Abstract
Phototropins (phot) are one of the important blue light receptors in plants and are involved in phototropism, stomata opening, chloroplast relocation, leaf expansion and etc. The N-terminal half has two light-receptive domains (LOV1, LOV2) each of which binds an FMN and the C-terminal half forms a Ser/Thr kinase (KD). The kinase activity is inhibited by LOV2 in the dark. Blue light cancels the inhibition resulting in both auto- and substrate-phosphorylation. In Arabidopsis, there are two phots. phot1 and phot2 act as low- and high-light sensor, respectively. We have reported that bacterially expressed Arabidopsis phot1 LOV2-KD showed kinase activity on the peptide of phot1-N-terminal region as an artificial substrate. In this study, we performed biochemical analyses for phot2 LOV2-KD peptide. It phosphorylated the phot1-N-terminal region. We will discuss the differences of light-regulation mechanisms of kinase activity between phot1 and phot2.
