Abstract
Phytochrome B (phyB) molecule consists of two domains: the N-terminal photosensory domain and the C-terminal domain, and the latter has been believed to transduce the signal to downstream components. However, our recent study has demonstrated that the N-terminal domain alone of phyB was fully functional when dimerized and localized in the nucleus. Moreover, a 450-amino acid N-terminal fragment of phyB effectively transduced the signal in the nucleus.
Here, we analyzed missense mutations within the N-terminal domain of phyB to identify the site critical for signaling. We mutagenized transgenic Arabidopsis expressing the N-terminal domain of phyB and screened for long hypocotyl mutants in red light. As a result, we identified several missense mutations within the N-terminal domain of phyB, some of which exhibited normal photochemical properties. Interestingly, they fell within a relatively small region, suggesting that this site is directly involved in phyB signal transduction.
