Dear Editor,Here,we report the developmental regulation of proteolytic cleavage of the FLOWERING LOCUS T (FT) protein.FT,a member of the phosphatidylethanolamine-binding protein (PEBP) family,functions as a florigen or a component of florigen.PEBP binds phosphoethanolamine,and its ligand-binding domain is evolutionarily conserved from bacteria to plants and animals (Schoentgen and Jolles,1995;Bradley et al.,1996).PEBPs regulate important signaling pathways to control growth and differentiation (Chautard et al.,2004).Some animal PEBP homologs undergo post-translational regulation.For example,hippocampal cholinergic neurostimulating peptide is produced as a precursor protein and cleaved by chymotrypsin-like proteases,a type of serine/cysteine protease (Tohdoh et al.,1995;Ojika et al.,2000).Although many studies have examined FT regulation at the transcriptional level,little is known about FT regulation at the protein level.