2001/09/01 by Weihong Liu, David J. Fairbairn, Rob J. Reid +2 · 101 citations
Agricultural and Biological Sciences · #Aquaporin #Biochemistry #Biology #Biophysics #Botany #Cell biology #Efflux #Eucalyptus camaldulensis #Function (biology) #Gene #Ion transporter #Membrane #Osmotic concentration #Plant Molecular Biology Research #Plant Stress Responses and Tolerance #Plant nutrient uptake and metabolism #Transporter #Xenopus
paper · pdf · doi:10.1104/pp.127.1.283
published in PLANT PHYSIOLOGY 127(1), 283-294 (Oxford University Press)
openalex publication_date 2001/09/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/28
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.