I am very happy to receive the award for the study of flowering regulation and florigen in rice. This research started a few years before I came to Nara and it has been the major project in my laboratory for the last 17 years. Many students, faculty members, and technical staff were involved in this research and I am grateful to all who participated in the project. The main achievements in this area of research are: identification of a conserved and distinct mechanism to generate photoperiodic regulation of flowering in a short day plant, rice and identification of Hd3a protein as a long-sought florigen in rice. These discoveries made a foundation to understand regulation of flowering in plants. The current research in our laboratory is involved in understanding molecular mechanisms for floral induction, role of florigen in growth and differentiation of plants, and development of synthetic florigen which can be used to regulate plant growth and flowering. Our study on these just started and we hope to gain insights into these questions in the future.

Fig. 1 Conserved and distinct mechanisms for the regulation of flowering in rice (short-day plant) and arabidopsis (long-day plant).
In Arabidosis regulatory genes GI and CO positively regulate FT under long-day conditions whereas in rice two distinct regulatory systems function under short-day and long-day conditions. Under long-day conditions Hd1 suppresses Hd3a inhibiting flowering while under short-day conditions Hd1 activates Hd3a resulting in flowering. This model explains the difference in the molecular mechanism for long-day and short-day regulation of flowering in plants. Hayama et al., Nature 2003