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NaKR1 regulates long-distance movement of FLOWERING LOCUS T in Arabidopsis

Abstract

Flowering plants perceive photoperiodic signals in leaves to generate mobile stimuli required for the induction of flower formation at shoot apices. Although FLOWERING LOCUS T (FT) has been identified as part of the mobile floral stimuli in Arabidopsis thaliana, the mechanisms underlying long-distance movement of FT from leaves to shoot apices remain largely unclear. Here we show that a heavy-metal-associated (HMA) domain-containing protein, SODIUM POTASSIUM ROOT DEFECTIVE 1 (NaKR1), is activated by CONSTANS (CO) under long-day conditions and regulates long-distance movement of FT in Arabidopsis. Loss of function of NaKR1 compromises FT transport to shoot apices through sieve elements, causing late flowering under long-day conditions. NaKR1 and FT share similar expression patterns and subcellular localization, and interact with each other in vivo. Grafting experiments demonstrate that NaKR1 promotes flowering through mediating FT translocation from leaves to shoot apices. Thus, photoperiodic control of floral induction requires NaKR1-mediated long-distance delivery of florigenic signals.

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Figure 1: NaKR1 promotes flowering under long-day conditions.
Figure 2: NaKR1 is expressed and functional in leaf vascular tissues.
Figure 3: NaKR1 is localized in the phloem.
Figure 4: NaKR1 interacts with FT.
Figure 5: NaKR1 affects FT transport.
Figure 6: NaKR1 is required for the long-distance movement of FT.

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Acknowledgements

We thank J. M. Ward for providing nakr1-1 seeds. This work was supported by Academic Research Funds (MOE2011-T2-2-008) from the Ministry of Education, Singapore, the Singapore National Research Foundation Investigatorship Programme (NRF-NRFI2016-02) and intramural research support from National University of Singapore and Temasek Life Sciences Laboratory.

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Y.Z. and H.Y. conceived and designed the study. Y.Z., L.L. and L.S. performed the experiments. Y.Z., L.S. and H.Y. analysed data and wrote the paper.

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Correspondence to Hao Yu.

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The authors declare no competing financial interests.

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Supplementary Figs 1-12, Supplementary Table 1, and Supplementary Materials and Methods. (PDF 3220 kb)

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Zhu, Y., Liu, L., Shen, L. et al. NaKR1 regulates long-distance movement of FLOWERING LOCUS T in Arabidopsis. Nature Plants 2, 16075 (2016). https://doi.org/10.1038/nplants.2016.75

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