Expression of a Cs(+)-resistant guard cell K+ channel confers Cs(+)-resistant, light-induced stomatal opening in transgenic arabidopsis.
Inward-rectifying K+ (K+in) channels in the guard cell plasma membrane have been suggested to function as a major pathway for K+ influx into guard cells during stomatal opening. When K+in channels were blocked with external Cs+ in wild-type Arabidopsis guard cells, light-induced stomatal opening was reduced. Transgenic Arabidopsis plants were generated that expressed a mutant of the guard cell K+in channel, KAT1, which shows enhanced resistance to the Cs+ block. Stomata in these transgenic lines opened in the presence of external Cs+. Patch-clamp experiments with transgenic guard cells showed that inward K+(in) currents were blocked less by Cs+ than were K+ currents in controls. These data provide direct evidence that KAT1 functions as a plasma membrane K+ channel in vivo and that K+in channels constitute an important mechanism for light-induced stomatal opening. In addition, biophysical properties of K+in channels in guard cells indicate that components in addition to KAT1 may contribute to the formation of K+in channels in vivo.
Ichida
A M
AM
Department of Biology, University of California at San Diego, La Jolla 92093-0116, USA.
Pei
Z M
ZM
Baizabal-Aguirre
V M
VM
Turner
K J
KJ
Schroeder
J I
JI
D017360:Arabidopsis / Q000502:physiology / Q000528:radiation effects*; D002586:Cesium / Q000494:pharmacology*; D015870:Gene Expression; D015640:Ion Channel Gating; D018408:Patch-Clamp Techniques; D030821:Plants, Genetically Modified / Q000502:physiology / Q000528:radiation effects*; D015221:Potassium Channels / Q000187:drug effects* / Q000235:genetics
D015221:Potassium Channels; D002586:Cesium