Abstract
Phototropins, blue light receptors, mediate stomatal opening through the activation of the plasma membrane H+-ATPase. We have already shown that a protein phosphatase 1 (PP1) positively regulates the signaling from phototropins to the H+-ATPase in guard cells of Vicia faba. In this report, we used guard cells from Arabidopsis thaliana to investigate PP1 functions in detail. We first confirmed that PP1 is located between phototropins and the H+-ATPase in blue light signaling of guard cells from Arabidopsis. Tautomycin, an inhibitor of PP1, inhibited both blue light-dependent stomatal opening in the epidermis and the H+ pumping from guard cell protoplasts. However, it did not inhibit the fusicoccin-dependent H+ pumping. We expect that there is the substrate for PP1 in guard cells. We are now trying to identify proteins that are dephosphorylated in response to blue light in guard cells from both Arabidopsis and V. faba. We used 2D-DIGE for the separation and detection of dephosphorylated proteins in guard cells. We will identify these proteins by LC-MS/MS and the results will be reported.
