Removing hairs from plant stems.
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Acetates↗
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Plant stem cells: the only constant thing is change.
Recent studies in Arabidopsis have uncovered a negative feedback loop that couples the antagonistic functions of the WUSCHEL and CLAVATA loci to control stem cell fate in the shoot apical meristem. Abundance of the CLAVATA3 protein limits signaling through this pathway.
Arabidopsis↗
Adhesion of rumen bacteria to alkali-treated plant stems.
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Animal Feed↗
[Orientation relationship of the proton resonance lines of water in plant stem capillaries].
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Electron Spin Resonance Spectroscopy↗
Plant stems: a possible model system for the transduction of mechanical information in bone modeling.
As a grass stem bends in the wind, signals at the subcellular level initiate a process of stem strengthening. The same happens in human bones. What have the two got in common?
Biomechanical Phenomena↗
[Progress in research on plant stem cell organizer gene WUSCHEL].
The WUS (WUSCHEL) gene encodes a transcription factor that specifies the adjacent cells to be stem cell. The WUS dependent signal systems have been found in different tissues recent years. The feedback loop between the CLV and WUS genes maintains the stem cell self-renewal and apical dominance in shoot apical meristem. In the embryonic meristem, the expression of CLV3 depends on WUS only. During post-embryo development, both WUS and STM are needed for CLV3 expression and the triggering of organogenesis. The expression of AG in floral meristem is activated by co-existence of WUS and LFY, AG acts as a negative regulator of WUS expression to downregulate the WUS level. The signal system established by WUS is also involved in ovule development. The somatic embryogenesis can be promoted efficiently by WUS, especially in the presence of auxin. The results of prevoius works indicated that cell competence to WUS activity is related to microenvironment and the combination of WUS signal with different environmental factors could activate different downstream genes.
Arabidopsis Proteins↗
Iron Translocation II. Citrate/Iron Ratios in Plant Stem Exudates.
Stem exudates of sunflower, soybean, cucumber, and tomato were analyzed for citrate and iron content. Generally, the lowest iron treatments given at decapitation were associated with lowest citrate levels in the exudate and intermediate treatments with the highest citrate levels. Citrate reached 6.2 x 10(-4)m in sunflower exudate. 7.3 x 10(-4)m in soybean, 9.4 x 10(-4)m in cucumber, and 1.8 x 10(-4)m in tomato. Some of these values represent a doubling or tripling of citrate when compared to the lowest ones obtained. High Fe depressed the citrate content of exudate in some cases.As iron was raised in the nutrient, the increases of iron in the exudate were proportionately greater than those of citrate. The highest Fe treatments led to exaggerated uptake of iron by sunflower. In some cases iron was translocated in molar excess of citrate. A time-response experiment with tomato showed a rapid flooding of iron into the roots but a relatively slow release of iron into xylem exudate.Similar electrophoretic patterns of iron were obtained despite changes in citrate and iron with time. Exudates from sunflower, cucumber, and tomato gave iron concentrations in the position of iron-citrate.
Journal Article↗
Signals that regulate stem cell activity during plant development.
Plant stem cells are used continuously to generate new structures during the entire life-span of the organism. In the adult plant, stem cells are found in specialized structures called meristems. The meristems contain the stem cell niche together with rapidly dividing daughter cells that will ultimately differentiate into specific cell types. Some of the master genes that orchestrate the establishment and maintenance of the stem cell niche have now been identified in both the root and the shoot. Recent results show that these genes also determine the fate of the stem cells and that feedback signals from differentiated cells are involved in stem cell specification. These advances have provided a framework to understand how short-range and long-range signals are integrated to specify and position the stem cell niche in the meristems, and how the differentiation potential of plant stem cells is controlled.
Cell Differentiation↗
Stem cells: a plant biology perspective.
A recent meeting at the Juan March Foundation in Madrid, Spain brought together plant biologists to discuss the characteristics of plant stem cells that are unique and those that are shared by stem cells from the animal kingdom.
Animals↗
Cellular mechanisms underlying growth asymmetry during stem gravitropism.
Plant stems respond to gravitropic stimulation with a rapid, local and reversible change in cell growth rate (elongation), generally on both the upper and lower sides of the stem. The cellular and biochemical mechanisms for this differential growth are reviewed. Considerable evidence implicates an asymmetry in wall pH in the growth response. The strengths and weaknesses of the wall "loosening enzyme" concept are reviewed and the possibility of expansin involvement in the bending response of stems is considered. Also discussed is the possibility that wall stiffening processes, e.g. phenolic coupling driven by oxidative bursts or altered orientation of newly deposited cellulose, might mediate the growth responses during gravitropism.
Cell Wall↗
Transport of methyl tert-butyl ether through alfalfa plants.
Concentrations measured in alfalfa plant stem segments indicated that plants grown in methyl tert-butyl ether (MTBE)-contaminated soil took up the chemical through their roots. Assuming a cylindrical shape for the plant stem, a mathematical model was developed to describe the transport of MTBE through the stems. Simulation results from uniform and nonuniform initial concentration distributions across the stem radius were compared with steady-state experimental data. With known values of plant stem radius, water usage, water content, and the distance over which the concentration decreased by 50%, the diffusion coefficient of MTBE radial transport across the plant stem was estimated with 95% confidence to be in the range of 8.43-16.2 x 10(-8) cm2/s with a mean of 1.23 x 10(-7) cm2/s. When the diffusion coefficient was calculated based on transient experimental data, the values with 95% confidence interval ranged from 4.14 x 10(-7) to 8.00 x 10(-7) cm2/s with a mean value of 6.07 x 10(-7) cm2/s. The difference between these two results can be reduced by more accurate estimation of the water flow velocity through plant stems. The model is applicable to other species including sunflowers and poplars upon substitution of appropriate parameters.
Carcinogens↗
Purification of lectins from the stems of peanut plants.
The stem of the peanut plant contains two lectins, a methyl alpha-mannoside specific lectin (SL-I) and a lactose/cellobiose specific lectin (SL-II). These lectins are found to be developmentally regulated and maximum activities are observed in 3-4-weeks-old plants. The two lectins SL-I and SL-II have been purified from 3-week-old stem by affinity chromatography on Sephadex G-50 and guar gum matrices respectively. Both are glycosylated lectins and have the identical subunit molecular weight of 31 kDa.
Arachis↗
Isolation of an effective debriding agent from the stems of pineapple plants.
The stem of the pineapple plant contains, in addition to a number of proteases, particularly bromelain, a non-proteolytic component which is responsible for the complete bridement of experimental burns by an "enzymatic dissection" between the viable native and the non-viable denatured burn tissue. With very little scraping, using a tongue depressor, all of the eschar can be removed and a bed suitable for grafting results. This "Escharase" has a molecular weight of 45,000 daltons and is a trimer made up of three identical subunits weighing 15,000 daltons each; it has an isoelectric point of pH 6.04 and has no hydrolytic enzyme activity against normal protein substrates or various glycosaminoglycan substrates. It can be concentrated by membrane ultrafiltration in a molecular weight range between 30,000 and 50,000 daltons and be purified by isoelectric focusing. The biological activity of the Escharase is not dependent on sulfhydryl groups nor upon the contaminating bromelain activity. The Escharase activity varies enormously from preparation to preparation, but the ultrafiltration procedure tends to concentrate Escharase activity to a fairly constant amount.
Animals↗
Relationship of boron to gibberellic Acid-induced proliferation in debudded tobacco plants.
Stem applications of gibberellic acid (GA) to debudded tobacco plants (Nicotiona tabacum L., var. One Sucker) produce stem swellings that involve intense proliferation of, primarily, xylem tissue. Withholding boron from GA-treated debudded plants greatly reduces the GA-induced proliferation. This response offers a system for directly demonstrating the effect of boron on xylem formation and lignification that is unconfounded by the effect of boron on elongation growth.
Journal Article↗
Isolation of cell wall proteins from Medicago sativa stems.
Plant cell walls are highly dynamic and chemically active components of plant cells. Cell walls consist primarily of polysaccharides, with proteins comprising approx 10% of the cell wall mass. These proteins are difficult to isolate with a high degree of purity from the complex carbohydrate matrix. This matrix traps proteins and is a source of contamination for subsequent 2-DE analysis. Mature plant tissues provide a further challenge owing to the formation of secondary walls that contain phenolic compounds. This chapter discusses protein extraction from cell walls and presents a specific method for the isolation of proteins from Medicago sativa stem cell walls. The method includes cell disruption by grinding, copious washes with both aqueous and organic solutions to remove cytosolic proteins and small molecule contaminants, and two different salt extractions that provide a highly enriched cell wall protein fraction from alfalfa stem cell walls. Following treatment with a commercial clean-up kit, the protein extracts yield high-quality and high-resolution 2-DE separations from which proteins can be readily identified by mass spectrometry.
Cell Fractionation↗
A C2H2-type zinc finger protein, SGR5, is involved in early events of gravitropism in Arabidopsis inflorescence stems.
Plants can sense the direction of gravity and change the growth orientation of their organs. To elucidate the molecular mechanisms of gravity perception and the signal transduction of gravitropism, we have characterized a number of shoot gravitropism (sgr) mutants of Arabidopsis. The sgr5-1 mutant shows reduced gravitropism in the inflorescence stem but its root and hypocotyl have normal gravitropism. SGR5 encodes a zinc finger protein with a coiled-coil motif. The SGR5-GFP fusion protein is localized in the nucleus of Arabidopsis protoplasts, suggesting that SGR5 may act as a transcription factor. Analysis of GUS expression under the control of the SGR5 promoter revealed that SGR5 is mainly expressed in the endodermis, the gravity-sensing tissue in inflorescence stems. Furthermore, the observation that endodermis-specific expression of SGR5 using the SCR promoter in the sgr5-1 mutant restores shoot gravitropism indicates that it could function in the gravity-sensing endodermal cell layer. In contrast to other sgr mutants reported previously, almost all amyloplasts in the endodermal cells of the sgr5-1 mutant sedimented in the direction of gravity. Taken together, our results suggest that SGR5 may be involved in an early event in shoot gravitropism such as gravity perception and/or a signaling process subsequent to amyloplast sedimentation as a putative transcription factor in gravity-perceptive cells.
Amino Acid Sequence↗
Willow growth in response to nutrients and moisture on a clay landfill cap soil. I. Growth and biomass production.
The growth and biomass production by willow (Salix viminalis L.) was studied in lysimeters containing Oxford clay landfill cap soil with different amendments, bulk densities and watering regimes. Three years from planting, stem biomass in well-watered plants was least (0.28 kg plant(-1)) with high bulk density soil (1480 kg m(-3)) and no nutritional amendment but was increased 10-fold (2.53 kg plant(-1)) by reducing soil bulk density (1200 kg m3) and adding amendments. In comparison, on a sandy loam soil it was 6.23 kg plant(-1). There were similar differences in number of stems plant(-1), stem basal area plant(-1) and plant leaf area which can be attributed to low nitrogen and phosphorus levels in Oxford clay. Water stress reduced stem biomass production by 26-37% and caused higher root:stem ratios. These were also higher on Oxford clay than on the sandy loam. Successful biomass production from willow on Oxford clay landfill caps will therefore require nutritional amendment.
Biomass↗
Characterization of a family of Arabidopsis genes related to xyloglucan fucosyltransferase1.
To understand primary cell wall assembly in Arabidopsis, we have focused on identifying and characterizing enzymes involved in xyloglucan biosynthesis. Nine genes (AtFUT2-10) were identified that share between 47% and 62% amino acid similarity with the xyloglucan-specific fucosyltransferase AtFUT1. Reverse transcriptase-PCR analysis indicates that all these genes are expressed. Bioinformatic analysis predicts that these family members are fucosyltransferases, and we first hypothesized that some may also be involved in xyloglucan biosynthesis. AtFUT3, AtFUT4, and AtFUT5 were expressed in tobacco (Nicotiana tabacum L. cv BY2) suspension culture cells, and the resulting proteins did not transfer fucose (Fuc) from GDP-Fuc to tamarind xyloglucan. AtFUT3, AtFUT4, and AtFUT5 were overexpressed in Arabidopsis plants. Leaves of plants overexpressing AtFUT4 or AtFUT5 contained more Fuc than wild-type plants. Stems of plants overexpressing AtFUT4 or AtFUT5 contained more xylose, less arabinose, and less galactose than wild-type plants. We suggest that the AtFUT family is likely to include fucosyltransferases important for the synthesis of wall carbohydrates. A targeted analysis of isolated cell wall matrix components from plants altered in expression of these proteins will help determine their specificity and biological function.
Amino Acid Sequence↗