Abstract
FD, a bZIP transcription factor, preferentially expressed in the shoot apical meristem is required for FT protein to promote flowering. FD and FT interact and act at the SAM to promote flowering. FD contains several possible phosphorylation sites by various protein kinases. A C-terminal RSST motif is a recognition sequence of calcium-dependent protein kinases (CDPKs). Threonine-to-alanine substitution mutant in the RSST motif (T282A mFD) was unable to interact with FT, and expression of T282A mFD by cauliflower mosaic virus 35S promoter failed to rescue delayed-flowering phenotype of fd-1 mutant plants. These results suggest the importance of C-terminal CDPK site in regulation of the FD function. However actual phosphorylation of FD has not been demonstrated.
We demonstrated actual phosphorylation by the protein extracts from the shoot apical meristem of plants prior to flowering. Currently, identification of kinases is in progress and there are a few dozen candidates. Furthermore we are also interested in mechanism of FD-FT protein complex formation. Progress toward understanding the molecular basis of promotion of flowering by FD and FT will be presented.
