Abstract
We performed the night-break (NB) experiments and carried out molecular analysis of flowering time genes in rice. NB caused delay of flowering by the down-regulation of Hd3a without affecting OsGI or Hd1 expression pattern, and phyB transduced NB signal to down-regulate Hd3a and inhibit flowering in rice (Ishikawa et al 2005). To understand roles of phytochrome in rice flowering in detail, we examined phytochrome mutant of rice using monochromatic light. NB effect induced by red light on Hd3a is dependent on the photon fluence and reversed by subsequent far-red light irradiation. We also analyzed Hd1 over-expressing rice (Hd1-ox) and found thatHd1-ox caused delay of flowering in SD with down-regulation of Hd3a. In contrast, when Hd1 was overexpressed in phyB mutant, flowering was promoted. These results suggest that phyB dependent signal modulates the activity of Hd1 in rice flowering. Roles of phytochrome on rice flowering will be discussed.
