Abstract
Phytochrome B is a major plant photoreceptor and its polypeptide is folded into two domains: the N-terminal photosensory domain and the C-terminal domain which has been widely believed to transduce the signal to downstream components. However, we have recently found that the N-terminal domain of Arabidopsis phyB, when dimerized and localized in the nucleus, triggered full phyB responses with much higher photosensitivity than the intact full-length phyB. In order to elucidate the molecular mechanism of the N-terminal domain signaling of phyB, we performed a genetic screening for long hypocotyl mutants under very weak red light by mutagenizing the transgenic Arabidopsis expressing the artificial N-terminal domain protein described above. We have so far screened at least 1200,000 M2 seedlings which is derived from approximately 200,000 M1 plants. Here we will report the details of screening method and some recent results on the isolated extragenic mutations.
