Abstract
Florigen is a plant hormone which was proposed by Chailakhyan in the 1930's. Florigen was proposed to be produced in the leaf after stimulation of day length change, translocated through phloem to shoot apex, and cause floral evocation. However, the molecular identity had been an enigma for long time. Recently, several lines of evidence in plant molecular genetics strongly suggest that Hd3a protein in rice (FT protein in Arabidopsis) is the florigen. Hd3a/FT, as well as the antagonist, RCN/TFL1, belongs to PEBP family which is highly conserved among organism. The molecular function of PEBP, however, remains largely unknown. To understand the molecular function of florigen, mutational analysis of Hd3a was performed.
On the basis of information of mutant alleles, the conserved residues, and the molecular structure of plant PEBP, several mutations were designed and introduced into Hd3a. The mutant Hd3a proteins were tested for interaction with rice GF14 and FD homolog, Hd3a-interacting proteins, by Y2H and for transcriptional activation activity by transient assay with rice suspension cells. The molecular mechanism of floral evocation by florigen will be discussed.
