Abstract
In Arabidopsis, FLOWERING LOCUS T (FT) is expressed in leaf vasculatures in response to external (photoperiod, light quality and temperature) and internal (age and size) signals, and FT protein is transported from leaves to shoot apex via phloem. At shoot apex, FT protein interacts with FD protein, a bZIP transcription factor, and controls the induction of downstream genes such as AP1 which is important for flower initiation. Thus, FT protein serves as the long-distance mobile flowering signal. However, temporal aspects and regulatory mechanism of transport have not yet been elucidated.
We analyzed the long-distance transport of FT protein by local and transient expression under regulation of heat shock protein promoter. FT protein was expressed transiently in a single leaf blade where the endogenous protein is expressed, and detection of the protein was performed at shoot apex at various times after induction. These and physiological analysis provided evidences for when enough amount of FT protein exits from source leaves and reaches at shoot apex.
We are also investigating the sites in FT protein that are important for the long-distance transport by site-directed mutagenesis.
