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111.
Lateral root development in cultured seedlings of Pisum sativum (cv. Alaska) was modified by the application of auxin transport inhibitors or antagonists. When applied either to replace the root tip or beneath the cotyledonary node, two auxin transport inhibitors, 2,3,5-triiodobenzoic acid (TIBA) and 3,3a-dihydro-2-(p-methoxyphenyl)-8H-pyrazolo[5,1-α]isoindol-8-one (DPX-1840), increased cell division activity opposite the protoxylem poles. This resulted in the formation of masses of cells, which we are calling root primordial masses (RPMs), 2 to 3 days after treatment. RPMs differed from lateral root primordia in that they lacked apical organization. Some roots however developed both RPMs and lateral roots indicating that both structures were similar in terms of the timing and location of cell division in the pericycle and endodermis leading to their initiation. Removal of the auxin transport inhibitors allowed many of the RPMs to organize later into lateral root primordia and to emerge in clusters. When the auxin, indoleacetic acid (IAA) was added to the growth medium along with DPX-1840, 3 ranks of RPMs now in the form of fasciated lateral roots emerged from the primary root. The auxin antagonist, p-chlorophenoxy-isobutyric acid (PCIB), also induced RPM formation. In contrast to DPX-1840 treatment, the addition of IAA during PCIB treatment caused normal lateral root development. 相似文献
112.
Patricia L. Ringeling Maud I. Cleton Martin J. Kroos Lianne W. J. Sorber Wim C. de Bruyn Pauline M. Harrison Henk G. van Eijk 《Biometals》1989,2(2):114-121
Summary Cytosolic and lysosomal ferritin and haemosiderin were isolated from rat livers which had been iron-loaded by four intraperitoneal injections of iron-dextran. The cytosolic and lysosomal ferritins, prepared in a phosphate-free medium, were subjected to gel-filtration chromatography on Sepharose 613, yielding four fractions: a cytosolic monomeric (CMF) and void-volume ferritin fraction (CVVF), and a lysosomal monomeric (LMF) and void-volume ferritin fraction (LVVF). Of each fraction the following aspects were examined: (a) immunoreactivity against specific antiserum; (b) the Fe/P mass ratio and the effect of dialysis on this ratio using electron probe micro-analysis (EPMA); (c) morphology and Fespecific imaging using electron spectroscopic imaging (ESI) and electron energy loss spectroscopy (EELS). For haemosiderin one aspect, the Fe/P ratio, was determined before and after extensive purification. The following results were obtained (a) All ferritin fractions reacted with anti- (rat liver ferritin). (b) The Fe/P ratios as determined in CMF in an haemosiderin were not affected by dialysis or extensive purification, respectively. The Fe/P ratio in CWF was affected by dialysis. In the lysosomal fractions, only a trace of phosphorus (LVVF) or no phosphorus (LMF) was detected. (c) Morphologically, CMF and CVVF were found to be rather homogeneous; the iron core diameters of both fractions were in the known size range. LMF and LVVF were of rather heterogeneous composition; the core diameters of these fractions were different. In conclusion: the phosphorus in ferritin and haemosiderin is firmly bound; Haemosiderin, when derived from ferritin, has to take up phosphorus in the lysosomes. 相似文献
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114.
The yeast protein Spo20 contains a regulatory amphipathic motif that has been suggested to recognize phosphatidic acid, a lipid involved in signal transduction, lipid metabolism and membrane fusion. We have investigated the interaction of the Spo20 amphipathic motif with lipid membranes using a bioprobe strategy that consists in appending this motif to the end of a long coiled-coil, which can be coupled to a GFP reporter for visualization in cells. The resulting construct is amenable to in vitro and in vivo experiments and allows unbiased comparison between amphipathic helices of different chemistry. In vitro, the Spo20 bioprobe responded to small variations in the amount of phosphatidic acid. However, this response was not specific. The membrane binding of the probe depended on the presence of phosphatidylethanolamine and also integrated the contribution of other anionic lipids, including phosphatidylserine and phosphatidyl-inositol-(4,5)bisphosphate. Inverting the sequence of the Spo20 motif neither affected the ability of the probe to interact with anionic liposomes nor did it modify its cellular localization, making a stereo-specific mode of phosphatidic acid recognition unlikely. Nevertheless, the lipid binding properties and the cellular localization of the Spo20 alpha-helix differed markedly from that of another amphipathic motif, Amphipathic Lipid Packing Sensor (ALPS), suggesting that even in the absence of stereo specific interactions, amphipathic helices can act as subcellular membrane targeting determinants in a cellular context. 相似文献
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117.
Petit M Lim KY Julio E Poncet C Dorlhac de Borne F Kovarik A Leitch AR Grandbastien MA Mhiri C 《Molecular genetics and genomics : MGG》2007,278(1):1-15
LTR-retrotransposons contribute substantially to the structural diversity of plant genomes. Recent models of genome evolution
suggest that retrotransposon amplification is offset by removal of retrotransposon sequences, leading to a turnover of retrotransposon
populations. While bursts of amplification have been documented, it is not known whether removal of retrotransposon sequences
occurs continuously, or is triggered by specific stimuli over short evolutionary periods. In this work, we have characterized
the evolutionary dynamics of four populations of copia-type retrotransposons in allotetraploid tobacco (Nicotiana tabacum) and its two diploid progenitors Nicotiana sylvestris and Nicotiana tomentosiformis. We have used SSAP (Sequence-Specific Amplification Polymorphism) to evaluate the contribution retrotransposons have made
to the diversity of tobacco and its diploid progenitor species, to quantify the contribution each diploid progenitor has made
to tobacco's retrotransposon populations, and to estimate losses or amplifications of retrotransposon sequences subsequent
to tobacco's formation. Our results show that the tobacco genome derives from a turnover of retrotransposon sequences with
removals concomitant with new insertions. We have detected unique behaviour specific to each retrotransposon population, with
differences likely reflecting distinct evolutionary histories and activities of particular elements. Our results indicate
that the retrotransposon content of a given plant species is strongly influenced by the host evolutionary history, with periods
of rapid turnover of retrotransposon sequences stimulated by allopolyploidy. 相似文献
118.
Transient receptor potential canonical channels are required for in vitro endothelial tube formation
In endothelial cells Ca(2+) entry is an essential component of the Ca(2+) signal that takes place during processes such as cell proliferation or angiogenesis. Ca(2+) influx occurs via the store-operated Ca(2+) entry pathway, involving stromal interaction molecule-1 (STIM1) and Orai1, but also through channels gated by second messengers like the transient receptor potential canonical (TRPC) channels. The human umbilical vein-derived endothelial cell line EA.hy926 expressed STIM1 and Orai1 as well as several TRPC channels. By invalidating each of these molecules, we showed that TRPC3, TRPC4, and TRPC5 are essential for the formation of tubular structures observed after EA.hy926 cells were plated on Matrigel. On the contrary, the silencing of STIM1 or Orai1 did not prevent tubulogenesis. Soon after being plated on Matrigel, the cells displayed spontaneous Ca(2+) oscillations that were strongly reduced by treatment with siRNA against TRPC3, TRPC4, or TRPC5, but not siRNA against STIM1 or Orai1. Furthermore, we showed that cell proliferation was reduced upon siRNA treatment against TRPC3, TRPC5, and Orai1 channels, whereas the knockdown of STIM1 had no effect. On primary human umbilical vein endothelial cells, TRPC1, TRPC4, and STIM1 are involved in tube formation, whereas Orai1 has no effect. These data showed that TRPC channels are essential for in vitro tubulogenesis, both on endothelial cell line and on primary endothelial cells. 相似文献
119.
Maud Sigoillot Anne Brockhoff Wolfgang Meyerhof Lo?c Briand 《Applied microbiology and biotechnology》2012,96(3):619-630
Sweet-tasting compounds are recognized by a heterodimeric receptor composed of the taste receptor, type 1, members 2 (T1R2) and 3 (T1R3) located in the mouth. This receptor is also expressed in the gut where it is involved in intestinal absorption, metabolic regulation, and glucose homeostasis. These metabolic functions make the sweet taste receptor a potential novel therapeutic target for the treatment of obesity and related metabolic dysfunctions such as diabetes. Existing sweet taste inhibitors or blockers that are still in development would constitute promising therapeutic agents. In this review, we will summarize the current knowledge of sweet taste inhibitors, including a sweet-taste-suppressing protein named gurmarin, which is only active on rodent sweet taste receptors but not on that of humans. In addition, their potential applications as therapeutic tools are discussed. 相似文献
120.
Actin turnover-dependent fast dissociation of capping protein in the dendritic nucleation actin network: evidence of frequent filament severing 下载免费PDF全文
Miyoshi T Tsuji T Higashida C Hertzog M Fujita A Narumiya S Scita G Watanabe N 《The Journal of cell biology》2006,175(6):947-955
Actin forms the dendritic nucleation network and undergoes rapid polymerization-depolymerization cycles in lamellipodia. To elucidate the mechanism of actin disassembly, we characterized molecular kinetics of the major filament end-binding proteins Arp2/3 complex and capping protein (CP) using single-molecule speckle microscopy. We have determined the dissociation rates of Arp2/3 and CP as 0.048 and 0.58 s(-1), respectively, in lamellipodia of live XTC fibroblasts. This CP dissociation rate is three orders of magnitude faster than in vitro. CP dissociates slower from actin stress fibers than from the lamellipodial actin network, suggesting that CP dissociation correlates with actin filament dynamics. We found that jasplakinolide, an actin depolymerization inhibitor, rapidly blocked the fast CP dissociation in cells. Consistently, the coexpression of LIM kinase prolonged CP speckle lifetime in lamellipodia. These results suggest that cofilin-mediated actin disassembly triggers CP dissociation from actin filaments. We predict that filament severing and end-to-end annealing might take place fairly frequently in the dendritic nucleation actin arrays. 相似文献