Academic literature on the topic 'Plant stem cells'
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Journal articles on the topic "Plant stem cells"
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Voronina, A. S., and E. S. Pshennikova. "Plant Stem Cells." Molecular Biology 54, no. 2 (March 2020): 163–77. http://dx.doi.org/10.1134/s002689332002017x.
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Greb, Thomas, and Jan U. Lohmann. "Plant Stem Cells." Current Biology 26, no. 17 (September 2016): R816—R821. http://dx.doi.org/10.1016/j.cub.2016.07.070.
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Perez-Garcia, Pablo, and Miguel A. Moreno-Risueno. "Stem cells and plant regeneration." Developmental Biology 442, no. 1 (October 2018): 3–12. http://dx.doi.org/10.1016/j.ydbio.2018.06.021.
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Sang, Ya Lin, Zhi Juan Cheng, and Xian Sheng Zhang. "Plant stem cells andde novoorganogenesis." New Phytologist 218, no. 4 (March 25, 2018): 1334–39. http://dx.doi.org/10.1111/nph.15106.
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Dodueva, I. E., V. E. Tvorogova, M. Azarakhsh, M. A. Lebedeva, and L. A. Lutova. "Plant stem cells: unity and diversity." Vavilov Journal of Genetics and Breeding 20, no. 4 (January 1, 2016): 441–58. http://dx.doi.org/10.18699/vj16.172.
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Dodueva, I. E., V. E. Tvorogova, M. Azarakhsh, M. A. Lebedeva, and L. A. Lutova. "Plant stem cells: Unity and diversity." Russian Journal of Genetics: Applied Research 7, no. 4 (June 2017): 385–403. http://dx.doi.org/10.1134/s2079059717040025.
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Scheres, Ben. "Stem Cells: A Plant Biology Perspective." Cell 122, no. 4 (August 2005): 499–504. http://dx.doi.org/10.1016/j.cell.2005.08.006.
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Wu, Haijun, Xiaoya Qu, Zhicheng Dong, Linjie Luo, Chen Shao, Joachim Forner, Jan U. Lohmann, et al. "WUSCHEL triggers innate antiviral immunity in plant stem cells." Science 370, no. 6513 (October 8, 2020): 227–31. http://dx.doi.org/10.1126/science.abb7360.
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Stem cells in plants constantly supply daughter cells to form new organs and are expected to safeguard the integrity of the cells from biological invasion. Here, we show how stem cells of the Arabidopsis shoot apical meristem and their nascent daughter cells suppress infection by cucumber mosaic virus (CMV). The stem cell regulator WUSCHEL responds to CMV infection and represses virus accumulation in the meristem central and peripheral zones. WUSCHEL inhibits viral protein synthesis by repressing the expression of plant S-adenosyl-l-methionine–dependent methyltransferases, which are involved in ribosomal RNA processing and ribosome stability. Our results reveal a conserved strategy in plants to protect stem cells against viral intrusion and provide a molecular basis for WUSCHEL-mediated broad-spectrum innate antiviral immunity in plants.
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G, Subramanyam, Himakar Reddy K, and Mahaboob V. Shaik. "Mobilization of Stem Cells Using Plant Extracts." Stem Cell & Regenerative Medicine 2, no. 2 (December 30, 2018): 1–4. http://dx.doi.org/10.33425/2639-9512.1030.
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Singh, Mohan B., and Prem L. Bhalla. "Plant stem cells carve their own niche." Trends in Plant Science 11, no. 5 (May 2006): 241–46. http://dx.doi.org/10.1016/j.tplants.2006.03.004.
Full textDissertations / Theses on the topic "Plant stem cells"
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Haleux, Pauline. "DNA damage responses in plant stem cells." Thesis, University of East Anglia, 2014. https://ueaeprints.uea.ac.uk/52055/.
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Plants are sessile organisms that cannot escape environmental hazards, which induce DNA damage and cause mutations. Plants are also subject to DNA damage caused by endogenous processes such as transposon movement. Plant stem cell populations in particular must be protected from genotoxicity, as they are the origin of all organs, together with the germline. In accordance with this premise, plant stem cells were found to be hypersensitive to Double Strand Breaks (DSBs), leading to their specific killing via the ATAXIA TELANGIECTASIA MUTATED (ATM) and SUPPRESSOR OF GAMMA RESPONSE 1 (SOG1) genes. However, the components of the pathway leading to programmed cell death (PCD) in response to DSBs in plant stem cells are still unknown, and the in vivo DNA damaging agents relevant to this mechanism have not been characterised, providing the starting point of this thesis. Here, a candidate gene approach and a forward genetics screen in the root stem cells did not yield new factors of the pathway leading to PCD in root stem cells. However, a specific ecotype showed an absence of DSBs-induced PCD, revealing natural variation in stem cell responses to DSBs. In relation to responses to endogenous DNA damage in plant stem cells, I identified several chromatin‐silencing mutants showing spontaneous PCD in the root meristem, and studied the link between transposon silencing and the ATM/SOG1 pathway. Finally, by characterising responses to Cre‐catalysed recombination in the shoot meristem, I uncovered an unexpected link between the DNA damage response pathway and chromatin silencing, This silencing was dependent on ATM/SOG1, linked to the production of 24-nt siRNA, and required the RNA polymerase IV and ARGONAUTE 6. My work links DNA damage responses to chromatin silencing in Arabidopsis stem cells.
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Bosch, Nadja. "Brassinosteroid regulation of plant stem cells: the bravo pathway." Doctoral thesis, Universitat Autònoma de Barcelona, 2021. http://hdl.handle.net/10803/671664.
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La present tesi doctoral descriu la configuració del complex proteic de BRAVO en el nínxol de cèl·lules mare d'Arabidopsis. També demostra que BRAVO-WOX5-BES1 formen part d'una xarxa organitzadora que comprèn heterodímeros de BRAVO-WOX5, i que junts mantenen la quiescencia en els nínxols de cèl·lules mare de l'arrel. I tot això està controlat pels BRs. Aquestes dades proporcionen nous coneixements sobre l'organització de la divisió del centre quiescente en les arrels vegetals. Es va investigar la composició del complex proteic BRAVO de l'arrel primària d'Arabidopsis in vivo mitjançant tècniques de InmunoPrecipitación i cromatografia líquida/masses. Però a causa de la baixa expressió nativa de BRAVO, ens vam veure obligats a realitzar un examen exhaustiu dels possibles interactores de BRAVO en llevat, per a aconseguir augmentar la sensibilitat del nostre enfocament. Les anàlisis van revelar que BRAVO, un membre de la família R2R3 MYB, interactua amb una proteïna de la superfamília homeobox.
Aquest treball demostra que BRAVO, a més d'interaccionar amb WOX5, també ho fa amb BES1 i TPL. El resultat va ser confirmat mitjançant tècniques moleculars in vitro per assajos de Y2H i també in vivo utilitzant FRET-FLIM i BiFC en fulles de Nicotiana benthamiana. Les nostres dades proporcionen evidències d'interacció directa de BRAVO amb WOX5, i al mateix temps, proposem que tots dos podrien formar part del complex transcripcional BES1/TPL en el SCN, i tot això regulat mitjançant BRs. Vam mostrar que la interacció de BES1-TPL és essencial per a la divisió del QC en el nínxol de cèl·lules mare de l'arrel. L'augment dels nivells de BR indueix la divisió del QC mitjançant un mecanisme controlat amb precisió per BRAVO. Els resultats estableixen que TPL regula la divisió de cèl·lules del QC a través de la supressió mediada per BES1 de BRAVO, i en resposta als BRs. A més, mitjançant una anàlisi genètic i matemàtic revelem que la interacció de BRAVO i WOX5 és essencial per a determinar el destí de les cèl·lules mare. De particular interès és el fet que BRAVO i WOX5 es reforcen mútuament en el nínxol de cèl·lules mare d'arrel. Això és sorprenent, ja que els nivells de WOX5 estan regulats per BRs de manera oposada que ho són en BRAVO. Un anàlisi exhaustiu del patró d'expressió de tots dos gens en els mutants KO simples i dobles, secunda que BRAVO és necessari per a mantenir els nivells normals de WOX5 en el QC. A més, les nostres dades són coherents amb el fet que WOX5 pot induir l'expressió de BRAVO, però només en el seu domini natiu. D'acord amb la nostra hipòtesi, el nostre model matemàtic prediu que WOX5 es reprimeix transcripcionalmente i al mateix temps activa l'expressió de BRAVO, tenint en compte la formació de heterodímeros i del complex. En aquest escenari, les interaccions del model indiquen que BRAVO no pot activar l'expressió WOX5 fora del seu domini, d'acord amb els resultats. Vam mostrar una xarxa reguladora de les nostres interaccions predita pel model matemàtic. A més, en augmentar la concentració de BR observem una major correlació entre les concentracions de proteïnes BRAVO i WOX5 quan un d'ells està absent, però no quan falten tots dos. Aquest mecanisme podria ser un mecanisme de compensació. I finalment, en l'últim capítol, aprofundim en l'evolució de BRAVO i de WOX5 amb l'objectiu de comprendre l'organització primitiva i la funció del nostre SCN actual en l'arrel.La presente tesis doctoral describe la configuración del complejo proteico de BRAVO en el nicho de células madre de Arabidopsis. También demuestra que BRAVO-WOX5-BES1 forman parte de una red organizadora que comprende heterodímeros de BRAVO-WOX5, y que juntos mantienen la quiescencia en los nichos de células madre de la raíz. Y todo esto está controlado por los BRs. Estos datos proporcionan nuevos conocimientos sobre la organización de la división del centro quiescente en las raíces vegetales. Se investigó la composición del complejo proteico BRAVO de la raíz primaria de Arabidopsis in vivo mediante técnicas de Inmuno-precipitación y cromatografía líquida/masas. Pero debido a la baja expresión nativa de BRAVO, nos vimos obligados a realizar un examen exhaustivo de los posibles interactores de BRAVO en levadura, para conseguir aumentar la sensibilidad de nuestro enfoque. Los análisis revelaron que BRAVO, un miembro de la familia R2R3 MYB, interactúa con una proteína de la superfamilia homeobox. Este trabajo demuestra que BRAVO, además de interaccionar con WOX5, también lo hace con BES1 y TPL. El resultado fue confirmado mediante técnicas moleculares in vitro por ensayos de Y2H y también in vivo utilizando FRET-FLIM y BiFC en hojas de Nicotiana benthamiana. Nuestros datos proporcionan evidencias de interacción directa de BRAVO con WOX5, y al mismo tiempo, proponemos que ambos podrían formar parte del complejo transcripcional BES1/TPL en el SCN, y todo esto regulado mediante BRs. Mostramos que la interacción de BES1-TPL es esencial para la división del QC en el nicho de células madre de la raíz. El aumento de los niveles de BR induce la división del QC mediante un mecanismo controlado con precisión por BRAVO. Los resultados establecen que TPL regula la división de células del QC a través de la supresión mediada por BES1 de BRAVO, y en respuesta a los BRs. Además, mediante un análisis genético y matemático revelamos que la interacción de BRAVO y WOX5 es esencial para determinar el destino de las células madre. De particular interés es el hecho de que BRAVO y WOX5 se refuerzan mutuamente en el nicho de células madre de raíz. Esto es sorprendente, ya que los niveles de WOX5 están regulados por BRs de forma opuesta que lo son en BRAVO. Un análisis exhaustivo del patrón de expresión de ambos genes en los mutantes KO simples y dobles, apoya que BRAVO es necesario para mantener los niveles normales de WOX5 en el QC. Además, nuestros datos son coherentes con el hecho de que WOX5 puede inducir la expresión de BRAVO, pero sólo en su dominio nativo. De acuerdo con nuestra hipótesis, nuestro modelo matemático predice que WOX5 se reprime transcripcionalmente y a su vez activa la expresión BRAVO, teniendo en cuenta la formación de heterodímeros y del complejo. En este escenario, las interacciones del modelo indican que BRAVO no puede activar la expresión WOX5 fuera de su dominio, de acuerdo con los resultados. Mostramos una red reguladora de nuestras interacciones predicha por el modelo matemático. Además, al aumentar la concentración de BR observamos una mayor correlación entre las concentraciones de proteínas BRAVO y WOX5 cuando uno de ellos está ausente. Pero no cuando faltan ambos. Este mecanismo podría ser un mecanismo de compensación. Y finalmente, en el último capítulo, profundizamos en la evolución de BRAVO y de WOX5 con el objetivo de comprender la organización primitiva y la función de nuestro SCN actual en la raíz.
The present PhD thesis dissertation describes the configuration of BRAVO protein complex in Arabidopsis stem cell niche, while demonstrates that BRAVO-WOX5-BES1 are part of a main regulator network that comprises BRAVO-WOX5 heterodimers, and together contribute to cell specific regulation of BR-controlled quiescence in root stem cell niches. The current data provide new insights into the QC division organization in plant roots. It was investigated the composition of BRAVO protein complex from Arabidopsis primary root in vivo by IP and LC-MS/MS techniques. Giving the low expression of native BRAVO, we conducted an exhaustive screening for BRAVO interactors in Yeast to increase the sensitivity of our approach. The analyses revealed that BRAVO, a member of the R2R3 MYB family, interact with a homeobox superfamily protein. The work further demonstrate that BRAVO interacts with WOX5, BES1 and TPL. This result was confirmed by molecular techniques in vitro by Y2H assays and in vivo using FRET-FLIM and BiFC in Nicotiana benthamiana leaves. Our data provides evidences of BRAVO directly interaction with WOX5, and at the same time both could be part of the BES1/TPL transcriptional complex at the SCN trough the BR signalling cascade. We display that the interaction of BES1-TPL is essential for the QC division in root SCN. Increasing BR levels induce QC division through a fine mechanism which is accurately controlled by BRAVO. The results establish that TPL regulates QC cell division through BES1-mediated suppression of BRAVO, and in response to BRs, the last step seems to be the promotion of the QC division. By a genetical and a mathematical analysis, we revealed that BRAVO and WOX5 interaction is essential for stem cell fate. Of particular interest is the fact that BRAVO and WOX5 reinforce each other at the root stem cell niche. This was surprising, since WOX5 levels are oppositely regulated by BRs than in BRAVO. The exhaustive analysis of the expression pattern of both genes in all the simple and double KO mutants, support that BRAVO is required to maintain normal WOX5 levels in the QC. In addition our data are coherent with the fact that WOX5 can induce BRAVO expression but only in the BRAVO native domain. Consistent with our hypothesis, a mathematical model predicted that WOX5 transcriptionally represses itself and activates BRAVO expression, taking in account the heterodimers and complex formation. In this scenario, the model interactions indicate that BRAVO is unable to activate WOX5 expression outside of its domain, in agreement with the results of the BRAVO overexpression line. We show a regulatory network of our interactions predicted by the mathematical model. We added the protein fold changes predicted by this model when changing the BR concentrations due to the BR signalling cascade in different situations and we observed better correlation of BRAVO and WOX5 protein concentrations when one of them are absent. But not when both are out. The exact reasons for these differences are not clear. This mechanism could be a compensation mechanism. And finally, in the last chapter, we delve into evolution with the aim to comprehend the primitive organisation and function of our present root SCN.
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Murison, Alexander James. "Regulatory networks in plant stem cells : an integrated bioinformatic and developmental biology analysis." Thesis, Cardiff University, 2014. http://orca.cf.ac.uk/57320/.
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SHOOT MERISTEMLESS (STM) encodes a transcription factor in Arabidopsis essential for ensuring correct stem cell fate. STM is known to impinge on a number of key regulatory processes such as cytokinin synthesis and the cell cycle, and interacts with other core regulatory genes such as CUP-SHAPED COTYLEDON1 (CUC1). In this study inducible STM over-expression and RNAi-mediated downregulation over a time course experiment have been used to identify the genes which form STM's gene regulatory network (GRN). These results reveal for the first time how STM over-expression and knockout phenotypes are mediated and identified the temporal order of transcriptomic changes following STM over-expression. A Bayesian network approach further refined the GRN - identifying conditional dependencies among regulated TFs and core signalling components from an independent dataset (>2,000 experiments). Predictions of direct targets from the network have been tested, demonstrating a high degree of accuracy. Interplay between STM and CUC1 is a biologically interesting sub-module of the STM GRN, with unusual dynamics. Via gene expression and microscopy experiments it has been shown that STM positively regulates the CUC1-targetting microRNA miR164c. Mathematical modelling approaches show that this is consistent with a model in which the boundary is the site of highest STM mRNA production via CUC1, and STM movement with miR164c upregulation produces the observed spatial distributions of both proteins. These relationships recast the boundary zone as a particularly dynamic region of the shoot apical meristem (SAM) and significantly develop our understanding of STM developmental context.
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Greenhowe, Jennifer. "Stem and progenitor cells in wound healing." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:87a9a7a1-b595-458a-913f-64497174f988.
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As more patients with large body surface area burns are surviving and requiring reconstructive surgery, there is a necessity for advances in the provision of bioengineered alternatives to autologous skin cover. The aims of this Thesis are to identify feasible source tissues of Endothelial Colony Forming Cells and Mesenchymal Stem/Stromal Cells for microvascular network formation in vitro with three-dimensional dermal substitute scaffolds. The working hypothesis is that pre-vascularised dermal scaffolds will result in better quality scarring when used with split thickness skin grafts. Human umbilical cord blood, peripheral blood and adipose tissue were collected and processed with ethical approval and informed consent. Samples were cultured to form endothelial outgrowth colonies and confluent Mesenchymal Stem/Stromal Cells, which were characterised using flow cytometry and expanded in vitro. Mesenchymal Stem/Stromal Cell multipotency was confirmed with tri-lineage mesenchymal differentiation. Primary cells were tested in a two-dimensional tubule formation co-culture assay and differences assessed using a proangiogenic antibody array. Tubule formation was tested in four different acellular dermal substitute scaffolds; Integra® Dermal Regeneration Template, Matriderm®, Neuskin-F® and De-cellularised Human Cadaveric Dermis. Umbilical cord blood was the most reliable source of Endothelial Colony Forming Cells, the yield of which could be predicted from placental weight. Microvasculature dissected free from adipose tissue was a reliable source of Mesenchymal Stem/Stromal Cells which supported significantly more tubule formation than Mesenchymal Stem/Stromal Cells from whole adipose tissue. Microvasculature Mesenchymal Stem/Stromal Cells secreted significantly higher levels of the proangiogenic hormone leptin, and addition of exogenous leptin to the tubule formation assay resulted in significantly increased tubule formation. Microvasculature was cultured in all four of the scaffolds tested, but depth of penetration was limited to 100µm. The artificial oxygen carrier perfluorocarbon was shown to increase two-dimensional tubule formation and may be useful in further three-dimensional scaffolds studies to improve microvascular penetration.
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Abraham, Samuel D. M. "Activation of multiple hemopoietic growth factor genes in Abelson virus transformed myeloid cells." Thesis, University of British Columbia, 1988. http://hdl.handle.net/2429/27786.
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The stringent requirement for hemopoietic growth factors (HGF) in the induction of hemopoiesis in vitro has raised questions as to their possible role(s) in leukemogenesis. Several recent clinical studies have shown aberrant cell growth factor gene activation in patient derived leukemic cells. Assessment of growth factor activity is often based on in vitro bioactivity assays of conditioned media or body fluids. The specificity of this type of endpoint is, however, open to question due to the overlap in biological activities of many HGFs.
In assessing the role of growth factor gene expression in a murine myeloid leukemia model I have used a sensitive RNA detection procedure coupled with a vector-probe system that enables the synthesis of uniformly labelled radioactive DNA probes to detect unambiguously the expression of particular growth factor genes. The Abelson murine leukemia virus (A-MuLV) derived myeloid transformants used in this study had previously been shown to produce a multi-lineage colony stimulating activity (CSA). While these A-MuLV transformants were shown to produce GM-CSF, it seemed likely that the multi-lineage CSA was due to another factor. In addition to confirming the expression of GM-CSF mRNA, I was able to show that the cells of all four A-MuLV transformed lines tested also expressed interleukin-3 mRNA. This finding was strongly corroborated by bio-activity data obtained using the CM from the A-MuLV myeloid transformants. Additional preliminary analysis by bioactivity assays have also shown the possible presence of interleukin-6 (IL-6) and a recently described pre-B cell factor suggesting perhaps a common mechanism underlying the activation of these various growth factor genes.Medicine, Faculty of
Medical Genetics, Department of
Graduate
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Betegón, Putze Isabel. "Spatiotemporal analysis of brassinosteroid signaling in the vascular stem cells." Doctoral thesis, Universitat Autònoma de Barcelona, 2021. http://hdl.handle.net/10803/671933.
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Aquesta tesi doctoral descriu diversos avenços conceptuals per a la comprensió molecular de la senyalització de brassinosteroides en el nínxol de cèl·lules mare de l’arrel d’Arabidopsis thaliana.
Els brassinoesteroides són les hormones esteroides de les plantes que juguen un paper important en el creixement i desenvolupament vegetal. En l’arrel primària d’Arabidopsis, els brassinoesteroides estan involucrats en el desenvolupament del meristem i manteniment de les cèl·lules mare. Les cèl·lules mare són les cèl·lules més indiferenciades, aquestes es van dividint i diferenciant per generar els diferents tipus cel·lulars de l’arrel. Aquests processos estan estretament controlats per factors interns i externs. El baix nombre de cada població de cèl·lules mare fa complicat el seu estudi de manera individual, per tant, el desenvolupament de mètodes amb resolució per estudiar tipus cel·lulars i fins i tot cèl·lules individuals representa una oportunitat única per investigar aquesta població cel·lular tan escassa. En aquesta tesi doctoral, utilitzem una estratègia multidisciplinària, que inclou genètica, anàlisi transcriptòmica i models matemàtics, per identificar les característiques moleculars de les cèl·lules mare de l’arrel enfocant-nos en el paper dels brassinoesteroides en aquestes cèl·lules.
Defectes en els processos de creixement i desenvolupament vegetal generalment són deguts a defectes en el creixement de l’arrel principal. Com que la quantificació precisa de la longitud de l’arrel requereix molt de temps, en aquesta tesi doctoral es descriu el desenvolupament de l’eina MyROOT per a la mesura d’arrels d’Arabidopsis d’una manera semiautomàtica (Capítol 2). A més a més, els resultats presentats en aquesta tesi revelen quin és el paper dels brassinoesteroides en el nínxol de cèl·lules mare. Mitjançant una estratègia de biologia de sistemes s’ha estudiat el paper del factor de transcripció BRAVO, regulat per brassinoesteroides, juntament amb WOX5 en el creixement i desenvolupament de l’arrel (Capítol 3). Igualment, una aproximació específica per tipus cel·lulars ha revelat la resposta transcripcional mediada per BRAVO al centre quiescent i en les cèl·lules mare vasculars adjacents (Capítol 4). Finalment, l’ús de seqüenciació massiva de l’RNA (RNAseq) amb resolució cel·lular ha estat implementat per generar el primer atles transcriptòmic del nínxol de cèl·lules mare de l’arrel. Aquesta aproximació ha permès identificar les característiques moleculars de les cèl·lules mare i la presència de diferents poblacions d’aquestes en el domini d’expressió de BRAVO (Capítol 5).
Aquesta tesi doctoral avança en el coneixement de les cèl·lules mare de les plantes i posa de manifest la necessitat d’estratègies multidisciplinàries per descobrir processos fonamentals de el desenvolupament vegetal.Esta tesis doctoral reporta avances conceptuales en la respuesta molecular mediada por la ruta de señalización de los brasinoesteroides en el nicho de células madre de Arabidopsis thaliana. Los brasinoesteroides son las hormonas esteroideas de las plantas y juegan un papel importante en el crecimiento y desarrollo vegetal. En la raíz primaria de Arabidopsis, los brasinoesteroides están involucrados en el desarrollo del meristemo y mantenimiento de las células madre. En el nicho de células madre, las células madre son las células más indiferenciadas que se van dividiendo y diferenciando para generar los distintos tipos celulares de la raíz. Estos procesos están estrechamente controlados por factores internos y externos. El bajo número de cada población de células madre hace complicado su estudio individualmente, por lo tanto, el desarrollo de métodos con resolución para estudiar tipos celulares e incluso células individualmente representa una oportunidad única para investigar esta población celular tan escasa. En esta tesis doctoral, utilizamos una estrategia multidisciplinar, que incluye genética, análisis transcriptómicos y modelos matemáticos, para identificar las características moleculares de las células madre de la raíz y enfocándonos al papel de los brasinoesteroides en esas células. Defectos en procesos de crecimiento y desarrollo vegetal se reflejan generalmente en defectos en el crecimiento de la raíz principal. Como la cuantificación precisa de la longitud de la raíz requiere mucho tiempo, en esta tesis doctoral se describe el desarrollo de la herramienta MyROOT para la medida de raíces de Arabidopsis de una forma semiautomática (Capítulo 2). Además, los resultados presentados en esta tesis revelan el papel de los brasinoesteroides en el nicho de células madre. Una estrategia de biología de sistemas revela el papel del factor de transcripción BRAVO, regulado por brasinoesteroides, junto con WOX5 en el crecimiento y desarrollo de la raíz (Capítulo 3). Igualmente, una aproximación específica para tipos celulares revela la respuesta transcripcional mediada por BRAVO en el centro quiescente y en las células madre vasculares adyacentes (Capítulo 4). Por último, el uso de RNAseqs con resolución celular ha sido implementado para generar el que creemos es el primer atlas transcriptómico del nicho de células madre de la raíz. Esta aproximación ha permitido identificar las características moleculares de las células madre y la presencia de diferentes poblaciones de estas células en el dominio de expresión de BRAVO (Capítulo 5). Esta tesis doctoral avanza en el conocimiento de las células madre de las plantas y pone de manifiesto la necesidad de estrategias multidisciplinares para descubrir procesos fundamentales del desarrollo vegetal.
This PhD thesis dissertation reports a number conceptual advances for the molecular understanding of brassinosteroid signaling in the root stem cell niche of Arabidopsis thaliana. Brassisnosteroids are the plant steroid hormones that play important roles in plant growth and development. In the Arabidopsis primary root, brassinosteroids are involved in meristem development and stem cell maintenance. At the root stem cell niche, stem cells are the more undifferentiated cells that divide and differentiate to give rise to the distinct cell types of the root. These processes are tightly controlled by internal and external factors. The low number each stem cell population makes it difficult to study them individually, therefore, the advent of cell-type and single-cell specific approaches represents a unique opportunity to investigate this rare cell population. In this PhD thesis, we used an interdisciplinary approach, including genetics, transcriptomics analysis and mathematical modelling, to identify the molecular signatures of the root stem cells with a focus on the role of brassinosteroid hormones in those cells. Defects in growth and development processes is often reflected in abnormal primary root growth. As the accurate quantification of plant primary root length is time consuming, in this PhD dissertation, we describe the development of MyROOT software for the semi-automatic measurement of Arabidopsis primary roots (Chapter 2). In addition, the results presented in this thesis uncover the role of brassinosteroids in the stem cell niche. A systems biology approach revealed a role of the brassinosteroid-mediated BRAVO transcription factor together with WOX5 in overall root growth and development (Chapter 3). Moreover, cell-type specific transcriptomic analysis uncover the transcriptional response mediated by BRAVO in the QC and adjacent vascular stem cells (Chapter 4). Finally, the use of single-cell RNAseq has been implemented to generate to our knowledge the first transcriptomic atlas of the root stem cell niche. This approach allowed to characterize the molecular signatures of the stem cells and to find novel stem cell populations within the BRAVO expression domain (Chapter 5). Overall, the present PhD thesis advances in the understanding of stem cells in plants and expose the necessity of multidisciplinary approaches to uncover fundamental biological questions in plant development.
Universitat Autònoma de Barcelona. Programa de Doctorat en Biologia i Biotecnologia Vegetal
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Mandegar, Mohammad Ali. "Analysis of artificial chromosomes in human embryonic stem cells." Thesis, University of Oxford, 2011. http://ora.ox.ac.uk/objects/uuid:81d118c3-dd01-40e4-9fea-2c335d9f3101.
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The development of safe and efficient gene delivery systems in pluripotent human embryonic stem cells (hESc) is essential to realising their full potential for basic and clinical research. The purpose of this study was to develop an efficient, non-integrating gene expression system in pluripotent hESc using human artificial chromosomes (HAC). Similar to endogenous chromosomes, HAC are capable of gene expression, replication and segregation during cell division. Unlike retroviral-mediated gene delivery vectors, HAC do not integrate into the host genome and can encompass large genomic regions for the delivery of multiple genes. Despite the advantages HAC offer, their use has been limited due to laborious cloning procedures and poor transfection efficiencies, and thus only studied in immortalised and tumour-derived human cell lines. In this study, the high transduction efficiency of herpes simplex virus type-1 (HSV-1) amplicons was utilised to overcome the described difficulties and delivered HAC vectors into pluripotent hESc. Analysis of stable hESc clones showed that de novo gene-expressing HAC were present at high frequencies ranging from 10-70% of metaphases analysed, without integrating into the genome. The established HAC contained an active centromere, and were stably maintained without integration or loss in the absence of selection for 90 days. Stable HAC-containing hESc clones retained their pluripotency as demonstrated by neuronal differentiation, in vitro germ layer and teratoma formation assays. HAC gene expression persisted, with some variation, post-differentiation in the various deriving cell types. This is the first report of successful de novo HAC formation in hESc for gene expression studies. These findings show potential for delivering high-capacity genomic constructs safely and efficiently into pluripotent cells for the purpose of genetic manipulation and ultimately patient-specific somatic gene therapy.
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Guo, Yanping. "The mechanism of Nov (CCN3) function in haematopoiesis." Thesis, University of Oxford, 2012. http://ora.ox.ac.uk/objects/uuid:5785f3b9-3206-4bb4-b486-d90cded680f8.
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Haematopoietic stem cells (HSC) are strictly regulated by intrinsic regulators and extrinsic signals from the microenvironment. Nov (CCN3), a matricellular protein of the CCN family, has been reported as a suppressor gene in solid tumours and chronic myeloid leukaemia (CML). Recent study identified Nov as a positive regulator in human cord blood CD34+ stem cells. However, the functions of Nov in haematopoiesis and adult HSC remain largely unknown.
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Buglass, Surahanil Katrin. "Regulating stem cell fate within microenvironmental niches." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:75f9498c-30f0-4983-84b2-dd58f2ccf52b.
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Improving the repopulation potential of human umbilical cord blood (UCB) haemopoietic stem cells (HSCs) remains a paramount goal in HSC transplantation (HSCT) therapy. This implies enhancing the homing and engraftment potential of UCB-CD34+CD133+ cells to the bone marrow (BM). Although an array of molecules continues to be identified as ‘key’ homing molecules, the molecular mechanisms controlling HSC homing are still not fully understood. The regulatory implications of hypoxia in the BM, with the concomitant stabilisation of hypoxia inducible transcription factor-1α (HIF-1α), are becoming more apparent, yet at the commencement of this thesis no study had explored whether hypoxia induced signalling can be adopted to regulate the homing and engraftment of transplanted HSCs. The aim of this DPhil project was thus to investigate whether hypoxic conditions as detected in the BM influence the adhesion of UBC-CD133+ cells to osteoblasts, BM stromal cells and BM endothelial cells-60 (BMEC-60), as well as their transmigration towards chemokine SDF-1α across BMEC-60. Increasing the exposure of UCB-CD133+ cells to 1.5% O2 doubled the percentage of transmigrating cells (p<0.05), and while hypoxia stimulated UCB-CD133+ cells preferentially adhered to IL-1β stimulated BMEC-60, their adhesion to non-stimulated (BMEC-60) was significantly improved (p<0.001). To help unravel the underlying molecular mechanisms, we attempted to examine the potential involvement of hypoxia regulated scaffolding protein HEF-1/NEDD9/Cas-L (HEF-1) in the increased percentage of migrating UCB-CD133+ cells after hypoxia pre-conditioning. The role of HEF-1 in HSCs is unexplored, and its multifunctional contribution in a variety of processes including cell migration, attachment and invasion make HEF-1 a prime candidate as a contributing homing molecule. After identifying a suitable short-hairpin RNA (shRNA) sequence to knockdown HEF-1, generating lentiviral (LV)-particles in house and optimising transduction protocols, HEF-1 knockdown was achieved in haemopoietic model cell lines KG-1 and KG-1A (KG-1/KG-1A–HEF1). Significantly decreased KG-1A–HEF1 cell adhesion to non-stimulated BMEC-60 was detected. Together, these studies provide a promising platform to further explore the role of HEF-1 in hypoxia induced UCB-CD133+ cell transmigration towards the key homing molecule SDF-1α.
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Grijzenhout, Anne Elizabeth. "Characterisation of AEBP2 : a polycomb repressive complex 2 component." Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:159716a1-a03c-44f3-9fd1-0e88328caef6.
Full textBooks on the topic "Plant stem cells"
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Naseem, Muhammad, and Thomas Dandekar, eds. Plant Stem Cells. New York, NY: Springer US, 2020. http://dx.doi.org/10.1007/978-1-0716-0183-9.
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Pavlović, Mirjana, and Ksenija Radotić. Animal and Plant Stem Cells. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-47763-3.
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Gemmotherapy: The science of healing with plant stem cells. Rochester, Vt: Healing Arts Press, 2010.
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Pavlović, Mirjana, and Ksenija Radotić. Animal and Plant Stem Cells: Concepts, Propagation and Engineering. Springer, 2018.
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Hüttermann, Aloys, Ulrich Storz, and Andreas Hübel. Limits of Patentability: Plant Sciences, Stem Cells and Nucleic Acids. Springer, 2012.
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Hüttermann, Aloys, Ulrich Storz, and Andreas Hübel. Limits of Patentability: Plant Sciences, Stem Cells and Nucleic Acids. Springer, 2012.
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Nackid, Thomas A. An analysis of the gravitropic response in Kalenchoë stems. 1991.
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Salinas-Rodríguez, Sergio G., Juan Arévalo, Juan Manuel Ortiz, Eduard Borràs-Camps, Victor Monsalvo-Garcia, Maria D. Kennedy, and Abraham Esteve-Núñez, eds. Microbial Desalination Cells for Low Energy Drinking Water. IWA Publishing, 2021. http://dx.doi.org/10.2166/9781789062120.
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The world's largest demonstrator of a revolutionary energy system in desalination for drinking water production is in operation. MIDES uses Microbial Desalination Cells (MDC) in a pre-treatment step for reverse osmosis (RO), for simultaneous saline stream desalination and wastewater treatment. MDCs are based on bio-electro-chemical technology, in which biological wastewater treatment can be coupled to the desalination of a saline stream using ion exchange membranes without external energy input. MDCs simultaneously treat wastewater and perform desalination using the energy contained in the wastewater. In fact, an MDC can produce around 1.8 kWh of bioelectricity from the energy contained in 1 m3 of wastewater. Compared to traditional RO, more than 3 kWh/m3 of electrical energy is saved. With this novel technology, two low-quality water streams (saline stream, wastewater) are transformed into two high-quality streams (desalinated water, treated wastewater) suitable for further uses. An exhaustive scaling-up process was carried out in which all MIDES partners worked together on nanostructured electrodes, antifouling membranes, electrochemical reactor design and optimization, life cycle assessment, microbial electrochemistry and physiology expertise, and process engineering and control. The roadmap of the lab-MDC upscaling goes through the assembly of a pre-pilot MDC, towards the development of the demonstrator of the MDC technology (patented). Nominal desalination rate between 4-11 Lm-2h-1 is reached with a current efficiency of 40 %. After the scalability success, two MDC pilot plants were designed and constructed consisting of one stack of 15 MDC pilot units with a 0.4 m2 electrode area per unit. This book presents the information generated throughout the EU funded MIDES project and includes the latest developments related to desalination of sea water and brackish water by applying microbial desalination cells. ISBN: 9781789062113 (Paperback) ISBN: 9781789062120 (eBook)
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Evans, Gregory, ed. Operative Plastic Surgery. Oxford University Press, 2019. http://dx.doi.org/10.1093/med/9780190499075.001.0001.
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The second edition of Operative Plastic Surgery is a fully updated, comprehensive text that discusses the most common plastic surgery procedures in great detail. It covers the classic techniques in plastic surgery, as well as the most recent technical advances while maintaining a systematic approach to patient care within each chapter. Traversing the entirety of the human body, each chapter addresses assessment of defects, preoperative factors, pathology, trauma, operative indications and procedures, and more. Also covered is the operative room setup, with special consideration given to the operative plan, patient positioning and markings, and technique for each type of surgery. Detailing more than 90 specific surgical techniques, this book covers both reconstructive and aesthetic plastic surgery. A new section addresses noninvasive techniques such as Botox, injectables, lasers, and skin care. New chapters throughout the book also include anterolateral thigh (ALT) flaps, nasal cleft deformities, zygomaticomaxillary complex (ZMC) fractures, augmentation mastoplexy, body contouring for the massive weight loss patient, and endoscopic carpal tunnel repair. Led by Gregory R. D. Evans, this volume assembles thought leaders in plastic surgery to present operative surgery in a clear, didactic, and comprehensive manner and lays the groundwork for ideas that we have just scratched the surface of, such as translational research, fat grafting, stem cells, and tissue engineering.
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Karmali, Mohamed A., and Jan M. Sargeant. Verocytotoxin-producing Escherichia coli (VTEC) infections. Oxford University Press, 2011. http://dx.doi.org/10.1093/med/9780198570028.003.0008.
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Verocytotoxin (VT)-producing Escherichia coli (VTEC), also known as Shiga toxin producing E. coli (STEC), are zoonotic agents, which cause a potentially fatal illness whose clinical spectrum includes diarrhoea, haemorrhagic colitis, and the haemolytic uraemic syndrome (HUS). VTEC are of serious public health concern because of their association with large outbreaks and with HUS, which is the leading cause of acute renal failure in children. Although over 200 different OH serotypes of VTEC have been associated with human illness, the vast majority of reported outbreaks and sporadic cases of VTEC-infection in humans have been associated with serotype O157:H7.VTs constitute a family of related protein subunit exotoxins, the major ones implicated in human disease being VT1, VT2, and VT2c. Following their translocation into the circulation, VTs bind to endothelial cells of the renal glomeruli, and of other organs and tissues via a specific receptor globotriosylceramide (Gb 3), are internalized by a process of receptor-mediated endocytosis, and cause subcellular damage that results in the characteristic microangiopathic disease observed in HUS.The incubation period of VTEC-associated illness is about 3–5 days. After ingestion VTEC (especially of serotype O157:H7) multiply in the bowel and colonize the mucosa of probably the large bowel with a characteristic attaching and effacing (AE) cytopathology. Colonization is followed by the translocation of VTs into the circulation and the subsequent manifestation of disease.The majority of patients with uncomplicated VTEC infection recover fully with general supportive measures. Historically, the case-fatality rate was high for HUS. However, improvement in the treatment of renal failure and the attendant biochemical disturbances has substantially improved the outlook, although long-term sequelae may develop.Ruminants, especially cattle, are the main reservoirs of VTEC. Infection is acquired through the ingestion of contaminated food, especially under-cooked hamburger, through direct contact with animals, via contaminated water or environments, or via personto-person transmission.The occurrence of large outbreaks of food-borne VTEC-associated illness has promoted close scrutiny of this zoonoses at all levels in the chain of transmission, including the farm, abattoir, food processing, packaging and distribution plants, the wholesaler, the retailer and the consumer. While eradication of VTEC O157 at the farm may not be an option, interventions to increase animal resistance or to decrease animal exposure are being developed and validated. Hazard Analysis and Critical Control Programmes are being implemented in the processing sector and appear to be associated with temporal decreases in VTEC serotype O157 illness in humans. Education programmes targeting food handling procedures and hygiene practices are being advocated at the retail and consumer level. Continued efforts at all stages from the farm to the consumer will be necessary to reduce the risk of VTEC-associated illness in humans.
Book chapters on the topic "Plant stem cells"
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Chowdhury, Suchandra, and Shyamasree Ghosh. "Plant Stem Cell Biology." In Stem Cells, 253–66. Singapore: Springer Singapore, 2021. http://dx.doi.org/10.1007/978-981-16-1638-9_11.
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Lohmann, Jan U. "Plant Stem Cells: Divide et Impera." In Stem Cells, 1–15. Dordrecht: Springer Netherlands, 2008. http://dx.doi.org/10.1007/978-1-4020-8274-0_1.
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Syed, Aqib, Anwar Hussain, Waheed Murad, and Badshah Islam. "Regulatory Role of Phytohormones in Maintaining Stem Cells and Boundaries of Stem Cell Niches." In Plant Stem Cells, 1–16. New York, NY: Springer US, 2019. http://dx.doi.org/10.1007/978-1-0716-0183-9_1.
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Sapala, Aleksandra, and Richard S. Smith. "Osmotic Treatment for Quantifying Cell Wall Elasticity in the Sepal of Arabidopsis thaliana." In Plant Stem Cells, 101–12. New York, NY: Springer US, 2019. http://dx.doi.org/10.1007/978-1-0716-0183-9_11.
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Naseem, Muhammad, Ozge Osmanoglu, Jibran Iqbal, Fares M. Howari, Fatima A. AlRemeithi, Martin Kaltdorf, and Thomas Dandekar. "Mapping a Transcriptome-Guided Arabidopsis SAM Interactome." In Plant Stem Cells, 113–18. New York, NY: Springer US, 2019. http://dx.doi.org/10.1007/978-1-0716-0183-9_12.
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Lavrekha, Viktoriya V., Taras Pasternak, Klaus Palme, and Victoria V. Mironova. "3D Analysis of Mitosis Distribution Pattern in the Plant Root Tip with iRoCS Toolbox." In Plant Stem Cells, 119–25. New York, NY: Springer US, 2019. http://dx.doi.org/10.1007/978-1-0716-0183-9_13.
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Kaya, Ergun, Selin Galatali, Sevinc Guldag, and Onur Celik. "A New Perspective on Cryotherapy: Pathogen Elimination Using Plant Shoot Apical Meristem via Cryogenic Techniques." In Plant Stem Cells, 137–48. New York, NY: Springer US, 2019. http://dx.doi.org/10.1007/978-1-0716-0183-9_15.
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Naseem, Muhammad, Gökhan Gun, Ozge Osmanoglu, Fatima A. AlRemeithi, Jibran Iqbal, and Thomas Dandekar. "Bacterial Shoot Apical Meristem Inoculation Assay." In Plant Stem Cells, 17–22. New York, NY: Springer US, 2019. http://dx.doi.org/10.1007/978-1-0716-0183-9_2.
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Forner, Joachim. "Germline-Transmitted Genome Editing Methodology in Arabidopsis thaliana Using TAL Effector Nucleases." In Plant Stem Cells, 23–30. New York, NY: Springer US, 2019. http://dx.doi.org/10.1007/978-1-0716-0183-9_3.
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Yu, Jie, Ning Zhai, Lin Xu, and Wu Liu. "Method to Study Gene Expression Patterns During De Novo Root Regeneration from Arabidopsis Leaf Explants." In Plant Stem Cells, 31–38. New York, NY: Springer US, 2019. http://dx.doi.org/10.1007/978-1-0716-0183-9_4.
Full textConference papers on the topic "Plant stem cells"
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Sasanuma, I., N. Suzuki, and K. Saito. "Rose essential oils stimulate neural differentiation and autophagy in stem cells." In 67th International Congress and Annual Meeting of the Society for Medicinal Plant and Natural Product Research (GA) in cooperation with the French Society of Pharmacognosy AFERP. © Georg Thieme Verlag KG, 2019. http://dx.doi.org/10.1055/s-0039-3400081.
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Litkouhi, Behrang. "Relationship Between Stress, Height, and Methods of Reproduction for Opuntia Covillea and Opuntia Parryi." In ASME 2001 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2001. http://dx.doi.org/10.1115/imece2001/bed-23000.
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Abstract In this research project, two species of cacti are investigated for relationships between stress, height, and methods of reproduction. These two species are Opuntia covillea, which has flat cladodes, and Opuntia parryi, which has pencil type cladodes. In a previous study, certain relationships were found at the stem segment. The purpose of this study is to confirm those findings, in addition to presenting any new relationships between the factors listed above. Also, a detailed geometric analysis and modeling methodology will be presented. One important point from the last study is that cladodes under the influence of a normal stress (from their own weight) developed approximately two times as many lignified xylem cells on the tensile side than on the compressive side. This would perhaps suggest that these lignified xylem cells prevent failure when they experience tension. This finding, along with other information, allowed an analogy to be drawn up comparing stem segments of cacti to concrete beams, since it is also a property of concrete that it cannot withstand tensile forces if it is not reinforced. Another trend noticed in the last project is that taller cacti plants experience less stress per unit area than shorter plants. Therefore, taller plants have a better ability to hold on to terminal stem segments, and thus have a higher tendency of reproducing sexually. Short plants tend to lose their terminal stem segments into the ground and reproduce asexually through the growth of a new plant from the terminal stem segments.
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Yang, Junhong, Qianqian Di, Jun Zhao, and Liqiu Wang. "Mechanism on Mass Transfer in Micro-Scale During the Microwave Drying of Plant Porous Materials." In ASME 2009 Heat Transfer Summer Conference collocated with the InterPACK09 and 3rd Energy Sustainability Conferences. ASMEDC, 2009. http://dx.doi.org/10.1115/ht2009-88389.
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Astragalus slice is one species of stem and root medicinal herb with the widely curative effects, also a special and typical plant porous material, and the drying operation is one of important processing technologies in its storage and further practical application. This paper characterizes the microstructure of Astragalus slices dried by microwave technique at 200 W by using scanning electronic microscope (SEM). The study also compares Astragalus slices dried by microwave with those untreated and discusses the drying mechanism. Result shows that as compared to the untreated sample, the microwave dried sample behaves much shorter drying time with more and larger pore and open structure on the surface layer of matrix, but without significant change about the distribution status of cytoplasm inside parenchyma cells. Further analysis suggests that the vapor diffusion is the dominant mode of moisture transfer inside matrix during the microwave drying process of sample, resulting in the well-preserved structures of sample, including parenchyma cell and trachea. This is also helpful for maintaining the distribution status of cytoplasm, particularly avoiding the agglomeration of biological macro-molecular, which is benefit to improving the permeability of moisture transfer path, leading to the rapidly dehydration of moisture. This work seems to be helpful for developing the optimized drying technology of plant porous material focused on micro-mechanism and the quality of dried products.
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Valeriu Iancu, Valeriu, Laura Adriana Bucur, Verginica Schröder, and Manuela Rossemary Apetroaei. "PRELIMINARY STUDIES RELATED TO MICROSCOPY AND THE SEDEM EXPERT SYSTEM PROFILE ON FREEZED-DRIED EXTRACT OF LYTHRI HERBA." In GEOLINKS Conference Proceedings. Saima Consult Ltd, 2021. http://dx.doi.org/10.32008/geolinks2021/b1/v3/16.
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"The floral tips of the plant species Lythrum salicaria L. represent a rich source of total polyphenols, among which with the largest share we mention tannins, and this is why this plant material has a standardized monograph in the European Pharmacopoeia 10.0th edition. According to the literature accessed so far, the plant material has antioxidant, anti-inflammatory, hemostatic, antibacterial and antifungal properties, along with modulatory action on carbohydrate metabolism. Powder microscopic examination is an important step in establishing the identity of the plant species used, highlighting elements specific to the aerial part such as spiral vessels of the stem, fragments of the spongy mesophyll with calcium oxalate clusters cells and anomocytic stomata. The application of the SeDeM method on dried plant extracts represents an innovative trend in pharmaceutical technology and contributes to the collection of data in a structured and standardized form. In this paper, the functions and applications of the SeDeM expert system are illustrated upon the freeze-dried extract of Lythri herba for the purpose of easier identification and standardization. Future applications may include obtaining chewable gums or tablets by direct compression."
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Jawaharlal, Mariappan, Gustavo Vargas, and Lorenzo Gutierrez. "The Plant Kingdom in Engineering Design: Learning to Design From Trees." In ASME 2017 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/imece2017-72497.
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A tree may be the earliest multifunctional structure, and wood is the oldest known engineering material. Yet, trees have no place in engineering education. If we view a tree from merely a mechanical or civil engineering perspective, engineering mechanics can be learned from the tree’s example. Trees have survived by adapting to the most difficult circumstances: heavy winds, rains, floods, droughts, earthquakes, mammal damage, human intervention, etc. The root system must be strong and flexible enough to support the tree’s entire structure from varying load conditions and to provide food storage and nutrient transfer. The stem system provides structural support for the tree’s above-the-ground parts and transfers water and nutrients from the roots through the network of thick-walled cells to other parts of the tree. Leaves produce food and form the surface area surrounding the tree. Leaves come in a variety of shapes and sizes. The tree’s crown, comprising branches, leaves, and reproductive elements, help the tree to catch more sunlight. It moves upward and outward to expose more of its leaves to direct sunlight for photosynthesis while maintaining physical balance on the earth. A tree’s lifecycle can span hundreds of years, despite its vulnerability to constantly changing loads throughout the day and throughout its life. In monsoon and windy seasons, trees endure extremely difficult fatigue-loading. Various parts of the tree and its stem are subjected to combined loading conditions: tension, compression, shear, bending, and torsion. Trees develop and adapt stress management strategies by adjusting their shapes to the type or level of stress they endure: they add more mass where more strength is needed, allows material to easily break off (or physiologically inactive) from locations where it is not necessary, design optimum shapes, and create variable notch radii for reducing stress concentration. But a tree is much more than a structural member. It provides food and shelter for wildlife. It absorbs atmospheric carbon dioxide and produces oxygen. It lowers air temperature and facilitates the water cycle. Structural analysis of a tree can benefit engineering students and practicing engineers alike. Furthermore, a deeper understanding of trees can help us to create multifunctional designs that are in a symbiotic relationship with other members in the system. In short, studying tree mechanics can help us to become better engineers. This paper presents our efforts to integrate trees into engineering curricula to teach mechanics ranging from equilibrium study to stress analysis. Students of statics, dynamics, the strength of materials, stress analysis, material science, design, etc., can benefit from learning about trees. This approach enables students to understand the complexities of real-world living systems, appreciate the genius of nature’s design, and develop methods for creating sustainable designs.
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Yang, Junhong, Qianqian Di, Jun Zhao, and Liqiu Wang. "Fractal Dimension of Pore Size Distribution Inside Matrix of Plant Materials and Drying Behavior." In 2010 14th International Heat Transfer Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/ihtc14-22999.
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This paper studied the relationship between matrix microstructure of plant materials and drying behavior using Astragalus and Chinese Angelica root slices as examples. Astragalus and Chinese Angelica, two kinds of traditional Chinese Medicine Herb (CMH), are species of stem and root medicinal herb with the widely curative effects. Based on the measured results by using automatic surface area-porosity analyzer (at smaller scale ≤ 100nm), the volume fractal dimensions (DV) were estimated to characterize the pore size distribution inside matrix of samples dried by different drying technologies, including microwave drying at 200W and conventional hot air drying at 60 °C. In cases studied in this paper, the values of DV are well related with drying time. As compared to hot air dried sample, DV of microwave dried sample increases by 5.9% for Astragalus, while 7.7% for Chinese Angelica. In comparison with hot air drying, the microwave drying time is reduced to 1/6 (30min/180 min) for Astragalus, while 1/16 (50min/810min) for Chinese Angelica. Combined the observation of SEM images of sample, our findings is that, higher fractal dimension, less concentration of pore size distribution, better connectivity of pore or channel with multi-scale characteristics (aperture about 0.1μm–1μm, plasmodesma about 1nm–10nm, or 10Å–100Å), much loose distribution of cytoplasm inside parenchyma cells, better permeability of moisture transfer path during drying process, shorter drying time. Our results demonstrate that the volume fractal dimension (DV) of pore size distribution at smaller scale (≤ 100nm) could give a better understanding the mass transfer behavior of plant materials.
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Yang, Junhong, Qianqian Di, Jun Zhao, and Liqiu Wang. "Effect of Biological Macro-Molecular Flow on the Hot Air Drying of Astragalus Slices." In ASME 2009 Heat Transfer Summer Conference collocated with the InterPACK09 and 3rd Energy Sustainability Conferences. ASMEDC, 2009. http://dx.doi.org/10.1115/ht2009-88385.
Full textAbstract:
Astragalus slice is one species of stem and root medicinal herb with the widely curative effects, also a special and typical plant porous material, and the drying operation is one of important processing technologies in its storage and further practical application. By using scanning electronic microscope (SEM), we mainly characterize the micrographics of parenchyma cell, trachea and aperture of Astragalus slices dried by hot air at 60°C, with the aim to discuss the relationships among the microstructure of sample, macro-drying property and drying mechanism in micro-scale. Results show that in hot air dried sample, the distribution status of cytoplasm inside parenchyma cells appears obvious different with that of untreated sample, behaving agglomeration and leaving wide space with cell wall. Furthermore, we find that in comparison with the untreated sample, the shape of aperture in hot air dried sample basically maintains un-changed, but most of apertures are fully filled with some perceived substance. It is demonstrated that the flow phenomenon of cytoplasm occurs inside matrix accompanied by the moisture diffusion in the mode of liquid water, particularly biological macro-molecular, which directly influence the permeability of moisture transfer path inside matrix and the quality of dried products. Hence, this study has significant meanings to develop the optimized drying technology of plant porous material focused on micro-mechanism and the quality of dried products.
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Pakhomova, V. M., A. I. Daminova, A. Yu Kozhevnikov, and I. V. Galiyakhmetov. "Yield of spring wheat due to lipid peroxidation under the influence of Bacillus oligonitrophilus bacterization." In РАЦИОНАЛЬНОЕ ИСПОЛЬЗОВАНИЕ ПРИРОДНЫХ РЕСУРСОВ В АГРОЦЕНОЗАХ. Federal State Budget Scientific Institution “Research Institute of Agriculture of Crimea”, 2020. http://dx.doi.org/10.33952/2542-0720-15.05.2020.18.
Full textAbstract:
The purpose of the article was to study the resistance of spring wheat under the influence of foliar treatment of plants with silicate bacteria according to lipid peroxidation (LP) and yield. The studies were conducted on spring wheat (variety ‘MiS’). The cultivation technology is typical wheat in this agroclimatic zone. The foliar treatment was carried out with a culture of bacteria Bacillus oligonitrophilus by spraying at the rate of 0.5 l/m2 of bacteria suspension containing 109 cells/ml (equally to 100% concentration). Field experiment design: option 1 – plants without treatment (control); option 2 – treatment with B. oligonitrophilus fertilizers at the stage of tillering; option 3 – treatment with B. oligonitrophilus fertilizers at the stage of tillering/stem elongation; option 4 – treatment with B. oligonitrophilus at the stage of tillering/stem elongation/heading. The activity of LP in wheat leaves was identified according to the content of malondialdehyde (MDA). The content of MDA was determined photometrically during interaction with thiobarbiturate. Wheat yield increase was observed in options 3 and 4 (by 11 and 15%, respectively). The content of MDA decreased in all phases of wheat vegetation in the same experimental options (by 14 and 21%, respectively), which indicated the antioxidant effect of the studied preparation. Thus, the bacterization of wheat with B. oligonitrophilus leads to the plant resistance increase. The protective effect is probably due to the action of a complex of their biologically active substances (metabolites) including the antioxidant mechanism of action.
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Bove, Roberto, and Piero Lunghi. "Comparison Between MCFC/Gas Turbine and MCFC/Steam Turbine Combined Power Plants." In ASME 2003 International Mechanical Engineering Congress and Exposition. ASMEDC, 2003. http://dx.doi.org/10.1115/imece2003-41708.
Full textAbstract:
Worldwide, the main power source to produce electric energy is represented by fossil fuels, principally used at the present time in large combustion power plants. The main environmental impacts of fossil fuel-fired power plants are the use of non-renewable resources and pollutants emissions. An improvement in electric efficiency would yield a reduction in emissions and resources depletion. In fact, if efficiency is raised, in order to produce an amount unit of electric energy, less fuel is required and consequently less pollutants are released. Moreover, higher efficiency leads to economic savings in operating costs. A generally accepted way of improving efficiency is to combine power plants’ cycles. If one of the combined plants is represented by a fuel cell, both thermodynamic efficiency and emissions level are improved. Fuel cells, in fact, are ultra-clean high efficiency energy conversion devices because no combustion occurs in energy production, but only electrochemical reactions and consequently no NOx and CO are produced inside the cell. Moreover, the final product of the reaction is water that can be released into the atmosphere without particular problems. Second generation fuel cells (Solid Oxide FC and Molten Carbonate FC) are particularly suitable for combining cycles, due to their high operating temperature. In previous works, the authors had analyzed the possibility of combining Molten Carbonate Fuel Cell (MCFC) plant with a Gas Turbine and then a MCFC with a Steam Turbine Plant. Results obtained show that both these configurations allow to obtain high conversion efficiencies and reduced emissions. In the present work, a comparison between MCFC-Gas Turbine and MCFC-Steam Turbine is conducted in order to evaluate the main advantages and disadvantages in adopting one solution instead of the other one.
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James, Sean R. "(CS-20-5) The Haunting Mystery of Stem Cell Development: Understanding POLTERGEIST Regulation via Phosphorylation." In ASPB PLANT BIOLOGY 2020. USA: ASPB, 2020. http://dx.doi.org/10.46678/pb.20.989683.
Full textReports on the topic "Plant stem cells"
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Moran, Nava, Richard Crain, and Wolf-Dieter Reiter. Regulation by Light of Plant Potassium Uptake through K Channels: Biochemical, Physiological and Biophysical Study. United States Department of Agriculture, September 1995. http://dx.doi.org/10.32747/1995.7571356.bard.
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The swelling of plant motor cells is regulated by various signals with almost unknown mediators. One of the obligatory steps in the signaling cascade is the activation of K+-influx channels -K+ channels activated by hyperpolarization (KH channels). We thus explored the regulation of these channels in our model system, motor cell protoplasts from Samanea saman, using patch-clamp in the "whole cell" configuration. (a) The most novel finding was that the activity of KH channels in situ varied with the time of the day, in positive correlation with cell swelling: in Extensor cells KH channels were active in the earlier part of the day, while in Flexor cells only during the later part of the day; (b) High internal pH promoted the activity of these channels in Extensor cells, opposite to the behavior of the equivalent channels in guard cells, but in conformity with the predicted behavior of the putative KH channel, cloned from S. saman recently; (c) HIgh external K+ concentration increased (KH channel currents in Flexor cells. BL depolarized the Flexor cells, as detected in cell-attached patch-clamp recording, using KD channels (the K+-efflux channels) as "voltage-sensing devices". Subsequent Red-Light (RL) pulse followed by Darkness, hyperpolarized the cell. We attribute these changes to the inhibition of the H+-pump by BL and its reactivation by RL, as they were abolished by an H+-pump inhibitor. BL increased also the activity KD channels, in a voltage-independent manner - in all probability by an independent signaling pathway. Blue-Light (BL), which stimulates shrinking of Flexor cells, evoked the IP3 signaling cascade (detected directly by IP3 binding assay), known to mobilize cytosolic Ca2+. Nevertheless, cytosolic Ca2+ . did not activate the KD channel in excised, inside-out patches. In this study we established a close functional similarity of the KD channels between Flexor and Extensior cells. Thus the differences in their responses must stem from different links to signaling in both cell types.
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Weil, Clifford F., Anne B. Britt, and Avraham Levy. Nonhomologous DNA End-Joining in Plants: Genes and Mechanisms. United States Department of Agriculture, July 2001. http://dx.doi.org/10.32747/2001.7585194.bard.
Full textAbstract:
Repair of DNA breaks is an essential function in plant cells as well as a crucial step in addition of modified DNA to plant cells. In addition, our inability to introduce modified DNA to its appropriate locus in the plant genome remains an important hurdle in genetically engineering crop species.We have taken a combined forward and reverse genetics approach to examining DNA double strand break repair in plants, focusing primarily on nonhomologous DNA end-joining. The forward approach utilizes a gamma-plantlet assay (miniature plants that are metabolically active but do not undergo cell division, due to cell cycle arrest) and has resulted in identification of five Arabidopsis mutants, including a new one defective in the homolog of the yeast RAD10 gene. The reverse genetics approach has identified knockouts of the Arabidopsis homologs for Ku80, DNA ligase 4 and Rad54 (one gene in what proves to be a gene family involved in DNA repair as well as chromatin remodeling and gene silencing)). All these mutants have phenotypic defects in DNA repair but are otherwise healthy and fertile. Additional PCR based screens are in progress to find knockouts of Ku70, Rad50, and Mre11, among others. Two DNA end-joining assays have been developed to further our screens and our ability to test candidate genes. One of these involves recovering linearized plasmids that have been added to and then rejoined in plant cells; plasmids are either recovered directly or transformed into E. coli and recovered. The products recovered from various mutant lines are then compared. The other assay involves using plant transposon excision to create DNA breaks in yeast cells and then uses the yeast cell as a system to examine those genes involved in the repair and to screen plant genes that might be involved as well. This award supported three graduate students, one in Israel and two in the U.S., as well as a technician in the U.S., and is ultimately expected to result directly in five publications and one Masters thesis.
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Eshed-Williams, Leor, and Daniel Zilberman. Genetic and cellular networks regulating cell fate at the shoot apical meristem. United States Department of Agriculture, January 2014. http://dx.doi.org/10.32747/2014.7699862.bard.
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The shoot apical meristem establishes plant architecture by continuously producing new lateral organs such as leaves, axillary meristems and flowers throughout the plant life cycle. This unique capacity is achieved by a group of self-renewing pluripotent stem cells that give rise to founder cells, which can differentiate into multiple cell and tissue types in response to environmental and developmental cues. Cell fate specification at the shoot apical meristem is programmed primarily by transcription factors acting in a complex gene regulatory network. In this project we proposed to provide significant understanding of meristem maintenance and cell fate specification by studying four transcription factors acting at the meristem. Our original aim was to identify the direct target genes of WUS, STM, KNAT6 and CNA transcription factor in a genome wide scale and the manner by which they regulate their targets. Our goal was to integrate this data into a regulatory model of cell fate specification in the SAM and to identify key genes within the model for further study. We have generated transgenic plants carrying the four TF with two different tags and preformed chromatin Immunoprecipitation (ChIP) assay to identify the TF direct target genes. Due to unforeseen obstacles we have been delayed in achieving this aim but hope to accomplish it soon. Using the GR inducible system, genetic approach and transcriptome analysis [mRNA-seq] we provided a new look at meristem activity and its regulation of morphogenesis and phyllotaxy and propose a coherent framework for the role of many factors acting in meristem development and maintenance. We provided evidence for 3 different mechanisms for the regulation of WUS expression, DNA methylation, a second receptor pathway - the ERECTA receptor and the CNA TF that negatively regulates WUS expression in its own domain, the Organizing Center. We found that once the WUS expression level surpasses a certain threshold it alters cell identity at the periphery of the inflorescence meristem from floral meristem to carpel fate [FM]. When WUS expression highly elevated in the FM, the meristem turn into indeterminate. We showed that WUS activate cytokinine, inhibit auxin response and represses the genes required for root identity fate and that gradual increase in WUCHEL activity leads to gradual meristem enlargement that affect phyllotaxis. We also propose a model in which the direction of WUS domain expansion laterally or upward affects meristem structure differently. We preformed mRNA-seq on meristems with different size and structure followed by k-means clustering and identified groups of genes that are expressed in specific domains at the meristem. We will integrate this data with the ChIP-seq of the 4 TF to add another layer to the genetic network regulating meristem activity.
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Granot, David, and Richard Amasino. Regulation of Senescence by Sugar Metabolism. United States Department of Agriculture, January 2003. http://dx.doi.org/10.32747/2003.7585189.bard.
Full textAbstract:
Research objectives a. Analyze transgenic plants that undergo rapid senescence due to increased expression of hexokinase. b. Determine if hexokinase-induced senescence accelerates natural senescence using senescence specific promoters that drive expression of a reporter gene (GUS) and a cytokinin producing gene (IPT - isopentyl transferase). c. Isolate and analyze plant genes that suppress sugar-induced cell death (SICD) in yeast, genes that potentially are involved in programmed cell death and senescence in plants. Background to the topic Leaf senescence is a regulated process of programmed cell death (PCD) in which metabolites are recycled to other active parts of the plant. Senescence associated genes (SAGs) are expressed throughout leaf senescence. Sugar flux and metabolism is thought to playa fundamental regulatory role in senescence. We found that transgenic tomato plants with high hexokinase activity, the initial enzymatic step of sugar (hexose) metabolism, undergo rapid leaf senescence, directly correlated with hexokinase activity. These plants provide a unique opportunity to analyze the regulatory role of sugar metabolism in senescence, and its relation to cytokinin, a senescence-inhibiting hormone. In addition, we found that sugar induces programmed cells death of yeast cells in direct correlation to hexokinase activity. We proposed to use the sugar induced cell death (SICD) to isolate Arabidopsis genes that suppress SICD. Such genes could potentially be involved in senescence induced PCD in plants. Major conclusions The promoters of Arabidopsis senescence-associated genes, SAG12 and SAGI3, are expressed in senescing tomato leaves similar to their expression in Arabidopsis leaves, indicating that these promoters are good senescence markers for tomato plants. Increased hexokinase activity accelerated senescence and induced expression of pSAG12 and pSAG13 promoters in tomato plants, suggesting that sugar regulate natural senescence via hexokinase. Expression of IPT, a cytokinin producing gene, under pSAG12 and pSAG13 promoters, delayed senescence of tomato leaves. Yet, senescence accelerated by hexokinase was epistatic over cytokinin, indicating that sugar regulation of senescence is dominant over the senescence-inhibiting hormone. A gene designated SFP1, which is similar to the major super family monosaccharide transporters, is induced during leaf senescence in Arabidopsis and may be involved in sugar transport during senescence. Accordingly, adult leaves accumulate sugars that may accelerate hexokinase activity. Light status of the entire plant affects the senescence of individual leaves. When individual leaves are darkened, senescence is induced in the covered leaves. However, whole adult plant placed in darkness show delayed senescence. In a search for Arabidopsis genes that suppress SICD we isolated 8 cDNA clones which confer partial resistance to SICD. One of the clones encodes a vesicle associated membrane protein - VAMP. This is the first evidence that vesicle trafficking might be involved in cell death. Implications Increased hexokinase activity accelerates senescence. We hypothesized that, reduced hexokinase activity may delay senescence. Preliminary experiments using a hexokinase inhibitor support this possible implication. Currently we are analyzing various practical approaches to delay leaf senescence via hexokinase inhibition. .
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Coplin, David L., Shulamit Manulis, and Isaac Barash. roles Hrp-dependent effector proteins and hrp gene regulation as determinants of virulence and host-specificity in Erwinia stewartii and E. herbicola pvs. gypsophilae and betae. United States Department of Agriculture, June 2005. http://dx.doi.org/10.32747/2005.7587216.bard.
Full textAbstract:
Gram-negative plant pathogenic bacteria employ specialized type-III secretion systems (TTSS) to deliver an arsenal of pathogenicity proteins directly into host cells. These secretion systems are encoded by hrp genes (for hypersensitive response and pathogenicity) and the effector proteins by so-called dsp or avr genes. The functions of effectors are to enable bacterial multiplication by damaging host cells and/or by blocking host defenses. We characterized essential hrp gene clusters in the Stewart's Wilt of maize pathogen, Pantoea stewartii subsp. stewartii (Pnss; formerly Erwinia stewartii) and the gall-forming bacterium, Pantoea agglomerans (formerly Erwinia herbicola) pvs. gypsophilae (Pag) and betae (Pab). We proposed that the virulence and host specificity of these pathogens is a function of a) the perception of specific host signals resulting in bacterial hrp gene expression and b) the action of specialized signal proteins (i.e. Hrp effectors) delivered into the plant cell. The specific objectives of the proposal were: 1) How is the expression of the hrp and effector genes regulated in response to host cell contact and the apoplastic environment? 2) What additional effector proteins are involved in pathogenicity? 3) Do the presently known Pantoea effector proteins enter host cells? 4) What host proteins interact with these effectors? We characterized the components of the hrp regulatory cascade (HrpXY ->7 HrpS ->7 HrpL ->7 hrp promoters), showed that they are conserved in both Pnss and Fag, and discovered that the regulation of the hrpS promoter (hrpSp) may be a key point in integrating apoplastic signals. We also analyzed the promoters recognized by HrpL and demonstrated the relationship between their composition and efficiency. Moreover, we showed that promoter strength can influence disease expression. In Pnss, we found that the HrpXY two-component signal system may sense the metabolic status of the bacterium and is required for full hrp gene expression in planta. In both species, acyl-homoserine lactone-mediated quorum sensing may also regulate epiphytic fitness and/or pathogenicity. A common Hrp effector protein, DspE/WtsE, is conserved and required for virulence of both species. When introduced into corn cells, Pnss WtsE protein caused water-soaked lesions. In other plants, it either caused cell death or acted as an Avr determinant. Using a yeast- two-hybrid system, WtsE was shown to interact with a number of maize signal transduction proteins that are likely to have roles in either programmed cell death or disease resistance. In Pag and Pab, we have characterized the effector proteins HsvG, HsvB and PthG. HsvG and HsvB are homologous proteins that determine host specificity of Pag and Pab on gypsophila and beet, respectively. Both possess a transcriptional activation domain that functions in yeast. PthG was found to act as an Avr determinant on multiple beet species, but was required for virulence on gypsophila. In addition, we demonstrated that PthG acts within the host cell. Additional effector genes have been characterized on the pathogenicity plasmid, pPATHₚₐg, in Pag. A screen for HrpL- regulated genes in Pnsspointed up 18 candidate effector proteins and four of these were required for full virulence. It is now well established that the virulence of Gram-negative plant pathogenic bacteria is governed by Hrp-dependent effector proteins. However; the mode of action of many effectors is still unresolved. This BARD supported research will significantly contribute to the understanding of how Hrp effectors operate in Pantoea spp. and how they control host specificity and affect symptom production. This may lead to novel approaches for genetically engineering plants resistant to a wide range of bacterial pathogens by inactivating the Hrp effectors with "plantabodies" or modifying their receptors, thereby blocking the induction of the susceptible response. Alternatively, innovative technologies could be used to interfere with the Hrp regulatory cascade by blocking a critical step or mimicking plant or quorum sensing signals.
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Wolf, Shmuel, and William J. Lucas. Involvement of the TMV-MP in the Control of Carbon Metabolism and Partitioning in Transgenic Plants. United States Department of Agriculture, October 1999. http://dx.doi.org/10.32747/1999.7570560.bard.
Full textAbstract:
The function of the 30-kilodalton movement protein (MP) of tobacco mosaic virus (TMV) is to facilitate cell-to-cell movement of viral progeny in infected plants. Our earlier findings have indicated that this protein has a direct effect on plasmodesmal function. In addition, these studies demonstrated that constitutive expression of the TMV MP gene (under the control of the CaMV 35S promoter) in transgenic tobacco plants significantly affects carbon metabolism in source leaves and alters the biomass distribution between the various plant organs. The long-term goal of the proposed research was to better understand the factors controlling carbon translocation in plants. The specific objectives were: A) To introduce into tobacco and potato plants a virally-encoded (TMV-MP) gene that affects plasmodesmal functioning and photosynthate partitioning under tissue-specific promoters. B) To introduce into tobacco and potato plants the TMV-MP gene under the control of promoters which are tightly repressed by the Tn10-encoded Tet repressor, to enable the expression of the protein by external application of tetracycline. C) To explore the mechanism by which the TMV-MP interacts with the endogenous control o~ carbon allocation. Data obtained in our previous project together with the results of this current study established that the TMV-MP has pleiotropic effects when expressed in transgenic tobacco plants. In addition to its ability to increase the plasmodesmal size exclusion limit, it alters carbohydrate metabolism in source leaves and dry matter partitioning between the various plant organs, Expression of the TMV-MP in various tissues of transgenic potato plants indicated that sugars and starch levels in source leaves are reduced below those of control plants when the TMV-MP is expressed in green tissue only. However, when the TMV-MP was expressed predominantly in PP and CC, sugar and starch levels were raised above those of control plants. Perhaps the most significant result obtained from experiments performed on transgenic potato plants was the discovery that the influence of the TMV-MP on carbohydrate allocation within source leaves was under developmental control and was exerted only during tuber development. The complexity of the mode by which the TMV-MP exerts its effect on the process of carbohydrate allocation was further demonstrated when transgenic tobacco plants were subjected to environmental stresses such as drought stress and nutrients deficiencies, Collectively, these studies indicated that the influence of the TMV-MP on carbon allocation L the result of protein-protein interaction within the source tissue. Based on these results, together with the findings that plasmodesmata potentiate the cell-to-cell trafficking of viral and endogenous proteins and nucleoproteins complexes, we developed the theme that at the whole plant level, the phloem serves as an information superhighway. Such a long-distance communication system may utilize a new class of signaling molecules (proteins and/or RNA) to co-ordinate photosynthesis and carbon/nitrogen metabolism in source leaves with the complex growth requirements of the plant under the prevailing environmental conditions. The discovery that expression of viral MP in plants can induce precise changes in carbon metabolism and photoassimilate allocation, now provide a conceptual foundation for future studies aimed at elucidating the communication network responsible for integrating photosynthetic productivity with resource allocation at the whole-plant level. Such information will surely provide an understanding of how plants coordinate the essential physiological functions performed by distantly-separated organs. Identification of the proteins involved in mediating and controlling cell-to-cell transport, especially at the companion cell-sieve element boundary, will provide an important first step towards achieving this goal.
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Granot, David, and Noel Michelle Holbrook. Role of Fructokinases in the Development and Function of the Vascular System. United States Department of Agriculture, January 2011. http://dx.doi.org/10.32747/2011.7592125.bard.
Full textAbstract:
Plant vascular tissues are superhighways whose development and function have profound implications for productivity, yield and stress response. Preliminary studies by the PI indicated that sugar metabolism mediated by fructokinases (FRKs) has a pronounced effect on the transport properties of the xylem. The goal of this research was to determine how the main fructokinase gene, FRK2, and the only plastidic fructokinase, FRK3, influence vascular development and physiology, emphasizing processes that occur at both the cellular and organismic level. We found that both genes are expressed in vascular tissues, but FRK3 is expressed primarily in vascular tissues of mature petioles. Vascular anatomy of plants with antisense suppression of FRK2 uncovered that FRK2 is necessary for xylem and phloem development, most likely due to its role in vascular cell-wall synthesis, and affects vascular development all over the plant. As a result, suppression of FRK2 reduced hydraulic conductivity of roots, stem and leaves and restricted sugar phloem transport. Vascular anatomy of plants with RNAi suppression of FRK3 uncovered that FRK3 is required for vascular development in mature petiole but its role is partially complemented by FRK2. Suppression of FRK3 combined with partial suppression of FRK2 had effects completely different from that of FRK2 suppression, resulting in wilting of mature leaves rather than young leaves of FRK2 suppressed plants, and decreased export of photoassimilates. This primary effect of FRK2 suppression on mature petioles had a secondary effect, reducing the hydraulic conductivity in roots and stem. The very fact that a plastidic fructokinase plays a role in vascular development is quite surprising and we are still seeking to uncover its metabolic mode-of-action. Yet, it is clear that these two fructokinases have different roles in the coordination between photosynthetic capacity and vascular development. We have started analyzing the role of the last third FRK, FRK1, and discovered that it is also expressed exclusively in vascular tissues. It appears therefore, that all FRKs studied here are involved in vascular development. An interesting unexpected outcome of this study was the connection of FRK2 with hormonal regulation of vascular development, most likely auxin. This observation together with the yet to be solved questions on the exact roles of FRK3 are the subjects of our current efforts.
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McClure, Michael A., Yitzhak Spiegel, David M. Bird, R. Salomon, and R. H. C. Curtis. Functional Analysis of Root-Knot Nematode Surface Coat Proteins to Develop Rational Targets for Plantibodies. United States Department of Agriculture, October 2001. http://dx.doi.org/10.32747/2001.7575284.bard.
Full textAbstract:
The goal of this research was to provide a better understanding of the interface between root-knot nematodes, Meloidogyne spp., and their host in order to develop rational targets for plantibodies and other novel methods of nematode control directed against the nematode surface coat (SC). Specific objectives were: 1. To produce additional monoclonal SC antibodies for use in Objectives 2, 3, and 4 and as candidates for development of plantibodies. 2. To determine the production and distribution of SC proteins during the infection process. 3. To use biochemical and immunological methods to perturbate the root-knot nematode SC in order to identify SC components that will serve as targets for rationally designed plantibodies. 4. To develop SC-mutant nematodes as additional tools for defining the role of the SC during infection. The external cuticular layer of nematodes is the epicuticle. In many nematodes, it is covered by a fuzzy material termed "surface coat" (SC). Since the SC is the outermost layer, it may playa role in the interaction between the nematode and its surroundings during all life stages in soil and during pathogenesis. The SC is composed mainly of proteins, carbohydrates (which can be part of glycoproteins), and lipids. SC proteins and glycoproteins have been labeled and extracted from preparasitic second-stage juveniles and adult females of Meloidogyne and specific antibodies have been raised against surface antigens. Antibodies can be used to gain more information about surface function and to isolate genes encoding for surface antigens. Characterization of surface antigens and their roles in different life-stages may be an important step towards the development of alternative control. Nevertheless, the role of the plant- parasitic nematode's surface in plant-nematode interaction is still not understood. Carbohydrates or carbohydrate-recognition domains (CROs) on the nematode surface may interact with CROs or carbohydrate molecules, on root surfaces or exudates, or be active after the nematode has penetrated into the root. Surface antigens undoubtedly play an important role in interactions with microorganisms that adhere to the nematodes. Polyclonal (PC) and monoclonal (MC) antibodies raised against Meloidogyne javanica, M. incognita and other plant-parasitic nematodes, were used to characterize the surface coat and secreted-excreted products of M. javanica and M. incognita. Some of the MC and PC antibodies raised against M. incognita showed cross-reactivity with the surface coat of M. javanica. Further characterization, in planta, of the epitopes recognized by the antibodies, showed that they were present in the parasitic juvenile stages and that the surface coat is shed during root penetration by the nematode and its migration between root cells. At the molecular level, we have followed two lines of experimentation. The first has been to identify genes encoding surface coat (SC) molecules, and we have isolated and characterized a small family of mucin genes from M. incognita. Our second approach has been to study host genes that respond to the nematode, and in particular, to the SC. Our previous work has identified a large suite of genes expressed in Lycopersicon esculentum giant cells, including the partial cDNA clone DB#131, which encodes a serine/threonine protein kinase. Isolation and predicted translation of the mature cDNA revealed a frame shift mutation in the translated region of nematode sensitive plants. By using primers homologous to conserved region of DB#131 we have identified the orthologues from three (nematode-resistant) Lycopersicon peruvianum strains and found that these plants lacked the mutation.
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Philosoph-Hadas, Sonia, Peter B. Kaufman, Shimon Meir, and Abraham H. Halevy. Inhibition of the Gravitropic Shoot Bending in Stored Cut Flowers Through Control of Their Graviperception: Involvement of the Cytoskeleton and Cytosolic Calcium. United States Department of Agriculture, December 2005. http://dx.doi.org/10.32747/2005.7586533.bard.
Full textAbstract:
Original objectives: The basic goal of the present project was to study the mechanism involved in shoot graviperception and early transduction, in order to determine the sequence of events operating in this process. This will enable to control the entire process of gravity-induced differential growth without affecting vertical growth processes essential for development. Thus, several new postulated interactions, operating at the perception and early transduction stages of the signaling cascade leading to auxin-mediated bending, were proposed to be examined in snapdragon spikes and oat shoot pulvini, according to the following research goals: 1) Establish the role of amyloplasts as gravireceptors in shoots; 2) Investigate gravity-induced changes in the integrity of shoot actin cytoskeleton (CK); 3) Study the cellular interactions among actin CK, statoliths and cell membranes (endoplasmic reticulum - ER, plasma membrane - PM) during shoot graviperception; 4) Examine mediation of graviperception by modulations of cytosolic calcium - [Ca2+]cyt, and other second messengers (protein phosphorylation, inositol 1,4,5-trisphosphate - IP3). Revisions: 1) Model system: in addition to snapdragon (Antirrhinum majus L.) spikes and oat (Avena sativa) shoot pulvini, the model system of maize (Zea mays) primary roots was targeted to confirm a more general mechanism for graviperception. 2) Research topic: brassinolide, which were not included in the original plan, were examined for their regulatory role in gravity perception and signal transduction in roots, in relation to auxin and ethylene. Background to the topic: The negative gravitropic response of shoots is a complex multi-step process that requires the participation of various cellular components acting in succession or in parallel. Most of the long-lasting studies regarding the link between graviperception and cellular components were focused mainly on roots, and there are relatively few reports on shoot graviperception. Our previous project has successfully characterized several key events occurring during shoot bending of cut flowers and oat pulvini, including amyloplast displacement, hormonal interactions and differential growth analysis. Based on this evidence, the present project has focused on studying the initial graviperception process in flowering stems and cereal shoots. Major conclusions and achievements: 1) The actin and not the microtubule (MT) CK is involved in the graviperception of snapdragon shoots. 2) Gravisensing, exhibited by amyloplast displacement, and early transduction events (auxin redistribution) in the gravitropic response of snapdragon spikes are mediated by the acto-myosin complex. 3) MTs are involved in stem directional growth, which occurs during gravitropism of cut snapdragon spikes, but they are not necessary for the gravity-induced differential growth. 4) The role of amyloplasts as gravisensors in the shoot endodermis was demonstrated for both plant systems. 5) A gravity-induced increase in IP.
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Elbaum, Michael, and Peter J. Christie. Type IV Secretion System of Agrobacterium tumefaciens: Components and Structures. United States Department of Agriculture, March 2013. http://dx.doi.org/10.32747/2013.7699848.bard.
Full textAbstract:
Objectives: The overall goal of the project was to build an ultrastructural model of the Agrobacterium tumefaciens type IV secretion system (T4SS) based on electron microscopy, genetics, and immunolocalization of its components. There were four original aims: Aim 1: Define the contributions of contact-dependent and -independent plant signals to formation of novel morphological changes at the A. tumefaciens polar membrane. Aim 2: Genetic basis for morphological changes at the A. tumefaciens polar membrane. Aim 3: Immuno-localization of VirB proteins Aim 4: Structural definition of the substrate translocation route. There were no major revisions to the aims, and the work focused on the above questions. Background: Agrobacterium presents a unique example of inter-kingdom gene transfer. The process involves cell to cell transfer of both protein and DNA substrates via a contact-dependent mechanism akin to bacterial conjugation. Transfer is mediated by a T4SS. Intensive study of the Agrobacterium T4SS has made it an archetypal model for the genetics and biochemistry. The channel is assembled from eleven protein components encoded on the B operon in the virulence region of the tumor-inducing plasmid, plus an additional coupling protein, VirD4. During the course of our project two structural studies were published presenting X-ray crystallography and three-dimensional reconstruction from electron microscopy of a core complex of the channel assembled in vitro from homologous proteins of E. coli, representing VirB7, VirB9, and VirB10. Another study was published claiming that the secretion channels in Agrobacterium appear on helical arrays around the membrane perimeter and along the entire length of the bacterium. Helical arrangements in bacterial membranes have since fallen from favor however, and that finding was partially retracted in a second publication. Overall, the localization of the T4SS within the bacterial membranes remains enigmatic in the literature, and we believe that our results from this project make a significant advance. Summary of achievements : We found that polar inflations and other membrane disturbances relate to the activation conditions rather than to virulence protein expression. Activation requires low pH and nutrient-poor medium. These stress conditions are also reflected in DNA condensation to varying degrees. Nonetheless, they must be considered in modeling the T4SS as they represent the relevant conditions for its expression and activity. We identified the T4SS core component VirB7 at native expression levels using state of the art super-resolution light microscopy. This marker of the secretion system was found almost exclusively at the cell poles, and typically one pole. Immuno-electron microscopy identified the protein at the inner membrane, rather than at bridges across the inner and outer membranes. This suggests a rare or transient assembly of the secretion-competent channel, or alternatively a two-step secretion involving an intermediate step in the periplasmic space. We followed the expression of the major secreted effector, VirE2. This is a single-stranded DNA binding protein that forms a capsid around the transferred oligonucleotide, adapting the bacterial conjugation to the eukaryotic host. We found that over-expressed VirE2 forms filamentous complexes in the bacterial cytoplasm that could be observed both by conventional fluorescence microscopy and by correlative electron cryo-tomography. Using a non-retentive mutant we observed secretion of VirE2 from bacterial poles. We labeled the secreted substrates in vivo in order detect their secretion and appearance in the plant cells. However the low transfer efficiency and significant background signal have so far hampered this approach.