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 and cause floral evocation. 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 in plants, however, remains largely unknown. To understand the molecular function of Hd3a protein complex, in-depth mutation analysis of Hd3a was performed.
Mutant Hd3a proteins were designed on the basis of structural information and tested for the interaction with Hd3a-interacting proteins and for transcriptional activation activity by transient assay in rice suspension cells. Results suggested that Hd3a make complex with rice GF14 and rice FD homolog to activate the target gene expression. Analysis of RCN, by contrast, suggested that RCN make similar protein complex to repress it. Taken together, the molecular mechanism of floral evocation by florigen will be discussed.
