Characterization of two HKT1 homologues from Eucalyptus camaldulensis that display intrinsic osmosensing capability

Liu, WH, Fairbairn, DJ, Reid, RJ and Schachtman, DP (2001) Characterization of two HKT1 homologues from Eucalyptus camaldulensis that display intrinsic osmosensing capability. Plant Physiology, 127 1: 283-294. doi:10.1104/pp.127.1.283


Author Liu, WH
Fairbairn, DJ
Reid, RJ
Schachtman, DP
Title Characterization of two HKT1 homologues from Eucalyptus camaldulensis that display intrinsic osmosensing capability
Journal name Plant Physiology   Check publisher's open access policy
ISSN 0032-0889
Publication date 2001
Sub-type Article (original research)
DOI 10.1104/pp.127.1.283
Volume 127
Issue 1
Start page 283
End page 294
Total pages 12
Editor N.V. Raikhel
Place of publication Rockville, USA
Publisher American Society of Plant Biologists
Collection year 2001
Language eng
Subject C1
620399 Forestry not elsewhere classified
270402 Plant Physiology
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.
Keyword Plant Sciences
Affinity K+ Transporter
Potassium Transporter
Higher-plants
Ion Channels
Saccharomyces-cerevisiae
Xenopus Oocytes
Salt Tolerance
Guard-cells
Na+ Uptake
Arabidopsis
Q-Index Code C1

Document type: Journal Article
Sub-type: Article (original research)
Collection: School of Biological Sciences Publications
 
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Created: Tue, 14 Aug 2007, 16:27:50 EST