Abstract
RICE FLOWERING LOCUS T 1 (RFT1) is the closest homolog to Heading date 3a (Hd3a), which promotes floral transition in short-day (SD) in rice. We demonstrate that RFT1 is a floral activator under long-day (LD) conditions. An RFT1:GFP fusion protein localized in the shoot apical meristem (SAM) under LD conditions, suggesting that RFT1 is a LD-specific florigen gene in rice. Furthermore, mutants in OsMADS50, a rice ortholog of Arabidopsis SUPPRESOR OF OVEREXPRESION OF CONSTANS 1 (SOC1) did not flower up to 300 days after sowing under LD conditions, suggesting that OsMADS50 is also a positive regulator of flowering in response to LD and the OsMADS50-Ehd1-RFT1-OsMADS14 and OsMADS15 pathway is involved in floral activation under LD conditions. We propose that both positive (OsMADS50, Ehd1 and RID1/Ehd2/OsId1) and negative (Hd1, phyB and Gdh7) regulators of RFT1 form a gene network which regulates LD flowering in rice.
