scholarly journals Electrophysiological characterization of AtAMT1;4, an extraordinarily high affinity ammonium transporter from Arabidopsis thaliana

2019 ◽  
Author(s):  
Nino Bindel ◽  
Benjamin Neuhäuser
Keyword(s):  
Arabidopsis Thaliana ◽  
Pollen Tube ◽  
Pollen Grains ◽  
Transport Proteins ◽  
Ammonium Transporter ◽  
High Affinity ◽  
Electrode Voltage ◽  
Electrophysiological Characterization ◽  
Unique Expression Pattern

In plants high affinity transport proteins mediate the essential transport of ammonium across membranes. In Arabidopsis thaliana six of these AMmonium Transporters (AMTs) are encoded on the genome. All of these show a unique expression pattern. While most AMTs are highly expressed in the root, AtAMT1;4 expression is limited to the pollen grains and the pollen tube. Here, we addressed the transport characteristics of AtAMT1;4 in the heterologous Xenopus laevis oocytes system. Two electrode voltage clamp measurements tagged AtAMT1;4 as an electrogenic high affinity ammonium transporter. The transport was saturable and showed extraordinarily high affinity for ammonium with a Km value lower than 10 µM.

scholarly journals High-affinity ammonium transport by Arabidopsis thaliana AMT1;4

2021 ◽  
Vol 43 (4) ◽  
Author(s):  
Nino Bindel ◽  
Benjamin Neuhäuser
Keyword(s):  
Arabidopsis Thaliana ◽  
Xenopus Laevis ◽  
Pollen Tube ◽  
Pollen Grains ◽  
Transport Proteins ◽  
Ammonium Transporter ◽  
Ammonium Transport ◽  
High Affinity ◽  
Ammonium Transporters ◽  
Unique Expression Pattern

AbstractIn plants high affinity transport proteins mediate the essential transport of ammonium across membranes. In Arabidopsis thaliana six of these AMmonium Transporters (AMTs) are encoded by the genome. All of them show a unique expression pattern. While most AMTs are highly expressed in the root, AtAMT1;4 expression is limited to the pollen grains and the pollen tube. Here, we addressed the transport characteristics of AtAMT1;4 in the heterologous Xenopus laevis oocytes system. The transport saturated and showed high affinity for ammonium with a Km value lower than 10 µM. Based on our electrophysiological analysis, we classified AtAMT1;4 as a high affinity ammonium transporter.

scholarly journals Two Expansin Genes, AtEXPA4 and AtEXPB5, Are Redundantly Required for Pollen Tube Growth and AtEXPA4 Is Involved in Primary Root Elongation in Arabidopsis thaliana

Genes ◽  
2021 ◽  
Vol 12 (2) ◽  
pp. 249
Author(s):  
Weimiao Liu ◽  
Liai Xu ◽  
Hui Lin ◽  
Jiashu Cao
Keyword(s):  
Arabidopsis Thaliana ◽  
Pollen Tube ◽  
Pollen Tube Growth ◽  
Cell Walls ◽  
Root Elongation ◽  
Expression Patterns ◽  
Primary Root ◽  
Pollen Grains ◽  
Tube Growth ◽  
Cell Wall Binding

The growth of plant cells is inseparable from relaxation and expansion of cell walls. Expansins are a class of cell wall binding proteins, which play important roles in the relaxation of cell walls. Although there are many members in expansin gene family, the functions of most expansin genes in plant growth and development are still poorly understood. In this study, the functions of two expansin genes, AtEXPA4 and AtEXPB5 were characterized in Arabidopsis thaliana. AtEXPA4 and AtEXPB5 displayed consistent expression patterns in mature pollen grains and pollen tubes, but AtEXPA4 also showed a high expression level in primary roots. Two single mutants, atexpa4 and atexpb5, showed normal reproductive development, whereas atexpa4atexpb5 double mutant was defective in pollen tube growth. Moreover, AtEXPA4 overexpression enhanced primary root elongation, on the contrary, knocking out AtEXPA4 made the growth of primary root slower. Our results indicated that AtEXPA4 and AtEXPB5 were redundantly involved in pollen tube growth and AtEXPA4 was required for primary root elongation.

Electrophysiological Characterization of Membrane Transport Proteins

2013 ◽  
Vol 42 (1) ◽  
pp. 95-120 ◽  
Author(s):  
Christof Grewer ◽  
Armanda Gameiro ◽  
Thomas Mager ◽  
Klaus Fendler
Keyword(s):  
Membrane Transport ◽  
Transport Proteins ◽  
Membrane Transport Proteins ◽  
Electrophysiological Characterization

scholarly journals Calcium Current Activated by Depletion of Calcium Stores in Xenopus Oocytes

1997 ◽  
Vol 109 (6) ◽  
pp. 703-715 ◽  
Author(s):  
Yong Yao ◽  
Roger Y. Tsien
Keyword(s):  
Xenopus Oocytes ◽  
Voltage Dependence ◽  
Calcium Stores ◽  
Kinase C ◽  
Electrode Voltage ◽  
Activation Mechanisms ◽  
Electrophysiological Characterization ◽  
Inwardly Rectifying ◽  
A Current

Ca2+ currents activated by depletion of Ca2+ stores in Xenopus oocytes were studied with a two-electrode voltage clamp. Buffering of cytosolic Ca2+ with EGTA and MeBAPTA abolished ICl(Ca) and unmasked a current in oocytes that was activated by InsP3 or ionomycin in minutes and by thapsigargin or the chelators themselves over hours. At −60 mV in 10 mM extracellular CaCl2, the current was typically around −90 or −160 nA in oocytes loaded with EGTA or MeBAPTA, respectively. This current was judged to be a Ca2+-selective current for the following reasons: (a) it was inwardly rectifying and reversed at membrane potentials usually more positive than +40 mV; (b) it was dependent on extracellular [CaCl2] with Km = 11.5 mM; (c) it was highly selective for Ca2+ against monovalent cations Na+ and K+, because replacing Na+ and K+ by N-methyl-d-glucammonium did not reduce the amplitude or voltage dependence of the current significantly; and (d) Ca2+, Sr2+, and Ba2+ currents had similar instantaneous conductances, but Sr2+ and Ba2+ currents appeared to inactivate more strongly than Ca2+. This Ca2+ current was blocked by metal ions with the following potency sequence: Mg2+ << Ni2+ ≈ Co2+ ≈ Mn2+ < Cd2+ << Zn2+ << La3+. It was also inhibited by niflumic acid, which is commonly used to block ICl(Ca). PMA partially inhibited the Ca2+ current, and this effect was mostly abolished by calphostin C, indicating that the Ca2+ current is sensitive to protein kinase C. These results are the first detailed electrophysiological characterization of depletion-activated Ca2+ current in nondialyzed cells. Because exogenous molecules and channels are easy to introduce into oocytes and the distortions in measuring ICl(Ca) can now be bypassed, oocytes are now a superior system in which to analyze the activation mechanisms of capacitative Ca2+ influx.

Isolation and characterization of a high-affinity ammonium transporter ApAMT1;1 in alligatorweed

2019 ◽  
Vol 89 (3) ◽  
pp. 321-330 ◽  
Author(s):  
Xiaotong Guo ◽  
Yuting Sheng ◽  
Shunying Yang ◽  
Lei Han ◽  
Yachao Gao ◽  
...  
Keyword(s):  
Ammonium Transporter ◽  
High Affinity ◽  
Isolation And Characterization

scholarly journals Characterization of the high-affinity phosphate transporter PHT1;4 gene promoter of Arabidopsis thaliana in transgenic wheat

2017 ◽  
Vol 61 (3) ◽  
pp. 453-462 ◽  
Author(s):  
E. Penaloza ◽  
M. Santiago ◽  
S. Cabrera ◽  
G. Munoz ◽  
L. J. Corcuera ◽  
...  
Keyword(s):  
Arabidopsis Thaliana ◽  
Gene Promoter ◽  
Transgenic Wheat ◽  
Phosphate Transporter ◽  
High Affinity

scholarly journals Five Gametophytic Mutations Affecting Pollen Development and Pollen Tube Growth in Arabidopsis thaliana

Genetics ◽  
2001 ◽  
Vol 158 (4) ◽  
pp. 1773-1783 ◽  
Author(s):  
Antonia Procissi ◽  
Solveig de Laissardière ◽  
Madina Férault ◽  
Daniel Vezon ◽  
Georges Pelletier ◽  
...  
Keyword(s):  
Arabidopsis Thaliana ◽  
Pollen Tube ◽  
Pollen Tube Growth ◽  
Pollen Development ◽  
Male Gametophyte ◽  
Pollen Grains ◽  
Segregation Ratio ◽  
Variable Number ◽  
Tube Growth ◽  
Mutant Lines

Abstract Mutant analysis represents one of the most reliable approaches to identifying genes involved in plant development. The screening of the Versailles collection of Arabidopsis thaliana T-DNA insertion transformants has allowed us to isolate different mutations affecting male gametophytic functions and viability. Among several mutated lines, five have been extensively studied at the genetic, molecular, and cytological levels. For each mutant, several generations of selfing and outcrossing have been carried out, leading to the conclusion that all these mutations are tagged and affect only the male gametophyte. However, only one out of the five mutations is completely penetrant. A variable number of T-DNA copies has integrated in the mutant lines, although all segregate at one mutated locus. Two mutants could be defined as “early mutants”: the mutated genes are presumably expressed during pollen grain maturation and their alteration leads to the production of nonfunctional pollen grains. Two other mutants could be defined as “late mutant” since their pollen is able to germinate but pollen tube growth is highly disturbed. Screening for segregation ratio distortions followed by thorough genetic analysis proved to be a powerful tool for identifying gametophytic mutations of all phases of pollen development.

Cloning and functional characterization of a high-affinity Na+/dicarboxylate cotransporter from mouse brain

2001 ◽  
Vol 280 (5) ◽  
pp. C1215-C1223 ◽  
Author(s):  
Ana M. Pajor ◽  
Rama Gangula ◽  
Xiaozhou Yao
Keyword(s):  
Electrical Properties ◽  
Mouse Brain ◽  
Functional Characterization ◽  
The Other ◽  
Acidic Ph ◽  
High Affinity ◽  
The Family ◽  
Electrode Voltage ◽  
Menten Constant

Neurons contain a high-affinity Na+/dicarboxylate cotransporter for absorption of neurotransmitter precursor substrates, such as α-ketoglutarate and malate, which are subsequently metabolized to replenish pools of neurotransmitters, including glutamate. We have isolated the cDNA coding for a high-affinity Na+/dicarboxylate cotransporter from mouse brain, called mNaDC-3. The mRNA coding for mNaDC-3 is found in brain and choroid plexus as well as in kidney and liver. The mNaDC-3 transporter has a broad substrate specificity for dicarboxylates, including succinate, α-ketoglutarate, fumarate, malate, and dimethylsuccinate. The transport of citrate is relatively insensitive to pH, but the transport of succinate is inhibited by acidic pH. The Michaelis-Menten constant for succinate in mNaDC-3 is 140 μM in transport assays and 16 μM at −50 mV in two-electrode voltage clamp assays. Transport is dependent on sodium, although lithium can partially substitute for sodium. In conclusion, mNaDC-3 likely codes for the high-affinity Na+/dicarboxylate cotransporter in brain, and it has some unusual electrical properties compared with the other members of the family.

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