Abstract
Phototropin (phot) is a blue light photoreceptor in plants that mediates phototropism, chloroplast relocation, stomata opening. Arabidopsis has two isoforms, phot1 and phot2. A phot molecule has two photoreceptive domains named LOV1 and LOV2 binding one FMN and a Ser/Thr kinase domain. Phot is thought to be a ligh-tregulated protein kinase.
From our studies, two important amino acids involved in photoreaction of FMN and conformational changes in the LOV domains have been found. Molecular-dynamics calculation and FTIR data propose the involvements of Arg interacting with phosphate grop of FMN and Gln nearby FMN, respectively, in the intramolecuar signal transduction. We have introduced the Arg-Lys or the Gln-Lue mutation into the LOV1, LOV2 or both LOV1 and LOV2 of Arabidopsis phot2 and examined the effect on phototropic and chloroplast avoidance responses. We found that these amino acids in the LOV2 domain play crucial roles in these physiological responses.
