Abstract
Phototropins (phot1 and phot2) are blue light receptors, mediating phototropism, chloroplast relocation, and stomatal opening in Arabidopsis. In this study, we show that 14-3-3 proteins bind to phot1, but not to phot2 when phototropin is phosphorylated by blue light in vivo. The 14-3-3 binding to phot1 was found in dark-grown seedlings, guard cells, and green leaves within 1 min after the illumination. We determined the sites of 14-3-3 binding and found two sites: phosphorylated Ser-376 and Ser-350 in the hinge1 region of phot1. The binding of 14-3-3 proteins to phototropin was very fast and reversible, and the phototropin-14-3-3 protein complex may have some unknown functions in all of these tissues. To clarify the physiological role of 14-3-3 binding to phot1, we transformed genomic phot1 with amino acid substitution of 14-3-3 binding sites into phot1 phot2 double mutant. We are now analyzing phot1-mediated responses in these transformants.
