The Experts below are selected from a list of 207 Experts worldwide ranked by ideXlab platform
William A. Tramontano - One of the best experts on this subject based on the ideXlab platform.
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Histone deacetylase inhibitors and cell proliferation in pea Root Meristems
Phytochemistry, 2000Co-Authors: James P Murphy, Jody P Mcaleer, Anthony Uglialoro, Jessica Papile, Jason Weniger, Floyd Bethelmie, William A. TramontanoAbstract:Abstract The histone deacetylase (HDA) inhibitors, trichostatin A (TSA) and HC toxin halt mitosis in cultured Root Meristems of Pisum sativum , while the anti-protozoan HDA inhibitor apicidin is ineffective. Two-dimensional PAGE of proteins from Root Meristems exposed to TSA and HC toxin did not show significant differences compared to controls, although a previously tested HDA inhibitor, butyrate, exhibited dramatic variations in its protein profile. Northern analysis of butyrate- and TSA-treated Root Meristems indicated that non-proliferating cells are expressing significant amounts of transcripts of the known cell proliferation associated genes: histone H2A, MAP kinase, cycA2:1 and cdc2. Western analysis reveals the presence of hyperacetylated nuclear proteins in HDA-inhibitor treated cells. These results suggest that the HDA inhibitors, butyrate and TSA, halt mitosis without down-regulating genes that typically have low or nonexistent expression levels in non-dividing cells.
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Cell cycle inhibition by sodium butyrate in legume Root Meristems
Phytochemistry, 1996Co-Authors: William A. Tramontano, Christine ScanlonAbstract:Abstract Previous investigations demonstrated that butyric, propionic and valeric acids reduced the mitotic index in cultured Root Meristems of peas ( Pisum sativum ). These compounds also inhibited DNA synthesis and the progression of cells through the cell cycle. Cultured pea Roots, exposed to either 0.1 mM 14 C-labelled butyrate or propionate, incorporated the isotope and transported it into the nucleus. Experiments have now been performed to determine if cultured Roots of other legume species such as soybean ( Glycine max ), pinto bean ( Phaseolus vulgaris ) and broad bean ( Vicia faba ) also respond to butyrate in a similar manner. After a 24-hr butyrate exposure, the mitotic index in the Root Meristems was greatly reduced in all three test species, even at butyrate concentrations as low as 0.1 mM. The mitotic index in broad bean Roots exposed to either 1 or 5 mM butyrate was reduced as quickly as 6 hr post-exposure. When broad bean Roots were exposed to 5 mM butyrate, [ 3 H]-TdR incorporation was inhibited by 8 hr, indicating a reduction in DNA synthesis. These experiments demonstrate that other legume species respond to butyrate exposure by reducing their overall mitotic index and halting progression through the cell cycle.
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Incorporation and cell-cycle effects of short-chain fatty acids in pea Root Meristems
Phytochemistry, 1994Co-Authors: William A. Tramontano, Patricia Gelardi, Diana JouveAbstract:Abstract Past investigations from this laboratory demonstrated that butyric, propionic and valeric acids diminished mitosis in Root Meristems of peas ( Pisum sativum ), as well as inhibiting DNA synthesis; longer-chain fatty acids were inactive. Experiments have now been performed to determine incorporation rates of [1- 14 C]-labelled short-chain fatty acids. Cultured pea Roots, exposed to either 0.1 mM labelled butyric or propionic acid, showed a steady overall increase in isotope incorporation during the 6 hr exposure period. Autoradiographic studies also demonstrated increased nuclear incorporation of the isotope with time. These experiments support past investigations that short-chain fatty acids, once incorporated into the Root meristem, alter its cell cycle physiology.
Elizabeth E. Hansen - One of the best experts on this subject based on the ideXlab platform.
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Plant Regeneration from Callus and Cell Suspension Cultures by Somatic Embryogenesis
Plant Cell Tissue and Organ Culture, 1995Co-Authors: Gregory C. Phillips, John F. Hubstenberger, Elizabeth E. HansenAbstract:Plant regeneration by somatic embryogenesis from cultured cells was originally observed with carrot (Steward et al. 1958). In somatic embryogenesis, somatic cells develop by division to form complete embryos analogous to zygotic embryos. The bipolar structure of the somatic embryo contains both shoot and Root Meristems. As the embryos develop, they progress through the distinct structural steps of the globular, heart, torpedo, cotyledonary, and mature stages. Plant regeneration by adventitious somatic embryogenesis will be discussed in Chapter 8.
Janusz Maszewski - One of the best experts on this subject based on the ideXlab platform.
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dna replication stress induces deregulation of the cell cycle events in Root Meristems of allium cepa
Annals of Botany, 2012Co-Authors: Aneta żabka, Justyna Teresa Polit, Janusz MaszewskiAbstract:† Background and Aims Prolonged treatment of Allium cepa Root Meristems with changing concentrations of hydroxyurea (HU) results in either premature chromosome condensation or cell nuclei with an uncommon form of biphasic chromatin organization. The aim of the current study was to assess conditions that compromise cell cycle checkpoints and convert DNA replication stress into an abnormal course of mitosis. † Methods Interphase-mitotic (IM) cells showing gradual changes of chromatin condensation were obtained following continuous 72 h treatment of seedlings with 0.75 mM HU (without renewal of the medium). HU-treated Root Meristems were analysed using histochemical stainings (DNA-DAPI/Feulgen; starch-iodide and DAB staining for H2O2 production), Western blotting [cyclin B-like (CBL) proteins] and immunochemistry (BrdU incorporation, detection of g-H2AX and H3S10 phosphorylation). † Key Results Continuous treatment of onion seedlings with a low concentration of HU results in shorter Root Meristems, enhanced production of H2O2, g-phosphorylation of H2AX histones and accumulation of CBL proteins. HU-induced replication stress gives rise to axially elongated cells with half interphase/half mitotic structures (IM-cells) having both decondensed and condensed domains of chromatin. Long-term HU treatment results in cell nuclei resuming S phase with gradients of BrdU labelling. This suggests a polarized distribution of factors needed to re-initiate stalled replication forks. Furthermore, prolonged HU treatment extends both the relative time span and the spatial scale of H3S10 phosphorylation known in plants. † Conclusions The minimum cell length and a threshold level of accumulated CBL proteins are both determining factors by which the nucleus attains commitment to induce an asynchronous course of chromosome condensation. Replication stress-induced alterations in an orderly route of the cell cycle events probably reflect a considerable reprogramming of metabolic functions of chromatin combined with gradients of morphological changes spread along the nucleus.
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lAA and BAP affect protein phosphorylation-dependent processes during sucrose-mediated G1 to S and G2 to M transitions in Root meristem cells of Vicia faba
Acta Societatis Botanicorum Poloniae, 2011Co-Authors: Justyna Teresa Polit, Janusz Maszewski, Marzena RosiakAbstract:In carbohydrate-starved Root Meristems of Vicia faba subsp. minor, the expression of two Principal Control Points located at the final stages of the G1 (PCP1) and G2 (PCP2) phases has been found to be correlated with a marked decrease of protein phosphorylation within cell nuclei, nucleoli and cytoplasm. Adopting the same experimental model in our present studies, monoclonal FITC conjugated antibodies that recognize phosphorylated form of threonine (αT P ab-FITC) were used to obtain an insight about how the indole-3-acetic acid (IAA), benzyl-6-aminopurine (BAP), and the mixture of both phytohormones influence the time-course changes in an overall protein phosphorylation during sucrose-mediated PCP1→S and PCP2→M transitions. Unsuspectedly, neither IAA, BAP, nor the mixture of both phytohormones supplied in combination with sucrose did up-regulate protein phosphorylation. However using the block-and-release method, it was shown that Root Meristems of Vicia provided with sucrose alone indicated higher levels of αT P ab-FITC. Contrarily, phytohormones supplied in combination with sucrose induced apparent decline in phosphorylation of cell proteins, which - when compared with the influence of sucrose alone - became increasingly evident in time. Thus, it seems probable, that a general decline in the amount of αT P ab-FITC labeled epitopes may overlay specific phosphorylations and dephosphorylations governed by the main cell cycle kinases and phosphatases.
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effect of oa inhibitor of protein phosphatases pp1 and pp2a on initiation of dna replication and mitosis in vicia faba Root Meristems
Acta Physiologiae Plantarum, 2005Co-Authors: Justyna Teresa Polit, Janusz MaszewskiAbstract:According to the principal control point (PCP) hypothesis, experiments with excised, carbohydrate-starved stationary Root Meristems of Vicia faba var. minor have demonstrated that cells which previously divided asynchronously were preferentially blocked in G1 (PCP1) and G2 (PCP2) phases. When stationary phase Meristems are supplied with exogenous carbohydrate (2 % sucrose), the G1- and G2-arrested cells start out DNA replication and mitotic divisions, respectively. The resumption of DNA synthesis and mitosis is not immediate and the delays of G1- and G2-arrested cells are found different. Using this model, we examined the effects of 4 pulse incubations with okadaic acid (OA), a specific inhibitor of PP1 and PP2A, on the duration of intervals elapsing between the provision of sucrose and the first appearance of S- and M-phase cells. We have found that depending on the period during which OA had been applied, the release from G1 and G2 phase arrest-points becomes prolonged, showing different time-course modifications. The obtained data provide evidence that activation of PP1 and PP2A is required to allow the cells for both PCP1→S and PCP2→M transitions in Root Meristems of V. faba.
R Simon - One of the best experts on this subject based on the ideXlab platform.
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a signaling module controlling the stem cell niche in arabidopsis Root Meristems
Current Biology, 2009Co-Authors: Yvonne Stahl, Rene H Wink, Gwyneth C Ingram, R SimonAbstract:The niches of the Arabidopsis shoot and Root Meristems, the organizing center (OC) and the quiescent center (QC), orchestrate the fine balance of stem cell maintenance and the provision of differentiating descendants. They express the functionally related homeobox genes WUSCHEL (WUS) and WOX5, respectively, that promote stem cell fate in adjacent cells [1]. Shoot stem cells signal back to the OC by secreting the CLAVATA3 (CLV3) dodecapeptide [2], which represses WUS expression [3]. However, the signals controlling homeostasis of the Root stem cell system are not identified to date. Here we show that the differentiating descendants of distal Root stem cells express CLE40, a peptide closely related to CLV3. Reducing CLE40 levels delays differentiation and allows stem cell proliferation. Conversely, increased CLE40 levels drastically alter the expression domain of WOX5 and promote stem cell differentiation. We report that the receptor kinase ACR4, previously shown to control cell proliferation [4], is an essential component, and also a target, of CLE40 signaling. Our results reveal how, in contrast to the shoot system, signals originating from differentiated cells, but not the stem cells, determine the size and position of the Root niche.
Christine Scanlon - One of the best experts on this subject based on the ideXlab platform.
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Cell cycle inhibition by sodium butyrate in legume Root Meristems
Phytochemistry, 1996Co-Authors: William A. Tramontano, Christine ScanlonAbstract:Abstract Previous investigations demonstrated that butyric, propionic and valeric acids reduced the mitotic index in cultured Root Meristems of peas ( Pisum sativum ). These compounds also inhibited DNA synthesis and the progression of cells through the cell cycle. Cultured pea Roots, exposed to either 0.1 mM 14 C-labelled butyrate or propionate, incorporated the isotope and transported it into the nucleus. Experiments have now been performed to determine if cultured Roots of other legume species such as soybean ( Glycine max ), pinto bean ( Phaseolus vulgaris ) and broad bean ( Vicia faba ) also respond to butyrate in a similar manner. After a 24-hr butyrate exposure, the mitotic index in the Root Meristems was greatly reduced in all three test species, even at butyrate concentrations as low as 0.1 mM. The mitotic index in broad bean Roots exposed to either 1 or 5 mM butyrate was reduced as quickly as 6 hr post-exposure. When broad bean Roots were exposed to 5 mM butyrate, [ 3 H]-TdR incorporation was inhibited by 8 hr, indicating a reduction in DNA synthesis. These experiments demonstrate that other legume species respond to butyrate exposure by reducing their overall mitotic index and halting progression through the cell cycle.
