Gene Details:

Functional Descriptions:

  • In addition, expression of the Hd3a and Rice Flowering-locus T 1 (RFT1) florigen genes was up-regulated in leaves of the Hd1 Ehd1 line at the time of the floral transition.
  • Knockdown of OsSAMS1, 2 and 3 led to distinguished late flowering and greatly reduced the expression of the flowering key genes, Early heading date 1 (Ehd1), Hd3a and RFT1 (rice FT-like genes).
  • RICE FLOWERING LOCUS T 1 (RFT1/FT-L3) is the closest homologue of Heading date 3a (Hd3a), which is thought to encode a mobile flowering signal and promote floral transition under short-day (SD) conditions.
  • Although RFT1 RNAi plants flowered normally, double RFT1-Hd3a RNAi plants did not flower up to 300 days after sowing (DAS), indicating that Hd3a and RFT1 are essential for flowering in rice.
  • RFT1 expression was very low in wild-type plants, but there was a marked increase in RFT1 expression by 70 DAS in Hd3a RNAi plants, which flowered 90 DAS.
  • Hd3a and RFT1 are essential for flowering in rice.
  • We show here that RICE FLOWERING LOCUS T 1 (RFT1), the closest homolog to Heading date 3a (Hd3a), is a major floral activator under LD conditions.
  • An RFT1:GFP fusion protein localized in the shoot apical meristem (SAM) under LD conditions, suggesting that RFT1 is a florigen gene in rice.
  • By regulating Ehd1, RFT1, and Hd3a, Ghd8 delayed flowering under long-day conditions, but promoted flowering under short-day conditions.
  • To assign the position of Ehd2 within the flowering pathway of rice, we compared transcript levels of previously isolated flowering-time genes, such as Ehd1, a member of the unique pathway, Hd3a, and Rice FT-like1 (RFT1; rice florigens), between the wild-type plants and the ehd2 mutants.
  • Severely reduced expression of these genes in ehd2 under both short- and long-day conditions suggests that Ehd2 acts as a flowering promoter mainly by up-regulating Ehd1 and by up-regulating the downstream Hd3a and RFT1 genes in the unique genetic network of photoperiodic flowering in rice.
  • The Early heading date 1 (Ehd1) which promotes the RFT1, was up-regulated by DTH3 in both LD and SD conditions.
  • A rice ortholog of Arabidopsis APETALA1, OsMADS14, was expressed in the floral meristem in wild-type but not in RFT1 RNAi plants, suggesting that OsMADS14 is activated by RFT1 protein in the SAM after the transition to flowering.
  • Among these regulators, Ehd1, a rice-specific floral inducer, integrates multiple pathways to regulate RFT1, leading to flowering under appropriate photoperiod conditions.
  • OsId1 regulates the expression of Ehd1 (Early heading date 1) and its downstream genes, including Hd3a (a rice ortholog of FT) and RFT1 (Rice Flowering Locus T1), under both SD and LD conditions.
  • This indicates that LHD1 may delay flowering by repressing the expression of Ehd1, Hd3a and RFT1 under long-day conditions.
  • We also found that LHD1 could down-regulate the expression of several floral transition activators such as Ehd1, Hd3a and RFT1 under long-day conditions, but not under short-day conditions.
  • Furthermore, SNPs in the regulatory region of RFT1 and the E105K substitution in 1,397 accessions show strong linkage disequilibrium with a flowering time-associated SNP.
  • These findings indicate that natural mutations in RFT1 provide flowering time divergence under long-day conditions.
  • These results indicate that Hd3a and RFT1 act as floral activators under SD conditions, and that RFT1 expression is partly regulated by chromatin modification.
  • This suggests that the divergent functions of paralogs RFT1 and Hd3a, and of MADS50 and MADS51, are in part due to differential H3K36me2/3 deposition, which also correlates with higher expression levels of MADS50 and RFT1 in flowering promotion in rice.
  • The histone methyltransferase SDG724 mediates H3K36me2/3 deposition at MADS50 and RFT1 and promotes flowering in rice.
  • Furthermore, mutants in OsMADS50, a rice ortholog of Arabidopsis SUPPRESOR OF OVEREXPRESSION OF CONSTANS 1 (SOC1) did not flower up to 300 days after sowing under LD conditions, indicating that OsMADS50, which acts upstream of RFT1, promotes flowering under LD conditions.
  • We propose that both positive (OsMADS50 and Ehd1) and negative (Hd1, phyB and Ghd7) regulators of RFT1 form a gene network that regulates LD flowering in rice.
  • A gene network for long-day flowering activates RFT1 encoding a mobile flowering signal in rice.
  • Here, we demonstrate that functional defects in the florigen gene RFT1 are the main cause of late flowering in an indica cultivar, Nona Bokra.
  • Mapping and complementation studies revealed that sequence polymorphisms in the RFT1 regulatory and coding regions are likely to cause late flowering under long-day conditions.
  • Sequencing of the RFT1 region in rice accessions from a global collection showed that the E105K mutation is found only in indica, and indicated a strong association between the RFT1 haplotype and extremely late flowering in a functional Hd1 background.
  • The RFT1 (ZS97) allele was shown to delay heading and increase plant height, grain weight, grain number and grain yield, indicating that RFT1 plays an important role in the growth and development of rice.
  • To further our study of RFT1 , we overexpressed the gene and examined the expression patterns of major regulatory genes during floral transition and inflorescence development.
  • This indicated that RFT1 promotes the expression of major regulatory genes that are important for inflorescence development.
  • RFT1 overexpression also induced SEPALLATA (SEP)-clade genes OsMADS1 , OsMADS5 , and OsMADS7 in the greening calli before floral transition occurred.
  • Here, we reported that rice florigen gene RFT1 plays an important role in controlling amino acid contents of rice grain.

Literature:

Gene Resources:

Sequences:

cDNA Sequence
  • >LOC_Os06g06300.1
    CCTGTCACTGTTTGGCTAGCTTAACCTTCCTGACATCTATCCTCTGGATTGAACGGCAGGAGATACCTAAGCTAGCTAGCAATCTCTATCGATCTGTTTGTTTACATGTTCAGTTAAAGGTTACTGAGAAATGCCTAGAGTTTTTCCGGCTAGCTTCATAAGTTAGTGGGTTAGCTGACCTAGATTCAAAGTCTAATCCTTTTATTTATTTGATATTAGATATCCTAACGTTTTTAGTTAGAGGTTATTAATTTGACATGGCCGGCAGCGGCAGGGACGATCCTCTTGTGGTTGGCAGGATTGTGGGTGATGTGCTGGATCCATTCGTCCGGATCACTAACCTCAGTGTCAGCTATGGTGCAAGGATCGTCTCCAATGGCTGCGAGCTCAAGCCGTCCATGGTGACCCAACAGCCCAGGGTCGTGGTCGGTGGCAATGACATGAGGACGTTCTACACACTCGTGATGGTAGACCCGGATGCTCCGAGCCCAAGCAACCCTAACCTTAGGGAGTATCTACACTGGCTGGTCACCGATATTCCTGGTACCACTGGAGCAACATTTGGGCAAGAGGTGATGTGCTACGAGAGCCCAAGGCCAACCATGGGGATCCACCGGCTGGTGTTCGTGCTGTTCCAGCAGCTGGGGCGTCAGACGGTGTACGCACCGGGGTGGCGCCAGAACTTCAGCACCAGGAACTTCGCCGAGCTCTACAACCTCGGCTCGCCGGTCGCCACCGTCTACTTCAACTGCCAGCGCGAGGCCGGCTCCGGCGGCAGGAGGGTCTACCCCTAGCTAGCTACGCATGCCACCCGGCCTCCATGCATGCAGCAGCTATAGCTAAGCTGAGACCTGCCTAGCTGTATA
CDS Sequence
  • >LOC_Os06g06300.1
    ATGGCCGGCAGCGGCAGGGACGATCCTCTTGTGGTTGGCAGGATTGTGGGTGATGTGCTGGATCCATTCGTCCGGATCACTAACCTCAGTGTCAGCTATGGTGCAAGGATCGTCTCCAATGGCTGCGAGCTCAAGCCGTCCATGGTGACCCAACAGCCCAGGGTCGTGGTCGGTGGCAATGACATGAGGACGTTCTACACACTCGTGATGGTAGACCCGGATGCTCCGAGCCCAAGCAACCCTAACCTTAGGGAGTATCTACACTGGCTGGTCACCGATATTCCTGGTACCACTGGAGCAACATTTGGGCAAGAGGTGATGTGCTACGAGAGCCCAAGGCCAACCATGGGGATCCACCGGCTGGTGTTCGTGCTGTTCCAGCAGCTGGGGCGTCAGACGGTGTACGCACCGGGGTGGCGCCAGAACTTCAGCACCAGGAACTTCGCCGAGCTCTACAACCTCGGCTCGCCGGTCGCCACCGTCTACTTCAACTGCCAGCGCGAGGCCGGCTCCGGCGGCAGGAGGGTCTACCCCTAG
Protein Sequence
  • >LOC_Os06g06300.1
    MAGSGRDDPLVVGRIVGDVLDPFVRITNLSVSYGARIVSNGCELKPSMVTQQPRVVVGGNDMRTFYTLVMVDPDAPSPSNPNLREYLHWLVTDIPGTTGATFGQEVMCYESPRPTMGIHRLVFVLFQQLGRQTVYAPGWRQNFSTRNFAELYNLGSPVATVYFNCQREAGSGGRRVYP*