Abstract
The transition from vegetative to reproductive phase in plants is regulated by environmental stimuli such as light and temperature. In Arabidopsis, it is well known that phytochrome, a red/far-red light photoreceptor, and cryptochrome, a blue light photoreceptor, are the major photoreceptor to regulate flowering. However little is known about the sites where these photoreceptors act. We have reported that phytochrome B acts in mesophyll cells of cotyledons to regulate flowering (Endo et al., 2005). In the present study, we produced several transgenic lines that express cryptochrome 2- (cry2-) GFP fusion protein in organ/tissue specific manners. Analyses of these lines revealed that only cry2 in vascular bundles (probably that in the phloem) regulated flowering. Further analysis suggested that cry2 in vascular bundle regulated flowering by altering the expression of a key flowering regulator gene, FLOWERING LOCUS T, in a cell-autonomous manner.
