The poplar K+ channel KPT1 is associated with K+ uptake during stomatal opening and bud development.
To gain insights into the performance of poplar guard cells, we have measured stomatal conductance and aperture, guard cell K+ content and K+-channel activity of the guard cell plasma membrane in intact poplar leaves. In contrast to Arabidopsis, broad bean and tobacco grown under same conditions, poplar stomata operated just in the dynamic range - any change in conductance altered the rate of photosynthesis. In response to light, CO2 and abscisic acid (ABA), the stomatal opening velocity was two to five times faster than that measured for Arabidopsis thaliana, Nicotiana tabacum and Vicia faba. When stomata opened, the K+ content of guard cells increased almost twofold, indicating that the very fast stomatal opening in this species is mediated via potassium uptake. Following impalement of single guard cells embedded in their natural environment of intact leaves with triple-barrelled microelectrodes, time-dependent inward and outward-rectifying K+-channel-mediated currents of large amplitude were recorded. To analyse the molecular nature of genes encoding guard cell K+-uptake channels, we cloned K+-transporter Populustremula (KPT)1 and functionally expressed this potassium channel in a K+-uptake-deficient Escherichia coli mutant. In addition to guard cells, this K+-transporter gene was expressed in buds, where the KPT1 gene activity strongly correlated with bud break. Thus, KPT1 represents one of only few poplar genes associated with bud flush.
Langer
Katharina
K
Julius-von-Sachs-Institut for Bioscience, Molecular Plant Physiology and Biophysics, University of Würzburg, Julius-von-Sachs-Platz 2, 97082 Würzburg, Germany.
Levchenko
Victor
V
Fromm
Jörg
J
Geiger
Dietmar
D
Steinmeyer
Ralf
R
Lautner
Silke
S
Ache
Peter
P
Hedrich
Rainer
R
D000595:Amino Acid Sequence; D001483:Base Sequence; D002712:Chlorides / Q000378:metabolism; D018744:DNA, Plant / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D017343:Genes, Plant; D005816:Genetic Complementation Test; D017136:Ion Transport; D008969:Molecular Sequence Data; D009154:Mutation; D018515:Plant Leaves / Q000166:cytology / Q000378:metabolism; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D032107:Populus / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism; D015221:Potassium Channels / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D021122:Protein Subunits; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D051637:Shaker Superfamily of Potassium Channels
D002712:Chlorides; D018744:DNA, Plant; D010940:Plant Proteins; D015221:Potassium Channels; D021122:Protein Subunits; D011994:Recombinant Proteins; D051637:Shaker Superfamily of Potassium Channels; D011188:Potassium