GA3 can be modified by either auxins or cytokinins.

  15. Elongation growth of the leaf sheath base of Avena sativa seedlings: regulation by hormones and sucrose

    NASA Technical Reports Server (NTRS)

    Brock, T. G.; Kaufman, P. B.

    1991-01-01

    The leaf sheath base of the seedling of Avena sativa was characterized for growth response to hormones and sucrose. Six day old plants, raised under a 10:14 hr light:dark cycle, were excised at the coleoptilar node and 1 cm above the node for treatment. The growth of the leaf sheath base was promoted by gibberellic acid (GA3) and this response was dose dependent. The lag to response initiation was approximately 4 hr. Growth with or without GA3 (10 micromoles) was transient, diminishing appreciably after 48 hr. The addition of 10 mM sucrose greatly prolonged growth; the effect of GA3 and sucrose was additive. Neither indole-3-acetic acid (IAA) nor the cytokinin N6-benzyladenine (BA), alone or in combination, promoted the growth of leaf sheath bases. However, both significantly inhibited the action of GA3. The inhibitory effect of IAA was dose dependent and was not affected by the addition of BA or sucrose. These results indicate that the growth of leaf sheath bases of Avena sativa is promoted specifically by gibberellin, that this action depends on the availability of carbohydrates from outside of the leaf sheath base, and that the promotional effect of GA3 can be modified by either auxins or cytokinins.

  16. Tomato SlDREB gene restricts leaf expansion and internode elongation by downregulating key genes for gibberellin biosynthesis

    PubMed Central

    Ye, Zhibiao

    2012-01-01

    Plants have evolved and adapted to different environments. Dwarfism is an adaptive trait of plants that helps them avoid high-energy costs under unfavourable conditions. The role of gibberellin (GA) in plant development has been well established. Several plant dehydration-responsive element-binding proteins (DREBs) have been identified and reported to be induced under abiotic and biotic stress conditions. A tomato DREB gene named SlDREB, which is a transcription factor and was cloned from cultivated tomato M82, was found to play a negative role in tomato plant architecture and enhances drought tolerance. Tissue expression profiles indicated that SlDREB was expressed mainly in the stem and leaf and could be induced by abscisic acid (ABA) but suppressed by GA and ethylene. SlDREB altered plant morphology by restricting leaf expansion and internode elongation when overexpressed, and the resulting dwarfism of tomato plants could be recovered by application of exogenous gibberellic acid (GA3). Transcriptional analysis of transgenic plants revealed that overexpression of SlDREB caused the dwarf phenotype by downregulating key genes involved in GA biosynthesis such as ent-copalyl diphosphate synthase (SlCPS) and GA 20-oxidases (SlGA20ox1, -2, and -4), thereby decreasing endogenous GA levels in transgenic plants. A yeast activity assay demonstrated that SlDREB specifically bound to dehydration-responsive element/C-repeat (DRE/CRT) elements of the SlCPS promoter region. Taken together, these data demonstrated that SlDREB can downregulate the expression of key genes required for GA biosynthesis and that it acts as a positive regulator in drought stress responses by restricting leaf expansion and internode elongation. PMID:23077200

  17. Tomato SlDREB gene restricts leaf expansion and internode elongation by downregulating key genes for gibberellin biosynthesis.

    PubMed

    Li, Jinhua; Sima, Wei; Ouyang, Bo; Wang, Taotao; Ziaf, Khurram; Luo, Zhidan; Liu, Lifeng; Li, Hanxia; Chen, Mingluan; Huang, Yunqing; Feng, Yuqi; Hao, Yanhong; Ye, Zhibiao

    2012-11-01

    Plants have evolved and adapted to different environments. Dwarfism is an adaptive trait of plants that helps them avoid high-energy costs under unfavourable conditions. The role of gibberellin (GA) in plant development has been well established. Several plant dehydration-responsive element-binding proteins (DREBs) have been identified and reported to be induced under abiotic and biotic stress conditions. A tomato DREB gene named SlDREB, which is a transcription factor and was cloned from cultivated tomato M82, was found to play a negative role in tomato plant architecture and enhances drought tolerance. Tissue expression profiles indicated that SlDREB was expressed mainly in the stem and leaf and could be induced by abscisic acid (ABA) but suppressed by GA and ethylene. SlDREB altered plant morphology by restricting leaf expansion and internode elongation when overexpressed, and the resulting dwarfism of tomato plants could be recovered by application of exogenous gibberellic acid (GA(3)). Transcriptional analysis of transgenic plants revealed that overexpression of SlDREB caused the dwarf phenotype by downregulating key genes involved in GA biosynthesis such as ent-copalyl diphosphate synthase (SlCPS) and GA 20-oxidases (SlGA20ox1, -2, and -4), thereby decreasing endogenous GA levels in transgenic plants. A yeast activity assay demonstrated that SlDREB specifically bound to dehydration-responsive element/C-repeat (DRE/CRT) elements of the SlCPS promoter region. Taken together, these data demonstrated that SlDREB can downregulate the expression of key genes required for GA biosynthesis and that it acts as a positive regulator in drought stress responses by restricting leaf expansion and internode elongation.

  18. Drought Induces Distinct Growth Response, Protection, and Recovery Mechanisms in the Maize Leaf Growth Zone1[OPEN

    PubMed Central

    Avramova, Viktoriya; AbdElgawad, Hamada; Zhang, Zhengfeng; Fotschki, Bartosz; Casadevall, Romina; Vergauwen, Lucia; Knapen, Dries; Taleisnik, Edith; Guisez, Yves; Asard, Han; Beemster, Gerrit T.S.

    2015-01-01

    Drought is the most important crop yield-limiting factor, and detailed knowledge of its impact on plant growth regulation is crucial. The maize (Zea mays) leaf growth zone offers unique possibilities for studying the spatiotemporal regulation of developmental processes by transcriptional analyses and methods that require more material, such as metabolite and enzyme activity measurements. By means of a kinematic analysis, we show that drought inhibits maize leaf growth by inhibiting cell division in the meristem and cell expansion in the elongation zone. Through a microarray study, we observed the down-regulation of 32 of the 54 cell cycle genes, providing a basis for the inhibited cell division. We also found evidence for an up-regulation of the photosynthetic machinery and the antioxidant and redox systems. This was confirmed by increased chlorophyll content in mature cells and increased activity of antioxidant enzymes and metabolite levels across the growth zone, respectively. We demonstrate the functional significance of the identified transcriptional reprogramming by showing that increasing the antioxidant capacity in the proliferation zone, by overexpression of the Arabidopsis (Arabidopsis thaliana) iron-superoxide dismutase gene, increases leaf growth rate by stimulating cell division. We also show that the increased photosynthetic capacity leads to enhanced photosynthesis upon rewatering, facilitating the often-observed growth compensation. PMID:26297138

  19. Influence of cluster zone leaf removal on Pinot noir grape chemical and volatile composition.

    PubMed

    Feng, Hui; Yuan, Fang; Skinkis, Patricia A; Qian, Michael C

    2015-04-15

    The influence of cluster-zone leaf removal on Pinot noir vine growth and fruit chemical and volatile composition was investigated in 3 years. Different severities of leaf removal (0%, 50%, 100%) were imposed during the pea-size stage of development from the cluster zone. Results show that cluster-zone leaf removal had little influence on vine growth, crop load, or grape maturity in terms of total soluble solids (TSS), pH or titratable acidity (TA) at harvest. However, 100% leaf removal resulted in higher concentrations of quercetin glycoside in grapes compared to 0% leaf removal. The 100% leaf removal also increased concentrations of petunidin- and malvidin-3-monoglucoside anthocyanins in two out of 3 years (2010 and 2012) by an average of 62% and 53%, respectively. In addition, 100% leaf removal resulted in higher concentrations of β-damascenone, and some bound-form terpenoids. The increases in β-damascenone were positively correlated to the increased sunlight exposure.

  20. Multiscale modelling of auxin transport in the plant-root elongation zone.

    PubMed

    Band, L R; King, J R

    2012-10-01

    In the root elongation zone of a plant, the hormone auxin moves in a polar manner due to active transport facilitated by spatially distributed influx and efflux carriers present on the cell membranes. To understand how the cell-scale active transport and passive diffusion combine to produce the effective tissue-scale flux, we apply asymptotic methods to a cell-based model of auxin transport to derive systematically a continuum description from the spatially discrete one. Using biologically relevant parameter values, we show how the carriers drive the dominant tissue-scale auxin flux and we predict how the overall auxin dynamics are affected by perturbations to these carriers, for example, in knockout mutants. The analysis shows how the dominant behaviour depends on the cells' lengths, and enables us to assess the relative importance of the diffusive auxin flux through the cell wall. Other distinguished limits are also identified and their potential roles discussed. As well as providing insight into auxin transport, the study illustrates the use of multiscale (cell to tissue) methods in deriving simplified models that retain the essential biology and provide understanding of the underlying dynamics.

  1. Lyme disease and relapsing fever Borrelia elongate through zones of peptidoglycan synthesis that mark division sites of daughter cells

    PubMed Central

    Jutras, Brandon Lyon; Scott, Molly; Parry, Bradley; Biboy, Jacob; Gray, Joe; Vollmer, Waldemar; Jacobs-Wagner, Christine

    2016-01-01

    Agents that cause Lyme disease, relapsing fever, leptospirosis, and syphilis belong to the phylum Spirochaetae—a unique lineage of bacteria most known for their long, spiral morphology. Despite the relevance to human health, little is known about the most fundamental aspects of spirochete growth. Here, using quantitative microscopy to track peptidoglycan cell-wall synthesis, we found that the Lyme disease spirochete Borrelia burgdorferi displays a complex pattern of growth. B. burgdorferi elongates from discrete zones that are both spatially and temporally regulated. In addition, some peptidoglycan incorporation occurs along the cell body, with the notable exception of a large region at the poles. Newborn cells inherit a highly active zone of peptidoglycan synthesis at midcell that contributes to elongation for most of the cell cycle. Concomitant with the initiation of nucleoid separation and cell constriction, second and third zones of elongation are established at the 1/4 and 3/4 cellular positions, marking future sites of division for the subsequent generation. Positioning of elongation zones along the cell is robust to cell length variations and is relatively precise over long distances (>30 µm), suggesting that cells ‟sense” relative, as opposed to absolute, cell length to establish zones of peptidoglycan synthesis. The transition from one to three zones of peptidoglycan growth during the cell cycle is also observed in relapsing fever Borrelia. However, this mode of growth does not extend to representative species from other spirochetal genera, suggesting that this distinctive growth mode represents an evolutionary divide in the spirochete phylum. PMID:27506799

  2. A hydraulic model is compatible with rapid changes in leaf elongation under fluctuating evaporative demand and soil water status.

    PubMed

    Caldeira, Cecilio F; Bosio, Mickael; Parent, Boris; Jeanguenin, Linda; Chaumont, François; Tardieu, François

    2014-04-01

    Plants are constantly facing rapid changes in evaporative demand and soil water content, which affect their water status and growth. In apparent contradiction to a hydraulic hypothesis, leaf elongation rate (LER) declined in the morning and recovered upon soil rehydration considerably quicker than transpiration rate and leaf water potential (typical half-times of 30 min versus 1-2 h). The morning decline of LER began at very low light and transpiration and closely followed the stomatal opening of leaves receiving direct light, which represent a small fraction of leaf area. A simulation model in maize (Zea mays) suggests that these findings are still compatible with a hydraulic hypothesis. The small water flux linked to stomatal aperture would be sufficient to decrease water potentials of the xylem and growing tissues, thereby causing a rapid decline of simulated LER, while the simulated water potential of mature tissues declines more slowly due to a high hydraulic capacitance. The model also captured growth patterns in the evening or upon soil rehydration. Changes in plant hydraulic conductance partly counteracted those of transpiration. Root hydraulic conductivity increased continuously in the morning, consistent with the transcript abundance of Zea maize Plasma Membrane Intrinsic Protein aquaporins. Transgenic lines underproducing abscisic acid, with lower hydraulic conductivity and higher stomatal conductance, had a LER declining more rapidly than wild-type plants. Whole-genome transcriptome and phosphoproteome analyses suggested that the hydraulic processes proposed here might be associated with other rapidly occurring mechanisms. Overall, the mechanisms and model presented here may be an essential component of drought tolerance in naturally fluctuating evaporative demand and soil moisture.

  3. Characterization of a Maize Tonoplast Aquaporin Expressed in Zones of Cell Division and Elongation1

    PubMed Central

    Chaumont, François; Barrieu, François; Herman, Eliot M.; Chrispeels, Maarten J.

    1998-01-01

    We studied aquaporins in maize (Zea mays), an important crop in which numerous studies on plant water relations have been carried out. A maize cDNA, ZmTIP1, was isolated by reverse transcription-coupled PCR using conserved motifs from plant aquaporins. The derived amino acid sequence of ZmTIP1 shows 76% sequence identity with the tonoplast aquaporin γ-TIP (tonoplast intrinsic protein) from Arabidopsis. Expression of ZmTIP1 in Xenopus laevis oocytes showed that it increased the osmotic water permeability of oocytes 5-fold; this water transport was inhibited by mercuric chloride. A cross-reacting antiserum made against bean α-TIP was used for immunocytochemical localization of ZmTIP1. These results indicate that this and/or other aquaporins is abundantly present in the small vacuoles of meristematic cells. Northern analysis demonstrated that ZmTIP1 is expressed in all plant organs. In situ hybridization showed a high ZmTIP1 expression in meristems and zones of cell enlargement: tips of primary and lateral roots, leaf primordia, and male and female inflorescence meristems. The high ZmTIP1 expression in meristems and expanding cells suggests that ZmTIP1 is needed (a) for vacuole biogenesis and (b) to support the rapid influx of water into vacuoles during cell expansion. PMID:9701570

  4. Comparison of chromatin epigenetic modification patterns among root meristem, elongation and maturation zones in maize (Zea mays L.).

    PubMed

    Yan, Shihan; Zhang, Qi; Li, Yingnan; Huang, Yan; Zhao, Lin; Tan, Junjun; He, Shibin; Li, Lijia

    2014-01-01

    Plant roots mainly consist of division, elongation and maturation regions. Histone modifications of chromatin play a vital role in plant cell growth and differentiation. However, there has been no systematic attempt to investigate the distribution patterns of histone modifications in the different plant root zones. In this study, histone H3 acetylation (H3K9ac), histone H4 acetylation (H4K5ac), and histone H3 methylation (H3K4me2, H3K4me3, H3K9me1, H3K9me2, and H3K27me2) levels and distribution patterns were examined in the root meristem, elongation and maturation zones of maize primary roots. Overall, the cells of the maturation zone displayed the highest level of multiple histone modifications. The lowest level of histone modification was detected in the root meristem. H3K9ac was enriched in the euchromatin and nucleoli of most nuclei from the elongation and maturation zones. The nucleoli of more than 60% of cells from all root regions were labeled by H4K5ac. In only a small proportion of cells (less than 7%), knobs showed H4K5ac signals. H3K4me2 and H3K4me3 were specifically detected in euchromatin. H3K9me1, H3K9me2 and H3K27me2 labeled heterochromatin and euchromatin in all the root tissues analyzed. Over 30% of elongation and maturation cells exhibited H3K9me1 signals around knobs, approximately 5% of maturation cells showed signals of H3K9me2 around knobs, and H3K27me2 was stained weakly in approximately 95% of maturation cells in knobs. Analysis of the genomic patterns of histone modifications across functionally distinct regions of maize roots reveals a root zone-specific chromatin distribution. © 2014 S. Karger AG, Basel.

  5. Leaf protein concentrate as food supplement from arid zone plants.

    PubMed

    Rathore, Mala

    2010-06-01

    In arid and semi-arid areas where prevalence of droughts and famines is a recurring feature, forest cover can in general make valuable contributions to food security and provide income to the rural poor. Protein and calorie malnutrition is widespread in these areas leading to high child mortality rate. Plant species can play an important role in overcoming this by being used as a source of leaf protein concentrate (LPC), a highly nutritious food. LPC should be considered seriously as it can serve as an additional protein source in the case of non-ruminants and man, especially in drought prone areas. The use of LPC in developing countries as an alternative protein source to fishmeal in broiler diet holds tremendous promise as it can substantially lower high cost of fishmeal and eventually the acute shortage of animal protein supply. Potential tropical plants for LPC production have been evaluated and selected for further research by United States Department of Agriculture. The present study was aimed to determine the potential of arid zone plants for preparation of LPC. Extraction characteristics of the several plant species have been studied and the quality of LPC prepared from them was investigated. Different fractions, chloroplastic and cytoplasmic proteins, were analyzed for their crude protein contents. Analysis of LPC shows considerable differences in their protein contents, which was found to range from 13.7 to 88.9%. Based on this, Achyranthes aspera and Tephrosia purpurea were found to be the best suited plants for LPC preparation.

  6. Homology of the internal sac components in the leaf beetle subfamily Criocerinae and evolutionary novelties related to the extremely elongated flagellum.

    PubMed

    Matsumura, Yoko; Yoshizawa, Kazunori

    2012-05-01

    Extremely elongated intromittent organs are found in a wide range of taxa, especially among insects. This phenomenon is generally thought to result from sexual selection, but it is predicted that limited storage space in the body cavity and the difficulty of using the elongated organs should have constrained the evolution of extreme elongation, neutralizing any selective advantage. Therefore, in groups with long intromittent organs, features that overcome these constraints may have evolved or coevolved together with intromittent organ elongation. Using a comparative morphological approach and outgroup comparisons, we identified potential constraints and key novelties that may neutralize such constraints in the leaf beetle subfamily Criocerinae. Observations of the internal sac structure throughout Criocerinae were performed. Comparing the results with preceding studies from outgroups, a ground plan of the criocerine internal sac was constructed. Our analysis also identified specific features that are always correlated with extreme elongation: the rotation of whole internal-sac sclerites and the possession of a pocket in which to store the elongated flagellum. The pocket is thought to be formed by the rotation of the sclerites, markedly altering internal sac shape from the criocerine ground plan. Onlythe clades that have acquired this derived state contain species with an elongated flagellum that distinctly exceeds the median lobe length. It is presumed that these character correlations evolved independently three times. The detected character correlations corroborate the hypothesis that there are latent adaptive constraints for the evolution of extremely elongated intromittent organs. The constraints may have been neutralized by the alteration from the criocerine ground plan resulting in the formation of a storage pocket. In conclusion, deviation from the criocerine ground plan is considered to be the evolutionary innovation that neutralized the latent adaptive

  7. Pinot noir wine volatile and anthocyanin composition under different levels of vine fruit zone leaf removal.

    PubMed

    Feng, Hui; Skinkis, Patricia A; Qian, Michael C

    2017-01-01

    The impacts of fruit zone leaf removal on volatile and anthocyanin compositions of Pinot noir wine were investigated over two growing seasons. Wine volatiles were analyzed by multiple techniques, including headspace solid phase microextraction-GC-MS (HS-SPME-GC-MS), headspace-GC-FID (HS-GC-FID) and stir bar sorptive extraction-GC-MS (SBSE-GC-MS). Fruit zone leaf removal affected the concentration of many grape-derived volatile compounds such as terpene alcohols and C13-norisoprenoids in wine, although the degree of impact depended on the vintage year and severity of leaf removal. Fruit zone leaf removal resulted in greater concentrations of linalool, α-terpineol and β-damascenone but had no impact on other terpene alcohols or β-ionone. Fruit zone leaf removal had no consistent impact on C6 alcohols, volatile phenols, lactones, fermentation-derived alcohols, acids, or most esters. Fruit zone leaf removal increased anthocyanins in final wine. Copyright © 2016 Elsevier Ltd. All rights reserved.

  8. Multi-omics analysis identifies genes mediating the extension of cell walls in the Arabidopsis thaliana root elongation zone

    PubMed Central

    Wilson, Michael H.; Holman, Tara J.; Sørensen, Iben; Cancho-Sanchez, Ester; Wells, Darren M.; Swarup, Ranjan; Knox, J. Paul; Willats, William G. T.; Ubeda-Tomás, Susana; Holdsworth, Michael; Bennett, Malcolm J.; Vissenberg, Kris; Hodgman, T. Charlie

    2015-01-01

    Plant cell wall composition is important for regulating growth rates, especially in roots. However, neither analyses of cell wall composition nor transcriptomes on their own can comprehensively reveal which genes and processes are mediating growth and cell elongation rates. This study reveals the benefits of carrying out multiple analyses in combination. Sections of roots from five anatomically and functionally defined zones in Arabidopsis thaliana were prepared and divided into three biological replicates. We used glycan microarrays and antibodies to identify the major classes of glycans and glycoproteins present in the cell walls of these sections, and identified the expected decrease in pectin and increase in xylan from the meristematic zone (MS), through the rapid and late elongation zones (REZ, LEZ) to the maturation zone and the rest of the root, including the emerging lateral roots. Other compositional changes included extensin and xyloglucan levels peaking in the REZ and increasing levels of arabinogalactan-proteins (AGP) epitopes from the MS to the LEZ, which remained high through the subsequent mature zones. Immuno-staining using the same antibodies identified the tissue and (sub)cellular localization of many epitopes. Extensins were localized in epidermal and cortex cell walls, while AGP glycans were specific to different tissues from root-hair cells to the stele. The transcriptome analysis found several gene families peaking in the REZ. These included a large family of peroxidases (which produce the reactive oxygen species (ROS) needed for cell expansion), and three xyloglucan endo-transglycosylase/hydrolase genes (XTH17, XTH18, and XTH19). The significance of the latter may be related to a role in breaking and re-joining xyloglucan cross-bridges between cellulose microfibrils, a process which is required for wall expansion. Knockdowns of these XTHs resulted in shorter root lengths, confirming a role of the corresponding proteins in root extension

  9. Investigating the roles of jasmonic acid and cytokinin in maize leaf growth control

    USDA-ARS?s Scientific Manuscript database

    Plant growth is the accumulation of biomass attributed to cell division and cell expansion. In the maize leaf, growth is spatially separated into three distinct growth zones: the division zone, elongation zone, and the maturation zone. This spatial separation makes the maize leaf a useful model for ...

  10. The effect of lunisolar tidal acceleration on stem elongation growth, nutations and leaf movements in peppermint (Mentha × piperita L.).

    PubMed

    Zajączkowska, U; Barlow, P W

    2017-03-03

    Orbital movement of the Moon generates a system of gravitational fields that periodically alter the gravitational force on Earth. This lunar tidal acceleration (Etide) is known to act as an external environmental factor affecting many growth and developmental phenomena in plants. Our study focused on the lunar tidal influence on stem elongation growth, nutations and leaf movements of peppermint. Plants were continuously recorded with time-lapse photography under constant illumination as well in constant illumination following 5 days of alternating dark-light cycles. Time courses of shoot movements were correlated with contemporaneous time courses of the Etide estimates. Optical microscopy and SEM were used in anatomical studies. All plant shoot movements were synchronised with changes in the lunisolar acceleration. Using a periodogram, wavelet analysis and local correlation index, a convergence was found between the rhythms of lunisolar acceleration and the rhythms of shoot growth. Also observed were cyclical changes in the direction of rotation of stem apices when gravitational dynamics were at their greatest. After contrasting dark-light cycle experiments, nutational rhythms converged to an identical phase relationship with the Etide and almost immediately their renewed movements commenced. Amplitudes of leaf movements decreased during leaf growth up to the stage when the leaf was fully developed; the periodicity of leaf movements correlated with the Etide rhythms. For the fist time, it was documented that lunisolar acceleration is an independent rhythmic environmental signal capable of influencing the dynamics of plant stem elongation. This phenomenon is synchronised with the known effects of Etide on nutations and leaf movements.

  11. Plasticity as a plastic response: how submergence-induced leaf elongation in Rumex palustris depends on light and nutrient availability in its early life stage.

    PubMed

    Huber, Heidrun; Chen, Xin; Hendriks, Marloes; Keijsers, Danny; Voesenek, Laurentius A C J; Pierik, Ronald; Poorter, Hendrik; de Kroon, Hans; Visser, Eric J W

    2012-04-01

    Plants may experience different environmental cues throughout their development which interact in determining their phenotype. This paper tests the hypothesis that environmental conditions experienced early during ontogeny affect the phenotypic response to subsequent environmental cues. This hypothesis was tested by exposing different accessions of Rumex palustris to different light and nutrient conditions, followed by subsequent complete submergence. Final leaf length and submergence-induced plasticity were affected by the environmental conditions experienced at early developmental stages. In developmentally older leaves, submergence-induced elongation was lower in plants previously subjected to high-light conditions. Submergence-induced elongation of developmentally younger leaves, however, was larger when pregrown in high light. High-light and low-nutrient conditions led to an increase of nonstructural carbohydrates in the plants. There was a positive correlation between submergence-induced leaf elongation and carbohydrate concentration and content in roots and shoots, but not with root and shoot biomass before submergence. These results show that conditions experienced by young plants modulate the responses to subsequent environmental conditions, in both magnitude and direction. Internal resource status interacts with cues perceived at different developmental stages in determining plastic responses to the environment.

  12. Electron probe X-ray microanalysis studies on the distribution change of intra- and extracellular calcium in the elongation zone of horizontally reoriented soybean roots.

    PubMed

    Hayatsu, Manabu; Suzuki, Suechika

    2015-10-01

    To clarify the contribution of Ca to the gravitropic response, quantitative X-ray microanalyses were performed on cryosections of roots of soybean seedlings reoriented horizontally from their original vertical orientation. After reorientation, the roots bent gradually toward the ground at the elongation zone. The concentrations of Ca in the cell walls, cytoplasmic matrices and central vacuoles of cortical cells were measured in the upper and lower halves of the elongation zone at 0, 30, 60 and 120 min after reorientation. The Ca concentration did not significantly change in the cytoplasmic matrices or vacuoles. Additionally, the Ca concentration did not change significantly in cell walls at 30 min after reorientation; however, beyond 30 min, this concentration significantly increased gradually in the lower half of the elongation zone and decreased in the upper half of the elongation zone, indicating a typical asymmetrical distribution of Ca. These results suggest that Ca moves apoplastically in soybean roots to produce an asymmetrical Ca distribution in the elongation zone, which contributes to root curvature. The possible role of Ca in accelerating or repressing the effect of auxin is also discussed in this study.

  13. Superposition of tectonic structures leading elongated intramontane basin: the Alhabia basin (Internal Zones, Betic Cordillera)

    NASA Astrophysics Data System (ADS)

    Martínez-Martos, Manuel; Galindo-Zaldivar, Jesús; Martínez-Moreno, Francisco José; Calvo-Rayo, Raquel; Sanz de Galdeano, Carlos

    2017-01-01

    The relief of the Betic Cordillera was formed since the late Serravallian inducing the development of intramontane basins. The Alhabia basin, situated in the central part of the Internal Zones, is located at the intersection of the Alpujarran Corridor, the Tabernas basin, both trending E-W, and the NW-SE oriented Gádor-Almería basin. The geometry of the basin has been constrained by new gravity data. The basin is limited to the North by the Sierra de Filabres and Sierra Nevada antiforms that started to develop in Serravallian times under N-S shortening and to the south by Sierra Alhamilla and Sierra de Gádor antiforms. Plate convergence in the region rotated counter-clockwise in Tortonian times favouring the formation of E-W dextral faults. In this setting, NE-SW extension, orthogonal to the shortening direction, was accommodated by normal faults on the SW edge of Sierra Alhamilla. The Alhabia basin shows a cross-shaped depocentre in the zone of synform and fault intersection. This field example serves to constrain recent counter-clockwise stress rotation during the latest stages of Neogene-Quaternary basin evolution in the Betic Cordillera Internal Zones and underlines the importance of studying the basins' deep structure and its relation with the tectonic structures interactions.

  14. Differential proton secretion in the apical elongation zone caused by gravistimulation is induced by a signal from the root cap.

    PubMed

    Monshausen, G B; Zieschang, H E; Sievers, A

    1996-12-01

    The extracellular proton activity along primary roots of Phleum pratense L. was measured using proton-selective microelectrodes. Removal of the root cap caused a reduction of the proton influx in the transitional region between the meristem and the apical elongation zone of the vertical root and inhibited the development of pH differences between the physically upper and lower flanks of the gravistimulated root. Disruption of the actin filament system of the root with 5 mmol m-3 cytochalasin D did not result in an altered proton flux and pH pattern compared with untreated vertical control roots, but inhibited the gravity-induced development of pH differences between the physically upper and lower root flanks as well as gravitropic curvature. These results provide evidence that pH changes following gravistimulation are induced by a signal transmitted from the root cap and that the actin filament system is involved in the gravity perception/transduction mechanism.

  15. Elongation Of The North Anatolian Fault Zone in the Sea of Marmara

    NASA Astrophysics Data System (ADS)

    Kurtulus, C.; Canbay, M. M.

    2003-04-01

    The North Anatolian Fault Zone (NAFZ) is a 1500 km long, seismically active, right lateral strike sleep fault that accommodates the relative motion between the Anatolian and Pontide blocks. The Sea of Marmara is an intra-continental sea lying along the western part of the NAFZ. There are two major fault systems in the Sea of Marmara one of which consists of the east-west striking faults and the other one is made up of NE-SW-trending faults that dissect the first group. The east, middle and the south parts of the Sea of Marmara are interpreted as pull-apart basins characterized by shear stresses. The interpretation of the structural framework indicates that the northern strand of the NAFZ traverses the Gulf of Izmit and deep Marmara to bind the Gulf of Saros and the middle strand of it traverses the Gulf of Gemlik, Bandirma and the Gulf of Erdek.

  16. Xyloglucan endotransglucosylase action is high in the root elongation zone and in the trichoblasts of all vascular plants from Selaginella to Zea mays.

    PubMed

    Vissenberg, K; Van Sandt, V; Fry, S C; Verbelen, J-P

    2003-01-01

    The endotransglucosylase action of the enzyme xyloglucan endotransglucosylase/hydrolase (XTH) was localized in the roots of diverse vascular plants: club-mosses (lycopodiophytes), ferns, gymnosperms, monocots, and dicots. High action was always found in the epidermis cell wall of the elongation zone and in trichoblasts in the differentiation zone. Clearly XTH and its action in root development evolved before the evolutionary divergence of ferns and seed plants and also of the lycopodiophytes and euphyllophytes.

  17. Functional morphology and evolution of the hyper-elongated intromittent organ in Cassida leaf beetles (Coleoptera: Chrysomelidae: Cassidinae).

    PubMed

    Matsumura, Yoko; Michels, Jan; Appel, Esther; Gorb, Stanislav N

    2017-02-01

    The peculiar phenomenon of hyper-elongation of intromittent organs is well known in a number of insect groups. However, the unresolved questions of how and why such a phenomenon originated independently many times continue to attract biologists' attention. To be able to detect the evolutionary driving mechanisms that enabled insects to repeatedly acquire such a peculiarity, first of all the structural key features and the mechanics of these organs have to be determined. In the present study, the morphology of the reproductive organs of two species of the beetle genus Cassida, with a special focus on the male structures, was scrutinised in detail during copulation and at rest using different microscopy techniques. We found that the hyper-elongated structure of the intromittent organ, called flagellum, is part of the male ejaculatory duct. When the flagellum is inserted into the female spermathecal duct, longitudinal muscles of the ejaculatory duct, but not the flagellum, are shortened. These results strongly suggest that the contraction of the longitudinal muscles of the ejaculatory duct causes propulsion of the flagellum into the highly spiralled spermathecal duct of the female. The tip of the cuticular flagellum is curled up, which can suggest that its physical properties differ from those of the rest of the flagellum. Considering the preceding modelling studies, this property aids the flagellum in penetrating within the highly spiralled and very variable female duct. Based on our morphological results and in comparison with the morphology of intromittent organs of other beetles, we discuss the evolutionary origin of the hyper-elongation in the Cassida species and propose a hypothesis that explains the independent origin of the hyper-elongation of intromittent organs.

  18. Geomorphological characteristics of elongate subglacial bedforms in the terminal zone of a palaeo-ice stream, NW Poland

    NASA Astrophysics Data System (ADS)

    Hermanowski, Piotr; Piotrowski, Jan A.

    2017-04-01

    A large body of literature concerns the morphology and spatial patterns of drumlins, mega-scale glacial lineations and other related subglacial bedforms. Geomorphological analyses of these streamlined bedforms facilitate identification of palaeo-ice streams and yield data to constrain their dynamics in time and space. In this study we investigated the morphometric characteristics and spatial patterns of over 1300 streamlined bedforms in the Stargard drumlin field (NW Poland) marking a terminal area of a major last-glacial palaeo-ice stream based on a high-resolution digital terrain model (LiDAR). Most of the streamlined bedforms are 600 to 800 m long, while the modal class of their widths is from 200 to 250 m. Almost 50% of the bedforms are between 3-6 m high and only slightly below 4% are higher than 10 m. The elongation ratios of ca. 60% of the population ranges from 1.5 to 3.0 and the modal class is 2.00-2.25. The overall pattern of the field reveals a distinct curvature corresponding to a radial flow pattern in a big ice lobe, but local deviations grouped in several discrete zones occur. The variations in spatial characteristics of the streamlined bedforms reflect different subglacial conditions and the diversified topography of the pre-ice advance terrain, both resulting in a spatial and temporal mosaic of ice flow velocities and directions.

  19. Hyper, a hydrogen peroxide sensor, indicates the sensitivity of the Arabidopsis root elongation zone to aluminum treatment.

    PubMed

    Hernández-Barrera, Alejandra; Velarde-Buendía, Ana; Zepeda, Isaac; Sanchez, Federico; Quinto, Carmen; Sánchez-Lopez, Rosana; Cheung, Alice Y; Wu, Hen-Ming; Cardenas, Luis

    2015-01-06

    Emerging evidence indicates that some reactive oxygen species (ROS), such as the superoxide anion radical and hydrogen peroxide (H2O2), are central regulators of plant responses to biotic and abiotic stresses. Thus, the cellular levels of ROS are thought to be tightly regulated by an efficient and elaborate pro- and antioxidant system that modulates the production and scavenging of ROS. Until recently, studies of ROS in plant cells have been limited to biochemical assays and the use of fluorescent probes; however, the irreversible oxidation of these fluorescent probes makes it impossible to visualize dynamic changes in ROS levels. In this work, we describe the use of Hyper, a recently developed live cell probe for H2O2 measurements in living cells, to monitor oxidative stress in Arabidopsis roots subjected to aluminum treatment. Hyper consists of a circularly permuted YFP (cpYFP) inserted into the regulatory domain of the Escherichia coli hydrogen peroxide-binding protein (OxyR), and is a H2O2-specific ratiometric, and therefore quantitative, probe that can be expressed in plant and animal cells. Now we demonstrate that H2O2 levels drop sharply in the elongation zone of roots treated with aluminum. This response could contribute to root growth arrest and provides evidence that H2O2 is involved in early Al sensing.

  20. Hyper, a Hydrogen Peroxide Sensor, Indicates the Sensitivity of the Arabidopsis Root Elongation Zone to Aluminum Treatment

    PubMed Central

    Hernández-Barrera, Alejandra; Velarde-Buendía, Ana; Zepeda, Isaac; Sanchez, Federico; Quinto, Carmen; Sánchez-Lopez, Rosana; Cheung, Alice Y.; Wu, Hen-Ming; Cardenas, Luis

    2015-01-01

    Emerging evidence indicates that some reactive oxygen species (ROS), such as the superoxide anion radical and hydrogen peroxide (H2O2), are central regulators of plant responses to biotic and abiotic stresses. Thus, the cellular levels of ROS are thought to be tightly regulated by an efficient and elaborate pro- and antioxidant system that modulates the production and scavenging of ROS. Until recently, studies of ROS in plant cells have been limited to biochemical assays and the use of fluorescent probes; however, the irreversible oxidation of these fluorescent probes makes it impossible to visualize dynamic changes in ROS levels. In this work, we describe the use of Hyper, a recently developed live cell probe for H2O2 measurements in living cells, to monitor oxidative stress in Arabidopsis roots subjected to aluminum treatment. Hyper consists of a circularly permuted YFP (cpYFP) inserted into the regulatory domain of the Escherichia coli hydrogen peroxide-binding protein (OxyR), and is a H2O2-specific ratiometric, and therefore quantitative, probe that can be expressed in plant and animal cells. Now we demonstrate that H2O2 levels drop sharply in the elongation zone of roots treated with aluminum. This response could contribute to root growth arrest and provides evidence that H2O2 is involved in early Al sensing. PMID:25569758

  1. Endoreduplication preferentially occurs at the proximal side of the abscission zone during abscission of tomato leaf.

    PubMed

    Dermastia, Marina; Kladnik, Aleš; Bar-Dror, Tal; Lers, Amnon

    2012-09-01

    Endoreduplication is a cell cycle variant in which multiple rounds of DNA replication occur without subsequent mitosis, resulting in polyploid cells. Although cells with endoreduplicated nuclei were ubiquitously distributed throughout the abscission zone (AZ) of tomato leaf before abscission induction by ethylene, endoreduplication was detected mostly on the proximal side of the AZ after induction. The possible association between endoreduplication and intensive membrane trafficking in cells at the proximal side of the AZ is discussed.

  2. Endoreduplication preferentially occurs at the proximal side of the abscission zone during abscission of tomato leaf

    PubMed Central

    Dermastia, Marina; Kladnik, Aleš; Bar-Dror, Tal; Lers, Amnon

    2012-01-01

    Endoreduplication is a cell cycle variant in which multiple rounds of DNA replication occur without subsequent mitosis, resulting in polyploid cells. Although cells with endoreduplicated nuclei were ubiquitously distributed throughout the abscission zone (AZ) of tomato leaf before abscission induction by ethylene, endoreduplication was detected mostly on the proximal side of the AZ after induction. The possible association between endoreduplication and intensive membrane trafficking in cells at the proximal side of the AZ is discussed. PMID:22899068

  3. Control of climate and litter quality on leaf litter decomposition in different climatic zones.

    PubMed

    Zhang, Xinyue; Wang, Wei

    2015-09-01

    Climate and initial litter quality are the major factors influencing decomposition rates on large scales. We established a comprehensive database of terrestrial leaf litter decomposition, including 785 datasets, to examine the relationship between climate and litter quality and evaluate the factors controlling decomposition on a global scale, the arid and semi-arid (AS) zone, the humid middle and humid low (HL) latitude zones. Initial litter nitrogen (N) and phosphorus (P) concentration only increased with mean annual temperature (MAT) in the AS zone and decreased with mean annual precipitation (MAP) in the HL zone. Compared with nutrient content, MAT imposed less effect on initial litter lignin content than MAP. MAT were the most important decomposition driving factors on a global scale as well as in different climatic zones. MAP only significantly affected decomposition constants in AS zone. Although litter quality parameters also showed significant influence on decomposition, their importance was less than the climatic factors. Besides, different litter quality parameters exerted significant influence on decomposition in different climatic zones. Our results emphasized that climate consistently exerted important effects on decomposition constants across different climatic zones.

  4. A Hydraulic Model Is Compatible with Rapid Changes in Leaf Elongation under Fluctuating Evaporative Demand and Soil Water Status1[C][W][OPEN

    PubMed Central

    Caldeira, Cecilio F.; Bosio, Mickael; Parent, Boris; Jeanguenin, Linda; Chaumont, François; Tardieu, François

    2014-01-01

    Plants are constantly facing rapid changes in evaporative demand and soil water content, which affect their water status and growth. In apparent contradiction to a hydraulic hypothesis, leaf elongation rate (LER) declined in the morning and recovered upon soil rehydration considerably quicker than transpiration rate and leaf water potential (typical half-times of 30 min versus 1–2 h). The morning decline of LER began at very low light and transpiration and closely followed the stomatal opening of leaves receiving direct light, which represent a small fraction of leaf area. A simulation model in maize (Zea mays) suggests that these findings are still compatible with a hydraulic hypothesis. The small water flux linked to stomatal aperture would be sufficient to decrease water potentials of the xylem and growing tissues, thereby causing a rapid decline of simulated LER, while the simulated water potential of mature tissues declines more slowly due to a high hydraulic capacitance. The model also captured growth patterns in the evening or upon soil rehydration. Changes in plant hydraulic conductance partly counteracted those of transpiration. Root hydraulic conductivity increased continuously in the morning, consistent with the transcript abundance of Zea maize Plasma Membrane Intrinsic Protein aquaporins. Transgenic lines underproducing abscisic acid, with lower hydraulic conductivity and higher stomatal conductance, had a LER declining more rapidly than wild-type plants. Whole-genome transcriptome and phosphoproteome analyses suggested that the hydraulic processes proposed here might be associated with other rapidly occurring mechanisms. Overall, the mechanisms and model presented here may be an essential component of drought tolerance in naturally fluctuating evaporative demand and soil moisture. PMID:24420931

  5. Differential expression profiles and pathways of genes in sugarcane leaf at elongation stage in response to drought stress

    PubMed Central

    Li, Changning; Nong, Qian; Solanki, Manoj Kumar; Liang, Qiang; Xie, Jinlan; Liu, Xiaoyan; Li, Yijie; Wang, Weizan; Yang, Litao; Li, Yangrui

    2016-01-01

    Water stress causes considerable yield losses in sugarcane. To investigate differentially expressed genes under water stress, a pot experiment was performed with the sugarcane variety GT21 at three water-deficit levels (mild, moderate, and severe) during the elongation stage and gene expression was analyzed using microarray technology. Physiological parameters of sugarcane showed significant alterations in response to drought stress. Based on the expression profile of 15,593 sugarcane genes, 1,501 (9.6%) genes were differentially expressed under different water-level treatments; 821 genes were upregulated and 680 genes were downregulated. A gene similarity analysis showed that approximately 62.6% of the differentially expressed genes shared homology with functional proteins. In a Gene Ontology (GO) analysis, 901 differentially expressed genes were assigned to 36 GO categories. Moreover, 325 differentially expressed genes were classified into 101 pathway categories involved in various processes, such as the biosynthesis of secondary metabolites, ribosomes, carbon metabolism, etc. In addition, some unannotated genes were detected; these may provide a basis for studies of water-deficit tolerance. The reliability of the observed expression patterns was confirmed by RT-PCR. The results of this study may help identify useful genes for improving drought tolerance in sugarcane. PMID:27170459

  6. A new algorithm for computational image analysis of deformable motion at high spatial and temporal resolution applied to root growth. Roughly uniform elongation in the meristem and also, after an abrupt acceleration, in the elongation zone.

    PubMed

    van der Weele, Corine M; Jiang, Hai S; Palaniappan, Krishnan K; Ivanov, Viktor B; Palaniappan, Kannapan; Baskin, Tobias I

    2003-07-01

    A requirement for understanding morphogenesis is being able to quantify expansion at the cellular scale. Here, we present new software (RootflowRT) for measuring the expansion profile of a growing root at high spatial and temporal resolution. The software implements an image processing algorithm using a novel combination of optical flow methods for deformable motion. The algorithm operates on a stack of nine images with a given time interval between each (usually 10 s) and quantifies velocity confidently at most pixels of the image. The root does not need to be marked. The software calculates components of motion parallel and perpendicular to the local tangent of the root's midline. A variation of the software has been developed that reports the overall root growth rate versus time. Using this software, we find that the growth zone of the root can be divided into two distinct regions, an apical region where the rate of motion, i.e. velocity, rises gradually with position and a subapical region where velocity rises steeply with position. In both zones, velocity increases almost linearly with position, and the transition between zones is abrupt. We observed this pattern for roots of Arabidopsis, tomato (Lycopersicon lycopersicum), lettuce (Lactuca sativa), alyssum (Aurinia saxatilis), and timothy (Phleum pratense). These velocity profiles imply that relative elongation rate is regulated in a step-wise fashion, being low but roughly uniform within the meristem and then becoming high, but again roughly uniform, within the zone of elongation. The executable code for RootflowRT is available from the corresponding author on request.

  7. A New Algorithm for Computational Image Analysis of Deformable Motion at High Spatial and Temporal Resolution Applied to Root Growth. Roughly Uniform Elongation in the Meristem and Also, after an Abrupt Acceleration, in the Elongation Zone1

    PubMed Central

    van der Weele, Corine M.; Jiang, Hai S.; Palaniappan, Krishnan K.; Ivanov, Viktor B.; Palaniappan, Kannapan; Baskin, Tobias I.

    2003-01-01

    A requirement for understanding morphogenesis is being able to quantify expansion at the cellular scale. Here, we present new software (RootflowRT) for measuring the expansion profile of a growing root at high spatial and temporal resolution. The software implements an image processing algorithm using a novel combination of optical flow methods for deformable motion. The algorithm operates on a stack of nine images with a given time interval between each (usually 10 s) and quantifies velocity confidently at most pixels of the image. The root does not need to be marked. The software calculates components of motion parallel and perpendicular to the local tangent of the root's midline. A variation of the software has been developed that reports the overall root growth rate versus time. Using this software, we find that the growth zone of the root can be divided into two distinct regions, an apical region where the rate of motion, i.e. velocity, rises gradually with position and a subapical region where velocity rises steeply with position. In both zones, velocity increases almost linearly with position, and the transition between zones is abrupt. We observed this pattern for roots of Arabidopsis, tomato (Lycopersicon lycopersicum), lettuce (Lactuca sativa), alyssum (Aurinia saxatilis), and timothy (Phleum pratense). These velocity profiles imply that relative elongation rate is regulated in a step-wise fashion, being low but roughly uniform within the meristem and then becoming high, but again roughly uniform, within the zone of elongation. The executable code for RootflowRT is available from the corresponding author on request. PMID:12857796

  8. Long-distance signals regulating stomatal conductance and leaf growth in tomato (Lycopersicon esculentum) plants subjected to partial root-zone drying.

    PubMed

    Sobeih, Wagdy Y; Dodd, Ian C; Bacon, Mark A; Grierson, Donald; Davies, William J

    2004-11-01

    Tomato (Lycopersicon esculentum Mill. cv. Ailsa Craig) plants were grown with roots split between two soil columns. After plant establishment, water was applied daily to one (partial root-zone drying-PRD) or both (well-watered control-WW) columns. Water was withheld from the other column in the PRD treatment, to expose some roots to drying soil. Soil and plant water status were monitored daily and throughout diurnal courses. Over 8 d, there were no treatment differences in leaf water potential (psileaf) even though soil moisture content of the upper 6 cm (theta) of the dry column in the PRD treatment decreased by up to 70%. Stomatal conductance (gs) of PRD plants decreased (relative to WW plants) when of the dry column decreased by 45%. Such closure coincided with increased xylem sap pH and did not require increased xylem sap abscisic acid (ABA) concentration ([X-ABA]). Detached leaflet ethylene evolution of PRD plants increased when of the dry column decreased by 55%, concurrent with decreased leaf elongation. The physiological significance of enhanced ethylene evolution of PRD plants was examined using a transgenic tomato (ACO1AS) with low stress-induced ethylene production. In response to PRD, ACO1AS and wild-type plants showed similar xylem sap pH, [X-ABA] and gs, but ACO1AS plants showed neither enhanced ethylene evolution nor significant reductions in leaf elongation. Combined use of genetic technologies to reduce ethylene production and agronomic technologies to sustain water status (such as PRD) may sustain plant growth under conditions where yield would otherwise be significantly reduced.

  9. Effects of radionuclide contamination on leaf litter decomposition in the Chernobyl exclusion zone.

    PubMed

    Bonzom, Jean-Marc; Hättenschwiler, Stephan; Lecomte-Pradines, Catherine; Chauvet, Eric; Gaschak, Sergey; Beaugelin-Seiller, Karine; Della-Vedova, Claire; Dubourg, Nicolas; Maksimenko, Andrey; Garnier-Laplace, Jacqueline; Adam-Guillermin, Christelle

    2016-08-15

    The effects of radioactive contamination on ecosystem processes such as litter decomposition remain largely unknown. Because radionuclides accumulated in soil and plant biomass can be harmful for organisms, the functioning of ecosystems may be altered by radioactive contamination. Here, we tested the hypothesis that decomposition is impaired by increasing levels of radioactivity in the environment by exposing uncontaminated leaf litter from silver birch and black alder at (i) eleven distant forest sites differing in ambient radiation levels (0.22-15μGyh(-1)) and (ii) along a short distance gradient of radioactive contamination (1.2-29μGyh(-1)) within a single forest in the Chernobyl exclusion zone. In addition to measuring ambient external dose rates, we estimated the average total dose rates (ATDRs) absorbed by decomposers for an accurate estimate of dose-induced ecological consequences of radioactive pollution. Taking into account potential confounding factors (soil pH, moisture, texture, and organic carbon content), the results from the eleven distant forest sites, and from the single forest, showed increased litter mass loss with increasing ATDRs from 0.3 to 150μGyh(-1). This unexpected result may be due to (i) overcompensation of decomposer organisms exposed to radionuclides leading to a higher decomposer abundance (hormetic effect), and/or (ii) from preferred feeding by decomposers on the uncontaminated leaf litter used for our experiment compared to locally produced, contaminated leaf litter. Our data indicate that radio-contamination of forest ecosystems over more than two decades does not necessarily have detrimental effects on organic matter decay. However, further studies are needed to unravel the underlying mechanisms of the results reported here, in order to draw firmer conclusions on how radio-contamination affects decomposition and associated ecosystem processes. Copyright © 2016 Elsevier B.V. All rights reserved.

  10. Leaf ultraviolet optical properties along a latitudinal gradient in the Arctic-Alpine life zone

    SciTech Connect

    Robberecht, R.; Caldwell, M.M.; Billings, W.D.

    1980-06-01

    Leaf epidermal transmittance of terrestrial solar ultraviolet-B radiation (295 to 320 nm) was examined along a latitudinal gradient of solar uv-B radiation. In high uv-B radiation zones, e.g., equatorial and tropical regions, mean epidermal transmittance for the species examined was less than 2%. At higher latitudes, mean epidermal transmittance exceeded 5%. Although this latitudinal solar uv-B gradient represents more than a seven-fold difference in daily integrated uv-B irradiance, the calculated mean effective uv-B irradiance at the mesophyll of low-latitude species is not substantially different from that of species at higher latitudes. Species in high uv-B radiation environments appear to attenuate this radiation more effectively than those in lower irradiance environments. In most cases, absorption of uv-B in the epidermis is the major parameter effecting low transmittance. Reflectance from glabrous leaves is generally less than 10%. In some species, pubescent or glaucous leaf surfaces can reflect more than 40% of the uv-B radiation incident on a horizontal leaf, although such surface characteristics do not necessarily indicate high uv-B reflectance. Under controlled conditions, epidermal transmittance in Pisum sativum L. decreased in response to uv-B irradiation. The modification of epidermal transmittance, resulting in lower uv-B irradiance at the mesophyll, may represent a mechanism of plant acclimation to uv-B radiation. Such acclimation may have occurred in several wildland species of temperate-latitude origin that have invaded high uv-B irradiance equatorial and tropical regions.

  11. Full-scale Model Test for Anchorage Zone of Pylon: Error Analysis on Elongation of Annular Pre-Stressing Steel Strand

    NASA Astrophysics Data System (ADS)

    Ye, Xijun; Sun, Zhuo; Wang, Weifeng

    2017-06-01

    In order to study the mechanism of the annular Pre-stressing steel strands applied to cable-pylon anchorage zone, a full-scale model test and finite element analysis were conducted. Through the research on the full-scale model test of the U-shaped annular Pre-stressing steel strands for the Anchorage Zone of Guangzhou Bridge, the prestressing technique for the U-shaped annular Pre-stressing steel strands was investigated, and the stress distribution in the model were measured and analyzed. It can be found that the elongation of the U-shaped pre-stressing steel strands is greater than the actual theoretical limit, and the results of some project cases also showed that it is a common phenomenon. Finally, the reasons for thus problems and relative suggestions are proposed, they can be used as a reference to engineering practice.

  12. The locations and amounts of endogenous ions and elements in the cap and elongating zone of horizontally oriented roots of Zea mays L.: an electron-probe EDS study

    NASA Technical Reports Server (NTRS)

    Moore, R.; Cameron, I. L.; Hunter, K. E.; Olmos, D.; Smith, N. K.

    1987-01-01

    We used quantitative electron-probe energy-dispersive x-ray microanalysis to localize endogenous Na, Cl, K, P, S, Mg and Ca in cryofixed and freeze-dried cryosections of the cap (i.e. the putative site of graviperception) and elongating zone (i.e. site of gravicurvature) of horizontally oriented roots of Zea mays. Ca, Na, Cl, K and Mg accumulate along the lower side of caps of horizontally oriented roots. The most dramatic asymmetries of these ions occur in the apoplast, especially the mucilage. We could not detect any significant differences in the concentrations of these ions in the central cytoplasm of columella cells along the upper and lower sides of caps of horizontally-oriented roots. However, the increased amounts of Na, Cl, K and Mg in the longitudinal walls of columella cells along the lower side of the cap suggest that these ions may move down through the columella tissue of horizontally-oriented roots. Ca also accumulates (largely in the mucilage) along the lower side of the elongating zone of horizontally-oriented roots, while Na, P, Cl and K tend to accumulate along the upper side of the elongating zone. Of these ions, only K increases in concentration in the cytoplasm and longitudinal walls of cortical cells in the upper vs lower sides of the elongating zone. These results indicate that (1) gravity-induced asymmetries of ions differ significantly in the cap and elongating zone of graviresponding roots, (2) Ca accumulates along the lower side of the cap and elongating zone of graviresponding roots, (3) increased growth of the upper side of the elongating zone of horizontally-oriented roots correlates positively with increased amounts of K in the cytoplasm and longitudinal walls of cortical cells, and (4) the apoplast (especially the mucilage) may be an important component of the pathway via which ions move in graviresponding rots of Zea mays. These results are discussed relative to mechanisms for graviperception and gravicurvature of roots.

  13. The locations and amounts of endogenous ions and elements in the cap and elongating zone of horizontally oriented roots of Zea mays L.: an electron-probe EDS study

    NASA Technical Reports Server (NTRS)

    Moore, R.; Cameron, I. L.; Hunter, K. E.; Olmos, D.; Smith, N. K.

    1987-01-01

    We used quantitative electron-probe energy-dispersive x-ray microanalysis to localize endogenous Na, Cl, K, P, S, Mg and Ca in cryofixed and freeze-dried cryosections of the cap (i.e. the putative site of graviperception) and elongating zone (i.e. site of gravicurvature) of horizontally oriented roots of Zea mays. Ca, Na, Cl, K and Mg accumulate along the lower side of caps of horizontally oriented roots. The most dramatic asymmetries of these ions occur in the apoplast, especially the mucilage. We could not detect any significant differences in the concentrations of these ions in the central cytoplasm of columella cells along the upper and lower sides of caps of horizontally-oriented roots. However, the increased amounts of Na, Cl, K and Mg in the longitudinal walls of columella cells along the lower side of the cap suggest that these ions may move down through the columella tissue of horizontally-oriented roots. Ca also accumulates (largely in the mucilage) along the lower side of the elongating zone of horizontally-oriented roots, while Na, P, Cl and K tend to accumulate along the upper side of the elongating zone. Of these ions, only K increases in concentration in the cytoplasm and longitudinal walls of cortical cells in the upper vs lower sides of the elongating zone. These results indicate that (1) gravity-induced asymmetries of ions differ significantly in the cap and elongating zone of graviresponding roots, (2) Ca accumulates along the lower side of the cap and elongating zone of graviresponding roots, (3) increased growth of the upper side of the elongating zone of horizontally-oriented roots correlates positively with increased amounts of K in the cytoplasm and longitudinal walls of cortical cells, and (4) the apoplast (especially the mucilage) may be an important component of the pathway via which ions move in graviresponding rots of Zea mays. These results are discussed relative to mechanisms for graviperception and gravicurvature of roots.

  14. Transcription elongation

    PubMed Central

    Imashimizu, Masahiko; Shimamoto, Nobuo; Oshima, Taku; Kashlev, Mikhail

    2014-01-01

    Regulation of transcription elongation via pausing of RNA polymerase has multiple physiological roles. The pausing mechanism depends on the sequence heterogeneity of the DNA being transcribed, as well as on certain interactions of polymerase with specific DNA sequences. In order to describe the mechanism of regulation, we introduce the concept of heterogeneity into the previously proposed alternative models of elongation, power stroke and Brownian ratchet. We also discuss molecular origins and physiological significances of the heterogeneity. PMID:25764114

  15. Functional traits drive the contribution of solar radiation to leaf litter decomposition among multiple arid-zone species

    PubMed Central

    Pan, Xu; Song, Yao-Bin; Liu, Guo-Fang; Hu, Yu-Kun; Ye, Xue-Hua; Cornwell, William K.; Prinzing, Andreas; Dong, Ming; Cornelissen, Johannes H.C.

    2015-01-01

    In arid zones, strong solar radiation has important consequences for ecosystem processes. To better understand carbon and nutrient dynamics, it is important to know the contribution of solar radiation to leaf litter decomposition of different arid-zone species. Here we investigated: (1) whether such contribution varies among plant species at given irradiance regime, (2) whether interspecific variation in such contribution correlates with interspecific variation in the decomposition rate under shade; and (3) whether this correlation can be explained by leaf traits. We conducted a factorial experiment to determine the effects of solar radiation and environmental moisture for the mass loss and the decomposition constant k-values of 13 species litters collected in Northern China. The contribution of solar radiation to leaf litter decomposition varied significantly among species. Solar radiation accelerated decomposition in particular in the species that already decompose quickly under shade. Functional traits, notably specific leaf area, might predict the interspecific variation in that contribution. Our results provide the first empirical evidence for how the effect of solar radiation on decomposition varies among multiple species. Thus, the effect of solar radiation on the carbon flux between biosphere and atmosphere may depend on the species composition of the vegetation. PMID:26282711

  16. Functional traits drive the contribution of solar radiation to leaf litter decomposition among multiple arid-zone species.

    PubMed

    Pan, Xu; Song, Yao-Bin; Liu, Guo-Fang; Hu, Yu-Kun; Ye, Xue-Hua; Cornwell, William K; Prinzing, Andreas; Dong, Ming; Cornelissen, Johannes H C

    2015-08-18

    In arid zones, strong solar radiation has important consequences for ecosystem processes. To better understand carbon and nutrient dynamics, it is important to know the contribution of solar radiation to leaf litter decomposition of different arid-zone species. Here we investigated: (1) whether such contribution varies among plant species at given irradiance regime, (2) whether interspecific variation in such contribution correlates with interspecific variation in the decomposition rate under shade; and (3) whether this correlation can be explained by leaf traits. We conducted a factorial experiment to determine the effects of solar radiation and environmental moisture for the mass loss and the decomposition constant k-values of 13 species litters collected in Northern China. The contribution of solar radiation to leaf litter decomposition varied significantly among species. Solar radiation accelerated decomposition in particular in the species that already decompose quickly under shade. Functional traits, notably specific leaf area, might predict the interspecific variation in that contribution. Our results provide the first empirical evidence for how the effect of solar radiation on decomposition varies among multiple species. Thus, the effect of solar radiation on the carbon flux between biosphere and atmosphere may depend on the species composition of the vegetation.

  17. Responses of Leaf-level Carbon Assimilation and Transpiration to Root-zone Water Potential Changes in a Subtropical Tree Species

    NASA Astrophysics Data System (ADS)

    Cicheng, Z.; Guan, H.; Han, G.; Zhang, X.

    2013-12-01

    Photosynthetic carbon assimilation in terrestrial ecosystems significantly contributes to global carbon balance in the atmosphere. While vegetation photosynthesizes to fix CO2, it simultaneously transpires H2O. These two interdependent processes are regulated by leaf stomata which are sensitive to environmental conditions (such as root zone soil moisture). Knowledge of the responses of leaf-level transpiration and carbon assimilation to a change of root-zone soil moisture condition is important to understand how these processes influence water balance and carbon sequestration in terrestrial ecosystems, and to understand the capacity of trees to cope with future climate changes.We will present the results of a one-year observational study on a subtropical evergreen broadleaf tree species (Osmanthus fragrans) in the central south China. The observations were carried out on two 8-year Osmanthus fragrans trees in a plantation site from 1 Sep, 2012 to 31 Aug, 2013. A portable infrared gas exchange analyzer (Li-6400, Li-COR, Inc., Lincoln, Nebraska, USA) was used to measure leaf photosynthesis and leaf transpiration on clear days. Root zone soil water potential was estimated from predawn stem water potential using stem psychrometers (ICT, Australia). Sap flow and micrometeorological data were also collected. The results show that the average leaf carbon assimilation rate at light saturation decreases quickly with the root zone water potential from 0 to -1 MPa, and slowly after the root zone water potential falls below -1 MPa. The average leaf transpiration at light saturation shows a similar pattern. Leaf-level water use efficiency increases slowly with a decrease of root-zone water potential from 0 to -1 MPa, and keeps constant when the root zone gets drier. This relationship provides a potential to estimate whole-tree carbon assimilation from sap flow measurements. Leaf assimilation rates at light saturation in early morning vs. root-zone water potential for Osmanthus

  18. Genotypical Differences in Aluminum Resistance of Maize Are Expressed in the Distal Part of the Transition Zone. Is Reduced Basipetal Auxin Flow Involved in Inhibition of Root Elongation by Aluminum?1

    PubMed Central

    Kollmeier, Malte; Felle, Hubert H.; Horst, Walter J.

    2000-01-01

    Short-term Al treatment (90 μm Al at pH 4.5 for 1 h) of the distal transition zone (DTZ; 1–2 mm from the root tip), which does not contribute significantly to root elongation, inhibited root elongation in the main elongation zone (EZ; 2.5–5 mm from the root tip) to the same extent as treatment of the entire maize (Zea mays) root apex. Application of Al to the EZ had no effect on root elongation. Higher genotypical resistance to Al applied to the entire root apex, and specifically to the DTZ, was expressed by less inhibition of root elongation, Al accumulation, and Al-induced callose formation, primarily in the DTZ. A characteristic pH profile along the surface of the root apex with a maximum of pH 5.3 in the DTZ was demonstrated. Al application induced a substantial flattening of the pH profile moreso in the Al-sensitive than in the Al-resistant cultivar. Application of indole-3-acetic acid to the EZ but not to the meristematic zone significantly alleviated the inhibition of root elongation induced by the application of Al to the DTZ. Basipetal transport of exogenously applied [3H]indole-3-acetic acid to the meristematic zone was significantly inhibited by Al application to the DTZ in the Al-sensitive maize cv Lixis. Our results provide evidence that the primary mechanisms of genotypical differences in Al resistance are located within the DTZ, and suggest a signaling pathway in the root apex mediating the Al signal between the DTZ and the EZ through basipetal auxin transport. PMID:10712559

  19. Water-sediment exchanges control microbial processes associated with leaf litter degradation in the hyporheic zone: a microcosm study.

    PubMed

    Navel, Simon; Mermillod-Blondin, Florian; Montuelle, Bernard; Chauvet, Eric; Simon, Laurent; Marmonier, Pierre

    2011-05-01

    The present study aimed to experimentally quantify the influence of a reduction of surface sediment permeability on microbial characteristics and ecological processes (respiration and leaf litter decomposition) occurring in the hyporheic zone (i.e. the sedimentary interface between surface water and groundwater). The physical structure of the water-sediment interface was manipulated by adding a 2-cm layer of coarse sand (unclogged systems) or fine sand (clogged systems) at the sediment surface of slow filtration columns filled with a heterogeneous gravel/sand sedimentary matrix. The influence of clogging was quantified through measurements of hydraulic conductivity, water chemistry, microbial abundances and activities and associated processes (decomposition of alder leaf litter inserted at a depth of 9 cm in sediments, oxygen and nitrate consumption by microorganisms). Fine sand deposits drastically reduced hydraulic conductivity (by around 8-fold in comparison with unclogged systems topped by coarse sand) and associated water flow, leading to a sharp decrease in oxygen (reaching less than 1 mg L(-1) at 3 cm depth) and nitrate concentrations with depth in sediments. The shift from aerobic to anaerobic conditions in clogged systems favoured the establishment of denitrifying bacteria living on sediments. Analyses performed on buried leaf litter showed a reduction by 30% of organic matter decomposition in clogged systems in comparison with unclogged systems. This reduction was linked to a negative influence of clogging on the activities and abundances of leaf-associated microorganisms. Finally, our study clearly demonstrated that microbial processes involved in organic matter decomposition were dependent on hydraulic conductivity and oxygen availability in the hyporheic zone.

  20. Cotton AnnGh3 encoding an annexin protein is preferentially expressed in fibers and promotes initiation and elongation of leaf trichomes in transgenic Arabidopsis.

    PubMed

    Li, Bing; Li, Deng-Di; Zhang, Jie; Xia, Hui; Wang, Xiu-Lan; Li, Ying; Li, Xue-Bao

    2013-10-01

    The annexins are a multifamily of calcium-regulated phospholipid-binding proteins. To investigate the roles of annexins in fiber development, four genes encoding putative annexin proteins were isolated from cotton (Gossypium hirsutum) and designated AnnGh3, AnnGh4, AnnGh5, and AnnGh6. Quantitative reverse transcription-polymerase chain reaction (qRT-PCR) results indicated that AnnGh3, AnnGh4, and AnnGh5 were preferentially expressed in fibers, while the transcripts of AnnGh6 were predominantly accumulated in roots. During fiber development, the transcripts of AnnGh3/4/5 genes were mainly accumulated in rapidly elongating fibers. With fiber cells further developed, their expression activity was dramatically declined to a relatively low level. In situ hybridization results indicated that AnnGh3 and AnnGh5 were expressed in initiating fiber cells (0-2 DPA). Additionally, their expression in fibers was also regulated by phytohormones and [Ca(2+)]. Subcellular localization analysis discovered that AnnGh3 protein was localized in the cytoplasm. Overexpression of AnnGh3 in Arabidopsis resulted in a significant increase in trichome density and length on leaves of the transgenic plants, suggesting that AnnGh3 may be involved in fiber cell initiation and elongation of cotton.

  1. Cell Wall Proteome in the Maize Primary Root Elongation Zone. II. Region-Specific Changes in Water Soluble and Lightly Ionically Bound Proteins under Water Deficit1[W][OA

    PubMed Central

    Zhu, Jinming; Alvarez, Sophie; Marsh, Ellen L.; LeNoble, Mary E.; Cho, In-Jeong; Sivaguru, Mayandi; Chen, Sixue; Nguyen, Henry T.; Wu, Yajun; Schachtman, Daniel P.; Sharp, Robert E.

    2007-01-01

    Previous work on the adaptation of maize (Zea mays) primary roots to water deficit showed that cell elongation is maintained preferentially toward the apex, and that this response involves modification of cell wall extension properties. To gain a comprehensive understanding of how cell wall protein (CWP) composition changes in association with the differential growth responses to water deficit in different regions of the elongation zone, a proteomics approach was used to examine water soluble and loosely ionically bound CWPs. The results revealed major and predominantly region-specific changes in protein profiles between well-watered and water-stressed roots. In total, 152 water deficit-responsive proteins were identified and categorized into five groups based on their potential function in the cell wall: reactive oxygen species (ROS) metabolism, defense and detoxification, hydrolases, carbohydrate metabolism, and other/unknown. The results indicate that stress-induced changes in CWPs involve multiple processes that are likely to regulate the response of cell elongation. In particular, the changes in protein abundance related to ROS metabolism predicted an increase in apoplastic ROS production in the apical region of the elongation zone of water-stressed roots. This was verified by quantification of hydrogen peroxide content in extracted apoplastic fluid and by in situ imaging of apoplastic ROS levels. This response could contribute directly to the enhancement of wall loosening in this region. This large-scale proteomic analysis provides novel insights into the complexity of mechanisms that regulate root growth under water deficit conditions and highlights the spatial differences in CWP composition in the root elongation zone. PMID:17951457

  2. Leaf-Induced Gibberellin Signaling Is Essential for Internode Elongation, Cambial Activity, and Fiber Differentiation in Tobacco Stems[C][W

    PubMed Central

    Dayan, Jonathan; Voronin, Nickolay; Gong, Fan; Sun, Tai-ping; Hedden, Peter; Fromm, Hillel; Aloni, Roni

    2012-01-01

    The gibberellins (GAs) are a group of endogenous compounds that promote the growth of most plant organs, including stem internodes. We show that in tobacco (Nicotiana tabacum) the presence of leaves is essential for the accumulation of bioactive GAs and their immediate precursors in the stem and consequently for normal stem elongation, cambial proliferation, and xylem fiber differentiation. These processes do not occur in the absence of maturing leaves but can be restored by application of C19-GAs, identifying the presence of leaves as a requirement for GA signaling in stems and revealing the fundamental role of GAs in secondary growth regulation. The use of reporter genes for GA activity and GA-directed DELLA protein degradation in Arabidopsis thaliana confirms the presence of a mobile signal from leaves to the stem that induces GA signaling. PMID:22253226

  3. NOTE: Elongated beamlets: a simple technique for segment and MU reduction for sMLC IMRT delivery on accelerators utilizing 5 mm leaf widths

    NASA Astrophysics Data System (ADS)

    Price, R. A., Jr.; Paskalev, K.; McNeeley, S.; Ma, C.-M.

    2005-10-01

    The focus of this work is to demonstrate the effects of using an elongated beamlet to achieve similar dose conformity as achieved with a square beamlet while reducing the number of segments and subsequent MU required. A series of 10 patients were planned for IMRT delivery to the prostate using minimum beamlet sizes of 5 × 5 mm2 (default scheme), 10 × 5 mm2 with the short axis parallel to the prostate rectum interface (scheme 1), and 10 × 5 mm2 with the short axis perpendicular to the prostate rectum interface (scheme 2). All other parameters between plans were left unchanged. Plans were appropriately normalized and evaluated for R65, R40, conformity index, total number of segments and MU. All plans were generated using the Corvus inverse planning system. The average number of segments in this study decreased by approximately 49% for both schemes 1 and 2. The subsequent number of MU required decreased by approximately 34.6%. The resultant modified modulation scaling factor (MSFmod) decreased by approximately 34.3%. Additionally, we found that each isodose distribution using scheme 2 would still meet our clinical acceptance criteria with no visible degradation in the dose distribution as compared with the default scheme. In conclusion, we have demonstrated that it is possible to achieve similar results as those obtained using a 5 × 5 mm2 beamlet with respect to target coverage and critical structure sparing by using strategically oriented elongated beamlets. This technique directly translates to a decreased MSFmod allowing for decreased leakage dose to the patient, a decreased risk of exceeding secondary shielding limits in pre-existing vaults, and shorter treatment times.

  4. Progressive Inhibition by Water Deficit of Cell Wall Extensibility and Growth along the Elongation Zone of Maize Roots Is Related to Increased Lignin Metabolism and Progressive Stelar Accumulation of Wall Phenolics1

    PubMed Central

    Fan, Ling; Linker, Raphael; Gepstein, Shimon; Tanimoto, Eiichi; Yamamoto, Ryoichi; Neumann, Peter M.

    2006-01-01

    Water deficit caused by addition of polyethylene glycol 6000 at −0.5 MPa water potential to well-aerated nutrient solution for 48 h inhibited the elongation of maize (Zea mays) seedling primary roots. Segmental growth rates in the root elongation zone were maintained 0 to 3 mm behind the tip, but in comparison with well-watered control roots, progressive growth inhibition was initiated by water deficit as expanding cells crossed the region 3 to 9 mm behind the tip. The mechanical extensibility of the cell walls was also progressively inhibited. We investigated the possible involvement in root growth inhibition by water deficit of alterations in metabolism and accumulation of wall-linked phenolic substances. Water deficit increased expression in the root elongation zone of transcripts of two genes involved in lignin biosynthesis, cinnamoyl-CoA reductase 1 and 2, after only 1 h, i.e. before decreases in wall extensibility. Further increases in transcript expression and increased lignin staining were detected after 48 h. Progressive stress-induced increases in wall-linked phenolics at 3 to 6 and 6 to 9 mm behind the root tip were detected by comparing Fourier transform infrared spectra and UV-fluorescence images of isolated cell walls from water deficit and control roots. Increased UV fluorescence and lignin staining colocated to vascular tissues in the stele. Longitudinal bisection of the elongation zone resulted in inward curvature, suggesting that inner, stelar tissues were also rate limiting for root growth. We suggest that spatially localized changes in wall-phenolic metabolism are involved in the progressive inhibition of wall extensibility and root growth and may facilitate root acclimation to drying environments. PMID:16384904

  5. Progressive inhibition by water deficit of cell wall extensibility and growth along the elongation zone of maize roots is related to increased lignin metabolism and progressive stelar accumulation of wall phenolics.

    PubMed

    Fan, Ling; Linker, Raphael; Gepstein, Shimon; Tanimoto, Eiichi; Yamamoto, Ryoichi; Neumann, Peter M

    2006-02-01

    Water deficit caused by addition of polyethylene glycol 6000 at -0.5 MPa water potential to well-aerated nutrient solution for 48 h inhibited the elongation of maize (Zea mays) seedling primary roots. Segmental growth rates in the root elongation zone were maintained 0 to 3 mm behind the tip, but in comparison with well-watered control roots, progressive growth inhibition was initiated by water deficit as expanding cells crossed the region 3 to 9 mm behind the tip. The mechanical extensibility of the cell walls was also progressively inhibited. We investigated the possible involvement in root growth inhibition by water deficit of alterations in metabolism and accumulation of wall-linked phenolic substances. Water deficit increased expression in the root elongation zone of transcripts of two genes involved in lignin biosynthesis, cinnamoyl-CoA reductase 1 and 2, after only 1 h, i.e. before decreases in wall extensibility. Further increases in transcript expression and increased lignin staining were detected after 48 h. Progressive stress-induced increases in wall-linked phenolics at 3 to 6 and 6 to 9 mm behind the root tip were detected by comparing Fourier transform infrared spectra and UV-fluorescence images of isolated cell walls from water deficit and control roots. Increased UV fluorescence and lignin staining colocated to vascular tissues in the stele. Longitudinal bisection of the elongation zone resulted in inward curvature, suggesting that inner, stelar tissues were also rate limiting for root growth. We suggest that spatially localized changes in wall-phenolic metabolism are involved in the progressive inhibition of wall extensibility and root growth and may facilitate root acclimation to drying environments.

  6. Effect of altering the root-zone temperature on growth, translocation, carbon exchange rate, and leaf starch accumulation in the tomato.

    PubMed

    Hurewitz, J; Janes, H W

    1983-09-01

    Tomato seedlings (Lycopersicon esculentum Mill. cv Vendor) were grown hydroponically with their root systems maintained at a constant temperature for a 2-week period commencing with the appearance of the first true leaf. Based on fresh and dry weight and leaf area, the optimal root-zone temperature for seedling growth was 30 degrees C. The carbon exchange rate of the leaves was also found to increase with rising root-zone temperature up to 30 degrees C. However, a more complex relationship seems to exist between root-zone temperature and the accumulation of (14)C-labeled assimilates in the roots; inasmuch as there is no enhancement in this accumulation at the most growth promoting root-zone temperatures (22-30 degrees C).

  7. Testing the 'hybrid susceptibility' and 'phenological sink' hypotheses using the P. balsamifera - P. deltoides hybrid zone and septoria leaf spot [Septoria musiva].

    PubMed

    LeBoldus, Jared M; Isabel, Nathalie; Floate, Kevin D; Blenis, Peter; Thomas, Barb R

    2013-01-01

    Hybrid genotypes that arise between plant species frequently have increased susceptibility to arthropod pests and fungal pathogens. This pattern has been attributed to the breakdown of plant defenses ('Hybrid susceptibility' hypothesis) and (or) to extended periods of susceptibility attributed to plant phenologies in zones of species overlap and (or) hybridization ('phenological sink' hypothesis). We examined these hypotheses by assessing the susceptibility of parental and hybrid Populus host genotypes to a leaf spot disease caused by the fungal pathogen Septoria musiva. For this purpose, 214 genotypes were obtained from morphologically pure zones of P. balsamifera and P. deltoides, and from an intervening zone of overlap and hybridization on the drainage of the Red Deer River, Alberta, Canada. Genotypes were identified as P. balsamifera, P. deltoides, or hybrid using a suite of 27 species-specific SNP markers. Initially the genetic structure of the hybrid zone was characterized with 27.7% of trees classified as admixed individuals. To test the hybrid susceptibility hypothesis, a subset of 52 genotypes was inoculated with four isolates of S. musiva. Levels of susceptibility were P. balsamifera > F1 hybrid > P. deltoides. A further 53 genotypes were grown in a common garden to assess the effect of genotype on variation in leaf phenology. Leaf phenology was more variable within the category of hybrid genotypes than within categories of either parental species. Leaf phenology was also more variable for the category of trees originating in the hybrid (P. balsamifera - P. deltoides [hybrid and parental genotypes combined]) zone than in adjacent pure zones of the parental species. The results from the inoculation experiment support the hybrid intermediacy hypothesis. The results from the common garden experiment support the 'phenological sink' hypothesis. These findings have greatly increased our understanding of the epidemiology and ecology of fungal pathogens in plant

  8. Testing the ‘Hybrid Susceptibility’ and ‘Phenological Sink’ Hypotheses Using the P. balsamifera – P. deltoides Hybrid Zone and Septoria Leaf Spot [Septoria musiva

    PubMed Central

    LeBoldus, Jared M.; Isabel, Nathalie; Floate, Kevin D.; Blenis, Peter; Thomas, Barb R.

    2013-01-01

    Hybrid genotypes that arise between plant species frequently have increased susceptibility to arthropod pests and fungal pathogens. This pattern has been attributed to the breakdown of plant defenses (‘Hybrid susceptibility’ hypothesis) and (or) to extended periods of susceptibility attributed to plant phenologies in zones of species overlap and (or) hybridization (‘phenological sink’ hypothesis). We examined these hypotheses by assessing the susceptibility of parental and hybrid Populus host genotypes to a leaf spot disease caused by the fungal pathogen Septoria musiva. For this purpose, 214 genotypes were obtained from morphologically pure zones of P. balsamifera and P. deltoides, and from an intervening zone of overlap and hybridization on the drainage of the Red Deer River, Alberta, Canada. Genotypes were identified as P. balsamifera, P. deltoides, or hybrid using a suite of 27 species-specific SNP markers. Initially the genetic structure of the hybrid zone was characterized with 27.7% of trees classified as admixed individuals. To test the hybrid susceptibility hypothesis, a subset of 52 genotypes was inoculated with four isolates of S. musiva. Levels of susceptibility were P. balsamifera > F1 hybrid > P. deltoides. A further 53 genotypes were grown in a common garden to assess the effect of genotype on variation in leaf phenology. Leaf phenology was more variable within the category of hybrid genotypes than within categories of either parental species. Leaf phenology was also more variable for the category of trees originating in the hybrid (P. balsamifera – P. deltoides [hybrid and parental genotypes combined]) zone than in adjacent pure zones of the parental species. The results from the inoculation experiment support the hybrid intermediacy hypothesis. The results from the common garden experiment support the ‘phenological sink’ hypothesis. These findings have greatly increased our understanding of the epidemiology and ecology of fungal

  9. Core cell cycle regulatory genes in rice and their expression profiles across the growth zone of the leaf.

    PubMed

    Pettkó-Szandtner, A; Cserháti, M; Barrôco, R M; Hariharan, S; Dudits, D; Beemster, G T S

    2015-11-01

    Rice (Oryza sativa L.) as a model and crop plant with a sequenced genome offers an outstanding experimental system for discovering and functionally analyzing the major cell cycle control elements in a cereal species. In this study, we identified the core cell cycle genes in the rice genome through a hidden Markov model search and multiple alignments supported with the use of short protein sequence probes. In total we present 55 rice putative cell cycle genes with locus identity, chromosomal location, approximate chromosome position and EST accession number. These cell cycle genes include nine cyclin dependent-kinase (CDK) genes, 27 cyclin genes, one CKS gene, two RBR genes, nine E2F/DP/DEL genes, six KRP genes, and one WEE gene. We also provide characteristic protein sequence signatures encoded by CDK and cyclin gene variants. Promoter analysis by the FootPrinter program discovered several motifs in the regulatory region of the core cell cycle genes. As a first step towards functional characterization we performed transcript analysis by RT-PCR to determine gene specific variation in transcript levels along the rice leaves. The meristematic zone of the leaves where cells are actively dividing was identified based on kinematic analysis and flow cytometry. As expected, expression of the majority of cell cycle genes was exclusively associated with the meristematic region. However genes such as different D-type cyclins, DEL1, KRP1/3, and RBR2 were also expressed in leaf segments representing the transition zone in which cells start differentiation.

  10. Reactive oxygen species regulate leaf pulvinus abscission zone cell separation in response to water-deficit stress in cassava

    PubMed Central

    Liao, Wenbin; Wang, Gan; Li, Yayun; Wang, Bin; Zhang, Peng; Peng, Ming

    2016-01-01

    Cassava (Manihot esculenta Crantz) plant resists water-deficit stress by shedding leaves leading to adaptive water-deficit condition. Transcriptomic, physiological, cellular, molecular, metabolic, and transgenic methods were used to study the mechanism of cassava abscission zone (AZ) cell separation under water-deficit stress. Microscopic observation indicated that AZ cell separation initiated at the later stages during water-deficit stress. Transcriptome profiling of AZ suggested that differential expression genes of AZ under stress mainly participate in reactive oxygen species (ROS) pathway. The key genes involved in hydrogen peroxide biosynthesis and metabolism showed significantly higher expression levels in AZ than non-separating tissues adjacent to the AZ under stress. Significantly higher levels of hydrogen peroxide correlated with hydrogen peroxide biosynthesis related genes and AZ cell separation was detected by microscopic observation, colorimetric detection and GC-MS analyses under stress. Co-overexpression of the ROS-scavenging proteins SOD and CAT1 in cassava decreased the levels of hydrogen peroxide in AZ under water-deficit stress. The cell separation of the pulvinus AZ also delayed in co-overexpression of the ROS-scavenging proteins SOD and CAT1 plants both in vitro and at the plant level. Together, the results indicated that ROS play an important regulatory role in the process of cassava leaf abscission under water-deficit stress. PMID:26899473

  11. Testing Earth System Model Assumptions of Photosynthetic Parameters with in situ Leaf Measurements from a Temperate Zone Forest.

    NASA Astrophysics Data System (ADS)

    Cheng, S. J.; Thomas, R. Q.; Wilkening, J. V.; Curtis, P.; Sharkey, T. D.; Nadelhoffer, K. J.

    2015-12-01

    Estimates of global land CO2 uptake vary widely across Earth system models. This uncertainty around model estimates of land-atmosphere CO2 fluxes may result from differences in how models parameterize and scale photosynthesis from the leaf-to-global level. To test model assumptions about photosynthesis, we derive rates of maximum carboxylation (Vc,max), electron transport (J), and triose phosphate utilization (TPU) from in situ leaf measurements from a forest representative of the Great Lakes region. Leaf-level gas exchange measurements were collected across a temperature range from sun and shade leaves of canopy-dominant tree species typically grouped into the same plant functional type. We evaluate the influence of short-term increases in leaf temperature, nitrogen per leaf area (Narea), species, and leaf light environment on Vc,max, J, and TPU by testing contrasting model equations that isolate the influence of these factors on these rate-limiting steps in leaf photosynthesis. Results indicate that patterns in Vc,max are best explained by a model that includes temperature and Narea. However, J varied with species and leaf light environment in addition to temperature. TPU also varied with leaf light environment and possibly with temperature. These variations in J and TPU with species or between sun and shade leaves suggest that plant traits outside of Narea are needed to explain patterns in J and TPU. This study provides in situ evidence on how Vc,max, J, and TPU vary within a forest canopy and highlight how leaf responses to changes in climate, forest species composition, and canopy structure may alter forest CO2 uptake.

  12. Leaf Development

    PubMed Central

    Tsukaya, Hirokazu

    2002-01-01

    The shoot system is the basic unit of development of seed plants and is composed of a leaf, a stem, and a lateral bud that differentiates into a lateral shoot. The most specialized organ in angiosperms, the flower, can be considered to be part of the same shoot system since floral organs, such as the sepal, petal, stamen, and carpel, are all modified leaves. Scales, bracts, and certain kinds of needle are also derived from leaves. Thus, an understanding of leaf development is critical to an understanding of shoot development. Moreover, leaves play important roles in photosynthesis, respiration and photoperception. Thus, a full understanding of leaves is directly related to a full understanding of seed plants. The details of leaf development remain unclear. The difficulties encountered in studies of leaf development, in particular in dicotyledonous plants such as Arabidopsis thaliana (L.) Henyn., are derived from the complex process of leaf development, during which the division and elongation of cells occur at the same time and in the same region of the leaf primordium (Maksymowych, 1963; Poethig and Sussex, 1985). Thus, we cannot divide the entire process into unit processes in accordance with the tenets of classical anatomy. Genetic approaches in Arabidopsis, a model plant (Meyerowitz and Pruitt, 1985), have provided a powerful tool for studies of mechanisms of leaf development in dicotyledonous plants, and various aspects of the mechanisms that control leaf development have been revealed in recent developmental and molecular genetic studies of Arabidopsis (for reviews, see Tsukaya, 1995 and 1998; Van Lijsebettens and Clarke, 1998; Sinha, 1999; Van Volkenburgh, 1999; Tsukaya, 2000; Byrne et al., 2001; Dengler and Kang, 2001; Dengler and Tsukaya, 2001; Tsukaya, 2001). In this review, we shall examine the information that is currently available about various mechanisms of leaf development in Arabidopsis. Vascular patterning is also an important factor in the

  13. Elongated grains in a hopper

    NASA Astrophysics Data System (ADS)

    Börzsönyi, Tamás; Somfai, Ellák; Szabó, Balázs; Wegner, Sandra; Ashour, Ahmed; Stannarius, Ralf

    2017-06-01

    Flow and clogging of granular materials in a 3-dimensional hopper is investigated experimentally. We use X-ray tomography and optical methods to study this phenomenon for spherical and elongated particles. The X-ray tomograms provide information on the bulk of the hopper filling, and allow to determine the particle positions and orientations inside the silo, as well as spatial variations of the local packing density. We find that particles show a preferred orientation and thereby an enhanced order in the flowing zone of the silo. Similarly to simple shear flows, the average orientation of the particles is not parallel to the streamlines but encloses a certain angle with them. The clogged state is characterized by a dome, i. e. the geometry of the layer of grains blocking the outflow. The number of grains forming this blocking layer is larger for elongated grains compared to the case of spheres of the same volume.

  14. Effect of apoplastic solutes on water potential in elongating sugarcane leaves.

    PubMed

    Meinzer, F C; Moore, P H

    1988-03-01

    Solute concentration in the apoplast of growing sugarcane (Saccharum spp. hybrid) leaves was measured using one direct and several indirect methods. The osmotic potential of apoplast solution collected directly by centrifugation of noninfiltrated tissue segments ranged from -0.25 megapascal in mature tissue to -0.35 megapascal in tissue just outside the elongation zone. The presence of these solutes in the apoplast manifested itself as a tissue water potential equal to the apoplast osmotic potential. Since the tissue was not elongating, the measurements were not influenced by growth-induced water uptake and no significant tension was detected with the pressure chamber. Further evidence for a significant apoplast solute concentration was obtained from pressure exudation experiments and comparison of methods for estimating tissue apoplast water fraction. For elongating leaf tissue the centrifugation method could not be used to obtain direct measurements of apoplast solute concentration. However, several other observations suggested that the apoplast water potential of -0.35 to -0.45 megapascal in elongating tissue had a significant osmotic component and small, but significant tension component. Results of experiments in which exudate was collected from pressurized tissue segments of different ages suggested that a tissue age-dependent dynamic equilibrium existed between intra- and extracellular solutes.

  15. Carbon Isotope Composition of Nighttime Leaf-Respired CO2 in the Agricultural-Pastoral Zone of the Songnen Plain, Northeast China

    PubMed Central

    Cui, Haiying; Wang, Yunbo; Jiang, Qi; Chen, Shiping; Ma, Jian-Ying; Sun, Wei

    2015-01-01

    Variations in the carbon isotope signature of leaf dark-respired CO2 (δ13CR) within a single night is a widely observed phenomenon. However, it is unclear whether there are plant functional type differences with regard to the amplitude of the nighttime variation in δ13CR. These differences, if present, would be important for interpreting the short-term variations in the stable carbon signature of ecosystem respiration and the partitioning of carbon fluxes. To assess the plant functional type differences relating to the magnitude of the nighttime variation in δ13CR and the respiratory apparent fractionation, we measured the δ13CR, the leaf gas exchange, and the δ13C of the respiratory substrates of 22 species present in the agricultural-pastoral zone of the Songnen Plain, northeast China. The species studied were grouped into C3 and C4 plants, trees, grasses, and herbs. A significant nocturnal shift in δ13CR was detected in 20 of the studied species, with the magnitude of the shift ranging from 1‰ to 5.8‰. The magnitude of the nighttime variation in δ13CR was strongly correlated with the daytime cumulative carbon assimilation, which suggests that variation in δ13CR were influenced, to some extent, by changes in the contribution of malate decarboxylation to total respiratory CO2 flux. There were no differences in the magnitude of the nighttime variation in δ13CR between the C3 and C4 plants, as well as among the woody plants, herbs and graminoids. Leaf respired CO2 was enriched in 13C compared to biomass, soluble carbohydrates and lipids; however the magnitude of enrichment differed between 8 pm and 4 am, which were mainly caused by the changes in δ13CR. We also detected the plant functional type differences in respiratory apparent fractionation relative to biomass at 4 am, which suggests that caution should be exercised when using the δ13C of bulk leaf material as a proxy for the δ13C of leaf-respired CO2. PMID:26356083

  16. Carbon Isotope Composition of Nighttime Leaf-Respired CO2 in the Agricultural-Pastoral Zone of the Songnen Plain, Northeast China.

    PubMed

    Cui, Haiying; Wang, Yunbo; Jiang, Qi; Chen, Shiping; Ma, Jian-Ying; Sun, Wei

    2015-01-01

    Variations in the carbon isotope signature of leaf dark-respired CO2 (δ13CR) within a single night is a widely observed phenomenon. However, it is unclear whether there are plant functional type differences with regard to the amplitude of the nighttime variation in δ13CR. These differences, if present, would be important for interpreting the short-term variations in the stable carbon signature of ecosystem respiration and the partitioning of carbon fluxes. To assess the plant functional type differences relating to the magnitude of the nighttime variation in δ13CR and the respiratory apparent fractionation, we measured the δ13CR, the leaf gas exchange, and the δ13C of the respiratory substrates of 22 species present in the agricultural-pastoral zone of the Songnen Plain, northeast China. The species studied were grouped into C3 and C4 plants, trees, grasses, and herbs. A significant nocturnal shift in δ13CR was detected in 20 of the studied species, with the magnitude of the shift ranging from 1‰ to 5.8‰. The magnitude of the nighttime variation in δ13CR was strongly correlated with the daytime cumulative carbon assimilation, which suggests that variation in δ13CR were influenced, to some extent, by changes in the contribution of malate decarboxylation to total respiratory CO2 flux. There were no differences in the magnitude of the nighttime variation in δ13CR between the C3 and C4 plants, as well as among the woody plants, herbs and graminoids. Leaf respired CO2 was enriched in 13C compared to biomass, soluble carbohydrates and lipids; however the magnitude of enrichment differed between 8 pm and 4 am, which were mainly caused by the changes in δ13CR. We also detected the plant functional type differences in respiratory apparent fractionation relative to biomass at 4 am, which suggests that caution should be exercised when using the δ13C of bulk leaf material as a proxy for the δ13C of leaf-respired CO2.

  17. Physiological responses of potato (Solanum tuberosum L.) to partial root-zone drying: ABA signalling, leaf gas exchange, and water use efficiency.

    PubMed

    Liu, Fulai; Shahnazari, Ali; Andersen, Mathias N; Jacobsen, Sven-Erik; Jensen, Christian R

    2006-01-01

    The physiological responses of potato (Solanum tuberosum L. cv. Folva) to partial root-zone drying (PRD) were investigated in potted plants in a greenhouse (GH) and in plants grown in the field under an automatic rain-out-shelter. In the GH, irrigation was applied daily to the whole root system (FI), or to one-half of the root system while the other half was dried, for 9 d. In the field, the plants were drip irrigated either to the whole root system near field capacity (FI) or using 70% water of FI to one side of the roots, and shifted to the other side every 5-10 d (PRD). PRD plants had a similar midday leaf water potential to that of FI, whereas in the GH their root water potential (Psi(r)) was significantly lowered after 5 d. Stomatal conductance (g(s)) was more sensitive to PRD than photosynthesis (A) particularly in the field, leading to greater intrinsic water use efficiency (WUE) (i.e. A/g(s)) in PRD than in FI plants on several days. In PRD, the xylem sap abscisic acid concentration ([ABA](xylem)) increased exponentially with decreasing Psi(r); and the relative [ABA](xylem) (PRD/FI) increased exponentially as the fraction of transpirable soil water (FTSW) in the drying side decreased. In the field, the leaf area index was slightly less in PRD than in FI treatment, while tuber biomass was similar for the two treatments. Compared with FI, PRD treatment saved 30% water and increased crop water use efficiency (WUE) by 59%. Restrictions on leaf area expansion and g(s) by PRD-induced ABA signals might have contributed to reduced water use and increased WUE.

  18. Regulation of Growth Response to Water Stress in the Soybean Primary Root. I. Proteomic Analysis Reveals Region-Specific Regulation of Phenylpropanoid Metabolism and Control of Free Iron in the Elongation Zone.

    USDA-ARS?s Scientific Manuscript database

    In water-stressed soybean primary roots, elongation was maintained at well-watered rates in the apical 4 mm (region 1) but was progressively inhibited in the 4-8 mm region (region 2), which exhibits maximum elongation in well-watered roots. These responses are similar to previous results for the mai...

  19. Synthesis of Elongated Microcapsules

    NASA Technical Reports Server (NTRS)

    Li, Wenyan; Buhrow, Jerry; Calle, Luz M.

    2011-01-01

    One of the factors that influence the effectiveness of self-healing in functional materials is the amount of liquid healing agents that can be delivered to the damaged area. The use of hollow tubes or fibers and the more sophisticated micro-vascular networks has been proposed as a way to increase the amount of healing agents that can be released when damage is inflicted. Although these systems might be effective in some specific applications, they are not practical for coatings applications. One possible practical way to increase the healing efficiency is to use microcapsules with high-aspect-ratios, or elongated microcapsules. It is understood that elongated microcapsules will be more efficient because they can release more healing agent than a spherical microcapsule when a crack is initiated in the coating. Although the potential advantage of using elongated microcapsules for self healing applications is clear, it is very difficult to make elongated microcapsules from an emulsion system because spherical microcapsules are normally formed due to the interfacial tension between the dispersed phase and the continuous phase. This paper describes the two methods that have been developed by the authors to synthesize elongated microcapsules. The first method involves the use of an emulsion with intermediate stability and the second involves the application of mechanical shear conditions to the emulsion.

  20. Differential methylation during maize leaf growth targets developmentally regulated genes.

    PubMed

    Candaele, Jasper; Demuynck, Kirin; Mosoti, Douglas; Beemster, Gerrit T S; Inzé, Dirk; Nelissen, Hilde

    2014-03-01

    DNA methylation is an important and widespread epigenetic modification in plant genomes, mediated by DNA methyltransferases (DMTs). DNA methylation is known to play a role in genome protection, regulation of gene expression, and splicing and was previously associated with major developmental reprogramming in plants, such as vernalization and transition to flowering. Here, we show that DNA methylation also controls the growth processes of cell division and cell expansion within a growing organ. The maize (Zea mays) leaf offers a great tool to study growth processes, as the cells progressively move through the spatial gradient encompassing the division zone, transition zone, elongation zone, and mature zone. Opposite to de novo DMTs, the maintenance DMTs were transcriptionally regulated throughout the growth zone of the maize leaf, concomitant with differential CCGG methylation levels in the four zones. Surprisingly, the majority of differentially methylated sequences mapped on or close to gene bodies and not to repeat-rich loci. Moreover, especially the 5' and 3' regions of genes, which show overall low methylation levels, underwent differential methylation in a developmental context. Genes involved in processes such as chromatin remodeling, cell cycle progression, and growth regulation, were differentially methylated. The presence of differential methylation located upstream of the gene anticorrelated with transcript expression, while gene body differential methylation was unrelated to the expression level. These data indicate that DNA methylation is correlated with the decision to exit mitotic cell division and to enter cell expansion, which adds a new epigenetic level to the regulation of growth processes.

  1. Control of Transcriptional Elongation

    PubMed Central

    Kwak, Hojoong; Lis, John T.

    2014-01-01

    Elongation is becoming increasingly recognized as a critically controlled step in transcriptional regulation. While traditional genetic and biochemical studies have identified major players of transcriptional elongation, our understanding of the importance and roles of these factors is evolving rapidly through the recent advances in genome-wide and single-molecule technologies. Here we focus on how elongation can modulate the transcriptional outcome through the rate-liming step of RNA polymerase II pausing near promoters, and how the participating factors were identified. Among the factors we describe are NELF and DSIF, the pausing factors, and P-TEFb, the key player in pause release. We also describe non-exclusive models for how pausing is achieved by making use of high resolution genome-wide mapping of paused Pol II relative to promoter elements and the first nucleosome. We also discuss Pol II elongation through the bodies of genes and the roles of FACT and Spt6, the factors that allow Pol II to move through nucleosomes. PMID:24050178

  2. Elongate Hemlock Scale

    Treesearch

    Mark McClure

    2002-01-01

    The elongate hemlock scale, Fiorinia externa Ferris, native to Japan, is a pest of eastern hemlock, Tsuga canadensis, and Carolina hemlock, T. caroliniana, in the Eastern United States. It has been found in the District of Columbia and in nine states from Virginia to southern New England and west to Ohio. F. externa attacks the lower surface of the hemlock needle,...

  3. Plant Elongator regulates auxin-related genes during RNA polymerase II transcription elongation.

    PubMed

    Nelissen, Hilde; De Groeve, Steven; Fleury, Delphine; Neyt, Pia; Bruno, Leonardo; Bitonti, Maria Beatrice; Vandenbussche, Filip; Van der Straeten, Dominique; Yamaguchi, Takahiro; Tsukaya, Hirokazu; Witters, Erwin; De Jaeger, Geert; Houben, Andreas; Van Lijsebettens, Mieke

    2010-01-26

    In eukaryotes, transcription of protein-encoding genes is strongly regulated by posttranslational modifications of histones that affect the accessibility of the DNA by RNA polymerase II (RNAPII). The Elongator complex was originally identified in yeast as a histone acetyltransferase (HAT) complex that activates RNAPII-mediated transcription. In Arabidopsis thaliana, the Elongator mutants elo1, elo2, and elo3 with decreased leaf and primary root growth due to reduced cell proliferation identified homologs of components of the yeast Elongator complex, Elp4, Elp1, and Elp3, respectively. Here we show that the Elongator complex was purified from plant cell cultures as a six-component complex. The role of plant Elongator in transcription elongation was supported by colocalization of the HAT enzyme, ELO3, with euchromatin and the phosphorylated form of RNAPII, and reduced histone H3 lysine 14 acetylation at the coding region of the SHORT HYPOCOTYL 2 auxin repressor and the LAX2 auxin influx carrier gene with reduced expression levels in the elo3 mutant. Additional auxin-related genes were down-regulated in the transcriptome of elo mutants but not targeted by the Elongator HAT activity showing specificity in target gene selection. Biological relevance was apparent by auxin-related phenotypes and marker gene analysis. Ethylene and jasmonic acid signaling and abiotic stress responses were up-regulated in the elo transcriptome and might contribute to the pleiotropic elo phenotype. Thus, although the structure of Elongator and its substrate are conserved, target gene selection has diverged, showing that auxin signaling and influx are under chromatin control.

  4. Root Apex Transition Zone As Oscillatory Zone

    PubMed Central

    Baluška, František; Mancuso, Stefano

    2013-01-01

    Root apex of higher plants shows very high sensitivity to environmental stimuli. The root cap acts as the most prominent plant sensory organ; sensing diverse physical parameters such as gravity, light, humidity, oxygen, and critical inorganic nutrients. However, the motoric responses to these stimuli are accomplished in the elongation region. This spatial discrepancy was solved when we have discovered and characterized the transition zone which is interpolated between the apical meristem and the subapical elongation zone. Cells of this zone are very active in the cytoskeletal rearrangements, endocytosis and endocytic vesicle recycling, as well as in electric activities. Here we discuss the oscillatory nature of the transition zone which, together with several other features of this zone, suggest that it acts as some kind of command center. In accordance with the early proposal of Charles and Francis Darwin, cells of this root zone receive sensory information from the root cap and instruct the motoric responses of cells in the elongation zone. PMID:24106493

  5. Regulation of Transcript Elongation

    PubMed Central

    Belogurov, Georgiy A.; Artsimovitch, Irina

    2015-01-01

    Bacteria lack subcellular compartments and harbor a single RNA polymerase that synthesizes both structural and protein-coding RNAs, which are cotranscriptionally processed by distinct pathways. Nascent rRNAs fold into elaborate secondary structures and associate with ribosomal proteins, whereas nascent mRNAs are translated by ribosomes. During elongation, nucleic acid signals and regulatory proteins modulate concurrent RNA-processing events, instruct RNA polymerase where to pause and terminate transcription, or act as roadblocks to the moving enzyme. Communications among complexes that carry out transcription, translation, repair, and other cellular processes ensure timely execution of the gene expression program and survival under conditions of stress. This network is maintained by auxiliary proteins that act as bridges between RNA polymerase, ribosome, and repair enzymes, blurring boundaries between separate information-processing steps and making assignments of unique regulatory functions meaningless. Understanding the regulation of transcript elongation thus requires genome-wide approaches, which confirm known and reveal new regulatory connections. PMID:26132790

  6. Elongation of Flare Ribbons

    NASA Astrophysics Data System (ADS)

    Qiu, Jiong; Longcope, Dana W.; Cassak, Paul A.; Priest, Eric R.

    2017-03-01

    We present an analysis of the apparent elongation motion of flare ribbons along the polarity inversion line (PIL), as well as the shear of flare loops in several two-ribbon flares. Flare ribbons and loops spread along the PIL at a speed ranging from a few to a hundred km s‑1. The shear measured from conjugate footpoints is consistent with the measurement from flare loops, and both show the decrease of shear toward a potential field as a flare evolves and ribbons and loops spread along the PIL. Flares exhibiting fast bidirectional elongation appear to have a strong shear, which may indicate a large magnetic guide field relative to the reconnection field in the coronal current sheet. We discuss how the analysis of ribbon motion could help infer properties in the corona where reconnection takes place.

  7. Optic Nerve Elongation

    PubMed Central

    Alvi, Aijaz; Janecka, Ivo P.; Kapadia, Silloo; Johnson, Bruce L.; McVay, William

    1996-01-01

    The length of the optic nerves is a reflection of normal postnatal cranio-orbital development. Unilateral elongation of an optic nerve has been observed in two patients with orbital and skull base neoplasms. In the first case as compared to the patient's opposite, normal optic nerve, an elongated length of the involved optic nerve of 45 mm was present. The involved optic nerve in the second patient was 10 mm longer than the normal opposite optic nerve. The visual and extraocular function was preserved in the second patient. The first patient had only light perception in the affected eye. In this paper, the embryology, anatomy, and physiology of the optic nerve and its mechanisms of stretch and repair are discussed. ImagesFigure 1Figure 2Figure 3Figure 4Figure 5Figure 6Figure 7Figure 8Figure 9Figure 10Figure 11Figure 13 PMID:17170975

  8. Intense natural selection preceded the invasion of new adaptive zones during the radiation of New World leaf-nosed bats.

    PubMed

    Rossoni, Daniela M; Assis, Ana Paula A; Giannini, Norberto P; Marroig, Gabriel

    2017-09-11

    The family Phyllostomidae, which evolved in the New World during the last 30 million years, represents one of the largest and most morphologically diverse mammal families. Due to its uniquely diverse functional morphology, the phyllostomid skull is presumed to have evolved under strong directional selection; however, quantitative estimation of the strength of selection in this extraordinary lineage has not been reported. Here, we used comparative quantitative genetics approaches to elucidate the processes that drove cranial evolution in phyllostomids. We also quantified the strength of selection and explored its association with dietary transitions and specialization along the phyllostomid phylogeny. Our results suggest that natural selection was the evolutionary process responsible for cranial diversification in phyllostomid bats. Remarkably, the strongest selection in the phyllostomid phylogeny was associated with dietary specialization and the origination of novel feeding habits, suggesting that the adaptive diversification of phyllostomid bats was triggered by ecological opportunities. These findings are consistent with Simpson's quantum evolutionary model of transitions between adaptive zones. The multivariate analyses used in this study provides a powerful tool for understanding the role of evolutionary processes in shaping phenotypic diversity in any group on both micro- and macroevolutionary scales.

  9. KNOX overexpression in transgenic Kohleria (Gesneriaceae) prolongs the activity of proximal leaf blastozones and drastically alters segment fate.

    PubMed

    Barth, Sina; Geier, Thomas; Eimert, Klaus; Watillon, Bernard; Sangwan, Rajbir S; Gleissberg, Stefan

    2009-11-01

    KNOX (knotted1-like homeobox) genes have a widely conserved role in the generation of dissected leaves. Ectopic KNOX activity in leaves in various angiosperm lineages causes leaf form changes that can elucidate how the configuration of leaf development evolved. We present an analysis of leaf morphology and morphogenesis in transgenic Kohleria lines overexpressing a heterologous KNOX gene. Kohleria, like many members of Gesneriaceae, has simple-serrated leaves with pinnate venation. KNOX overexpression causes prolonged segment proliferation in proximal, but not distal, parts of leaf blades. Elaborate dissected segments reiterate the zonation of the whole leaf, with organogenic activity persisting between a distal maturation zone and a proximal intercalary elongation zone. The architecture of vascular bundles is severely altered, with a reduced midvein and a more palmate venation. The initial establishment of organogenically competent primordial margins (marginal blastozones) and the onset of tissue differentiation in early stages of leaf development were similar in wild-type and KNOX overexpressing lines. However, leaves overexpressing KNOX often failed to fully mature, and persistent marginal blastozones were found at the base of blades in mature portions of the shoot. We conclude that KNOX-mediated perpetuation of marginal blastozones in Kohleria is sufficient to induce a set of processes that result in highly dissected leaflets, which are unusual in this plant family. Spatial confinement of blastozones between an early maturing tip and a late elongating petiole zone reflects the presence of distinct maturation processes that limit the ability of the leaf margins to respond to ectopic KNOX gene expression.

  10. [Regulation of bacterial transcription elongation].

    PubMed

    Proshkin, S A; Mironov, A S

    2011-01-01

    The elongation complex, which involves RNA polymerase, DNA template and nascent RNA, is a central intermediate in transcription cycle. It is elongation complex that represents the main target for the action of different regulatory factors. Over the past several years, many structural and biochemical data have been obtained that shed light upon the molecular details of RNA polymerase function. Cooperation between RNA polymerase elongation complex and translating ribosome was established recently. Here we discuss the mechanisms of the regulation of bacterial transcription elongation.

  11. Elongated Microcapsules and Their Formation

    NASA Technical Reports Server (NTRS)

    Calle, Luz M. (Inventor); Li, Wenyan N. (Inventor); Buhrow, Jerry W. (Inventor); Perusich, Stephen A. (Inventor); Jolley, Scott T. (Inventor); Gibson, Tracy L. (Inventor); Williams, Martha K. (Inventor)

    2015-01-01

    Elongated microcapsules, such as elongated hydrophobic-core and hydrophilic-core microcapsules, may be formed by pulse stirring an emulsion or shearing an emulsion between two surfaces moving at different velocities. The elongated microcapsules may be dispersed in a coating formulation, such as paint.

  12. Gibberellin biosynthesis and signal transduction is essential for internode elongation in deepwater rice

    PubMed Central

    Ayano, Madoka; Kani, Takahiro; Kojima, Mikiko; Sakakibara, Hitoshi; Kitaoka, Takuya; Kuroha, Takeshi; Angeles-Shim, Rosalyn B; Kitano, Hidemi; Nagai, Keisuke; Ashikari, Motoyuki

    2014-01-01

    Under flooded conditions, the leaves and internodes of deepwater rice can elongate above the water surface to capture oxygen and prevent drowning. Our previous studies showed that three major quantitative trait loci (QTL) regulate deepwater-dependent internode elongation in deepwater rice. In this study, we investigated the age-dependent internode elongation in deepwater rice. We also investigated the relationship between deepwater-dependent internode elongation and the phytohormone gibberellin (GA) by physiological and genetic approach using a QTL pyramiding line (NIL-1 + 3 + 12). Deepwater rice did not show internode elongation before the sixth leaf stage under deepwater condition. Additionally, deepwater-dependent internode elongation occurred on the sixth and seventh internodes during the sixth leaf stage. These results indicate that deepwater rice could not start internode elongation until the sixth leaf stage. Ultra-performance liquid chromatography tandem mass-spectrometry (UPLC-MS/MS) method for the phytohormone contents showed a deepwater-dependent GA1 and GA4 accumulation in deepwater rice. Additionally, a GA inhibitor abolished deepwater-dependent internode elongation in deepwater rice. On the contrary, GA feeding mimicked internode elongation under ordinary growth conditions. However, mutations in GA biosynthesis and signal transduction genes blocked deepwater-dependent internode elongation. These data suggested that GA biosynthesis and signal transduction are essential for deepwater-dependent internode elongation in deepwater rice. Deepwater rice obtained the ability for rapid internode elongation to avoid drowning and adapt to flooded condition. How does it regulate internode elongation? Using both physiological and genetic approach, this paper shows that the plant hormone, gibberellin (GA) regulates internode elongation. PMID:24891164

  13. Regulation of Compound Leaf Development by PHANTASTICA in Medicago truncatula1[C][W][OPEN

    PubMed Central

    Ge, Liangfa; Peng, Jianling; Berbel, Ana; Madueño, Francisco; Chen, Rujin

    2014-01-01

    Plant leaves, simple or compound, initiate as peg-like structures from the peripheral zone of the shoot apical meristem, which requires class I KNOTTED-LIKE HOMEOBOXI (KNOXI) transcription factors to maintain its activity. The MYB domain protein encoded by the ASYMMETRIC LEAVES1/ROUGH SHEATH2/PHANTASTICA (ARP) gene, together with other factors, excludes KNOXI gene expression from incipient leaf primordia to initiate leaves and specify leaf adaxial identity. However, the regulatory relationship between ARP and KNOXI is more complex in compound-leafed species. Here, we investigated the role of ARP and KNOXI genes in compound leaf development in Medicago truncatula. We show that the M. truncatula phantastica mutant exhibited severe compound leaf defects, including curling and deep serration of leaf margins, shortened petioles, increased rachises, petioles acquiring motor organ characteristics, and ectopic development of petiolules. On the other hand, the M. truncatula brevipedicellus mutant did not exhibit visible compound leaf defects. Our analyses show that the altered petiole development requires ectopic expression of ELONGATED PETIOLULE1, which encodes a lateral organ boundary domain protein, and that the distal margin serration requires the auxin efflux protein M. truncatula PIN-FORMED10 in the M. truncatula phantastica mutant. PMID:24218492

  14. Structural basis of transcription elongation.

    PubMed

    Martinez-Rucobo, Fuensanta W; Cramer, Patrick

    2013-01-01

    For transcription elongation, all cellular RNA polymerases form a stable elongation complex (EC) with the DNA template and the RNA transcript. Since the millennium, a wealth of structural information and complementary functional studies provided a detailed three-dimensional picture of the EC and many of its functional states. Here we summarize these studies that elucidated EC structure and maintenance, nucleotide selection and addition, translocation, elongation inhibition, pausing and proofreading, backtracking, arrest and reactivation, processivity, DNA lesion-induced stalling, lesion bypass, and transcriptional mutagenesis. In the future, additional structural and functional studies of elongation factors that control the EC and their possible allosteric modes of action should result in a more complete understanding of the dynamic molecular mechanisms underlying transcription elongation. This article is part of a Special Issue entitled: RNA polymerase II Transcript Elongation. Copyright © 2012 Elsevier B.V. All rights reserved.

  15. Root cooling strongly affects diel leaf growth dynamics, water and carbohydrate relations in Ricinus communis.

    PubMed

    Poiré, Richard; Schneider, Heike; Thorpe, Michael R; Kuhn, Arnd J; Schurr, Ulrich; Walter, Achim

    2010-03-01

    In laboratory and greenhouse experiments with potted plants, shoots and roots are exposed to temperature regimes throughout a 24 h (diel) cycle that can differ strongly from the regime under which these plants have evolved. In the field, roots are often exposed to lower temperatures than shoots. When the root-zone temperature in Ricinus communis was decreased below a threshold value, leaf growth occurred preferentially at night and was strongly inhibited during the day. Overall, leaf expansion, shoot biomass growth, root elongation and ramification decreased rapidly, carbon fluxes from shoot to root were diminished and carbohydrate contents of both root and shoot increased. Further, transpiration rate was not affected, yet hydrostatic tensions in shoot xylem increased. When root temperature was increased again, xylem tension reduced, leaf growth recovered rapidly, carbon fluxes from shoot to root increased, and carbohydrate pools were depleted. We hypothesize that the decreased uptake of water in cool roots diminishes the growth potential of the entire plant - especially diurnally, when the growing leaf loses water via transpiration. As a consequence, leaf growth and metabolite concentrations can vary enormously, depending on root-zone temperature and its heterogeneity inside pots.

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

    NASA Technical Reports Server (NTRS)

    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.

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

    NASA Technical Reports Server (NTRS)

    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.

  18. Nitrogen stress affects the turnover and size of nitrogen pools supplying leaf growth in a grass.

    PubMed

    Lehmeier, Christoph Andreas; Wild, Melanie; Schnyder, Hans

    2013-08-01

    The effect of nitrogen (N) stress on the pool system supplying currently assimilated and (re)mobilized N for leaf growth of a grass was explored by dynamic ¹⁵N labeling, assessment of total and labeled N import into leaf growth zones, and compartmental analysis of the label import data. Perennial ryegrass (Lolium perenne) plants, grown with low or high levels of N fertilization, were labeled with ¹⁵NO₃⁻/¹⁴NO₃⁻ from 2 h to more than 20 d. In both treatments, the tracer time course in N imported into the growth zones fitted a two-pool model (r² > 0.99). This consisted of a "substrate pool," which received N from current uptake and supplied the growth zone, and a recycling/mobilizing "store," which exchanged with the substrate pool. N deficiency halved the leaf elongation rate, decreased N import into the growth zone, lengthened the delay between tracer uptake and its arrival in the growth zone (2.2 h versus 0.9 h), slowed the turnover of the substrate pool (half-life of 3.2 h versus 0.6 h), and increased its size (12.4 μg versus 5.9 μg). The store contained the equivalent of approximately 10 times (low N) and approximately five times (high N) the total daily N import into the growth zone. Its turnover agreed with that of protein turnover. Remarkably, the relative contribution of mobilization to leaf growth was large and similar (approximately 45%) in both treatments. We conclude that turnover and size of the substrate pool are related to the sink strength of the growth zone, whereas the contribution of the store is influenced by partitioning between sinks.

  19. Structural insights into Elongator function.

    PubMed

    Glatt, Sebastian; Müller, Christoph W

    2013-04-01

    The eukaryotic Elongator complex was initially identified in yeast as a RNA polymerase II (Pol II) associated transcription elongation factor, although there is accumulating evidence that its main cellular function is the specific modification of uridines at the wobble base position of tRNAs. Elongator complex is built up by six highly conserved subunits and was shown to be involved in a variety of different cellular activities. Here, we summarize structural and functional information on individual Elongator subunits or subcomplexes. On the basis of homology models of the Elp1, Elp2 and Elp3 subunits and the crystal structure of the Elp456 subcomplex, the role of each subunit in Elongator complex assembly and catalytic activity is discussed. Copyright © 2013 Elsevier Ltd. All rights reserved.

  20. Differential Methylation during Maize Leaf Growth Targets Developmentally Regulated Genes1[C][W][OPEN

    PubMed Central

    Candaele, Jasper; Demuynck, Kirin; Mosoti, Douglas; Beemster, Gerrit T.S.; Inzé, Dirk; Nelissen, Hilde

    2014-01-01

    DNA methylation is an important and widespread epigenetic modification in plant genomes, mediated by DNA methyltransferases (DMTs). DNA methylation is known to play a role in genome protection, regulation of gene expression, and splicing and was previously associated with major developmental reprogramming in plants, such as vernalization and transition to flowering. Here, we show that DNA methylation also controls the growth processes of cell division and cell expansion within a growing organ. The maize (Zea mays) leaf offers a great tool to study growth processes, as the cells progressively move through the spatial gradient encompassing the division zone, transition zone, elongation zone, and mature zone. Opposite to de novo DMTs, the maintenance DMTs were transcriptionally regulated throughout the growth zone of the maize leaf, concomitant with differential CCGG methylation levels in the four zones. Surprisingly, the majority of differentially methylated sequences mapped on or close to gene bodies and not to repeat-rich loci. Moreover, especially the 5′ and 3′ regions of genes, which show overall low methylation levels, underwent differential methylation in a developmental context. Genes involved in processes such as chromatin remodeling, cell cycle progression, and growth regulation, were differentially methylated. The presence of differential methylation located upstream of the gene anticorrelated with transcript expression, while gene body differential methylation was unrelated to the expression level. These data indicate that DNA methylation is correlated with the decision to exit mitotic cell division and to enter cell expansion, which adds a new epigenetic level to the regulation of growth processes. PMID:24488968

  1. Thermodynamic Model of Transcription Elongation

    NASA Astrophysics Data System (ADS)

    Tadigotla, Vasisht; O'Maoileidigh, Daibhid; Sengupta, Anirvan; Epshtein, Vitaly; Ebright, Richard; Nudler, Evgeny; Ruckenstein, Andrei

    2006-03-01

    We present a statistical mechanics approach to the prediction of backtracked pauses in prokaryotic transcription elongation derived from structural models of the transcription elongation complex (TEC). Our algorithm is based on the thermodynamic stability of TEC along the DNA template calculated from the sequence dependent free-energy of DNA-DNA, DNA-RNA and RNA-RNA base pairing associated with (a) the translocation and size fluctuations of the transcription bubble; (b) the changes in the DNA-RNA hybrid; and (c) the changes in the RNA folding free-energy. The calculations involve no adjustable parameters apart from a cutoff used to discriminate paused from non-paused complexes. When applied to 100 experimental pauses in transcription elongation by E. coli RNA polymerase on ten DNA templates the approach produces highly statistically significant results. Transcription elongation is an inherently kinetic process and a simplified kinetic model with the same predictive power is presented separately.

  2. The δ(18) O and δ(2) H of water in the leaf growth-and-differentiation zone of grasses is close to source water in both humid and dry atmospheres.

    PubMed

    Liu, Hai Tao; Schäufele, Rudi; Gong, Xiao Ying; Schnyder, Hans

    2017-04-03

    The oxygen and hydrogen isotope composition of water in the leaf growth-and-differentiation zone, LGDZ, (δ(18) OLGDZ , δ(2) HLGDZ ) of grasses influences the isotopic composition of leaf cellulose (oxygen) and wax (hydrogen) - important for understanding (paleo)environmental and physiological information contained in these biological archives - but is presently unknown. This work determined δ(18) OLGDZ and δ(2) HLGDZ , (18) O- and (2) H-enrichment of LGDZ (∆(18) OLGDZ and ∆(2) HLGDZ ), and the (18) O- and (2) H-enrichment of leaf blade water (∆(18) OLW, ∆(2) HLW ) in two C3 and three C4 grasses grown at high and low vapor pressure deficit (VPD). The proportion of unenriched water (px ) in the LGDZ ranged from 0.9 to 1.0 for (18) O and 1.0 to 1.2 for (2) H. VPD had no effect on the proportion of (18) O- and (2) H-enriched water in the LGDZ, and species effects were small or nonsignificant. Deuterium discrimination caused depletion of (2) H in LGDZ water, increasing (apparent) px -values > 1.0 in some cases. The isotopic composition of water in the LGDZ was close to that of source water, independent of VPD and much less enriched than previously supposed, but similar to reported xylem water in trees. The well-constrained px will be useful in future investigations of oxygen and hydrogen isotopic fractionation during cellulose and wax synthesis, respectively.

  3. Controlled laser production of elongated articles from particulates

    DOEpatents

    Dixon, Raymond D.; Lewis, Gary K.; Milewski, John O.

    2002-01-01

    It has been discovered that wires and small diameter rods can be produced using laser deposition technology in a novel way. An elongated article such as a wire or rod is constructed by melting and depositing particulate material into a deposition zone which has been designed to yield the desired article shape and dimensions. The article is withdrawn from the deposition zone as it is formed, thus enabling formation of the article in a continuous process. Alternatively, the deposition zone is moved along any of numerous deposition paths away from the article being formed.

  4. Vegetative growth and cluster development in Shiraz grapevines subjected to partial root-zone cooling.

    PubMed

    Rogiers, Suzy Y; Clarke, Simon J

    2013-01-01

    Heterogeneity in root-zone temperature both vertically and horizontally may contribute to the uneven vegetative and reproductive growth often observed across vineyards. An experiment was designed to assess whether the warmed half of a grapevine root zone could compensate for the cooled half in terms of vegetative growth and reproductive development. We divided the root system of potted Shiraz grapevines bilaterally and applied either a cool or a warm treatment to each half from budburst to fruit set. Shoot growth and inflorescence development were monitored over the season. Simultaneous cooling and warming of parts of the root system decreased shoot elongation, leaf emergence and leaf expansion below that of plants with a fully warmed root zone, but not to the same extent as those with a fully cooled root zone. Inflorescence rachis length, flower number and berry number after fertilization were smaller only in those vines exposed to fully cooled root zones. After terminating the treatments, berry enlargement and the onset of veraison were slowed in those vines that had been exposed to complete or partial root-zone cooling. Grapevines exposed to partial root-zone cooling were thus delayed in vegetative and reproductive development, but the inhibition was greater in those plants whose entire root system had been cooled.

  5. Vegetative growth and cluster development in Shiraz grapevines subjected to partial root-zone cooling

    PubMed Central

    Rogiers, Suzy Y.; Clarke, Simon J.

    2013-01-01

    Heterogeneity in root-zone temperature both vertically and horizontally may contribute to the uneven vegetative and reproductive growth often observed across vineyards. An experiment was designed to assess whether the warmed half of a grapevine root zone could compensate for the cooled half in terms of vegetative growth and reproductive development. We divided the root system of potted Shiraz grapevines bilaterally and applied either a cool or a warm treatment to each half from budburst to fruit set. Shoot growth and inflorescence development were monitored over the season. Simultaneous cooling and warming of parts of the root system decreased shoot elongation, leaf emergence and leaf expansion below that of plants with a fully warmed root zone, but not to the same extent as those with a fully cooled root zone. Inflorescence rachis length, flower number and berry number after fertilization were smaller only in those vines exposed to fully cooled root zones. After terminating the treatments, berry enlargement and the onset of veraison were slowed in those vines that had been exposed to complete or partial root-zone cooling. Grapevines exposed to partial root-zone cooling were thus delayed in vegetative and reproductive development, but the inhibition was greater in those plants whose entire root system had been cooled. PMID:24244839

  6. Aortoiliac elongation after endovascular aortic aneurysm repair.

    PubMed

    Chandra, Venita; Rouer, Martin; Garg, Trit; Fleischmann, Dominik; Mell, Matthew

    2015-07-01

    differences in proximal landing zone, significant differences in aortic lengthening over time were observed by device type (P = 0.02). Significant aortoiliac elongation was observed after EVAR. Such morphologic changes may impact long-term durability of EVAR, warranting further investigation into factors associated with these morphologic changes. Copyright © 2015 Elsevier Inc. All rights reserved.

  7. Biophysical constraints on leaf expansion in a tall conifer.

    Treesearch

    Fredrick C. Meinzer; Barbara J. Bond; Jennifer A. Karanian

    2008-01-01

    The physiological mechanisms responsible for reduced extension growth as trees increase in height remain elusive. We evaluated biophysical constraints on leaf expansion in old-growth Douglas-fir (Psuedotsuga menziesii (Mirb.) Franco) trees. Needle elongation rates, plastic and elastic extensibility, bulk leaf water, (L...

  8. Leaf Activities.

    ERIC Educational Resources Information Center

    Mingie, Walter

    Leaf activities can provide a means of using basic concepts of outdoor education to learn in elementary level subject areas. Equipment needed includes leaves, a clipboard with paper, and a pencil. A bag of leaves may be brought into the classroom if weather conditions or time do not permit going outdoors. Each student should pick a leaf, examine…

  9. Leaf physiognomy and climate: A multivariate analysis

    NASA Astrophysics Data System (ADS)

    Davis, J. M.; Taylor, S. E.

    1980-11-01

    Research has demonstrated that leaf physiognomy is representative of the local or microclimate conditions under which plants grow. The physiognomy of leaf samples from Oregon, Michigan, Missouri, Tennessee, and the Panama Canal Zone has been related to the microclimate using Walter diagrams and Thornthwaite water-budget data. A technique to aid paleoclimatologists in identifying the nature of the microclimate from leaf physiognomy utilizes statistical procedures to classify leaf samples into one of six microclimate regimes based on leaf physiognomy information available from fossilized samples.

  10. A kinetic analysis of hyponastic growth and petiole elongation upon ethylene exposure in Rumex palustris

    PubMed Central

    Heydarian, Zohreh; Sasidharan, Rashmi; Cox, Marjolein C. H.; Pierik, Ronald; Voesenek, Laurentius A. C. J.; Peeters, Anton J. M.

    2010-01-01

    Background and Aims Complete submergence is an important stress factor for many terrestrial plants, and a limited number of species have evolved mechanisms to deal with these conditions. Rumex palustris is one such species and manages to outgrow the water, and thus restore contact with the atmosphere, through upward leaf growth (hyponasty) followed by strongly enhanced petiole elongation. These responses are initiated by the gaseous plant hormone ethylene, which accumulates inside plants due to physical entrapment. This study aimed to investigate the kinetics of ethylene-induced leaf hyponasty and petiole elongation. Methods Leaf hyponasty and petiole elongation was studied using a computerized digital camera set-up followed by image analyses. Linear variable displacement transducers were used for fine resolution monitoring and measurement of petiole growth rates. Key Results We show that submergence-induced hyponastic growth and petiole elongation in R. palustris can be mimicked by exposing plants to ethylene. The petiole elongation response to ethylene is shown to depend on the initial angle of the petiole. When petiole angles were artificially kept at 0°, rather than the natural angle of 35°, ethylene could not induce enhanced petiole elongation. This is very similar to submergence studies and confirms the idea that there are endogenous, angle-dependent signals that influence the petiole elongation response to ethylene. Conclusions Our data suggest that submergence and ethylene-induced hyponastic growth and enhanced petiole elongation responses in R. palustris are largely similar. However, there are some differences that may relate to the complexity of the submergence treatment as compared with an ethylene treatment. PMID:20603244

  11. A kinetic analysis of hyponastic growth and petiole elongation upon ethylene exposure in Rumex palustris.

    PubMed

    Heydarian, Zohreh; Sasidharan, Rashmi; Cox, Marjolein C H; Pierik, Ronald; Voesenek, Laurentius A C J; Peeters, Anton J M

    2010-09-01

    Complete submergence is an important stress factor for many terrestrial plants, and a limited number of species have evolved mechanisms to deal with these conditions. Rumex palustris is one such species and manages to outgrow the water, and thus restore contact with the atmosphere, through upward leaf growth (hyponasty) followed by strongly enhanced petiole elongation. These responses are initiated by the gaseous plant hormone ethylene, which accumulates inside plants due to physical entrapment. This study aimed to investigate the kinetics of ethylene-induced leaf hyponasty and petiole elongation. Leaf hyponasty and petiole elongation was studied using a computerized digital camera set-up followed by image analyses. Linear variable displacement transducers were used for fine resolution monitoring and measurement of petiole growth rates. We show that submergence-induced hyponastic growth and petiole elongation in R. palustris can be mimicked by exposing plants to ethylene. The petiole elongation response to ethylene is shown to depend on the initial angle of the petiole. When petiole angles were artificially kept at 0 degrees, rather than the natural angle of 35 degrees, ethylene could not induce enhanced petiole elongation. This is very similar to submergence studies and confirms the idea that there are endogenous, angle-dependent signals that influence the petiole elongation response to ethylene. Our data suggest that submergence and ethylene-induced hyponastic growth and enhanced petiole elongation responses in R. palustris are largely similar. However, there are some differences that may relate to the complexity of the submergence treatment as compared with an ethylene treatment.

  12. Hack's Law: Sinuosity, convexity, elongation

    NASA Astrophysics Data System (ADS)

    Willemin, James H.

    2000-11-01

    Hack's law, an empirical, power law relationship between drainage basin area and the length of the main stream channel, has long been taken to imply that drainage basins become more elongate (relatively longer and narrower) with increasing basin size. A study of the geometry of 38 basins from three distinct geomorphic settings shows that this geometric interpretation of Hack's law is only occasionally true: Even though Hack's power law relationship holds between basin area and main channel length, these basins do not necessarily become more elongate with increasing size. Rather, Hack's law is an expression of a balance between changes in basin shape and changes in channel planform geometry. For the basins in this study, changes in channel sinuosity play the most important role in this balance; changes in basin shape are far less regular. Local conditions appear to determine the partitioning of importance between changes in basin shape and channel sinuosity.

  13. Elongation Transducer For Tensile Tests

    NASA Technical Reports Server (NTRS)

    Roberts, Paul W.; Stokes, Thomas R.

    1994-01-01

    Extensometer transducer measures elongation of tensile-test specimen with negligible distortion of test results. Used in stress-versus-strain tests of small specimens of composite materials. Clamping stress distributed more evenly. Specimen clamped gently between jaw and facing surface of housing. Friction force of load points on conical tips onto specimen depends on compression of spring, adjusted by turning cover on housing. Limp, light nylon-insulated electrical leads impose minimal extraneous loads on measuring elements.

  14. Effects of elevated CO₂ and temperature on photosynthesis and leaf traits of an understory dwarf bamboo in subalpine forest zone, China.

    PubMed

    Li, Yongping; Zhang, Yuanbin; Zhang, Xiaolu; Korpelainen, Helena; Berninger, Frank; Li, Chunyang

    2013-06-01

    The dwarf bamboo (Fargesia rufa Yi), growing understory in subalpine dark coniferous forest, is one of the main foods for giant panda, and it influences the regeneration of subalpine coniferous forests in southwestern China. To investigate the effects of elevated CO₂, temperature and their combination, the dwarf bamboo plantlets were exposed to two CO₂ regimes (ambient and double ambient CO₂ concentration) and two temperatures (ambient and +2.2°C) in growth chambers. Gas exchange, leaf traits and carbohydrates concentration were measured after the 150-day experiment. Elevated CO₂ significantly increased the net photosynthetic rate (Anet ), intrinsic water-use efficiency (WUEi ) and carbon isotope composition (δ¹³C) and decreased stomatal conductance (g(s)) and total chlorophyll concentration based on mass (Chl(m)) and area (Chl(a)). On the other hand, elevated CO₂ decreased specific leaf area (SLA), which was increased by elevated temperature. Elevated CO₂ also increased foliar carbon concentration based on mass (C(m)) and area (C(a)), nitrogen concentration based on area (N(a)), carbohydrates concentration (i.e. sucrose, sugar, starch and non-structural carbohydrates) and the slope of the A(net)-N(a) relationship. However, elevated temperature decreased C(m), C(a) and N(a). The combination of elevated CO₂ and temperature hardly affected SLA, C(m), C(a), N(m), N(a), Chl(m) and Chl(a). Variables Anet and Na had positive linear relationships in all treatments. Our results showed that photosynthetic acclimation did not occur in dwarf bamboo at elevated CO₂ and it could adjust physiology and morphology to enable the capture of more light, to increase WUE and improve nutritional conditions.

  15. Limitation of Cell Elongation in Barley (Hordeum vulgare L.) Leaves Through Mechanical and Tissue-Hydraulic Properties.

    PubMed

    Touati, Mostefa; Knipfer, Thorsten; Visnovitz, Tamás; Kameli, Abdelkrim; Fricke, Wieland

    2015-07-01

    The aim of the present study was to assess the mechanical and hydraulic limitation of growth in leaf epidermal cells of barley (Hordeum vulgare L.) in response to agents which affect cellular water (mercuric chloride, HgCl(2)) and potassium (cesium chloride, CsCl; tetraethylammonium, TEA) transport, pump activity of plasma membrane H(+)-ATPase and wall acidification (fusicoccin, FC). Cell turgor (P) was measured with the cell pressure probe, and cell osmotic pressure (π) was analyzed through picoliter osmometry of single-cell extracts. A wall extensibility coefficient (M) and tissue hydraulic conductance coefficient (L) were derived using the Lockhart equation. There was a significant positive linear relationship between relative elemental growth rate and P, which fit all treatments, with an overall apparent yield threshold of 0.368 MPa. Differences in growth between treatments could be explained through differences in P. A comparison of L and M showed that growth in all except the FC treatment was co-limited through hydraulic and mechanical properties, though to various extents. This was accompanied by significant (0.17-0.24 MPa) differences in water potential (ΔΨ) between xylem and epidermal cells in the leaf elongation zone. In contrast, FC-treated leaves showed ΔΨ close to zero and a 10-fold increase in L.

  16. Elongation factors in protein synthesis.

    PubMed

    Kraal, B; Bosch, L; Mesters, J R; de Graaf, J M; Woudt, L P; Vijgenboom, E; Heinstra, P W; Zeef, L A; Boon, C

    1993-01-01

    Recent discoveries of elongation factor-related proteins have considerably complicated the simple textbook scheme of the peptide chain elongation cycle. During growth and differentiation the cycle may be regulated not only by factor modification but also factor replacement. In addition, rare tRNAs may have their own rare factor proteins. A special case is the acquisition of resistance by bacteria to elongation factor-directed antibiotics. Pertinent data from the literature and our own work with Escherichia coli and Streptomyces are discussed. The GTP-binding domain of EF-Tu has been studied extensively, but little molecular detail is available on the interactions with its other ligands or effectors, or on the way they are affected by the GTPase switch signal. A growing number of EF-Tu mutants obtained by ourselves and others are helping us in testing current ideas. We have found a synergistic effect between EF-Tu and EF-G in their uncoupled GTPase reactions on empty ribosomes. Only the EF-G reaction is perturbed by fluoroaluminates.

  17. Optimal architectures of elongated viruses

    PubMed Central

    Luque, Antoni; Zandi, Roya; Reguera, David

    2010-01-01

    Many viruses protect their genetic material by a closed elongated protein shell. Unlike spherical viruses, the structure of these prolates is not yet well understood, and only a few of them have been fully characterized. We present the results of a simple phenomenological model, which describes the remarkable structures of prolate or bacilliform viral shells. Surprisingly, we find that the special well-defined geometry of these elongated viruses arises just as a consequence of free-energy minimization of a generic interaction between the structural units of the capsid. Hemispherical T-number caps centered along the 5-, 3-, and 2-fold axes with hexagonally ordered cylindrical bodies are found to be local energy minima, thus justifying their occurrence as optimal viral structures. Moreover, closed elongated viruses show a sequence of magic numbers for the end-caps, leading to strict selection rules for the length and structure of the body as well as for the number of capsomers and proteins of the capsid. The model reproduces the architecture of spherical and bacilliform viruses, both in vivo and in vitro, and constitutes an important step towards understanding viral assembly and its potential control for biological and nanotechnological applications. PMID:20212146

  18. Venus - A Large Elongated Caldera 'Sacajawea Patera

    NASA Technical Reports Server (NTRS)

    1991-01-01

    This Magellan image reveals Sacajawea Patera, a large, elongate caldera located in Western Ishtar Terra on the smooth plateau of Lakshmi Planum. The image is centered at 64.5 degrees North latitude and 337 degrees East longitude. It is approximately 420 kilometers (252 miles) wide at the base. Sacajawea is a depression approximately 1-2 kilometers (0.6-1.2 miles) deep and 120 x 215 kilometers (74 x 133 miles) in diameter; it is elongate in a southwest-northeast direction. The depression is bounded by a zone of circumferential curvilinear structures interpreted to be graben and fault scarps. These structures are spaced 0.5-4 kilometers (0.3-2.5 miles) apart, are 0.6-4.0 kilometers (0.4-2.5 miles) in width and up to 100 kilometers (62 miles) in length. Extending up to approximately 140 kilometers (87 miles) in length from the southeast of the patera is a system of linear structures thought to represent a flanking rift zone along which the lateral injection and eruption of magma may have occurred. A shield edifice 12 kilometers (7 miles) in diameter with a prominent central pit lies along the trend of one of these features. The impact crater Zlata, approximately 6 kilometers (4 miles) in diameter is located within the zone of graben to the northwest of the patera. Few flow features are observed in association with Sacajawea, possibly due to age and state of degradation of the flows. Mottled bright deposits 4-20 kilometers (2.5-12 miles) in width are located near the periphery and in the center of the patera floor within local topographic lows. Diffuse patches of dark material approximately 40 kilometers (25 miles) in width are observed southwest of the patera, superposed on portions of the surrounding graben. The formation of Sacajawea is thought to be related to the drainage and collapse of a large magma chamber. Gravitational relaxation may have caused the resultant caldera to sag, producing the numerous faults and graben that circumscribe the patera. Regions of

  19. Nitrogen Stress Affects the Turnover and Size of Nitrogen Pools Supplying Leaf Growth in a Grass1[C][W][OPEN

    PubMed Central

    Lehmeier, Christoph Andreas; Wild, Melanie; Schnyder, Hans

    2013-01-01

    The effect of nitrogen (N) stress on the pool system supplying currently assimilated and (re)mobilized N for leaf growth of a grass was explored by dynamic 15N labeling, assessment of total and labeled N import into leaf growth zones, and compartmental analysis of the label import data. Perennial ryegrass (Lolium perenne) plants, grown with low or high levels of N fertilization, were labeled with 15NO3−/14NO3− from 2 h to more than 20 d. In both treatments, the tracer time course in N imported into the growth zones fitted a two-pool model (r2 > 0.99). This consisted of a “substrate pool,” which received N from current uptake and supplied the growth zone, and a recycling/mobilizing “store,” which exchanged with the substrate pool. N deficiency halved the leaf elongation rate, decreased N import into the growth zone, lengthened the delay between tracer uptake and its arrival in the growth zone (2.2 h versus 0.9 h), slowed the turnover of the substrate pool (half-life of 3.2 h versus 0.6 h), and increased its size (12.4 μg versus 5.9 μg). The store contained the equivalent of approximately 10 times (low N) and approximately five times (high N) the total daily N import into the growth zone. Its turnover agreed with that of protein turnover. Remarkably, the relative contribution of mobilization to leaf growth was large and similar (approximately 45%) in both treatments. We conclude that turnover and size of the substrate pool are related to the sink strength of the growth zone, whereas the contribution of the store is influenced by partitioning between sinks. PMID:23757403

  20. Project LEAF

    EPA Pesticide Factsheets

    Project LEAF has a goal of educating farmworkers about how to reduce pesticide exposure to their families from pesticide residues they may be inadvertently taking home on their clothing, etc. Find outreach materials.

  1. Intraspecific variation in the magnitude and pattern of flooding-induced shoot elongation in Rumex palustris

    PubMed Central

    Chen, Xin; Huber, Heidrun; de Kroon, Hans; Peeters, Anton J. M.; Poorter, Hendrik; Voesenek, Laurentius A. C. J.; Visser, Eric J. W.

    2009-01-01

    Background and Aims Intraspecific variation in flooding tolerance is the basic pre-condition for adaptive flooding tolerance to evolve, and flooding-induced shoot elongation is an important trait that enables plants to survive shallow, prolonged flooding. Here an investigation was conducted to determine to what extent variation in flooding-induced leaf elongation exists among and within populations of the wetland species Rumex palustris, and whether the magnitude of elongation can be linked to habitat characteristics. Methods Offspring of eight genotypes collected in each of 12 populations from different sites (ranging from river mudflats with dynamic flooding regimes to areas with stagnant water) were submerged, and petioles, laminas and roots were harvested separately to measure traits related to elongation and plant growth. Key Results We found strong elongation of petioles upon submergence, and both among- and within-population variation in this trait, not only in final length, but also in the timing of the elongation response. However, the variation in elongation responses could not be linked to habitat type. Conclusions Spatio-temporal variation in the duration and depth of flooding in combination with a presumably weak selection against flooding-induced elongation may have contributed to the maintenance of large genetic variation in flooding-related traits among and within populations. PMID:19687030

  2. Intraspecific variation in the magnitude and pattern of flooding-induced shoot elongation in Rumex palustris.

    PubMed

    Chen, Xin; Huber, Heidrun; de Kroon, Hans; Peeters, Anton J M; Poorter, Hendrik; Voesenek, Laurentius A C J; Visser, Eric J W

    2009-11-01

    Intraspecific variation in flooding tolerance is the basic pre-condition for adaptive flooding tolerance to evolve, and flooding-induced shoot elongation is an important trait that enables plants to survive shallow, prolonged flooding. Here an investigation was conducted to determine to what extent variation in flooding-induced leaf elongation exists among and within populations of the wetland species Rumex palustris, and whether the magnitude of elongation can be linked to habitat characteristics. Offspring of eight genotypes collected in each of 12 populations from different sites (ranging from river mudflats with dynamic flooding regimes to areas with stagnant water) were submerged, and petioles, laminas and roots were harvested separately to measure traits related to elongation and plant growth. We found strong elongation of petioles upon submergence, and both among- and within-population variation in this trait, not only in final length, but also in the timing of the elongation response. However, the variation in elongation responses could not be linked to habitat type. Spatio-temporal variation in the duration and depth of flooding in combination with a presumably weak selection against flooding-induced elongation may have contributed to the maintenance of large genetic variation in flooding-related traits among and within populations.

  3. Specialized zones of development in roots

    NASA Technical Reports Server (NTRS)

    Ishikawa, H.; Evans, M. L.

    1995-01-01

    The authors propose using the term "distal elongation zone" (DEZ) rather than "postmitotic isodiametric growth zone" to refer to the group of cells between the apical meristem and the elongation zone in plant roots. Reasons presented for the change are that the proposed DEZ includes many cells that are still dividing, most cells in the region are not isodiametric, and the pattern of cell expansion in this region varies with position in the region. Cells in the DEZ respond to gravistimulation, mechanical impedance, electrotropic stimulation, water stress, and auxin. Differences in gene expression patterns between DEZ cells and cells in the main elongation zone are noted.

  4. Specialized zones of development in roots

    NASA Technical Reports Server (NTRS)

    Ishikawa, H.; Evans, M. L.

    1995-01-01

    The authors propose using the term "distal elongation zone" (DEZ) rather than "postmitotic isodiametric growth zone" to refer to the group of cells between the apical meristem and the elongation zone in plant roots. Reasons presented for the change are that the proposed DEZ includes many cells that are still dividing, most cells in the region are not isodiametric, and the pattern of cell expansion in this region varies with position in the region. Cells in the DEZ respond to gravistimulation, mechanical impedance, electrotropic stimulation, water stress, and auxin. Differences in gene expression patterns between DEZ cells and cells in the main elongation zone are noted.

  5. Copper regulates primary root elongation through PIN1-mediated auxin redistribution.

    PubMed

    Yuan, Hong-Mei; Xu, Heng-Hao; Liu, Wen-Cheng; Lu, Ying-Tang

    2013-05-01

    The heavy metal copper (Cu) is an essential microelement required for normal plant growth and development, but it inhibits primary root growth when in excess. The mechanism underlying how excess Cu functions in this process remains to be further elucidated. Here, we report that a higher concentration of CuSO4 inhibited primary root elongation of Arabidopsis seedlings by affecting both the elongation and meristem zones. In the meristem zone, meristematic cell division potential was reduced by excess Cu. Further experiments showed that Cu can modulate auxin distribution, resulting in higher auxin activities in both the elongation and meristem zones of Cu-treated roots based on DR5::GUS expression patterns. This Cu-mediated auxin redistribution was shown to be responsible for Cu-mediated inhibition of primary root elongation. Additional genetic and physiological data demonstrated that it was PINFORMED1 (PIN1), but not PIN2 or AUXIN1 (AUX1), that regulated this process. However, Cu-induced hydrogen peroxide accumulation did not contribute to Cu-induced auxin redistribution for inhibition of root elongation. When the possible role of ethylene in this process was analyzed, Cu had a similar impact on the root elongation of both the wild type and the ein2-1 mutant, implying that Cu-mediated inhibition of primary root elongation was not due to the ethylene signaling pathway.

  6. Whole population cell analysis of a landmark-rich mammalian epithelium reveals multiple elongation mechanisms

    PubMed Central

    Economou, Andrew D.; Brock, Lara J.; Cobourne, Martyn T.; Green, Jeremy B. A.

    2013-01-01

    Tissue elongation is a fundamental component of developing and regenerating systems. Although localised proliferation is an important mechanism for tissue elongation, potentially important contributions of other elongation mechanisms, specifically cell shape change, orientated cell division and cell rearrangement, are rarely considered or quantified, particularly in mammalian systems. Their quantification, together with proliferation, provides a rigorous framework for the analysis of elongation. The mammalian palatal epithelium is a landmark-rich tissue, marked by regularly spaced ridges (rugae), making it an excellent model in which to analyse the contributions of cellular processes to directional tissue growth. We captured confocal stacks of entire fixed mouse palate epithelia throughout the mid-gestation growth period, labelled with membrane, nuclear and cell proliferation markers and segmented all cells (up to ∼20,000 per palate), allowing the quantification of cell shape and proliferation. Using the rugae as landmarks, these measures revealed that the so-called growth zone is a region of proliferation that is intermittently elevated at ruga initiation. The distribution of oriented cell division suggests that it is not a driver of tissue elongation, whereas cell shape analysis revealed that both elongation of cells leaving the growth zone and apico-basal cell rearrangements do contribute significantly to directional growth. Quantitative comparison of elongation processes indicated that proliferation contributes most to elongation at the growth zone, but cell shape change and rearrangement contribute as much as 40% of total elongation. We have demonstrated the utility of an approach to analysing the cellular mechanisms underlying tissue elongation in mammalian tissues. It should be broadly applied to higher-resolution analysis of links between genotypes and malformation phenotypes. PMID:24173805

  7. METHOD OF FORMING ELONGATED COMPACTS

    DOEpatents

    Larson, H.F.

    1959-05-01

    A powder compacting procedure and apparatus which produces elongated compacts of Be is described. The powdered metal is placed in a thin metal tube which is chemically compatible to lubricant, powder, atmosphere, and die material and will undergo a high degree of plastic deformation and have intermediate hardness. The tube is capped and placed in the die, and punches are applied to the ends. During the compacting stroke the powder seizes the tube and a thickening and shortening of the tube occurs. The tube is easily removed from the die, split, and peeled from the compact. (T.R.H.)

  8. Leaf Development

    PubMed Central

    2013-01-01

    Leaves are the most important organs for plants. Without leaves, plants cannot capture light energy or synthesize organic compounds via photosynthesis. Without leaves, plants would be unable perceive diverse environmental conditions, particularly those relating to light quality/quantity. Without leaves, plants would not be able to flower because all floral organs are modified leaves. Arabidopsis thaliana is a good model system for analyzing mechanisms of eudicotyledonous, simple-leaf development. The first section of this review provides a brief history of studies on development in Arabidopsis leaves. This history largely coincides with a general history of advancement in understanding of the genetic mechanisms operating during simple-leaf development in angiosperms. In the second section, I outline events in Arabidopsis leaf development, with emphasis on genetic controls. Current knowledge of six important components in these developmental events is summarized in detail, followed by concluding remarks and perspectives. PMID:23864837

  9. Plant Movement. Submergence-Induced Petiole Elongation in Rumex palustris Depends on Hyponastic Growth1

    PubMed Central

    Cox, Marjolein C.H.; Millenaar, Frank F.; van Berkel, Yvonne E.M. de Jong; Peeters, Anton J.M.; Voesenek, Laurentius A.C.J.

    2003-01-01

    The submergence-tolerant species Rumex palustris (Sm.) responds to complete submergence by an increase in petiole angle with the horizontal. This hyponastic growth, in combination with stimulated elongation of the petiole, can bring the leaf tips above the water surface, thus restoring gas exchange and enabling survival. Using a computerized digital camera set-up the kinetics of this hyponastic petiole movement and stimulated petiole elongation were studied. The hyponastic growth is a relatively rapid process that starts after a lag phase of 1.5 to 3 h and is completed after 6 to 7 h. The kinetics of hyponastic growth depend on the initial angle of the petiole at the time of submergence, a factor showing considerable seasonal variation. For example, lower petiole angles at the time of submergence result in a shorter lag phase for hyponastic growth. This dependency of the hyponastic growth kinetics can be mimicked by experimentally manipulating the petiole angle at the time of submergence. Stimulated petiole elongation in response to complete submergence also shows kinetics that are dependent on the petiole angle at the time of submergence, with lower initial petiole angles resulting in a longer lag phase for petiole elongation. Angle manipulation experiments show that stimulated petiole elongation can only start when the petiole has reached an angle of 40° to 50°. The petiole can reach this “critical angle” for stimulated petiole elongation by the process of hyponastic growth. This research shows a functional dependency of one response to submergence in R. palustris (stimulated petiole elongation) on another response (hyponastic petiole growth), because petiole elongation can only contribute to the leaf reaching the water surface when the petiole has a more or less upright position. PMID:12746533

  10. Locomotion in elongate fishes: A contact sport.

    PubMed

    Ward, Andrea B; Costa, Alyssa; Monroe, Stephanie L; Aluck, Robert J; Mehta, Rita S

    2015-10-01

    Despite the physical differences between water and air, a number of fish lineages are known to make terrestrial excursions on land. Many of these fishes exhibit an elongate body plan. Elongation of the body can occur in several ways, the most common of which is increasing the number of vertebrae in one or both regions of the axial skeleton--precaudal and/or caudal. Elongate species are often found in three-dimensionally complex habitats. It has been hypothesized that elongate fishes use this structure to their locomotor advantage. In this study, we consider how elongation and differences in vertebral regionalization correspond with the use of wooden pegs, which are provided as analogs to vertically oriented substrate, structures that protrude above the ground. We compare aquatic and terrestrial locomotor behaviors of Polypterus senegalus, Erpetoichthys calabaricus, and Gymnallabes typus as they move through a peg array. When considering axial elongation we find that the highly elongate species, E. calabaricus and G. typus, contact more pegs but on average move slower in both environments than P. senegalus. When considering axial regionalization, we find that the precaudally elongate species, P. senegalus and E. calabaricus, differ in the patterns of peg contact between the two environments whereas the caudally elongate species, G. typus, exhibits similar peg contact between the two environments. Our study highlights the importance of incorporating body shape and vertebral regionalization to understand how elongate fishes move in water and on land.

  11. Elongation growth and gravitropic curvature in the Flammulina velutipes (Agaricales) fruiting body.

    PubMed

    Haindl, E; Monzer, J

    1994-06-01

    Differential elongation of stipe hyphae drives the gravitropic reorientation of Flammulina velutipes (Agaricales) fruiting bodies. The gravitropic curvature is strictly dependent on the presence of the transition zone between pileus and stipe. Elongation growth, providing the driving force for curvature, is also promoted by the pileus. Gravitropic curvature is successfully suppressed by clinostatic rotation, but the elongation rate is not affected. Explantation of fruiting body stipes lowers curvature and elongation rates corresponding to explant size reduction. In Flammulina, 25 mm length of transition zone explants is an efficient size for reproducible curvature and elongation during 48- to 72-h curvature tests. Submersion of specimens in aqueous medium causes cessation of the gravitropic curvature, but does not affect elongation. Thus the involvement of a diffusible factor in transmission of the curvature signal is probable. Splitting the fruiting body stipe in segments of 1/8 diameter does not suppress the gravitropic response, and the segments are individually reoriented to the vertical. It is concluded that the graviresponse of the Flammulina fruiting body is based on cellular perception of the gravistimulus and that a differential growth signal is transmitted in the stipe by a soluble factor that regulates hyphal elongation.

  12. Stimulation of root elongation and curvature by calcium

    NASA Technical Reports Server (NTRS)

    Takahashi, H.; Scott, T. K.; Suge, H.

    1992-01-01

    Ca2+ has been proposed to mediate inhibition of root elongation. However, exogenous Ca2+ at 10 or 20 millimolar, applied directly to the root cap, significantly stimulated root elongation in pea (Pisum sativum L.) and corn (Zea mays L.) seedlings. Furthermore, Ca2+ at 1 to 20 millimolar, applied unilaterally to the caps of Alaska pea roots, caused root curvature away from the Ca2+ source, which was caused by an acceleration of elongation growth on the convex side (Ca2+ side) of the roots. Roots of an agravitropic pea mutant, ageotropum, responded to a greater extent. Roots of Merit and Silver Queen corn also responded to Ca2+ in similar ways but required a higher Ca2+ concentration than that of pea roots. Roots of all other cultivars tested (additional four cultivars of pea and one of corn) curved away from the unilateral Ca2+ source as well. The Ca(2+)-stimulated curvature was substantially enhanced by light. A Ca2+ ionophore, A23187, at 20 micromolar or abscisic acid at 0.1 to 100 micromolar partially substituted for the light effect and enhanced the Ca(2+)-stimulated curvature in the dark. Unilateral application of Ca2+ to the elongation zone of intact roots or to the cut end of detipped roots caused either no curvature or very slight curvature toward the Ca2+. Thus, Ca2+ action on root elongation differs depending on its site of application. The stimulatory action of Ca2+ may involve an elevation of cytoplasmic Ca2+ in root cap cells and may partipate in root tropisms.

  13. Stimulation of root elongation and curvature by calcium

    NASA Technical Reports Server (NTRS)

    Takahashi, H.; Scott, T. K.; Suge, H.

    1992-01-01

    Ca2+ has been proposed to mediate inhibition of root elongation. However, exogenous Ca2+ at 10 or 20 millimolar, applied directly to the root cap, significantly stimulated root elongation in pea (Pisum sativum L.) and corn (Zea mays L.) seedlings. Furthermore, Ca2+ at 1 to 20 millimolar, applied unilaterally to the caps of Alaska pea roots, caused root curvature away from the Ca2+ source, which was caused by an acceleration of elongation growth on the convex side (Ca2+ side) of the roots. Roots of an agravitropic pea mutant, ageotropum, responded to a greater extent. Roots of Merit and Silver Queen corn also responded to Ca2+ in similar ways but required a higher Ca2+ concentration than that of pea roots. Roots of all other cultivars tested (additional four cultivars of pea and one of corn) curved away from the unilateral Ca2+ source as well. The Ca(2+)-stimulated curvature was substantially enhanced by light. A Ca2+ ionophore, A23187, at 20 micromolar or abscisic acid at 0.1 to 100 micromolar partially substituted for the light effect and enhanced the Ca(2+)-stimulated curvature in the dark. Unilateral application of Ca2+ to the elongation zone of intact roots or to the cut end of detipped roots caused either no curvature or very slight curvature toward the Ca2+. Thus, Ca2+ action on root elongation differs depending on its site of application. The stimulatory action of Ca2+ may involve an elevation of cytoplasmic Ca2+ in root cap cells and may partipate in root tropisms.

  14. Stimulation of root elongation and curvature by calcium.

    PubMed

    Takahashi, H; Scott, T K; Suge, H

    1992-01-01

    Ca2+ has been proposed to mediate inhibition of root elongation. However, exogenous Ca2+ at 10 or 20 millimolar, applied directly to the root cap, significantly stimulated root elongation in pea (Pisum sativum L.) and corn (Zea mays L.) seedlings. Furthermore, Ca2+ at 1 to 20 millimolar, applied unilaterally to the caps of Alaska pea roots, caused root curvature away from the Ca2+ source, which was caused by an acceleration of elongation growth on the convex side (Ca2+ side) of the roots. Roots of an agravitropic pea mutant, ageotropum, responded to a greater extent. Roots of Merit and Silver Queen corn also responded to Ca2+ in similar ways but required a higher Ca2+ concentration than that of pea roots. Roots of all other cultivars tested (additional four cultivars of pea and one of corn) curved away from the unilateral Ca2+ source as well. The Ca(2+)-stimulated curvature was substantially enhanced by light. A Ca2+ ionophore, A23187, at 20 micromolar or abscisic acid at 0.1 to 100 micromolar partially substituted for the light effect and enhanced the Ca(2+)-stimulated curvature in the dark. Unilateral application of Ca2+ to the elongation zone of intact roots or to the cut end of detipped roots caused either no curvature or very slight curvature toward the Ca2+. Thus, Ca2+ action on root elongation differs depending on its site of application. The stimulatory action of Ca2+ may involve an elevation of cytoplasmic Ca2+ in root cap cells and may partipate in root tropisms.

  15. Correlations between changes in electrical parameters and changes in cell elongation rates in gavistimulated roots

    NASA Astrophysics Data System (ADS)

    Ishikawa, H.; Evans, M. L.

    1994-08-01

    The earliest changes in growth rate following the gravistimulation of roots occur in a special group of cells between the meristem and the elongating region of the root. This zone is called the postomitotic isodiametric growth (PIG) zone and consists of cells which have ceased dividing and are expanding isodiametrically. Upon gravistimulation cells along the upper side of the PIG zone begin elongating rapidly and this accounts for much of the early growth asymmetry. There is rapid (< 30 s) hyperpolarization of cells on the upper side of the PIG zone as well as rapid uptake of potassium from the stele. We propose that there is a relationship between the rate of hydrogen ion efflux and the extent of membrane hyperpolarization in the PIG zone and that such changes in potential are an early indication of impending changes in growth performance. Although the development of auxin asymmetry in the cap and its transmission to the elongating region is considered to be the controlling factor in root gravitropism, auxin asymmetry in the cap develops only after 30 min, about the same as the lag before initiation of curvature. Although this dilemma may be partly resolved by the location of the PIG zone close to the cap, alternative explanations such as gravi-detection by the PIG zone or very rapid (electrical?) signal transmission from the cap to the PIG zone need to be considered.

  16. Promoting elongation with transcript cleavage stimulatory factors.

    PubMed

    Fish, Rachel N; Kane, Caroline M

    2002-09-13

    Transcript elongation by RNA polymerase is a dynamic process, capable of responding to a number of intrinsic and extrinsic signals. A number of elongation factors have been identified that enhance the rate or efficiency of transcription. One such class of factors facilitates RNA polymerase transcription through blocks to elongation by stimulating the polymerase to cleave the nascent RNA transcript within the elongation complex. These cleavage factors are represented by the Gre factors from prokaryotes, and TFIIS and TFIIS-like factors found in archaea and eukaryotes. High-resolution structures of RNA polymerases and the cleavage factors in conjunction with biochemical investigations and genetic analyses have provided insights into the mechanism of action of these elongation factors. However, there are yet many unanswered questions regarding the regulation of these factors and their effects on target genes.

  17. Translational Control of Cell Division by Elongator

    PubMed Central

    Bauer, Fanelie; Matsuyama, Akihisa; Candiracci, Julie; Dieu, Marc; Scheliga, Judith; Wolf, Dieter A.; Yoshida, Minoru; Hermand, Damien

    2012-01-01

    SUMMARY Elongator is required for the synthesis of the mcm5s2 modification found on tRNAs recognizing AA-ending codons. In order to obtain a global picture of the role of Elongator in translation, we used reverse protein arrays to screen the fission yeast proteome for translation defects. Unexpectedly, this revealed that Elongator inactivation mainly affected three specific functional groups including proteins implicated in cell division. The absence of Elongator results in a delay in mitosis onset and cytokinesis defects. We demonstrate that the kinase Cdr2, which is a central regulator of mitosis and cytokinesis, is under translational control by Elongator due to the Lysine codon usage bias of the cdr2 coding sequence. These findings uncover a mechanism by which the codon usage, coupled to tRNA modifications, fundamentally contributes to gene expression and cellular functions. PMID:22768388

  18. Regulation switching of Epichloë typhina within elongating perennial ryegrass leaves.

    PubMed

    Christensen, Michael J; Zhang, Xiuwen; Scott, Barry

    2008-09-01

    Epichloë and Neotyphodium spp. are clavicipitaceous fungi that form symbiotic endophytic associations with temperate grasses. The growth of these endophytes is strictly intercellular and tightly regulated, being synchronized with that of the host grass. The exception to this synchronized form of growth is the profuse growth of hyphae during development of stromata on reproductive tillers, thereby preventing emergence of the inflorescence. Here we report the occurrence of stromata on leaves of vegetative tillers of perennial ryegrass infected with E. typhina. Stroma formation was confined to leaf blades, being present as a distinct zone within an otherwise symptomless leaf. In some leaf blades two or more stromata zones were present, separated by symptomless tissue. Growth of hyphae in the symptomless zones was seldom branched, orientated parallel with the longitudinal leaf axis, and synchronised with plant growth. In contrast, hyphal growth in the stroma zones was unrestricted and highly branched. Thus in stable zones along a single leaf blade the interaction between E. typhina and its host grass alternated between synchronised, symptomless growth and a pathogenic state with unrestricted hyphal growth. These results demonstrate that the development of an inflorescence is not a prerequisite for hyphal growth leading to stroma formation and provide an ideal experimental system for investigating further how these fungi are able to switch from synchronized, symptomless growth to unrestricted stromal expression.

  19. The Effects of High Steady State Auxin Levels on Root Cell Elongation in Brachypodium[OPEN

    PubMed Central

    Pacheco-Villalobos, David; Tamaki, Takayuki; Gujas, Bojan; Jaspert, Nina; Oecking, Claudia; Bulone, Vincent; Hardtke, Christian S.

    2016-01-01

    The long-standing Acid Growth Theory of plant cell elongation posits that auxin promotes cell elongation by stimulating cell wall acidification and thus expansin action. To date, the paucity of pertinent genetic materials has precluded thorough analysis of the importance of this concept in roots. The recent isolation of mutants of the model grass species Brachypodium distachyon with dramatically enhanced root cell elongation due to increased cellular auxin levels has allowed us to address this question. We found that the primary transcriptomic effect associated with elevated steady state auxin concentration in elongating root cells is upregulation of cell wall remodeling factors, notably expansins, while plant hormone signaling pathways maintain remarkable homeostasis. These changes are specifically accompanied by reduced cell wall arabinogalactan complexity but not by increased proton excretion. On the contrary, we observed a tendency for decreased rather than increased proton extrusion from root elongation zones with higher cellular auxin levels. Moreover, similar to Brachypodium, root cell elongation is, in general, robustly buffered against external pH fluctuation in Arabidopsis thaliana. However, forced acidification through artificial proton pump activation inhibits root cell elongation. Thus, the interplay between auxin, proton pump activation, and expansin action may be more flexible in roots than in shoots. PMID:27169463

  20. Antibacterial activity on Citrullus colocynthis Leaf extract

    PubMed Central

    gowri, S. Shyamala; Priyavardhini, S.; Vasantha, K.; Umadevi, M.

    2009-01-01

    Studies on the antibacterial activities of the leaf extract of Citrullus colocynthis (Cucurbitaceae), a medicinal plant used for the treatment of various ailments was carried out using agar disc diffusion technique. The results revealed that the crude acetone extract exhibited antibacterial activities against Pseudomonas aeruginosa with zones of inhibition measuring 14.0mm. The chloroform leaf extract exhibited no antibacterial activity against Staphylococcus aureus. The minimum inhibitory concentration for the chloroform extract was 4.0mm for Escherichia coli. PMID:22557336

  1. Ancestral role of caudal genes in axis elongation and segmentation.

    PubMed

    Copf, Tijana; Schröder, Reinhard; Averof, Michalis

    2004-12-21

    caudal (cad/Cdx) genes are essential for the formation of posterior structures in Drosophila, Caenorhabditis elegans, and vertebrates. In contrast to Drosophila, the majority of arthropods generate their segments sequentially from a posteriorly located growth zone, a process known as short-germ development. caudal homologues are expressed in the growth zone of diverse short-germ arthropods, but until now their functional role in these animals had not been studied. Here, we use RNA interference to examine the function of caudal genes in two short-germ arthropods, the crustacean Artemia franciscana and the beetle Tribolium castaneum. We show that, in both species, caudal is required for the formation of most body segments. In animals with reduced levels of caudal expression, axis elongation stops, resulting in severe truncations that remove most trunk segments. We also show that caudal function is required for the early phases of segmentation and Hox gene expression. The observed phenotypes suggest that in arthropods caudal had an ancestral role in axis elongation and segmentation, and was required for the formation of most body segments. Similarities to the function of vertebrate Cdx genes in the presomitic mesoderm, from which somites are generated, indicate that this role may also predate the origin of the Bilateria.

  2. [Influence of perennial flooding and drought on growth restoration of Acorus calamus in water-level-fluctuation zone of the Three Gorges Reservoir].

    PubMed

    Li, Qiang; Gao, Xiang; Ding, Wu-quan; Zhu, Qi-hong; Ou, Yuan; Liu, Yu

    2012-08-01

    Acorus calamus L. is a common kind of wetland plant species in the Three Gorges Reservoir. In this study, we investigated the influence of perennial flooding on growth restoration of A. calamus in the lightless conditions and the drought stress on this plant species' growth after flooding. Our research provided the scientific basis for the selection of candidate species for vegetations restoration in water-level-fluctuation zone of the Three Gorges Reservoir. A. calamus plants were exposed to waters in the lightless conditions in September 2009 and September 2010 respectively and taken away from the waters and grew in natural conditions in the following March, April and May (named as S1, S2, S3). All plants in the control, S1 and S2 groups were challenged with drought stress in May for 20 days. During the experiment, the plant number and leaf number were recorded regularly, as well as leaf length and leaf width. The results showed that flooding restrained the germination of the plants with much less plant in flooding groups than the control, and the plant germination rate had inverse relation to the flooding time. Flooding promoted formation and elongation of the leaves in S1 and S2 groups, which showed higher leaf growth parameters, such as leaf length, leaf number, total leaf length of one plant and total leaf length of all plants than the control. However, all of these growth parameters in S3 group had significantly lower values compared to the control. The survival rate of the plants after flooding decreased significantly with longer flooding time. Besides, the leaf length and leaf width in S1 and S2 groups increased significantly but with decreased leaf number. Additionally, all growth parameters (leaf length, leaf width, leaf number, total leaf number, total leaf length of one plant, total leaf length of all plants) in S3 group decreased remarkably. Furthermore, drought decreased the values of all growth parameters and the plant number in the control, S1 and

  3. Hormonal control of cell division and elongation along differentiation trajectories in roots.

    PubMed

    Takatsuka, Hirotomo; Umeda, Masaaki

    2014-06-01

    The continuous development of roots is supported by a sustainable system for cell production and growth at the root tip. In the stem cell niche that consists of a quiescent centre and surrounding stem cells, an undifferentiated state and low mitotic activity are preserved by the action of auxin and abscisic acid. Stem cell daughters divide several times in the proximal meristem, where auxin and gibberellin mainly promote cell proliferation. Cells then elongate with the help of gibberellin, and become finally differentiated as a constituent of a cell file in the elongation/differentiation zone. In the model plant Arabidopsis thaliana, the transition zone is located between the proximal meristem and the elongation/differentiation zone, and plays an important role in switching from mitosis to the endoreplication that causes DNA polyploidization. Recent studies have shown that cytokinins are essentially required for this transition by antagonizing auxin signalling and promoting degradation of mitotic regulators. In each root zone, different phytohormones interact with one another and coordinately control cell proliferation, cell elongation, cell differentiation, and endoreplication. Such hormonal networks maintain the elaborate structure of the root tip under various environmental conditions. In this review, we summarize and discuss key issues related to hormonal regulation of root growth, and describe how phytohormones are associated with the control of cell cycle machinery. © The Author 2014. Published by Oxford University Press on behalf of the Society for Experimental Biology. All rights reserved. For permissions, please email: journals.permissions@oup.com.

  4. A review of penile elongation surgery

    PubMed Central

    Gillis, Joshua

    2017-01-01

    Penile elongation surgery is less commonly performed in the public sector, but involves a collaborative approach between urology and plastic surgery. Congenital and acquired micropenis are the classic surgical indications for penile elongation surgery. The goal of intervention in these patients is to restore a functional penis size in order to allow normal standing micturition, enable satisfying sexual intercourse and improve patient quality of life. Many men seeking elongation actually have normal length penises, but perceive themselves to be small, a psychologic condition termed ‘penile dysmorphophobia’. This paper will review the anatomy and embryology of congenital micropenis and discuss both conservative and surgical management options for men seeking penile elongation therapy. PMID:28217452

  5. Elongated Deposits in Southern Elysium Planitia, Mars

    NASA Astrophysics Data System (ADS)

    Nussbaumer, J. W.

    2012-03-01

    In the Elysium Planitia region, deposits have elongated elevations that resemble terrestrial drumlins or yardangs. Drumlins and drumlin clusters are glacial landforms that have been extensively studied. In contrast, Yardangs are formed by wind.

  6. Effects of elongation delay in transcription dynamics.

    PubMed

    Zhang, Xuan; Jin, Huiqin; Yang, Zhuoqin; Lei, Jinzhi

    2014-12-01

    In the transcription process, elongation delay is induced by the movement of RNA polymerases (RNAP) along the DNA sequence, and can result in changes in the transcription dynamics. This paper studies the transcription dynamics that involved the elongation delay and effects of cell division and DNA replication. The stochastic process of gene expression is modeled with delay chemical master equation with periodic coefficients, and is studied numerically through the stochastic simulation algorithm with delay. We show that the average transcription level approaches to a periodic dynamics over cell cycles at homeostasis, and the elongation delay can reduce the transcription level and increase the transcription noise. Moreover, the transcription elongation can induce bimodal distribution of mRNA levels that can be measured by the techniques of flow cytometry.

  7. Numerical Experiments with Flows of Elongated Granules

    DTIC Science & Technology

    1992-01-01

    NASA AVSCOM Technical Memorandum 105567 Technical Report 91- C- 006 𔃼e- 0ok, Numerical Experiments With Flows of Elongated Granules AD-A251 853 DTIC...EXPERIMENTS WITH FLOWS OF ELONGATED GRANULES H.G. Elrod 14 Cromwell Court Old Saybrook, Connecticut 06475 and D.E. Brewe Propulsion Directorate U.S. Army...granular flows (1) between two infinite, counter-moving, parallel, roughened walls, and (2) for an infinitely-wide slider. Each granule is simulated by a

  8. Mutual interdependence of splicing and transcription elongation.

    PubMed

    Brzyżek, Grzegorz; Świeżewski, Szymon

    2015-01-01

    Transcription and splicing are intrinsically linked, as splicing needs a pre-mRNA substrate to commence. The more nuanced view is that the rate of transcription contributes to splicing regulation. On the other hand there is accumulating evidence that splicing has an active role in controlling transcription elongation by DNA-dependent RNA polymerase II (RNAP II). We briefly review those mechanisms and propose a unifying model where splicing controls transcription elongation to provide an optimal timing for successive rounds of splicing.

  9. Visualization of large elongated DNA molecules.

    PubMed

    Lee, Jinyong; Kim, Yongkyun; Lee, Seonghyun; Jo, Kyubong

    2015-09-01

    Long and linear DNA molecules are the mainstream single-molecule analytes for a variety of biochemical analysis within microfluidic devices, including functionalized surfaces and nanostructures. However, for biochemical analysis, large DNA molecules have to be unraveled, elongated, and visualized to obtain biochemical and genomic information. To date, elongated DNA molecules have been exploited in the development of a number of genome analysis systems as well as for the study of polymer physics due to the advantage of direct visualization of single DNA molecule. Moreover, each single DNA molecule provides individual information, which makes it useful for stochastic event analysis. Therefore, numerous studies of enzymatic random motions have been performed on a large elongated DNA molecule. In this review, we introduce mechanisms to elongate DNA molecules using microfluidics and nanostructures in the beginning. Secondly, we discuss how elongated DNA molecules have been utilized to obtain biochemical and genomic information by direct visualization of DNA molecules. Finally, we reviewed the approaches used to study the interaction of proteins and large DNA molecules. Although DNA-protein interactions have been investigated for many decades, it is noticeable that there have been significant achievements for the last five years. Therefore, we focus mainly on recent developments for monitoring enzymatic activity on large elongated DNA molecules.

  10. Synergistic action of auxin and ethylene on root elongation inhibition is caused by a reduction of epidermal cell length.

    PubMed

    Alarcón, M Victoria; Lloret, Pedro G; Salguero, Julio

    2014-01-01

    Auxin and ethylene have been largely reported to reduce root elongation in maize primary root. However the effects of auxin are greater than those caused by ethylene. Although auxin stimulates ethylene biosynthesis through the specific increase of ACC synthase, the auxin inhibitory effect on root elongation is not mediated by the auxin-induced increase of ethylene production. Recently it has been demonstrated that root inhibition by the application of the synthetic auxin NAA (1-naphtalenacetic acid) is increased if combined with the ethylene precursor ACC (1-aminocyclopropane-1-carboxilic acid) when both compounds are applied at very low concentrations.   Root elongation is basically the result of two processes: a) cell divisions in the meristem where meristematic cells continuously generate new cells and b) subsequently polarized growth by elongation along the root axis as cells leave the meristem and enter the root elongation zone. Our results indicate that exogenous auxin reduced both root elongation and epidermal cell length. In a different way, ethylene at very low concentrations only inhibited root elongation without affecting significantly epidermal cell length. However, these concentrations of ethylene increased the inhibitory effect of auxin on root elongation and cell length. Consequently the results support the hypothesis that ethylene acts synergistically with auxin in the regulation of root elongation and that inhibition by both hormones is due, at least partially, to the reduction of cell length in the epidermal layer.

  11. Synergistic action of auxin and ethylene on root elongation inhibition is caused by a reduction of epidermal cell length

    PubMed Central

    Alarcón, M Victoria; Lloret, Pedro G; Salguero, Julio

    2014-01-01

    Auxin and ethylene have been largely reported to reduce root elongation in maize primary root. However the effects of auxin are greater than those caused by ethylene. Although auxin stimulates ethylene biosynthesis through the specific increase of ACC synthase, the auxin inhibitory effect on root elongation is not mediated by the auxin-induced increase of ethylene production. Recently it has been demonstrated that root inhibition by the application of the synthetic auxin NAA (1-naphtalenacetic acid) is increased if combined with the ethylene precursor ACC (1-aminocyclopropane-1-carboxilic acid) when both compounds are applied at very low concentrations. Root elongation is basically the result of two processes: a) cell divisions in the meristem where meristematic cells continuously generate new cells and b) subsequently polarized growth by elongation along the root axis as cells leave the meristem and enter the root elongation zone. Our results indicate that exogenous auxin reduced both root elongation and epidermal cell length. In a different way, ethylene at very low concentrations only inhibited root elongation without affecting significantly epidermal cell length. However, these concentrations of ethylene increased the inhibitory effect of auxin on root elongation and cell length. Consequently the results support the hypothesis that ethylene acts synergistically with auxin in the regulation of root elongation and that inhibition by both hormones is due, at least partially, to the reduction of cell length in the epidermal layer. PMID:24598313

  12. Effect of Gibberellic Acid on Elongation and Longevity of Coleus Petioles 1

    PubMed Central

    Jacobs, W. P.; Kirk, Susan C.

    1966-01-01

    The effects of gibberellic acid on the longevity and elongation of variously aged, debladed petioles of Coleus blumei were studied, with particular reference to the hypotheses 1) that auxin increases longevity by increasing growth, and 2) that gibberellic acid acts by increasing the endogenous levels of auxin. Gibberellic acid, substituted for the leaf blades, significantly decreased longevity of younger petioles, as measured by days or hours to abscission. Gibberellic acid also decreased the longevity resulting from 0.1% indoleacetic acid. This is the opposite of the effect expected if it is increasing auxin levels in the petiole. In its effect on elongation of younger petioles, however, gibberellic acid did act in the direction expected if it were increasing effective levels of auxin in the petiole. The elongation rate from 0.1% gibberellic acid plus 0.1% indoleacetic acid in lanolin was as large or larger than that for 1.0% indoleacetic acid. Petioles which were 10 or more weeks old (i.e., at positions 5+ below the apical bud were not affected by 0.1% gibberellic acid in either longevity or rate of elongation, with or without 0.1% indoleacetic acid. Since 1.0% indoleacetic acid increases both longevity and elongation rate of these petioles over 0.1% indoleacetic acid, gibberellic acid is clearly not acting on older petioles as if it were increasing effective auxin levels). PMID:16656279

  13. Limited Correlation between Expansin Gene Expression and Elongation Growth Rate1

    PubMed Central

    Caderas, Doina; Muster, Matthias; Vogler, Hannes; Mandel, Therese; Rose, Jocelyn K.C.; McQueen-Mason, Simon; Kuhlemeier, Cris

    2000-01-01

    The aim of this work was to study the role of the cell wall protein expansin in elongation growth. Expansins increase cell wall extensibility in vitro and are thought to be involved in cell elongation. Here, we studied the regulation of two tomato (Lycopersicon esculentum cv Moneymaker) expansin genes, LeExp2 and LeExp18, in rapidly expanding tissues. LeExp2 was strongly expressed in the elongation zone of hypocotyls and in the faster growing stem part during gravitropic stimulation. LeExp18 expression did not correlate with elongation growth. Exogenous application of hormones showed a substantial auxin-stimulation of LeExp2 mRNA in etiolated hypocotyls and a weaker auxin-stimulation of LeExp18 mRNA in stem tissue. Analysis of transcript accumulation revealed higher levels of LeExp2 and LeExp18 in light-treated, slow-growing tissue than in dark-treated, rapidly elongating tissue. Expansin protein levels and cell wall extension activities were similar in light- and dark-grown hypocotyl extracts. The results show a strong correlation between expansin gene expression and growth rate, but this correlation is not absolute. We conclude that elongation growth is likely to be controlled by expansin acting in concert with other factors that may limit growth under some physiological conditions. PMID:10938357

  14. The RNA polymerase II elongation complex.

    PubMed

    Aso, T; Conaway, J W; Conaway, R C

    1995-11-01

    The initiation stage of transcription by RNA polymerase II has long been regarded as the primary site for regulation of eukaryotic gene expression. Nevertheless, a growing body of evidence reveals that the RNA polymerase II elongation complex is also a major target for regulation. Biochemical studies are implicating an increasing number of transcription factors in the regulation of elongation, and these transcription factors are being found to function by a diverse collection of mechanisms. Moreover, unexpected features of the structure and catalytic mechanism of RNA polymerase II are forcing a reconsideration of long-held views on the mechanics of some of the most basic aspects of polymerase function. In this review, we will describe recent insights into the structures and functions of RNA polymerase II and the transcription factors that control its activity during the elongation stage of eukaryotic messenger RNA synthesis.

  15. Architecture of the yeast Elongator complex.

    PubMed

    Dauden, Maria I; Kosinski, Jan; Kolaj-Robin, Olga; Desfosses, Ambroise; Ori, Alessandro; Faux, Celine; Hoffmann, Niklas A; Onuma, Osita F; Breunig, Karin D; Beck, Martin; Sachse, Carsten; Séraphin, Bertrand; Glatt, Sebastian; Müller, Christoph W

    2017-02-01

    The highly conserved eukaryotic Elongator complex performs specific chemical modifications on wobble base uridines of tRNAs, which are essential for proteome stability and homeostasis. The complex is formed by six individual subunits (Elp1-6) that are all equally important for its tRNA modification activity. However, its overall architecture and the detailed reaction mechanism remain elusive. Here, we report the structures of the fully assembled yeast Elongator and the Elp123 sub-complex solved by an integrative structure determination approach showing that two copies of the Elp1, Elp2, and Elp3 subunits form a two-lobed scaffold, which binds Elp456 asymmetrically. Our topological models are consistent with previous studies on individual subunits and further validated by complementary biochemical analyses. Our study provides a structural framework on how the tRNA modification activity is carried out by Elongator.

  16. A random cell motility gradient downstream of FGF controls elongation of an amniote embryo

    PubMed Central

    Bénazéraf, Bertrand; Francois, Paul; Baker, Ruth E.; Denans, Nicolas; Little, Charles D.; Pourquie, Olivier

    2011-01-01

    Vertebrate embryos are characterized by an elongated antero-posterior (AP) body axis, which forms by progressive cell deposition from a posterior growth zone in the embryo. Here, we used tissue ablation in the chicken embryo to demonstrate that the caudal presomitic mesoderm (PSM) plays a key role in axis elongation. Using time-lapse microscopy, we analysed the movements of fluorescently labelled cells in the PSM during embryo elongation which revealed a clear posterior-to-anterior gradient of cell motility and directionality in the PSM. We tracked the movement of the PSM extracellular matrix in parallel with the labelled cells and subtracted the extracellular matrix movement from the global motion of cells. After subtraction, cell motility remained graded but lacked directionality, indicating that the posterior cell movements associated with axis elongation in the PSM are not intrinsic but reflect tissue deformation. The gradient of cell motion along the PSM parallels the fibroblast growth factor (FGF)/mitogen-activated protein kinase (MAPK) gradient 1, which has been implicated in the control of cell motility in this tissue2. Both FGF signalling gain- and loss-of-function experiments lead to disruption of the motility gradient and a slowing down of axis elongation. Furthermore, embryos treated with cell movement inhibitors (Blebbistatin or RhoK inhibitor), but not cell cycle inhibitors, show a slower axis elongation rate. We propose that the gradient of random cell motility downstream of FGF signalling in the PSM controls posterior elongation in the amniote embryo. Our data suggest that tissue elongation is an emergent property that arises from the collective regulation of graded, random cell motion rather than by the regulation of directionality of individual cellular movements. PMID:20613841

  17. Identification of genes involved in the ACC-mediated control of root cell elongation in Arabidopsis thaliana.

    PubMed

    Markakis, Marios Nektarios; De Cnodder, Tinne; Lewandowski, Michal; Simon, Damien; Boron, Agnieszka; Balcerowicz, Daria; Doubbo, Thanaa; Taconnat, Ludivine; Renou, Jean-Pierre; Höfte, Herman; Verbelen, Jean-Pierre; Vissenberg, Kris

    2012-11-07

    Along the root axis of Arabidopsis thaliana, cells pass through different developmental stages. In the apical meristem repeated cycles of division increase the numbers of cells. Upon leaving the meristem, these cells pass the transition zone where they are physiologically and mechanically prepared to undergo subsequent rapid elongation. During the process of elongation epidermal cells increase their length by 300% in a couple of hours. When elongation ceases, the cells acquire their final size, shape and functions (in the differentiation zone). Ethylene administered as its precursor 1-aminocyclopropane-1-carboxylic acid (ACC) is capable of inhibiting elongation in a concentration-dependent way. Using a microarray analysis, genes and/or processes involved in this elongation arrest are identified. Using a CATMA-microarray analysis performed on control and 3h ACC-treated roots, 240 differentially expressed genes were identified. Quantitative Real-Time RT-PCR analysis of the 10 most up and down regulated genes combined with literature search confirmed the accurateness of the analysis. This revealed that inhibition of cell elongation is, at least partly, caused by restricting the events that under normal growth conditions initiate elongation and by increasing the processes that normally stop cellular elongation at the end of the elongation/onset of differentiation zone. ACC interferes with cell elongation in the Arabidopsis thaliana roots by inhibiting cells from entering the elongation process and by immediately stimulating the formation of cross-links in cell wall components, diminishing the remaining elongation capacity. From the analysis of the differentially expressed genes, it becomes clear that many genes identified in this response, are also involved in several other kind of stress responses. This suggests that many responses originate from individual elicitors, but that somewhere in the downstream signaling cascade, these are converged to a 'common pathway

  18. Identification of genes involved in the ACC-mediated control of root cell elongation in Arabidopsis thaliana

    PubMed Central

    2012-01-01

    Background Along the root axis of Arabidopsis thaliana, cells pass through different developmental stages. In the apical meristem repeated cycles of division increase the numbers of cells. Upon leaving the meristem, these cells pass the transition zone where they are physiologically and mechanically prepared to undergo subsequent rapid elongation. During the process of elongation epidermal cells increase their length by 300% in a couple of hours. When elongation ceases, the cells acquire their final size, shape and functions (in the differentiation zone). Ethylene administered as its precursor 1-aminocyclopropane-1-carboxylic acid (ACC) is capable of inhibiting elongation in a concentration-dependent way. Using a microarray analysis, genes and/or processes involved in this elongation arrest are identified. Results Using a CATMA-microarray analysis performed on control and 3h ACC-treated roots, 240 differentially expressed genes were identified. Quantitative Real-Time RT-PCR analysis of the 10 most up and down regulated genes combined with literature search confirmed the accurateness of the analysis. This revealed that inhibition of cell elongation is, at least partly, caused by restricting the events that under normal growth conditions initiate elongation and by increasing the processes that normally stop cellular elongation at the end of the elongation/onset of differentiation zone. Conclusions ACC interferes with cell elongation in the Arabidopsis thaliana roots by inhibiting cells from entering the elongation process and by immediately stimulating the formation of cross-links in cell wall components, diminishing the remaining elongation capacity. From the analysis of the differentially expressed genes, it becomes clear that many genes identified in this response, are also involved in several other kind of stress responses. This suggests that many responses originate from individual elicitors, but that somewhere in the downstream signaling cascade, these are

  19. Scatter factor corrections for elongated fields.

    PubMed

    Higgins, P D; Sohn, W H; Sibata, C H; McCarthy, W A

    1989-01-01

    Measurements have been made to determine scatter factor corrections for elongated fields of Cobalt-60 and for nominal linear accelerator energies of 6 MV (Siemens Mevatron 67) and 18 MV (AECL Therac 20). It was found that for every energy the collimator scatter factor varies by 2% or more as the field length-to-width ratio increases beyond 3:1. The phantom scatter factor is independent of which collimator pair is elongated at these energies. For 18 MV photons it was found that the collimator scatter factor is complicated by field-size-dependent backscatter into the beam monitor.

  20. Scatter factor corrections for elongated fields

    SciTech Connect

    Higgins, P.D.; Sohn, W.H.; Sibata, C.H.; McCarthy, W.A. )

    1989-09-01

    Measurements have been made to determine scatter factor corrections for elongated fields of Cobalt-60 and for nominal linear accelerator energies of 6 MV (Siemens Mevatron 67) and 18 MV (AECL Therac 20). It was found that for every energy the collimator scatter factor varies by 2% or more as the field length-to-width ratio increases beyond 3:1. The phantom scatter factor is independent of which collimator pair is elongated at these energies. For 18 MV photons it was found that the collimator scatter factor is complicated by field-size-dependent backscatter into the beam monitor.

  1. The cauliflower Orange gene enhances petiole elongation by suppressing expression of eukaryotic release factor 1.

    PubMed

    Zhou, Xiangjun; Sun, Tian-Hu; Wang, Ning; Ling, Hong-Qing; Lu, Shan; Li, Li

    2011-04-01

    The cauliflower (Brassica oleracea var. botrytis) Orange (Or) gene affects plant growth and development in addition to conferring β-carotene accumulation. This study was undertaken to investigate the molecular basis for the effects of the Or gene mutation in on plant growth. The OR protein was found to interact with cauliflower and Arabidopsis eukaryotic release factor 1-2 (eRF1-2), a member of the eRF1 family, by yeast two-hybrid analysis and by bimolecular fluorescence complementation (BiFC) assay. Concomitantly, the Or mutant showed reduced expression of the BoeRF1 family genes. Transgenic cauliflower plants with suppressed expression of BoeRF1-2 and BoeRF1-3 were generated by RNA interference. Like the Or mutant, the BoeRF1 RNAi lines showed increased elongation of the leaf petiole. This long-petiole phenotype was largely caused by enhanced cell elongation, which resulted from increased cell length and elevated expression of genes involved in cell-wall loosening. These findings demonstrate that the cauliflower Or gene controls petiole elongation by suppressing the expression of eRF1 genes, and provide new insights into the molecular mechanism of leaf petiole regulation. © 2010 The Authors. New Phytologist © 2010 New Phytologist Trust.

  2. Interplay between DNA supercoiling and transcription elongation.

    PubMed

    Ma, Jie; Wang, Michelle

    2014-01-01

    Transcription-coupled DNA supercoiling has been shown to be an important regulator of transcription that is broadly present in the cell. Here we review experimental work which shows that RNA polymerase is a powerful torsional motor that can alter DNA topology and structure, and DNA supercoiling in turn directly affects transcription elongation.

  3. Cell elongation is an adaptive response for clearing long chromatid arms from the cleavage plane.

    PubMed

    Kotadia, Shaila; Montembault, Emilie; Sullivan, William; Royou, Anne

    2012-11-26

    Chromosome segregation must be coordinated with cell cleavage to ensure correct transmission of the genome to daughter cells. Here we identify a novel mechanism by which Drosophila melanogaster neuronal stem cells coordinate sister chromatid segregation with cleavage furrow ingression. Cells adapted to a dramatic increase in chromatid arm length by transiently elongating during anaphase/telophase. The degree of cell elongation correlated with the length of the trailing chromatid arms and was concomitant with a slight increase in spindle length and an enlargement of the zone of cortical myosin distribution. Rho guanine-nucleotide exchange factor (Pebble)-depleted cells failed to elongate during segregation of long chromatids. As a result, Pebble-depleted adult flies exhibited morphological defects likely caused by cell death during development. These studies reveal a novel pathway linking trailing chromatid arms and cortical myosin that ensures the clearance of chromatids from the cleavage plane at the appropriate time during cytokinesis, thus preserving genome integrity.

  4. Leaf seal for gas turbine stator shrouds and a nozzle band

    DOEpatents

    Burdgick, Steven Sebastian; Sexton, Brendan Francis

    2002-01-01

    A leaf seal assembly is secured to the trailing edge of a shroud segment for sealing between the shroud segment and the leading edge side wall of a nozzle outer band. The leaf seal includes a circumferentially elongated seal plate biased by a pair of spring clips disposed in a groove along the trailing edge of the shroud segment to maintain the seal plate in engagement with the flange on the leading edge side wall of the nozzle outer band. The leaf seal plate and spring clips receive pins tack-welded to the shroud segment to secure the leaf seal assembly in place.

  5. Species-specific contribution of volumetric growth and tissue convergence to posterior body elongation in vertebrates.

    PubMed

    Steventon, Ben; Duarte, Fernando; Lagadec, Ronan; Mazan, Sylvie; Nicolas, Jean-François; Hirsinger, Estelle

    2016-05-15

    Posterior body elongation is a widespread mechanism propelling the generation of the metazoan body plan. The posterior growth model predicts that a posterior growth zone generates sufficient tissue volume to elongate the posterior body. However, there are energy supply-related differences between vertebrates in the degree to which growth occurs concomitantly with embryogenesis. By applying a multi-scalar morphometric analysis in zebrafish embryos, we show that posterior body elongation is generated by an influx of cells from lateral regions, by convergence-extension of cells as they exit the tailbud, and finally by a late volumetric growth in the spinal cord and notochord. Importantly, the unsegmented region does not generate additional tissue volume. Fibroblast growth factor inhibition blocks tissue convergence rather than volumetric growth, showing that a conserved molecular mechanism can control convergent morphogenesis through different cell behaviours. Finally, via a comparative morphometric analysis in lamprey, dogfish, zebrafish and mouse, we propose that elongation via posterior volumetric growth is linked to increased energy supply and is associated with an overall increase in volumetric growth and elongation. © 2016. Published by The Company of Biologists Ltd.

  6. Vibrational modes of elongated sessile liquid droplets.

    PubMed

    Temperton, Robert H; Sharp, James S

    2013-04-16

    Vibrations of small (microliter) sessile liquid droplets were studied using a simple optical deflection technique. The droplets were made to elongate in one direction by taking advantage of the anisotropic wetting of the liquids on structured diffraction grating surfaces. They were vibrated by applying a puff of nitrogen gas. Motion of the droplets was monitored by scattering laser light from their surfaces. The scattered light was collected using a photodiode, and the resulting time-dependent intensity signals were Fourier-transformed to obtain the vibrational response of the drops. The vibrational spectra of elongated sessile drops were observed to contain two closely spaced peaks. A simple model that considers the frequency of capillary wave fluctuations on the surfaces of the drops was used to show that the vibrational frequencies of these peaks correspond to standing wave states that exist along the major and minor profile lengths of the droplets.

  7. Sound propagation in elongated superfluid fermionic clouds

    SciTech Connect

    Capuzzi, P.; Vignolo, P.; Federici, F.; Tosi, M. P.

    2006-02-15

    We use hydrodynamic equations to study sound propagation in a superfluid Fermi gas at zero temperature inside a strongly elongated cigar-shaped trap, with main attention to the transition from the BCS to the unitary regime. First, we treat the role of the radial density profile in the limit of a cylindrical geometry and then evaluate numerically the effect of the axial confinement in a configuration in which a hole is present in the gas density at the center of the trap. We find that in a strongly elongated trap the speed of sound in both the BCS and the unitary regime differs by a factor {radical}(3/5) from that in a homogeneous three-dimensional superfluid. The predictions of the theory could be tested by measurements of sound-wave propagation in a setup such as that exploited by Andrews et al. [Phys. Rev. Lett. 79, 553 (1997)] for an atomic Bose-Einstein condensate.

  8. Vertically stabilized elongated cross-section tokamak

    DOEpatents

    Sheffield, George V.

    1977-01-01

    This invention provides a vertically stabilized, non-circular (minor) cross-section, toroidal plasma column characterized by an external separatrix. To this end, a specific poloidal coil means is added outside a toroidal plasma column containing an endless plasma current in a tokamak to produce a rectangular cross-section plasma column along the equilibrium axis of the plasma column. By elongating the spacing between the poloidal coil means the plasma cross-section is vertically elongated, while maintaining vertical stability, efficiently to increase the poloidal flux in linear proportion to the plasma cross-section height to achieve a much greater plasma volume than could be achieved with the heretofore known round cross-section plasma columns. Also, vertical stability is enhanced over an elliptical cross-section plasma column, and poloidal magnetic divertors are achieved.

  9. Measuring Hole Elongation in Bolted Joints

    NASA Technical Reports Server (NTRS)

    Wichorek, G. R.

    1986-01-01

    Measurement does not affect joint parameters. Verification of analytical and strength-prediction methods for bolted composite joints based generally on data obtained experimentally from double-lap-joint specimens. In mechanically fastened joints, stresses maximal at fastener holes. Ability to measure accurately hole elongations without affecting joint parameters provides better understanding of elastic and plastic behavior of joint material leading to failure mechanisms in mechanically fastened joints required for design of more-efficient, lightweight composite joints.

  10. Optics for multimode lasers with elongated depth of field

    NASA Astrophysics Data System (ADS)

    Laskin, Alexander; Laskin, Vadim; Ostrun, Aleksei

    2017-02-01

    Modern multimode high-power lasers are widely used in industrial applications and control of their radiation, especially by focusing, is of great importance. Because of relatively low optical quality, characterized by high values of specifications Beam Parameter Product (BPP) or M², the depth of field by focusing of multimode laser radiation is narrow. At the same time laser technologies like deep penetration welding, cutting of thick metal sheets get benefits from elongated depth of field in area of focal plane, therefore increasing of zone along optical axis with minimized spot size is important technical task. As a solution it is suggested to apply refractive optical systems splitting an initial laser beam into several beamlets, which are focused in different foci separated along optical axis with providing reliable control of energy portions in each separate focus, independently of beam size or mode structure. With the multi-focus optics, the length of zone of material processing along optical axis is defined rather by distances between separate foci, which are determined by optical design of the optics and can be chosen according to requirements of a particular laser technology. Due to stability of the distances between foci there is provided stability of a technology process. This paper describes some design features of refractive multi-focus optics, examples of real implementations and experimental results will be presented as well.

  11. Elongational viscosity of photo-oxidated LDPE

    SciTech Connect

    Rolón-Garrido, Víctor H. E-mail: manfred.wagner@tu-berlin.de; Wagner, Manfred H. E-mail: manfred.wagner@tu-berlin.de

    2014-05-15

    Sheets of low-density polyethylene (LDPE) were photo-oxidatively treated at room temperature, and subsequently characterized rheologically in the melt state by shear and uniaxial extensional experiments. For photo-oxidation, a xenon lamp was used to irradiate the samples for times between 1 day and 6 weeks. Linear-viscoelastic characterization was performed in a temperature range of 130 to 220°C to obtain the master curve at 170°C, the reference temperature at which the elongational viscosities were measured. Linear viscoelasticity is increasingly affected by increasing photo-oxidation due to crosslinking of LDPE, as corroborated by an increasing gel fraction as determined by a solvent extraction method. The elongational measurements reveal a strong enhancement of strain hardening until a saturation level is achieved. The elongational data are analyzed in the frame work of two constitutive equations, the rubber-like liquid and the molecular stress function models. Within the experimental window, timedeformation separability is confirmed for all samples, independent of the degree of photo-oxidation.

  12. Elongational viscosity of photo-oxidated LDPE

    NASA Astrophysics Data System (ADS)

    Rolón-Garrido, Víctor H.; Wagner, Manfred H.

    2014-05-01

    Sheets of low-density polyethylene (LDPE) were photo-oxidatively treated at room temperature, and subsequently characterized rheologically in the melt state by shear and uniaxial extensional experiments. For photo-oxidation, a xenon lamp was used to irradiate the samples for times between 1 day and 6 weeks. Linear-viscoelastic characterization was performed in a temperature range of 130 to 220°C to obtain the master curve at 170°C, the reference temperature at which the elongational viscosities were measured. Linear viscoelasticity is increasingly affected by increasing photo-oxidation due to crosslinking of LDPE, as corroborated by an increasing gel fraction as determined by a solvent extraction method. The elongational measurements reveal a strong enhancement of strain hardening until a saturation level is achieved. The elongational data are analyzed in the frame work of two constitutive equations, the rubber-like liquid and the molecular stress function models. Within the experimental window, timedeformation separability is confirmed for all samples, independent of the degree of photo-oxidation.

  13. Quasigeostrohpic flow over isolated elongated topography

    NASA Astrophysics Data System (ADS)

    Johnson, E. R.

    1982-09-01

    The finite amplitude perturbations to a uniform stream caused by the presence of elongated topography is considered using two simple models. The first considers elliptic seamounts with scales L and l ( L ⪖ l) and gives a smooth interpolation between axisymmetric models L ; l at one extreme and infinite ridges of fixed cross-section L å l at the other. Basing the Rossby number of the flow on the shorter scale gives blocking heights of order unity for all elongations, whereas it is the longer scale that determines the horizontal extent of the region affected by the topography. The second model considers greatly elongated topography (L å l) of variable cross section showing that the topographic velocity parallel to the ridges is given by ƒ A∗/2d , where A∗ is the local cross-section area, d the depth, and f the Coriolis parameter. The component perpendicular to the ridge is obtained directly from the parallel component via a linear transform. Topographically generated velocities may thus be obtained rapidly from contours of bottom topography and an example is given using the seamount 'Brontosaurus Bump' from GOULD, HENDRY AND HUPPERT (Deep-Sea Research, 28, 409-440, 1981).

  14. From boron carbide to glass: Absorption of an elongated high-speed projectile in brittle materials

    NASA Astrophysics Data System (ADS)

    Rumyantsev, B. V.

    2016-09-01

    Penetration into boron carbide of an elongated high-speed projectile in the form of a copper jet produced by an explosion of a cumulative charge is studied. The efficiency of absorption of a copper jet in different brittle materials for evaluating their protective ability is compared. Conditions for the absence of the influence of the lateral unloading wave on the penetration zone, which provide the minimum penetration depth, are determined.

  15. The blue light receptor Phototropin 1 suppresses lateral root growth by controlling cell elongation.

    PubMed

    Moni, A; Lee, A-Y; Briggs, W R; Han, I-S

    2015-01-01

    We investigated the relationship between the blue light receptor phototropin 1 (phot1) and lateral root growth in Arabidopsis thaliana seedlings. Fluorescence and confocal microscopy images, as well as PHOT1 mRNA expression studies provide evidence that it is highly expressed in the elongation zone of lateral roots where auxin is accumulating. However, treatment with the auxin transport inhibitor N-1-naphthylphthalamic acid significantly reduced PHOT1 expression in this zone. In addition, PHOT1 expression was higher in darkness than in light. The total number of lateral roots was higher in the phot1 mutant than in wild-type Arabidopsis. Cells in the elongation zone of lateral roots of the phot1 mutant were longer than those of wild-type lateral roots. These findings suggest that PHOT1 plays a role(s) in elongation of lateral roots through the control of an auxin-related signalling pathway. © 2014 German Botanical Society and The Royal Botanical Society of the Netherlands.

  16. Stiff mutant genes of phycomyces affect turgor pressure and wall mechanical properties to regulate elongation growth rate.

    PubMed

    Ortega, Joseph K E; Munoz, Cindy M; Blakley, Scott E; Truong, Jason T; Ortega, Elena L

    2012-01-01

    Regulation of cell growth is paramount to all living organisms. In plants, algae and fungi, regulation of expansive growth of cells is required for development and morphogenesis. Also, many sensory responses of stage IVb sporangiophores of Phycomyces blakesleeanus are produced by regulating elongation growth rate (growth responses) and differential elongation growth rate (tropic responses). "Stiff" mutant sporangiophores exhibit diminished tropic responses and are found to be defective in at least five genes; madD, E, F, G, and J. Prior experimental research suggests that the defective genes affect growth regulation, but this was not verified. All the growth of the single-celled stalk of the stage IVb sporangiophore occurs in a short region termed the "growth zone." Prior experimental and theoretical research indicates that elongation growth rate of the stage IVb sporangiophore can be regulated by controlling the cell wall mechanical properties within the growth zone and the magnitude of the turgor pressure. A quantitative biophysical model for elongation growth rate is required to elucidate the relationship between wall mechanical properties and turgor pressure during growth regulation. In this study, it is hypothesized that the mechanical properties of the wall within the growth zone of stiff mutant sporangiophores are different compared to wild type (WT). A biophysical equation for elongation growth rate is derived for fungal and plant cells with a growth zone. Two strains of stiff mutants are studied, C149 madD120 (-) and C216 geo- (-). Experimental results demonstrate that turgor pressure is larger but irreversible wall deformation rates within the growth zone and growth zone length are smaller for stiff mutant sporangiophores compared to WT. These findings can explain the diminished tropic responses of the stiff mutant sporangiophores. It is speculated that the defective genes affect the amount of wall-building material delivered to the inner cell wall.

  17. Stiff Mutant Genes of Phycomyces Affect Turgor Pressure and Wall Mechanical Properties to Regulate Elongation Growth Rate

    PubMed Central

    Ortega, Joseph K. E.; Munoz, Cindy M.; Blakley, Scott E.; Truong, Jason T.; Ortega, Elena L.

    2012-01-01

    Regulation of cell growth is paramount to all living organisms. In plants, algae and fungi, regulation of expansive growth of cells is required for development and morphogenesis. Also, many sensory responses of stage IVb sporangiophores of Phycomyces blakesleeanus are produced by regulating elongation growth rate (growth responses) and differential elongation growth rate (tropic responses). “Stiff” mutant sporangiophores exhibit diminished tropic responses and are found to be defective in at least five genes; madD, E, F, G, and J. Prior experimental research suggests that the defective genes affect growth regulation, but this was not verified. All the growth of the single-celled stalk of the stage IVb sporangiophore occurs in a short region termed the “growth zone.” Prior experimental and theoretical research indicates that elongation growth rate of the stage IVb sporangiophore can be regulated by controlling the cell wall mechanical properties within the growth zone and the magnitude of the turgor pressure. A quantitative biophysical model for elongation growth rate is required to elucidate the relationship between wall mechanical properties and turgor pressure during growth regulation. In this study, it is hypothesized that the mechanical properties of the wall within the growth zone of stiff mutant sporangiophores are different compared to wild type (WT). A biophysical equation for elongation growth rate is derived for fungal and plant cells with a growth zone. Two strains of stiff mutants are studied, C149 madD120 (−) and C216 geo- (−). Experimental results demonstrate that turgor pressure is larger but irreversible wall deformation rates within the growth zone and growth zone length are smaller for stiff mutant sporangiophores compared to WT. These findings can explain the diminished tropic responses of the stiff mutant sporangiophores. It is speculated that the defective genes affect the amount of wall-building material delivered to the inner cell

  18. YUCCA Genes Are Expressed in Response to Leaf Adaxial-Abaxial Juxtaposition and Are Required for Leaf Margin Development1[W

    PubMed Central

    Wang, Wei; Xu, Ben; Wang, Hua; Li, Jiqin; Huang, Hai; Xu, Lin

    2011-01-01

    During leaf development, the formation of leaf adaxial-abaxial polarity at the primordium stage is crucial for subsequent leaf expansion. However, little is known about the genetic control from polarity establishment to blade outgrowth. The leaf margin, comprising elongated margin cells and hydathodes, is thought to affect leaf expansion. Here, we show that mutants with defective leaf polarity or with loss of function in the multiple auxin-biosynthetic YUCCA (YUC) genes exhibited a similar abnormal leaf margin and less-expanded leaves. Leaf margins of these mutants contained fewer hydathodes and an increased number of cell patches in which the patterns of epidermal cells resembled those of hydathodes. The previously characterized leaf-abaxialized asymmetric leaves2 (as2) revoluta (rev) and leaf-adaxialized kanadi1 (kan1) kan2 double mutants both produce finger-shaped, hydathode-like protrusions on adaxial and abaxial leaf surfaces, respectively. YUCs are required for formation of the protrusions, as those produced by as2 rev and kan1 kan2 were absent in the yuc1 yuc2 yuc4 triple mutant background. Expressions of YUC1, YUC2, and YUC4 were spatially regulated in the leaf, being associated with hydathodes in wild-type leaves and protrusions on as2 rev and kan1 kan2 leaves. In addition, inhibition of auxin transport by treatment of seedlings with N-(1-naphtyl) phtalamic acid or disruption of the auxin gradient by transforming plants with the 35S:YUC1 construct also blocked leaf margin development. Collectively, our data show that expressions of YUCs in the leaf respond to the adaxial-abaxial juxtaposition, and that the activities of auxin mediate leaf margin development, which subsequently promotes blade outgrowth. PMID:22003085

  19. Safety Zones

    EPA Pesticide Factsheets

    These are established primarily to reduce the accidental spread of hazardous substances by workers or equipment from contaminated areas to clean areas. They include the exclusion (hot) zone, contamination reduction (warm) zone, and support (cold) zone.

  20. Rapid Changes in Cell Wall Yielding of Elongating Begonia argenteo-guttata L. Leaves in Response to Changes in Plant Water Status 1

    PubMed Central

    Serpe, Marcelo D.; Matthews, Mark A.

    1992-01-01

    Elongation and epidermal cell turgor (P) of Begonia argenteoguttata L. leaves were simultaneously measured to determine the wall-yielding behavior of growing leaf cells in response to changes in plant water status. Rapid changes in plant water status were imposed by irrigating the rooting media with solutions of −0.20 and −0.30 MPa mannitol. These treatments caused decreases in P of 0.09 and 0.17 MPa, respectively. The decreases in P were complete within 10 min, and P did not change thereafter. Following treatments, leaf elongation was nil for periods of 25 to 38 min. Subsequently, elongation recovered to steady rates that were 45 or 75% lower than in the well-watered controls. Leaves of plants that were pretreated with −0.30 MPa of mannitol and rewatered showed an increase in P of 0.19 MPa, which was complete within 15 min; P did not change thereafter. Rewatering caused a several-fold increase in leaf elongation rates, which subsequently declined while P was increasing, to reach steady rates similar to that of the controls. Several estimates of elastic deformation indicated that most of the elongation responses to altered P were due to changes in irreversible deformation. The results showed that the initial effects of changes in P on leaf elongation were partially compensated for by changes in the cell wall-yielding properties. We conclude that linear relationships between P and adjusted growth rates are not necessarily indicative of constant wall-yielding properties. Instead, these relationships may reflect the effect of P on wall-loosening processes. PMID:16653208

  1. Rapid Changes in Cell Wall Yielding of Elongating Begonia argenteo-guttata L. Leaves in Response to Changes in Plant Water Status.

    PubMed

    Serpe, M D; Matthews, M A

    1992-12-01

    Elongation and epidermal cell turgor (P) of Begonia argenteoguttata L. leaves were simultaneously measured to determine the wall-yielding behavior of growing leaf cells in response to changes in plant water status. Rapid changes in plant water status were imposed by irrigating the rooting media with solutions of -0.20 and -0.30 MPa mannitol. These treatments caused decreases in P of 0.09 and 0.17 MPa, respectively. The decreases in P were complete within 10 min, and P did not change thereafter. Following treatments, leaf elongation was nil for periods of 25 to 38 min. Subsequently, elongation recovered to steady rates that were 45 or 75% lower than in the well-watered controls. Leaves of plants that were pretreated with -0.30 MPa of mannitol and rewatered showed an increase in P of 0.19 MPa, which was complete within 15 min; P did not change thereafter. Rewatering caused a several-fold increase in leaf elongation rates, which subsequently declined while P was increasing, to reach steady rates similar to that of the controls. Several estimates of elastic deformation indicated that most of the elongation responses to altered P were due to changes in irreversible deformation. The results showed that the initial effects of changes in P on leaf elongation were partially compensated for by changes in the cell wall-yielding properties. We conclude that linear relationships between P and adjusted growth rates are not necessarily indicative of constant wall-yielding properties. Instead, these relationships may reflect the effect of P on wall-loosening processes.

  2. Dimerization of elongator protein 1 is essential for Elongator complex assembly.

    PubMed

    Xu, Huisha; Lin, Zhijie; Li, Fengzhi; Diao, Wentao; Dong, Chunming; Zhou, Hao; Xie, Xingqiao; Wang, Zheng; Shen, Yuequan; Long, Jiafu

    2015-08-25

    The evolutionarily conserved Elongator complex, which is composed of six subunits elongator protein 1 (Elp1 to -6), plays vital roles in gene regulation. The molecular hallmark of familial dysautonomia (FD) is the splicing mutation of Elp1 [also known as IκB kinase complex-associated protein (IKAP)] in the nervous system that is believed to be the primary cause of the devastating symptoms of this disease. Here, we demonstrate that disease-related mutations in Elp1 affect Elongator assembly, and we have determined the structure of the C-terminal portion of human Elp1 (Elp1-CT), which is sufficient for full-length Elp1 dimerization, as well as the structure of the cognate dimerization domain of yeast Elp1 (yElp1-DD). Our study reveals that the formation of the Elp1 dimer contributes to its stability in vitro and in vivo and is required for the assembly of both the human and yeast Elongator complexes. Functional studies suggest that Elp1 dimerization is essential for yeast viability. Collectively, our results identify the evolutionarily conserved dimerization domain of Elp1 and suggest that the pathological mechanisms underlying the onset and progression of Elp1 mutation-related disease may result from impaired Elongator activities.

  3. Dimerization of elongator protein 1 is essential for Elongator complex assembly

    PubMed Central

    Xu, Huisha; Lin, Zhijie; Li, Fengzhi; Diao, Wentao; Dong, Chunming; Zhou, Hao; Xie, Xingqiao; Wang, Zheng; Shen, Yuequan; Long, Jiafu

    2015-01-01

    The evolutionarily conserved Elongator complex, which is composed of six subunits elongator protein 1 (Elp1 to -6), plays vital roles in gene regulation. The molecular hallmark of familial dysautonomia (FD) is the splicing mutation of Elp1 [also known as IκB kinase complex-associated protein (IKAP)] in the nervous system that is believed to be the primary cause of the devastating symptoms of this disease. Here, we demonstrate that disease-related mutations in Elp1 affect Elongator assembly, and we have determined the structure of the C-terminal portion of human Elp1 (Elp1-CT), which is sufficient for full-length Elp1 dimerization, as well as the structure of the cognate dimerization domain of yeast Elp1 (yElp1-DD). Our study reveals that the formation of the Elp1 dimer contributes to its stability in vitro and in vivo and is required for the assembly of both the human and yeast Elongator complexes. Functional studies suggest that Elp1 dimerization is essential for yeast viability. Collectively, our results identify the evolutionarily conserved dimerization domain of Elp1 and suggest that the pathological mechanisms underlying the onset and progression of Elp1 mutation-related disease may result from impaired Elongator activities. PMID:26261306

  4. Genetic variability of oxalate oxidase activity and elongation in water-stressed primary roots of diverse maize and rice lines

    USDA-ARS?s Scientific Manuscript database

    Previous work on maize primary roots under water stress showed that cell elongation is maintained in the apical region of the growth zone but progressively inhibited further from the apex. In association with these responses, several proteins related to reactive oxygen species (ROS) production, part...

  5. Elongated nanostructures for radial junction solar cells.

    PubMed

    Kuang, Yinghuan; Vece, Marcel Di; Rath, Jatindra K; Dijk, Lourens van; Schropp, Ruud E I

    2013-10-01

    In solar cell technology, the current trend is to thin down the active absorber layer. The main advantage of a thinner absorber is primarily the reduced consumption of material and energy during production. For thin film silicon (Si) technology, thinning down the absorber layer is of particular interest since both the device throughput of vacuum deposition systems and the stability of the devices are significantly enhanced. These features lead to lower cost per installed watt peak for solar cells, provided that the (stabilized) efficiency is the same as for thicker devices. However, merely thinning down inevitably leads to a reduced light absorption. Therefore, advanced light trapping schemes are crucial to increase the light path length. The use of elongated nanostructures is a promising method for advanced light trapping. The enhanced optical performance originates from orthogonalization of the light's travel path with respect to the direction of carrier collection due to the radial junction, an improved anti-reflection effect thanks to the three-dimensional geometric configuration and the multiple scattering between individual nanostructures. These advantages potentially allow for high efficiency at a significantly reduced quantity and even at a reduced material quality, of the semiconductor material. In this article, several types of elongated nanostructures with the high potential to improve the device performance are reviewed. First, we briefly introduce the conventional solar cells with emphasis on thin film technology, following the most commonly used fabrication techniques for creating nanostructures with a high aspect ratio. Subsequently, several representative applications of elongated nanostructures, such as Si nanowires in realistic photovoltaic (PV) devices, are reviewed. Finally, the scientific challenges and an outlook for nanostructured PV devices are presented.

  6. Elongated nanostructures for radial junction solar cells

    NASA Astrophysics Data System (ADS)

    Kuang, Yinghuan; Di Vece, Marcel; Rath, Jatindra K.; van Dijk, Lourens; Schropp, Ruud E. I.

    2013-10-01

    In solar cell technology, the current trend is to thin down the active absorber layer. The main advantage of a thinner absorber is primarily the reduced consumption of material and energy during production. For thin film silicon (Si) technology, thinning down the absorber layer is of particular interest since both the device throughput of vacuum deposition systems and the stability of the devices are significantly enhanced. These features lead to lower cost per installed watt peak for solar cells, provided that the (stabilized) efficiency is the same as for thicker devices. However, merely thinning down inevitably leads to a reduced light absorption. Therefore, advanced light trapping schemes are crucial to increase the light path length. The use of elongated nanostructures is a promising method for advanced light trapping. The enhanced optical performance originates from orthogonalization of the light's travel path with respect to the direction of carrier collection due to the radial junction, an improved anti-reflection effect thanks to the three-dimensional geometric configuration and the multiple scattering between individual nanostructures. These advantages potentially allow for high efficiency at a significantly reduced quantity and even at a reduced material quality, of the semiconductor material. In this article, several types of elongated nanostructures with the high potential to improve the device performance are reviewed. First, we briefly introduce the conventional solar cells with emphasis on thin film technology, following the most commonly used fabrication techniques for creating nanostructures with a high aspect ratio. Subsequently, several representative applications of elongated nanostructures, such as Si nanowires in realistic photovoltaic (PV) devices, are reviewed. Finally, the scientific challenges and an outlook for nanostructured PV devices are presented.

  7. Cell division versus cell elongation: the control of radicle elongation during thermoinhibition of Tagetes minuta achenes.

    PubMed

    Taylor, Nicky J; Hills, Paul N; van Staden, Johannes

    2007-12-01

    Endogenous embryo factors, which act mainly in the radicle, prevent germination in Tagetes minuta at high temperatures. These factors act to prevent cell elongation, which is critical for radicle protrusion under optimal conditions. Once the radicle has emerged both cell elongation and cell division are required for post-germination growth. Germination can be induced at high temperatures by fusicoccin, which rapidly stimulates cell elongation. In addition, priming seeds at 25 degrees C on polyethylene glycol (PEG) 6000 and mannitol could also induce germination on water at 36 degrees C, indicating that priming prevents radicle protrusion at a point subsequent to the point of control in thermoinhibited achenes. Flow cytometry studies revealed that DNA synthesis occurs during thermoinhibition and the inhibition of DNA synthesis during this process inhibits subsequent germination on water under optimal conditions, suggesting a protective role for DNA synthesis in thermoinhibited achenes of T. minuta.

  8. Plasma column changes at small solar elongations

    NASA Technical Reports Server (NTRS)

    Callahan, P. S.

    1973-01-01

    The differenced range versus integrated Doppler (DRVID) technique was used to study charged particle changes in the ray path between earth and Mariner 9. For plasma activity near the sun, DRVID data were obtained from August 10 to October 24, 1972, surrounding the Mariner 9 superior conjunction on September 7. If the records are viewed in terms of range change or range change rate, the day-to-day fluctuations in these quantities mask the changes expected due to the varying solar elongation. Thus, while the steady-state total electron content varies by a factor of 4, the columnar content changes show no systematic variations.

  9. Nonlinear deformations of microcapsules in elongation flow

    NASA Astrophysics Data System (ADS)

    Deschamps, Julien; de Loubens, Clément; Boedec, Gwenn; Georgelin, Marc; Leonetti, Marc; Soft Matter; Biophysics Group Team

    2014-11-01

    Soft microcapsules are drops bounded by a thin elastic shell made of cross-linked proteins. They have numerous applications for drug delivery in bioengineering, pharmaceutics and medicine, where their mechanical stability and their dynamics under flow are crucial. They can also be used as red blood cells models. Here, we investigate the mechanical behaviour of microcapsules made of albumine in strong elongational flow, up to a stretching of 180% just before breaking. The set-up allows us to visualize the deformed shape in the two perpendicular main fields of view, to manage high capillary number and to manipulate soft microcapsules. The steady-state shape of a capsule in the planar elongational flow is non-axisymmetric. In each cross section, the shape is an ellipse but with different small axis which vary in opposite sense with the stretching. Whatever the degree of cross-linking and the size of the capsules, the deformations followed the same master-curve. Comparisons between numerical predictions and experimental results permit to conclude unambiguously that the more properly strain-energy model of membrane is the generalized Hooke model.

  10. Functional specialization of transcription elongation factors

    PubMed Central

    Belogurov, Georgiy A; Mooney, Rachel A; Svetlov, Vladimir; Landick, Robert; Artsimovitch, Irina

    2009-01-01

    Elongation factors NusG and RfaH evolved from a common ancestor and utilize the same binding site on RNA polymerase (RNAP) to modulate transcription. However, although NusG associates with RNAP transcribing most Escherichia coli genes, RfaH regulates just a few operons containing ops, a DNA sequence that mediates RfaH recruitment. Here, we describe the mechanism by which this specificity is maintained. We observe that RfaH action is indeed restricted to those several operons that are devoid of NusG in vivo. We also show that RfaH and NusG compete for their effects on transcript elongation and termination in vitro. Our data argue that RfaH recognizes its DNA target even in the presence of NusG. Once recruited, RfaH remains stably associated with RNAP, thereby precluding NusG binding. We envision a pathway by which a specialized regulator has evolved in the background of its ubiquitous paralogue. We propose that RfaH and NusG may have opposite regulatory functions: although NusG appears to function in concert with Rho, RfaH inhibits Rho action and activates the expression of poorly translated, frequently foreign genes. PMID:19096362

  11. Characterization of pollutant dispersion near elongated ...

    EPA Pesticide Factsheets

    This paper presents a wind tunnel study of the effects of elongated rectangular buildings on the dispersion of pollutants from nearby stacks. The study examines the influence of source location, building aspect ratio, and wind direction on pollutant dispersion with the goal of developing improved algorithms within dispersion models. The paper also examines the current AERMOD/PRIME modeling capabilities compared to wind tunnel observations. Differences in the amount of plume material entrained in the wake region downwind of a building for various source locations and source heights are illustrated with vertical and lateral concentration profiles. These profiles were parameterized using the Gaussian equation and show the influence of building/source configurations on those parameters. When the building is oriented at 45° to the approach flow, for example, the effective plume height descends more rapidly than it does for a perpendicular building, enhancing the resulting surface concentrations in the wake region. Buildings at angles to the wind cause a cross-wind shift in the location of the plume resulting from a lateral mean flow established in the building wake. These and other effects that are not well represented in many dispersion models are important considerations when developing improved algorithms to estimate the location and magnitude of concentrations downwind of elongated buildings. The National Exposure Research Laboratory (NERL) Computational Exposur

  12. A size-mediated effect can compensate for transient chilling stress affecting maize (Zea mays) leaf extension.

    PubMed

    Louarn, Gaëtan; Andrieu, Bruno; Giauffret, Catherine

    2010-07-01

    *In this study, we examined the impact of transient chilling in maize (Zea mays). We investigated the respective roles of the direct effects of stressing temperatures and indirect whorl size-mediated effects on the growth of leaves chilled at various stages of development. *Cell production, individual leaf extension and final leaf size of plants grown in a glasshouse under three temperature regimes (a control and two short chilling transfers) were studied using two genotypes contrasting in terms of their architecture. *The kinetics of all the leaves emerging after the stress were affected, but not all final leaf lengths were affected. No size-mediated propagation of an initial growth reduction was observed, but a size-mediated effect was associated with a longer duration of leaf elongation which compensated for reduced leaf elongation rates when leaves were stressed during their early growth. Both cell division and cell expansion contributed to explaining cold-induced responses at the leaf level. *These results demonstrate that leaf elongation kinetics and final leaf length are under the control of processes at the n - 1 (cell proliferation and expansion) and n + 1 (whorl size signal) scales. Both levels may respond to chilling stress with different time lags, making it possible to buffer short-term responses.

  13. Purification and characterization of the human elongator complex.

    PubMed

    Hawkes, Nicola A; Otero, Gabriel; Winkler, G Sebastiaan; Marshall, Nick; Dahmus, Michael E; Krappmann, Daniel; Scheidereit, Claus; Thomas, Claire L; Schiavo, Giampietro; Erdjument-Bromage, Hediye; Tempst, Paul; Svejstrup, Jesper Q

    2002-01-25

    Human Elongator complex was purified to virtual homogeneity from HeLa cell extracts. The purified factor can exist in two forms: a six-subunit complex, holo-Elongator, which has histone acetyltransferase activity directed against histone H3 and H4, and a three-subunit core form, which does not have histone acetyltransferase activity despite containing the catalytic Elp3 subunit. Elongator is a component of early elongation complexes formed in HeLa nuclear extracts and can interact directly with RNA polymerase II in solution. Several human homologues of the yeast Elongator subunits were identified as subunits of the human Elongator complex, including StIP1 (STAT-interacting protein 1) and IKAP (IKK complex-associated protein). Mutations in IKAP can result in the severe human disorder familial dysautonomia, raising the possibility that this disease might be due to compromised Elongator function and therefore could be a transcription disorder.

  14. Impact of plant shoot architecture on leaf cooling: a coupled heat and mass transfer model

    PubMed Central

    Bridge, L. J.; Franklin, K. A.; Homer, M. E.

    2013-01-01

    Plants display a range of striking architectural adaptations when grown at elevated temperatures. In the model plant Arabidopsis thaliana, these include elongation of petioles, and increased petiole and leaf angles from the soil surface. The potential physiological significance of these architectural changes remains speculative. We address this issue computationally by formulating a mathematical model and performing numerical simulations, testing the hypothesis that elongated and elevated plant configurations may reflect a leaf-cooling strategy. This sets in place a new basic model of plant water use and interaction with the surrounding air, which couples heat and mass transfer within a plant to water vapour diffusion in the air, using a transpiration term that depends on saturation, temperature and vapour concentration. A two-dimensional, multi-petiole shoot geometry is considered, with added leaf-blade shape detail. Our simulations show that increased petiole length and angle generally result in enhanced transpiration rates and reduced leaf temperatures in well-watered conditions. Furthermore, our computations also reveal plant configurations for which elongation may result in decreased transpiration rate owing to decreased leaf liquid saturation. We offer further qualitative and quantitative insights into the role of architectural parameters as key determinants of leaf-cooling capacity. PMID:23720538

  15. Brassinosteroid Regulates Cell Elongation by Modulating Gibberellin Metabolism in Rice[C][W][OPEN

    PubMed Central

    Tong, Hongning; Xiao, Yunhua; Liu, Dapu; Gao, Shaopei; Liu, Linchuan; Yin, Yanhai; Jin, Yun; Qian, Qian; Chu, Chengcai

    2014-01-01

    Brassinosteroid (BR) and gibberellin (GA) are two predominant hormones regulating plant cell elongation. A defect in either of these leads to reduced plant growth and dwarfism. However, their relationship remains unknown in rice (Oryza sativa). Here, we demonstrated that BR regulates cell elongation by modulating GA metabolism in rice. Under physiological conditions, BR promotes GA accumulation by regulating the expression of GA metabolic genes to stimulate cell elongation. BR greatly induces the expression of D18/GA3ox-2, one of the GA biosynthetic genes, leading to increased GA1 levels, the bioactive GA in rice seedlings. Consequently, both d18 and loss-of-function GA-signaling mutants have decreased BR sensitivity. When excessive active BR is applied, the hormone mostly induces GA inactivation through upregulation of the GA inactivation gene GA2ox-3 and also represses BR biosynthesis, resulting in decreased hormone levels and growth inhibition. As a feedback mechanism, GA extensively inhibits BR biosynthesis and the BR response. GA treatment decreases the enlarged leaf angles in plants with enhanced BR biosynthesis or signaling. Our results revealed a previously unknown mechanism underlying BR and GA crosstalk depending on tissues and hormone levels, which greatly advances our understanding of hormone actions in crop plants and appears much different from that in Arabidopsis thaliana. PMID:25371548

  16. Mechanical modelling quantifies the functional importance of outer tissue layers during root elongation and bending

    PubMed Central

    Dyson, Rosemary J; Vizcay-Barrena, Gema; Band, Leah R; Fernandes, Anwesha N; French, Andrew P; Fozard, John A; Hodgman, T Charlie; Kenobi, Kim; Pridmore, Tony P; Stout, Michael; Wells, Darren M; Wilson, Michael H; Bennett, Malcolm J; Jensen, Oliver E

    2014-01-01

    Root elongation and bending require the coordinated expansion of multiple cells of different types. These processes are regulated by the action of hormones that can target distinct cell layers. We use a mathematical model to characterise the influence of the biomechanical properties of individual cell walls on the properties of the whole tissue. Taking a simple constitutive model at the cell scale which characterises cell walls via yield and extensibility parameters, we derive the analogous tissue-level model to describe elongation and bending. To accurately parameterise the model, we take detailed measurements of cell turgor, cell geometries and wall thicknesses. The model demonstrates how cell properties and shapes contribute to tissue-level extensibility and yield. Exploiting the highly organised structure of the elongation zone (EZ) of the Arabidopsis root, we quantify the contributions of different cell layers, using the measured parameters. We show how distributions of material and geometric properties across the root cross-section contribute to the generation of curvature, and relate the angle of a gravitropic bend to the magnitude and duration of asymmetric wall softening. We quantify the geometric factors which lead to the predominant contribution of the outer cell files in driving root elongation and bending. PMID:24641449

  17. Elongate and Radial Hummocky Tracts in Southern Sweden - Evidence for Extensive Subglacial Drainage?

    NASA Astrophysics Data System (ADS)

    Peterson, Gustaf; Johnson, Mark D.

    2016-04-01

    Complete understanding of glacial melt-water processes is crucial for a profound view on former and contemporary ice sheets. Investigating sediments and landforms below ice sheets is complicated; however, formerly glaciated regions are easily accessible. For over a century, the hummocky characteristics of the South Swedish Uplands (SSU) have been recognized, and several explanations have been proposed since. Most of these studies describe hummocks shown to be products of a stagnant ice environment. The arrival of detailed elevation models (LiDAR) has revealed this landscape in an unprecedented detail. We have made an inventory of glacial landforms on detailed DEMs covering SSU, and can present a more diverse view of the hummocky tracts. In the field we have investigated the sedimentology and stratigraphy in machine dug sections. It is possible to manually distinguish at least four different hummocky tracts: I) Ribbed moraine, II) Dead ice moraine, III) An enigmatic landform type with a fish scale pattern, and IV) Hummocky tracts in elongate zones. This abstract will focus on the last type (IV). The four most striking morphological characteristics are: First, there are distinct elongate zones of hummocks with a radial pattern with distinct borders to the surrounding lineated till plains. Second, the hummocky zones in some places show an anastamosing pattern. Third, in analyzing these elongate zones, it is clear that they do not follow regional lows but instead runs over highlands. Fourth, in these zones there are localities with eskers superposed on hummocks. Sedimentological excavations yield a compact sandy silty till. Fabric measurements are not very strong; however, they are sub-parallel to lineations on nearby upland till surfaces. Taken together, these observations can possibly explain the elongate hummocky zones invoking processes of subglacial meltwater eroding hummocks in the bottom of tunnel valleys. A large amount of subglacial meltwater is controversial

  18. Leaf Size in Swietenia

    Treesearch

    Charles B. Briscoe; F. Bruce. Lamb

    1962-01-01

    A study was made of the putative hybrid of bigleaf and small-leaf mahoganies. Initial measurements indicated that bigleaf mahogany can be distinguished from small-leaf mahogany by gross measurements of leaflets. Isolated mother trees yield typical progeny. Typical mother trees in mixed stands yield like progeny plus, usually, mediumleaf progeny. Mediumleaf mother trees...

  19. Gravity-induced changes in intracellular potentials in elongating cortical cells of mung bean roots

    NASA Technical Reports Server (NTRS)

    Ishikawa, H.; Evans, M. L.

    1990-01-01

    Gravity-induced changes in intracellular potentials in primary roots of 2-day-old mung bean (Vigna mungo L. cv. black matpe) seedlings were investigated using glass microelectrodes held by 3-dimensional hydraulic micro-drives. The electrodes were inserted into outer cortical cells within the elongation zone. Intracellular potentials, angle of root orientation with respect to gravity, and position within the root of the impaled cortical cell were measured simultaneously. Gravistimulation caused intracellular potential changes in cortical cells of the elongation zone. When the roots were oriented vertically, the intracellular potentials of the outer cortical cells (2 mm behind the root apex) were approximately - 115 mV. When the roots were placed horizontally cortical cells on the upper side hyperpolarized to - 154 mV within 30 s while cortical cells on the lower side depolarized to about - 62 mV. This electrical asymmetry did not occur in cells of the maturation zone. Because attempts to insert the electrode into cells of the root cap were unsuccessful, these cells were not measured. The hyperpolarization of cortical cells on the upper side was greatly reduced upon application of N,N'-dicyclohexylcarbodiimide (DCCD), an inhibitor of respiratory energy coupling. When stimulated roots were returned to the vertical, the degree of hyperpolarization of cortical cells on the previous upper side decreased within 30 s and approached that of cortical cells in non-stimulated roots. This cycle of hyperpolarization/loss of hyperpolarization was repeatable at least ten times by alternately turning the root from the vertical to the horizontal and back again. The very short (<30 s) lag period of these electrical changes indicates that they may result from stimulus-perception and transduction within the elongation zone rather than from transmission of a signal from the root cap.

  20. Potential flow about elongated bodies of revolution

    NASA Technical Reports Server (NTRS)

    Kaplan, Carl

    1936-01-01

    This report presents a method of solving the problem of axial and transverse potential flows around arbitrary elongated bodies of revolution. The solutions of Laplace's equation for the velocity potentials of the axial and transverse flows, the system of coordinates being an elliptic one in a meridian plane, are given. The theory is applied to a body of revolution obtained from a symmetrical Joukowsky profile, a shape resembling an airship hull. The pressure distribution and the transverse-force distribution are calculated and serve as examples of the procedure to be followed in the case of an actual airship. A section on the determination of inertia coefficients is also included in which the validity of some earlier work is questioned.

  1. The Astoria Fan: An elongate type fan

    USGS Publications Warehouse

    Nelson, C.H.

    1984-01-01

    The Astoria Fan, a modern system, is located on a subducting oceanic crust and fills a north-south-trending trench along the Oregon continental margin. Well-developed channels cross the entire fan length; they display classic inner-fan leveed profiles but evolve into distributaries in the midfan area where the gradient decreases sharply. During periods of low sea level, inner- and middle-fan channels funnel sand to distal depositional sites in the outer-fan area where the sand/shale ratios are highest. This pattern of sand displacement and efficiency of transport appears to be characteristic of elongate fans fed by a major river and submarine canyon. ?? 1984 Springer-Verlag New York Inc.

  2. [Influence of photosynthetic parameters on leaf longevity].

    PubMed

    Vasfilov, S P

    2015-01-01

    Higher plants show a wide range of leaf lifespan (LL) variability. LL is calculated as a sum of functional LL(f) (corresponding to the time of active photosynthesis and CO2 accumulation in the leaf) and nonfunctional LL(n) (the time of photosynthetic activity absence). For evergreen species of boreal zones, LL(n) corresponds to the period of winter rest. Photosynthetic potential of leaf (PPL), interpreted as the maximum possible amount of CO2 that can be fixed during its life, can be estimated on the basis of maximum photosynthesis rate (P(a)) dynamics during LL(f); the maximum (P(a max)) being achieved in mature leaf. Photosynthetic potential depends on LL(f) more strongly than on P(a max). The PPL/LL(f) ratio is indicative of the rate of PPL realization over leaf lifespan. As LL(f) shows strong positive correlation with LL, the latter parameter can also characterize the rate of PPL realization. Long LL(f) in evergreen species provides higher PPL, which is advantageous by comparison with deciduous ones. In evergreen species, the PPL itself is realized slower than in deciduous ones. The increase in LL(f) and LL is accompanied by the increase in leaf constructional cost (LCC(a)) as well as the decrease in photosynthesis rate. At that, photosynthesis rate per unit of dry weight (P(m)) decreases much faster than that per unit of leaf area (P(a)). Apparently, when considering dry leaf weight, the apoplast share seems to be much higher in long-living leaves of evergreen species than in short-living leaves of deciduous species. The leaf payback (LP) may be stabilized by unidirectional shifts in PPL and LCC(a). Species with short/long LL(f) and high/low PPL realization rate are typical for early/late succession stages and for habitats with the environmental conditions favorable/adverse for photosynthesis and growth. If the conditions for photosynthesis and growth are favorable, high PPL realization rate provides advantage in competition. The PPL realization rate is

  3. Boron deficiency inhibits root cell elongation via an ethylene/auxin/ROS-dependent pathway in Arabidopsis seedlings

    PubMed Central

    Camacho-Cristóbal, Juan J.; Martín-Rejano, Esperanza M.; Herrera-Rodríguez, M. Begoña; Navarro-Gochicoa, M. Teresa; Rexach, Jesús; González-Fontes, Agustín

    2015-01-01

    One of the earliest symptoms of boron (B) deficiency is the inhibition of root elongation which can reasonably be attributed to the damaging effects of B deprivation on cell wall integrity. It is shown here that exposure of wild-type Arabidopsis thaliana seedlings to B deficiency for 4h led to a drastic inhibition of root cell length in the transition between the elongation and differentiation zones. To investigate the possible mediation of ethylene, auxin, and reactive oxygen species (ROS) in the effect of B deficiency on root cell elongation, B deficiency was applied together with aminoethoxyvinylglycine (AVG, a chemical inhibitor of ethylene biosynthesis), silver ions (Ag+, an antagonist of ethylene perception), α-(phenylethyl-2‐oxo)‐indoleacetic acid (PEO-IAA, a synthetic antagonist of TIR1 receptor function), and diphenylene iodonium (DPI, an inhibitor of ROS production). Interestingly, all these chemicals partially or fully restored cell elongation in B-deficient roots. To further explore the possible role of ethylene and auxin in the inhibition of root cell elongation under B deficiency, a genetic approach was performed by using Arabidopsis mutants defective in the ethylene (ein2‐1) or auxin (eir1-4 and aux1-22) response. Root cell elongation in these mutants was less sensitive to B-deficient treatment than that in wild-type plants. Altogether, these results demonstrated that a signalling pathway involving ethylene, auxin, and ROS participates in the reduction of root cell elongation when Arabidopsis seedlings are subjected to B deficiency. A similar signalling process has been described to reduce root elongation rapidly under various types of cell wall stress which supports the idea that this signalling pathway is triggered by the impaired cell wall integrity caused by B deficiency. PMID:25922480

  4. Boron deficiency inhibits root cell elongation via an ethylene/auxin/ROS-dependent pathway in Arabidopsis seedlings.

    PubMed

    Camacho-Cristóbal, Juan J; Martín-Rejano, Esperanza M; Herrera-Rodríguez, M Begoña; Navarro-Gochicoa, M Teresa; Rexach, Jesús; González-Fontes, Agustín

    2015-07-01

    One of the earliest symptoms of boron (B) deficiency is the inhibition of root elongation which can reasonably be attributed to the damaging effects of B deprivation on cell wall integrity. It is shown here that exposure of wild-type Arabidopsis thaliana seedlings to B deficiency for 4h led to a drastic inhibition of root cell length in the transition between the elongation and differentiation zones. To investigate the possible mediation of ethylene, auxin, and reactive oxygen species (ROS) in the effect of B deficiency on root cell elongation, B deficiency was applied together with aminoethoxyvinylglycine (AVG, a chemical inhibitor of ethylene biosynthesis), silver ions (Ag(+), an antagonist of ethylene perception), α-(phenylethyl-2-oxo)-indoleacetic acid (PEO-IAA, a synthetic antagonist of TIR1 receptor function), and diphenylene iodonium (DPI, an inhibitor of ROS production). Interestingly, all these chemicals partially or fully restored cell elongation in B-deficient roots. To further explore the possible role of ethylene and auxin in the inhibition of root cell elongation under B deficiency, a genetic approach was performed by using Arabidopsis mutants defective in the ethylene (ein2-1) or auxin (eir1-4 and aux1-22) response. Root cell elongation in these mutants was less sensitive to B-deficient treatment than that in wild-type plants. Altogether, these results demonstrated that a signalling pathway involving ethylene, auxin, and ROS participates in the reduction of root cell elongation when Arabidopsis seedlings are subjected to B deficiency. A similar signalling process has been described to reduce root elongation rapidly under various types of cell wall stress which supports the idea that this signalling pathway is triggered by the impaired cell wall integrity caused by B deficiency. © The Author 2015. Published by Oxford University Press on behalf of the Society for Experimental Biology.

  5. First Report of Fusarium subglutinans Causing Leaf Spot Disease on Cymbidium Orchids in Korea.

    PubMed

    Han, Kyung-Sook; Park, Jong-Han; Back, Chang-Gi; Park, Mi-Jeong

    2015-09-01

    In 2006~2010, leaf spot symptoms, that is, small, yellow spots that turned into dark brown-to-black lesions surrounded by a yellow halo, were observed on Cymbidium spp. in Gongju, Taean, and Gapyeong in Korea. A Fusarium species was continuously isolated from symptomatic leaves; in pathogenicity testing, isolates caused leaf spot symptoms consisting of sunken, dark brown lesions similar to the original ones. The causal pathogen was identified as Fusarium subglutinans based on morphological and translation elongation factor 1-alpha sequence analyses. This is the first report of F. subglutinans as the cause of leaf spot disease in Cymbidium spp. in Korea.

  6. First Report of Fusarium subglutinans Causing Leaf Spot Disease on Cymbidium Orchids in Korea

    PubMed Central

    Han, Kyung-Sook; Park, Jong-Han; Back, Chang-Gi

    2015-01-01

    In 2006~2010, leaf spot symptoms, that is, small, yellow spots that turned into dark brown-to-black lesions surrounded by a yellow halo, were observed on Cymbidium spp. in Gongju, Taean, and Gapyeong in Korea. A Fusarium species was continuously isolated from symptomatic leaves; in pathogenicity testing, isolates caused leaf spot symptoms consisting of sunken, dark brown lesions similar to the original ones. The causal pathogen was identified as Fusarium subglutinans based on morphological and translation elongation factor 1-alpha sequence analyses. This is the first report of F. subglutinans as the cause of leaf spot disease in Cymbidium spp. in Korea. PMID:26539053

  7. Lignification in rapidly elongating internodes of deep water rice as a limiting factor in growth

    SciTech Connect

    Sauter, M.; Kende, H. )

    1990-05-01

    Internodes of deep water rice are induced to elongate rapidly by partial submergence, or by treatment with ethylene or gibberellin. This growth response is based, in part, on enhanced cell elongation and an increase in the size of the internodal growing zone. For this to occur, processes that limit growth, e.g. lignification, must be delayed. We examined the activity and distribution of two enzymes of the lignin biosynthetic pathway, phenylalanine ammonia-lyase (PAL) and coniferylalcohol dehydrogenase (CAD) in rapidly growing and control internodes. CAD activity decreased in the rapidly growing region of submerged or gibberellin-treated internodes to about 25% of the activity found in air-grown control internodes. No comparable change in CAD activity was observed in the older, non-growing portions of the internodes. PAL activity changed in similar fashion upon induction of rapid growth.

  8. Shaping organs by a wingless-int/Notch/nonmuscle myosin module which orients feather bud elongation

    PubMed Central

    Li, Ang; Chen, Meng; Jiang, Ting-Xin; Wu, Ping; Nie, Qing; Widelitz, Randall; Chuong, Cheng-Ming

    2013-01-01

    How organs are shaped to specific forms is a fundamental issue in developmental biology. To address this question, we used the repetitive, periodic pattern of feather morphogenesis on chicken skin as a model. Avian feathers within a single tract extend from dome-shaped primordia to thin conical structures with a common axis of orientation. From a systems biology perspective, the process is precise and robust. Using tissue transplantation assays, we demonstrate that a “zone of polarizing activity,” localized in the posterior feather bud, is necessary and sufficient to mediate the directional elongation. This region contains a spatially well-defined nuclear β-catenin zone, which is induced by wingless-int (Wnt)7a protein diffusing in from posterior bud epithelium. Misexpressing nuclear β-catenin randomizes feather polarity. This dermal nuclear β-catenin zone, surrounded by Notch1 positive dermal cells, induces Jagged1. Inhibition of Notch signaling disrupts the spatial configuration of the nuclear β-catenin zone and leads to randomized feather polarity. Mathematical modeling predicts that lateral inhibition, mediated by Notch signaling, functions to reduce Wnt7a gradient variations and fluctuations to form the sharp boundary observed for the dermal β-catenin zone. This zone is also enriched for nonmuscle myosin IIB. Suppressing nonmuscle myosin IIB disrupts directional cell rearrangements and abolishes feather bud elongation. These data suggest that a unique molecular module involving chemical–mechanical coupling converts a pliable chemical gradient to a precise domain, ready for subsequent mechanical action, thus defining the position, boundary, and duration of localized morphogenetic activity that molds the shape of growing organs. PMID:23576731

  9. The effect of glyphosate on import into a sink leaf of sugar beet

    SciTech Connect

    Shieh, Wenjang; Geiger, D.R. )

    1990-05-01

    The basis for glyphosate inducted limitation of carbon import into developing leaves was studied in sugar beet. To separate the effects of the herbicide on export from those on import, glyphosate was supplied to a developing leaf from two exporting source leaves which fed the sink leaf. Carbon import into the sink leaf was determined by supplying {sup 14}CO{sub 2} to a third source leaf which also supplies carbon to the monitored sink leaf. Import into the sink leaf decreased within 2 to 3 h after glyphosate application, even though photosynthesis and export in the source leaf supplying {sup 14}C were unaffected. Reduced import into the sink leaf was accompanied by increased import by the tap root. Elongation of the sink leaf was only slightly decreased following arrival of glyphosate. Photosynthesis by the sink leaf was not inhibited. The results to data support the view that import is slowed by the inhibition of synthesis of structural or storage compounds in the developing leaves.

  10. Structures and Activities of the Elongator Complex and Its Cofactors.

    PubMed

    Kolaj-Robin, Olga; Séraphin, Bertrand

    2017-01-01

    Elongator is a highly conserved eukaryotic protein complex consisting of two sets of six Elp proteins, while homologues of its catalytic subunit Elp3 are found in all the kingdoms of life. Although it was originally described as a transcription elongation factor, cumulating evidence suggests that its primary function is catalyzing tRNA modifications. In humans, defects in Elongator subunits are associated with neurological disorders and cancer. Although further studies are still required, a clearer picture of the molecular mechanism of action of Elongator and its cofactors has started to emerge within recent years that have witnessed significant development in the field. In this review we summarize recent Elongator-related findings provided largely by crystal structures of several subunits of the complex, the electron microscopy structure of the entire yeast holoenzyme, as well as the structure of the Elongator cofactor complex Kti11/Kti13. © 2017 Elsevier Inc. All rights reserved.

  11. Cotranslational response to proteotoxic stress by elongation pausing of ribosomes.

    PubMed

    Liu, Botao; Han, Yan; Qian, Shu-Bing

    2013-02-07

    Translational control permits cells to respond swiftly to a changing environment. Rapid attenuation of global protein synthesis under stress conditions has been largely ascribed to the inhibition of translation initiation. Here we report that intracellular proteotoxic stress reduces global protein synthesis by halting ribosomes on transcripts during elongation. Deep sequencing of ribosome-protected messenger RNA (mRNA) fragments reveals an early elongation pausing, roughly at the site where nascent polypeptide chains emerge from the ribosomal exit tunnel. Inhibiting endogenous chaperone molecules by a dominant-negative mutant or chemical inhibitors recapitulates the early elongation pausing, suggesting a dual role of molecular chaperones in facilitating polypeptide elongation and cotranslational folding. Our results further support the chaperone "trapping" mechanism in promoting the passage of nascent chains. Our study reveals that translating ribosomes fine tune the elongation rate by sensing the intracellular folding environment. The early elongation pausing represents a cotranslational stress response to maintain the intracellular protein homeostasis.

  12. Somaclonal variation in hybrid poplars for resistance to Septoria leaf spot

    Treesearch

    M.E. Ostry; D. D. Skilling

    1987-01-01

    Tissue culture techniques have been used to obtain hybrid poplars with putative resistance to leaf spot caused by Septoria musiva from clones previously susceptible to the disease. Stem internode explants were used to obtain proliferating callus cultures. Adventitious bud formation and shoot proliferation were then induced. Elongated shoots were excised and rooted in a...

  13. Molecular phylogenetic relationships of the brown leaf rust fungi on wheat, rye and other grasses

    USDA-ARS?s Scientific Manuscript database

    Phylogenetic analyses were conducted with DNA sequence data from the rDNA internal transcribed spacer region and elongation factor 1–alpha to elucidate the species complex of brown leaf rust fungi infecting wheat, rye and other grasses. Three phylogenetic lineages were recovered within the complex o...

  14. Zone lines

    Treesearch

    Kevin T. Smith

    2001-01-01

    Zone lines are narrow, usually dark markings formed in decaying wood. Zone lines are found most frequently in advanced white rot of hardwoods, although they occasionally are associated both with brown rot and with softwoods.

  15. Runaway telomere elongation caused by telomerase RNA gene mutations.

    PubMed

    McEachern, M J; Blackburn, E H

    1995-08-03

    The ribonucleoprotein enzyme telomerase adds telomeric DNA onto chromosome ends and is normally regulated so that telomeric DNA lengths are kept within defined bounds. In the telomerase RNA gene from the yeast Kluyveromyces lactis, specific mutations that alter telomeric DNA sequences result in telomeres elongating to up to 100 times their normal length and impair cell growth. Some mutations cause immediate elongation whereas others behave like genetic time bombs, causing elongation only after a latent period of hundreds of generations.

  16. Ethylene Inhibits Root Elongation during Alkaline Stress through AUXIN1 and Associated Changes in Auxin Accumulation.

    PubMed

    Li, Juan; Xu, Heng-Hao; Liu, Wen-Cheng; Zhang, Xiao-Wei; Lu, Ying-Tang

    2015-08-01

    Soil alkalinity causes major reductions in yield and quality of crops worldwide. The plant root is the first organ sensing soil alkalinity, which results in shorter primary roots. However, the mechanism underlying alkaline stress-mediated inhibition of root elongation remains to be further elucidated. Here, we report that alkaline conditions inhibit primary root elongation of Arabidopsis (Arabidopsis thaliana) seedlings by reducing cell division potential in the meristem zones and that ethylene signaling affects this process. The ethylene perception antagonist silver (Ag(+)) alleviated the inhibition of root elongation by alkaline stress. Moreover, the ethylene signaling mutants ethylene response1-3 (etr1-3), ethylene insensitive2 (ein2), and ein3-1 showed less reduction in root length under alkaline conditions, indicating a reduced sensitivity to alkalinity. Ethylene biosynthesis also was found to play a role in alkaline stress-mediated root inhibition; the ethylene overproducer1-1 mutant, which overproduces ethylene because of increased stability of 1-AMINOCYCLOPROPANE-1-CARBOXYLIC ACID SYNTHASE5, was hypersensitive to alkaline stress. In addition, the ethylene biosynthesis inhibitor cobalt (Co(2+)) suppressed alkaline stress-mediated inhibition of root elongation. We further found that alkaline stress caused an increase in auxin levels by promoting expression of auxin biosynthesis-related genes, but the increase in auxin levels was reduced in the roots of the etr1-3 and ein3-1 mutants and in Ag(+)/Co(2+)-treated wild-type plants. Additional genetic and physiological data showed that AUXIN1 (AUX1) was involved in alkaline stress-mediated inhibition of root elongation. Taken together, our results reveal that ethylene modulates alkaline stress-mediated inhibition of root growth by increasing auxin accumulation by stimulating the expression of AUX1 and auxin biosynthesis-related genes.

  17. Light-Induced Indeterminacy Alters Shade-Avoiding Tomato Leaf Morphology.

    PubMed

    Chitwood, Daniel H; Kumar, Ravi; Ranjan, Aashish; Pelletier, Julie M; Townsley, Brad T; Ichihashi, Yasunori; Martinez, Ciera C; Zumstein, Kristina; Harada, John J; Maloof, Julin N; Sinha, Neelima R

    2015-11-01

    Plants sense the foliar shade of competitors and alter their developmental programs through the shade-avoidance response. Internode and petiole elongation, and changes in overall leaf area and leaf mass per area, are the stereotypical architectural responses to foliar shade in the shoot. However, changes in leaf shape and complexity in response to shade remain incompletely, and qualitatively, described. Using a meta-analysis of more than 18,000 previously published leaflet outlines, we demonstrate that shade avoidance alters leaf shape in domesticated tomato (Solanum lycopersicum) and wild relatives. The effects of shade avoidance on leaf shape are subtle with respect to individual traits but are combinatorially strong. We then seek to describe the developmental origins of shade-induced changes in leaf shape by swapping plants between light treatments. Leaf size is light responsive late into development, but patterning events, such as stomatal index, are irrevocably specified earlier. Observing that shade induces increases in shoot apical meristem size, we then describe gene expression changes in early leaf primordia and the meristem using laser microdissection. We find that in leaf primordia, shade avoidance is not mediated through canonical pathways described in mature organs but rather through the expression of KNOTTED1-LIKE HOMEOBOX and other indeterminacy genes, altering known developmental pathways responsible for patterning leaf shape. We also demonstrate that shade-induced changes in leaf primordium gene expression largely do not overlap with those found in successively initiated leaf primordia, providing evidence against classic hypotheses that shaded leaf morphology results from the prolonged production of juvenile leaf types.

  18. Light-Induced Indeterminacy Alters Shade-Avoiding Tomato Leaf Morphology1[OPEN

    PubMed Central

    Chitwood, Daniel H.; Kumar, Ravi; Ranjan, Aashish; Pelletier, Julie M.; Townsley, Brad T.; Ichihashi, Yasunori; Martinez, Ciera C.; Zumstein, Kristina; Harada, John J.; Maloof, Julin N.; Sinha, Neelima R.

    2015-01-01

    Plants sense the foliar shade of competitors and alter their developmental programs through the shade-avoidance response. Internode and petiole elongation, and changes in overall leaf area and leaf mass per area, are the stereotypical architectural responses to foliar shade in the shoot. However, changes in leaf shape and complexity in response to shade remain incompletely, and qualitatively, described. Using a meta-analysis of more than 18,000 previously published leaflet outlines, we demonstrate that shade avoidance alters leaf shape in domesticated tomato (Solanum lycopersicum) and wild relatives. The effects of shade avoidance on leaf shape are subtle with respect to individual traits but are combinatorially strong. We then seek to describe the developmental origins of shade-induced changes in leaf shape by swapping plants between light treatments. Leaf size is light responsive late into development, but patterning events, such as stomatal index, are irrevocably specified earlier. Observing that shade induces increases in shoot apical meristem size, we then describe gene expression changes in early leaf primordia and the meristem using laser microdissection. We find that in leaf primordia, shade avoidance is not mediated through canonical pathways described in mature organs but rather through the expression of KNOTTED1-LIKE HOMEOBOX and other indeterminacy genes, altering known developmental pathways responsible for patterning leaf shape. We also demonstrate that shade-induced changes in leaf primordium gene expression largely do not overlap with those found in successively initiated leaf primordia, providing evidence against classic hypotheses that shaded leaf morphology results from the prolonged production of juvenile leaf types. PMID:26381315

  19. Conditions for bubble elongation in cold ice-sheet ice

    USGS Publications Warehouse

    Alley, R.B.; Fitzpatrick, J.J.

    1999-01-01

    Highly elongated bubbles are sometimes observed in ice-sheet ice. Elongation is favored by rapid ice deformation, and opposed by diffusive processes. We use simple models to show that vapor transport dominates diffusion except possibly very close to the melting point, and that latent-heat effects are insignificant. Elongation is favored by larger bubbles at pore close-off, but is nearly independent of bubble compression below close-off. The simple presence of highly elongated bubbles indicates only that a critical ice-strain rate has been exceeded for significant time, and provides no information on possible disruption of stratigraphic continuity by ice deformation.

  20. A coordinated codon-dependent regulation of translation by Elongator

    PubMed Central

    Bauer, Fanelie; Hermand, Damien

    2012-01-01

    More than a decade ago, the purification of the form of the RNA polymerase II (PolII) engaged in elongation led to the discovery of an associated, multi-subunit (Elp1-6) complex named “Elongator” by the Svejstrup lab. Although further evidence supported the original notion that Elongator is involved in transcription, Elongator lacked some of the expected features for a regulator of the elongating PolII. The discovery by the Byström lab, based on genetic dissection, that Elongator is pivotal for tRNA modifications, and that all the reported phenotypes of Elongator mutants are suppressed by the overexpression of two tRNAs added to the confusion. The increasing range of both potential substrates and biological processes regulated by Elongator in higher eukaryotes indicates that the major challenge of the field is to determine the biologically relevant function of Elongator. Our recent proteome-wide study in fission yeast supports a coordinated codon-dependent regulation of translation by Elongator. Here we provide additional analyses extending this hypothesis to budding yeast and worm. PMID:23165209

  1. Cuticular permeance in relation to wax and cutin development along the growing barley (Hordeum vulgare) leaf.

    PubMed

    Richardson, Andrew; Wojciechowski, Tobias; Franke, Rochus; Schreiber, Lukas; Kerstiens, Gerhard; Jarvis, Mike; Fricke, Wieland

    2007-05-01

    The developing leaf three of barley provides an excellent model system for the direct determination of relationships between amounts of waxes and cutin and cuticular permeance. Permeance of the cuticle was assessed via the time-course of uptake of either toluidine blue or (14)C-labelled benzoic acid ([(14)C] BA) along the length of the developing leaf. Toluidine blue uptake only occurred within the region 0-25 mm from the point of leaf insertion (POLI). Resistance--the inverse of permeance--to uptake of [(14)C] BA was determined for four leaf regions and was lowest in the region 10-20 mm above POLI. At 20-30 and 50-60 mm above POLI, it increased by factors of 6 and a further 32, respectively. Above the point of emergence of leaf three from the sheath of leaf two, which was 76-80 mm above POLI, resistance was as high as at 50-60 mm above POLI. GC-FID/MS analyses of wax and cutin showed that: (1) the initial seven fold increase in cuticular resistance coincided with increase in cutin coverage and appearance of waxes; (2) the second, larger and final increase in cuticle resistance was accompanied by an increase in wax coverage, whereas cutin coverage remained unchanged; (3) cutin deposition in barley leaf epidermis occurred in parallel with cell elongation, whereas deposition of significant amounts of wax commenced as cells ceased to elongate.

  2. Leaf growth is conformal

    NASA Astrophysics Data System (ADS)

    Alim, Karen; Armon, Shahaf; Shraiman, Boris I.; Boudaoud, Arezki

    2016-10-01

    Growth pattern dynamics lie at the heart of morphogenesis. Here, we investigate the growth of plant leaves. We compute the conformal transformation that maps the contour of a leaf at a given stage onto the contour of the same leaf at a later stage. Based on the mapping we predict the local displacement field in the leaf blade and find it to agree with the experimentally measured displacement field to 92%. This approach is applicable to any two-dimensional system with locally isotropic growth, enabling the deduction of the whole growth field just from observation of the tissue contour.

  3. (R)-β-lysine-modified elongation factor P functions in translation elongation.

    PubMed

    Bullwinkle, Tammy J; Zou, S Betty; Rajkovic, Andrei; Hersch, Steven J; Elgamal, Sara; Robinson, Nathaniel; Smil, David; Bolshan, Yuri; Navarre, William Wiley; Ibba, Michael

    2013-02-08

    Post-translational modification of bacterial elongation factor P (EF-P) with (R)-β-lysine at a conserved lysine residue activates the protein in vivo and increases puromycin reactivity of the ribosome in vitro. The additional hydroxylation of EF-P at the same lysine residue by the YfcM protein has also recently been described. The roles of modified and unmodified EF-P during different steps in translation, and how this correlates to its physiological role in the cell, have recently been linked to the synthesis of polyproline stretches in proteins. Polysome analysis indicated that EF-P functions in translation elongation, rather than initiation as proposed previously. This was further supported by the inability of EF-P to enhance the rate of formation of fMet-Lys or fMet-Phe, indicating that the role of EF-P is not to specifically stimulate formation of the first peptide bond. Investigation of hydroxyl-(β)-lysyl-EF-P showed 30% increased puromycin reactivity but no differences in dipeptide synthesis rates when compared with the β-lysylated form. Unlike disruption of the other genes required for EF-P modification, deletion of yfcM had no phenotypic consequences in Salmonella. Taken together, our findings indicate that EF-P functions in translation elongation, a role critically dependent on post-translational β-lysylation but not hydroxylation.

  4. Emerging brain morphologies from axonal elongation

    PubMed Central

    Holland, Maria A.; Miller, Kyle E.; Kuhl, Ellen

    2015-01-01

    Understanding the characteristic morphology of our brain remains a challenging, yet important task in human evolution, developmental biology, and neurosciences. Mathematical modeling shapes our understanding of cortical folding and provides functional relations between cortical wavelength, thickness, and stiffness. Yet, current mathematical models are phenomenologically isotropic and typically predict non-physiological, periodic folding patterns. Here we establish a mechanistic model for cortical folding, in which macroscopic changes in white matter volume are a natural consequence of microscopic axonal growth. To calibrate our model, we consult axon elongation experiments in chick sensory neurons. We demonstrate that a single parameter, the axonal growth rate, explains a wide variety of in vitro conditions including immediate axonal thinning and gradual thickness restoration. We embed our axonal growth model into a continuum model for brain development using axonal orientation distributions motivated by diffusion spectrum imaging. Our simulations suggest that white matter anisotropy - as an emergent property from directional axonal growth - intrinsically induces symmetry breaking, and predicts more physiological, less regular morphologies with regionally varying gyral wavelengths and sulcal depths. Mechanistic modeling of brain development could establish valuable relationships between brain connectivity, brain anatomy, and brain function. PMID:25824370

  5. Glycoproteome of Elongating Cotton Fiber Cells*

    PubMed Central

    Kumar, Saravanan; Kumar, Krishan; Pandey, Pankaj; Rajamani, Vijayalakshmi; Padmalatha, Kethireddy Venkata; Dhandapani, Gurusamy; Kanakachari, Mogilicherla; Leelavathi, Sadhu; Kumar, Polumetla Ananda; Reddy, Vanga Siva

    2013-01-01

    Cotton ovule epidermal cell differentiation into long fibers primarily depends on wall-oriented processes such as loosening, elongation, remodeling, and maturation. Such processes are governed by cell wall bound structural proteins and interacting carbohydrate active enzymes. Glycosylation plays a major role in the structural, functional, and localization aspects of the cell wall and extracellular destined proteins. Elucidating the glycoproteome of fiber cells would reflect its wall composition as well as compartmental requirement, which must be system specific. Following complementary proteomic approaches, we have identified 334 unique proteins comprising structural and regulatory families. Glycopeptide-based enrichment followed by deglycosylation with PNGase F and A revealed 92 unique peptides containing 106 formerly N-linked glycosylated sites from 67 unique proteins. Our results showed that structural proteins like arabinogalactans and carbohydrate active enzymes were relatively more abundant and showed stage- and isoform-specific expression patterns in the differentiating fiber cell. Furthermore, our data also revealed the presence of heterogeneous and novel forms of structural and regulatory glycoproteins. Comparative analysis with other plant glycoproteomes highlighted the unique composition of the fiber glycoproteome. The present study provides the first insight into the identity, abundance, diversity, and composition of the glycoproteome within single celled cotton fibers. The elucidated composition also indirectly provides clues about unicellular compartmental requirements underlying single cell differentiation. PMID:24019148

  6. Transcription elongation through a chromatin template.

    PubMed

    Lavelle, Christophe

    2007-04-01

    DNA transaction events occurring during cell life (replication, transcription, recombination, repair, cell division) are always linked to severe changes in the topological state of the double helix. However, since naked DNA almost does not exist in eukaryote nucleus but rather interacts with various proteins, including ubiquitous histones, these topological changes happen in a chromatin context. This review focuses on the role of chromatin fiber structure and dynamics in the regulation of transcription, with an almost exclusive emphasis on the elongation step. Beside a brief overview of our knowledge about transcribed chromatin, we will see how recent mechanistic and biochemical studies give us new insights into the way cell could modulate DNA supercoiling and chromatin conformational dynamics. The participation of topoisomerases in this complex ballet is discussed, since recent data suggest that their role could be closely related to the precise chromatin structure. Lastly, some future prospects to carry on are proposed, hoping this review will help in stimulating discussions and further investigations in the field.

  7. Project LEAF Documents

    EPA Pesticide Factsheets

    Project LEAF has a goal of educating farmworkers about how to reduce pesticide exposure to their families from pesticide residues they may be inadvertently taking home on their clothing, etc. Find outreach materials.

  8. Blastocyst Elongation, Trophoblastic Differentiation and Embryonic Pattern Formation

    USDA-ARS?s Scientific Manuscript database

    The molecular basis behind elongation and concomitant gastrulation in ungulates that occurs during pre-implantation is still poorly understood. In-depth transcriptome analysis of the elongating porcine conceptus at specific stages has demonstrated that protein synthesis, protein trafficking, cell g...

  9. Formation of Elongated Starch Granules in High-amylose Maize

    USDA-ARS?s Scientific Manuscript database

    GEMS-0067 maize starch contains up to 32% elongated starch granules much higher than amylose-extender (ae) single-mutant maize starch (~7%) and normal (non-mutant) maize starch (0%). These elongated granules are highly resistant to enzymatic hydrolysis at 95-100 C, which function as resistant starc...

  10. Induction of Coleoptile Elongation by Carbon Dioxide 1

    PubMed Central

    Evans, Michael L.; Ray, Peter M.; Reinhold, Leonora

    1971-01-01

    The ability of CO2 to induce elongation of Avena sativa coleoptile segments was examined with the use of a high resolution growth-recording device. CO2-saturated water causes an 8- to 16-fold promotion in the rate of elongation within 1 minute. This elongation is insensitive to a variety of metabolic inhibitors that suppress auxin-induced elongation, and the CO2 effect cannot be prevented by pretreatment with these inhibitors. Buffers of pH 3 to 4 also stimulate elongation quickly, and it seems that at least a major part of the action of CO2 depends upon its ability to reduce pH. The rate of elongation of auxin-promoted segments can be further enhanced by treatment with CO2 but not vice versa. The response to CO2 can be inhibited by mannitol at osmotic concentrations that inhibit normal growth, by calcium, and by brief pretreatment with heavy water (D2O). The elongation rate that results from CO2 treatment is sensitive to temperature, but the induction by CO2 itself appears to be almost temperature-independent. Elongation following treatment with CO2 may be a physical flow phenomenon, essentially independent of immediate biochemical participation, which occurs when wall polymer interactions that normally restrict strain in the cell wall are weakened or broken by CO2 in a manner that in effect substitutes for the role of metabolism in normal auxin-inducible cell enlargement. PMID:16657618

  11. Isolated Horner Syndrome From an Elongated Styloid Process (Eagle Syndrome).

    PubMed

    Chang, Caitlin A; Lin, Tony; Fung, Kevin; Sharma, Manas; Fraser, J Alexander

    2015-12-01

    Eagle syndrome occurs when an elongated styloid process causes otolaryngological or neurological symptoms or signs. We report a patient who had an isolated asymptomatic Horner syndrome that resulted from a pinned internal carotid artery being dynamically injured by an elongated styloid process during chiropractic neck manipulation. There was no evidence of arterial dissection.

  12. Ballooning mode stability of elongated high-beta tokamaks

    NASA Astrophysics Data System (ADS)

    Mauel, Michael E.

    1987-12-01

    The variational principle derived by Choe and Freidberg [Phys. Fluids 29, 1766 (1986)] and used to estimate the geometry of high-beta tokamak equilibria is extended to include elongation. Ballooning mode stability is then investigated, illustrating the influence of elongation on local and global stability.

  13. An elongation method for large systems toward bio-systems.

    PubMed

    Aoki, Yuriko; Gu, Feng Long

    2012-06-07

    The elongation method, proposed in the early 1990s, originally for theoretical synthesis of aperiodic polymers, has been reviewed. The details of derivation of the localization scheme adopted by the elongation method are described along with the elongation processes. The reliability and efficiency of the elongation method have been proven by applying it to various models of bio-systems, such as gramicidin A, collagen, DNA, etc. By means of orbital shift, the elongation method has been successfully applied to delocalized π-conjugated systems. The so-called orbital shift works in such a way that during the elongation process, some strongly delocalized frozen orbitals are assigned as active orbitals and joined with the interaction of the attacking monomer. By this treatment, it has been demonstrated that the total energies and non-linear optical properties determined by the elongation method are more accurate even for bio-systems and delocalized systems like fused porphyrin wires. The elongation method has been further developed for treating any three-dimensional (3D) systems and its applicability is confirmed by applying it to entangled insulin models whose terminal is capped by both neutral and zwitterionic sequences.

  14. Red Light-inhibited Mesocotyl Elongation in Maize Seedlings

    PubMed Central

    Vanderhoef, Larry N.; Briggs, Winslow R.

    1978-01-01

    Red light-inhibited mesocotyl elongation, which occurs in intact Zea mays L. seedlings, was studied in excised segments which included the coleoptile (or parts therefrom) and apical centimeter of the mesocotyl. Experiments took into account, first, the ability of the segments to regenerate auxin supply sites, and, second, that auxin uptake can be greatly reduced if there is no cut surface, apical to the elongating cells, to act as a port of entry. In all cases, auxin completely reversed the inhibition of elongation by light. The results support the hypothesis that light regulates mesocotyl elongation by controlling auxin supply from the coleoptile. Sucrose concentration had no effect on auxin reversal of light-inhibited elongation, but relatively high concentrations of gibberellic acid (10 μm) could substitute for auxin in this system. PMID:16660331

  15. High n ballooning modes in highly elongated tokamaks

    SciTech Connect

    An, C.H.; Bateman, G.

    1980-02-01

    An analytic study of stability against high n ballooning modes in highly elongated axisymmetric plasmas is presented and compared with computational results. From the equation for the marginal pressure gradient, it is found that the local shear plays an important role on the stability of elongated and shifted plasma, and that high elongation deteriorates the stability by decreasing the stabilizing effects of field line bending and local shear. The net contribution of the local shear to stability decreases with elongation and shift for strongly ballooning modes (eigenfunctions strongly localized near the outer edge of the toroidal flux surfaces) but increases for interchange modes (eigenfunctions more uniform along the flux surfaces). The computational study of high n ballooning modes in a highly elongated plasma reveals that lowering the aspect ratio and broadening the pressure profile enhance the marginal beta for ..beta../sub p/ less than unity but severely reduce the marginal beta for ..beta../sub p/ larger than unity.

  16. Sequence-dependent elongation dynamics on macrolide-bound ribosomes.

    PubMed

    Johansson, Magnus; Chen, Jin; Tsai, Albert; Kornberg, Guy; Puglisi, Joseph D

    2014-06-12

    The traditional view of macrolide antibiotics as plugs inside the ribosomal nascent peptide exit tunnel (NPET) has lately been challenged in favor of a more complex, heterogeneous mechanism, where drug-peptide interactions determine the fate of a translating ribosome. To investigate these highly dynamic processes, we applied single-molecule tracking of elongating ribosomes during inhibition of elongation by erythromycin of several nascent chains, including ErmCL and H-NS, which were shown to be, respectively, sensitive and resistant to erythromycin. Peptide sequence-specific changes were observed in translation elongation dynamics in the presence of a macrolide-obstructed NPET. Elongation rates were not severely inhibited in general by the presence of the drug; instead, stalls or pauses were observed as abrupt events. The dynamic pathways of nascent-chain-dependent elongation pausing in the presence of macrolides determine the fate of the translating ribosome stalling or readthrough.

  17. Elongated mandibular coronoid process as a cause of mandibular hypomobility.

    PubMed

    Kursoglu, Pinar; Capa, Nuray

    2006-07-01

    There are multiple factors in cases of mandibular hypomobility. One of these factors is elongated coronoid process. Two cases are presented to illustrate elongated coronoid process leading to mandibular hypomobility to help prevent misdiagnosis by clinicians. Coronoid process elongation is a rare condition. Both cases reported here had pulpitis on the teeth, however endodontic treatment could not be performed due to the restricted mouth opening in both cases. There were clinical findings of restricted range of motion, especially during protrusive movements. The restrictive movements did not cause pain for either patient, and the patients were not aware of their restricted mouth opening. Panoromic radiographs were taken and evaluated. The radiographs showed elongated coronoid process bilaterally. Three-dimensional computerized tomography was taken in one case only, due to the patient's financial restrictions. In cases of restricted mandibular opening, elongated coronoid process must be considered when diagnosing the cause.

  18. Deer predation on leaf miners via leaf abscission

    NASA Astrophysics Data System (ADS)

    Yamazaki, Kazuo; Sugiura, Shinji

    2008-03-01

    The evergreen oak Quercus gilva Blume sheds leaves containing mines of the leaf miner Stigmella sp. (Lepidoptera: Nepticulidae) earlier than leaves with no mines in early spring in Nara, central Japan. The eclosion rates of the leaf miner in abscised and retained leaves were compared in the laboratory to clarify the effects of leaf abscission on leaf miner survival in the absence of deer. The leaf miner eclosed successfully from both fallen leaves and leaves retained on trees. However, sika deer ( Cervus nippon centralis Kishida) feed on the fallen mined leaves. Field observations showed that deer consume many fallen leaves under Q. gilva trees, suggesting considerable mortality of leaf miners due to deer predation via leaf abscission. This is a previously unreported relationship between a leaf miner and a mammalian herbivore via leaf abscission.

  19. Deer predation on leaf miners via leaf abscission.

    PubMed

    Yamazaki, Kazuo; Sugiura, Shinji

    2008-03-01

    The evergreen oak Quercus gilva Blume sheds leaves containing mines of the leaf miner Stigmella sp. (Lepidoptera: Nepticulidae) earlier than leaves with no mines in early spring in Nara, central Japan. The eclosion rates of the leaf miner in abscised and retained leaves were compared in the laboratory to clarify the effects of leaf abscission on leaf miner survival in the absence of deer. The leaf miner eclosed successfully from both fallen leaves and leaves retained on trees. However, sika deer (Cervus nippon centralis Kishida) feed on the fallen mined leaves. Field observations showed that deer consume many fallen leaves under Q. gilva trees, suggesting considerable mortality of leaf miners due to deer predation via leaf abscission. This is a previously unreported relationship between a leaf miner and a mammalian herbivore via leaf abscission.

  20. Nanosecond plasma-mediated electrosurgery with elongated electrodes

    NASA Astrophysics Data System (ADS)

    Vankov, Alexander; Palanker, Daniel

    2007-06-01

    Progress in interventional medicine is associated with the development of more delicate and less invasive surgical procedures, which requires more precise and less traumatic, yet affordable, surgical instruments. Previously we reported on the development of the pulsed electron avalanche knife for dissection of soft tissue in liquid media using the 100 ns plasma-mediated electric discharges applied via a 25 μm disk microelectrode. Cavitation bubbles accompanying explosive vaporization of the liquid medium in front of such a pointed electrode produced a series of craters that did not always merge into a continuous cut. In addition, this approach of surface ablation provided a limited depth of cutting. Application of an elongated electrode capable of cutting with its edge rather than just with its pointed apex faces a problem of nonuniformity of the electric field on a nonspherical electrode. In this article we explore dynamics of the plasma-mediated nanosecond discharges in liquid medium in positive and negative polarities and describe the geometry of an electrode that provides a sufficiently uniform electric field along an extended edge of a surgical probe. A highly enhanced and uniform electric field was obtained on very sharp (2.5 μm) exposed edges of a planar electrode insulated on its flat sides. Uniform ionization and simultaneous vaporization was obtained along the whole edge of such a blade with 100 ns pulses at 4-6 kV. A continuous cutting rate of 1 mm/s in the retina and in soft membranes was achieved at a pulse repetition rate of 100 Hz. The collateral damage zone at the edges of incision did not exceed 80 μm. Negative polarity was found advantageous due to the lower rate of electrode erosion and due to better spatial confinement of the plasma-mediated discharge in liquid.

  1. Inhibition of gibberellin-induced elongation growth of rice by feruloyl oligosaccharides.

    PubMed

    Ishii, T; Nishijima, T

    1995-12-01

    The biological activity of cell wall-derived feruloyl oligosaccharides was investigated using a modified micro-drop bioassay. A feruloyl arabinoxylan trisaccharide (FAXX) and a feruloyl arabinoxylan tetrasaccharide (FAXXX) were found to inhibit the gibberellin-induced elongation of dwarf rice (Oryza sativa L., cv, Tan-ginbozu) that had been treated with uniconazole (S-3307), an inhibitor of the biosynthesis of gibberellins. An arabinoxylan trisaccharide (AXX) was ineffective. The growth-inhibitory effect of feruloyl oligosaccharides depended on their feruloyl and glycosyl moieties. The amount of esterified diferulic acid residues in the cell walls of the second leaf sheath of rice seedlings that had been treated with FAXX was almost same as that of controls. Feruloyl oligosaccharides did not inhibit the incorporation of [14C]leucine into acid-precipitable proteins by suspension-cultured maize cells, whereas cinnamic acid and its derivatives strongly inhibited such incorporation.

  2. The plant RNA polymerase II elongation complex: a hub coordinating transcript elongation and mRNA processing.

    PubMed

    Grasser, Marion; Grasser, Klaus D

    2017-09-08

    Characterisation of the Arabidopsis RNA polymerase II (RNAPII) elongation complex revealed an assembly of a conserved set of transcript elongation factors associated with chromatin remodellers, histone modifiers as well as with various pre-mRNA splicing and polyadenylation factors. Therefore, transcribing RNAPII streamlines the processes of mRNA synthesis and processing in plants.

  3. Nanoscale segregation of actin nucleation and elongation factors determines dendritic spine protrusion

    PubMed Central

    Chazeau, Anaël; Mehidi, Amine; Nair, Deepak; Gautier, Jérémie J; Leduc, Cécile; Chamma, Ingrid; Kage, Frieda; Kechkar, Adel; Thoumine, Olivier; Rottner, Klemens; Choquet, Daniel; Gautreau, Alexis; Sibarita, Jean-Baptiste; Giannone, Grégory

    2014-01-01

    Actin dynamics drive morphological remodeling of neuronal dendritic spines and changes in synaptic transmission. Yet, the spatiotemporal coordination of actin regulators in spines is unknown. Using single protein tracking and super-resolution imaging, we revealed the nanoscale organization and dynamics of branched F-actin regulators in spines. Branched F-actin nucleation occurs at the PSD vicinity, while elongation occurs at the tip of finger-like protrusions. This spatial segregation differs from lamellipodia where both branched F-actin nucleation and elongation occur at protrusion tips. The PSD is a persistent confinement zone for IRSp53 and the WAVE complex, an activator of the Arp2/3 complex. In contrast, filament elongators like VASP and formin-like protein-2 move outwards from the PSD with protrusion tips. Accordingly, Arp2/3 complexes associated with F-actin are immobile and surround the PSD. Arp2/3 and Rac1 GTPase converge to the PSD, respectively, by cytosolic and free-diffusion on the membrane. Enhanced Rac1 activation and Shank3 over-expression, both associated with spine enlargement, induce delocalization of the WAVE complex from the PSD. Thus, the specific localization of branched F-actin regulators in spines might be reorganized during spine morphological remodeling often associated with synaptic plasticity. PMID:25293574

  4. [New treatment for peripheral nerve defects: nerve elongation].

    PubMed

    Kou, Y H; Jiang, B G

    2016-10-18

    Peripheral nerve defects are still a major challenge in clinical practice, and the most commonly used method of treatment for peripheral nerve defects is nerve transplantation, which has certain limitations and shortcomings, so new repair methods and techniques are needed. The peripheral nerve is elongated in limb lengthening surgery without injury, from which we got inspirations and proposed a new method to repair peripheral nerve defects: peripheral nerve elongation. The peripheral nerve could beelongated by a certain percent, but the physiological change and the maximum elongation range were still unknown. This study discussed the endurance, the physiological and pathological change of peripheral nerve elongation in detail, and got a lot of useful data. First, we developed peripheral nerve extender which could match the slow and even extension of peripheral nerve. Then, our animal experiment result confirmed that the peripheral nerve had better endurance for chronic elongation than that of acute elongation and cleared the extensibility of peripheral nerve and the range of repair for peripheral nerve defects. Our result also revealed the histological basis and changed the rule for pathological physiology of peripheral nerve elongation: the most important structure foundation of peripheral nerve elongation was Fontana band, which was the coiling of nerve fibers under the epineurium, so peripheral nerve could be stretched for 8.5%-10.0% without injury because of the Fontana band. We confirmed that peripheral nerve extending technology could have the same repair effect as traditional nerve transplantation through animal experiments. Finally, we compared the clinical outcomes between nerve elongation and performance of the conventional method in the repair of short-distance transection injuries in human elbows, and the post-operative follow-up results demonstrated that early neurological function recovery was better in the nerve elongation group than in the

  5. Damped leaf flexure hinge

    NASA Astrophysics Data System (ADS)

    Chen, Zhong; Chen, Guisheng; Zhang, Xianmin

    2015-05-01

    Flexure-based mechanism like compliant actuation system embeds complex dynamics that will reduce the control bandwidth and limits their dynamic positioning precision. This paper presents a theoretical model of a leaf flexure hinge with damping layers using strain energy method and Kelvin damping model. The modified loss factor of the damped leaf flexure hinge is derived, and the equivalent viscous damping coefficient of the damped leaf hinge is obtained, which could be used to improve the pseudo-rigid-model. The free vibration signals of the hinge in three different damping configurations are measured. The experimental modal analysis also is performed on the three kinds of damped leaf flexure hinges in order to evaluate their 1st order bending natural frequency and vibration-suppressing effects. The evaluation of modified loss factor model also is performed. The experimental results indicate that the constrained layer damping can enhance the structure damping of the hinge even if only single damping layer each side, the modified loss factor model can get good predicts of a damped leaf flexure hinge in the frequency range below 1st order natural frequency, and it is necessary that the dimensional parameters of the damping layers and basic layer of the hinge should be optimized for simplification at the mechanism's design stage.

  6. Damped leaf flexure hinge.

    PubMed

    Chen, Zhong; Chen, Guisheng; Zhang, Xianmin

    2015-05-01

    Flexure-based mechanism like compliant actuation system embeds complex dynamics that will reduce the control bandwidth and limits their dynamic positioning precision. This paper presents a theoretical model of a leaf flexure hinge with damping layers using strain energy method and Kelvin damping model. The modified loss factor of the damped leaf flexure hinge is derived, and the equivalent viscous damping coefficient of the damped leaf hinge is obtained, which could be used to improve the pseudo-rigid-model. The free vibration signals of the hinge in three different damping configurations are measured. The experimental modal analysis also is performed on the three kinds of damped leaf flexure hinges in order to evaluate their 1st order bending natural frequency and vibration-suppressing effects. The evaluation of modified loss factor model also is performed. The experimental results indicate that the constrained layer damping can enhance the structure damping of the hinge even if only single damping layer each side, the modified loss factor model can get good predicts of a damped leaf flexure hinge in the frequency range below 1st order natural frequency, and it is necessary that the dimensional parameters of the damping layers and basic layer of the hinge should be optimized for simplification at the mechanism's design stage.

  7. The shape of a long leaf

    PubMed Central

    Liang, Haiyi; Mahadevan, L.

    2009-01-01

    Long leaves in terrestrial plants and their submarine counterparts, algal blades, have a typical, saddle-like midsurface and rippled edges. To understand the origin of these morphologies, we dissect leaves and differentially stretch foam ribbons to show that these shapes arise from a simple cause, the elastic relaxation via bending that follows either differential growth (in leaves) or differential stretching past the yield point (in ribbons). We quantify these different modalities in terms of a mathematical model for the shape of an initially flat elastic sheet with lateral gradients in longitudinal growth. By using a combination of scaling concepts, stability analysis, and numerical simulations, we map out the shape space for these growing ribbons and find that as the relative growth strain is increased, a long flat lamina deforms to a saddle shape and/or develops undulations that may lead to strongly localized ripples as the growth strain is localized to the edge of the leaf. Our theory delineates the geometric and growth control parameters that determine the shape space of finite laminae and thus allows for a comparative study of elongated leaf morphology. PMID:19966215

  8. Mapping the messenger RNA within the elongating ribosome

    NASA Astrophysics Data System (ADS)

    Jünemann, R.; Wadzack, J.; Burkhardt, N.; Schmitt, M.; Zhao, J.; Stuhrmann, H. B.; Nierhaus, K. H.

    1997-02-01

    The method of proton-spin contrast-variation was applied for determining the position of the messenger RNA within the elongating ribosome. Using an artificial mRNA fragment the mass center of the mRNA sequence covered by the ribosome could be localized for the pre- and the post-translocational elongation states. The mass center moves about 12 ± 5 Å upon translocation. The radius of gyration was 12 ± e Å. The data give an independent contribution for refining a structural model including the RNA ligands of the elongating ribosome.

  9. Phytochrome Control of Maize Coleoptile Section Elongation 1

    PubMed Central

    Warner, Timothy J.; Ross, James D.; Coombs, James

    1981-01-01

    A rapid loss of far red light (FR) reversibility of red-light (R) stimulated elongation of maize coleoptile sections was observed. Reversal was not possible when the interval between R and FR treatment was greater than 45 seconds. Most of the R-stimulated elongation occurred during the first 15 hours after irradiation. Exogenous gibberellic acid did not alter the time course of R/FR reversibility loss. These results are interpreted as indicating independence of R- and gibberellic acid-stimulated elongation in this system. PMID:16661674

  10. Control of Transcriptional Elongation by RNA Polymerase II: A Retrospective.

    PubMed

    Brannan, Kris; Bentley, David L

    2012-01-01

    The origins of our current understanding of control of transcription elongation lie in pioneering experiments that mapped RNA polymerase II on viral and cellular genes. These studies first uncovered the surprising excess of polymerase molecules that we now know to be situated at the at the 5' ends of most genes in multicellular organisms. The pileup of pol II near transcription start sites reflects a ubiquitous bottle-neck that limits elongation right at the start of the transcription elongation. Subsequent seminal work identified conserved protein factors that positively and negatively control the flux of polymerase through this bottle-neck, and make a major contribution to control of gene expression.

  11. Selenotrisulfide inhibits initiation by RNA polymerase II but not elongation

    SciTech Connect

    Frenkel, G.D.; Falvey, D.

    1989-03-01

    We previously reported that RNA polymerase II (purified from wheat germ) is inhibited by selenotrisulfides, the products of the reaction of selenite with sulfhydryl compounds. We have now found that the initiation stage of the reaction is inhibited by selenotrisulfide but the elongation stage of the reaction is not. The actual start of the RNA chain is not inhibited by the selenotrisulfide, but rather the formation of the enzyme-DNA binary complex. Selenotrisulfide has a similar differential effect on initiation and elongation by RNA polymerase II from HeLa cells; in contrast, with E. coli RNA polymerase, it inhibits elongation as well.

  12. Comparison of flooding-tolerance in four mangrove species in a diurnal tidal zone in the Beibu Gulf

    NASA Astrophysics Data System (ADS)

    He, Binyuan; Lai, Tinghe; Fan, Hangqing; Wang, Wenqing; Zheng, Hailei

    2007-08-01

    The flood tolerance of four mangrove species, Aegiceras corniculatum (L.) Blanco (AC), Avicennia marina (Forsk.) Vierh. (Am), Bruguiera gymnorrhiza (L.) Savigny (Bg) and Rhizophora stylosa Griff. (Rs) was examined in a field trial conducted from August 2004 until August 2005 in a diurnal tidal zone in Yingluo Bay, Guangxi province, China. In a section of tidal flat, three replicate artificial platforms were constructed for seedling cultivation. Eight different tidal flat elevation (TFE) treatments were created on each platform. After one year of cultivation under the TFE treatments, the survival rate and growth parameters of seedlings were measured. Seedlings of A. corniculatum and A. marina seedlings survived all treatments. The survival rate of B. gymnorrhiza and R. stylosa seedlings, however, decreased sharply as the TFE fell; in any treatment, fewer B. gymnorrhiza seedlings survived than R. stylosa seedlings. Stem elongation in A. corniculatum and A. marina seedlings was significantly increased by lower TFEs. Lower TFE treatments also increased stem heights in B. gymnorrhiza and R. stylosa seedlings; however, growth was significantly higher as TFE increased. Leaf number, leaf conservation rate and leaf area per seedling changed relatively little among treatments in A. corniculatum and A. marina seedlings, while these three indexes in B. gymnorrhiza and R. stylosa seedlings all decreased dramatically with decreasing TFE. A. marina seedlings reached a higher neonatal biomass at lower TFE treatments, whereas A. corniculatum seedlings attained a higher biomass under moderate TFEs. In contrast, B. gymnorrhiza and R. stylosa seedlings accumulated more biomass in the higher TFEs habitats. Biomass partitioning among the components of both A. corniculatum and A. marina seedlings changed evenly; however, A. corniculatum accumulated more biomass in the leaf while A. marina accumulated more in the stem. The TFE treatments greatly influenced biomass partitioning in B

  13. Multi-walled carbon nanotubes can enhance root elongation of wheat ( Triticum aestivum) plants

    NASA Astrophysics Data System (ADS)

    Wang, Xiuping; Han, Heyou; Liu, Xueqin; Gu, Xiaoxu; Chen, Kun; Lu, Donglian

    2012-06-01

    The potential effects of oxidized multi-walled carbon nanotubes (o-MWCNTs) with a length ranging from 50 to 630 nm on the development and physiology of wheat plants were evaluated by examining their effects on seed germination, root elongation, stem length, and vegetative biomass at a concentration ranging from 10 to 160 μg/mL in the plant. Results indicated that after 7 days of exposure to the o-MWCNTs medium, faster root growth and higher vegetative biomass were observed, but seed germination and stem length did not show any difference as compared with controls. Moreover, a physiological study was conducted at cellular level using a traditional physiological approach to evidence the possible alterations in morphology, the cell length of root zone, and the dehydrogenase activity of seedlings. Transmission electron microscopy images revealed that o-MWCNTs could penetrate the cell wall and enter the cytoplasm after being taken up by roots. The cell length of root zone for the seedlings germinated and grown in the o-MWCNTs (80 μg/mL) medium increased by 1.4-fold and a significant concentration-dependent increase in the dehydrogenase activity for the o-MWCNT-treated wheat seedlings was detected. These findings suggest that o-MWCNTs can significantly promote cell elongation in the root system and increase the dehydrogenase activity, resulting in faster root growth and higher biomass production.

  14. Amyloid-like fibril elongation follows michaelis-menten kinetics.

    PubMed

    Milto, Katazyna; Botyriute, Akvile; Smirnovas, Vytautas

    2013-01-01

    A number of proteins can aggregate into amyloid-like fibrils. It was noted that fibril elongation has similarities to an enzymatic reaction, where monomers or oligomers would play a role of substrate and nuclei/fibrils would play a role of enzyme. The question is how similar these processes really are. We obtained experimental data on insulin amyloid-like fibril elongation at the conditions where other processes which may impact kinetics of fibril formation are minor and fitted it using Michaelis-Menten equation. The correlation of the fit is very good and repeatable. It speaks in favour of enzyme-like model of fibril elongation. In addition, obtained [Formula: see text] and [Formula: see text] values at different conditions may help in better understanding influence of environmental factors on the process of fibril elongation.

  15. Morphological and Chemical Mechanisms of Elongated Mineral Particle Toxicities

    EPA Science Inventory

    Much of our understanding regarding the mechanisms for induction of disease following inhalation of respirable elongated mineral particles (REMPs) is based on studies involving the biological effects of asbestos fibers. The factors governing the disease potential of an exposure i...

  16. Morphological and Chemical Mechanisms of Elongated Mineral Particle Toxicities

    EPA Science Inventory

    Much of our understanding regarding the mechanisms for induction of disease following inhalation of respirable elongated mineral particles (REMPs) is based on studies involving the biological effects of asbestos fibers. The factors governing the disease potential of an exposure i...

  17. Direct Characterization of Transcription Elongation by RNA Polymerase I.

    PubMed

    Ucuncuoglu, Suleyman; Engel, Krysta L; Purohit, Prashant K; Dunlap, David D; Schneider, David A; Finzi, Laura

    2016-01-01

    RNA polymerase I (Pol I) transcribes ribosomal DNA and is responsible for more than 60% of transcription in a growing cell. Despite this fundamental role that directly impacts cell growth and proliferation, the kinetics of transcription by Pol I are poorly understood. This study provides direct characterization of S. Cerevisiae Pol I transcription elongation using tethered particle microscopy (TPM). Pol I was shown to elongate at an average rate of approximately 20 nt/s. However, the maximum speed observed was, in average, about 60 nt/s, comparable to the rate calculated based on the in vivo number of active genes, the cell division rate and the number of engaged polymerases observed in EM images. Addition of RNA endonucleases to the TPM elongation assays enhanced processivity. Together, these data suggest that additional transcription factors contribute to efficient and processive transcription elongation by RNA polymerase I in vivo.

  18. Direct Characterization of Transcription Elongation by RNA Polymerase I

    PubMed Central

    Ucuncuoglu, Suleyman; Engel, Krysta L.; Purohit, Prashant K.; Dunlap, David D.; Schneider, David A.

    2016-01-01

    RNA polymerase I (Pol I) transcribes ribosomal DNA and is responsible for more than 60% of transcription in a growing cell. Despite this fundamental role that directly impacts cell growth and proliferation, the kinetics of transcription by Pol I are poorly understood. This study provides direct characterization of S. Cerevisiae Pol I transcription elongation using tethered particle microscopy (TPM). Pol I was shown to elongate at an average rate of approximately 20 nt/s. However, the maximum speed observed was, in average, about 60 nt/s, comparable to the rate calculated based on the in vivo number of active genes, the cell division rate and the number of engaged polymerases observed in EM images. Addition of RNA endonucleases to the TPM elongation assays enhanced processivity. Together, these data suggest that additional transcription factors contribute to efficient and processive transcription elongation by RNA polymerase I in vivo. PMID:27455049

  19. The elongation, termination, and recycling phases of translation in eukaryotes.

    PubMed

    Dever, Thomas E; Green, Rachel

    2012-07-01

    This work summarizes our current understanding of the elongation and termination/recycling phases of eukaryotic protein synthesis. We focus here on recent advances in the field. In addition to an overview of translation elongation, we discuss unique aspects of eukaryotic translation elongation including eEF1 recycling, eEF2 modification, and eEF3 and eIF5A function. Likewise, we highlight the function of the eukaryotic release factors eRF1 and eRF3 in translation termination, and the functions of ABCE1/Rli1, the Dom34:Hbs1 complex, and Ligatin (eIF2D) in ribosome recycling. Finally, we present some of the key questions in translation elongation, termination, and recycling that remain to be answered.

  20. The Emerging Role of Forces in Axonal Elongation

    PubMed Central

    Suter, Daniel M.; Miller, Kyle E.

    2011-01-01

    An understanding of how axons elongate is needed to develop rational strategies to treat neurological diseases and nerve injury. Growth cone-mediated neuronal elongation is currently viewed as occurring through cytoskeletal dynamics involving the polymerization of actin and tubulin subunits at the tip of the axon. However, recent work suggests that axons and growth cones also generate forces (through cytoskeletal dynamics, kinesin, dynein, and myosin), forces induce axonal elongation, and axons lengthen by stretching. This review highlights results from various model systems (Drosophila, Aplysia, Xenopus, chicken, mouse, rat, and PC12 cells), supporting a role for forces, bulk microtubule movements, and intercalated mass addition in the process of axonal elongation. We think that a satisfying answer to the question, “How do axons grow?” will come by integrating the best aspects of biophysics, genetics, and cell biology. PMID:21527310

  1. Shear of ordinary and elongated granular mixtures

    NASA Astrophysics Data System (ADS)

    Hensley, Alexander; Kern, Matthew; Marschall, Theodore; Teitel, Stephen; Franklin, Scott

    2015-03-01

    We present an experimental and computational study of a mixture of discs and moderate aspect-ratio ellipses under two-dimensional annular planar Couette shear. Experimental particles are cut from acrylic sheet, are essentially incompressible, and constrained in the thin gap between two concentric cylinders. The annular radius of curvature is much larger than the particles, and so the experiment is quasi-2d and allows for arbitrarily large pure-shear strains. Synchronized video cameras and software identify all particles and track them as they move from the field of view of one camera to another. We are particularly interested in the global and local properties as the mixture ratio of discs to ellipses varies. Global quantities include average shear rate and distribution of particle species as functions of height, while locally we investigate the orientation of the ellipses and non-affine events that can be characterized as shear transformational zones or possess a quadrupole signature observed previously in systems of purely circular particles. Discrete Element Method simulations on mixtures of circles and spherocylinders extend the study to the dynamics of the force network and energy dissipated as the system evolves. Supported by NSF CBET #1243571 and PRF #51438-UR10.

  2. Root-to-shoot signalling when soil moisture is heterogeneous: increasing the proportion of root biomass in drying soil inhibits leaf growth and increases leaf abscisic acid concentration.

    PubMed

    Martin-Vertedor, Ana Isabel; Dodd, Ian C

    2011-07-01

    To determine whether root-to-shoot signalling of soil moisture heterogeneity depended on root distribution, wild-type (WT) and abscisic acid (ABA)-deficient (Az34) barley (Hordeum vulgare) plants were grown in split pots into which different numbers of seminal roots were inserted. After establishment, all plants received the same irrigation volumes, with one pot watered (w) and the other allowed to dry the soil (d), imposing three treatments (1 d: 3 w, 2 d: 2 w, 3 d: 1 w) that differed in the number of seminal roots exposed to drying soil. Root distribution did not affect leaf water relations and had no sustained effect on plant evapotranspiration (ET). In both genotypes, leaf elongation was less and leaf ABA concentrations were higher in plants with more roots in drying soil, with leaf ABA concentrations and water potentials 30% and 0.2 MPa higher, respectively, in WT plants. Whole-pot soil drying increased xylem ABA concentrations, but maximum values obtained when leaf growth had virtually ceased (100 nm in Az34, 330 nm in WT) had minimal effects (<40% leaf growth inhibition) when xylem supplied to detached shoots. Although ABA may not regulate leaf growth in vivo, genetic variation in foliar ABA concentration in the field may indicate different root distributions between upper (drier) and lower (wetter) soil layers.

  3. Comparative leaf development in angiosperms.

    PubMed

    Tsukaya, Hirokazu

    2014-02-01

    Recent accumulation of our knowledge on basic leaf development mechanisms in model angiosperm species has allowed us to pursue evolutionary development (evo/devo) studies of various kinds of leaf development. As a result, unexpected findings and clues have been unearthed aiding our understanding of the mechanisms involved in the diversity of leaf morphology, although the covered remain limited. In this review, we highlight recent findings of diversified leaf development in angiosperms.

  4. Maple Leaf Outdoor Centre.

    ERIC Educational Resources Information Center

    Maguire, Molly; Gunton, Ric

    2000-01-01

    Maple Leaf Outdoor Centre (Ontario) has added year-round outdoor education facilities and programs to help support its summer camp for disadvantaged children. Schools, youth centers, religious groups, and athletic teams conduct their own programs, collaborate with staff, or use staff-developed programs emphasizing adventure education and personal…

  5. Bacterial leaf spot

    USDA-ARS?s Scientific Manuscript database

    Bacterial leaf spot has been reported in Australia (Queensland), Egypt, El Salvador, India, Japan, Nicaragua, Sudan, and the United States (Florida, Iowa, Kansas, Maryland, and Wisconsin). It occasionally causes locally severe defoliation and post-emergence damping-off and stunting. The disease is...

  6. Cucumber leaf spot virus

    USDA-ARS?s Scientific Manuscript database

    Cucumber leaf spot virus (CLSV) was originally identified from cucumber (Cucumis sativus) in Germany, but has since been found in various parts of Europe, the UK, and the Middle East, including Jordan, Saudi Arabia, Bulgaria, Poland, and Spain. CLSV is known to cause symptoms ranging from chloroti...

  7. Is Cervical Elongation Associated with Pelvic Organ Prolapse?

    PubMed Central

    Berger, Mitchell B.; Ramanah, Rajeev; Guire, Kenneth E.; DeLancey, John O. L.

    2012-01-01

    Introduction and Hypothesis It is commonly believed that pelvic organ prolapse is associated with cervical elongation. However, cervical lengths have not been formally compared between women with prolapse and those with normal support. Methods Cervix and uterine corpus lengths were measured on magnetic resonance images in a case-control study of 51 women with prolapse and 46 women with normal support determined by pelvic organ prolapse (POP) quantification (POP-Q) examination. Group matching ensured similar demographics in both groups. Ranges for normal cervical lengths were determined from the values in the control group in order to evaluate for cervical elongation amongst women with prolapse. Results The cervix is 36.4% (8.6 mm) longer in women with prolapse than in women with normal pelvic support (p < 0.001). Linear regression modeling suggests the feature most highly associated with cervical length is the degree of uterine descent (POP-Q point C). Approximately 40% of women with prolapse have cervical elongation. 57% of cervical elongation in prolapse can be explained by a logistic-regression based model including POP-Q point C, body mass index and menopausal status. Conclusion Cervical elongation is found in one-third of women with pelvic organ prolapse, with the extent of elongation increasing with greater degrees of uterine descent. PMID:22527546

  8. Insights on the development, kinetics, and variation of photoinhibition using chlorophyll fluorescence imaging of a chilled, variegated leaf.

    PubMed

    Hogewoning, Sander W; Harbinson, Jeremy

    2007-01-01

    The effect of chilling on photosystem II (PSII) efficiency was studied in the variegated leaves of Calathea makoyana, in order to gain insight into the causes of chilling-induced photoinhibition. Additionally, a relationship was revealed between (chilling) stress and variation in photosynthesis. Chilling treatments (5 degrees C and 10 degrees C) were performed for different durations (1-7 d) under a moderate irradiance (120 micromol m-2 s-1). The individual leaves were divided into a shaded zone and two illuminated, chilled zones. The leaf tip and sometimes the leaf base were not chilled. Measurements of the dark-adapted Fv/Fm were made on the different leaf zones at the end of the chilling treatment, and then for several days thereafter to monitor recovery. Chilling up to 7 d in the dark did not affect PSII efficiency and visual appearance, whereas chilling in the light caused severe photoinhibition, sometimes followed by leaf necrosis. Photoinhibition increased with the duration of the chilling period, whereas, remarkably, chilling temperature had no effect. In the unchilled leaf tip, photoinhibition also occurred, whereas in the unchilled leaf base it did not. Whatever the leaf zone, photoinhibition became permanent if the mean value dropped below 0.4, although chlorosis and necrosis were associated solely with chilled illuminated tissue. Starch accumulated in the unchilled leaf tip, in contrast to the adjacent chilled irradiated zone. This suggests that photoinhibition was due to a secondary effect in the unchilled leaf tip (sink limitation), whereas it was a direct effect of chilling and irradiance in the chilled illuminated zones. The PSII efficiency and its coefficient of variation showed a unique negative linearity across all leaf zones and different tissue types. The slope of this curve was steeper for chilled leaves than it was for healthy, non-stressed leaves, suggesting that the coefficient of variation may be an important tool for assessing stress in

  9. Identification and Characterization of Pseudocercospora pyricola Causing Leaf Spots on Aronia melanocarpa

    PubMed Central

    Park, Sung-Hee; Choi, In-Young; Seo, Kyoung-Won; Kim, Jin-Ho; Galea, Victor

    2017-01-01

    Leaf spot disease on black chokeberry (Aronia melanocarpa) was observed at several locations in Korea during 2014–2015. Leaf spots were distinct, scattered over the leaf surface and along the leaf border, subcircular to irregular and brown surrounded by a distinct dark color, and were expanded and coalesced into irregularly shaped lesions. Severely infected leaves became dry and fell off eventually. The causative agent was identified as Pseudocercospora pyricola. Morphological observations and phylogenetic analyses of multiple genes, including internal transcribed spacer, translation elongation factor 1-alpha, actin, and the large subunit ribosomal DNA were conducted. The pathogenicity test was conducted twice yielding similar results, fulfilling Koch's postulates. To our knowledge, this is the first report on P. pyricola infection of A. melanocarpa globally. PMID:28435353

  10. Antibacterial and antioxidant activities of Vaccinium corymbosum L. leaf extract

    PubMed Central

    Pervin, Mehnaz; Hasnat, Md Abul; Lim, Beong Ou

    2013-01-01

    Objective To investigate antibacterial and antioxidant activity of the leaf extract of tropical medicinal herb and food plant Vaccinium corymbosum L. (V. corymbosum). Methods Free radical scavenging activity on DPPH, ABTS, and nitrites were used to analyse phenoic and flavonoid contents of leaf extract. Other focuses included the determination of antioxidant enzymatic activity (SOD, CAT and GPx), metal chelating activity, reduction power, lipid peroxidation inhibition and the prevention of oxidative DNA damage. Antibacterial activity was determined by using disc diffusion for seven strains of bacteria. Results Results found that V. corymbosum leaf extract had significant antibacterial activity. The tested extract displayed the highest activity (about 23.18 mm inhibition zone) against Salmonella typhymurium and the lowest antibacterial activity was observed against Enterococcus faecalis (about 14.08 mm inhibition zone) at 10 mg/ disc. The IC50 values for DPPH, ABTS and radical scavenging activity were 0.120, 0.049 and 1.160 mg/mL, respectively. V. corymbosum leaf extract also showed dose dependent reduction power, lipid peroxidation, DNA damage prevention and significant antioxidant enzymatic activity. Conclusions These findings demonstrate that leaf extract of V. corymbosum could be used as an alternative therapy for antibiotic-resistant bacteria and help prevent various free radical related diseases.

  11. The polar auxin transport inhibitor N-1-naphthylphthalamic acid disrupts leaf initiation, KNOX protein regulation, and formation of leaf margins in maize.

    PubMed

    Scanlon, Michael J

    2003-10-01

    Maize (Zea mays) leaves develop basipetally (tip to base); the upper blade emerges from the shoot apical meristem (SAM) before the expansion of the lower sheath. Founder cells, leaf initials located in the periphery of the SAM, are distinguished from the SAM proper by the differential accumulation of KNOX proteins. KNOX proteins accumulate in the SAM, but are excluded from maize leaf primordia and leaf founder cells. As in Arabidopsis and tomato (Lycopersicon esculentum), maize shoots failed to initiate new leaves when cultured in the polar auxin transport inhibitor N-1-naphthylphthalamic acid (NPA). We demonstrate that NPA-induced arrest of leaf initiation in maize is correlated with the failure to down-regulate KNOX accumulation in the SAM. In addition, NPA-cultured shoots formed abnormal tubular leaf bases in which the margins failed to separate in the lower leaf zone. The tubular leaf bases always formed in the fourth leaf from the arrested meristem. Moreover, the unseparated margin domains of these tubular leaf bases accumulated ectopic KNOX protein(s). Transfer of NPA-cultured apices to NPA-free media resulted in the resumption of leaf initiation from the SAM and the restoration of normal patterns of KNOX down-regulation, accordingly. These data suggest that the lower sheath margins emerge from the leaf base late in maize leaf development and that the separation of these leaf margin domains is correlated with auxin transport and down-regulation of KNOX proteins. In addition, these results suggest that the down-regulation of KNOX accumulation in maize apices is not upstream of polar auxin transport, although a more complicated feedback network may exist. A model for L1-derived margin development in maize leaves is presented.

  12. Characterizing natural cellulose fibers from velvet leaf (Abutilon theophrasti) stems.

    PubMed

    Reddy, Narendra; Yang, Yiqi

    2008-05-01

    Velvet leaf (Abutilon theophrasti) that is currently considered a weed and an agricultural problem could be used as a source for high quality natural cellulose fibers. The fibers obtained from the velvet leaf stems are mainly composed of approximately 69% cellulose and 17% lignin. The single cells in the fiber have lengths of approximately 0.9 mm, shorter than those in common bast fibers, hemp and kenaf. However, the widths of single cells in velvet leaf fibers are similar to the single cells in hemp and kenaf. The fibers exhibited breaking tenacity from 2.4 to 3.9 g/denier (325-500 MPa), breaking elongation of 1.6-2.4% and Young's modulus of 140-294 g/denier (18-38 GPa). Overall, velvet leaf fibers have properties similar to that of common bast fibers such as hemp and kenaf. Velvet leaves fibers could be processed on the current kenaf processing machineries for textile, composite, automotive and other fibrous applications.

  13. Evolution of Body Elongation in Gymnophthalmid Lizards: Relationships with Climate

    PubMed Central

    Grizante, Mariana B.; Brandt, Renata; Kohlsdorf, Tiana

    2012-01-01

    The evolution of elongated body shapes in vertebrates has intrigued biologists for decades and is particularly recurrent among squamates. Several aspects might explain how the environment influences the evolution of body elongation, but climate needs to be incorporated in this scenario to evaluate how it contributes to morphological evolution. Climatic parameters include temperature and precipitation, two variables that likely influence environmental characteristics, including soil texture and substrate coverage, which may define the selective pressures acting during the evolution of morphology. Due to development of geographic information system (GIS) techniques, these variables can now be included in evolutionary biology studies and were used in the present study to test for associations between variation in body shape and climate in the tropical lizard family Gymnophthalmidae. We first investigated how the morphological traits that define body shape are correlated in these lizards and then tested for associations between a descriptor of body elongation and climate. Our analyses revealed that the evolution of body elongation in Gymnophthalmidae involved concomitant changes in different morphological traits: trunk elongation was coupled with limb shortening and a reduction in body diameter, and the gradual variation along this axis was illustrated by less-elongated morphologies exhibiting shorter trunks and longer limbs. The variation identified in Gymnophthalmidae body shape was associated with climate, with the species from more arid environments usually being more elongated. Aridity is associated with high temperatures and low precipitation, which affect additional environmental features, including the habitat structure. This feature may influence the evolution of body shape because contrasting environments likely impose distinct demands for organismal performance in several activities, such as locomotion and thermoregulation. The present study establishes a

  14. Evolution of body elongation in gymnophthalmid lizards: relationships with climate.

    PubMed

    Grizante, Mariana B; Brandt, Renata; Kohlsdorf, Tiana

    2012-01-01

    The evolution of elongated body shapes in vertebrates has intrigued biologists for decades and is particularly recurrent among squamates. Several aspects might explain how the environment influences the evolution of body elongation, but climate needs to be incorporated in this scenario to evaluate how it contributes to morphological evolution. Climatic parameters include temperature and precipitation, two variables that likely influence environmental characteristics, including soil texture and substrate coverage, which may define the selective pressures acting during the evolution of morphology. Due to development of geographic information system (GIS) techniques, these variables can now be included in evolutionary biology studies and were used in the present study to test for associations between variation in body shape and climate in the tropical lizard family Gymnophthalmidae. We first investigated how the morphological traits that define body shape are correlated in these lizards and then tested for associations between a descriptor of body elongation and climate. Our analyses revealed that the evolution of body elongation in Gymnophthalmidae involved concomitant changes in different morphological traits: trunk elongation was coupled with limb shortening and a reduction in body diameter, and the gradual variation along this axis was illustrated by less-elongated morphologies exhibiting shorter trunks and longer limbs. The variation identified in Gymnophthalmidae body shape was associated with climate, with the species from more arid environments usually being more elongated. Aridity is associated with high temperatures and low precipitation, which affect additional environmental features, including the habitat structure. This feature may influence the evolution of body shape because contrasting environments likely impose distinct demands for organismal performance in several activities, such as locomotion and thermoregulation. The present study establishes a

  15. An optical solution to the LGS spot elongation problem

    NASA Astrophysics Data System (ADS)

    Schreiber, Laura; Lombini, Matteo; Foppiani, Italo; Diolaiti, Emiliano; Conan, Jean-Marc; Marchetti, Enrico

    2008-07-01

    In the last years an increasing consideration has been given to the study of Laser Guide Stars (LGS) for the measurement of the disturbance introduced by the atmosphere. Due to the finite distance of the artificial reference source and its vertical extension (the Sodium layer occurs at approximately 90 km, with a vertical thickness of about 10 km), the source itself looks elongated, when observed from the edge of a large aperture. On a 40 m class telescope, for instance, the maximum elongation varies between 4 and 6 arcseconds, depending on the Sodium layer properties and on the launching position. This spot elongation strongly limits the performance of the most common wavefront sensors. A straightforward solution for a Shack-Hartmann wavefront sensor is to increase the laser power, in order to balance the loss of centroiding accuracy due to the elongation. This solution, although appealing in principle, presents drawbacks related, for instance, to the availability of very powerful lasers. We propose in this paper a wavefront sensor concept that provides an optical solution to the perspective elongation problem. It is based on an array of bi-prisms placed in the focal plane of a lenslet array; each bi-prism is aligned to the elongated spot produced by the corresponding lenslet; the spot is split into two beams, that are re-imaged into two micro-images of the sub-aperture itself; the difference in the integrated intensity of these two micro-images is proportional to the local wavefront slope. This method is sensitive only to the slope information in the direction locally orthogonal to the bi-prisms (and to the elongation) and the full information has to be recovered by combining the signals coming from different LGSs launched from different positions at the telescope edge. The pros and cons of this technique, in terms of hardware requirements and photon budget, are discussed in this paper.

  16. Leaf absorbance and photosynthesis

    NASA Technical Reports Server (NTRS)

    Schurer, Kees

    1994-01-01

    The absorption spectrum of a leaf is often thought to contain some clues to the photosynthetic action spectrum of chlorophyll. Of course, absorption of photons is needed for photosynthesis, but the reverse, photosynthesis when there is absorption, is not necessarily true. As a check on the existence of absorption limits we measured spectra for a few different leaves. Two techniques for measuring absorption have been used, viz. the separate determination of the diffuse reflectance and the diffuse transmittance with the leaf at a port of an integrating sphere and the direct determination of the non-absorbed fraction with the leaf in the sphere. In a cross-check both methods yielded the same results for the absorption spectrum. The spectrum of a Fuchsia leaf, covering the short-wave region from 350 to 2500 nm, shows a high absorption in UV, blue and red, the well known dip in the green and a steep fall-off at 700 nm. Absorption drops to virtually zero in the near infrared, with subsequent absorptions, corresponding to the water absorption bands. In more detailed spectra, taken at 5 nm intervals with a 5 nm bandwidth, differences in chlorophyll content show in the different depths of the dip around 550 nm and in a small shift of the absorption edge at 700 nm. Spectra for Geranium (Pelargonium zonale) and Hibiscus (with a higher chlorophyll content) show that the upper limit for photosynthesis can not be much above 700 nm. No evidence, however, is to be seen of a lower limit for photosynthesis and, in fact, some experiments down to 300 nm still did not show a decrease of the absorption although it is well recognized that no photosynthesis results with 300 nm wavelengths.

  17. Multiple DNA Interactions Contribute to the Initiation of Telomerase Elongation.

    PubMed

    Karademir Andersson, Ahu; Gustafsson, Cecilia; Krishnankutty, Roopesh; Cohn, Marita

    2017-07-07

    Telomerase maintains telomere length and chromosome integrity by adding short tandem repeats of single-stranded DNA to the 3' ends, via reverse transcription of a defined template region of its RNA subunit. To further understand the telomerase elongation mechanism, we studied the primer utilization and extension activity of the telomerase from the budding yeast Naumovozyma castellii (Saccharomyces castellii), which displays a processive nucleotide and repeat addition polymerization. For the efficient initiation of canonical elongation, telomerase required 4-nt primer 3' end complementarity to the template RNA. This DNA-RNA hybrid formation was highly important for the stabilization of an initiation-competent telomerase-DNA complex. Anchor site interactions with the DNA provided additional stabilization to the complex. Our studies indicate three additional separate interactions along the length of the DNA primer, each providing different and distinct contributions to the initiation event. A sequence-independent anchor site interaction acts immediately adjacent to the base-pairing 3' end, indicating a protein anchor site positioned very close to the catalytic site. Two additional anchor regions further 5' on the DNA provide sequence-specific contributions to the initiation of elongation. Remarkably, a non-telomeric sequence in the distal 25- to 32-nt region negatively influences the initiation of telomerase elongation, suggesting an anchor site with a regulatory role in the telomerase elongation decision. Copyright © 2017 Elsevier Ltd. All rights reserved.

  18. Correlation Between NDE Measurements and Elongation of Aluminum

    SciTech Connect

    Thompson, R. Bruce; Margetan, Frank J.; Nakagawa, Norio; Haldipur, Pranaam

    2007-03-21

    Complex aluminum forgings can have engineering properties which vary with position due to changes in the underlying local metal microstructure. Consequently, the material properties may be in compliance with production requirements in some regions of the forging, but out of compliance in others. One conical Al-7050 forging of interest was found to have elongation properties which failed required tests in certain regions. NDE measurements sensitive to microstructural changes were carried out to search for correlations with elongation properties. The results of a set of initial feasibility experiments will be reported. Both ultrasonic and eddy current NDE methods were used, with the goal being to determine which properties were sensitive to the elongation. Ultrasonic testing included the measurement of longitudinal and shear-wave velocity, longitudinal wave attenuation, and longitudinal and shear-wave backscattered grain noise. All tests were performed with the sonic beam entering through the coupon face that would be adjacent to the outer surface of the forging. Only modest differences in wave speed and attenuation values were seen among the suite of coupons, but significant differences were seen in backscattered noise levels. These appeared to indicate changes in grain structure but only exhibited partial correlation with elongation. The eddy current measurements were designed to be sensitive to the electrical resistivity. Included were a number of measurement configurations and frequencies. The signals exhibited a significant correlation with elongation.

  19. Correlation Between NDE Measurements and Elongation of Aluminum

    NASA Astrophysics Data System (ADS)

    Thompson, R. Bruce; Margetan, Frank J.; Nakagawa, Norio; Haldipur, Pranaam

    2007-03-01

    Complex aluminum forgings can have engineering properties which vary with position due to changes in the underlying local metal microstructure. Consequently, the material properties may be in compliance with production requirements in some regions of the forging, but out of compliance in others. One conical Al-7050 forging of interest was found to have elongation properties which failed required tests in certain regions. NDE measurements sensitive to microstructural changes were carried out to search for correlations with elongation properties. The results of a set of initial feasibility experiments will be reported. Both ultrasonic and eddy current NDE methods were used, with the goal being to determine which properties were sensitive to the elongation. Ultrasonic testing included the measurement of longitudinal and shear-wave velocity, longitudinal wave attenuation, and longitudinal and shear-wave backscattered grain noise. All tests were performed with the sonic beam entering through the coupon face that would be adjacent to the outer surface of the forging. Only modest differences in wave speed and attenuation values were seen among the suite of coupons, but significant differences were seen in backscattered noise levels. These appeared to indicate changes in grain structure but only exhibited partial correlation with elongation. The eddy current measurements were designed to be sensitive to the electrical resistivity. Included were a number of measurement configurations and frequencies. The signals exhibited a significant correlation with elongation.

  20. Using the conservative nature of fresh leaf surface density to measure foliar area

    NASA Astrophysics Data System (ADS)

    Castillo, Omar S.; Zaragoza, Esther M.; Alvarado, Carlos J.; Barrera, Maria G.; Dasgupta-Schubert, Nabanita

    2014-10-01

    For a herbaceous species, the inverse of the fresh leaf surface density, the Hughes constant, is nearly conserved. We apply the Hughes constant to develop an absolute method of leafarea measurement that requires no regression fits, prior calibrations or oven-drying. The Hughes constant was determined in situ using a known geometry and weights of a sub-set obtained from the fresh leaves whose areas are desired. Subsequently, the leaf-areas (at any desired stratification level), were derived by utilizing the Hughes constant and the masses of the fresh leaves. The proof of concept was established for leaf-discs of the plants Mandevilla splendens and Spathiphyllum wallisii. The conservativeness of the Hughes constant over individual leaf-zones and different leaftypes from the leaves of each species was quantitatively validated. Using the globally averaged Hughes constant for each species, the leaf-area of these and additional co-species plants, were obtained. The leaf-area-measurement-by-mass was cross-checked with standard digital image analysis. There were no statistically significant differences between the leaf-area-measurement-by-mass and the digital image analysis measured leaf-areas and the linear correlation between the two methods was very good. Leaf-areameasurement- by-mass was found to be rapid and simple with accuracies comparable to the digital image analysis method. The greatly reduced cost of leaf-area-measurement-by-mass could be beneficial for small agri-businesses in developing countries.

  1. GhCaM7-like, a calcium sensor gene, influences cotton fiber elongation and biomass production.

    PubMed

    Cheng, Yuan; Lu, Lili; Yang, Zhaoen; Wu, Zhixia; Qin, Wenqiang; Yu, Daoqian; Ren, Zhongying; Li, Yi; Wang, Lingling; Li, Fuguang; Yang, Zuoren

    2016-12-01

    Calcium signaling regulates many developmental processes in plants. Calmodulin (CaM) is one of the most conserved calcium sensors and has a flexible conformation in eukaryotes. The molecular functions of CaM are unknown in cotton, which is a major source of natural fiber. In this study, a Gossypium hirsutum L.CaM7-like gene was isolated from upland cotton. Bioinformatics analysis indicated that the GhCaM7-like gene was highly conserved as compared with Arabidopsis AtCaM7. The GhCaM7-like gene showed a high expression level in elongating fibers. Expression of β-glucuronidase was observed in trichomes on the stem, leaf and root in transgenic Arabidopsis plants of a PROGhCaM7-like:GUS fusion. Silencing of the GhCaM7-like gene resulted in decreased fiber length, but also caused reduction in stem height, leaf dimensions, seed length and 100-seed weight, in comparison with those of the control. Reduced expression of the GhCaM7-like gene caused decreased Ca(2+) influx in cells of the leaf hypodermis and stem apex, and down-regulation of GhIQD1 (IQ67-domain containing protein), GhAnn2 (Annexins) and GhEXP2 (Expansin). These results indicate that the GhCaM7-like gene plays a vital role in calcium signaling pathways, and may regulate cotton fiber elongation and biomass production by affecting Ca(2+) signatures and downstream signaling pathways of CaM. Copyright © 2016 Elsevier Masson SAS. All rights reserved.

  2. Association study between the gibberellic acid insensitive gene and leaf length in a Lolium perenne L. synthetic variety.

    PubMed

    Auzanneau, Jérôme; Huyghe, Christian; Escobar-Gutiérrez, Abraham J; Julier, Bernadette; Gastal, François; Barre, Philippe

    2011-12-28

    Association studies are of great interest to identify genes explaining trait variation since they deal with more than just a few alleles like classical QTL analyses. They are usually performed using collections representing a wide range of variability but which could present a genetic substructure. The aim of this paper is to demonstrate that association studies can be performed using synthetic varieties obtained after several panmictic generations. This demonstration is based on an example of association between the gibberellic acid insensitive gene (GAI) polymorphism and leaf length polymorphism in 'Herbie', a synthetic variety of perennial ryegrass. Leaf growth parameters, consisted of leaf length, maximum leaf elongation rate (LERmax) and leaf elongation duration (LED), were evaluated in spring and autumn on 216 plants of Herbie with three replicates. For each plant, a sequence of 370 bp in GAI was analysed for polymorphism. Genetic effect was highly significant for all traits. Broad sense heritabilities were higher for leaf length and LERmax with about 0.7 in each period and 0.5 considering both periods than for LED with about 0.4 in each period and 0.3 considering both periods. GAI was highly polymorphic with an average of 12 bp between two consecutive SNPs and 39 haplotypes in which 9 were more frequent. Linkage disequilibrium declined rapidly with distance with r 2 values lower than 0.2 beyond 150 bp. Sequence polymorphism of GAI explained 8-14% of leaf growth parameter variation. A single SNP explained 4% of the phenotypic variance of leaf length in both periods which represents a difference of 33 mm on an average of 300 mm. Synthetic varieties in which linkage disequilibrium declines rapidly with distance are suitable for association studies using the "candidate gene" approach. GAI polymorphism was found to be associated with leaf length polymorphism which was more correlated to LERmax than to LED in Herbie. It is a good candidate to explain leaf length

  3. Developmentally distinct activities of the exocyst enable rapid cell elongation and determine meristem size during primary root growth in Arabidopsis.

    PubMed

    Cole, Rex A; McInally, Samantha A; Fowler, John E

    2014-12-31

    Exocytosis is integral to root growth: trafficking components of systems that control growth (e.g., PIN auxin transport proteins) to the plasma membrane, and secreting materials that expand the cell wall to the apoplast. Spatiotemporal regulation of exocytosis in eukaryotes often involves the exocyst, an octameric complex that tethers selected secretory vesicles to specific sites on the plasma membrane and facilitates their exocytosis. We evaluated Arabidopsis lines with mutations in four exocyst components (SEC5, SEC8, EXO70A1 and EXO84B) to explore exocyst function in primary root growth. The mutants have root growth rates that are 82% to 11% of wild-type. Even in lines with the most severe defects, the organization of the quiescent center and tissue layers at the root tips appears similar to wild-type, although meristematic, transition, and elongation zones are shorter. Reduced cell production rates in the mutants are due to the shorter meristems, but not to lengthened cell cycles. Additionally, mutants demonstrate reduced anisotropic cell expansion in the elongation zone, but not the meristematic zone, resulting in shorter mature cells that are similar in shape to wild-type. As expected, hypersensitivity to brefeldin A links the mutant root growth defect to altered vesicular trafficking. Several experimental approaches (e.g., dose-response measurements, localization of signaling components) failed to identify aberrant auxin or brassinosteroid signaling as a primary driver for reduced root growth in exocyst mutants. The exocyst participates in two spatially distinct developmental processes, apparently by mechanisms not directly linked to auxin or brassinosteroid signaling pathways, to help establish root meristem size, and to facilitate rapid cell expansion in the elongation zone.

  4. Leaf gas films, underwater photosynthesis and plant species distributions in a flood gradient.

    PubMed

    Winkel, Anders; Visser, Eric J W; Colmer, Timothy D; Brodersen, Klaus P; Voesenek, Laurentius A C J; Sand-Jensen, Kaj; Pedersen, Ole

    2016-07-01

    Traits for survival during flooding of terrestrial plants include stimulation or inhibition of shoot elongation, aerenchyma formation and efficient gas exchange. Leaf gas films form on superhydrophobic cuticles during submergence and enhance underwater gas exchange. The main hypothesis tested was that the presence of leaf gas films influences the distribution of plant species along a natural flood gradient. We conducted laboratory experiments and field observations on species distributed along a natural flood gradient. We measured presence or absence of leaf gas films and specific leaf area of 95 species. We also measured, gas film retention time during submergence and underwater net photosynthesis and dark respiration of 25 target species. The presence of a leaf gas film was inversely correlated to flood frequency and duration and reached a maximum value of 80% of the species in the rarely flooded locations. This relationship was primarily driven by grasses that all, independently of their field location along the flood gradient, possess gas films when submerged. Although the present study and earlier experiments have shown that leaf gas films enhance gas exchange of submerged plants, the ability of species to form leaf gas films did not show the hypothesized relationship with species composition along the flood gradient.

  5. Hox genes control vertebrate body elongation by collinear Wnt repression.

    PubMed

    Denans, Nicolas; Iimura, Tadahiro; Pourquié, Olivier

    2015-02-26

    In vertebrates, the total number of vertebrae is precisely defined. Vertebrae derive from embryonic somites that are continuously produced posteriorly from the presomitic mesoderm (PSM) during body formation. We show that in the chicken embryo, activation of posterior Hox genes (paralogs 9-13) in the tail-bud correlates with the slowing down of axis elongation. Our data indicate that a subset of progressively more posterior Hox genes, which are collinearly activated in vertebral precursors, repress Wnt activity with increasing strength. This leads to a graded repression of the Brachyury/T transcription factor, reducing mesoderm ingression and slowing down the elongation process. Due to the continuation of somite formation, this mechanism leads to the progressive reduction of PSM size. This ultimately brings the retinoic acid (RA)-producing segmented region in close vicinity to the tail bud, potentially accounting for the termination of segmentation and axis elongation.

  6. Elongate summit calderas as Neogene paleostress indicators in Antarctica

    USGS Publications Warehouse

    Paulsen, T.S.; Wilson, T.J.

    2007-01-01

    The orientations and ages of elongate summit calderas on major polygenetic volcanoes were compiled to document Miocene to Pleistocene Sh (minimum horizontal stress) directions on the western and northern flanks of the West Antarctic rift system. Miocene to Pleistocene summit calderas along the western Ross Sea show relatively consistent ENE long axis trends, which are at a high angle to the Transantarctic Mountain Front and parallel to the N77ºE Sh direction at Cape Roberts. The elongation directions of many Miocene to Pleistocene summit calderas in Marie Byrd Land parallel the alignment of polygenetic volcanoes in which they occur, except several Pleistocene calderas with consistent NNE to NE trends. The overall pattern of elongate calderas in Marie Byrd Land is probably due to a combination of structurally controlled orientations and regional stress fields in which Sh is oriented NNE to NE at a moderate to high angle to the trace of the West Antarctic rift system.

  7. Bilateral elongated mandibular coronoid process in an Anatolian skull

    PubMed Central

    Çorumlu, Ufuk; Demir, Mehmet Tevfik; Pirzirenli, Mennan Ece

    2016-01-01

    Elongation or hyperplasia of coronoid process of mandible is rare condition characterized by abnormal bone development which cause malocclusion and the limited mouth opening. In this study, in an Anatolian skull, a case of bilateral elongation of mandibular coronoid process was presented. Levandoski panographic analysis was performed on the panoramic radiographie to determine the hyperplasia of the coronoid process. The right condylar process was exactly hyperplastic. The measurements of Kr-Go/Cd-Go were 95.10 mm/79.03 mm on right side and 97.53 mm/87.80 mm on left side. The ratio of Kr-Go/Cd-Go on the right side was 1.20. Elongated coronoid process is one of the factors cause mandibular hypomobility, it as reported here might lead to limited mouth opening. The knowledge of this variation or abnormality can be useful for the radiologist and surgeons and prevent misdiagnosis. PMID:27722017

  8. An Elongated Tetrakaidecahedron Model for Open-Celled Foams

    NASA Technical Reports Server (NTRS)

    Sullivan, Roy M.; Ghosn, Louis J.; Lerch, Bradley A.

    2007-01-01

    A micro-mechanics model for non-isotropic, open-celled foams is developed using an elongated tetrakaidecahedron (Kelvin model) as the repeating unit cell. The micro-mechanics model employs an elongated Kelvin model geometry which is more general than that employed by previous authors. Assuming the cell edges possess axial and bending rigidity, the mechanics of deformation of the elongated tetrakaidecahedron lead to a set of equations for the Young's modulus, Poisson's ratio and strength of the foam in the principal material directions. These equations are written as a function of the cell edge lengths and cross-section properties, the inclination angle and the strength and stiffness of the solid material. The model is applied to predict the strength and stiffness of several polymeric foams. Good agreement is observed between the model results and the experimental measurements.

  9. How slow RNA polymerase II elongation favors alternative exon skipping.

    PubMed

    Dujardin, Gwendal; Lafaille, Celina; de la Mata, Manuel; Marasco, Luciano E; Muñoz, Manuel J; Le Jossic-Corcos, Catherine; Corcos, Laurent; Kornblihtt, Alberto R

    2014-05-22

    Splicing is functionally coupled to transcription, linking the rate of RNA polymerase II (Pol II) elongation and the ability of splicing factors to recognize splice sites (ss) of various strengths. In most cases, slow Pol II elongation allows weak splice sites to be recognized, leading to higher inclusion of alternative exons. Using CFTR alternative exon 9 (E9) as a model, we show here that slowing down elongation can also cause exon skipping by promoting the recruitment of the negative factor ETR-3 onto the UG-repeat at E9 3' splice site, which displaces the constitutive splicing factor U2AF65 from the overlapping polypyrimidine tract. Weakening of E9 5' ss increases ETR-3 binding at the 3' ss and subsequent E9 skipping, whereas strengthening of the 5' ss usage has the opposite effect. This indicates that a delay in the cotranscriptional emergence of the 5' ss promotes ETR-3 recruitment and subsequent inhibition of E9 inclusion.

  10. Elongation effects on the Therac 6 linear accelerator.

    PubMed

    Dawson, D J

    1978-01-01

    The effects of field elongation on the central-axis output at dmax and on the depth-dose curves for the 6-MV x rays from the Therac 6 linear accelerator are considered. These parameters are independent of the collimator angle for both square and elongated fields. The exchange of collimator pairs results in significant output differences but has a negligible effect on the depth-dose curves. Both the central-axis output at dmax and the depth-dose curves agree satisfactorily with the predictions of the equivalent-square technique. An alternative method of greater accuracy is also indicated for the prediction of central-axis outputs at dmax for elongated fields.

  11. Progressive cis-inhibition of telomerase upon telomere elongation.

    PubMed Central

    Marcand, S; Brevet, V; Gilson, E

    1999-01-01

    In yeast, the constant length of telomeric DNA results from a negative regulation of telomerase by the telomere itself. Here we follow the return to equilibrium of an abnormally shortened telomere. We observe that telomere elongation is restricted to a few base pairs per generation and that its rate decreases progressively with increasing telomere length. In contrast, in the absence of telomerase or in the presence of an over-elongated telomere, the degradation rate linked to the succession of generations appears to be constant, i.e. independent of telomere length. Together, these results indicate that telomerase is gradually inhibited at its site of action by the elongating telomere. The implications of this finding for the dynamics of telomere length regulation are discussed in this study. PMID:10369690

  12. Break-induced replication and recombinational telomere elongation in yeast.

    PubMed

    McEachern, Michael J; Haber, James E

    2006-01-01

    When a telomere becomes unprotected or if only one end of a chromosomal double-strand break succeeds in recombining with a template sequence, DNA can be repaired by a recombination-dependent DNA replication process termed break-induced replication (BIR). In budding yeasts, there are two BIR pathways, one dependent on the Rad51 recombinase protein and one Rad51 independent; these two repair processes lead to different types of survivors in cells lacking the telomerase enzyme that is required for normal telomere maintenance. Recombination at telomeres is triggered by either excessive telomere shortening or disruptions in the function of telomere-binding proteins. Telomere elongation by BIR appears to often occur through a "roll and spread" mechanism. In this process, a telomeric circle produced by recombination at a dysfunctional telomere acts as a template for a rolling circle BIR event to form an elongated telomere. Additional BIR events can then copy the elongated sequence to all other telomeres.

  13. Elongation measurement using 1-dimensional image correlation method

    NASA Astrophysics Data System (ADS)

    Phongwisit, Phachara; Kamoldilok, Surachart; Buranasiri, Prathan

    2016-11-01

    Aim of this paper was to study, setup, and calibrate an elongation measurement by using 1- Dimensional Image Correlation method (1-DIC). To confirm our method and setup correctness, we need calibration with other methods. In this paper, we used a small spring as a sample to find a result in terms of spring constant. With a fundamental of Image Correlation method, images of formed and deformed samples were compared to understand the difference between deformed process. By comparing the location of reference point on both image's pixel, the spring's elongation were calculated. Then, the results have been compared with the spring constants, which were found from Hooke's law. The percentage of 5 percent error has been found. This DIC method, then, would be applied to measure the elongation of some different kinds of small fiber samples.

  14. Expression of TWISTED DWARF1 lacking its in-plane membrane anchor leads to increased cell elongation and hypermorphic growth.

    PubMed

    Bailly, Aurélien; Wang, Bangjun; Zwiewka, Marta; Pollmann, Stephan; Schenck, Daniel; Lüthen, Hartwig; Schulz, Alexander; Friml, Jiri; Geisler, Markus

    2014-01-01

    Plant growth is achieved predominantly by cellular elongation, which is thought to be controlled on several levels by apoplastic auxin. Auxin export into the apoplast is achieved by plasma membrane efflux catalysts of the PIN-FORMED (PIN) and ATP-binding cassette protein subfamily B/phosphor-glycoprotein (ABCB/PGP) classes; the latter were shown to depend on interaction with the FKBP42, TWISTED DWARF1 (TWD1). Here by using a transgenic approach in combination with phenotypical, biochemical and cell biological analyses we demonstrate the importance of a putative C-terminal in-plane membrane anchor of TWD1 in the regulation of ABCB-mediated auxin transport. In contrast with dwarfed twd1 loss-of-function alleles, TWD1 gain-of-function lines that lack a putative in-plane membrane anchor (HA-TWD1-Ct ) show hypermorphic plant architecture, characterized by enhanced stem length and leaf surface but reduced shoot branching. Greater hypocotyl length is the result of enhanced cell elongation that correlates with reduced polar auxin transport capacity for HA-TWD1-Ct . As a consequence, HA-TWD1-Ct displays higher hypocotyl auxin accumulation, which is shown to result in elevated auxin-induced cell elongation rates. Our data highlight the importance of C-terminal membrane anchoring for TWD1 action, which is required for specific regulation of ABCB-mediated auxin transport. These data support a model in which TWD1 controls lateral ABCB1-mediated export into the apoplast, which is required for auxin-mediated cell elongation.

  15. Reversible stalling of transcription elongation complexes by high pressure.

    PubMed

    Erijman, L; Clegg, R M

    1998-07-01

    We have investigated the effect of high hydrostatic pressure on the stability of RNA polymerase molecules during transcription. RNA polymerase molecules participating in stalled or active ternary transcribing complexes do not dissociate from the template DNA and nascent RNA at pressures up to 180 MPa. A lower limit for the free energy of stabilization of an elongating ternary complex relative to the quaternary structure of the free RNAP molecules is estimated to be 20 kcal/mol. The rate of elongation decreases at high pressure; transcription completely halts at sufficiently high pressure. The overall rate of elongation has an apparent activation volume (DeltaVdouble dagger) of 55-65 ml . mol-1 (at 35 degrees C). The pressure-stalled transcripts are stable and resume elongation at the prepressure rate upon decompression. The efficiency of termination decreases at the rho-independent terminator tR2 after the transcription reaction has been exposed to high pressure. This suggests that high pressure modifies the ternary complex such that termination is affected in a manner different from that of elongation. The solvent and temperature dependence of the pressure-induced inhibition show evidence for major conformational changes in the core polymerase enzyme during RNA synthesis. It is proposed that the inhibition of the elongation phase of the transcription reaction at elevated pressures is related to a reduction of the partial specific volume of the RNA polymerase molecule; under high pressure, the RNA polymerase molecule does not have the necessary structural flexibility required for the protein to translocate.

  16. Rotation in Free Fall of Rectangular Wings of Elongated Shape

    NASA Technical Reports Server (NTRS)

    Dupleich, Paul

    1949-01-01

    The present report of Mr. Dupleich is the summary of a very extensive experimental study of the well-known mechanical phenomenon: the rotation in free fall (* air, for instance) of more or less elongated rectangles cut out of paper or pasteboard. This phenomenon, the conditions for existence of which depend chiefly on the elongated of the small plate and its weight per unit area, is essentially an aerodynamic phenomenon and as such, raises questions of a certain interest to our department.We believe that the modern concepts of the mechanics of fluids do not have the range attributed to them.

  17. The worldwide leaf economics spectrum.

    PubMed

    Wright, Ian J; Reich, Peter B; Westoby, Mark; Ackerly, David D; Baruch, Zdravko; Bongers, Frans; Cavender-Bares, Jeannine; Chapin, Terry; Cornelissen, Johannes H C; Diemer, Matthias; Flexas, Jaume; Garnier, Eric; Groom, Philip K; Gulias, Javier; Hikosaka, Kouki; Lamont, Byron B; Lee, Tali; Lee, William; Lusk, Christopher; Midgley, Jeremy J; Navas, Marie-Laure; Niinemets, Ulo; Oleksyn, Jacek; Osada, Noriyuki; Poorter, Hendrik; Poot, Pieter; Prior, Lynda; Pyankov, Vladimir I; Roumet, Catherine; Thomas, Sean C; Tjoelker, Mark G; Veneklaas, Erik J; Villar, Rafael

    2004-04-22

    Bringing together leaf trait data spanning 2,548 species and 175 sites we describe, for the first time at global scale, a universal spectrum of leaf economics consisting of key chemical, structural and physiological properties. The spectrum runs from quick to slow return on investments of nutrients and dry mass in leaves, and operates largely independently of growth form, plant functional type or biome. Categories along the spectrum would, in general, describe leaf economic variation at the global scale better than plant functional types, because functional types overlap substantially in their leaf traits. Overall, modulation of leaf traits and trait relationships by climate is surprisingly modest, although some striking and significant patterns can be seen. Reliable quantification of the leaf economics spectrum and its interaction with climate will prove valuable for modelling nutrient fluxes and vegetation boundaries under changing land-use and climate.

  18. Vertex-element models for anisotropic growth of elongated plant organs

    PubMed Central

    Fozard, John A.; Lucas, Mikaël; King, John R.; Jensen, Oliver E.

    2013-01-01

    New tools are required to address the challenge of relating plant hormone levels, hormone responses, wall biochemistry and wall mechanical properties to organ-scale growth. Current vertex-based models (applied in other contexts) can be unsuitable for simulating the growth of elongated organs such as roots because of the large aspect ratio of the cells, and these models fail to capture the mechanical properties of cell walls in sufficient detail. We describe a vertex-element model which resolves individual cells and includes anisotropic non-linear viscoelastic mechanical properties of cell walls and cell division whilst still being computationally efficient. We show that detailed consideration of the cell walls in the plane of a 2D simulation is necessary when cells have large aspect ratio, such as those in the root elongation zone of Arabidopsis thaliana, in order to avoid anomalous transverse swelling. We explore how differences in the mechanical properties of cells across an organ can result in bending and how cellulose microfibril orientation affects macroscale growth. We also demonstrate that the model can be used to simulate growth on realistic geometries, for example that of the primary root apex, using moderate computational resources. The model shows how macroscopic root shape can be sensitive to fine-scale cellular geometries. PMID:23847638

  19. Posterior elongation in the annelid Platynereis dumerilii involves stem cells molecularly related to primordial germ cells.

    PubMed

    Gazave, Eve; Béhague, Julien; Laplane, Lucie; Guillou, Aurélien; Préau, Laetitia; Demilly, Adrien; Balavoine, Guillaume; Vervoort, Michel

    2013-10-01

    Like most bilaterian animals, the annelid Platynereis dumerilii generates the majority of its body axis in an anterior to posterior temporal progression with new segments added sequentially. This process relies on a posterior subterminal proliferative body region, known as the "segment addition zone" (SAZ). We explored some of the molecular and cellular aspects of posterior elongation in Platynereis, in particular to test the hypothesis that the SAZ contains a specific set of stem cells dedicated to posterior elongation. We cloned and characterized the developmental expression patterns of orthologs of 17 genes known to be involved in the formation, behavior, or maintenance of stem cells in other metazoan models. These genes encode RNA-binding proteins (e.g., tudor, musashi, pumilio) or transcription factors (e.g., myc, id, runx) widely conserved in eumetazoans. Most of these genes are expressed both in the migrating primordial germ cells and in overlapping ring-like patterns in the SAZ, similar to some previously analyzed genes (piwi, vasa). The SAZ patterns are coincident with the expression of proliferation markers cyclin B and PCNA. EdU pulse and chase experiments suggest that new segments are produced through many rounds of divisions from small populations of teloblast-like posterior stem cells. The shared molecular signature between primordial germ cells and posterior stem cells in Platynereis thus corresponds to an ancestral "stemness" program. © 2013 Elsevier Inc. All rights reserved.

  20. Low phosphate activates STOP1-ALMT1 to rapidly inhibit root cell elongation

    PubMed Central

    Balzergue, Coline; Dartevelle, Thibault; Godon, Christian; Laugier, Edith; Meisrimler, Claudia; Teulon, Jean-Marie; Creff, Audrey; Bissler, Marie; Brouchoud, Corinne; Hagège, Agnès; Müller, Jens; Chiarenza, Serge; Javot, Hélène; Becuwe-Linka, Noëlle; David, Pascale; Péret, Benjamin; Delannoy, Etienne; Thibaud, Marie-Christine; Armengaud, Jean; Abel, Steffen; Pellequer, Jean-Luc; Nussaume, Laurent; Desnos, Thierry

    2017-01-01

    Environmental cues profoundly modulate cell proliferation and cell elongation to inform and direct plant growth and development. External phosphate (Pi) limitation inhibits primary root growth in many plant species. However, the underlying Pi sensory mechanisms are unknown. Here we genetically uncouple two Pi sensing pathways in the root apex of Arabidopsis thaliana. First, the rapid inhibition of cell elongation in the transition zone is controlled by transcription factor STOP1, by its direct target, ALMT1, encoding a malate channel, and by ferroxidase LPR1, which together mediate Fe and peroxidase-dependent cell wall stiffening. Second, during the subsequent slow inhibition of cell proliferation in the apical meristem, which is mediated by LPR1-dependent, but largely STOP1–ALMT1-independent, Fe and callose accumulate in the stem cell niche, leading to meristem reduction. Our work uncovers STOP1 and ALMT1 as a signalling pathway of low Pi availability and exuded malate as an unexpected apoplastic inhibitor of root cell wall expansion. PMID:28504266

  1. Ethylene Inhibits Root Elongation during Alkaline Stress through AUXIN1 and Associated Changes in Auxin Accumulation1

    PubMed Central

    Li, Juan; Xu, Heng-Hao; Liu, Wen-Cheng; Zhang, Xiao-Wei

    2015-01-01

    Soil alkalinity causes major reductions in yield and quality of crops worldwide. The plant root is the first organ sensing soil alkalinity, which results in shorter primary roots. However, the mechanism underlying alkaline stress-mediated inhibition of root elongation remains to be further elucidated. Here, we report that alkaline conditions inhibit primary root elongation of Arabidopsis (Arabidopsis thaliana) seedlings by reducing cell division potential in the meristem zones and that ethylene signaling affects this process. The ethylene perception antagonist silver (Ag+) alleviated the inhibition of root elongation by alkaline stress. Moreover, the ethylene signaling mutants ethylene response1-3 (etr1-3), ethylene insensitive2 (ein2), and ein3-1 showed less reduction in root length under alkaline conditions, indicating a reduced sensitivity to alkalinity. Ethylene biosynthesis also was found to play a role in alkaline stress-mediated root inhibition; the ethylene overproducer1-1 mutant, which overproduces ethylene because of increased stability of 1-AMINOCYCLOPROPANE-1-CARBOXYLIC ACID SYNTHASE5, was hypersensitive to alkaline stress. In addition, the ethylene biosynthesis inhibitor cobalt (Co2+) suppressed alkaline stress-mediated inhibition of root elongation. We further found that alkaline stress caused an increase in auxin levels by promoting expression of auxin biosynthesis-related genes, but the increase in auxin levels was reduced in the roots of the etr1-3 and ein3-1 mutants and in Ag+/Co2+-treated wild-type plants. Additional genetic and physiological data showed that AUXIN1 (AUX1) was involved in alkaline stress-mediated inhibition of root elongation. Taken together, our results reveal that ethylene modulates alkaline stress-mediated inhibition of root growth by increasing auxin accumulation by stimulating the expression of AUX1 and auxin biosynthesis-related genes. PMID:26109425

  2. Leaf Dynamics of Panicum maximum under Future Climatic Changes.

    PubMed

    Britto de Assis Prado, Carlos Henrique; Haik Guedes de Camargo-Bortolin, Lívia; Castro, Érique; Martinez, Carlos Alberto

    2016-01-01

    Panicum maximum Jacq. 'Mombaça' (C4) was grown in field conditions with sufficient water and nutrients to examine the effects of warming and elevated CO2 concentrations during the winter. Plants were exposed to either the ambient temperature and regular atmospheric CO2 (Control); elevated CO2 (600 ppm, eC); canopy warming (+2°C above regular canopy temperature, eT); or elevated CO2 and canopy warming (eC+eT). The temperatures and CO2 in the field were controlled by temperature free-air controlled enhancement (T-FACE) and mini free-air CO2 enrichment (miniFACE) facilities. The most green, expanding, and expanded leaves and the highest leaf appearance rate (LAR, leaves day(-1)) and leaf elongation rate (LER, cm day(-1)) were observed under eT. Leaf area and leaf biomass were higher in the eT and eC+eT treatments. The higher LER and LAR without significant differences in the number of senescent leaves could explain why tillers had higher foliage area and leaf biomass in the eT treatment. The eC treatment had the lowest LER and the fewest expanded and green leaves, similar to Control. The inhibitory effect of eC on foliage development in winter was indicated by the fewer green, expanded, and expanding leaves under eC+eT than eT. The stimulatory and inhibitory effects of the eT and eC treatments, respectively, on foliage raised and lowered, respectively, the foliar nitrogen concentration. The inhibition of foliage by eC was confirmed by the eC treatment having the lowest leaf/stem biomass ratio and by the change in leaf biomass-area relationships from linear or exponential growth to rectangular hyperbolic growth under eC. Besides, eC+eT had a synergist effect, speeding up leaf maturation. Therefore, with sufficient water and nutrients in winter, the inhibitory effect of elevated CO2 on foliage could be partially offset by elevated temperatures and relatively high P. maximum foliage production could be achieved under future climatic change.

  3. Leaf Dynamics of Panicum maximum under Future Climatic Changes

    PubMed Central

    Britto de Assis Prado, Carlos Henrique; Haik Guedes de Camargo-Bortolin, Lívia; Castro, Érique; Martinez, Carlos Alberto

    2016-01-01

    Panicum maximum Jacq. ‘Mombaça’ (C4) was grown in field conditions with sufficient water and nutrients to examine the effects of warming and elevated CO2 concentrations during the winter. Plants were exposed to either the ambient temperature and regular atmospheric CO2 (Control); elevated CO2 (600 ppm, eC); canopy warming (+2°C above regular canopy temperature, eT); or elevated CO2 and canopy warming (eC+eT). The temperatures and CO2 in the field were controlled by temperature free-air controlled enhancement (T-FACE) and mini free-air CO2 enrichment (miniFACE) facilities. The most green, expanding, and expanded leaves and the highest leaf appearance rate (LAR, leaves day-1) and leaf elongation rate (LER, cm day-1) were observed under eT. Leaf area and leaf biomass were higher in the eT and eC+eT treatments. The higher LER and LAR without significant differences in the number of senescent leaves could explain why tillers had higher foliage area and leaf biomass in the eT treatment. The eC treatment had the lowest LER and the fewest expanded and green leaves, similar to Control. The inhibitory effect of eC on foliage development in winter was indicated by the fewer green, expanded, and expanding leaves under eC+eT than eT. The stimulatory and inhibitory effects of the eT and eC treatments, respectively, on foliage raised and lowered, respectively, the foliar nitrogen concentration. The inhibition of foliage by eC was confirmed by the eC treatment having the lowest leaf/stem biomass ratio and by the change in leaf biomass-area relationships from linear or exponential growth to rectangular hyperbolic growth under eC. Besides, eC+eT had a synergist effect, speeding up leaf maturation. Therefore, with sufficient water and nutrients in winter, the inhibitory effect of elevated CO2 on foliage could be partially offset by elevated temperatures and relatively high P. maximum foliage production could be achieved under future climatic change. PMID:26894932

  4. Leaf development: a cellular perspective

    PubMed Central

    Kalve, Shweta; De Vos, Dirk; Beemster, Gerrit T. S.

    2014-01-01

    Through its photosynthetic capacity the leaf provides the basis for growth of the whole plant. In order to improve crops for higher productivity and resistance for future climate scenarios, it is important to obtain a mechanistic understanding of leaf growth and development and the effect of genetic and environmental factors on the process. Cells are both the basic building blocks of the leaf and the regulatory units that integrate genetic and environmental information into the developmental program. Therefore, to fundamentally understand leaf development, one needs to be able to reconstruct the developmental pathway of individual cells (and their progeny) from the stem cell niche to their final position in the mature leaf. To build the basis for such understanding, we review current knowledge on the spatial and temporal regulation mechanisms operating on cells, contributing to the formation of a leaf. We focus on the molecular networks that control exit from stem cell fate, leaf initiation, polarity, cytoplasmic growth, cell division, endoreduplication, transition between division and expansion, expansion and differentiation and their regulation by intercellular signaling molecules, including plant hormones, sugars, peptides, proteins, and microRNAs. We discuss to what extent the knowledge available in the literature is suitable to be applied in systems biology approaches to model the process of leaf growth, in order to better understand and predict leaf growth starting with the model species Arabidopsis thaliana. PMID:25132838

  5. 7 CFR 29.3033 - Leaf.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Leaf. 29.3033 Section 29.3033 Agriculture Regulations... Leaf. Whole, unstemmed leaf. Leaf, when applied to tobacco in strip form, shall describe the divided unit of a whole leaf. [49 FR 16758, Apr. 20, 1984] ...

  6. 7 CFR 29.3525 - Leaf.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 2 2011-01-01 2011-01-01 false Leaf. 29.3525 Section 29.3525 Agriculture Regulations... Type 95) § 29.3525 Leaf. Whole, unstemmed leaf. Leaf, when applied to tobacco in strip form, shall describe the divided unit of a whole leaf. [49 FR 16759, Apr. 20, 1984] ...

  7. 7 CFR 29.3033 - Leaf.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 2 2014-01-01 2014-01-01 false Leaf. 29.3033 Section 29.3033 Agriculture Regulations... Leaf. Whole, unstemmed leaf. Leaf, when applied to tobacco in strip form, shall describe the divided unit of a whole leaf. ...

  8. 7 CFR 29.3525 - Leaf.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 2 2014-01-01 2014-01-01 false Leaf. 29.3525 Section 29.3525 Agriculture Regulations... Type 95) § 29.3525 Leaf. Whole, unstemmed leaf. Leaf, when applied to tobacco in strip form, shall describe the divided unit of a whole leaf. ...

  9. 7 CFR 29.3525 - Leaf.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 2 2012-01-01 2012-01-01 false Leaf. 29.3525 Section 29.3525 Agriculture Regulations... Type 95) § 29.3525 Leaf. Whole, unstemmed leaf. Leaf, when applied to tobacco in strip form, shall describe the divided unit of a whole leaf. [49 FR 16759, Apr. 20, 1984] ...

  10. 7 CFR 29.1028 - Leaf.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 2 2014-01-01 2014-01-01 false Leaf. 29.1028 Section 29.1028 Agriculture Regulations... Type 92) § 29.1028 Leaf. Whole, unstemmed leaf. Leaf, when applied to tobacco in strip form, shall describe the divided unit of a whole leaf. ...

  11. 7 CFR 29.3033 - Leaf.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 2 2012-01-01 2012-01-01 false Leaf. 29.3033 Section 29.3033 Agriculture Regulations... Leaf. Whole, unstemmed leaf. Leaf, when applied to tobacco in strip form, shall describe the divided unit of a whole leaf. [49 FR 16758, Apr. 20, 1984] ...

  12. 7 CFR 29.3033 - Leaf.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 2 2013-01-01 2013-01-01 false Leaf. 29.3033 Section 29.3033 Agriculture Regulations... Leaf. Whole, unstemmed leaf. Leaf, when applied to tobacco in strip form, shall describe the divided unit of a whole leaf. ...

  13. 7 CFR 29.3033 - Leaf.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 2 2011-01-01 2011-01-01 false Leaf. 29.3033 Section 29.3033 Agriculture Regulations... Leaf. Whole, unstemmed leaf. Leaf, when applied to tobacco in strip form, shall describe the divided unit of a whole leaf. [49 FR 16758, Apr. 20, 1984] ...

  14. 7 CFR 29.2528 - Leaf.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 2 2013-01-01 2013-01-01 false Leaf. 29.2528 Section 29.2528 Agriculture Regulations...-Cured Tobacco (u.s. Types 22, 23, and Foreign Type 96) § 29.2528 Leaf. Whole, unstemmed leaf. Leaf, when applied to tobacco in strip form, shall describe the divided unit of a whole leaf. ...

  15. 7 CFR 29.1028 - Leaf.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Leaf. 29.1028 Section 29.1028 Agriculture Regulations... Type 92) § 29.1028 Leaf. Whole, unstemmed leaf. Leaf, when applied to tobacco in strip form, shall describe the divided unit of a whole leaf. [49 FR 16755, Apr. 20, 1984. Redesignated at 51 FR 25027, July...

  16. 7 CFR 29.1028 - Leaf.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 2 2011-01-01 2011-01-01 false Leaf. 29.1028 Section 29.1028 Agriculture Regulations... Type 92) § 29.1028 Leaf. Whole, unstemmed leaf. Leaf, when applied to tobacco in strip form, shall describe the divided unit of a whole leaf. [49 FR 16755, Apr. 20, 1984. Redesignated at 51 FR 25027, July...

  17. 7 CFR 29.3525 - Leaf.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 2 2013-01-01 2013-01-01 false Leaf. 29.3525 Section 29.3525 Agriculture Regulations... Type 95) § 29.3525 Leaf. Whole, unstemmed leaf. Leaf, when applied to tobacco in strip form, shall describe the divided unit of a whole leaf. ...

  18. 7 CFR 29.1028 - Leaf.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 2 2013-01-01 2013-01-01 false Leaf. 29.1028 Section 29.1028 Agriculture Regulations... Type 92) § 29.1028 Leaf. Whole, unstemmed leaf. Leaf, when applied to tobacco in strip form, shall describe the divided unit of a whole leaf. ...

  19. 7 CFR 29.3525 - Leaf.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Leaf. 29.3525 Section 29.3525 Agriculture Regulations... Type 95) § 29.3525 Leaf. Whole, unstemmed leaf. Leaf, when applied to tobacco in strip form, shall describe the divided unit of a whole leaf. [49 FR 16759, Apr. 20, 1984] ...

  20. 7 CFR 29.1028 - Leaf.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 2 2012-01-01 2012-01-01 false Leaf. 29.1028 Section 29.1028 Agriculture Regulations... Type 92) § 29.1028 Leaf. Whole, unstemmed leaf. Leaf, when applied to tobacco in strip form, shall describe the divided unit of a whole leaf. [49 FR 16755, Apr. 20, 1984. Redesignated at 51 FR 25027, July...

  1. 7 CFR 29.2528 - Leaf.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 2 2014-01-01 2014-01-01 false Leaf. 29.2528 Section 29.2528 Agriculture Regulations...-Cured Tobacco (u.s. Types 22, 23, and Foreign Type 96) § 29.2528 Leaf. Whole, unstemmed leaf. Leaf, when applied to tobacco in strip form, shall describe the divided unit of a whole leaf. ...

  2. Relationships of leaf dark respiration to leaf nitrogen, specific leaf area and leaf life-span: a test across biomes and functional groups

    Treesearch

    Peter B. Reich; Michael B. Walters; David S. Ellsworth; [and others; [Editor’s note: James M.. Vose is the SRS co-author for this publication.

    1998-01-01

    Based on prior evidence of coordinated multiple leaf trait scaling, the authors hypothesized that variation among species in leaf dark respiration rate (Rd) should scale with variation in traits such as leaf nitrogen (N), leaf life-span, specific leaf area (SLA), and net photosynthetic capacity (Amax). However, it is not known whether such scaling, if it exists, is...

  3. Translation elongation-3-like factors: are they rational antifungal targets?

    PubMed

    Sturtevant, Joy

    2002-10-01

    The occurrence of fungal infection has escalated significantly in recent years and is expected to continue to increase for the foreseeable future. Unfortunately, only a limited number of antifungal drugs are currently available partially due to a lack of suitable targets. The most commonly used antifungals target the same molecule in the cell membrane and, while efficacious, are either extremely toxic or susceptible to resistance. This article examines elongation factor-3, which is unique to fungi and essential for fungal cell survival and, thus, an attractive antifungal target. A search for inhibitors of this 'perfect target' led to identification of compounds (sordarins) which inhibited elongation factor-2, a protein with a mammalian homologue. Molecular analysis demonstrated why sordarins can specifically act against fungal elongation factor-2. This data questions the validity of pursuing genes as targets only if they are unique to fungi. Proteins that are homologous to elongation factor-3 are also discussed. The advances in molecular techniques and bioinformatics will allow the re-evaluation of targets previously thought to be unattractive. In addition, molecular genetics provides new and novel information on cellular processes that can potentially introduce new targets.

  4. Collisional diffusion in toroidal plasmas with elongation and triangularity

    SciTech Connect

    Martin, P.; Castro, E.; Haines, M. G.

    2007-05-15

    Collisional diffusion is analyzed for plasma tokamaks with different ellipticities and triangularities. Improved nonlinear equations for the families of magnetic surfaces are used here. Dimensionless average velocities are calculated as a function of the inductive electric field, elongation, triangularity, and Shafranov shift. Confinement has been found to depend significantly on triangularity.

  5. Molecular landscape of cotton fiber in early elongation

    USDA-ARS?s Scientific Manuscript database

    Cotton fibers are the dominant source of natural fibers used in the textile industry and contribute significantly to the world economy. Adverse environmental conditions negatively affect fiber characteristics, especially when the fibers are in the elongation phase of development. Improvement in the...

  6. FtsZ-Dependent Elongation of a Coccoid Bacterium

    PubMed Central

    Pereira, Ana R.; Hsin, Jen; Król, Ewa; Tavares, Andreia C.; Flores, Pierre; Hoiczyk, Egbert; Ng, Natalie; Dajkovic, Alex; Brun, Yves V.; VanNieuwenhze, Michael S.; Roemer, Terry; Carballido-Lopez, Rut; Huang, Kerwyn Casey

    2016-01-01

    ABSTRACT A mechanistic understanding of the determination and maintenance of the simplest bacterial cell shape, a sphere, remains elusive compared with that of more complex shapes. Cocci seem to lack a dedicated elongation machinery, and a spherical shape has been considered an evolutionary dead-end morphology, as a transition from a spherical to a rod-like shape has never been observed in bacteria. Here we show that a Staphylococcus aureus mutant (M5) expressing the ftsZG193D allele exhibits elongated cells. Molecular dynamics simulations and in vitro studies indicate that FtsZG193D filaments are more twisted and shorter than wild-type filaments. In vivo, M5 cell wall deposition is initiated asymmetrically, only on one side of the cell, and progresses into a helical pattern rather than into a constricting ring as in wild-type cells. This helical pattern of wall insertion leads to elongation, as in rod-shaped cells. Thus, structural flexibility of FtsZ filaments can result in an FtsZ-dependent mechanism for generating elongated cells from cocci. PMID:27601570

  7. Structural insights into NusG regulating transcription elongation

    PubMed Central

    Liu, Bin; Steitz, Thomas A.

    2017-01-01

    NusG is an essential transcription factor that plays multiple key regulatory roles in transcription elongation, termination and coupling translation and transcription. The core role of NusG is to enhance transcription elongation and RNA polymerase processivity. Here, we present the structure of Escherichia coli RNA polymerase complexed with NusG. The structure shows that the NusG N-terminal domain (NGN) binds at the central cleft of RNA polymerase surrounded by the β' clamp helices, the β protrusion, and the β lobe domains to close the promoter DNA binding channel and constrain the β' clamp domain, but with an orientation that is different from the one observed in the archaeal β' clamp–Spt4/5 complex. The structure also allows us to construct a reliable model of the complete NusG-associated transcription elongation complex, suggesting that the NGN domain binds at the upstream fork junction of the transcription elongation complex, similar to σ2 in the transcription initiation complex, to stabilize the junction, and therefore enhances transcription processivity. PMID:27899640

  8. Evidence for parallel elongated structures in the mesosphere

    NASA Technical Reports Server (NTRS)

    Adams, G. W.; Brosnahan, J. W.; Walden, D. C.

    1983-01-01

    The physical cause of partial reflection from the mesosphere is of interest. Data are presented from an image-forming radar at Brighton, Colorado, that suggest that some of the radar scattering is caused by parallel elongated structures lying almost directly overhead. Possible physical sources for such structures include gravity waves and roll vortices.

  9. Key patterning genes contribute to leg elongation in water striders.

    PubMed

    Refki, Peter Nagui; Khila, Abderrahman

    2015-01-01

    How adaptive phenotypes are shaped by the action of key developmental genes during ontogeny remains poorly understood. Water striders, a group of hemipteran insects, present a unique example of adaptation to life on the fluid water surface substrate. The group has undergone a set of leg modifications allowing them to efficiently move on the water surface and hence invade a variety of niches from ponds to open oceans. The elongated legs of water striders play a key role in generating efficient movement on the fluid by acting as propelling oars. To determine the developmental mechanisms underlying leg elongation, we examined the function of the key developmental genes decapentaplegic (dpp), wingless (wg), epidermal growth factor receptor (egfr), and hedgehog (hh) during embryonic development in the water strider Limnoporus dissortis. By analyzing expression patterns and RNAi knockdown phenotypes, we uncover the role of these genes in leg growth and patterning during embryogenesis. Our results indicate that wg and egfr contribute to the elongation of all the three segments of all thoracic legs, whereas hh specifies distal leg segments. Together, our results suggest that key patterning genes contribute to the dramatic elongation of thoracic appendages in water striders.

  10. A SnapShot of Ubiquitin Chain Elongation

    PubMed Central

    Kovacev, Jordan; Wu, Kenneth; Spratt, Donald E.; Chong, Robert A.; Lee, Chan; Nayak, Jaladhi; Shaw, Gary S.; Pan, Zhen-Qiang

    2014-01-01

    We have explored the mechanisms of polyubiquitin chain assembly with reconstituted ubiquitination of IκBα and β-catenin by the Skp1-cullin 1-βTrCP F-box protein (SCFβTrCP) E3 ubiquitin (Ub) ligase complex. Competition experiments revealed that SCFβTrCP formed a complex with IκBα and that the Nedd8 modified E3-substrate platform engaged in dynamic interactions with the Cdc34 E2 Ub conjugating enzyme for chain elongation. Using “elongation intermediates” containing β-catenin linked with Ub chains of defined length, it was observed that a Lys-48-Ub chain of a length greater than four, but not its Lys-63 linkage counterparts, slowed the rate of additional Ub conjugation. Thus, the Ub chain length and linkage impact kinetic rates of chain elongation. Given that Lys-48-tetra-Ub is packed into compact conformations due to extensive intrachain interactions between Ub subunits, this topology may limit the accessibility of SCFβTrCP/Cdc34 to the distal Ub Lys-48 and result in slowed elongation. PMID:24464578

  11. Proliferation of elongate fishes in the deep sea.

    PubMed

    Neat, F C; Campbell, N

    2013-12-01

    It was hypothesized that energetically efficient anguilliform swimming and axial elongation in fishes is favoured in the deep sea and predicted that the degree of elongation of the body form of fishes would increase with depth. An index of fish shape was derived from the relationship between length and mass. This was combined with data on abundance of c. 266 fish species from 389 research trawl tows made at depths of between 300 and 2030 m in the north-east Atlantic Ocean. The degree of elongation of the fish increased with depth to c. 1250 m before levelling off. The strength of this phenomenon varied between higher level taxa, being most apparent in the Gadiformes and Osmeriformes, and weak or absent in the Perciformes and Selachimorpha. The advantage of efficient elongate body forms may explain why certain taxa such as the grenadiers (Macrouridae) have dominated the deep sea, some have restricted depth ranges, e.g. the sharks, skates and rays, and others are almost entirely absent, e.g. the flatfishes (Pleuronectiformes). © 2013 The Fisheries Society of the British Isles.

  12. Quantitative regulation of FLC via coordinated transcriptional initiation and elongation

    PubMed Central

    Wu, Zhe; Ietswaart, Robert; Liu, Fuquan; Yang, Hongchun; Howard, Martin; Dean, Caroline

    2016-01-01

    The basis of quantitative regulation of gene expression is still poorly understood. In Arabidopsis thaliana, quantitative variation in expression of FLOWERING LOCUS C (FLC) influences the timing of flowering. In ambient temperatures, FLC expression is quantitatively modulated by a chromatin silencing mechanism involving alternative polyadenylation of antisense transcripts. Investigation of this mechanism unexpectedly showed that RNA polymerase II (Pol II) occupancy changes at FLC did not reflect RNA fold changes. Mathematical modeling of these transcriptional dynamics predicted a tight coordination of transcriptional initiation and elongation. This prediction was validated by detailed measurements of total and chromatin-bound FLC intronic RNA, a methodology appropriate for analyzing elongation rate changes in a range of organisms. Transcription initiation was found to vary ∼25-fold with elongation rate varying ∼8- to 12-fold. Premature sense transcript termination contributed very little to expression differences. This quantitative variation in transcription was coincident with variation in H3K36me3 and H3K4me2 over the FLC gene body. We propose different chromatin states coordinately influence transcriptional initiation and elongation rates and that this coordination is likely to be a general feature of quantitative gene regulation in a chromatin context. PMID:26699513

  13. Molecular development of the mid-stage elongating cotton fiber

    USDA-ARS?s Scientific Manuscript database

    Cotton fiber is one of the leading natural textile fibers and is the leading value added crop in the USA. The annual business revenue from the cotton industry exceeds $120 billion. The growth of the cotton fiber is divided into four unique, yet overlapping stages; initiation, elongation, secondary w...

  14. Widespread regulation of translation by elongation pausing in heat shock.

    PubMed

    Shalgi, Reut; Hurt, Jessica A; Krykbaeva, Irina; Taipale, Mikko; Lindquist, Susan; Burge, Christopher B

    2013-02-07

    Global repression of protein synthesis is a hallmark of the cellular stress response and has been attributed primarily to inhibition of translation initiation, although this mechanism may not always explain the full extent of repression. Here, using ribosome footprinting, we show that 2 hr of severe heat stress triggers global pausing of translation elongation at around codon 65 on most mRNAs in both mouse and human cells. The genome-wide nature of the phenomenon, its location, and features of protein N termini suggested the involvement of ribosome-associated chaperones. After severe heat shock, Hsp70's interactions with the translational machinery were markedly altered and its association with ribosomes was reduced. Pretreatment with mild heat stress or overexpression of Hsp70 protected cells from heat shock-induced elongation pausing, while inhibition of Hsp70 activity triggered elongation pausing without heat stress. Our findings suggest that regulation of translation elongation in general, and by chaperones in particular, represents a major component of cellular stress responses.

  15. Transcriptome Sequencing and Analysis for Culm Elongation of the World’s Largest Bamboo (Dendrocalamus sinicus)

    PubMed Central

    Cui, Kai; Wang, Haiying; Liao, Shengxi; Tang, Qi; Li, Li; Cui, Yongzhong; He, Yuan

    2016-01-01

    proteins that regarded as the main tool for capturing light of plants, implying stem photosynthesis plays a key role during culm elongation due to the unavailability of its leaf. By real-time quantitative PCR, the expression level of 6 unigenes was detected. The results showed the expression level of all genes accorded with the transcriptome data, which confirm the reliability of the transcriptome data. As we know, this is the first study underline the D. sinicus transcriptome, which will deepen the understanding of the molecular mechanisms of culm development. The results may help variety improvement and resource utilization of bamboos. PMID:27304219

  16. Transcriptome Sequencing and Analysis for Culm Elongation of the World's Largest Bamboo (Dendrocalamus sinicus).

    PubMed

    Cui, Kai; Wang, Haiying; Liao, Shengxi; Tang, Qi; Li, Li; Cui, Yongzhong; He, Yuan

    2016-01-01

    proteins that regarded as the main tool for capturing light of plants, implying stem photosynthesis plays a key role during culm elongation due to the unavailability of its leaf. By real-time quantitative PCR, the expression level of 6 unigenes was detected. The results showed the expression level of all genes accorded with the transcriptome data, which confirm the reliability of the transcriptome data. As we know, this is the first study underline the D. sinicus transcriptome, which will deepen the understanding of the molecular mechanisms of culm development. The results may help variety improvement and resource utilization of bamboos.

  17. Binary asteroid population. 3. Secondary rotations and elongations

    NASA Astrophysics Data System (ADS)

    Pravec, P.; Scheirich, P.; Kušnirák, P.; Hornoch, K.; Galád, A.; Naidu, S. P.; Pray, D. P.; Világi, J.; Gajdoš, Š.; Kornoš, L.; Krugly, Yu. N.; Cooney, W. R.; Gross, J.; Terrell, D.; Gaftonyuk, N.; Pollock, J.; Husárik, M.; Chiorny, V.; Stephens, R. D.; Durkee, R.; Reddy, V.; Dyvig, R.; Vraštil, J.; Žižka, J.; Mottola, S.; Hellmich, S.; Oey, J.; Benishek, V.; Kryszczyńska, A.; Higgins, D.; Ries, J.; Marchis, F.; Baek, M.; Macomber, B.; Inasaridze, R.; Kvaratskhelia, O.; Ayvazian, V.; Rumyantsev, V.; Masi, G.; Colas, F.; Lecacheux, J.; Montaigut, R.; Leroy, A.; Brown, P.; Krzeminski, Z.; Molotov, I.; Reichart, D.; Haislip, J.; LaCluyze, A.

    2016-03-01

    We collected data on rotations and elongations of 46 secondaries of binary and triple systems among near-Earth, Mars-crossing and small main belt asteroids. 24 were found or are strongly suspected to be synchronous (in 1:1 spin-orbit resonance), and the other 22, generally on more distant and/or eccentric orbits, were found or are suggested to have asynchronous rotations. For 18 of the synchronous secondaries, we constrained their librational angles, finding that their long axes pointed to within 20° of the primary on most epochs. The observed anti-correlation of secondary synchroneity with orbital eccentricity and the limited librational angles agree with the theories by Ćuk and Nesvorný (Ćuk, M., Nesvorný, D. [2010]. Icarus 207, 732-743) and Naidu and Margot (Naidu, S.P., Margot, J.-L. [2015]. Astron. J. 149, 80). A reason for the asynchronous secondaries being on wider orbits than synchronous ones may be longer tidal circularization time scales at larger semi-major axes. The asynchronous secondaries show relatively fast spins; their rotation periods are typically < 10 h. An intriguing observation is a paucity of chaotic secondary rotations; with an exception of (35107) 1991 VH, the secondary rotations are single-periodic with no signs of chaotic rotation and their periods are constant on timescales from weeks to years. The secondary equatorial elongations show an upper limit of a2 /b2 ∼ 1.5 . The lack of synchronous secondaries with greater elongations appears consistent, considering uncertainties of the axis ratio estimates, with the theory by Ćuk and Nesvorný that predicts large regions of chaotic rotation in the phase space for a2 /b2 ≳√{ 2 } . Alternatively, secondaries may not form or stay very elongated in gravitational (tidal) field of the primary. It could be due to the secondary fission mechanism suggested by Jacobson and Scheeres (Jacobson, S.A., Scheeres, D.J. [2011]. Icarus 214, 161-178), as its efficiency is correlated with the

  18. Adenylate cyclase regulates elongation of mammalian primary cilia

    SciTech Connect

    Ou, Young; Ruan, Yibing; Cheng, Min; Moser, Joanna J.; Rattner, Jerome B.; Hoorn, Frans A. van der

    2009-10-01

    The primary cilium is a non-motile microtubule-based structure that shares many similarities with the structures of flagella and motile cilia. It is well known that the length of flagella is under stringent control, but it is not known whether this is true for primary cilia. In this study, we found that the length of primary cilia in fibroblast-like synoviocytes, either in log phase culture or in quiescent state, was confined within a range. However, when lithium was added to the culture to a final concentration of 100 mM, primary cilia of synoviocytes grew beyond this range, elongating to a length that was on average approximately 3 times the length of untreated cilia. Lithium is a drug approved for treating bipolar disorder. We dissected the molecular targets of this drug, and observed that inhibition of adenylate cyclase III (ACIII) by specific inhibitors mimicked the effects of lithium on primary cilium elongation. Inhibition of GSK-3{beta} by four different inhibitors did not induce primary cilia elongation. ACIII was found in primary cilia of a variety of cell types, and lithium treatment of these cell types led to their cilium elongation. Further, we demonstrate that different cell types displayed distinct sensitivities to the lithium treatment. However, in all cases examined primary cilia elongated as a result of lithium treatment. In particular, two neuronal cell types, rat PC-12 adrenal medulla cells and human astrocytes, developed long primary cilia when lithium was used at or close to the therapeutic relevant concentration (1-2 mM). These results suggest that the length of primary cilia is controlled, at least in part, by the ACIII-cAMP signaling pathway.

  19. The artificial leaf.

    PubMed

    Nocera, Daniel G

    2012-05-15

    To convert the energy of sunlight into chemical energy, the leaf splits water via the photosynthetic process to produce molecular oxygen and hydrogen, which is in a form of separated protons and electrons. The primary steps of natural photosynthesis involve the absorption of sunlight and its conversion into spatially separated electron-hole pairs. The holes of this wireless current are captured by the oxygen evolving complex (OEC) of photosystem II (PSII) to oxidize water to oxygen. The electrons and protons produced as a byproduct of the OEC reaction are captured by ferrodoxin of photosystem I. With the aid of ferrodoxin-NADP(+) reductase, they are used to produce hydrogen in the form of NADPH. For a synthetic material to realize the solar energy conversion function of the leaf, the light-absorbing material must capture a solar photon to generate a wireless current that is harnessed by catalysts, which drive the four electron/hole fuel-forming water-splitting reaction under benign conditions and under 1 sun (100 mW/cm(2)) illumination. This Account describes the construction of an artificial leaf comprising earth-abundant elements by interfacing a triple junction, amorphous silicon photovoltaic with hydrogen- and oxygen-evolving catalysts made from a ternary alloy (NiMoZn) and a cobalt-phosphate cluster (Co-OEC), respectively. The latter captures the structural and functional attributes of the PSII-OEC. Similar to the PSII-OEC, the Co-OEC self-assembles upon oxidation of an earth-abundant metal ion from 2+ to 3+, may operate in natural water at room temperature, and is self-healing. The Co-OEC also activates H(2)O by a proton-coupled electron transfer mechanism in which the Co-OEC is increased by four hole equivalents akin to the S-state pumping of the Kok cycle of PSII. X-ray absorption spectroscopy studies have established that the Co-OEC is a structural relative of Mn(3)CaO(4)-Mn cubane of the PSII-OEC, where Co replaces Mn and the cubane is extended in a

  20. The control of tomato fruit elongation orchestrated by sun, ovate and fs8.1 in a wild relative of tomato.

    PubMed

    Wu, Shan; Clevenger, Josh P; Sun, Liang; Visa, Sofia; Kamiya, Yuji; Jikumaru, Yusuke; Blakeslee, Joshua; van der Knaap, Esther

    2015-09-01

    Within the cultivated tomato germplasm, sun, ovate and fs8.1 are the three predominant QTLs controlling fruit elongation. Although SUN and OVATE have been cloned, their role in plant growth and development are not well understood. To compare and contrast the effects of the three QTLs in a homogeneous background, we developed near isogenic lines (NILs) in the wild species Solanum pimpinellifolium LA1589 background. We carried out detailed morphological characterization of reproductive and vegetative organs in the single, double and triple NILs and determined the epistatic interactions of the three loci affecting fruit shape. The phenotypic evaluations demonstrated that the three loci regulate unique aspects of ovary and fruit elongation and in different temporal manners. The strongest effect on organ shape was caused by sun. In addition to fruit shape, sun also affected leaf and sepal elongation and stem thickness. The synergistic interaction between sun and ovate or fs8.1 suggested that the pathways involving SUN, OVATE and the gene(s) underlying fs8.1 may converge at a common node. The results of an extensive profiling analysis suggested that the degree of fruit elongation was not related to the accumulation of any of the classical hormones.

  1. How to pattern a leaf

    USDA-ARS?s Scientific Manuscript database

    Leaf development presents a tremendous resource for tackling the question of patterning in biology. Leaves can be simple or highly dissected. They may have elaborated parts such as the tendrils of a pea leaf or the rolled blade of a carnivorous pitcher plant. Despite the variation in size, shape, an...

  2. Exserohilum Leaf Spot on Tigergrass

    USDA-ARS?s Scientific Manuscript database

    Tigergrass (Thysanolaena maxima (Roxb.) Kuntze ) is a popular ornamental grass grown throughout landscapes in South Florida. In the summer of 2006, a leaf spot was observed on tigergrass in the landscape and a commercial nursery in Homestead, FL. The causal agent of the leaf spot was isolated, cha...

  3. Modelling changes in leaf shape prior to phyllode acquisition in Acacia mangium Willd. seedlings.

    PubMed

    Leroy, Céline; Heuret, Patrick

    2008-02-01

    The aim of this study was to characterise changes in leaf shape prior to phyllode acquisition along the axes of Acacia mangium seedlings. The study area was located in North Lampung (South Sumatra, Indonesia), where these trees belong to a naturally regenerated stand. A total of 173 seedlings, less than three months old, were described node by node. Leaf shape and leaf length were recorded and the way in which one leaf type succeeded another was modelled using a hidden semi-Markov chain composed of seven states. The phyllotactical pattern was studied using another sample of forty 6-month-old seedlings. The results indicate (i) the existence of successive zones characterised by one or a combination of leaf types, and (ii) that phyllode acquisition seems to be accompanied by a change in the phyllotactical pattern. The concepts of juvenility and heteroblasty, as well as potential applications for taxonomy are discussed.

  4. Genetic Architecture and Molecular Networks Underlying Leaf Thickness in Desert-Adapted Tomato Solanum pennellii.

    PubMed

    Coneva, Viktoriya; Frank, Margaret H; Balaguer, Maria A de Luis; Li, Mao; Sozzani, Rosangela; Chitwood, Daniel H

    2017-09-01

    Thicker leaves allow plants to grow in water-limited conditions. However, our understanding of the genetic underpinnings of this highly functional leaf shape trait is poor. We used a custom-built confocal profilometer to directly measure leaf thickness in a set of introgression lines (ILs) derived from the desert tomato Solanum pennellii and identified quantitative trait loci. We report evidence of a complex genetic architecture of this trait and roles for both genetic and environmental factors. Several ILs with thick leaves have dramatically elongated palisade mesophyll cells and, in some cases, increased leaf ploidy. We characterized the thick IL2-5 and IL4-3 in detail and found increased mesophyll cell size and leaf ploidy levels, suggesting that endoreduplication underpins leaf thickness in tomato. Next, we queried the transcriptomes and inferred dynamic Bayesian networks of gene expression across early leaf ontogeny in these lines to compare the molecular networks that pattern leaf thickness. We show that thick ILs share S. pennellii-like expression profiles for putative regulators of cell shape and meristem determinacy as well as a general signature of cell cycle-related gene expression. However, our network data suggest that leaf thickness in these two lines is patterned at least partially by distinct mechanisms. Consistent with this hypothesis, double homozygote lines combining introgression segments from these two ILs show additive phenotypes, including thick leaves, higher ploidy levels, and larger palisade mesophyll cells. Collectively, these data establish a framework of genetic, anatomical, and molecular mechanisms that pattern leaf thickness in desert-adapted tomato. © 2017 American Society of Plant Biologists. All Rights Reserved.

  5. Leaf-inhabiting genera of the Gnomoniaceae, Diaporthales

    PubMed Central

    Sogonov, M.V.; Castlebury, L.A.; Rossman, A.Y.; Mejía, L.C.; White, J.F.

    2008-01-01

    The Gnomoniaceae are characterised by ascomata that are generally immersed, solitary, without a stroma, or aggregated with a rudimentary stroma, in herbaceous plant material especially in leaves, twigs or stems, but also in bark or wood. The ascomata are black, soft-textured, thin-walled, and pseudoparenchymatous with one or more central or eccentric necks. The asci usually have a distinct apical ring. The Gnomoniaceae includes species having ascospores that are small, mostly less than 25 μm long, although some are longer, and range in septation from non-septate to one-septate, rarely multi-septate. Molecular studies of the Gnomoniaceae suggest that the traditional classification of genera based on characteristics of the ascomata such as position of the neck and ascospores such as septation have resulted in genera that are not monophyletic. In this paper the concepts of the leaf-inhabiting genera in the Gnomoniaceae are reevaluated using multiple genes, specifically nrLSU, translation elongation factor 1-alpha (tef1-α), and RNA polymerase II second largest subunit (rpb2) for 64 isolates. ITS sequences were generated for 322 isolates. Six genera of leaf-inhabiting Gnomoniaceae are defined based on placement of their type species within the multigene phylogeny. The new monotypic genus Ambarignomonia is established for an unusual species, A. petiolorum. A key to 59 species of leaf-inhabiting Gnomoniaceae is presented and 22 species of Gnomoniaceae are described and illustrated. PMID:19287541

  6. Diel time-courses of leaf growth in monocot and dicot species: endogenous rhythms and temperature effects

    PubMed Central

    Poiré, Richard; Wiese-Klinkenberg, Anika; Parent, Boris; Mielewczik, Michael; Schurr, Ulrich; Tardieu, François; Walter, Achim

    2010-01-01

    Diel (24 h) leaf growth patterns were differently affected by temperature variations and the circadian clock in several plant species. In the monocotyledon Zea mays, leaf elongation rate closely followed changes in temperature. In the dicotyledons Nicotiana tabacum, Ricinus communis, and Flaveria bidentis, the effect of temperature regimes was less obvious and leaf growth exhibited a clear circadian oscillation.These differences were related neither to primary metabolism nor to altered carbohydrate availability for growth. The effect of endogenous rhythms on leaf growth was analysed under continuous light in Arabidopsis thaliana, Ricinus communis, Zea mays, and Oryza sativa. No rythmic growth was observed under continuous light in the two monocotyledons, while growth rhythmicity persisted in the two dicotyledons. Based on model simulations it is concluded that diel leaf growth patterns in mono- and dicotyledons result from the additive effects of both circadian-clock-controlled processes and responses to environmental changes such as temperature and evaporative demand. Apparently very distinct diel leaf growth behaviour of monocotyledons and dicotyledons can thus be explained by the different degrees to which diel temperature variations affect leaf growth in the two groups of species which, in turn, depends on the extent of the leaf growth control by internal clocks. PMID:20299442

  7. Light-induced transient ion flux responses from maize leaves and their association with leaf growth and photosynthesis.

    PubMed

    Zivanović, B D; Pang, J; Shabala, S

    2005-03-01

    Net fluxes of H+, K+ and Ca2+ ions from maize (Zea mays L.) isolated leaf segments were measured non-invasively using ion-selective vibrating microelectrodes (the MIFE technique). Leaf segments were isolated from the blade base, containing actively elongating cells (basal segments), and from non-growing tip regions (tip segments). Ion fluxes were measured in response to bright white light (2600 micromoles m-2 s-1) from either the leaf segments or the underlying mesophyll (after stripping the epidermis). Fluxes measured from the mesophyll showed no significant difference between basal and tip regions. In leaf segments (epidermis attached), light-induced flux kinetics of all ions measured (H+, Ca2+ and K+) were strikingly different between the two regions. It appears that epidermal K+ fluxes are required to drive leaf expansion growth, whereas in the mesophyll light-induced K+ flux changes are likely to play a charge balancing role. Light-stimulated Ca2+ influx was not directly attributable either to leaf photosynthetic performance or to leaf expansion growth. It is concluded that light-induced ion flux changes are associated with both leaf growth and photosynthesis.

  8. Transcription impairment and cell migration defects in elongator-depleted cells: implication for familial dysautonomia.

    PubMed

    Close, Pierre; Hawkes, Nicola; Cornez, Isabelle; Creppe, Catherine; Lambert, Charles A; Rogister, Bernard; Siebenlist, Ulrich; Merville, Marie-Paule; Slaugenhaupt, Susan A; Bours, Vincent; Svejstrup, Jesper Q; Chariot, Alain

    2006-05-19

    Mutations in IKBKAP, encoding a subunit of Elongator, cause familial dysautonomia (FD), a severe neurodevelopmental disease with complex clinical characteristics. Elongator was previously linked not only with transcriptional elongation and histone acetylation but also with other cellular processes. Here, we used RNA interference (RNAi) and fibroblasts from FD patients to identify Elongator target genes and study the role of Elongator in transcription. Strikingly, whereas Elongator is recruited to both target and nontarget genes, only target genes display histone H3 hypoacetylation and progressively lower RNAPII density through the coding region in FD cells. Interestingly, several target genes encode proteins implicated in cell motility. Indeed, characterization of IKAP/hELP1 RNAi cells, FD fibroblasts, and neuronal cell-derived cells uncovered defects in this cellular function upon Elongator depletion. These results indicate that defects in Elongator function affect transcriptional elongation of several genes and that the ensuing cell motility deficiencies may underlie the neuropathology of FD patients.

  9. Regulation of Stalk Elongation by Phosphate in Caulobacter crescentus

    PubMed Central

    Gonin, Madeleine; Quardokus, Ellen M.; O'Donnol, Danielle; Maddock, Janine; Brun, Yves V.

    2000-01-01

    In Caulobacter crescentus, stalk biosynthesis is regulated by cell cycle cues and by extracellular phosphate concentration. Phosphate-starved cells undergo dramatic stalk elongation to produce stalks as much as 30 times as long as those of cells growing in phosphate-rich medium. To identify genes involved in the control of stalk elongation, transposon mutants were isolated that exhibited a long-stalk phenotype irrespective of extracellular phosphate concentration. The disrupted genes were identified as homologues of the high-affinity phosphate transport genes pstSCAB of Escherichia coli. In E. coli, pst mutants have a constitutively expressed phosphate (Pho) regulon. To determine if stalk elongation is regulated by the Pho regulon, the Caulobacter phoB gene that encodes the transcriptional activator of the Pho regulon was cloned and mutated. While phoB was not required for stalk synthesis or for the cell cycle timing of stalk synthesis initiation, it was required for stalk elongation in response to phosphate starvation. Both pstS and phoB mutants were deficient in phosphate transport. When a phoB mutant was grown with limiting phosphate concentrations, stalks only increased in length by an average of 1.4-fold compared to the average 9-fold increase in stalk length of wild-type cells grown in the same medium. Thus, the phenotypes of phoB and pst mutants were opposite. phoB mutants were unable to elongate stalks during phosphate starvation, whereas pst mutants made long stalks in both high- and low-phosphate media. Analysis of double pst phoB mutants indicated that the long-stalk phenotype of pst mutants was dependent on phoB. In addition, analysis of a pstS-lacZ transcriptional fusion showed that pstS transcription is dependent on phoB. These results suggest that the signal transduction pathway that stimulates stalk elongation in response to phosphate starvation is mediated by the Pst proteins and the response regulator PhoB. PMID:10629178

  10. Proteomic Analysis Reveals the Leaf Color Regulation Mechanism in Chimera Hosta “Gold Standard” Leaves

    PubMed Central

    Yu, Juanjuan; Zhang, Jinzheng; Zhao, Qi; Liu, Yuelu; Chen, Sixue; Guo, Hongliang; Shi, Lei; Dai, Shaojun

    2016-01-01

    Leaf color change of variegated leaves from chimera species is regulated by fine-tuned molecular mechanisms. Hosta “Gold Standard” is a typical chimera Hosta species with golden-green variegated leaves, which is an ideal material to investigate the molecular mechanisms of leaf variegation. In this study, the margin and center regions of young and mature leaves from Hosta “Gold Standard”, as well as the leaves from plants after excess nitrogen fertilization were studied using physiological and comparative proteomic approaches. We identified 31 differentially expressed proteins in various regions and development stages of variegated leaves. Some of them may be related to the leaf color regulation in Hosta “Gold Standard”. For example, cytosolic glutamine synthetase (GS1), heat shock protein 70 (Hsp70), and chloroplastic elongation factor G (cpEF-G) were involved in pigment-related nitrogen synthesis as well as protein synthesis and processing. By integrating the proteomics data with physiological results, we revealed the metabolic patterns of nitrogen metabolism, photosynthesis, energy supply, as well as chloroplast protein synthesis, import and processing in various leaf regions at different development stages. Additionally, chloroplast-localized proteoforms involved in nitrogen metabolism, photosynthesis and protein processing implied that post-translational modifications were crucial for leaf color regulation. These results provide new clues toward understanding the mechanisms of leaf color regulation in variegated leaves. PMID:27005614

  11. Proteomic Analysis Reveals the Leaf Color Regulation Mechanism in Chimera Hosta "Gold Standard" Leaves.

    PubMed

    Yu, Juanjuan; Zhang, Jinzheng; Zhao, Qi; Liu, Yuelu; Chen, Sixue; Guo, Hongliang; Shi, Lei; Dai, Shaojun

    2016-03-08

    Leaf color change of variegated leaves from chimera species is regulated by fine-tuned molecular mechanisms. Hosta "Gold Standard" is a typical chimera Hosta species with golden-green variegated leaves, which is an ideal material to investigate the molecular mechanisms of leaf variegation. In this study, the margin and center regions of young and mature leaves from Hosta "Gold Standard", as well as the leaves from plants after excess nitrogen fertilization were studied using physiological and comparative proteomic approaches. We identified 31 differentially expressed proteins in various regions and development stages of variegated leaves. Some of them may be related to the leaf color regulation in Hosta "Gold Standard". For example, cytosolic glutamine synthetase (GS1), heat shock protein 70 (Hsp70), and chloroplastic elongation factor G (cpEF-G) were involved in pigment-related nitrogen synthesis as well as protein synthesis and processing. By integrating the proteomics data with physiological results, we revealed the metabolic patterns of nitrogen metabolism, photosynthesis, energy supply, as well as chloroplast protein synthesis, import and processing in various leaf regions at different development stages. Additionally, chloroplast-localized proteoforms involved in nitrogen metabolism, photosynthesis and protein processing implied that post-translational modifications were crucial for leaf color regulation. These results provide new clues toward understanding the mechanisms of leaf color regulation in variegated leaves.

  12. Elongated solid electrolyte cell configurations and flexible connections therefor

    DOEpatents

    Reichner, Philip

    1989-01-01

    A flexible, high temperature, solid oxide electrolyte electrochemical cell stack configuration is made, comprising a plurality of flattened, elongated, connected cell combinations 1, each cell combination containing an interior electrode 2 having a top surface and a plurality of interior gas feed conduits 3, through its axial length, electrolyte 5 contacting the interior electrode and exterior electrode 8 contacting electrolyte, where a major portion of the air electrode top surface 7 is covered by interconnection material 6, and where each cell has at least one axially elongated, electronically conductive, flexible, porous, metal fiber felt material 9 in electronic connection with the air electrode 2 through contact with a major portion of the interconnection material 6, the metal fiber felt being effective as a shock absorbent body between the cells.

  13. TERRA promotes telomerase-mediated telomere elongation in Schizosaccharomyces pombe.

    PubMed

    Moravec, Martin; Wischnewski, Harry; Bah, Amadou; Hu, Yan; Liu, Na; Lafranchi, Lorenzo; King, Megan C; Azzalin, Claus M

    2016-07-01

    Telomerase-mediated telomere elongation provides cell populations with the ability to proliferate indefinitely. Telomerase is capable of recognizing and extending the shortest telomeres in cells; nevertheless, how this mechanism is executed remains unclear. Here, we show that, in the fission yeast Schizosaccharomyces pombe, shortened telomeres are highly transcribed into the evolutionarily conserved long noncoding RNA TERRA A fraction of TERRA produced upon telomere shortening is polyadenylated and largely devoid of telomeric repeats, and furthermore, telomerase physically interacts with this polyadenylated TERRA in vivo We also show that experimentally enhanced transcription of a manipulated telomere promotes its association with telomerase and concomitant elongation. Our data represent the first direct evidence that TERRA stimulates telomerase recruitment and activity at chromosome ends in an organism with human-like telomeres. © 2016 The Authors.

  14. Critical dynamics of vesicle stretching transition in elongational flow.

    PubMed

    Kantsler, Vasiliy; Segre, Enrico; Steinberg, Victor

    2008-07-25

    We present results on the stretching of single tubular vesicles in an elongation flow toward dumbbell shapes, and on their relaxation. A critical strain rate epsilonc exists; for strain rates epsilonelongation flow.

  15. DNA sequencing by synthesis based on elongation delay detection

    NASA Astrophysics Data System (ADS)

    Manturov, Alexey O.; Grigoryev, Anton V.

    2015-03-01

    The one of most important problem in modern genetics, biology and medicine is determination of the primary nucleotide sequence of the DNA of living organisms (DNA sequencing). This paper describes the label-free DNA sequencing approach, based on the observation of a discrete dynamics of DNA sequence elongation phase. The proposed DNA sequencing principle are studied by numerical simulation. The numerical model for proposed label-free DNA sequencing approach is based on a cellular automaton, which can simulate the elongation stage (growth of DNA strands) and dynamics of nucleotides incorporation to rising DNA strand. The estimates for number of copied DNA sequences for required probability of nucleotide incorporation event detection and correct DNA sequence determination was obtained. The proposed approach can be applied at all known DNA sequencing devices with "sequencing by synthesis" principle of operation.

  16. Elongated solid electrolyte cell configurations and flexible connections therefor

    DOEpatents

    Reichner, P.

    1989-10-17

    A flexible, high temperature, solid oxide electrolyte electrochemical cell stack configuration is made, comprising a plurality of flattened, elongated, connected cell combinations, each cell combination containing an interior electrode having a top surface and a plurality of interior gas feed conduits, through its axial length, electrolyte contacting the interior electrode and exterior electrode contacting electrolyte, where a major portion of the air electrode top surface is covered by interconnection material, and where each cell has at least one axially elongated, electronically conductive, flexible, porous, metal fiber felt material in electronic connection with the air electrode through contact with a major portion of the interconnection material, the metal fiber felt being effective as a shock absorbent body between the cells. 4 figs.

  17. Kinetic analysis of the template effect in ribooligoguanylate elongation

    NASA Technical Reports Server (NTRS)

    Kanavarioti, Anastassia; White, David H.

    1987-01-01

    The paper presents kinetic studies on the reaction of elongation of the 3-prime-5-prime-linked ribooligoguanylates with guanosine 5-prime-phospho-2-methylimidazolide (2-MelmpG) in the presence or absence of a complementary template, the polycytidylic acid. In the absence of poly(C), the reaction leads to three isomeric oligomers that are elongated by one monomer unit: the 3-prime-5-prime linked, the 2-prime-5-prime linked, and the pyrophosphate, formed in a ratio of 1:2:5. In the presence of the template, the reaction is 20-fold faster and yields products (n + 1), (n + 2), (n + 3), etc., as long as 2-MelmpG is available. The formation of the natural, 3-prime-5-prime-linked isomer, is enhanced selectively by 140-fold at 37 C, and its relative yield increases with decreasing temperature.

  18. The interplay of stiffness and force anisotropies drives embryo elongation.

    PubMed

    Vuong-Brender, Thanh Thi Kim; Ben Amar, Martine; Pontabry, Julien; Labouesse, Michel

    2017-02-15

    The morphogenesis of tissues, like the deformation of an object, results from the interplay between their material properties and the mechanical forces exerted on them. The importance of mechanical forces in influencing cell behaviour is widely recognized, whereas the importance of tissue material properties, in particular stiffness, has received much less attention. Using Caenorhabditis elegans as a model, we examine how both aspects contribute to embryonic elongation. Measuring the opening shape of the epidermal actin cortex after laser nano-ablation, we assess the spatiotemporal changes of actomyosin-dependent force and stiffness along the antero-posterior and dorso-ventral axis. Experimental data and analytical modelling show that myosin-II-dependent force anisotropy within the lateral epidermis, and stiffness anisotropy within the fiber-reinforced dorso-ventral epidermis are critical in driving embryonic elongation. Together, our results establish a quantitative link between cortical tension, material properties and morphogenesis of an entire embryo.

  19. Achieving elongated lesions employing cardiac cryoablation: a preclinical evaluation study.

    PubMed

    Seger, M; Fischer, G; Handler, M; Stöger, M; Nowak, C-N; Hintringer, F; Klima, G; Baumgartner, C

    2012-10-01

    Cardiac cryoablation applied for treating cardiac arrhythmias has shown promising results after intervention, particularly for the creation of elongated lesions. A model for simulating and assessing cryoablation interventions was developed, evaluated and validated with animal experiments. We employed two simulations of different freezing outlet settings for a loop shaped cryocatheter, applying Pennes heat equation for cardiac tissue. Our experiments demonstrated that an equidistantly spaced freezing outlet distribution of 5mm led to an improved formation of lesions, i.e., elongated lesions were observed throughout the transmural cardiac volume and on the epicardial structure. A complete transmural frozen lesion was not achieved with a freezing outlet distance of 10mm. These simulation results could be experimentally verified by morphological and histological examinations. Using our simulation model we were able to optimize the intervention procedure by predicting and assessing the freezing process. This should further increase the success rate of cardiac cryoablation in clinical interventions.

  20. Nitrogen deficiency inhibits leaf blade growth in Lolium perenne by increasing cell cycle duration and decreasing mitotic and post-mitotic growth rates.

    PubMed

    Kavanová, Monika; Lattanzi, Fernando Alfredo; Schnyder, Hans

    2008-06-01

    Nitrogen deficiency severely inhibits leaf growth. This response was analysed at the cellular level by growing Lolium perenne L. under 7.5 mM (high) or 1 mM (low) nitrate supply, and performing a kinematic analysis to assess the effect of nitrogen status on cell proliferation and cell growth in the leaf blade epidermis. Low nitrogen supply reduced leaf elongation rate (LER) by 43% through a similar decrease in the cell production rate and final cell length. The former was entirely because of a decreased average cell division rate (0.023 versus 0.032 h(-1)) and thus longer cell cycle duration (30 versus 22 h). Nitrogen status did not affect the number of division cycles of the initial cell's progeny (5.7), and accordingly the meristematic cell number (53). Meristematic cell length was unaffected by nitrogen deficiency, implying that the division and mitotic growth rates were equally impaired. The shorter mature cell length arose from a considerably reduced post-mitotic growth rate (0.033 versus 0.049 h(-1)). But, nitrogen stress did not affect the position where elongation stopped, and increased cell elongation duration. In conclusion, nitrogen deficiency limited leaf growth by increasing the cell cycle duration and decreasing mitotic and post-mitotic elongation rates, delaying cell maturation.

  1. Effects of transcription elongation rate and Xrn2 exonuclease activity on RNA polymerase II termination suggest widespread kinetic competition

    PubMed Central

    Fong, Nova; Brannan, Kristopher; Erickson, Benjamin; Kim, Hyunmin; Cortazar, Michael; Sheridan, Ryan M.; Nguyen, Tram; Karp, Shai; Bentley, David L.

    2015-01-01

    Summary The torpedo model of transcription termination asserts that the exonuclease Xrn2 attacks the 5′PO4-end exposed by nascent RNA cleavage and chases down the RNA polymerase. We tested this mechanism using a dominant-negative human Xrn2 mutant and found that it delayed termination genome-wide. Xrn2 nuclease inactivation caused strong termination defects downstream of most poly(A) sites and modest delays at some histone and U snRNA genes suggesting that the torpedo mechanism is not limited to poly(A) site-dependent termination. A central untested feature of the torpedo model is that there is kinetic competition between the exonuclease and the pol II elongation complex. Using pol II rate mutants, we found that slow transcription robustly shifts termination upstream, and fast elongation extends the zone of termination further downstream. These results suggest that kinetic competition between elongating pol II and the Xrn2 exonuclease is integral to termination of transcription on most human genes. PMID:26474067

  2. Morphodynamics of pure elongating dunes: Implications for sediment flux in the Ténéré desert

    NASA Astrophysics Data System (ADS)

    Narteau, C.; Lucas, A.; Rodriguez, S.; Callot, Y.; Garcia, A.; Courrech Du Pont, S.

    2015-12-01

    Although they are a very common bedforms in terrestrial sand seas, description of linear dune growth, either by extension or lateral migration is still hindered by our limited understanding of the underlying mechanisms. Therefore, sand flux estimates in arid regions relies essentially on the migration speed of barchan dunes but not on the dynamics of linear dunes despite their abundance. Here we use half a century of high-resolution aerial and satellite imagery of the Ténéré desert, the world's largest source of mineral aerosols, to demonstrate that linear dunes can elongate in the direction of the resultant sand flux with no lateral migration. As they form away from topographic obstacles in a zone of low sediment availability experiencing multimodal winds, these elongating structures are ideal to isolate and quantify dune growth by pure extension. Using similar conditions in a numerical model, we show how deposition downstream of low hills may result in nucleation and development of bedforms. From pure elongation, we derive the local sand flux parallel to the linear dune crests. Together with sand flux estimates perpendicular to the barchan dune crests, this study indicates that two independent dune growth mechanisms can now be used for reconstructing sediment transport and wind conditions from dune morphodynamics.

  3. CRMP4 and CRMP2 Interact to Coordinate Cytoskeleton Dynamics, Regulating Growth Cone Development and Axon Elongation

    PubMed Central

    Tan, Minghui; Cha, Caihui; Ye, Yongheng; Zhang, Jifeng; Li, Sumei; Wu, Fengming; Gong, Sitang; Guo, Guoqing

    2015-01-01

    Cytoskeleton dynamics are critical phenomena that underpin many fundamental cellular processes. Collapsin response mediator proteins (CRMPs) are highly expressed in the developing nervous system, mediating growth cone guidance, neuronal polarity, and axonal elongation. However, whether and how CRMPs associate with microtubules and actin coordinated cytoskeletal dynamics remain unknown. In this study, we demonstrated that CRMP2 and CRMP4 interacted with tubulin and actin in vitro and colocalized with the cytoskeleton in the transition-zone in developing growth cones. CRMP2 and CRMP4 also interacted with one another coordinately to promote growth cone development and axonal elongation. Genetic silencing of CRMP2 enhanced, whereas overexpression of CRMP2 suppressed, the inhibitory effects of CRMP4 knockdown on axonal development. In addition, knockdown of CRMP2 or overexpression of truncated CRMP2 reversed the promoting effect of CRMP4. With the overexpression of truncated CRMP2 or CRMP4 lacking the cytoskeleton interaction domain, the promoting effect of CRMP was suppressed. These data suggest a model in which CRMP2 and CRMP4 form complexes to bridge microtubules and actin and thus work cooperatively to regulate growth cone development and axonal elongation. PMID:26064693

  4. Effects of Transcription Elongation Rate and Xrn2 Exonuclease Activity on RNA Polymerase II Termination Suggest Widespread Kinetic Competition.

    PubMed

    Fong, Nova; Brannan, Kristopher; Erickson, Benjamin; Kim, Hyunmin; Cortazar, Michael A; Sheridan, Ryan M; Nguyen, Tram; Karp, Shai; Bentley, David L

    2015-10-15

    The torpedo model of transcription termination asserts that the exonuclease Xrn2 attacks the 5'PO4-end exposed by nascent RNA cleavage and chases down the RNA polymerase. We tested this mechanism using a dominant-negative human Xrn2 mutant and found that it delayed termination genome-wide. Xrn2 nuclease inactivation caused strong termination defects downstream of most poly(A) sites and modest delays at some histone and U snRNA genes, suggesting that the torpedo mechanism is not limited to poly(A) site-dependent termination. A central untested feature of the torpedo model is that there is kinetic competition between the exonuclease and the pol II elongation complex. Using pol II rate mutants, we found that slow transcription robustly shifts termination upstream, and fast elongation extends the zone of termination further downstream. These results suggest that kinetic competition between elongating pol II and the Xrn2 exonuclease is integral to termination of transcription on most human genes. Copyright © 2015 Elsevier Inc. All rights reserved.

  5. A review of elongation of os calcis for flat feet.

    PubMed

    Phillips, G E

    1983-01-01

    Between 1959 and 1974 the late Dillwyn Evans treated severe symptomatic flat feet by elongating the os calcis. The long-term follow-up of 20 of these patients with a total of 23 feet is presented 7 to 20 years after the operation. At review 17 of the 23 feet showed very good or good results and it was concluded that this is a useful procedure for severe cases of flat feet which appears to stand the test of time.

  6. Neuroprotective copper bis(thiosemicarbazonato) complexes promote neurite elongation.

    PubMed

    Bica, Laura; Liddell, Jeffrey R; Donnelly, Paul S; Duncan, Clare; Caragounis, Aphrodite; Volitakis, Irene; Paterson, Brett M; Cappai, Roberto; Grubman, Alexandra; Camakaris, James; Crouch, Peter J; White, Anthony R

    2014-01-01

    Abnormal biometal homeostasis is a central feature of many neurodegenerative disorders including Alzheimer's disease (AD), Parkinson's disease (PD), and motor neuron disease. Recent studies have shown that metal complexing compounds behaving as ionophores such as clioquinol and PBT2 have robust therapeutic activity in animal models of neurodegenerative disease; however, the mechanism of neuroprotective action remains unclear. These neuroprotective or neurogenerative processes may be related to the delivery or redistribution of biometals, such as copper and zinc, by metal ionophores. To investigate this further, we examined the effect of the bis(thiosemicarbazonato)-copper complex, Cu(II)(gtsm) on neuritogenesis and neurite elongation (neurogenerative outcomes) in PC12 neuronal-related cultures. We found that Cu(II)(gtsm) induced robust neurite elongation in PC12 cells when delivered at concentrations of 25 or 50 nM overnight. Analogous effects were observed with an alternative copper bis(thiosemicarbazonato) complex, Cu(II)(atsm), but at a higher concentration. Induction of neurite elongation by Cu(II)(gtsm) was restricted to neurites within the length range of 75-99 µm with a 2.3-fold increase in numbers of neurites in this length range with 50 nM Cu(II)(gtsm) treatment. The mechanism of neurogenerative action was investigated and revealed that Cu(II)(gtsm) inhibited cellular phosphatase activity. Treatment of cultures with 5 nM FK506 (calcineurin phosphatase inhibitor) resulted in analogous elongation of neurites compared to 50 nM Cu(II)(gtsm), suggesting a potential link between Cu(II)(gtsm)-mediated phosphatase inhibition and neurogenerative outcomes.

  7. Directional ultrasonic backscattering in polycrystals with elongated grains

    NASA Astrophysics Data System (ADS)

    Lobkis, O. I.; Yang, L.; Li, J.; Rokhlin, S. I.

    2012-05-01

    An analytical solution for a three dimensional integral representation of the backscattering (BS) coefficient in polycrystals with elongated grains is obtained. The theory was applied to evaluation of experimental data in Ti alloy with duplex microstructure, which consists of micro-textured regions (MTR) and smaller crystallites. Experiment shows that for microstructure characterization there is significant advantage in using the directional ratios of backscattering coefficients instead their absolute values for data analysis.

  8. Solitary waves in elongated clouds of strongly interacting bosons

    SciTech Connect

    Oegren, M.; Kavoulakis, G.M.; Jackson, A.D.

    2005-08-15

    We examine the propagation of solitary waves in elongated clouds of trapped bosonic atoms as the confinement, the strength of the interatomic interaction, and the atom density are varied. We identify three different physical regimes and develop a general formalism that allows us to interpolate between them. Finally we pay special attention to the transition to the Tonks-Girardeau limit of strongly interacting bosons.

  9. Neuroprotective Copper Bis(thiosemicarbazonato) Complexes Promote Neurite Elongation

    PubMed Central

    Bica, Laura; Liddell, Jeffrey R.; Donnelly, Paul S.; Duncan, Clare; Caragounis, Aphrodite; Volitakis, Irene; Paterson, Brett M.; Cappai, Roberto; Grubman, Alexandra; Camakaris, James; Crouch, Peter J.; White, Anthony R.

    2014-01-01

    Abnormal biometal homeostasis is a central feature of many neurodegenerative disorders including Alzheimer's disease (AD), Parkinson's disease (PD), and motor neuron disease. Recent studies have shown that metal complexing compounds behaving as ionophores such as clioquinol and PBT2 have robust therapeutic activity in animal models of neurodegenerative disease; however, the mechanism of neuroprotective action remains unclear. These neuroprotective or neurogenerative processes may be related to the delivery or redistribution of biometals, such as copper and zinc, by metal ionophores. To investigate this further, we examined the effect of the bis(thiosemicarbazonato)-copper complex, CuII(gtsm) on neuritogenesis and neurite elongation (neurogenerative outcomes) in PC12 neuronal-related cultures. We found that CuII(gtsm) induced robust neurite elongation in PC12 cells when delivered at concentrations of 25 or 50 nM overnight. Analogous effects were observed with an alternative copper bis(thiosemicarbazonato) complex, CuII(atsm), but at a higher concentration. Induction of neurite elongation by CuII(gtsm) was restricted to neurites within the length range of 75–99 µm with a 2.3-fold increase in numbers of neurites in this length range with 50 nM CuII(gtsm) treatment. The mechanism of neurogenerative action was investigated and revealed that CuII(gtsm) inhibited cellular phosphatase activity. Treatment of cultures with 5 nM FK506 (calcineurin phosphatase inhibitor) resulted in analogous elongation of neurites compared to 50 nM CuII(gtsm), suggesting a potential link between CuII(gtsm)-mediated phosphatase inhibition and neurogenerative outcomes. PMID:24587210

  10. A Note on Elongations of Summable QTAG-Modules

    PubMed Central

    Mehdi, Alveera; Naji, Sabah A. R. K.

    2013-01-01

    A right module M over an associative ring with unity is a QTAG-module if every finitely generated submodule of any homomorphic image of M is a direct sum of uniserial modules. In this paper we find a suitable condition under which a special ω-elongation of a summable QTAG-module by a (ω+k)-projective QTAG-module is also a summable QTAG-module. PMID:24459429

  11. Clamped-filament elongation model for actin-based motors.

    PubMed Central

    Dickinson, Richard B; Purich, Daniel L

    2002-01-01

    Although actin-based motility drives cell crawling and intracellular locomotion of organelles and certain pathogens, the underlying mechanism of force generation remains a mystery. Recent experiments demonstrated that Listeria exhibit episodes of 5.4-nm stepwise motion corresponding to the periodicity of the actin filament subunits, and extremely small positional fluctuations during the intermittent pauses [S. C. Kuo and J. L. McGrath. 2000. Nature. 407:1026-1029]. These findings suggest that motile bacteria remain firmly bound to actin filament ends as they elongate, a behavior that appears to rule out previous models for actin-based motility. We propose and analyze a new mechanochemical model (called the "Lock, Load & Fire" mechanism) for force generation by means of affinity-modulated, clamped-filament elongation. During the locking step, the filament's terminal ATP-containing subunit binds tightly to a clamp situated on the surface of a motile object; in the loading step, actin.ATP monomer(s) bind to the filament end, an event that triggers the firing step, wherein ATP hydrolysis on the clamped subunit attenuates the filament's affinity for the clamp. This last step initiates translocation of the new ATP-containing terminus to the clamp, whereupon another cycle begins anew. This model explains how surface-tethered filaments can grow while exerting flexural or tensile force on the motile surface. Moreover, stochastic simulations of the model reproduce the signature motions of Listeria. This elongation motor, which we term actoclampin, exploits actin's intrinsic ATPase activity to provide a simple, high-fidelity enzymatic reaction cycle for force production that does not require elongating filaments to dissociate from the motile surface. This mechanism may operate whenever actin polymerization is called upon to generate the forces that drive cell crawling or intracellular organelle motility. PMID:11806905

  12. Investigation of Impact Load Absorption through Suspension Line Elongation

    DTIC Science & Technology

    1952-12-01

    16 1. Charts . . ’ . . . .. . . 16 2. glong~tion Ratin of Li; Goups . . . 163. Graphs . .. .. .. .. .. .. .. ... . 16 SECTION IV - DISCUSSION OF...Tester . ...................... z14 Figure 16 . Frazier Air Porosity Tester in Use ....... 215 Figure 17. 30 ft., Extended Skirt CsnoW’ in Deployment Bag...line than on canopies strung with high elongation line. WMADR 5&~5T 1 CONCLUSIONS; 15. Nylon is superior to fortisan in shock absorbing capacity. 16

  13. Leaf hydraulics II: vascularized tissues.

    PubMed

    Rockwell, Fulton E; Holbrook, N Michele; Stroock, Abraham D

    2014-01-07

    Current models of leaf hydration employ an Ohm's law analogy of the leaf as an ideal capacitor, neglecting the resistance to flow between cells, or treat the leaf as a plane sheet with a source of water at fixed potential filling the mid-plane, neglecting the discrete placement of veins as well as their resistance. We develop a model of leaf hydration that considers the average conductance of the vascular network to a representative areole (region bounded by the vascular network), and represent the volume of tissue within the areole as a poroelastic composite of cells and air spaces. Solutions to the 3D flow problem are found by numerical simulation, and these results are then compared to 1D models with exact solutions for a range of leaf geometries, based on a survey of temperate woody plants. We then show that the hydration times given by these solutions are well approximated by a sum of the ideal capacitor and plane sheet times, representing the time for transport through the vasculature and tissue respectively. We then develop scaling factors relating this approximate solution to the 3D model, and examine the dependence of these scaling factors on leaf geometry. Finally, we apply a similar strategy to reduce the dimensions of the steady state problem, in the context of peristomatal transpiration, and consider the relation of transpirational gradients to equilibrium leaf water potential measurements. © 2013 Published by Elsevier Ltd. All rights reserved.

  14. Mechanism of gibberellin-dependent stem elongation in peas

    NASA Technical Reports Server (NTRS)

    Cosgrove, D. J.; Sovonick-Dunford, S. A.

    1989-01-01

    Stem elongation in peas (Pisum sativum L.) is under partial control by gibberellins, yet the mechanism of such control is uncertain. In this study, we examined the cellular and physical properties that govern stem elongation, to determine how gibberellins influence pea stem growth. Stem elongation of etiolated seedlings was retarded with uniconozol, a gibberellin synthesis inhibitor, and the growth retardation was reversed by exogenous gibberellin. Using the pressure probe and vapor pressure osmometry, we found little effect of uniconozol and gibberellin on cell turgor pressure or osmotic pressure. In contrast, these treatments had major effects on in vivo stress relaxation, measured by turgor relaxation and pressure-block techniques. Uniconozol-treated plants exhibited reduced wall relaxation (both initial rate and total amount). The results show that growth retardation is effected via a reduction in the wall yield coefficient and an increase in the yield threshold. These effects were largely reversed by exogenous gibberellin. When we measured the mechanical characteristics of the wall by stress/strain (Instron) analysis, we found only minor effects of uniconozol and gibberellin on the plastic compliance. This observation indicates that these agents did not alter wall expansion through effects on the mechanical (viscoelastic) properties of the wall. Our results suggest that wall expansion in peas is better viewed as a chemorheological, rather than a viscoelastic, process.

  15. Ethylene-promoted Elongation: an Adaptation to Submergence Stress

    PubMed Central

    Jackson, Michael B.

    2008-01-01

    Background A sizeable minority of taxa is successful in areas prone to submergence. Many such plants elongate with increased vigour when underwater. This helps to restore contact with the aerial environment by shortening the duration of inundation. Poorly adapted species are usually incapable of this underwater escape. Scope Evidence implicating ethylene as the principal factor initiating fast underwater elongation by leaves or stems is evaluated comprehensively along with its interactions with other hormones and gases. These interactions make up a sequence of events that link the perception of submergence to a prompt acceleration of extension. The review encompasses whole plant physiology, cell biology and molecular genetics. It includes assessments of how submergence threatens plant life and of the extent to which the submergence escape demonstrably improves the likelihood of survival. Conclusions Experimental testing over many years establishes ethylene-promoted underwater extension as one of the most convincing examples of hormone-mediated stress adaptation by plants. The research has utilized a wide range of species that includes numerous angiosperms, a fern and a liverwort. It has also benefited from detailed physiological and molecular studies of underwater elongation by rice (Oryza sativa) and the marsh dock (Rumex palustris). Despite complexities and interactions, the work reveals that the signal transduction pathway is initiated by the simple expediency of physical entrapment of ethylene within growing cells by a covering of water. PMID:17956854

  16. Mechanism of gibberellin-dependent stem elongation in peas

    NASA Technical Reports Server (NTRS)

    Cosgrove, D. J.; Sovonick-Dunford, S. A.

    1989-01-01

    Stem elongation in peas (Pisum sativum L.) is under partial control by gibberellins, yet the mechanism of such control is uncertain. In this study, we examined the cellular and physical properties that govern stem elongation, to determine how gibberellins influence pea stem growth. Stem elongation of etiolated seedlings was retarded with uniconozol, a gibberellin synthesis inhibitor, and the growth retardation was reversed by exogenous gibberellin. Using the pressure probe and vapor pressure osmometry, we found little effect of uniconozol and gibberellin on cell turgor pressure or osmotic pressure. In contrast, these treatments had major effects on in vivo stress relaxation, measured by turgor relaxation and pressure-block techniques. Uniconozol-treated plants exhibited reduced wall relaxation (both initial rate and total amount). The results show that growth retardation is effected via a reduction in the wall yield coefficient and an increase in the yield threshold. These effects were largely reversed by exogenous gibberellin. When we measured the mechanical characteristics of the wall by stress/strain (Instron) analysis, we found only minor effects of uniconozol and gibberellin on the plastic compliance. This observation indicates that these agents did not alter wall expansion through effects on the mechanical (viscoelastic) properties of the wall. Our results suggest that wall expansion in peas is better viewed as a chemorheological, rather than a viscoelastic, process.

  17. ACL reconstruction: in vivo measurement of patellar tendon graft elongation.

    PubMed

    Berruto, M; Howe, J G; Beynnon, B D; Johnson, R J; Nichols, C E; Pope, M H

    1991-06-01

    The implantation of a free autogenous patellar tendon graft is the surgical technique that currently offers the best results in anterior cruciate ligament reconstruction. However, numerous aspects regarding both technique and postoperative rehabilitation can still be improved. The aim of this study was to measure the elongation of the patellar tendon in vivo in the operating room after reconstructive surgery, subjecting the knee to normal strain such as passive mobilization or anterior displacement of the tibia. Three volunteers were studied. Our results were different from those reported in a previous study conducted in vivo on a normal anterior cruciate ligament (ACL). In spite of the isometric position of the tendon, passive mobilization provoked a progressive increase in the elongation of the graft within each cycle of flexion-extension and between one cycle and the next. This also occurred during the Lachman test. These findings suggest that the graft undergoes a process of tensile adjustment when it is first put under strain. Continued elongation once this process appears stabilized raises doubts as to the reliability of isometric measuring devices.

  18. Thin blanket designs for the Elongated Tokamak Commercial Reactor

    SciTech Connect

    Wong, C.P.C.; Bourque, R.F.; Cheng, E.T.; Creedon, R.L.; Schultz, K.R.

    1986-11-01

    The Elongated Tokamak (ET)* is an innovative concept that uses as highly elongated plasma (plasma height-to-width ratio of 6-10) to allow high plasma current and high toroidal betas. ET has the potential for the development of small-size, high-power density, low-cost fusion reactors using normal conducting coils. The elongated plasma shape is achieved by use of a continuous stack of PF coils parallel to the plasma surface on both inbound and outbound sides. To achieve plasma stability, these coil stacks must be located no further than one plasma minor radius from the plasma edge, greatly restricting the space available for blankets. In order to assess the potential of a small reactor, the authors evaluated and designed blankets 30 to 40 cm thick. Three different thin blanket designs were found to be acceptable: FLiBe self-cooled, helium-cooled lithium, and helium-cooled 17Li83Pb blanket designs. A lithium-cooled integrated blanket-coil design (BLITZ-coil) was also found to be suitable for the ET commercial reactors.

  19. Role of dipole elongation in orientationally ordered liquids

    NASA Astrophysics Data System (ADS)

    Wei, Dong-Qing; Gao, Lin; Zhang, Jiao; Yan, Li-Wei; Hu, Jin-He; Chen, Lang; Gong, Zi-Zheng; Guo, Yong-Xin; Han, Yu

    2011-06-01

    A recent study shows that the dipole elongation in the extended dipole model plays a significant role in the phase transitions of liquid crystal phases. In this paper, molecular dynamics (MD) simulations were performed for the dipole model with different distances between the two charges keeping the total dipole moment the same. The potential energy consists of the Lennard-Jones potential and the site-site electrostatic contribution of partial charges. Detailed analyses were made with respect to the average order parameters and as functions of density along with other thermodynamic properties. When the reduced dipole elongations are 0.16 and 0.32, respectively, it is shown that the chainlike structures in the low density regime, liquid phases with columnar and smectic orders, and solid phases are formed; the phase with nematic order is not present anymore. At 0.64, the phases with antiferroelectric order were favored. The transition is found at the reduced elongation 0.55. It shows that the phase transitions are quite sensitive to the molecular charge distribution; this simple system could exhibit rather rich phase behaviors, which represents a significant advance in identifying molecular and state parameters of the future ferroelectric liquids.

  20. Mechanism of gibberellin-dependent stem elongation in peas.

    PubMed

    Cosgrove, D J; Sovonick-Dunford, S A

    1989-01-01

    Stem elongation in peas (Pisum sativum L.) is under partial control by gibberellins, yet the mechanism of such control is uncertain. In this study, we examined the cellular and physical properties that govern stem elongation, to determine how gibberellins influence pea stem growth. Stem elongation of etiolated seedlings was retarded with uniconozol, a gibberellin synthesis inhibitor, and the growth retardation was reversed by exogenous gibberellin. Using the pressure probe and vapor pressure osmometry, we found little effect of uniconozol and gibberellin on cell turgor pressure or osmotic pressure. In contrast, these treatments had major effects on in vivo stress relaxation, measured by turgor relaxation and pressure-block techniques. Uniconozol-treated plants exhibited reduced wall relaxation (both initial rate and total amount). The results show that growth retardation is effected via a reduction in the wall yield coefficient and an increase in the yield threshold. These effects were largely reversed by exogenous gibberellin. When we measured the mechanical characteristics of the wall by stress/strain (Instron) analysis, we found only minor effects of uniconozol and gibberellin on the plastic compliance. This observation indicates that these agents did not alter wall expansion through effects on the mechanical (viscoelastic) properties of the wall. Our results suggest that wall expansion in peas is better viewed as a chemorheological, rather than a viscoelastic, process.

  1. Photo-oxidation of LDPE: Effects on elongational viscosity

    NASA Astrophysics Data System (ADS)

    Rolón-Garrido, Víctor H.; Wagner, Manfred H.

    2013-04-01

    Sheets of low-density polyethylene (LDPE) were photo-oxidatively treated at room temperature, and subsequently characterized rheologically in the melt state by shear and uniaxial extensional experiments. For photo-oxidation, a xenon lamp was used to irradiate the samples for times between 1 day and 6 weeks. Linear-viscoelastic characterization was performed in a temperature range of 130 to 220°C to obtain the master curve at 170°C, the reference temperature at which the elongational viscosities were measured. Linear viscoelasticity is increasingly affected by increasing photo-oxidation due to crosslinking of LDPE, as corroborated by an increasing gel fraction as determined by a solvent extraction method. The elongational measurements reveal a strong enhancement of strain hardening until a saturation level is achieved. The elongational data are analyzed in the frame work of two constitutive equations, the rubber-like liquid and the molecular stress function models. Within the experimental window, time-deformation separability is confirmed for all samples, independent of the degree of photo-oxidation.

  2. Localization of Stem Elongation Control in Cucumis sativus L. 1

    PubMed Central

    Sandhu, M. S.; Lockard, R. G.; Kasperbauer, M. J.

    1974-01-01

    Reciprocal grafts, and applications of gibberellin (GA) and indoleacetic acid (IAA) were used to localize the site of control for stem elongation in cucumber (Cucumis sativus L.). Dwarf and tall plants were reciprocally grafted to determine influence of stems and roots on stem elongation. At 21 days there were no significant differences in length between stems grafted to their own roots and those grafted to roots of the other type. GA3, GA4+7, and IAA were applied to seedlings with and without live apical buds. Seedlings with live apical buds responded to level of added GA, but not to added IAA. GA4+7 was more effective than GA3. Hypocotyls of tall plants responded more to both GA treatments than did those of the dwarves when both types had live apical buds. When either GA4+7 or IAA was applied to seedlings with dead apical buds, elongation of the hypocotyl responded to level of the growth regulator, but there was no difference in response between the dwarf and tall plants. PMID:16658820

  3. Multiscale quantification of tissue behavior during amniote embryo axis elongation.

    PubMed

    Bénazéraf, Bertrand; Beaupeux, Mathias; Tchernookov, Martin; Wallingford, Allison; Salisbury, Tasha; Shirtz, Amelia; Shirtz, Andrew; Huss, David; Pourquié, Olivier; François, Paul; Lansford, Rusty

    2017-08-23

    Embryonic axis elongation is a complex multi-tissue morphogenetic process responsible for the formation of the posterior part of the amniote body. How movements and growth are coordinated between the different posterior tissues (e.g. neural tube, axial and paraxial mesoderm, lateral plate, ectoderm, endoderm) to drive axis morphogenesis remain largely unknown. Here, we use quail embryos to quantify cell behavior and tissue movements during elongation. We quantify the tissue-specific contribution to axis elongation by using 3D volumetric techniques, then quantify tissue-specific parameters such as cell density and proliferation. To study cell behavior at a multi-tissue scale, we used high-resolution 4D imaging of transgenic quail embryos expressing fluorescent proteins. We developed specific tracking and image analysis techniques to analyze cell motion and compute tissue deformations in 4D. This analysis reveals extensive sliding between tissues during axis extension. Further quantification of tissue tectonics showed patterns of rotations, contractions and expansions, which are coherent with the multi-tissue behavior observed previously. Our approach defines a quantitative and multiscale method to analyze the coordination between tissue behaviors during early vertebrate embryo morphogenetic events. © 2017. Published by The Company of Biologists Ltd.

  4. Maize YABBY genes drooping leaf1 and drooping leaf2 affect agronomic traits by regulating leaf architecture

    USDA-ARS?s Scientific Manuscript database

    Leaf architectural traits, such as length, width and angle, directly influence canopy structure and light penetration, photosynthate production and overall yield. We discovered and characterized a maize (Zea mays) mutant with aberrant leaf architecture we named drooping leaf1 (drl1), as leaf blades ...

  5. Active suppression of a leaf meristem orchestrates determinate leaf growth.

    PubMed

    Alvarez, John Paul; Furumizu, Chihiro; Efroni, Idan; Eshed, Yuval; Bowman, John L

    2016-10-06

    Leaves are flat determinate organs derived from indeterminate shoot apical meristems. The presence of a specific leaf meristem is debated, as anatomical features typical of meristems are not present in leaves. Here we demonstrate that multiple NGATHA (NGA) and CINCINNATA-class-TCP (CIN-TCP) transcription factors act redundantly, shortly after leaf initiation, to gradually restrict the activity of a leaf meristem in Arabidopsis thaliana to marginal and basal domains, and that their absence confers persistent marginal growth to leaves, cotyledons and floral organs. Following primordia initiation, the restriction of the broadly acting leaf meristem to the margins is mediated by the juxtaposition of adaxial and abaxial domains and maintained by WOX homeobox transcription factors, whereas other marginal elaboration genes are dispensable for its maintenance. This genetic framework parallels the morphogenetic program of shoot apical meristems and may represent a relic of an ancestral shoot system from which seed plant leaves evolved.

  6. Leaf Relative Water Content Estimated from Leaf Reflectance and Transmittance

    NASA Technical Reports Server (NTRS)

    Vanderbilt, Vern; Daughtry, Craig; Dahlgren, Robert

    2016-01-01

    Remotely sensing the water status of plants and the water content of canopies remain long term goals of remote sensing research. In the research we report here, we used optical polarization techniques to monitor the light reflected from the leaf interior, R, as well as the leaf transmittance, T, as the relative water content (RWC) of corn (Zea mays) leaves decreased. Our results show that R and T both change nonlinearly. The result show that the nonlinearities cancel in the ratio R/T, which appears linearly related to RWC for RWC less than 90%. The results suggest that potentially leaf water status and perhaps even canopy water status could be monitored starting from leaf and canopy optical measurements.

  7. Leaf chlorophyll content as a proxy for leaf photosynthetic capacity.

    PubMed

    Croft, Holly; Chen, Jing M; Luo, Xiangzhong; Bartlett, Paul; Chen, Bin; Staebler, Ralf M

    2017-09-01

    Improving the accuracy of estimates of forest carbon exchange is a central priority for understanding ecosystem response to increased atmospheric CO2 levels and improving carbon cycle modelling. However, the spatially continuous parameterization of photosynthetic capacity (Vcmax) at global scales and appropriate temporal intervals within terrestrial biosphere models (TBMs) remains unresolved. This research investigates the use of biochemical parameters for modelling leaf photosynthetic capacity within a deciduous forest. Particular attention is given to the impacts of seasonality on both leaf biophysical variables and physiological processes, and their interdependent relationships. Four deciduous tree species were sampled across three growing seasons (2013-2015), approximately every 10 days for leaf chlorophyll content (ChlLeaf ) and canopy structure. Leaf nitrogen (NArea ) was also measured during 2014. Leaf photosynthesis was measured during 2014-2015 using a Li-6400 gas-exchange system, with A-Ci curves to model Vcmax. Results showed that seasonality and variations between species resulted in weak relationships between Vcmax normalized to 25°C (Vcmax25) and NArea (R(2)  = 0.62, P < 0.001), whereas ChlLeaf demonstrated a much stronger correlation with Vcmax25 (R(2)  = 0.78, P < 0.001). The relationship between ChlLeaf and NArea was also weak (R(2)  = 0.47, P < 0.001), possibly due to the dynamic partitioning of nitrogen, between and within photosynthetic and nonphotosynthetic fractions. The spatial and temporal variability of Vcmax25 was mapped using Landsat TM/ETM satellite data across the forest site, using physical models to derive ChlLeaf . TBMs largely treat photosynthetic parameters as either fixed constants or varying according to leaf nitrogen content. This research challenges assumptions that simple NArea -Vcmax25 relationships can reliably be used to constrain photosynthetic capacity in TBMs, even within the same plant functional type. It

  8. Grain Size Dependence of Uniform Elongation in Single-Phase FCC/BCC Metals

    NASA Astrophysics Data System (ADS)

    Liu, Haiting; Shen, Yao; Ma, Jiawei; Zheng, Pengfei; Zhang, Lei

    2016-09-01

    We studied the dependence of uniform elongation on grain size in the range of submicron to millimeter for single-phase FCC/BCC metals by reviewing recent experimental results and applying crystal plasticity finite element method simulation. In the order of increasing grain size, uniform elongation can be divided into three stages, namely low elongation stage, nearly constant elongation stage, and decreased elongation with large scatters stage. Low elongation stage features a dramatic increase near the critical grain size at the end of the stage, which is primarily attributed to the emergence of dislocation cell size transition from ultrafine to mid-size grain. Other factors can be neglected due to their negligible influence on overall variation trend. In nearly constant elongation stage, uniform elongation remains unchanged at a high level in general. As grain size keeps growing, uniform elongation starts decreasing and becomes scattered upon a certain grain size, indicating the initiation of decreased elongation with large scatters stage. It is shown that the increase is not linear or smooth but rather sharp at the end of low elongation stage, leading to a wider range in nearly constant elongation stage. The grain size dependence of uniform elongation can serve as a guiding principle for designing small uniaxial tensile specimens for mechanical testing, where size effect matters in most cases.

  9. Rice HOX12 Regulates Panicle Exsertion by Directly Modulating the Expression of ELONGATED UPPERMOST INTERNODE1[OPEN

    PubMed Central

    Gao, Shaopei; Fang, Jun; Xu, Fan; Wang, Wei

    2016-01-01

    Bioactive gibberellins (GAs) are key endogenous regulators of plant growth. Previous work identified ELONGATED UPPERMOST INTERNODE1 (EUI1) as a GA-deactivating enzyme that plays an important role in panicle exsertion from the flag leaf sheath in rice (Oryza sativa). However, the mechanism that regulates EUI1 activity during development is still largely unexplored. In this study, we identified the dominant panicle enclosure mutant regulator of eui1 (ree1-D), whose phenotype is caused by the activation of the homeodomain-leucine zipper transcription factor HOX12. Diminished HOX12 expression by RNA interference enhanced panicle exsertion, mimicking the eui1 phenotype. HOX12 knockdown plants contain higher levels of the major biologically active GAs (such as GA1 and GA4) than the wild type. The expression of EUI1 is elevated in the ree1-D mutant but reduced in HOX12 knockdown plants. Interestingly, both HOX12 and EUI1 are predominantly expressed in panicles, where GA4 is highly accumulated. Yeast one-hybrid, electrophoretic mobility shift assay, and chromatin immunoprecipitation analyses showed that HOX12 physically interacts with the EUI1 promoter both in vitro and in vivo. Furthermore, plants overexpressing HOX12 in the eui1 mutant background retained the elongated uppermost internode phenotype. These results indicate that HOX12 acts directly through EUI1 to regulate panicle exsertion in rice. PMID:26977084

  10. Leaf fall as a source of leaf miner mortality.

    PubMed

    Pritchard, I M; James, R

    1984-09-01

    Leaf miner deaths resulting from the death of their leaves were assessd by collecting falling leaves of holm oak and beech. The Phyllonorycter mines thus captured were examined to ascertain the cause of death. For both mining species the mortality from leaf shedding accounted for less than 2.8% of the mining cohorts. It is argued that the level of mortality is insufficient for population regulation, as has been previously suggested.

  11. Light quality-mediated petiole elongation in Arabidopsis during shade avoidance involves cell wall modification by xyloglucan endotransglucosylase/hydrolases.

    PubMed

    Sasidharan, Rashmi; Chinnappa, C C; Staal, Marten; Elzenga, J Theo M; Yokoyama, Ryusuke; Nishitani, Kazuhiko; Voesenek, Laurentius A C J; Pierik, Ronald

    2010-10-01

    Some plants can avoid shaded conditions via rapid shoot elongation, thus growing into better lit areas in a canopy. Cell wall-modifying mechanisms promoting this elongation response, therefore, are important regulatory points during shade avoidance. Two major cell wall-modifying protein families are expansins and xyloglucan endotransglucosylase/hydrolases (XTHs). The role of these proteins during shade avoidance was studied in Arabidopsis (Arabidopsis thaliana). In response to two shade cues, low red to far-red light (implying neighbor proximity) and green shade (mimicking dense canopy conditions), Arabidopsis showed classic shade avoidance features: petiole elongation and leaf hyponasty. Measurement of the apoplastic proton flux in green shade-treated petioles revealed a rapid efflux of protons into the apoplast within minutes, unlike white light controls. This apoplastic acidification probably provides the acidic pH required for the optimal activity of cell wall-modifying proteins like expansins and XTHs. Acid-induced extension, expansin susceptibility, and extractable expansin activity were similar in petioles from white light- and shade-treated plants. XTH activity, however, was high in petioles exposed to shade treatments. Five XTH genes (XTH9, -15, -16, -17, and -19) were positively regulated by low red to far-red light conditions, while the latter four and XTH22 showed a significant up-regulation also in response to green shade. Consistently, knockout mutants for two of these XTH genes also had reduced or absent shade avoidance responses to these light signals. These results point toward the cell wall as a vital regulatory point during shade avoidance.

  12. A general method for calculating the optimal leaf longevity from the viewpoint of carbon economy.

    PubMed

    Seki, Motohide; Yoshida, Tomohiko; Takada, Takenori

    2015-09-01

    According to the viewpoint of the optimal strategy theory, a tree is expected to shed its leaves when they no longer contribute to maximisation of net carbon gain. Several theoretical models have been proposed in which a tree was assumed to strategically shed an old deteriorated leaf to develop a new leaf. We mathematically refined an index used in a previous theoretical model [Kikuzawa (Am Nat 138:1250-1263, 1991)] so that the index is exactly proportional to a tree's lifelong net carbon gain. We also incorporated a tree's strategy that determines the timing of leaf expansion, and examined three kinds of strategies. Specifically, we assumed that a new leaf is expanded (1) immediately after shedding of an old leaf, (2) only at the beginning of spring, or (3) immediately after shedding of an old leaf if the shedding occurs during a non-winter season and at the beginning of spring otherwise. We derived a measure of optimal leaf longevity maximising the value of an appropriate index reflecting total net carbon gain and show that use of this index yielded results that are qualitatively consistent with empirical records. The model predicted that expanding a new leaf at the beginning of spring than immediately after shedding usually yields higher carbon gain, and combined strategy of the immediate replacement and the spring flushing earned the highest gain. In addition, our numerical analyses suggested that multiple flushing seen in a few species of subtropical zones can be explained in terms of carbon economy.

  13. Distinct palisade tissue development processes promoted by leaf autonomous signalling and long-distance signalling in Arabidopsis thaliana.

    PubMed

    Munekage, Yuri Nakajima; Inoue, Shio; Yoneda, Yuki; Yokota, Akiho

    2015-06-01

    Plants develop palisade tissue consisting of cylindrical mesophyll cells located at the adaxial side of leaves in response to high light. To understand high light signalling in palisade tissue development, we investigated leaf autonomous and long-distance signal responses of palisade tissue development using Arabidopsis thaliana. Illumination of a developing leaf with high light induced cell height elongation, whereas illumination of mature leaves with high light increased cell density and suppressed cell width expansion in palisade tissue of new leaves. Examination using phototropin1 phototropin2 showed that blue light signalling mediated by phototropins was involved in cell height elongation of the leaf autonomous response rather than the cell density increase induced by long-distance signalling. Hydrogen peroxide treatment induced cylindrical palisade tissue cell formation in both a leaf autonomous and long-distance manner, suggesting involvement of oxidative signals. Although constitutive expression of transcription factors involved in systemic-acquired acclimation to excess light, ZAT10 and ZAT12, induced cylindrical palisade tissue cell formation, knockout of these genes did not affect cylindrical palisade tissue cell formation. We conclude that two distinct signalling pathways - leaf autonomous signalling mostly dependent on blue light signalling and long-distance signalling from mature leaves that sense high light and oxidative stress - control palisade tissue development in A. thaliana.

  14. 7 CFR 29.3036 - Leaf surface.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 2 2014-01-01 2014-01-01 false Leaf surface. 29.3036 Section 29.3036 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing... Leaf surface. The smoothness or roughness of the web or lamina of a tobacco leaf. Leaf surface is...

  15. 7 CFR 29.3036 - Leaf surface.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Leaf surface. 29.3036 Section 29.3036 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing... Leaf surface. The smoothness or roughness of the web or lamina of a tobacco leaf. Leaf surface is...

  16. Diffuse and specular characteristics of leaf reflectance

    NASA Technical Reports Server (NTRS)

    Grant, Lois

    1987-01-01

    In this paper, the evolution of current understanding of the mechanisms of leaf reflectance is reviewed. The use of measurements of polarized reflectance to separate leaf reflectance into diffuse and specular components is discussed. A section on the factors influencing leaf reflectance - leaf structure and physiological disturbances - is included along with discussion on the manner in which these influences are manifested.

  17. 7 CFR 29.3036 - Leaf surface.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 2 2012-01-01 2012-01-01 false Leaf surface. 29.3036 Section 29.3036 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing... Leaf surface. The smoothness or roughness of the web or lamina of a tobacco leaf. Leaf surface is...

  18. 7 CFR 29.3036 - Leaf surface.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 2 2011-01-01 2011-01-01 false Leaf surface. 29.3036 Section 29.3036 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing... Leaf surface. The smoothness or roughness of the web or lamina of a tobacco leaf. Leaf surface is...

  19. 7 CFR 29.3036 - Leaf surface.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 2 2013-01-01 2013-01-01 false Leaf surface. 29.3036 Section 29.3036 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing... Leaf surface. The smoothness or roughness of the web or lamina of a tobacco leaf. Leaf surface is...

  20. Leaf acclimation to light availability supports rapid growth in tall Picea sitchensis trees.

    PubMed

    Chin, Alana R O; Sillett, Stephen C

    2017-03-21

    Leaf-level anatomical variation is readily apparent within tall tree crowns, yet the relative importance of water and light availability in controlling this variation remains unclear. Sitka spruce (Picea sitchensis, (Bong.) Carr.) thrives in temperate rainforests of the Pacific Northwest, where it has historically reached heights >100 m, despite rarely living more than 400 years alongside redwoods that are five times older. We examined leaves of trees up to 97 m tall using a combination of transverse sections, longitudinal sections, epidermal imprints and whole-leaf measurements to explore the combined effects of water stress and light availability on leaf development in P. sitchensis. In contrast to the situation in tall Cupressaceae, light availability-not hydraulic limitation-is the primary ecological driver of leaf-level anatomical variation in P. sitchensis. While height-associated decreases in leaf length and mesoporosity are best explained by hydrostatic constraints on leaf elongation, the majority of anatomical traits we measured reflect acclimation to light availability, including increases in leaf width and vascular tissue areas in the brightest parts of the crown. Along with these changes, the appearance of abaxial stomata in the bright upper crown, and the arrangement of mesophyll in uniseriate, transverse plates-with radially arranged apoplastic pathways leading directly to stomata before bridging them with a V-shaped cell-may enhance gas exchange and hydraulic conductivity. This suite of leaf traits suggests an adaptive strategy that maximizes photosynthesis at the expense of water-stress tolerance. Anatomical investigations spanning the height gradient in tall tree crowns build our understanding of mechanisms underlying among-species variation in growth rates, life spans, and potential responses to climate change. © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  1. Relative Mesothelioma Potencies for Unregulated Respirable Elongated Mineral and Synthetic Particles

    EPA Science Inventory

    For decades uncertainties and contradictions have surrounded the issue of whether exposures to respirable elongated mineral and synthetic particles (REMPs and RESPs) present health risks such as those recognized for exposures to elongated asbestiform mineral particles from the fi...

  2. Relative Mesothelioma Potencies for Unregulated Respirable Elongated Mineral and Synthetic Particles

    EPA Science Inventory

    For decades uncertainties and contradictions have surrounded the issue of whether exposures to respirable elongated mineral and synthetic particles (REMPs and RESPs) present health risks such as those recognized for exposures to elongated asbestiform mineral particles from the fi...

  3. Experiments in Whole Leaf Photosynthesis

    ERIC Educational Resources Information Center

    Stewart, J. C.; And Others

    1974-01-01

    Described is a simple experimental system, which uses radioactive carbon dioxide to study whole leaf photosynthesis under a variety of conditions. Other experiments and simple apparatus for the experiments are also described. (Author/RH)

  4. Near infrared leaf reflectance modeling

    NASA Technical Reports Server (NTRS)

    Parrish, J. B.

    1985-01-01

    Near infrared leaf reflectance modeling using Fresnel's equation (Kumar and Silva, 1973) and Snell's Law successfully approximated the spectral curve for a 0.25-mm turgid oak leaf lying on a Halon background. Calculations were made for ten interfaces, air-wax, wax-cellulose, cellulose-water, cellulose-air, air-water, and their inverses. A water path of 0.5 mm yielded acceptable results, and it was found that assignment of more weight to those interfaces involving air versus water or cellulose, and less to those involving wax, decreased the standard deviation of the error for all wavelengths. Data suggest that the air-cell interface is not the only important contributor to the overall reflectance of a leaf. Results also argue against the assertion that the near infrared plateau is a function of cell structure within the leaf.

  5. Hormonal Regulation of Leaf Abscission

    PubMed Central

    Jacobs, William P.

    1968-01-01

    A review is given of the progress made during the last 6 years in elucidating the nature, locus of action, and transport properties of the endogenous hormones that control leaf abscission. PMID:16657014

  6. Experiments in Whole Leaf Photosynthesis

    ERIC Educational Resources Information Center

    Stewart, J. C.; And Others

    1974-01-01

    Described is a simple experimental system, which uses radioactive carbon dioxide to study whole leaf photosynthesis under a variety of conditions. Other experiments and simple apparatus for the experiments are also described. (Author/RH)

  7. Legumes are different: Leaf nitrogen, photosynthesis, and water use efficiency.

    PubMed

    Adams, Mark Andrew; Turnbull, Tarryn L; Sprent, Janet I; Buchmann, Nina

    2016-04-12

    Using robust, pairwise comparisons and a global dataset, we show that nitrogen concentration per unit leaf mass for nitrogen-fixing plants (N2FP; mainly legumes plus some actinorhizal species) in nonagricultural ecosystems is universally greater (43-100%) than that for other plants (OP). This difference is maintained across Koppen climate zones and growth forms and strongest in the wet tropics and within deciduous angiosperms. N2FP mostly show a similar advantage over OP in nitrogen per leaf area (Narea), even in arid climates, despite diazotrophy being sensitive to drought. We also show that, for most N2FP, carbon fixation by photosynthesis (Asat) and stomatal conductance (gs) are not related to Narea-in distinct challenge to current theories that place the leaf nitrogen-Asat relationship at the center of explanations of plant fitness and competitive ability. Among N2FP, only forbs displayed an Narea-gs relationship similar to that for OP, whereas intrinsic water use efficiency (WUEi; Asat/gs) was positively related to Narea for woody N2FP. Enhanced foliar nitrogen (relative to OP) contributes strongly to other evolutionarily advantageous attributes of legumes, such as seed nitrogen and herbivore defense. These alternate explanations of clear differences in leaf N between N2FP and OP have significant implications (e.g., for global models of carbon fluxes based on relationships between leaf N and Asat). Combined, greater WUE and leaf nitrogen-in a variety of forms-enhance fitness and survival of genomes of N2FP, particularly in arid and semiarid climates.

  8. Legumes are different: Leaf nitrogen, photosynthesis, and water use efficiency

    PubMed Central

    Adams, Mark Andrew; Turnbull, Tarryn L.; Sprent, Janet I.; Buchmann, Nina

    2016-01-01

    Using robust, pairwise comparisons and a global dataset, we show that nitrogen concentration per unit leaf mass for nitrogen-fixing plants (N2FP; mainly legumes plus some actinorhizal species) in nonagricultural ecosystems is universally greater (43–100%) than that for other plants (OP). This difference is maintained across Koppen climate zones and growth forms and strongest in the wet tropics and within deciduous angiosperms. N2FP mostly show a similar advantage over OP in nitrogen per leaf area (Narea), even in arid climates, despite diazotrophy being sensitive to drought. We also show that, for most N2FP, carbon fixation by photosynthesis (Asat) and stomatal conductance (gs) are not related to Narea—in distinct challenge to current theories that place the leaf nitrogen–Asat relationship at the center of explanations of plant fitness and competitive ability. Among N2FP, only forbs displayed an Narea–gs relationship similar to that for OP, whereas intrinsic water use efficiency (WUEi; Asat/gs) was positively related to Narea for woody N2FP. Enhanced foliar nitrogen (relative to OP) contributes strongly to other evolutionarily advantageous attributes of legumes, such as seed nitrogen and herbivore defense. These alternate explanations of clear differences in leaf N between N2FP and OP have significant implications (e.g., for global models of carbon fluxes based on relationships between leaf N and Asat). Combined, greater WUE and leaf nitrogen—in a variety of forms—enhance fitness and survival of genomes of N2FP, particularly in arid and semiarid climates. PMID:27035971

  9. Why do leaf-tying caterpillars abandon their leaf ties?

    PubMed Central

    Sliwinski, Michelle

    2013-01-01

    Leaf-tying caterpillars act as ecosystem engineers by building shelters between overlapping leaves, which are inhabited by other arthropods. Leaf-tiers have been observed to leave their ties and create new shelters (and thus additional microhabitats), but the ecological factors affecting shelter fidelity are poorly known. For this study, we explored the effects of resource limitation and occupant density on shelter fidelity and assessed the consequences of shelter abandonment. We first quantified the area of leaf material required for a caterpillar to fully develop for two of the most common leaf-tiers that feed on white oak, Quercus alba. On average, Psilocorsis spp. caterpillars consumed 21.65 ± 0.67 cm2 leaf material to complete development. We also measured the area of natural leaf ties found in a Maryland forest, to determine the distribution of resources available to caterpillars in situ. Of 158 natural leaf ties examined, 47% were too small to sustain an average Psilocorsis spp. caterpillar for the entirety of its development. We also manipulated caterpillar densities within experimental ties on potted trees to determine the effects of cohabitants on the likelihood of a caterpillar to leave its tie. We placed 1, 2, or 4 caterpillars in ties of a standard size and monitored the caterpillars twice daily to track their movement. In ties with more than one occupant, caterpillars showed a significantly greater propensity to leave their tie, and left sooner and at a faster rate than those in ties as single occupants. To understand the consequences of leaf tie abandonment, we observed caterpillars searching a tree for a site to build a shelter in the field. This is a risky behavior, as 17% of the caterpillars observed died while searching for a shelter site. Caterpillars that successfully built a shelter traveled 110 ± 20 cm and took 28 ± 7 min to find a suitable site to build a shelter. In conclusion, leaf-tying caterpillars must frequently abandon their leaf

  10. Why do leaf-tying caterpillars abandon their leaf ties?

    PubMed

    Sliwinski, Michelle; Sigmon, Elisha

    2013-01-01

    Leaf-tying caterpillars act as ecosystem engineers by building shelters between overlapping leaves, which are inhabited by other arthropods. Leaf-tiers have been observed to leave their ties and create new shelters (and thus additional microhabitats), but the ecological factors affecting shelter fidelity are poorly known. For this study, we explored the effects of resource limitation and occupant density on shelter fidelity and assessed the consequences of shelter abandonment. We first quantified the area of leaf material required for a caterpillar to fully develop for two of the most common leaf-tiers that feed on white oak, Quercus alba. On average, Psilocorsis spp. caterpillars consumed 21.65 ± 0.67 cm(2) leaf material to complete development. We also measured the area of natural leaf ties found in a Maryland forest, to determine the distribution of resources available to caterpillars in situ. Of 158 natural leaf ties examined, 47% were too small to sustain an average Psilocorsis spp. caterpillar for the entirety of its development. We also manipulated caterpillar densities within experimental ties on potted trees to determine the effects of cohabitants on the likelihood of a caterpillar to leave its tie. We placed 1, 2, or 4 caterpillars in ties of a standard size and monitored the caterpillars twice daily to track their movement. In ties with more than one occupant, caterpillars showed a significantly greater propensity to leave their tie, and left sooner and at a faster rate than those in ties as single occupants. To understand the consequences of leaf tie abandonment, we observed caterpillars searching a tree for a site to build a shelter in the field. This is a risky behavior, as 17% of the caterpillars observed died while searching for a shelter site. Caterpillars that successfully built a shelter traveled 110 ± 20 cm and took 28 ± 7 min to find a suitable site to build a shelter. In conclusion, leaf-tying caterpillars must frequently abandon their leaf

  11. Increasing leaf hydraulic conductance with transpiration rate minimizes the water potential drawdown from stem to leaf.

    PubMed

    Simonin, Kevin A; Burns, Emily; Choat, Brendan; Barbour, Margaret M; Dawson, Todd E; Franks, Peter J

    2015-03-01

    Leaf hydraulic conductance (k leaf) is a central element in the regulation of leaf water balance but the properties of k leaf remain uncertain. Here, the evidence for the following two models for k leaf in well-hydrated plants is evaluated: (i) k leaf is constant or (ii) k leaf increases as transpiration rate (E) increases. The difference between stem and leaf water potential (ΔΨstem-leaf), stomatal conductance (g s), k leaf, and E over a diurnal cycle for three angiosperm and gymnosperm tree species growing in a common garden, and for Helianthus annuus plants grown under sub-ambient, ambient, and elevated atmospheric CO₂ concentration were evaluated. Results show that for well-watered plants k leaf is positively dependent on E. Here, this property is termed the dynamic conductance, k leaf(E), which incorporates the inherent k leaf at zero E, which is distinguished as the static conductance, k leaf(0). Growth under different CO₂ concentrations maintained the same relationship between k leaf and E, resulting in similar k leaf(0), while operating along different regions of the curve owing to the influence of CO₂ on g s. The positive relationship between k leaf and E minimized variation in ΔΨstem-leaf. This enables leaves to minimize variation in Ψleaf and maximize g s and CO₂ assimilation rate over the diurnal course of evaporative demand.

  12. Increasing leaf hydraulic conductance with transpiration rate minimizes the water potential drawdown from stem to leaf

    PubMed Central

    Simonin, Kevin A.; Burns, Emily; Choat, Brendan; Barbour, Margaret M.; Dawson, Todd E.; Franks, Peter J.

    2015-01-01

    Leaf hydraulic conductance (k leaf) is a central element in the regulation of leaf water balance but the properties of k leaf remain uncertain. Here, the evidence for the following two models for k leaf in well-hydrated plants is evaluated: (i) k leaf is constant or (ii) k leaf increases as transpiration rate (E) increases. The difference between stem and leaf water potential (ΔΨstem–leaf), stomatal conductance (g s), k leaf, and E over a diurnal cycle for three angiosperm and gymnosperm tree species growing in a common garden, and for Helianthus annuus plants grown under sub-ambient, ambient, and elevated atmospheric CO2 concentration were evaluated. Results show that for well-watered plants k leaf is positively dependent on E. Here, this property is termed the dynamic conductance, k leaf(E), which incorporates the inherent k leaf at zero E, which is distinguished as the static conductance, k leaf(0). Growth under different CO2 concentrations maintained the same relationship between k leaf and E, resulting in similar k leaf(0), while operating along different regions of the curve owing to the influence of CO2 on g s. The positive relationship between k leaf and E minimized variation in ΔΨstem–leaf. This enables leaves to minimize variation in Ψleaf and maximize g s and CO2 assimilation rate over the diurnal course of evaporative demand. PMID:25547915

  13. NtSCP1 from tobacco is an extracellular serine carboxypeptidase III that has an impact on cell elongation.

    PubMed

    Bienert, Manuela Désirée; Delannoy, Mélanie; Navarre, Catherine; Boutry, Marc

    2012-03-01

    The leaf extracellular space contains several peptidases, most of which are of unknown function. We isolated cDNAs for two extracellular serine carboxypeptidase III genes from tobacco (Nicotiana tabacum), NtSCP1 and NtSCP2, belonging to a phylogenetic clade not yet functionally characterized in plants. NtSCP1 and NtSCP2 are orthologs derived from the two ancestors of tobacco. Reverse transcription-polymerase chain reaction analysis showed that NtSCP1 and NtSCP2 are expressed in root, stem, leaf, and flower tissues. Expression analysis of the β-glucuronidase reporter gene fused to the NtSCP1 transcription promoter region confirmed this expression profile. Western blotting of NtSCP1 and expression of an NtSCP1-green fluorescent protein fusion protein showed that the protein is located in the extracellular space of tobacco leaves and culture cells. Purified His-tagged NtSCP1 had carboxypeptidase activity in vitro. Transgenic tobacco plants overexpressing NtSCP1 showed a reduced flower length due to a decrease in cell size. Etiolated seedlings of these transgenic plants had shorter hypocotyls. These data provide support for a role of an extracellular type III carboxypeptidase in the control of cell elongation.

  14. Effects of water deficit on radicle apex elongation and solute accumulation in Zea mays L.

    PubMed

    Velázquez-Márquez, S; Conde-Martínez, V; Trejo, C; Delgado-Alvarado, A; Carballo, A; Suárez, R; Mascorro, J O; Trujillo, A R

    2015-11-01

    In this study, we examined the effects of water deficit on the elongation of radicles of maize seedlings and on the accumulation of solutes in the radicle apices of two maize varieties: VS-22 (tolerant) and AMCCG-2 (susceptible). Sections of radicle corresponding to the first 2 mm of the primary roots were marked with black ink, and the seedlings were allowed to grow for 24, 48, and 72 h in polyvinyl chloride (PVC) tubes filled with vermiculite at three different water potentials (Ψ(w), -0.03, -1.0, and -1.5 MPa). The radicle elongation, sugar accumulation, and proline accumulation were determined after each of the growth periods specified above. The Ψ(w) of the substrate affected the dynamics of primary root elongation in both varieties. In particular, the lowest Ψ(w) (-1.5 MPa) inhibited root development by 72% and 90% for the VS-22 and AMCCG-2 varieties, respectively. The osmotic potential (Ψ(o)) was reduced substantially in both varieties to maintain root turgor; however, VS-22 had a higher root turgor (0.67 MPa) than AMCCG-2 (0.2 MPa). These results suggest that both varieties possess a capacity for osmotic adjustment. Sugar began to accumulate within the first 24 h of radicle apex growth. The sugar concentration was higher in VS-22 root apices compared to AMCCG-2, and the amount of sugar accumulation increased with a decrease in Ψ(w). Significant amounts of trehalose accumulated in VS-22 and AMCCG-2 (29.8 μmol/g fresh weight [FW] and 5.24 μmol/g FW, respectively). Starch accumulation in the root apices of these two maize varieties also differed significantly, with a lower level in VS-22. In both varieties, the proline concentration also increased as a consequence of the water deficit. At 72 h, the proline concentration in VS-22 (16.2 μmol/g FW) was almost 3 times greater than that in AMCCG-2 (5.19 μmol/g FW). Trehalose also showed a 3-fold increase in the tolerant variety. Accumulation of these solutes in the root growth zone may indicate an osmotic

  15. 7 CFR 29.2528 - Leaf.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 2 2012-01-01 2012-01-01 false Leaf. 29.2528 Section 29.2528 Agriculture Regulations...-Cured Tobacco (u.s. Types 22, 23, and Foreign Type 96) § 29.2528 Leaf. Whole, unstemmed leaf. Leaf, when applied to tobacco in strip form, shall describe the divided unit of a whole leaf. [49 FR 16757, Apr. 20...

  16. 7 CFR 29.2528 - Leaf.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Leaf. 29.2528 Section 29.2528 Agriculture Regulations...-Cured Tobacco (u.s. Types 22, 23, and Foreign Type 96) § 29.2528 Leaf. Whole, unstemmed leaf. Leaf, when applied to tobacco in strip form, shall describe the divided unit of a whole leaf. [49 FR 16757, Apr. 20...

  17. 7 CFR 29.2528 - Leaf.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 2 2011-01-01 2011-01-01 false Leaf. 29.2528 Section 29.2528 Agriculture Regulations...-Cured Tobacco (u.s. Types 22, 23, and Foreign Type 96) § 29.2528 Leaf. Whole, unstemmed leaf. Leaf, when applied to tobacco in strip form, shall describe the divided unit of a whole leaf. [49 FR 16757, Apr. 20...

  18. Species of Cercospora associated with grey leaf spot of maize

    PubMed Central

    Crous, Pedro W.; Groenewald, Johannes Z.; Groenewald, Marizeth; Caldwell, Pat; Braun, Uwe; Harrington, Thomas C.

    2006-01-01

    Grey leaf spot is a serious yield-reducing disease of maize (Zea mays) in many parts of the world where this crop is cultivated. The causal organism associated with the disease is Cercospora zeae-maydis. Two potential sibling species have been recognized as Groups I and II. The DNA sequences for the internal transcribed spacers (ITS1 & ITS2), the 5.8S rRNA gene, elongation factor 1-α, histone H3, actin and calmodulin gene regions suggest that Groups I and II are two distinct species. Furthermore, Cercospora zeae-maydis (Group I) can be distinguished from C. zeina sp. nov. (Group II) by its faster growth rate on artificial media, the ability to produce cercosporin, longer conidiophores, and broadly fusiform conidia. A PCR-based test that distinguishes the two species was developed using species-specific primers designed from the histone H3 gene. PMID:18490979

  19. Species of Cercospora associated with grey leaf spot of maize.

    PubMed

    Crous, Pedro W; Groenewald, Johannes Z; Groenewald, Marizeth; Caldwell, Pat; Braun, Uwe; Harrington, Thomas C

    2006-01-01

    Grey leaf spot is a serious yield-reducing disease of maize (Zea mays) in many parts of the world where this crop is cultivated. The causal organism associated with the disease is Cercospora zeae-maydis. Two potential sibling species have been recognized as Groups I and II. The DNA sequences for the internal transcribed spacers (ITS1 & ITS2), the 5.8S rRNA gene, elongation factor 1-alpha, histone H3, actin and calmodulin gene regions suggest that Groups I and II are two distinct species. Furthermore, Cercospora zeae-maydis (Group I) can be distinguished from C. zeina sp. nov. (Group II) by its faster growth rate on artificial media, the ability to produce cercosporin, longer conidiophores, and broadly fusiform conidia. A PCR-based test that distinguishes the two species was developed using species-specific primers designed from the histone H3 gene.

  20. Embryoidogenesis and plant regeneration from leaf tissue of Gloriosa superba.

    PubMed

    Sivakumar, G; Krishnamurthy, K V; Rajendran, T D

    2003-05-01

    The induction, maturation and germination of embryoids from leaf tissue of Gloriosa superba L. were developed by exploiting solid and liquid culture. Nodular calli were obtained from SH medium supplemented with 2,4-D and 2iP. In solid culture, the nodular calli when transferred to 2,4-D along with glycerol gave the best response (68.4 %) in embryoid induction after 20 days. After two subcultures at 7-day intervals in a medium with thiamine instead of glycerol, the embryoids matured. When mature embryoids were transferred to BAP and IBA medium, they gave rise to plantlets with single shoots and roots. In liquid culture, the medium supplemented with NAA and L-glutamine with continuous agitation, the embryoidogenic calli produced embryoids (85 %) after 21 days. The mature embryoids began to turn green and produced shoots and elongated "radicles" after 35 days.

  1. Tbx1 is Necessary for Palatal Elongation and Elevation

    PubMed Central

    Goudy, Steven; Law, Amy; Sanchez, Gabriela; Baldwin, H. Scott; Brown, Christopher

    2010-01-01

    The transcription factor TBX1 is a key mediator of developmental abnormalities associated with DiGeorge/Velocardiofacial Syndrome. Studies in mice have demonstrated that decreased dosage of Tbx1 results in defects in pharyngeal arch, cardiovascular, and craniofacial development. The role of Tbx1 in cardiac development has been intensely studied; however, its role in palatal development is poorly understood. By studying the Tbx1-/- mice we found defects during the critical points of palate elongation and elevation. The intrinsic palate defects in the Tbx1-/- mice were determined by measuring changes in palate shelf length, proliferation, apoptosis, expression of relevant growth factors, and in palate fusion assays. Tbx1-/- embryos exhibit cleft palate with failed palate elevation in 100% and abnormal palatal-oral fusions in 50%. In the Tbx1-/- mice the palate shelf length was reduced and tongue height was greater, demonstrating a physical impediment to palate elevation and apposition. In vitro palate fusion assays demonstrate that Tbx1-/- palate shelves are capable of fusion but a roller culture assay showed that the null palatal shelves were unable to elongate. Diminished hyaluronic acid production in the Tbx1-/- palate shelves may explain failed palate shelf elevation. In addition, cell proliferation and apoptosis were perturbed in Tbx1-/- palates. A sharp decrease of Fgf8 expression was detected in the Tbx1-/- palate shelves, suggesting that Fgf8 is dependent on Tbx1 in the palate. Fgf10 is also up-regulated in the Tbx1-/- palate shelves and tongue. These data demonstrate that Tbx1 is a critical transcription factor that guides palatal elongation and elevation and that Fgf8 expression in the palate is Tbx1-dependent. PMID:20214979

  2. How do roots elongate in a structured soil?

    PubMed

    Jin, Kemo; Shen, Jianbo; Ashton, Rhys W; Dodd, Ian C; Parry, Martin A J; Whalley, William R

    2013-11-01

    In this review, we examine how roots penetrate a structured soil. We first examine the relationship between soil water status and its mechanical strength, as well as the ability of the soil to supply water to the root. We identify these as critical soil factors, because it is primarily in drying soil that mechanical constraints limit root elongation. Water supply to the root is important because root water status affects growth pressures and root stiffness. To simplify the bewildering complexity of soil-root interactions, the discussion is focused around the special cases of root elongation in soil with pores much smaller than the root diameter and the penetration of roots at interfaces within the soil. While it is often assumed that the former case is well understood, many unanswered questions remain. While low soil-root friction is often viewed as a trait conferring better penetration of strong soils, it may also increase the axial pressure on the root tip and in so doing reduce the rate of cell division and/or expansion. The precise trade-off between various root traits involved in root elongation in homogeneous soil remains to be determined. There is consensus that the most important factors determining root penetration at an interface are the angle at which the root attempts to penetrate the soil, root stiffness, and the strength of the soil to be penetrated. The effect of growth angle on root penetration implicates gravitropic responses in improved root penetration ability. Although there is no work that has explored the effect of the strength of the gravitropic responses on penetration of hard layers, we attempt to outline possible interactions. Impacts of soil drying and strength on phytohormone concentrations in roots, and consequent root-to-shoot signalling, are also considered.

  3. Elongation factor-2: a useful gene for arthropod phylogenetics.

    PubMed

    Regier, J C; Shultz, J W

    2001-07-01

    Robust resolution of controversial higher-level groupings within Arthropoda requires additional sources of characters. Toward this end, elongation factor-2 sequences (1899 nucleotides) were generated from 17 arthropod taxa (5 chelicerates, 6 crustaceans, 3 hexapods, 3 myriapods) plus an onychophoran and a tardigrade as outgroups. Likelihood and parsimony analyses of nucleotide and amino acid data sets consistently recovered Myriapoda and major chelicerate groups with high bootstrap support. Crustacea + Hexapoda (= Pancrustacea) was recovered with moderate support, whereas the conflicting group Myriapoda + Hexapoda (= Atelocerata) was never recovered and bootstrap values were always <5%. With additional nonarthropod sequences included, one indel supports monophyly of Tardigrada, Onychophora, and Arthropoda relative to molluscan, annelidan, and mammalian outgroups. New and previously published sequences from RNA polymerase II (1038 nucleotides) and elongation factor-1alpha (1092 nucleotides) were analyzed for the same taxa. A comparison of bootstrap values from the three genes analyzed separately revealed widely varying values for some clades, although there was never strong support for conflicting groups. In combined analyses, there was strong bootstrap support for the generally accepted clades Arachnida, Arthropoda, Euchelicerata, Hexapoda, and Pycnogonida, and for Chelicerata, Myriapoda, and Pancrustacea, whose monophyly is more controversial. Recovery of some additional groups was fairly robust to method of analysis but bootstrap values were not high; these included Pancrustacea + Chelicerata, Hexapoda + Cephalocarida + Remipedia, Cephalocarida + Remipedia, and Malaocostraca + Cirripedia. Atelocerata (= Myriapoda + Hexapoda) was never recovered. Elongation factor-2 is now the second protein-encoding, nuclear gene (in addition to RNA polymerase II) to support Pancrustacea over Atelocerata. Atelocerata is widely cited in morphology-based analyses, and the

  4. Hypocrea/Trichoderma: species with conidiophore elongations and green conidia.

    PubMed

    Chaverri, Priscila; Castlebury, Lisa A; Overton, Barrie E; Samuels, Gary J

    2003-01-01

    Species of Trichoderma and Hypocrea that have green conidia and sterile or fertile elongations of their conidiophores are described or redescribed and their phylogenetic position explored. The described species include T. crassum, T. fasciculatum, T. fertile, T. hamatum, T. longipile, T. oblongisporum, T. pubescens, T. spirale, T. strictipile, T. strigosum, T. stromaticum, T. tomentosum, Hypocrea aureoviridis f. macrospora, H. ceramica. and H. semiorbis. Trichoderma fasciculatum originally was described from cultures from ascospores of an unidentified Hypocrea specimen; it is considered to be a synonym of T. strictipile. The remaining species of Trichoderma considered here have not been linked to teleomorphs, and the Trichoderma anamorphs of H. aureoviridis f. macrospora and H. semiorbis have not been named. Five new species of Hypocrea are described, viz. H. cremea, H. cuneispora, H. estonica, H. strictipilosa and H. surrotunda. The phylogenetic relationships of these species were inferred based on partial RPB2 and EF-1α DNA sequence data and phenotypic characteristics, including teleomorph, anamorph, colony and growth rates. Trichoderma crassum was found to be a sister species to T. virens, based on molecular sequences and phenotypic data. Hypocrea surrotunda and H. cremea, H. cuneispora and T. longipile, T. fertile and T. oblongisporum, T. tomentosum and H. atrogelatinosa, and T. hamatum and T. pubescens, respectively, were found to be closely related phylogenetically, based on RPB2 and EF-1α gene genealogies. Anamorph and teleomorph phenotype, including conidiophore elongations, phialide morphology, conidial morphology, stroma anatomy and ascospore morphology are not useful predictors of relationships. Despite the shared phenotypic characters of these Trichoderma and Hypocrea species, they are distributed between two major clades of Trichoderma/Hypocrea. Redescriptions and a key to species of Hypocrea/Trichoderma with green conidia and conidiophore

  5. Morphological and Chemical Mechanisms of Elongated Mineral Particle Toxicities

    PubMed Central

    Aust, Ann E.; Cook, Philip M.; Dodson, Ronald F.

    2011-01-01

    Much of our understanding regarding the mechanisms for induction of disease following inhalation of respirable elongated mineral particles (REMP) is based on studies involving the biological effects of asbestos fibers. The factors governing the disease potential of an exposure include duration and frequency of exposures; tissue-specific dose over time; impacts on dose persistence from in vivo REMP dissolution, comminution, and clearance; individual susceptibility; and the mineral type and surface characteristics. The mechanisms associated with asbestos particle toxicity involve two facets for each particle's contribution: (1) the physical features of the inhaled REMP, which include width, length, aspect ratio, and effective surface area available for cell contact; and (2) the surface chemical composition and reactivity of the individual fiber/elongated particle. Studies in cell-free systems and with cultured cells suggest an important way in which REMP from asbestos damage cellular molecules or influence cellular processes. This may involve an unfortunate combination of the ability of REMP to chemically generate potentially damaging reactive oxygen species, through surface iron, and the interaction of the unique surfaces with cell membranes to trigger membrane receptor activation. Together these events appear to lead to a cascade of cellular events, including the production of damaging reactive nitrogen species, which may contribute to the disease process. Thus, there is a need to be more cognizant of the potential impact that the total surface area of REMP contributes to the generation of events resulting in pathological changes in biological systems. The information presented has applicability to inhaled dusts, in general, and specifically to respirable elongated mineral particles. PMID:21534085

  6. Metabolic and Physical Control of Cell Elongation Rate

    PubMed Central

    Green, P. B.; Erickson, R. O.; Buggy, J.

    1971-01-01

    Several levels of control of elongation rate are revealed through the detailed study of responses of the Nitella internode to abrupt shifts in turgor. The immediate response, which apparently reflects the physical state of the cell, is approximately described by the equation r = (P — Y)m where r is rate, P is pressure, Y is the wall's yielding threshold, and m is related to the wall's apparent fluidity (reciprocal viscosity). Because P and Y are in the range 5 to 6 atmospheres, and (P — Y) is roughly 0.2 atmosphere, elongation rate is initially extremely sensitive to changes in P. A small step-down in turgor (0.7 atmosphere) stops growth, and a similar rise greatly accelerates it. These initial responses are, however, soon (15 minutes) compensated by changes in Y. An apparent metabolism-dependent reaction (azide-sensitive) lowers Y; strain hardening (azide-insensitive) raises it. These two opposing processes, acting on Y, serve as a governor on (P — Y), tending to maintain it at a given value despite changes in P. This ability to compensate is itself a function of turgor. Turgor step-downs are less and less well compensated, leading to lower rate, as turgor falls from 5 atmospheres to about 2 atmospheres where growth appears not to resume. This is the lowest attainable yield value, Y1. The turgor dependency of compensation reflects a turgor requirement of the Y-lowering (“wall-softening”) process. Thus the relation between steady state, rs, and turgor is an indirect one, derived from time-dependent alterations of the cell wall. This relationship superficially resembles the instantaneously valid one in that, roughly, rs = (P — Y1)ms. Y1 and ms, however, have much lower values than Y and m. The duality of the elongation rate versus turgor relation and the prominent role of Y in regulating rate are the major features of growth control in Nitella. PMID:16657635

  7. Single-Plane Magnetically Focused Elongated Small Field Proton Beams.

    PubMed

    McAuley, Grant A; Slater, James M; Wroe, Andrew J

    2015-08-01

    We previously performed Monte Carlo simulations of magnetically focused proton beams shaped by a single quadrapole magnet and thereby created narrow elongated beams with superior dose delivery characteristics (compared to collimated beams) suitable for targets of similar geometry. The present study seeks to experimentally validate these simulations using a focusing magnet consisting of 24 segments of samarium cobalt permanent magnetic material adhered into a hollow cylinder. Proton beams with properties relevant to clinical radiosurgery applications were delivered through the magnet to a water tank containing a diode detector or radiochromic film. Dose profiles were analyzed and compared with analogous Monte Carlo simulations. The focused beams produced elongated beam spots with high elliptical symmetry, indicative of magnet quality. Experimental data showed good agreement with simulations, affirming the utility of Monte Carlo simulations as a tool to model the inherent complexity of a magnetic focusing system. Compared to target-matched unfocused simulations, focused beams showed larger peak to entrance ratios (26% to 38%) and focused simulations showed a two-fold increase in beam delivery efficiency. These advantages can be attributed to the magnetic acceleration of protons in the transverse plane that tends to counteract the particle outscatter that leads to degradation of peak to entrance performance in small field proton beams. Our results have important clinical implications and suggest rare earth focusing magnet assemblies are feasible and could reduce skin dose and beam number while delivering enhanced dose to narrow elongated targets (eg, in and around the spinal cord) in less time compared to collimated beams. © The Author(s) 2014.

  8. Fruiting Branch K+ Level Affects Cotton Fiber Elongation Through Osmoregulation

    PubMed Central

    Yang, Jiashuo; Hu, Wei; Zhao, Wenqing; Chen, Binglin; Wang, Youhua; Zhou, Zhiguo; Meng, Yali

    2016-01-01

    Potassium (K) deficiency in cotton plants results in reduced fiber length. As one of the primary osmotica, K+ contributes to an increase in cell turgor pressure during fiber elongation. Therefore, it is hypothesized that fiber length is affected by K deficiency through an osmotic pathway, so in 2012 and 2013, an experiment was conducted to test this hypothesis by imposing three potassium supply regimes (0, 125, 250 kg K ha-1) on a low-K-sensitive cultivar, Siza 3, and a low-K-tolerant cultivar, Simian 3. We found that fibers were longer in the later season bolls than in the earlier ones in cotton plants grown under normal growth conditions, but later season bolls showed a greater sensitivity to low-K stress, especially the low-K sensitive genotype. We also found that the maximum velocity of fibre elongation (Vmax) is the parameter that best reflects the change in fiber elongation under K deficiency. This parameter mostly depends on cell turgor, so the content of the osmotically active solutes was analyzed accordingly. Statistical analysis showed that K+ was the major osmotic factor affecting fiber length, and malate was likely facilitating K+ accumulation into fibers, which enabled the low-K-tolerant genotype to cope with low-K stress. Moreover, the low-K-tolerant genotype tended to have greater K+ absorptive capacities in the upper fruiting branches. Based on our findings, we suggest a fertilization scheme for Gossypium hirsutum that adds extra potash fertilizer or distributes it during the development of late season bolls to mitigate K deficiency in the second half of the growth season and to enhance fiber length in late season bolls. PMID:26834777

  9. Antibacterial activity of stem and leaf extract of Kedrostis foetidissima (Jacq.) Cogn.

    PubMed Central

    Priyavardhini, S.; Gowri, S. Shyamala; Vasantha, K.; Umadevi, M.

    2008-01-01

    The present study aimed at evaluating the antimicrobial activity of chloroform extracts of stem and leaf of Kedrostis foetidissima (jacq.) cogn. (Cucurbitaceae) against Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, Serratia marcescens and Klebsiella pneumoniae. was carried out using agar disc diffusion technique. The results revealed that the chloroform extract of stem presented the highest zone of inhibition against Pseudomonas aeruginosa others show significant zone of inhibition. PMID:22557304

  10. Elongated optical bottle beams generated by composite binary axicons

    NASA Astrophysics Data System (ADS)

    Porfirev, A. P.; Skidanov, R. V.

    2016-04-01

    We provide analytical, numerical and experimental study of the possibility of forming elongated optical bottle beams (OBBs) using composite binary phase axicons. In this case, the OBB is generated by the superposition of Bessel beams in the near-field region on the axicon. To generate the OBB experimentally, we utilized a spatial light modulator. The experimental results are qualitatively consistent with the results of numerical simulations performed using Fresnel transform. Such type of optical trap can be applied in many applications of microbiology, micromechanics and meteorology to manipulate micro- and nanoobjects in liquid or gaseous medium.

  11. Elongated Asteroid Will Safely Pass Earth on Christmas Eve

    NASA Image and Video Library

    2015-12-23

    The elongated asteroid in this radar image, named 2003 SD220, will safely fly past Earth on Thursday, Dec. 24, 2015, at a distance of 6.8 million miles (11 million kilometers). The image was taken on Dec. 22 by scientists using NASA's 230-foot (70-meter) Deep Space Network antenna at Goldstone, California, when the asteroid was approaching its flyby distance. This asteroid is at least 3,600 feet (1,100 meters) long. In 2018, it will safely pass Earth at a distance of 1.8 million miles (2.8 million kilometers). http://photojournal.jpl.nasa.gov/catalog/PIA20280

  12. Connectedness Percolation of Elongated Hard Particles in an External Field

    NASA Astrophysics Data System (ADS)

    Otten, Ronald H. J.; van der Schoot, Paul

    2012-02-01

    A theory is presented of how orienting fields and steric interactions conspire against the formation of a percolating network of, in some sense, connected elongated colloidal particles in fluid dispersions. We find that the network that forms above a critical loading breaks up again at higher loadings due to interaction-induced enhancement of the particle alignment. Upon approach of the percolation threshold, the cluster dimensions diverge with the same critical exponent parallel and perpendicular to the field direction, implying that connectedness percolation is not in the universality class of directed percolation.

  13. Fluorescent Methods to Study Transcription Initiation and Transition into Elongation

    PubMed Central

    Deshpande, Aishwarya P.; Sultana, Shemaila

    2015-01-01

    The DNA-dependent RNA polymerases induce specific conformational changes in the promoter DNA during transcription initiation. Fluorescence spectroscopy sensitively monitors these DNA conformational changes in real time and at equilibrium providing powerful ways to estimate interactions in transcriptional complexes and to assess how transcription is regulated by the promoter DNA sequence, transcription factors, and small ligands. Ensemble fluorescence methods described here probe the individual steps of promoter binding, bending, opening, and transition into the elongation using T7 phage and mitochondrial transcriptional systems as examples. PMID:25095993

  14. Longitudinal domain wall formation in elongated assemblies of ferromagnetic nanoparticles.

    PubMed

    Varón, Miriam; Beleggia, Marco; Jordanovic, Jelena; Schiøtz, Jakob; Kasama, Takeshi; Puntes, Victor F; Frandsen, Cathrine

    2015-09-29

    Through evaporation of dense colloids of ferromagnetic ~13 nm ε-Co particles onto carbon substrates, anisotropic magnetic dipolar interactions can support formation of elongated particle structures with aggregate thicknesses of 100-400 nm and lengths of up to some hundred microns. Lorenz microscopy and electron holography reveal collective magnetic ordering in these structures. However, in contrast to continuous ferromagnetic thin films of comparable dimensions, domain walls appear preferentially as longitudinal, i.e., oriented parallel to the long axis of the nanoparticle assemblies. We explain this unusual domain structure as the result of dipolar interactions and shape anisotropy, in the absence of inter-particle exchange coupling.

  15. Leaf shape evolution has a similar genetic architecture in three edaphic specialists within the Mimulus guttatus species complex.

    PubMed

    Ferris, Kathleen G; Rushton, Tullia; Greenlee, Anna B; Toll, Katherine; Blackman, Benjamin K; Willis, John H

    2015-08-01

    The genetic basis of leaf shape has long interested botanists because leaf shape varies extensively across the plant kingdom and this variation is probably adaptive. However, knowledge of the genetic architecture of leaf shape variation in natural populations remains limited. This study examined the genetic architecture of leaf shape diversification among three edaphic specialists in the Mimulus guttatus species complex. Lobed and narrow leaves have evolved from the entire, round leaves of M. guttatus in M. laciniatus, M. nudatus and a polymorphic serpentine M. guttatus population (M2L). Bulk segregant analysis and next-generation sequencing were used to map quantitative trait loci (QTLs) that underlie leaf shape in an M. laciniatus × M. guttatus F2 population. To determine whether the same QTLs contribute to leaf shape variation in M. nudatus and M2L, F2s from M. guttatus × M. nudatus and lobed M2L × unlobed M. guttatus crosses were genotyped at QTLs from the bulk segregant analysis. Narrow and lobed leaf shapes in M. laciniatus, M. nudatus and M. guttatus are controlled by overlapping genetic regions. Several promising leaf shape candidate genes were found under each QTL. The evolution of divergent leaf shape has taken place multiple times in the M. guttatus species complex and is associated with the occupation of dry, rocky environments. The genetic architecture of elongated and lobed leaves is similar across three species in this group. This may indicate that parallel genetic evolution from standing variation or new mutations is responsible for the putatively adaptive leaf shape variation in Mimulus. © The Author 2015. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  16. Leaf shape evolution has a similar genetic architecture in three edaphic specialists within the Mimulus guttatus species complex

    PubMed Central

    Ferris, Kathleen G.; Rushton, Tullia; Greenlee, Anna B.; Toll, Katherine; Blackman, Benjamin K.; Willis, John H.

    2015-01-01

    Background and Aims The genetic basis of leaf shape has long interested botanists because leaf shape varies extensively across the plant kingdom and this variation is probably adaptive. However, knowledge of the genetic architecture of leaf shape variation in natural populations remains limited. This study examined the genetic architecture of leaf shape diversification among three edaphic specialists in the Mimulus guttatus species complex. Lobed and narrow leaves have evolved from the entire, round leaves of M. guttatus in M. laciniatus, M. nudatus and a polymorphic serpentine M. guttatus population (M2L). Methods Bulk segregant analysis and next-generation sequencing were used to map quantitative trait loci (QTLs) that underlie leaf shape in an M. laciniatus × M. guttatus F2 population. To determine whether the same QTLs contribute to leaf shape variation in M. nudatus and M2L, F2s from M. guttatus × M. nudatus and lobed M2L × unlobed M. guttatus crosses were genotyped at QTLs from the bulk segregant analysis. Key Results Narrow and lobed leaf shapes in M. laciniatus, M. nudatus and M. guttatus are controlled by overlapping genetic regions. Several promising leaf shape candidate genes were found under each QTL. Conclusions The evolution of divergent leaf shape has taken place multiple times in the M. guttatus species complex and is associated with the occupation of dry, rocky environments. The genetic architecture of elongated and lobed leaves is similar across three species in this group. This may indicate that parallel genetic evolution from standing variation or new mutations is responsible for the putatively adaptive leaf shape variation in Mimulus. PMID:26070644

  17. ZEITLUPE positively regulates hypocotyl elongation at warm temperature under light in Arabidopsis thaliana.

    PubMed

    Miyazaki, Yuji; Takase, Tomoyuki; Kiyosue, Tomohiro

    2015-01-01

    Hypocotyl cell elongation has been studied as a model to understand how cellular expansion contributes to plant organ growth. Hypocotyl elongation is affected by multiple environmental factors, including light quantity and light quality. Red light inhibits hypocotyl growth via the phytochrome signaling pathways. Proteins of the flavin-binding KELCH repeat F-box 1 / LOV KELCH protein 2 / ZEITLUPE family are positive regulators of hypocotyl elongation under red light in Arabidopsis. These proteins were suggested to reduce phytochrome-mediated inhibition of hypocotyl elongation. Here, we show that ZEITLUPE also functions as a positive regulator in warmth-induced hypocotyl elongation under light in Arabidopsis.

  18. Leaf-Mediated Light Responses in Petunia Flowers.

    PubMed Central

    Moscovici, S.; Moalem-Beno, D.; Weiss, D.

    1996-01-01

    In the present work we studied the role of light in the regulation of flavonoid gene expression and anthocyanin synthesis in petunia (Petunia hybrida) corollas. We found that light is required for chalcone synthase gene (chs) expression, anthocyanin synthesis, and growth of detached and attached petunia corollas. Although direct illumination induced chs expression, pigmentation, and elongation of the detached corollas, irradiation of green leaves or sepals played the main role in the attached corollas. The duration, intensity, and spectrum of the light reaction suggest that phytochrome-mediated high-irradiance reactions are involved in the regulation of corolla development. Using the photosynthesis inhibitor 3-(3,4-dichlorophenyl)-1,1-dimethylurea, we showed that photosynthesis does not significantly contribute to the leaf-mediated light responses. When sepals were removed or covered. [14C]sucrose up-take by the corolla of detached intact flowers was inhibited. The results of this study suggest that light is perceived by leaves and sepals and enhances corolla sink activity, elongation, pigmentation, and chs expression. The role of leaves and sepals in the light regulation of petunia corolla development is discussed. PMID:12226259

  19. Maintenance of Transcription-Translation Coupling by Elongation Factor P

    PubMed Central

    Elgamal, Sara

    2016-01-01

    ABSTRACT Under conditions of tight coupling between translation and transcription, the ribosome enables synthesis of full-length mRNAs by preventing both formation of intrinsic terminator hairpins and loading of the transcription termination factor Rho. While previous studies have focused on transcription factors, we investigated the role of Escherichia coli elongation factor P (EF-P), an elongation factor required for efficient translation of mRNAs containing consecutive proline codons, in maintaining coupled translation and transcription. In the absence of EF-P, the presence of Rho utilization (rut) sites led to an ~30-fold decrease in translation of polyproline-encoding mRNAs. Coexpression of the Rho inhibitor Psu fully restored translation. EF-P was also shown to inhibit premature termination during synthesis and translation of mRNAs encoding intrinsic terminators. The effects of EF-P loss on expression of polyproline mRNAs were augmented by a substitution in RNA polymerase that accelerates transcription. Analyses of previously reported ribosome profiling and global proteomic data identified several candidate gene clusters where EF-P could act to prevent premature transcription termination. In vivo probing allowed detection of some predicted premature termination products in the absence of EF-P. Our findings support a model in which EF-P maintains coupling of translation and transcription by decreasing ribosome stalling at polyproline motifs. Other regulators that facilitate ribosome translocation through roadblocks to prevent premature transcription termination upon uncoupling remain to be identified. PMID:27624127

  20. Device for measuring hole elongation in a bolted joint

    NASA Technical Reports Server (NTRS)

    Wichorek, Gregory R. (Inventor)

    1987-01-01

    A device to determine the operable failure mode of mechanically fastened lightweight composite joints by measuring the hole elongation of a bolted joint is disclosed. The double-lap joint test apparatus comprises a stud, a test specimen having a hole, two load transfer plates, and linear displacement measuring instruments. The test specimen is sandwiched between the two load transfer plates and clamped together with the stud. Spacer washers are placed between the test specimen and each load transfer plate to provide a known, controllable area for the determination of clamping forces around the hole of the specimen attributable to bolt torque. The spacer washers also provide a gap for the mounting of reference angles on each side of the test specimen. Under tensile loading, elongation of the hole of the test specimen causes the stud to move away from the reference angles. This displacement is measured by the voltage output of two linear displacement measuring instruments that are attached to the stud and remain in contact with the reference angles throughout the tensile loading. The present invention obviates previous problems in obtaining specimen deformation measurements by monitoring the reference angles to the test specimen and the linear displacement measuring instruments to the stud.

  1. Application of an Elongated Kelvin Model to Space Shuttle Foams

    NASA Technical Reports Server (NTRS)

    Sullivan, Roy M.; Ghosn, Louis J.; Lerch, Bradley A.

    2009-01-01

    The space shuttle foams are rigid closed-cell polyurethane foams. The two foams used most-extensively oil space shuttle external tank are BX-265 and NCFL4-124. Because of the foaming and rising process, the foam microstructures are elongated in the rise direction. As a result, these two foams exhibit a nonisotropic mechanical behavior. A detailed microstructural characterization of the two foams is presented. Key features of the foam cells are described and the average cell dimensions in the two foams are summarized. Experimental studies are also conducted to measure the room temperature mechanical response of the two foams in the two principal material directions (parallel to the rise and perpendicular to the rise). The measured elastic modulus, proportional limit stress, ultimate tensile strength, and Poisson's ratios are reported. The generalized elongated Kelvin foam model previously developed by the authors is reviewed and the equations which result from this model are summarized. Using the measured microstructural dimensions and the measured stiffness ratio, the foam tensile strength ratio and Poisson's ratios are predicted for both foams and are compared with the experimental data. The predicted tensile strength ratio is in close agreement with the measured strength ratio for both BX-265 and NCFI24-124. The comparison between the predicted Poisson's ratios and the measured values is not as favorable.

  2. Doc Toxin Is a Kinase That Inactivates Elongation Factor Tu*

    PubMed Central

    Cruz, Jonathan W.; Rothenbacher, Francesca P.; Maehigashi, Tatsuya; Lane, William S.; Dunham, Christine M.; Woychik, Nancy A.

    2014-01-01

    The Doc toxin from bacteriophage P1 (of the phd-doc toxin-antitoxin system) has served as a model for the family of Doc toxins, many of which are harbored in the genomes of pathogens. We have shown previously that the mode of action of this toxin is distinct from the majority derived from toxin-antitoxin systems: it does not cleave RNA; in fact P1 Doc expression leads to mRNA stabilization. However, the molecular triggers that lead to translation arrest are not understood. The presence of a Fic domain, albeit slightly altered in length and at the catalytic site, provided a clue to the mechanism of P1 Doc action, as most proteins with this conserved domain inactivate GTPases through addition of an adenylyl group (also referred to as AMPylation). We demonstrated that P1 Doc added a single phosphate group to the essential translation elongation factor and GTPase, elongation factor (EF)-Tu. The phosphorylation site was at a highly conserved threonine, Thr-382, which was blocked when EF-Tu was treated with the antibiotic kirromycin. Therefore, we have established that Fic domain proteins can function as kinases. This distinct enzymatic activity exhibited by P1 Doc also solves the mystery of the degenerate Fic motif unique to the Doc family of toxins. Moreover, we have established that all characterized Fic domain proteins, even those that phosphorylate, target pivotal GTPases for inactivation through a post-translational modification at a single functionally critical acceptor site. PMID:24448800

  3. The Many Faces of Elongator in Neurodevelopment and Disease

    PubMed Central

    Kojic, Marija; Wainwright, Brandon

    2016-01-01

    Development of the nervous system requires a variety of cellular activities, such as proliferation, migration, axonal outgrowth and guidance and synapse formation during the differentiation of neural precursors into mature neurons. Malfunction of these highly regulated and coordinated events results in various neurological diseases. The Elongator complex is a multi-subunit complex highly conserved in eukaryotes whose function has been implicated in the majority of cellular activities underlying neurodevelopment. These activities include cell motility, actin cytoskeleton organization, exocytosis, polarized secretion, intracellular trafficking and the maintenance of neural function. Several studies have associated mutations in Elongator subunits with the neurological disorders familial dysautonomia (FD), intellectual disability (ID), amyotrophic lateral sclerosis (ALS) and rolandic epilepsy (RE). Here, we review the various cellular activities assigned to this complex and discuss the implications for neural development and disease. Further research in this area has the potential to generate new diagnostic tools, better prevention strategies and more effective treatment options for a wide variety of neurological disorders. PMID:27847465

  4. Molecular Mobility of Soft Segment of Polyurethane Elastomers under Elongation

    NASA Astrophysics Data System (ADS)

    Kojio, Ken; Shimada, Makoto; Motokucho, Suguru; Furukawa, Mutsuhisa

    2008-07-01

    In this study, we investigated molecular mobility of a soft segment in the poly(oxypropylene) glycol (PPG), 4,4'-diphenylmethane diisocyanate (MDI) and 1,4-butane diol (BD)-based polyurethane elastomers (PUE) with and without elongation by dynamic viscoelastic property measurement and pulse nuclear magnetic resonance (NMR) measurement. The peak position of the loss tangent (tand) curves shifted to the lower temperature region with increasing elongation. In the pulse NMR measurement, the long spin-spin relaxation time (T2) component appeared at -18.0(ɛ = 0) and -26.0 °C(ɛ = 1.5), respectively, with increasing temperature. Since this temperature seems to be related to the glass transition temperature (Tg) of the soft segment in the PUE, it is likely to consider that the Tg decreased with increasing strain. These results might be attributed that the size of cooperative motion during the glass transition decrease due to the orientation of the soft segment, and the soft segment phase approach to a pure phase on account of the extraction of the hard segment from the soft segment phase.

  5. Mode-converted ultrasonic scattering in polycrystals with elongated grains.

    PubMed

    Arguelles, Andrea P; Kube, Christopher M; Hu, Ping; Turner, Joseph A

    2016-09-01

    Elastic wave scattering is used to study polycrystalline media for a wide range of applications. Received signals, which include scattering from the randomly oriented grains comprising the polycrystal, contain information from which useful microstructural parameters may often be inferred. Recently, a mode-converted diffuse ultrasonic scattering model was developed for evaluating the scattered response of a transverse wave from an incident longitudinal wave in a polycrystalline medium containing equiaxed single-phase grains with cubic elastic symmetry. In this article, that theoretical mode-converted scattering model is modified to account for grain elongation within the sample. The model shows the dependence on scattering angle relative to the grain axis orientation. Experimental measurements were performed on a sample of 7475-T7351 aluminum using a pitch-catch transducer configuration. The results show that the mode-converted scattering can be used to determine the dimensions of the elongated grains. The average grain shape determined from the experimental measurements is compared with dimensions extracted from electron backscatter diffraction, an electron imaging technique. The results suggest that mode-converted diffuse ultrasonic scattering has the potential to quantify detailed information about grain microstructure.

  6. Cellular dynamics of the negative transcription elongation factor NELF

    SciTech Connect

    Yung, Tetsu M.C.; Narita, Takashi; Komori, Toshiharu; Yamaguchi, Yuki; Handa, Hiroshi

    2009-06-10

    Negative Elongation Factor (NELF) is a transcription factor discovered based on its biochemical activity to suppress transcription elongation, and has since been implicated in various diseases ranging from neurological disorders to cancer. Besides its role in promoter-proximal pausing of RNA polymerase II during early stages of transcription, recently we found that it also plays important roles in the 3'-end processing of histone mRNA. Furthermore, NELF has been found to form a distinct subnuclear structure, which we named NELF bodies. These recent developments point to a wide range of potential functions for NELF, and, as most studies on NELF thus far had been carried out in vitro, here, we prepared a complete set of fusion protein constructs of NELF subunits and carried out a general cell biological study of the intracellular dynamics of NELF. Our data show that NELF subunits exhibit highly specific subcellular localizations, such as in NELF bodies or in midbodies, and some shuttle actively between the nucleus and cytoplasm. We further show that loss of NELF from cells can lead to enlarged and/or multiple nuclei. This work serves as a foundation and starting point for further cell biological investigations of NELF in the future.

  7. Initiation and elongation of lateral roots in Lactuca sativa

    NASA Technical Reports Server (NTRS)

    Zhang, N.; Hasenstein, K. H.

    1999-01-01

    Lactuca sativa cv. Baijianye seedlings do not normally produce lateral roots, but removal of the root tip or application of auxin, especially indole-butyric acid, triggered the formation of lateral roots. Primordia initiated within 9 h and were fully developed after 24 h by activating the pericycle cells opposite the xylem pole. The pericycle cells divided asymmetrically into short and long cells. The short cells divided further to form primordia. The effect of root tip removal and auxin application was reversed by 6-benzylaminopurine at concentrations >10(-8) M. The cytokinin oxidase inhibitor N1-(2chloro4pyridyl)-N2-phenylurea also suppressed auxin-induced lateral rooting. The elongation of primary roots was promoted by L-alpha-(2-aminoethoxyvinyl) glycine and silver ions, but only the latter enhanced elongation of lateral roots. The data indicate that the induction of lateral roots is controlled by basipetally moving cytokinin and acropetally moving auxin. Lateral roots appear to not produce ethylene.

  8. Cooperativity of peptidoglycan synthases active in bacterial cell elongation.

    PubMed

    Banzhaf, Manuel; van den Berg van Saparoea, Bart; Terrak, Mohammed; Fraipont, Claudine; Egan, Alexander; Philippe, Jules; Zapun, André; Breukink, Eefjan; Nguyen-Distèche, Martine; den Blaauwen, Tanneke; Vollmer, Waldemar

    2012-07-01

    Growth of the bacterial cell wall peptidoglycan sacculus requires the co-ordinated activities of peptidoglycan synthases, hydrolases and cell morphogenesis proteins, but the details of these interactions are largely unknown. We now show that the Escherichia coli peptidoglycan glycosyltrasferase-transpeptidase PBP1A interacts with the cell elongation-specific transpeptidase PBP2 in vitro and in the cell. Cells lacking PBP1A are thinner and initiate cell division later in the cell cycle. PBP1A localizes mainly to the cylindrical wall of the cell, supporting its role in cell elongation. Our in vitro peptidoglycan synthesis assays provide novel insights into the cooperativity of peptidoglycan synthases with different activities. PBP2 stimulates the glycosyltransferase activity of PBP1A, and PBP1A and PBP2 cooperate to attach newly synthesized peptidoglycan to sacculi. PBP2 has peptidoglycan transpeptidase activity in the presence of active PBP1A. Our data also provide a possible explanation for the depletion of lipid II precursors in penicillin-treated cells.

  9. Initiation and elongation of lateral roots in Lactuca sativa

    NASA Technical Reports Server (NTRS)

    Zhang, N.; Hasenstein, K. H.

    1999-01-01

    Lactuca sativa cv. Baijianye seedlings do not normally produce lateral roots, but removal of the root tip or application of auxin, especially indole-butyric acid, triggered the formation of lateral roots. Primordia initiated within 9 h and were fully developed after 24 h by activating the pericycle cells opposite the xylem pole. The pericycle cells divided asymmetrically into short and long cells. The short cells divided further to form primordia. The effect of root tip removal and auxin application was reversed by 6-benzylaminopurine at concentrations >10(-8) M. The cytokinin oxidase inhibitor N1-(2chloro4pyridyl)-N2-phenylurea also suppressed auxin-induced lateral rooting. The elongation of primary roots was promoted by L-alpha-(2-aminoethoxyvinyl) glycine and silver ions, but only the latter enhanced elongation of lateral roots. The data indicate that the induction of lateral roots is controlled by basipetally moving cytokinin and acropetally moving auxin. Lateral roots appear to not produce ethylene.

  10. Engineering the elongation factor Tu for efficient selenoprotein synthesis.

    PubMed

    Haruna, Ken-ichi; Alkazemi, Muhammad H; Liu, Yuchen; Söll, Dieter; Englert, Markus

    2014-09-01

    Selenocysteine (Sec) is naturally co-translationally incorporated into proteins by recoding the UGA opal codon with a specialized elongation factor (SelB in bacteria) and an RNA structural signal (SECIS element). We have recently developed a SECIS-free selenoprotein synthesis system that site-specifically--using the UAG amber codon--inserts Sec depending on the elongation factor Tu (EF-Tu). Here, we describe the engineering of EF-Tu for improved selenoprotein synthesis. A Sec-specific selection system was established by expression of human protein O(6)-alkylguanine-DNA alkyltransferase (hAGT), in which the active site cysteine codon has been replaced by the UAG amber codon. The formed hAGT selenoprotein repairs the DNA damage caused by the methylating agent N-methyl-N'-nitro-N-nitrosoguanidine, and thereby enables Escherichia coli to grow in the presence of this mutagen. An EF-Tu library was created in which codons specifying the amino acid binding pocket were randomized. Selection was carried out for enhanced Sec incorporation into hAGT; the resulting EF-Tu variants contained highly conserved amino acid changes within members of the library. The improved UTu-system with EF-Sel1 raises the efficiency of UAG-specific Sec incorporation to >90%, and also doubles the yield of selenoprotein production. © The Author(s) 2014. Published by Oxford University Press on behalf of Nucleic Acids Research.

  11. Effect of temperature on plant elongation and cell wall extensibility.

    PubMed

    Pietruszka, M; Lewicka, S

    2007-03-01

    Lockhart equation was derived for explaining plant cell expansion where both cell wall extension and water uptake must occur concomitantly. Its fundamental contribution was to express turgor pressure explicitly in terms of osmosis and wall mechanics. Here we present a new equation in which pressure is determined by temperature. It also accounts for the role of osmosis and consequently the role of water uptake in growing cell. By adopting literature data, we also attempt to report theoretically the close relation between plant elongation and cell wall extensibility. This is accomplished by the modified equation of growth solved for various temperatures in case of two different species. The results enable to interpret empirical data in terms of our model and fully confirm its applicability to the investigation of the problem of plant cell extensibility in function of environmental temperature. Moreover, by separating elastic effects from growth process we specified the characteristic temperature common for both processes which corresponds to the resonance energy of biochemical reactions as well as to the rapid softening of the elastic modes toward the high temperature end where we encountered viscoelastic and/or plastic behavior as dominating. By introducing analytical formulae connected with growth and elastic properties of the cell wall, we conclude with the statement how these both processes contribute quantitatively to the resonance-like shape of the elongation curve. In addition, the tension versus temperature "phase diagram" for a living plant cell is presented.

  12. Axial elongation following prolonged near work in myopes and emmetropes.

    PubMed

    Woodman, Emily C; Read, Scott A; Collins, Michael J; Hegarty, Katherine J; Priddle, Scott B; Smith, Josephine M; Perro, Judd V

    2011-05-01

    To investigate the influence of a period of sustained near work upon axial length in groups of emmetropes (EMM) and myopes. Forty young adult subjects (20 myopes and 20 emmetropes) were recruited for the study. Myopes were further classified as early onset (EOM), late onset (LOM), stable (SM) or progressing (PM) subgroups. Axial length was measured with the IOLMaster instrument before, immediately after and then again 10 min after a continuous 30 min near task of 5 D accommodation demand. Measures of distance objective refraction were also collected. Significant changes in axial length were observed immediately following the near task. EOM axial length elongated on average by 0.027±0.021 mm, LOM by 0.014±0.020 mm, EMM by 0.010±0.015 mm, PM by 0.031±0.022 mm and SM by 0.014±0.018 mm. At the conclusion of the 10 min regression period, axial length measures were not significantly different from baseline values. Axial elongation was observed following a prolonged near task. Both EOM and PM groups showed increases in axial length that were significantly greater than emmetropes.

  13. Strain and elongation of the human semitendinosus muscle - tendon unit.

    PubMed

    Kellis, Eleftherios; Patsika, Glykeria; Karagiannidis, Evaggelos

    2013-12-01

    The semitendinosus (ST) consists of a long distal tendon and it is divided in two parts by a tendinous inscription (TI). The purpose of this study was to quantify strain and elongation of the TI and the distal tendon of ST. Fourteen subjects performed ramp isometric contractions of the knee flexors at 0°, 45° and 90° of knee flexion. Two ultrasound probes were used to visualize the displacement of the distal tendon and selected points across the TI and aponeuroses. Three-way analysis of variance designs indicated that: (a) strain and elongation of the ST distal muscle-tendon junction were higher than that of the aponeurosis - TI junction points (p < 0.05) (b) the long arm of the TI reach strain of 49.86 ± 7.77% which was significantly (p < 0.05) higher than that displayed by the short arm (28.35 ± 0.59%) (c) Strain of tendinous and TI-aponeuroses segments significantly increased from 90° to 0° of knee flexion while the inverse was observed for the TI arm length (p < 0.05). (d) Tendon strain was significantly higher than strain of the TI-aponeuroses segments at 45° and 90° of knee flexion while the opposite was observed at 0° of knee flexion. The arrangement of TI along ST length results in differential local strains, indicating that the mechanical properties of the ST muscle are affected by tendon, aponeuroses and tendinous inscription interactions.

  14. The interplay of stiffness and force anisotropies drives embryo elongation

    PubMed Central

    Vuong-Brender, Thanh Thi Kim; Ben Amar, Martine; Pontabry, Julien; Labouesse, Michel

    2017-01-01

    The morphogenesis of tissues, like the deformation of an object, results from the interplay between their material properties and the mechanical forces exerted on them. The importance of mechanical forces in influencing cell behaviour is widely recognized, whereas the importance of tissue material properties, in particular stiffness, has received much less attention. Using Caenorhabditis elegans as a model, we examine how both aspects contribute to embryonic elongation. Measuring the opening shape of the epidermal actin cortex after laser nano-ablation, we assess the spatiotemporal changes of actomyosin-dependent force and stiffness along the antero-posterior and dorso-ventral axis. Experimental data and analytical modelling show that myosin-II-dependent force anisotropy within the lateral epidermis, and stiffness anisotropy within the fiber-reinforced dorso-ventral epidermis are critical in driving embryonic elongation. Together, our results establish a quantitative link between cortical tension, material properties and morphogenesis of an entire embryo. DOI: http://dx.doi.org/10.7554/eLife.23866.001 PMID:28181905

  15. Structural basis for transcription elongation by bacterial RNA polymerase.

    PubMed

    Vassylyev, Dmitry G; Vassylyeva, Marina N; Perederina, Anna; Tahirov, Tahir H; Artsimovitch, Irina

    2007-07-12

    The RNA polymerase elongation complex (EC) is both highly stable and processive, rapidly extending RNA chains for thousands of nucleotides. Understanding the mechanisms of elongation and its regulation requires detailed information about the structural organization of the EC. Here we report the 2.5-A resolution structure of the Thermus thermophilus EC; the structure reveals the post-translocated intermediate with the DNA template in the active site available for pairing with the substrate. DNA strand separation occurs one position downstream of the active site, implying that only one substrate at a time can specifically bind to the EC. The upstream edge of the RNA/DNA hybrid stacks on the beta'-subunit 'lid' loop, whereas the first displaced RNA base is trapped within a protein pocket, suggesting a mechanism for RNA displacement. The RNA is threaded through the RNA exit channel, where it adopts a conformation mimicking that of a single strand within a double helix, providing insight into a mechanism for hairpin-dependent pausing and termination.

  16. Elongation of primed DNA templates by eukaryotic DNA polymerases.

    PubMed Central

    Ikeda, J E; Longiaru, M; Horwitz, M S; Hurwitz, J

    1980-01-01

    The combined action of DNA polymerase alpha and DNA polymerase beta leads to the synthesis of full-length linear DNA strands with phi X174 DNA templates containing an RNA primer. The reaction can be carried out in two stages. In the first stage, DNA polymerase alpha catalyzes the synthesis of a chain that averaged 230 deoxynucleotides long and was covalently linked to the RNA primer. In the second stage, DNA polymerase beta elongates the DNA strand covalently attached to the RNA primer to full length. With DNA primers, DNA polymerase alpha catalyzes only limited deoxynucleotide addition whereas DNA polymerase beta alone elongates DNA primed templates to full length. DNA polymerase beta can also stimulate the synthesis of adenovirus DNA in vitro in the presence of a cytosol extract from adenovirus-infected cells. In all of these systems, dNMP incorporation catalyzed by DNA polymerase beta was sensitive to N-ethylmaleimide; however, this polymerase activity was resistant to N-ethylmaleimide with poly(rA) x (dT) as the primer template. Images PMID:6160581

  17. Molecular mechanism of viomycin inhibition of peptide elongation in bacteria.

    PubMed

    Holm, Mikael; Borg, Anneli; Ehrenberg, Måns; Sanyal, Suparna

    2016-01-26

    Viomycin is a tuberactinomycin antibiotic essential for treating multidrug-resistant tuberculosis. It inhibits bacterial protein synthesis by blocking elongation factor G (EF-G) catalyzed translocation of messenger RNA on the ribosome. Here we have clarified the molecular aspects of viomycin inhibition of the elongating ribosome using pre-steady-state kinetics. We found that the probability of ribosome inhibition by viomycin depends on competition between viomycin and EF-G for binding to the pretranslocation ribosome, and that stable viomycin binding requires an A-site bound tRNA. Once bound, viomycin stalls the ribosome in a pretranslocation state for a minimum of ∼ 45 s. This stalling time increases linearly with viomycin concentration. Viomycin inhibition also promotes futile cycles of GTP hydrolysis by EF-G. Finally, we have constructed a kinetic model for viomycin inhibition of EF-G catalyzed translocation, allowing for testable predictions of tuberactinomycin action in vivo and facilitating in-depth understanding of resistance development against this important class of antibiotics.

  18. Molecular mechanism of viomycin inhibition of peptide elongation in bacteria

    PubMed Central

    Holm, Mikael; Borg, Anneli; Ehrenberg, Måns; Sanyal, Suparna

    2016-01-01

    Viomycin is a tuberactinomycin antibiotic essential for treating multidrug-resistant tuberculosis. It inhibits bacterial protein synthesis by blocking elongation factor G (EF-G) catalyzed translocation of messenger RNA on the ribosome. Here we have clarified the molecular aspects of viomycin inhibition of the elongating ribosome using pre-steady-state kinetics. We found that the probability of ribosome inhibition by viomycin depends on competition between viomycin and EF-G for binding to the pretranslocation ribosome, and that stable viomycin binding requires an A-site bound tRNA. Once bound, viomycin stalls the ribosome in a pretranslocation state for a minimum of ∼45 s. This stalling time increases linearly with viomycin concentration. Viomycin inhibition also promotes futile cycles of GTP hydrolysis by EF-G. Finally, we have constructed a kinetic model for viomycin inhibition of EF-G catalyzed translocation, allowing for testable predictions of tuberactinomycin action in vivo and facilitating in-depth understanding of resistance development against this important class of antibiotics. PMID:26755601

  19. Functional relationships of leafing intensity to plant height, growth form and leaf habit

    NASA Astrophysics Data System (ADS)

    Yan, En-Rong; Milla, Rubén; Aarssen, Lonnie W.; Wang, Xi-Hua

    2012-05-01

    Leafing intensity, i.e. the number of leaves per unit of stem volume or mass, is a common developmental correlate of leaf size. However, the ecological significance and the functional implications of variation in leafing intensity, other than its relation to leaf size, are unknown. Here, we explore its relationships with plant height, growth form, leaf size, and leaf habit to test a series of corollaries derived from the leafing intensity premium hypothesis. Volume-based leafing intensities and plant heights were recorded for 109 woody species from the subtropical evergreen broadleaf forests of eastern China. In addition, we compiled leafing intensity data from published literature, and combined it with our data to form a 398 species dataset, to test for differences of leafing intensity between plant growth forms (i.e. herbaceous and woody) and leaf habits (i.e. deciduous and evergreens). Leafing intensity was negatively correlated with plant height and individual leaf mass. Volume-based leafing intensities were significantly higher in herbaceous species than in woody species, and also higher in deciduous than in evergreen woody species. In conclusion, leafing intensity relates strongly to plant height, growth form, leaf size, and leaf habit in directions generally in accordance to the leafing intensity premium hypothesis. These results can be interpreted in terms of the evolution of adaptive strategies involving response to herbivory, competitive ability for light and reproductive economy.

  20. [The in silico elongation and analysis of the EST from Schistosoma japonicum].

    PubMed

    Liu, Han-teng; Wu, Zhong-dao; Zou, Sai-de; Shao, Xiao

    2004-08-01

    To construct a platform for in silico elongation and batch analysis of Schistosoma japonicum (Sj) ESTs, acquire the potential novel genes and research the expression profile of the genes. On the basis of Linux operating system and local ESTs database of Sj, the BLAST and PHRAP softwares were used to construct a program to achieve the elongation of ESTs. Stand-alone BLAST search against the nr database helped analyze the elongated sequence. After finishing the batch analysis script, the platform was used to research the Sj gene expression profile and acquire the potential novel genes. The platform showed satisfactory efficiency and fidelity. 487 elongated sequences obtained from 552 and 307 elongated sequences showed high homology within the nr database downloaded from NCBI. Furthermore, 104 elongated sequences displayed significant homology but showed no homology before elongated. 27 potential novel genes were filtered out. An effective platform for Sj ESTs data mining was accomplished and further information on the potential novel genes was acquired.

  1. Expression of IPT in Asakura-sanshoo (Zanthoxylum piperitum (L.) DC. f. inerme Makino) Alters Tree Architecture, Delays Leaf Senescence, and Changes Leaf Essential Oil Composition.

    PubMed

    Zeng, Xiao-Fang; Zhao, De-Gang

    The IPT gene encodes isopentenyl pyrophosphate transferase, a key enzyme in cytokinin biosynthesis. We introduced IPT under the control of the CaMV35S promoter into Asakura-sanshoo (Zanthoxylum piperitum (L.) DC. f. inerme Makino) via stable Agrobacterium tumefaciens-mediated transformation. Three of 3-year-old transgenic Asakura-sanshoo lines Y5, Y16, and Y17 were used to evaluate the effects of IPT expression on the morphological characteristics, leaf senescence, and essential oil composition. Introduced IPT into Asakura-sanshoo stimulated an increase in cytokinin content and a decrease in auxin level. The increase in the cytokinin/auxin ratio affected the tree architecture in 3-year-old transgenic lines. The phenotypes of transgenic lines included reduced stem elongation, decreased leaf surface area, increased branching, and delayed leaf senescence. The expression of IPT in Asakura-sanshoo also affected the leaf essential oil composition. The amount of oxygenated sesquiterpenoid compounds in Y5 and Y16 was 21.1 and 15.8 % higher, respectively, than that in wild type (WT). The amount of aromatic compounds in Y5 and Y16 was 2.9 and 24.6 % lower, respectively, than that in WT. These results show that ipt expression in Asakura-sanshoo conferred desirable traits, including a dwarf growth habit, delayed senescence, and increased concentrations of some sesquiterpenoid compounds.

  2. The R3-MYB gene GhCPC negatively regulates cotton fiber elongation.

    PubMed

    Liu, Bingliang; Zhu, Yichao; Zhang, Tianzhen

    2015-01-01

    Cotton (Gossypium spp.) fibers are single-cell trichomes that arise from the outer epidermal layer of seed coat. Here, we isolated a R3-MYB gene GhCPC, identified by cDNA microarray analysis. The only conserved R3 motif and different expression between TM-1 and fuzzless-lintless mutants suggested that it might be a negative regulator in fiber development. Transgenic evidence showed that GhCPC overexpression not only delayed fiber initiation but also led to significant decreases in fiber length. Interestingly, Yeast two-hybrid analysis revealed an interaction complex, in which GhCPC and GhTTG1/4 separately interacted with GhMYC1. In transgenic plants, Q-PCR analysis showed that GhHOX3 (GL2) and GhRDL1 were significantly down regulated in -1-5 DPA ovules and fibers. In addition, Yeast one-hybrid analysis demonstrated that GhMYC1 could bind to the E-box cis-elements and the promoter of GhHOX3. These results suggested that GhHOX3 (GL2) might be downstream gene of the regulatory complex. Also, overexpression of GhCPC in tobacco led to differential loss of pigmentation. Taken together, the results suggested that GhCPC might negatively regulate cotton fiber initiation and early elongation by a potential CPC-MYC1-TTG1/4 complex. Although the fibers were shorter in transgenic cotton lines than in the wild type, no significant difference was detected in stem or leaf trichomes, even in cotton mutants (five naked seed or fuzzless), suggesting that fiber and trichome development might be regulated by two sets of genes sharing a similar model.

  3. [The analysis of the causes of variability of the relationship between leaf dry mass and area in plants].

    PubMed

    Vasfilov, S P

    2011-01-01

    The lamina dry mass: area ratio (LMA - Leaf Mass per Area) is a quite variable trait. Leaf dry mass consists of symplast mass (a set of all leaf protoplasts) and apoplast mass (a set of all cell walls in a leaf). The ratio between symplast and apoplast masses is positively related to any functional trait of leaf calculated per unit of dry mass. The value of this ratio is defined by cells size and their number per unit of leaf area, number of mesophyll cells layers and their differentiation between palisade and spongy ones, and also by density of cells packing. The LMA value is defined by leaf thickness and density. The extent and direction of variability in both leaf traits define the extent and direction of variability in LMA. Negative correlation between leaf thickness and density reduces the level of LMA variability. As a consequence of this correlation the following pattern emerges: the thinner a leaf, the denser it is. Changes in the traits that define the LMA value take place both within a species under the influence of environmental factors and between species that differ in leaf structure and functions. Light is the most powerful environmental factor that influences the LMA, increase in illumination leading to increase in LMA. This effect occurs during leaf growth at the expense of structural changes associated with the reduction of symplast/apoplast mass ratio. Under conditions of intense illumination, LMA may increase due to accumulation of starch. With regard to the majority of leaf functions, the mass of starch may be ascribed to apoplast. Starch accumulation in leaves is observed also under conditions of elevated CO2 concentration in the air. Under high illumination, however, LMA increases also due to increased apoplast contribution to leaf dry mass. Scarce mineral nutrition leads to LMA increase due to lowering of growth zones demands for phothosyntates and, therefore, to increase in starch content of leaves. High level of mineral nutrition during

  4. Analysis and significance of gravity-induced asymmetric growth in the grass leaf-sheath pulvinus

    NASA Technical Reports Server (NTRS)

    Dayanandan, P.; Kaufman, P. B.

    1984-01-01

    The negative gravitropic response in the grass leaf-sheath pulvinus is a consequence of cell elongation involving all cells except those of the uppermost region of the upper flank of an horizontally oriented pulvinus. The lowermost layer of cells elongate maximally, and the regions in between elongate to intermediate extents. The resulting curvatures of a responding pulvinus can be expressed mathematically by relating the angle of curvature (theta) to the original length (L0) and the maximal length of the lower surface (L1) and the diameter of the organ (D), using the equation, theta = (L1-L0)/D, where theta is in radians. The elongation response (S) of any individual cells within the pulvinus can be expressed by the equation, S = 0.5 - r cos theta, where r is the radius of the pulvinus and theta is in degrees. Microscopic measurement of cell lengths in different regions of the pulvinus supports the mathematical predictions. Indirect support is also obtained from the use of colchicine, coumarin, dichlorobenzonitrile (DCBN) and isopropyl N-chlorophenyl carbamate which exaggerate the inherent asymmetry during gravitropic response. Coumarin and DCBN also induce thickenings in the radial walls which appear first in the statenchyma, and later, in cells located towards the outer periphery of the pulvinus. The distribution patterns of these thickenings suggest that the asymmetric growth response of the pulvinus may be due to a differential and radial, centrifugal transport of growth promotors from the central statenchyma region.

  5. Analysis and significance of gravity-induced asymmetric growth in the grass leaf-sheath pulvinus.

    PubMed

    Dayanandan, P; Kaufman, P B

    1984-01-01

    The negative gravitropic response in the grass leaf-sheath pulvinus is a consequence of cell elongation involving all cells except those of the uppermost region of the upper flank of an horizontally oriented pulvinus. The lowermost layer of cells elongate maximally, and the regions in between elongate to intermediate extents. The resulting curvatures of a responding pulvinus can be expressed mathematically by relating the angle of curvature (theta) to the original length (L0) and the maximal length of the lower surface (L1) and the diameter of the organ (D), using the equation, theta = (L1-L0)/D, where theta is in radians. The elongation response (S) of any individual cells within the pulvinus can be expressed by the equation, S = 0.5 - r cos theta, where r is the radius of the pulvinus and theta is in degrees. Microscopic measurement of cell lengths in different regions of the pulvinus supports the mathematical predictions. Indirect support is also obtained from the use of colchicine, coumarin, dichlorobenzonitrile (DCBN) and isopropyl N-chlorophenyl carbamate which exaggerate the inherent asymmetry during gravitropic response. Coumarin and DCBN also induce thickenings in the radial walls which appear first in the statenchyma, and later, in cells located towards the outer periphery of the pulvinus. The distribution patterns of these thickenings suggest that the asymmetric growth response of the pulvinus may be due to a differential and radial, centrifugal transport of growth promotors from the central statenchyma region.

  6. Analysis and significance of gravity-induced asymmetric growth in the grass leaf-sheath pulvinus

    NASA Technical Reports Server (NTRS)

    Dayanandan, P.; Kaufman, P. B.

    1984-01-01

    The negative gravitropic response in the grass leaf-sheath pulvinus is a consequence of cell elongation involving all cells except those of the uppermost region of the upper flank of an horizontally oriented pulvinus. The lowermost layer of cells elongate maximally, and the regions in between elongate to intermediate extents. The resulting curvatures of a responding pulvinus can be expressed mathematically by relating the angle of curvature (theta) to the original length (L0) and the maximal length of the lower surface (L1) and the diameter of the organ (D), using the equation, theta = (L1-L0)/D, where theta is in radians. The elongation response (S) of any individual cells within the pulvinus can be expressed by the equation, S = 0.5 - r cos theta, where r is the radius of the pulvinus and theta is in degrees. Microscopic measurement of cell lengths in different regions of the pulvinus supports the mathematical predictions. Indirect support is also obtained from the use of colchicine, coumarin, dichlorobenzonitrile (DCBN) and isopropyl N-chlorophenyl carbamate which exaggerate the inherent asymmetry during gravitropic response. Coumarin and DCBN also induce thickenings in the radial walls which appear first in the statenchyma, and later, in cells located towards the outer periphery of the pulvinus. The distribution patterns of these thickenings suggest that the asymmetric growth response of the pulvinus may be due to a differential and radial, centrifugal transport of growth promotors from the central statenchyma region.

  7. The Super Elongation Complex Family of RNA Polymerase II Elongation Factors: Gene Target Specificity and Transcriptional Output

    PubMed Central

    Luo, Zhuojuan; Lin, Chengqi; Guest, Erin; Garrett, Alexander S.; Mohaghegh, Nima; Swanson, Selene; Marshall, Stacy; Florens, Laurence; Washburn, Michael P.

    2012-01-01

    The elongation stage of transcription is highly regulated in metazoans. We previously purified the AFF1- and AFF4-containing super elongation complex (SEC) as a major regulator of development and cancer pathogenesis. Here, we report the biochemical isolation of SEC-like 2 (SEC-L2) and SEC-like 3 (SEC-L3) containing AFF2 and AFF3 in association with P-TEFb, ENL/MLLT1, and AF9/MLLT3. The SEC family members demonstrate high levels of polymerase II (Pol II) C-terminal domain kinase activity; however, only SEC is required for the proper induction of the HSP70 gene upon stress. Genome-wide mRNA-Seq analyses demonstrated that SEC-L2 and SEC-L3 control the expression of different subsets of genes, while AFF4/SEC plays a more dominant role in rapid transcriptional induction in cells. MYC is one of the direct targets of AFF4/SEC, and SEC recruitment to the MYC gene regulates its expression in different cancer cells, including those in acute myeloid or lymphoid leukemia. These findings suggest that AFF4/SEC could be a potential therapeutic target for the treatment of leukemia or other cancers associated with MYC overexpression. PMID:22547686

  8. Light acclimation potential and carry-over effects vary among three evergreen tree species with contrasting patterns of leaf emergence and maturation.

    PubMed

    Ishii, Hiroaki; Ohsugi, Yoshihiro

    2011-08-01

    We compared light acclimation potential among three evergreen broadleaved species with contrasting patterns of shoot elongation, leaf emergence and leaf maturation. Understory saplings were transferred to a high-light environment before bud break, grown for 13 months, and then transferred back to the understory to observe subsequent carry-over effects. Acclimation potential was highest and sapling mortality was lowest for Cinnamomum japonicum Sieb. ex Nakai. Indeterminate growth and successive leaf emergence allowed this species to acclimate to both high and low light by adjusting leaf production as well as leaf properties. Sapling mortality occurred after both transfers for Camellia japonica L., which also has indeterminate growth and successive leaf emergence. In this species, carry-over effects were observed at the individual level, but leaf-level acclimation potential was high. Acclimation potential was lowest and sapling mortality occurred soon after the transfer to high light for Quercus glauca Thunb. ex Murray. Determinate growth and flush-type leaf emergence resulted in significant carry-over effects in this species. Indeterminate growth and successive leaf emergence increase whole-plant acclimation potential by extending the period of growth and architectural development during the growing season. Similarly, we inferred that delayed leaf maturation, observed in many evergreen species, increases the acclimation potential of current-year leaves by extending the period of leaf development. In evergreen species, the acclimation potential of preexisting leaves determines the role that leaf turnover plays in whole-plant light acclimation, resulting in diverse strategies for light acclimation among species, as observed in this study.

  9. Radiostereometric Evaluation of Tendon Elongation After Distal Biceps Repair

    PubMed Central

    Marshall, Nathan E.; Keller, Robert A.; Okoroha, Kelechi; Guest, John Michael; Yu, Charles; Muh, Stephanie; Moutzouros, Vasilios

    2016-01-01

    Background: Operative repair of distal biceps tendon ruptures has shown successful outcomes. However, little is known about the amount of tendon or repair site lengthening after repair. Purpose/Hypothesis: The purpose of this study was to evaluate distal biceps tendon repair via intratendinous radiostereometric analysis to analyze tendon lengthening at different time intervals of healing. The hypothesis was that there is significant lengthening after repair. Study Design: Case series; Level of evidence, 4. Methods: Eleven patients with distal biceps ruptures requiring operative repair were recruited. During repair, two 2-mm tantalum beads with laser-etched holes were sutured to the distal biceps tendon. Beads were evaluated via computed tomography scans immediately postoperatively and at 16 weeks. Radiographs were obtained at time 0 and then at 4, 8, and 16 weeks postoperatively. Measurements were made using the button-to-bead and bead-to-bead distances to assess repair site elongation as well as tendon elongation over time. After final follow-up, patients filled out the Disabilities of the Arm, Shoulder, and Hand (DASH) questionnaire and underwent ultrasound to confirm the integrity of the tendon. Results: Ten patients had complete ruptures, with 1 having a partial rupture that underwent completion of the tear and subsequent repair. All patients showed statistically significant lengthening after surgery. The mean amount of tendon lengthening after surgery was 22.8 mm (range, 11.2-30.9 mm; P < .05), and the repair site lengthened a mean 17.0 mm (range, 9.6-30.6 mm; P < .05) from surgery to final follow-up. The greatest change in lengthening was noted between time 0 and week 4 (mean, 11.3 mm; P < .05), with the least amount of lengthening between weeks 8 and 16 (mean, 2.6 mm; P < .05). The mean DASH score was 11.2. Final ultrasound evaluations found all tendons to be in continuity. Conclusion: All patients undergoing distal biceps tendon repair have significant

  10. Biophysical control of leaf temperature

    NASA Astrophysics Data System (ADS)

    Dong, N.; Prentice, I. C.; Wright, I. J.

    2014-12-01

    In principle sunlit leaves can maintain their temperatures within a narrower range than ambient temperatures. This is an important and long-known (but now overlooked) prediction of energy balance theory. Net radiation at leaf surface in steady state (which is reached rapidly) must be equal to the combination of sensible and latent heat exchanges with surrounding air, the former being proportional to leaf-to-air temperature difference (ΔT), the latter to the transpiration rate. We present field measurements of ΔT which confirm the existence of a 'crossover temperature' in the 25-30˚C range for species in a tropical savanna and a tropical rainforest environment. This finding is consistent with a simple representation of transpiration as a function of net radiation and temperature (Priestley-Taylor relationship) assuming an entrainment factor (ω) somewhat greater than the canonical value of 0.26. The fact that leaves in tropical forests are typically cooler than surrounding air, often already by solar noon, is consistent with a recently published comparison of MODIS day-time land-surface temperatures with air temperatures. Theory further predicts a strong dependence of leaf size (which is inversely related to leaf boundary-layer conductance, and therefore to absolute magnitude of ΔT) on moisture availability. Theoretically, leaf size should be determined by either night-time constraints (risk of frost damage to active leaves) or day-time constraints (risk of heat stress damage),with the former likely to predominate - thereby restricting the occurrence of large leaves - at high latitudes. In low latitudes, daytime maximum leaf size is predicted to increase with temperature, provided that water is plentiful. If water is restricted, however, transpiration cannot proceed at the Priestley-Taylor rate, and it quickly becomes advantageous for plants to have small leaves, which do not heat up much above the temperature of their surroundings. The difference between leaf

  11. Photodegradation of Leaf Litter in Water-Limited Ecosystems

    NASA Astrophysics Data System (ADS)

    Cory, R. M.; Powers, H.; McDowell, N.; Rahn, T.

    2008-12-01

    The longstanding view of terrestrial decomposition holds that heterotrophic respiration drives release of CO2, but recent studies, such as Austin and Vivanco (2006) have shown that in water-limited environments, photochemical decomposition of leaf litter may be equally or more effective than microbial decomposition. Although initial studies have concluded that photochemical degradation can be important in some environments, it has been difficult to quantify and the oxidative mechanisms involved remain unknown. Thus, the objectives of our study were to (1) quantify the CO2 emitted during photochemical degradation of leaf litter and (2) use the stable isotopic signatures of evolved CO2 to elucidate pathways of production. Emitted CO2 and its isotopic signature were measured using a tunable diode laser (TDL) to assess the pool of photochemically-labile plant matter (δ13C-CO2) in a given sample and to assess the source of the oxygen (δ18O-CO2). We quantified the photochemical release of CO2 and its isotopic signature from dried leaf litter of 10 tree and grass species prevalent in major biotic zones of New Mexico. The cumulative CO2 released upon exposure of 0.1-0.3 g of dried leaf litter to three hours of simulated sunlight ranged from 8-25 mg CO2-C g-1 dried litter, corresponding to 1-2% mass loss. Generally, the δ13C-CO2 was more depleted (4-7 ± 2 per mil) than the average δ13C of the respective leaf litter sample. The δ18O-CO2 evolved is approximately equal to δ18O of atmospheric O2, suggesting that the oxidation mechanism involves direct reaction with atmospheric O2.

  12. Asian Eocene monsoons as revealed by leaf architectural signatures

    NASA Astrophysics Data System (ADS)

    Spicer, Robert A.; Yang, Jian; Herman, Alexei B.; Kodrul, Tatiana; Maslova, Natalia; Spicer, Teresa E. V.; Aleksandrova, Galina; Jin, Jianhua

    2016-09-01

    The onset and development of the Asian monsoon systems is a topic that has attracted considerable research effort but proxy data limitations, coupled with a diversity of definitions and metrics characterizing monsoon phenomena, have generated much debate. Failure of geological proxies to yield metrics capable of distinguishing between rainfall seasonality induced by migrations of the Inter-tropical Convergence Zone (ITCZ) from that attributable to topographically modified seasonal pressure reversals has frustrated attempts to understand mechanisms underpinning monsoon development and dynamics. Here we circumvent the use of such single climate parameter metrics in favor of detecting directly the distinctive attributes of different monsoon regimes encoded in leaf fossils. Leaf form adapts to the prevailing climate, particularly under the extreme seasonal stresses imposed by monsoons, so it is likely that fossil leaves carry a unique signature of past monsoon regimes. Leaf form trait spectra obtained from fossils from Eocene basins in southern China were compared with those seen in modern leaves growing under known climate regimes. The fossil leaf trait spectra, including those derived from previously published fossil floras from northwestern India, were most similar to those found in vegetation exposed to the modern Indonesia-Australia Monsoon (I-AM), which is largely a product of seasonal migrations of the ITCZ. The presence of this distinctive leaf physiognomic signature suggests that although a monsoon climate existed in Eocene time across southern Asia the characteristics of the modern topographically-enhanced South Asia Monsoon had yet to develop. By the Eocene leaves in South Asia had become well adapted to an I-AM type regime across many taxa and points to the existence of a pervasive monsoon climate prior to the Eocene. No fossil trait spectra typical of exposure to the modern East Asia monsoon were seen, suggesting the effects of this system in southern

  13. Arabidopsis COP1 and SPA Genes Are Essential for Plant Elongation But Not for Acceleration of Flowering Time in Response to a Low Red Light to Far-Red Light Ratio1[W

    PubMed Central

    Rolauffs, Sebastian; Fackendahl, Petra; Sahm, Jan; Fiene, Gabriele; Hoecker, Ute

    2012-01-01

    Plants sense vegetative shade as a reduction in the ratio of red light to far-red light (R:FR). Arabidopsis (Arabidopsis thaliana) responds to a reduced R:FR with increased elongation of the hypocotyl and the leaf petioles as well as with an acceleration of flowering time. The repressor of light signaling, CONSTITUTIVELY PHOTOMORPHOGENIC1 (COP1), has been shown previously to be essential for the shade-avoidance response in seedlings. Here, we have investigated the roles of COP1 and the COP1-interacting SUPPRESSOR OF PHYA-105 (SPA) proteins in seedling and adult facets of the shade-avoidance response. We show that COP1 and the four SPA genes are essential for hypocotyl and leaf petiole elongation in response to low R:FR, in a fashion that involves the COP1/SPA ubiquitination target LONG HYPOCOTYL IN FR LIGHT1 but not ELONGATED HYPOCOTYL5. In contrast, the acceleration of flowering in response to a low R:FR was normal in cop1 and spa mutants, thus demonstrating that the COP1/SPA complex is only required for elongation responses to vegetative shade and not for shade-induced early flowering. We further show that spa mutant seedlings fail to exhibit an increase in the transcript levels of the auxin biosynthesis genes YUCCA2 (YUC2), YUC8, and YUC9 in response to low R:FR, suggesting that an increase in auxin biosynthesis in vegetative shade requires SPA function. Consistent with this finding, expression of the auxin-response marker gene DR5::GUS did not increase in spa mutant seedlings exposed to low R:FR. We propose that COP1/SPA activity, via LONG HYPOCOTYL IN FR LIGHT1, is required for shade-induced modulation of the auxin biosynthesis pathway and thereby enhances cell elongation in low R:FR. PMID:23093358

  14. Arabidopsis COP1 and SPA genes are essential for plant elongation but not for acceleration of flowering time in response to a low red light to far-red light ratio.

    PubMed

    Rolauffs, Sebastian; Fackendahl, Petra; Sahm, Jan; Fiene, Gabriele; Hoecker, Ute

    2012-12-01

    Plants sense vegetative shade as a reduction in the ratio of red light to far-red light (R:FR). Arabidopsis (Arabidopsis thaliana) responds to a reduced R:FR with increased elongation of the hypocotyl and the leaf petioles as well as with an acceleration of flowering time. The repressor of light signaling, CONSTITUTIVELY PHOTOMORPHOGENIC1 (COP1), has been shown previously to be essential for the shade-avoidance response in seedlings. Here, we have investigated the roles of COP1 and the COP1-interacting SUPPRESSOR OF PHYA-105 (SPA) proteins in seedling and adult facets of the shade-avoidance response. We show that COP1 and the four SPA genes are essential for hypocotyl and leaf petiole elongation in response to low R:FR, in a fashion that involves the COP1/SPA ubiquitination target LONG HYPOCOTYL IN FR LIGHT1 but not ELONGATED HYPOCOTYL5. In contrast