Mechanisms of micronutrient uptake in plants

2001 ◽  
Vol 28 (7) ◽  
pp. 661 ◽  
Author(s):  
Robert J. Reid
Keyword(s):  
Plasma Membrane ◽  
Trace Metals ◽  
Plant Growth ◽  
Expression Systems ◽  
Cation Uptake ◽  
Micronutrient Uptake ◽  
Heterologous Expression Systems ◽  
Metal Micronutrients ◽  
Uptake Studies ◽  
Kinetics Of

In plants, the elements Fe, Zn, Mn, Cu, Ni, B, Mo and Cl are considered to be micronutrients essential for plant growth. Micronutrient uptake systems are intrinsically more difficult to investigate than their macronutrient counterparts because of the low fluxes involved. Currently, the mechanism of transport for these micronutrients has not been clearly identified, except for Cl. In the case of the trace metal micronutrients, uptake studies point to the presence of high and low affinity transporters with broad substrate specificity. The kinetics of these transporters is clouded by the failure of many investigators to consider the effects of the electrostatic nature of the plasma membrane on cation uptake. Recent work has helped to clarify the nature of B movement across membranes and there is now evidence of a facilitated transport system for B, in addition to its passive permeation directly through the membrane. The uptake of Mo is known to be induced by NO3 and inhibited by W, but little further information is available on how Mo enters cells. In recent years, the emphasis has shifted from physiological studies of micronutrient uptake to molecular investigations of transporters cloned in plants and characterized in heterologous expression systems. There is now a substantial catalogue of transporter genes, mostly for trace metals, whose functions in plants have yet to be clearly defined.

scholarly journals A region within the third extracellular loop of rat Aquaporin 6 precludes trafficking to plasma membrane in a heterologous cell line

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
D. C. Soler ◽  
T. Kowatz ◽  
A. E. Sloan ◽  
T. S. McCormick ◽  
K. D. Cooper ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Membrane Trafficking ◽  
Extracellular Loop ◽  
Expression Systems ◽  
Membrane Expression ◽  
Er Retention ◽  
Plasma Membrane Expression ◽  
Heterologous Expression Systems ◽  
Heterologous Cell ◽  
Retention Signal

AbstractThe inability to over-express Aquaporin 6 (AQP6) in the plasma membrane of heterologous cells has hampered efforts to further characterize the function of this aquaglyceroporin membrane protein at atomic detail using crystallographic approaches. Using an Aquaporin 3-tGFP Reporter (AGR) system we have identified a region within loop C of AQP6 that is responsible for severely hampering plasma membrane expression. Serine substitution corroborated that amino acids present within AQP6194–213 of AQP6 loop C contribute to intracellular endoplasmic reticulum (ER) retention. This intracellular retention signal may preclude proper plasma membrane trafficking and severely curtail expression of AQP6 in heterologous expression systems.

Agrobacteium Transformation of Tobacco with a Genetic Module of Antimalarial Agent Artemisinin Biosynthesis

2020 ◽  
Vol 36 (3) ◽  
pp. 34-45
Author(s):  
T.Yu. Mitiuchkina ◽  
A.S. Pushin ◽  
A.K. Tzareva ◽  
A.M. Vainstein ◽  
S.V. Dolgov
Keyword(s):  
Target Genes ◽  
Artemisia Annua ◽  
Biosynthesis Pathway ◽  
Expression Systems ◽  
Heterologous Host ◽  
Russian Science ◽  
Tobacco Plants ◽  
Genetic Module ◽  
Heterologous Expression Systems ◽  
Artemisinin Biosynthesis

Artemisinin-based medicines are the most effective treatment for malaria. To date, the wormwood plants (Artemisia annua L.) are the main source of artemisinin. Due to the limited nature of this source, considerable efforts are directed towards the development of methods for artemisinin production via heterologous expression systems. We used in this study agrobacterial transformation to transfer the genetic module of the artemisinin biosynthesis pathway into plants and then analyzed its transcription in a heterologous host. Tobacco plants were transformed with the artemisinin biosynthesis genes encoding amorpha-4,11-diene synthase, artemisin-aldehyde All(13) reductase, amorpha-4,11-diene monooxygenase, cytochrome P450 reductase from A. annua and yeast 3-hydroxy-3-methylglutaryl-coenzyme A reductase cloned in the pArtemC vector; farnesyl diphosphate synthase and aldehyde dehydrogenase were used to transform the plants as parts of vector p2356. As a result of transformation with the pArtemC and p2356 vectors, in twos transgenic lines with all target genes were obtained. Five genes of artemisinin biosynthesis and two genes of biosynthesis of its precursors were successfully transferred into the genome of transgenic tobacco lines as a result of the co-transformation with abovementioned vectors. Thus, the entire artemisinin biosynthesis pathway was first reconstructed in heterologous plants: the transcription of the artemisinin biosynthesis genes in the tobacco plants was shown via RT-PCR. The obtained results will be used in further research on expression systems for the production of artemisinin and other non-protein substances in heterologous host plants. artemisinin, malaria, metabolic engineering, tobacco, transgenic plants This work was supported by a Grant from the Russian Science Foundation no. 19-14-00190.

Kv3.1–Kv3.2 Channels Underlie a High-Voltage–Activating Component of the Delayed Rectifier K+ Current in Projecting Neurons From the Globus Pallidus

1999 ◽  
Vol 82 (3) ◽  
pp. 1512-1528 ◽  
Author(s):  
R. Hernández-Pineda ◽  
A. Chow ◽  
Y. Amarillo ◽  
H. Moreno ◽  
M. Saganich ◽  
...  
Keyword(s):  
Heterologous Expression ◽  
Globus Pallidus ◽  
High Frequency ◽  
Calcium Binding ◽  
Repetitive Firing ◽  
Delayed Rectifier ◽  
Expression Systems ◽  
Electrophysiological Properties ◽  
Channel Proteins ◽  
Heterologous Expression Systems

The globus pallidus plays central roles in the basal ganglia circuitry involved in movement control as well as in cognitive and emotional functions. There is therefore great interest in the anatomic and electrophysiological characterization of this nucleus. Most pallidal neurons are GABAergic projecting cells, a large fraction of which express the calcium binding protein parvalbumin (PV). Here we show that PV-containing pallidal neurons coexpress Kv3.1 and Kv3.2 K+ channel proteins and that both Kv3.1 and Kv3.2 antibodies coprecipitate both channel proteins from pallidal membrane extracts solubilized with nondenaturing detergents, suggesting that the two channel subunits are forming heteromeric channels. Kv3.1 and Kv3.2 channels have several unusual electrophysiological properties when expressed in heterologous expression systems and are thought to play special roles in neuronal excitability including facilitating sustained high-frequency firing in fast-spiking neurons such as interneurons in the cortex and the hippocampus. Electrophysiological analysis of freshly dissociated pallidal neurons demonstrates that these cells have a current that is nearly identical to the currents expressed by Kv3.1 and Kv3.2 proteins in heterologous expression systems, including activation at very depolarized membrane potentials (more positive than −10 mV) and very fast deactivation rates. These results suggest that the electrophysiological properties of native channels containing Kv3.1 and Kv3.2 proteins in pallidal neurons are not significantly affected by factors such as associated subunits or postranslational modifications that result in channels having different properties in heterologous expression systems and native neurons. Most neurons in the globus pallidus have been reported to fire sustained trains of action potentials at high-frequency. Kv3.1–Kv3.2 voltage-gated K+channels may play a role in helping maintain sustained high-frequency repetitive firing as they probably do in other neurons.

scholarly journals Albumin binding of unconjugated [3H]bilirubin and its uptake by rat liver basolateral plasma membrane vesicles

1996 ◽  
Vol 316 (3) ◽  
pp. 999-1004 ◽  
Author(s):  
Lorella PASCOLO ◽  
Savino DEL VECCHIO ◽  
Ronald K. KOEHLER ◽  
J. Enrique BAYON ◽  
Cecile C. WEBSTER ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Rat Liver ◽  
Basolateral Membrane ◽  
Membrane Vesicles ◽  
Plasma Membrane Vesicles ◽  
Experimental Conditions ◽  
Saturation Kinetics ◽  
Basolateral Plasma Membrane ◽  
Component C ◽  
Uptake Studies

Using highly purified unconjugated [3H]bilirubin (UCB), we measured UCB binding to delipidated human serum albumin (HSA) and its uptake by basolateral rat liver plasma membrane vesicles, in both the absence and presence of an inside-positive membrane potential. Free UCB concentrations ([Bf]) were calculated from UCB–HSA affinity constants (K´f), determined by five cycles of ultrafiltration through a Centricon-10 device (Amicon) of the same solutions used in the uptake studies. At HSA concentrations from 12 to 380 μM, K´f (litre/mol) was inversely related to [HSA], irrespective of the [Bt]/[HSA] ratio. K´f was 2.066×106+(3.258×108/[HSA]). When 50 mM KCl was iso-osmotically substituted for sucrose, the K´f value was significantly lower {2.077×106+(1.099×108/[HSA])}. The transport occurred into an osmotic-sensitive space. Below saturation ([Bf] ⩽ 65 nM), both electroneutral and electrogenic components followed saturation kinetics with respect to [Bf], with Km values of 28±7 and 57±8 nM respectively (mean±S.D., n = 3, P < 0.001). The Vmax was greater for the electrogenic than for the electroneutral component (112±12 versus 45±4 pmol of UCB·mg-1 of protein·15 s-1, P < 0.001). Sulphobromophthalein trans-stimulated both electrogenic (61%) and electroneutral (72%) UCB uptake. These data indicate that: (a) as [HSA] increases, K´f decreases, thus increasing the concentration of free UCB. This may account for much of the enhanced hepatocytic uptake of organic anions observed with increasing [HSA]. (b) UCB is taken up at the basolateral membrane of the hepatocyte by two systems with Km values within the range of physiological free UCB levels in plasma. The electrogenic component shows a lower affinity and a higher capacity than the electroneutral component. (c) It is important to calculate the actual [Bf] using a K´f value determined under the same experimental conditions (medium and [HSA]) used for the uptake studies.

The use of bioluminescence as a reporter to study the adherence of the plant growth promoting rhizopseudomonads 7NSK2 and ANP15 to canola roots

1993 ◽  
Vol 39 (3) ◽  
pp. 329-334 ◽  
Author(s):  
J. Boelens ◽  
D. Zoutman ◽  
J. Campbell ◽  
W. Verstraete ◽  
W. Paranchych
Keyword(s):  
Plant Growth ◽  
Freundlich Isotherm ◽  
Root Surface ◽  
Broad Host Range ◽  
Bacterial Bioluminescence ◽  
Range Vector ◽  
Plant Growth Promoting ◽  
Specific Receptors ◽  
Growth Promoting ◽  
Kinetics Of

The adherence of the plant growth promoting rhizopseudomonads Pseudomonas aeruginosa 7NSK2 and Pseudomonas fluorescens ANP15 to canola roots (Brassica campestris L. c.v. Tobin) was examined by means of a bacterial bioluminescence system. The bioluminescence broad host range vector pDLUX-I was constructed from pLAFR-I and the lux A–E genes of Vibrio fischerii. This vector was conjugally transferred into the plant growth promoting rhizopseudomonads 7NSK2 and ANP15. The transformed strains were constitutively bioluminescent at an optimal temperature of 21 °C. The measured bioluminescence was directly proportional to the density of the bacteria in suspension and was the same for both planktonic and sessile bacteria adhering to the root surface. The adherence of the plant growth promoting rhizopseudomonads was proportional to the density of the bacterial inoculum, approached saturation at 60 min, and was reversible. The kinetics of the microbial adhesion was described by a Freundlich isotherm suggesting that the adherence of the bacteria to the canola root surface does not involve specific receptors. We conclude that the pDLUX-I vector is an easy and accurate way to study the kinetics of microbial adherence to the rhizoplane.Key words: rhizopseudomonads, bioluminescence, adhesion, plant growth promotion.not available

scholarly journals Insulin Stimulates Membrane Fusion and GLUT4 Accumulation in Clathrin Coats on Adipocyte Plasma Membranes

2007 ◽  
Vol 27 (9) ◽  
pp. 3456-3469 ◽  
Author(s):  
Shaohui Huang ◽  
Larry M. Lifshitz ◽  
Christine Jones ◽  
Karl D. Bellve ◽  
Clive Standley ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Membrane Fusion ◽  
Insulin Signaling ◽  
Plasma Membranes ◽  
Glucose Transporter ◽  
Fluorescent Protein ◽  
Fluorescent Proteins ◽  
Tirf Microscopy ◽  
Adipocyte Plasma Membranes ◽  
Kinetics Of

ABSTRACT Total internal reflection fluorescence (TIRF) microscopy reveals highly mobile structures containing enhanced green fluorescent protein-tagged glucose transporter 4 (GLUT4) within a zone about 100 nm beneath the plasma membrane of 3T3-L1 adipocytes. We developed a computer program (Fusion Assistant) that enables direct analysis of the docking/fusion kinetics of hundreds of exocytic fusion events. Insulin stimulation increases the fusion frequency of exocytic GLUT4 vesicles by ∼4-fold, increasing GLUT4 content in the plasma membrane. Remarkably, insulin signaling modulates the kinetics of the fusion process, decreasing the vesicle tethering/docking duration prior to membrane fusion. In contrast, the kinetics of GLUT4 molecules spreading out in the plasma membrane from exocytic fusion sites is unchanged by insulin. As GLUT4 accumulates in the plasma membrane, it is also immobilized in punctate structures on the cell surface. A previous report suggested these structures are exocytic fusion sites (Lizunov et al., J. Cell Biol. 169:481-489, 2005). However, two-color TIRF microscopy using fluorescent proteins fused to clathrin light chain or GLUT4 reveals these structures are clathrin-coated patches. Taken together, these data show that insulin signaling accelerates the transition from docking of GLUT4-containing vesicles to their fusion with the plasma membrane and promotes GLUT4 accumulation in clathrin-based endocytic structures on the plasma membrane.

The effects of acetylcholine and atropine on the 22Na+ permeability of intestinal smooth muscle vesicles

1978 ◽  
Vol 56 (6) ◽  
pp. 921-925
Author(s):  
L. Spero
Keyword(s):  
Smooth Muscle ◽  
Plasma Membrane ◽  
Membrane Vesicles ◽  
Intestinal Smooth Muscle ◽  
Erythrocyte Ghosts ◽  
Muscarinic Agonists ◽  
Plasma Membrane Vesicles ◽  
Muscle Plasma Membrane ◽  
Whole Muscle ◽  
Kinetics Of

A technique is described which has enabled us to measure changes in 22Na+ efflux from smooth muscle plasma membrane vesicles. The resting 22Na+ efflux from these sealed vesicles showed a concentration-dependent increase in response to acetylcholine and other muscarinic agonists, in similar concentrations to those which increased 42K+ efflux in whole muscle. The kinetics of this efflux were complex and could not be described by less than three exponential processes. The response to agonists has, therefore, been characterized by measurement of the half-life of 22Na+ efflux (t1/2). The acetylcholine effect was inhibited by atropine, but unlike the situation in the whole muscle, this inhibition was noncompetitive. Tubocuraine (a nicotinic antagonist) had no effect on this acetylcholine response. Atropine has no effect by itself on the resting 22Na+ efflux, neither did tetrodotoxin or ouabain. 22Na+ efflux from erythrocyte ghosts and liposomes, prepared from lipid extracts of the smooth muscle plasma membrane, was not modified by acetylcholine or atropine.

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