‘Florigen’ was proposed 75 years ago1 to be synthesized in the leaf and transported to the shoot apex, where it induces flowering. Only recently have genetic and biochemical studies established that florigen is encoded by FLOWERING LOCUS T (FT), a gene that is universally conserved in higher plants2,3,4. Nonetheless, the exact function of florigen during floral induction remains poorly understood and receptors for florigen have not been identified. Here we show that the rice FT homologue Hd3a5 interacts with 14-3-3 proteins in the apical cells of shoots, yielding a complex that translocates to the nucleus and binds to the Oryza sativa (Os)FD1 transcription factor, a rice homologue of Arabidopsis thaliana FD. The resultant ternary ‘florigen activation complex’ (FAC) induces transcription of OsMADS15, a homologue of A. thaliana APETALA1 (AP1), which leads to flowering. We have determined the 2.4 Å crystal structure of rice FAC, which provides a mechanistic basis for florigen function in flowering. Our results indicate that 14-3-3 proteins act as intracellular receptors for florigen in shoot apical cells, and offer new approaches to manipulate flowering in various crops and trees.
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We thank Y. Takahashi for the anti-14-3-3 antibody and S. Takayama for the BiFC vectors. We are grateful to I. Smith for critical reading of the manuscript. We also thank N. Inada for FRET measurement; Y. Nishio, Y. Ohno, E. Kawano and M. Kanda for technical assistance; Y. Tamaki, Y. Konomi and J. Naritomi for rice transformation; M. Yoneyama, H. Kinoshita and A. Yasuba for sample preparation; J. Tsukamoto for mass spectroscopy analysis; H. Fukada for ITC measurement; K. Takeshita and Y. Hara for crystallization; and members of the Laboratory of Plant Molecular Genetics and the Laboratory of Biophysics at Nara Institute of Science and Technology (NAIST) for discussions. We thank beamline staff of BL41XU and BL44XU at SPring-8 and Photon Factory for data collection. We also thank Academia Sinica and National Synchrotron Radiation Research Center (Taiwan) for use of the MX225-HE detector at BL44XU. This work was supported in part by grants from the Ministry of Education, Culture, Sports, Science and Technology (MEXT) through the Target Proteins Research Program, by the Global COE Program at NAIST, by Grants-in-Aid for Scientific Research to I.O., C.K. and K.S., by Grants-in-Aid for Scientific Research on Priority Areas to K.S. and by the Program for Promotion of Basic and Applied Researches for Innovations in Bio-oriented Industry from Bio-oriented Research Advancement Institution (BRAIN) to H.T.
The authors declare no competing financial interests.
This file contains Supplementary Text 1 to 7, additional references, Supplementary Figures 1 to 30 with legends and Supplementary Tables 1 to 6. The Supplementary Figures and Tables were missing from the original file posted online and were added on 8 August 2011. (PDF 20553 kb)
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Taoka, Ki., Ohki, I., Tsuji, H. et al. 14-3-3 proteins act as intracellular receptors for rice Hd3a florigen. Nature 476, 332–335 (2011). https://doi.org/10.1038/nature10272
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