A putative role for the plasma membrane potential in the control of the expression of the gene encoding the tomato high-affinity potassium transporter HAK5

Plant Mol Biol. 2008 Dec;68(6):521-32. doi: 10.1007/s11103-008-9388-3. Epub 2008 Aug 27.


A chimeric CaHAK1-LeHAK5 transporter with only 15 amino acids of CaHAK1 in the N-terminus mediates high-affinity K(+) uptake in yeast cells. Kinetic and expression analyses strongly suggest that LeHAK5 mediates a significant proportion of the high-affinity K(+) uptake shown by K(+)-starved tomato (Solanum lycopersicum) plants. The development of high-affinity K(+) uptake, putatively mediated by LeHAK5, was correlated with increased LeHAK5 mRNA levels and a more negative electrical potential difference across the plasma membrane of root epidermal and cortical cells. However, this increase in high-affinity K(+) uptake was not correlated with the root K(+) content. Thus, (i) growth conditions that result in a hyperpolarized root plasma membrane potential, such as K(+) starvation or growth in the presence of NH(4) (+), but which do not decrease the K(+) content, lead to increased LeHAK5 expression; (ii) the presence of NaCl in the growth solution, which prevents the hyperpolarization induced by K(+) starvation, also prevents LeHAK5 expression. Moreover, once the gene is induced, depolarization of the plasma membrane potential then produces a decrease in the LeHAK5 mRNA. On the basis of these results, we propose that the plant membrane electrical potential plays a role in the regulation of the expression of this gene encoding a high-affinity K(+) transporter.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Base Sequence
  • DNA Primers
  • Down-Regulation
  • Gene Expression Regulation, Plant / physiology*
  • Lycopersicon esculentum / genetics*
  • Lycopersicon esculentum / metabolism
  • Membrane Potentials*
  • Membrane Transport Proteins / genetics*
  • Membrane Transport Proteins / metabolism
  • Plant Proteins / genetics*
  • Plant Proteins / metabolism
  • Potassium / metabolism*


  • DNA Primers
  • Membrane Transport Proteins
  • Plant Proteins
  • Potassium