Dominant negative guard cell K+ channel mutants reduce inward-rectifying K+ currents and light-induced stomatal opening in arabidopsis.
Inward-rectifying potassium (K+(in)) channels in guard cells have been suggested to provide a pathway for K+ uptake into guard cells during stomatal opening. To test the proposed role of guard cell K+(in) channels in light-induced stomatal opening, transgenic Arabidopsis plants were generated that expressed dominant negative point mutations in the K+(in) channel subunit KAT1. Patch-clamp analyses with transgenic guard cells from independent lines showed that K+(in) current magnitudes were reduced by approximately 75% compared with vector-transformed controls at -180 mV, which resulted in reduction in light-induced stomatal opening by 38% to 45% compared with vector-transformed controls. Analyses of intracellular K+ content using both sodium hexanitrocobaltate (III) and elemental x-ray microanalyses showed that light-induced K+ uptake was also significantly reduced in guard cells of K+(in) channel depressor lines. These findings support the model that K+(in) channels contribute to K+ uptake during light-induced stomatal opening. Furthermore, transpirational water loss from leaves was reduced in the K+(in) channel depressor lines. Comparisons of guard cell K+(in) current magnitudes among four different transgenic lines with different K+(in) current magnitudes show the range of activities of K+(in) channels required for guard cell K+ uptake during light-induced stomatal opening.
Kwak
J M
JM
Division of Biology, Cell and Developmental Biology Section, University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0116, USA.
Murata
Y
Y
Baizabal-Aguirre
V M
VM
Merrill
J
J
Wang
M
M
Kemper
A
A
Hawke
S D
SD
Tallman
G
G
Schroeder
J I
JI
D017360:Arabidopsis / Q000235:genetics / Q000502:physiology* / Q000528:radiation effects; D029681:Arabidopsis Proteins; D001693:Biological Transport, Active; D018506:Gene Expression Regulation, Plant; D015640:Ion Channel Gating / Q000235:genetics; D008027:Light; D008564:Membrane Potentials / Q000187:drug effects; D018408:Patch-Clamp Techniques; D019441:Plant Epidermis / Q000235:genetics / Q000502:physiology*; D010940:Plant Proteins; D018526:Plant Transpiration / Q000502:physiology; D030821:Plants, Genetically Modified / Q000502:physiology / Q000528:radiation effects; D017354:Point Mutation; D011188:Potassium / Q000378:metabolism*; D015221:Potassium Channels / Q000235:genetics / Q000502:physiology*; D024661:Potassium Channels, Inwardly Rectifying
D029681:Arabidopsis Proteins; C501210:KAT1 protein, Arabidopsis; D010940:Plant Proteins; D015221:Potassium Channels; D024661:Potassium Channels, Inwardly Rectifying; D011188:Potassium