抄録
Phototropins (phot1 and phot2), membrane-associated protein kinases, act as blue-light photoreceptors for phototropism, chloroplast relocation, stomatal opening, and leaf flattening in Arabidopsis. Phototropins have three functional domains, two LOV domains in their N-termini and a Ser/Thr kinase domain in their C-termini. We have recently reported that phot2 associates with the Golgi apparatus in a light-dependent manner (Kong et al., 2005, Plant J., in press). Here we analyzed the structure/function relationship in phot2 using transgenic Arabidopsis. The phot2 C-terminal kinase domain fused to GFP (P2CG) was localized to the plasma membrane and the Golgi apparatus, whereas the N-terminus fused to GFP (P2NG) was uniformly localized in the cytoplasm. P2CG exhibited dominant-positive activity for the physiological responses such as chloroplast relocation and stomatal opening. By contrast, the P2CG with a mutation that abolishes the kinase activity was localized mainly to the plasma membrane and exhibited dominant-negative activity over the endogenous phot2.
