Blue light inhibits guard cell plasma membrane anion channels in a phototropin-dependent manner.
Guard cells respond to light through two independent signalling pathways. The first pathway is initiated by photosynthetically active radiation and has been associated with changes in the intercellular CO(2) concentration, leading to inhibition of plasma membrane anion channels. The second response is blue-light-specific and so far has been restricted to the activation of plasma membrane H(+)-ATPases. In a search for interactions of both signalling pathways, guard cells of Vicia faba and Arabidopsis thaliana were studied in intact plants. Vicia faba guard cells recorded in CO(2)-free air responded to blue light with a transient outward plasma membrane current that had an average peak value of 17 pA. In line with previous reports, changes in the current-voltage relation of the plasma membrane indicate that this outward current is based on the activation of H(+)-ATPases. However, when V. faba guard cells were blue-light-stimulated in air with 700 microl l(-1) CO(2), the outward current increased to 56 pA. The increase in current was linked to inhibition of S-type anion channels. Blue light also inhibited plasma membrane anion channels in A. thaliana guard cells, but not in the phot1 phot2 double mutant. These results show that blue light inhibits plasma membrane anion channels through a pathway involving phototropins, in addition to the stimulation of guard cell plasma membrane H(+)-ATPases.
Marten
Holger
H
Molecular Plant Physiology and Biophysics, Julius-von-Sachs Institute for Biosciences, Biocenter, Würzburg University, Julius-von-Sachs-Platz 2, D-97082 Würzburg, Germany.
Hedrich
Rainer
R
Roelfsema
M Rob G
MR
D017360:Arabidopsis / Q000166:cytology / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000502:physiology*; D002245:Carbon Dioxide / Q000494:pharmacology; D056931:Cryptochromes; D005420:Flavoproteins / Q000502:physiology*; D018506:Gene Expression Regulation, Plant / Q000187:drug effects / Q000528:radiation effects; D007473:Ion Channels / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D008027:Light; D018408:Patch-Clamp Techniques; D019441:Plant Epidermis / Q000166:cytology / Q000378:metabolism; D018515:Plant Leaves / Q000166:cytology / Q000502:physiology; D006180:Proton-Translocating ATPases / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000528:radiation effects
D029681:Arabidopsis Proteins; C538962:CRY1 protein, Arabidopsis; D056931:Cryptochromes; D005420:Flavoproteins; D007473:Ion Channels; D002245:Carbon Dioxide; D006180:Proton-Translocating ATPases