Abstract
The phytochrome molecule has two domains: the N-terminal photosensory domain and the C-terminal domain which contains signaling motifs such as a kinase domain. The latter has been widely believed to transduce the signal to downstream components. Our recent study clearly demonstrated that the N-terminal domain, but not the C-terminal domain, of Arabidopsis phytochrome B (phyB) transduces the signal, which forces us to reconsider our view on phytochrome. Then we took a genetic screening strategy to address which amino acid residue within the N-terminal domain of phyB is directly involved in signal transfer. As a result, we identified 6 missense mutations within phyB N-terminal domain which abolished signaling competence of phyB without affecting its spectral nature. Interestingly, they fell within a relatively small region with significant homology to PAS domain, suggesting that the protein-protein interaction through this region might be directly involved in phyB signal transduction.
