Abstract
Many plant species monitor and respond to changes in day length (photoperiod) for aligning reproduction with a favourable season. Day length is measured in leaves and, when appropriate, leads to the production of floral stimuli called florigens that are transmitted to the shoot apical meristem to initiate inflorescence development1. Rice possesses two florigens encoded by HEADING DATE 3a (Hd3a) and RICE FLOWERING LOCUS T 1 (RFT1)2. Here we show that the arrival of Hd3a and RFT1 at the shoot apical meristem activates FLOWERING LOCUS T-LIKE 1 (FT-L1), encoding a florigen-like protein that shows features partially differentiating it from typical florigens. FT-L1 potentiates the effects of Hd3a and RFT1 during the conversion of the vegetative meristem into an inflorescence meristem and organizes panicle branching by imposing increasing determinacy to distal meristems. A module comprising Hd3a, RFT1 and FT-L1 thus enables the initiation and balanced progression of panicle development towards determinacy.
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Data availability
All data generated or analysed during this study are included in this Letter (and its supplementary files). The 3D protein structure of FT-L1 was modelled on the basis of available structural data on monomeric AtFT (PDB ID 6igh.1).
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Acknowledgements
We thank G. Valè, CREA-RIS and the staff of the Botanical Garden ‘Città Studi’ for technical support with the field experiments and the NO LIMITS facility for technical support with confocal microscopy. We thank P. E. Colleoni for support with the molecular studies. This work was supported by the Shanghai Science and Technology Innovation Plan (grant no. 20ZR1467000) to D. Miki, by an ERC Starting Grant (no. 260963) to F.F. and by the Italy–Japan bilateral collaboration programme funded by the Italian Ministry of Foreign Affairs and International Cooperation (Grande Rilevanza, grant no. PGR10047) to F.F.
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F.G., G.A.B., D. Martignago, Y.M., G.V., T.T., M.C., D.C., M.B., B.K., P.M., D.G. and V.B. performed the expression analyses, generated the transgenic plants, recorded the phenotypes and analysed the data. R.W., D.K. and D. Miki designed and produced the GFP knock-in plants. W.T. and M.K. produced the Volano mutant collection. M.M. performed the field experiments. G.C., V.B., D. Miki and J.K. conceived the experiments. F.F. and F.G. conceived the project and wrote the manuscript.
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Nature Plants thanks Richard Immink and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.
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Supplementary Figs. 1–9.
Supplementary Table 1
Pearson correlation coefficients among gene transcripts (FT-L1 versus 728 Affymetrix rice microarrays). Genes indicated in red have been demonstrated to regulate aspects of reproductive (mostly floral) development.
Supplementary Data 1
Statistical source data.
Supplementary Data 2
Unprocessed western blots.
Supplementary Data 3
Primers used in this study.
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Giaume, F., Bono, G.A., Martignago, D. et al. Two florigens and a florigen-like protein form a triple regulatory module at the shoot apical meristem to promote reproductive transitions in rice. Nat. Plants 9, 525–534 (2023). https://doi.org/10.1038/s41477-023-01383-3
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DOI: https://doi.org/10.1038/s41477-023-01383-3
