Phosphate absorption by Arabidopsis thaliana: interactions between phosphorus status and inhibition by arsenate.

2000 ◽  
Vol 27 (10) ◽  
pp. 959 ◽  
Author(s):  
Gregory T. Clark ◽  
James Dunlop ◽  
H. Thai Phung
Keyword(s):  
Arabidopsis Thaliana ◽  
Kinetic Analysis ◽  
Maximum Velocity ◽  
Michaelis Constant ◽  
Absorption Mechanism ◽  
Influx Rate ◽  
Phosphorus Status ◽  
High Level ◽  
Phosphate Influx ◽  
Simultaneous Elimination

The effects of phosphorus status and arsenate on the absorption of phosphate by roots of intact sterile seedlings of Arabidopsis thaliana were studied by analysing the rate of depletion of phosphate from solutions initially containing 10 M KH2PO4. Depletion of phosphate from the experimental solutions was measured both chemically and by labelling with 32P. There was a substantial efflux of phosphate coincident with a rapid influx of phosphate, with efflux increasing with increasing phosphorus status. The highest rates of absorption were obtained for the plants initially grown with a high level of phosphorus but then deprived of phosphate for 5 d prior to the experiments, with the next highest rates obtained for the most phosphorus-deficient plants. Kinetic analysis suggests that changes in both the affinity and capacity of the absorption mechanism contribute to differences in the rate of phosphate influx between plants of different phosphorus status. Arsenate as 20 M KH2AsO4 inhibited phosphate influx in a manner such that all plants, regardless of their phosphorus status, had the same phosphate influx rate. This was reflected in identical values for the Michaelis constant, Km, and maximum velocity as used in Michaelis–Menten kinetics, Vmax. Arsenate had its greatest effect on phosphate movement to the shoot. The simultaneous elimination of differences in phosphate influx between plants of different phosphorus status suggest that phosphate movement to the shoot may be important in the regulation of influx by phosphorus status.

scholarly journals Analysis on the Evolution and Microphysical Characteristics of Two Consecutive Hailstorms in Spring in Yunnan, China

Atmosphere ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 63
Author(s):  
Sidou Zhang ◽  
Shiyin Liu ◽  
Tengfei Zhang
Keyword(s):  
Wind Speed ◽  
Cloud Model ◽  
Global Analysis ◽  
Maximum Velocity ◽  
Western Pacific Subtropical High ◽  
Convective Cloud ◽  
Radar Data ◽  
Reanalysis Data ◽  
Cloud Water ◽  
High Level

By using products of the cloud model, National Centers for Environmental Prediction (NCEP) Final Operational Global Analysis (FNL) reanalysis data, and Doppler weather radar data, the mesoscale characteristics, microphysical structure, and mechanism of two hail cloud systems which occurred successively within 24 h in southeastern Yunnan have been analyzed. The results show that under the influence of two southwest jets in front of the south branch trough (SBT) and the periphery of the western Pacific subtropical high (WPSH), the northeast-southwest banded echoes affect the southeastern Yunnan of China twice. Meanwhile, the local mesoscale radial wind convergence and uneven wind speed lead to the intense development of convective echoes and the occurrence of hail. The simulated convective cloud bands are similar to the observation. The high-level mesoscale convergence line leads to the development of convective cloud bands. The low-level wind direction or wind speed convergence and the high-level wind speed divergence form a deep tilted updraft, with the maximum velocity of 15 m·s−1 at the −40~−10 °C layer, resulting in the intense development of local convective clouds. The hail embryos form through the conversion or collision growth of cloud water and snowflakes and have little to do with rain and ice crystals. Abundant cloud water, especially the accumulation region of high supercooled water (cloud water) near the 0 °C layer, is the key to the formation of hail embryos, in which qc is up to 1.92 g·kg−1 at the −4~−2 °C layer. The hail embryos mainly grow by collision-coalescence (collision-freezing) with cloud water (supercooled cloud drops) and snow crystal riming.

scholarly journals High level expression of transgenes by use of 5^|^#8242;-untranslated region of the Arabidopsis thaliana arabinogalactan-protein 21 gene in dicotyledons

2012 ◽  
Vol 29 (3) ◽  
pp. 319-322 ◽  
Author(s):  
Takeshi Matsui ◽  
Hideyuki Matsuura ◽  
Kazutoshi Sawada ◽  
Eiji Takita ◽  
Satoko Kinjo ◽  
...  
Keyword(s):  
Arabidopsis Thaliana ◽  
Untranslated Region ◽  
Arabinogalactan Protein ◽  
High Level Expression ◽  
High Level

scholarly journals Conserved and Opposite Transcriptome Patterns during Germination in Hordeum vulgare and Arabidopsis thaliana

2020 ◽  
Vol 21 (19) ◽  
pp. 7404
Author(s):  
Yanqiao Zhu ◽  
Oliver Berkowitz ◽  
Jennifer Selinski ◽  
Andreas Hartmann ◽  
Reena Narsai ◽  
...  
Keyword(s):  
Arabidopsis Thaliana ◽  
Hordeum Vulgare ◽  
Mitochondrial Biogenesis ◽  
Expression Patterns ◽  
Tca Cycle ◽  
Transcript Abundance ◽  
Pentatricopeptide Repeat ◽  
Orthologous Genes ◽  
Regulatory Processes ◽  
High Level

Seed germination is a critical process for completion of the plant life cycle and for global food production. Comparing the germination transcriptomes of barley (Hordeum vulgare) to Arabidopsis thaliana revealed the overall pattern was conserved in terms of functional gene ontology; however, many oppositely responsive orthologous genes were identified. Conserved processes included a set of approximately 6000 genes that peaked early in germination and were enriched in processes associated with RNA metabolism, e.g., pentatricopeptide repeat (PPR)-containing proteins. Comparison of orthologous genes revealed more than 3000 orthogroups containing almost 4000 genes that displayed similar expression patterns including functions associated with mitochondrial tricarboxylic acid (TCA) cycle, carbohydrate and RNA/DNA metabolism, autophagy, protein modifications, and organellar function. Biochemical and proteomic analyses indicated mitochondrial biogenesis occurred early in germination, but detailed analyses revealed the timing involved in mitochondrial biogenesis may vary between species. More than 1800 orthogroups representing 2000 genes displayed opposite patterns in transcript abundance, representing functions of energy (carbohydrate) metabolism, photosynthesis, protein synthesis and degradation, and gene regulation. Differences in expression of basic-leucine zippers (bZIPs) and Apetala 2 (AP2)/ethylene-responsive element binding proteins (EREBPs) point to differences in regulatory processes at a high level, which provide opportunities to modify processes in order to enhance grain quality, germination, and storage as needed for different uses.

The COP9 signalosome influences the epigenetic landscape of Arabidopsis thaliana

2018 ◽  
Vol 35 (16) ◽  
pp. 2718-2723 ◽  
Author(s):  
Tamir Tuller ◽  
Alon Diament ◽  
Avital Yahalom ◽  
Assaf Zemach ◽  
Shimshi Atar ◽  
...  
Keyword(s):  
Gene Expression ◽  
Dna Methylation ◽  
Arabidopsis Thaliana ◽  
Gene Expression Regulation ◽  
Developmental Pathways ◽  
Cop9 Signalosome ◽  
Supplementary Information ◽  
Loss Of Function ◽  
Genome Wide ◽  
High Level

Abstract Motivation The COP9 signalosome is a highly conserved multi-protein complex consisting of eight subunits, which influences key developmental pathways through its regulation of protein stability and transcription. In Arabidopsis thaliana, mutations in the COP9 signalosome exhibit a number of diverse pleiotropic phenotypes. Total or partial loss of COP9 signalosome function in Arabidopsis leads to misregulation of a number of genes involved in DNA methylation, suggesting that part of the pleiotropic phenotype is due to global effects on DNA methylation. Results We determined and analyzed the methylomes and transcriptomes of both partial- and total-loss-of-function Arabidopsis mutants of the COP9 signalosome. Our results support the hypothesis that the COP9 signalosome has a global genome-wide effect on methylation and that this effect is at least partially encoded in the DNA. Our analyses suggest that COP9 signalosome-dependent methylation is related to gene expression regulation in various ways. Differentially methylated regions tend to be closer in the 3D conformation of the genome to differentially expressed genes. These results suggest that the COP9 signalosome has a more comprehensive effect on gene expression than thought before, and this is partially related to regulation of methylation. The high level of COP9 signalosome conservation among eukaryotes may also suggest that COP9 signalosome regulates methylation not only in plants but also in other eukaryotes, including humans. Supplementary information Supplementary data are available at Bioinformatics online.

Mechanisms of potassium transfer across the dually perfused rat placenta

1993 ◽  
Vol 265 (2) ◽  
pp. R341-R347 ◽  
Author(s):  
T. Mohammed ◽  
J. Stulc ◽  
J. D. Glazier ◽  
R. D. Boyd ◽  
C. P. Sibley
Keyword(s):  
Diffusion Coefficient ◽  
Maximum Velocity ◽  
T Test ◽  
Michaelis Constant ◽  
Diffusion Limited ◽  
51Cr Edta ◽  
The Asymmetry ◽  
Paired T Test

The purpose of this study was to directly investigate the mechanisms of K+ transfer across the rat placenta, which was isolated and perfused through both its maternal and fetal circulations. Unidirectional maternofetal (Kmf) and fetomaternal (Kfm) clearances for 42K, 51Cr-labeled EDTA (used as a diffusion-limited paracellular marker), and 3H2O (used as a flow-limited marker) were respectively 232 +/- 36, 12 +/- 4, and 1,020 +/- 260 (mf) and 96 +/- 26, 18 +/- 6, and 737 +/- 176 (fm) microliters.min-1 x g placenta-1. Calculated K+ fluxes were asymmetric, being 0.75 +/- 0.12 and 0.41 +/- 0.12 mumol.min-1 x g placenta-1 for maternofetal and fetomaternal, respectively (mean +/- SE, n = 6; P < 0.01, paired t test). Although Kmf for 3H2O was 28% higher than Kfm, this could not completely account for the asymmetry in K+ fluxes. Kmf for 42K was 12-70 times higher than that for 51Cr-EDTA (presumed to be a paracellular marker), although its diffusion coefficient is only 2.5 times higher. An apparent Michaelis constant (Km) of 11.0 +/- 2.4 mM and maximum velocity (Vmax) of 3.8 +/- 0.33 mumol.min-1 x g placenta-1 was calculated by Michaelis-Menten analysis of the transcellular component of maternofetal flux (Jmf) for K+. Ouabain or barium (1 mM in maternal and fetal perfusate) reduced Kmf for 42K from 250 +/- 38 to 76 +/- 13 microliters.min-1 x g placenta-1 (n = 4; P < 0.01) and from 358 +/- 31 to 106 +/- 18 microliters.min-1 x g placenta-1 (n = 5; P < 0.001). Neither drug had any effect on Kmf for 51Cr-EDTA or 3H2O.(ABSTRACT TRUNCATED AT 250 WORDS)

Copper transport and kinetics in cultured C6 rat glioma cells

1995 ◽  
Vol 269 (4) ◽  
pp. C892-C898 ◽  
Author(s):  
Y. Qian ◽  
E. Tiffany-Castiglioni ◽  
E. D. Harris
Keyword(s):  
Membrane Fraction ◽  
Glioma Cells ◽  
Maximum Velocity ◽  
C6 Cells ◽  
Michaelis Constant ◽  
Rat Glioma ◽  
Saturation Kinetics ◽  
Efflux Mechanism ◽  
Import And Export ◽  
P Type

C6 rat glioma cells accumulate and efflux 67Cu. Both processes showed saturation kinetics with increasing 67Cu concentration. The Michaelis constant (Km) for uptake was 0.63 +/- 0.14 microM; maximum velocity (Vmax) was 3.29 +/- 0.57 pmol Cu.mg protein-1.min-1. The Km for efflux was 0.15 +/- 0.06 microM; Vmax was 1.08 +/- 0.71 pmol Cu.mg protein-1.min-1. p-Chloromercuribenzoate (p-CMB) totally blocked 67Cu efflux but had no effect on Km or Vmax of uptake. Total 67Cu in the cell after 50 min was partitioned equally between particulate and soluble fractions. p-CMB-treated cells accumulated more 67Cu, but < 10% was bound to the particulate (membrane) fraction. Pb also increased 67Cu accumulation without affecting Km and Vmax of 67Cu uptake. These data suggest that carriers for import and export of Cu in C6 cells are distinct or operate in two different cellular environments. Efflux is a sulfhydryl-dependent process subject to inhibition by Pb. The data are consistent with a P-type ATPase in the efflux of Cu from cells and the potential for Pb to inhibit the efflux mechanism.

scholarly journals Kinetic Analysis ofArabidopsisPhospholipase Dδ

2002 ◽  
Vol 277 (51) ◽  
pp. 49685-49690 ◽  
Author(s):  
Chunbo Qin ◽  
Cunxi Wang ◽  
Xuemin Wang
Keyword(s):  
Kinetic Analysis ◽  
Mixed Micelles ◽  
Surface Concentration ◽  
Molar Ratio ◽  
Regulation Mechanism ◽  
Michaelis Constant ◽  
Cellular Processes ◽  
Maximal Activation ◽  
Triton X ◽  
Micelle Surface

Phospholipase D (PLD) is a major plant phospholipase family involved in many cellular processes such as signal transduction, membrane remodeling, and lipid degradation. Five classes of PLDs have been identified inArabidopsis thaliana, and Ca2+and polyphosphoinositides have been suggested as key regulators for these enzymes. To investigate the catalysis and regulation mechanism of individual PLDs, surface-dilution kinetics studies were carried out on the newly identified PLDδ fromArabidopsis. PLDδ activity was dependent on both bulk concentration and surface concentration of substrate phospholipids in the Triton X-100/phospholipid mixed micelles.Vmax,KsA, andKmBvalues for PLDδ toward phosphatidylcholine or phosphatidylethanolamine were determined; phosphatidylethanolamine was the preferred substrate. PLDδ activity was stimulated greatly by phosphatidylinositol 4,5-bisphosphate (PIP2). Maximal activation was observed at a PIP2molar ratio around 0.01. Kinetic analysis indicates that PIP2activates PLD by promoting substrate binding to the enzyme, without altering the bulk binding of the enzyme to the micelle surface. Ca2+is required for PLDδ activity, and it significantly decreased the interfacial Michaelis constantKmB. This indicates that Ca2+activates PLD by promoting the binding of phospholipid substrate to the catalytic site of the enzyme.

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