Regulation of flowering in rice: two florigen genes, a complex gene network, and natural variation

▶ In rice, Hd3a and RFT1 function as florigen in SD and LD, respectively. ▶ Hd3a and RFT1 are suppressed in LD and SD, respectively. ▶ Variation in Hd3a regulation contributes to the flowering time diversity in rice. ▶ SOC1 and LFY function in floral induction is different between Arabidopsis and rice. Photoperiodic control of flowering time consists of a complicated network that converges into the generation of a mobile flowering signal called florigen. Recent advances identifying the protein FT/Hd3a as the molecular nature responsible for florigen activity have focused current research on florigen genes as the important output of this complex signaling network. Rice is a model system for short-day plants and recent progress in elucidating the flowering network from rice and Arabidopsis, a long-day plant, provides an evolutionarily comparative view of the photoperiodic flowering pathway. This review summarizes photoperiodic flowering control in rice, including the interaction of complex layers of gene networks contributed from evolutionarily unique factors and the regulatory adaptation of conserved factors.