Characterisation of two distinct HKT1-like potassium transporters from Eucalyptus camaldulensis.
Potassium is an essential macronutrient in higher plants. It plays an important physiological role in stoma movements, osmoregulation, enzyme activation and cell expansion. The demand for potassium can be substantial, especially when the plant concerned is a Eucalyptus tree in excess of 50 m tall. We have isolated two cDNAs, EcHKT1 and EcHKT2, from Eucalyptus camaldulensis (river red gum) which are expressed in leaves, stems and roots. These encode potassium transporter polypeptides with homology to the wheat K+-Na+ symporter, HKT1. EcHKT1 and EcHKT2 both complemented the K+-limited growth of an Escherichia coli K+-uptake-deficient triple mutant. EcHKT1 and EcHKT2 also mediated Na+ and K+ uptake when expressed in Xenopus oocytes. A comparison of the EcHKT1 and EcHKT2 sequences and their transport properties indicated that these cDNAs represent two K+ transporters with distinct functional characteristics. The functional and structural conservation between these two E. camaldulensis genes and the wheat HKT1 suggests that they play an important, albeit elusive, physiological role.
Fairbairn
D J
DJ
ForBio Research Pty Ltd, Milton, BC, Australia. fairbairn@comcen.com.au
Liu
W
W
Schachtman
D P
DP
Gomez-Gallego
S
S
Day
S R
SR
Teasdale
R D
RD
D000595:Amino Acid Sequence; D000818:Animals; D002352:Carrier Proteins / Q000235:genetics*; D027682:Cation Transport Proteins; D018076:DNA, Complementary / Q000737:chemistry / Q000235:genetics; D004305:Dose-Response Relationship, Drug; D004594:Electrophysiology; D004926:Escherichia coli / Q000235:genetics; D005052:Eucalyptus / Q000235:genetics*; D005260:Female; D018506:Gene Expression Regulation, Plant; D005816:Genetic Complementation Test; D008564:Membrane Potentials / Q000187:drug effects; D008565:Membrane Proteins / Q000235:genetics*; D008969:Molecular Sequence Data; D009154:Mutation; D009865:Oocytes; D018515:Plant Leaves / Q000235:genetics; D010940:Plant Proteins; D018517:Plant Roots / Q000235:genetics; D018547:Plant Stems / Q000235:genetics; D010946:Plants, Medicinal; D011188:Potassium / Q000494:pharmacology; D020033:Protein Isoforms / Q000235:genetics; D018749:RNA, Plant / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D012964:Sodium / Q000494:pharmacology; D027981:Symporters; D014018:Tissue Distribution; D014981:Xenopus
D002352:Carrier Proteins; D027682:Cation Transport Proteins; D018076:DNA, Complementary; C088864:HKT1 protein, plant; D008565:Membrane Proteins; D010940:Plant Proteins; D020033:Protein Isoforms; D018749:RNA, Plant; D027981:Symporters; D012964:Sodium; D011188:Potassium