Reevaluation of the Florigen Hypothesis: A Molecular Genetic Approach with Arabidopsis

Abstract

It has long been believed that floral stimulus generated in leaves upon photoperiodic induction is transported via phloem to the shoot apex and evokes floral morphogenesis. Graft-transmission of floral stimulus observed in various plants have provided evidence for the existence of causative substance(s) named florigen. However, the lack of good candidates causally related to flowering with above-mentioned properties has made the identification of florigen rather difficult.
FT, a potent promoter of flowering in Arabidopsis, acts in photoperiodic regulation of flowering. With the supposed properties of florigen in mind, patterns of expression, the site of the action, and graft-transmissibility of the action of FT have been examined by various approaches. Our efforts to reevaluate the florigen hypothesis through analysis of FT will be presented.