Channel-like characteristics of the low-affinity barley phosphate transporter PHT1;6 when expressed in Xenopus oocytes.
Remobilization of inorganic phosphate (P(i)) within a plant is critical for sustaining growth and seed production under external P(i) fluctuation. The barley (Hordeum vulgare) transporter HvPHT1;6 has been implicated in P(i) remobilization. In this report, we expressed HvPHT1;6 in Xenopus laevis oocytes, allowing detailed characterization of voltage-dependent fluxes and currents induced by HvPHT1;6. HvPHT1;6 increased efflux of P(i) near oocyte resting membrane potentials, dependent on external P(i) concentration. Time-dependent inward currents were observed when membrane potentials were more negative than -160 mV, which was consistent with nH(+):HPO(4)(2-) (n > 2) cotransport, based on simultaneous radiotracer and oocyte voltage clamping, dependent upon P(i) concentration gradient and pH. Time- and voltage-dependent inward currents through HvPHT1;6 were also observed for SO(4)(2-)and to a lesser degree for NO(3)(-)Cl(-)but not for malate. Inward and outward currents showed linear dependence on the concentration of external HPO(4)(2-)similar to low-affinity P(i) transport in plant studies. The electrophysiological properties of HvPHT1;6, which locates to the plasma membrane when expressed in onion (Allium cepa) epidermal cells, are consistent with its suggested role in the remobilization of P(i) in barley plants.
Preuss
Christian P
CP
Australian Centre for Plant Functional Genomics, Glen Osmond, South Australia 5064, Australia.
Huang
Chun Y
CY
Gilliham
Matthew
M
Tyerman
Stephen D
SD
D000818:Animals; D003001:Cloning, Molecular; D018744:DNA, Plant / Q000235:genetics; D001467:Hordeum / Q000235:genetics* / Q000378:metabolism; D008564:Membrane Potentials; D009865:Oocytes / Q000378:metabolism; D028061:Phosphate Transport Proteins / Q000235:genetics / Q000378:metabolism*; D010710:Phosphates / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D014981:Xenopus
D018744:DNA, Plant; D028061:Phosphate Transport Proteins; D010710:Phosphates; D010940:Plant Proteins