Molecular action of florigen in the floral
transition of shoot apical meristems
Hd3a and FT belong to the PEBP (phosphatidylethanolamine-binding protein) family that is highly conserved among organisms from bacteria to humans [45].
PEBP is a small globular protein with a pocket structure
for anion binding [46]. Several florigen interacting
proteins have been identified (Table 2). InArabidopsis,
FT protein interacts with FD, a bZIP-type transcription
factor, to activate AP1, a floral meristem identity gene
[47,48]. No distinct domains for transcriptional regulation, such as acidic amino acid-rich or glutamine-rich
domains, have been found in FT and Hd3a. Such a
regulatory pathway as FT-FD inArabidopsiscould exist
in rice, although the FDortholog in rice remains to be
identified [49]. RNAi plants of Hd3aorRFT1showed
strong attenuation ofOsMADS14andOsMADS15RNA, as
well as a delay in flowering [8
,15
]. OsMADS14 and
OsMADS15 belong to the AP1 subfamily of the plant
MADS family [50]. The genetic role ofOsMADS14and
OsMADS15in the process of floral transition remains to be
analyzed