Click here to close
Hello! We notice that you are using Internet Explorer, which is not supported by Xenbase and may cause the site to display incorrectly.
We suggest using a current version of Chrome,
FireFox, or Safari.
Characterization of two HKT1 homologues from Eucalyptus camaldulensis that display intrinsic osmosensing capability.
Liu W
,
Fairbairn DJ
,
Reid RJ
,
Schachtman DP
.
???displayArticle.abstract???
Plants have multiple potassium (K(+)) uptake and efflux mechanisms that are expressed throughout plant tissues to fulfill different physiological functions. Several different classes of K(+) channels and carriers have been identified at the molecular level in plants. K(+) transporters of the HKT1 superfamily have been cloned from wheat (Triticum aestivum), Arabidopsis, and Eucalyptus camaldulensis. The functional characteristics as well as the primary structure of these transporters are diverse with orthologues found in bacterial and fungal genomes. In this report, we provide a detailed characterization of the functional characteristics, as expressed in Xenopus laevis oocytes, of two cDNAs isolated from E. camaldulensis that encode proteins belonging to the HKT1 superfamily of K(+)/Na(+) transporters. The transport of K(+) in EcHKT-expressing oocytes is enhanced by Na(+), but K(+) was also transported in the absence of Na(+). Na(+) is transported in the absence of K(+) as has been demonstrated for HKT1 and AtHKT1. Overall, the E. camaldulensis transporters show some similarities and differences in ionic selectivity to HKT1 and AtHKT1. One striking difference between HKT1 and EcHKT is the sensitivity to changes in the external osmolarity of the solution. Hypotonic solutions increased EcHKT induced currents in oocytes by 100% as compared with no increased current in HKT1 expressing or uninjected oocytes. These osmotically sensitive currents were not enhanced by voltage and may mediate water flux. The physiological function of these osmotically induced increases in currents may be related to the ecological niches that E. camaldulensis inhabits, which are periodically flooded. Therefore, the osmosensing function of EcHKT may provide this species with a competitive advantage in maintaining K(+) homeostasis under certain conditions.
Arabidopsis Genome Initiative,
Analysis of the genome sequence of the flowering plant Arabidopsis thaliana.
2000, Pubmed
Arabidopsis Genome Initiative,
Analysis of the genome sequence of the flowering plant Arabidopsis thaliana.
2000,
Pubmed
Bihler,
The presumed potassium carrier Trk2p in Saccharomyces cerevisiae determines an H+-dependent, K+-independent current.
1999,
Pubmed
Blount,
Bacterial mechanosensitive channels: integrating physiology, structure and function.
1999,
Pubmed
Clemens,
The plant cDNA LCT1 mediates the uptake of calcium and cadmium in yeast.
1998,
Pubmed
Czempinski,
New structure and function in plant K+ channels: KCO1, an outward rectifier with a steep Ca2+ dependency.
1997,
Pubmed
Fairbairn,
Characterisation of two distinct HKT1-like potassium transporters from Eucalyptus camaldulensis.
2000,
Pubmed
,
Xenbase
Felix,
Sensing of osmotic pressure changes in tomato cells.
2000,
Pubmed
Fu,
AtKuP1: a dual-affinity K+ transporter from Arabidopsis.
1998,
Pubmed
Gassman,
Alkali cation selectivity of the wheat root high-affinity potassium transporter HKT1.
1996,
Pubmed
,
Xenbase
Gassmann,
Physiological Roles of Inward-Rectifying K+ Channels.
1993,
Pubmed
Gaymard,
Identification and disruption of a plant shaker-like outward channel involved in K+ release into the xylem sap.
1998,
Pubmed
,
Xenbase
Hirsch,
A role for the AKT1 potassium channel in plant nutrition.
1998,
Pubmed
Kammerloher,
Water channels in the plant plasma membrane cloned by immunoselection from a mammalian expression system.
1994,
Pubmed
,
Xenbase
Kim,
AtKUP1: an Arabidopsis gene encoding high-affinity potassium transport activity.
1998,
Pubmed
,
Xenbase
Kochian,
Can K+ Channels Do It All?
1993,
Pubmed
Lacombe,
A shaker-like K(+) channel with weak rectification is expressed in both source and sink phloem tissues of Arabidopsis.
2000,
Pubmed
,
Xenbase
Liu,
Voltage-dependent K+ channels as targets of osmosensing in guard cells.
1998,
Pubmed
Liu,
Partial deletion of a loop region in the high affinity K+ transporter HKT1 changes ionic permeability leading to increased salt tolerance.
2000,
Pubmed
,
Xenbase
Loo,
Cotransport of water by the Na+/glucose cotransporter.
1996,
Pubmed
,
Xenbase
Marten,
AKT3, a phloem-localized K+ channel, is blocked by protons.
1999,
Pubmed
,
Xenbase
Maurel,
Phosphorylation regulates the water channel activity of the seed-specific aquaporin alpha-TIP.
1995,
Pubmed
,
Xenbase
Nakamura,
Expression of an Arabidopsis potassium channel gene in guard cells.
1995,
Pubmed
Nelson,
Status of genome projects for nonpathogenic bacteria and archaea.
2000,
Pubmed
Nilius,
Volume-activated Cl- channels.
1996,
Pubmed
Quintero,
A new family of K+ transporters from Arabidopsis that are conserved across phyla.
1997,
Pubmed
Rigas,
TRH1 encodes a potassium transporter required for tip growth in Arabidopsis root hairs.
2001,
Pubmed
Rubio,
Genetic selection of mutations in the high affinity K+ transporter HKT1 that define functions of a loop site for reduced Na+ permeability and increased Na+ tolerance.
1999,
Pubmed
,
Xenbase
Rubio,
Sodium-driven potassium uptake by the plant potassium transporter HKT1 and mutations conferring salt tolerance.
1995,
Pubmed
,
Xenbase
Saitou,
Characterization of whole-cell currents elicited by mechanical stimulation of Xenopus oocytes.
2000,
Pubmed
,
Xenbase
Santa-María,
The HAK1 gene of barley is a member of a large gene family and encodes a high-affinity potassium transporter.
1997,
Pubmed
Schachtman,
Molecular and functional characterization of a novel low-affinity cation transporter (LCT1) in higher plants.
1997,
Pubmed
Schachtman,
Molecular pieces to the puzzle of the interaction between potassium and sodium uptake in plants.
1999,
Pubmed
Schachtman,
Structure and transport mechanism of a high-affinity potassium uptake transporter from higher plants.
1994,
Pubmed
,
Xenbase
Schachtman,
Molecular insights into the structure and function of plant K(+) transport mechanisms.
2000,
Pubmed
Schroeder,
Perspectives on the physiology and structure of inward-rectifying K+ channels in higher plants: biophysical implications for K+ uptake.
1994,
Pubmed
Strotmann,
OTRPC4, a nonselective cation channel that confers sensitivity to extracellular osmolarity.
2000,
Pubmed
Tholema,
Change to alanine of one out of four selectivity filter glycines in KtrB causes a two orders of magnitude decrease in the affinities for both K+ and Na+ of the Na+ dependent K+ uptake system KtrAB from Vibrio alginolyticus.
1999,
Pubmed
Uozumi,
The Arabidopsis HKT1 gene homolog mediates inward Na(+) currents in xenopus laevis oocytes and Na(+) uptake in Saccharomyces cerevisiae.
2000,
Pubmed
,
Xenbase
Urao,
Two-component systems in plant signal transduction.
2000,
Pubmed
Urao,
A transmembrane hybrid-type histidine kinase in Arabidopsis functions as an osmosensor.
1999,
Pubmed
Voets,
Reduced intracellular ionic strength as the initial trigger for activation of endothelial volume-regulated anion channels.
1999,
Pubmed
Walker,
Potassium homeostasis in vacuolate plant cells.
1996,
Pubmed
Walker,
A Drosophila mechanosensory transduction channel.
2000,
Pubmed
Ward,
Calcium-Activated K+ Channels and Calcium-Induced Calcium Release by Slow Vacuolar Ion Channels in Guard Cell Vacuoles Implicated in the Control of Stomatal Closure.
1994,
Pubmed
Yang,
Block of stretch-activated ion channels in Xenopus oocytes by gadolinium and calcium ions.
1989,
Pubmed
,
Xenbase
Zimmermann,
Plant ion channels: from molecular structures to physiological functions.
1999,
Pubmed
Zubrinich,
Tolerance of salinized floodplain conditions in a naturally occurring Eucalyptus hybrid related to lowered plant water potential.
2000,
Pubmed
