Abstract
Florigen is a hypothesized hormone-like molecule responsible for regulating flowering in plants. But the nature of florigen has remained elusive for 70 years. Recent studies suggest Hd3a/FT protein is the mobile flower-inducing hormone florigen. Actually, the Hd3a/FT protein expressed in the leaves moves to the apical meristem and promotes flowering. The floral transition by Hd3/FT is achieved by transcriptional activation of floral genes at the shoot apex, however, molecular mechanism remains unclear. To understand this mechanism, we performed a structural analysis of the rice florigen Hd3a protein.
The polypeptide encoding the rice florigen Hd3a was expressed in bacterial cells with a novel high-level bacterial expression system pCold-GST (Hayashi et al. 2008, Protein Expr. Purif. 62, 120). The molecular structure of Hd3a was determined by NMR. Hd3a-interacting proteins were identified by Yeast Two-Hybrid and evaluated interactions with Hd3a by NMR titration experiments, isothermal titration calorimetry (ITC) measurements and GST-pull down assay. From these results, the molecular mechanism of floral initiation by florigen will be discussed.
