Abstract
Blue-light photoreceptor phototropins (phot1 and phot2) function in phototropism, chloroplast relocation, stomatal opening and leaf flattening. In Arabidopsis, phot1 and phot2 have overlapping and distinct functions. Namely, phot1 exhibits higher sensitivity to blue light than phot2. While both phot1 and phot2 mediate chloroplast photoaccumulation response, only phot2 mediates chloroplast photoavoidance response.
Photoropin consists of two functional domains, the N-terminal photosensory domain and the C-terminal kinase domain. To identify the domain that was responsible for the functional specificity of phot1 and phot2, we swapped the N and C-terminal domains and fused them to GFP (namely P1n/2cG and P2n/1cG). The transgenic plants expressing P1n/2cG, P2n/1cG, PHOT1-GFP and PHOT2-GFP under the PHOT2 promoter were produced and analyzed. For phototropism, the photosensitivity was determined almost exclusively by the N-terminal domain. For chloroplast relocation, both P1n/2cG and P2n/1cG mediated photoaccumulation and photoavoidance responses. Subcellular localization of those chimeric phototropins will be also discussed.
