Letter

Systemic transport of trans-zeatin and its precursor have differing roles in Arabidopsis shoots

  • Nature Plants 3, Article number: 17112 (2017)
  • doi:10.1038/nplants.2017.112
  • Download Citation
Received:
Accepted:
Published online:

Abstract

Organ-to-organ signal transmission is essential for higher organisms to ensure coordinated biological reactions during metabolism and morphogenesis. Similar to organs in animals, plant organs communicate by various signalling molecules. Among them, cytokinins, a class of phytohormones, play a key role as root-to-shoot long-distance signals, regulating various growth and developmental processes in shoots1,2. Previous studies have proposed that trans-zeatin-riboside, a type of cytokinin precursor, is a major long-distance signalling form in xylem vessels and its action depends on metabolic conversion via the LONELY GUY enzyme in proximity to the site of action3,​4,​5. Here we report an additional long-distance signalling form of cytokinin: trans-zeatin, an active form. Grafting between various cytokinin biosynthetic and transportation mutants revealed that root-to-shoot translocation of trans-zeatin, a minor component of xylem cytokinin, controls leaf size but not meristem activity-related traits, whereas that of trans-zeatin riboside is sufficient for regulating both traits. Considering the ratio of trans-zeatin to trans-zeatin-riboside in xylem and their delivery rate change in response to environmental conditions, this dual long-distance cytokinin signalling system allows plants to fine-tune the manner of shoot growth to adapt to fluctuating environments.

  • Subscribe to Nature Plants for full access:

    $62

    Subscribe

Additional access options:

Already a subscriber?  Log in  now or  Register  for online access.

References

  1. 1.

    & Cytokinins. Arabidopsis Book 12, e0168 (2014).

  2. 2.

    Cytokinins: activity, biosynthesis, and translocation. Annu. Rev. Plant. Biol. 57, 431–449 (2006).

  3. 3.

    et al. Direct control of shoot meristem activity by a cytokinin-activating enzyme. Nature 445, 652–655 (2007).

  4. 4.

    et al. Regulation of cytokinin biosynthesis, compartmentalization and translocation. J. Exp. Bot. 59, 75–83 (2008).

  5. 5.

    et al. Arabidopsis lonely guy (LOG) multiple mutants reveal a central role of the LOG-dependent pathway in cytokinin activation. Plant J. 69, 355–365 (2012).

  6. 6.

    & Long-distance transport of phytohormones through the plant vascular system. Curr. Opin. Cell. Biol. 34, 1–8 (2016).

  7. 7.

    , & Long-distance peptide signalling essential for nutrient homeostasis in plants. Curr. Opin. Cell. Biol. 34, 35–40 (2016).

  8. 8.

    , & Cytokinin signaling networks. Annu. Rev. Plant Biol. 63, 353–380 (2012).

  9. 9.

    & Q&A: how do plants respond to cytokinins and what is their importance? BMC Biol. 13, 102 (2015).

  10. 10.

    , , & Side-chain modification of cytokinins controls shoot growth in Arabidopsis. Dev. Cell 27, 452–461 (2013).

  11. 11.

    et al. Functional analyses of LONELY GUY cytokinin-activating enzymes reveal the importance of the direct activation pathway in Arabidopsis. Plant Cell 21, 3152–3169 (2009).

  12. 12.

    et al. Roles of Arabidopsis ATP/ADP isopentenyltransferases and tRNA isopentenyltransferases in cytokinin biosynthesis. Proc. Natl Acad. Sci. USA 103, 16598–16603 (2006).

  13. 13.

    et al. Integration of growth and patterning during vascular tissue formation in Arabidopsis. Science 345, 1255215 (2014).

  14. 14.

    et al. A bHLH complex activates vascular cell division via cytokinin action in root apical meristem. Curr. Biol. 24, 2053–2058 (2014).

  15. 15.

    et al. An epidermis-driven mechanism positions and scales stem cell niches in plants. Sci. Adv. 2, e1500989 (2016).

  16. 16.

    et al. Arabidopsis ABCG14 is essential for the root-to-shoot translocation of cytokinin. Proc. Natl Acad. Sci. USA 111, 7150–7155 (2014).

  17. 17.

    et al. Arabidopsis ABCG14 protein controls the acropetal translocation of root-synthesized cytokinins. Nat. Commun. 5, 3274 (2014).

  18. 18.

    et al. Feedback regulation of xylem cytokinin content is conserved in pea and Arabidopsis. Plant Physiol. 143, 1418–1428 (2007).

  19. 19.

    , , & Nitrogen-dependent accumulation of cytokinins in root and the translocation to leaf: implication of cytokinin species that induces gene expression of maize response regulator. Plant Cell Physiol. 42, 85–93 (2001).

  20. 20.

    , & Biochemical characteristics and ligand-binding properties of Arabidopsis cytokinin receptor AHK3 compared to CRE1/AHK4 as revealed by a direct binding assay. J. Exp. Bot. 57, 4051–4058 (2006).

  21. 21.

    et al. The specificity of cytokinin signalling in Arabidopsis thaliana is mediated by differing ligand affinities and expression profiles of the receptors. Plant J. 67, 157–168 (2011).

  22. 22.

    , & Structural basis for cytokinin recognition by Arabidopsis thaliana histidine kinase 4. Nat. Chem. Biol. 7, 766–768 (2011).

  23. 23.

    et al. Plant membrane assays with cytokinin receptors underpin the unique role of free cytokinin bases as biologically active ligands. J. Exp. Bot. 66, 1851–1863 (2015).

  24. 24.

    et al. Cytokinins are central regulators of cambial activity. Proc. Natl Acad. Sci. USA 105, 20027–20031 (2008).

  25. 25.

    & PIN-dependent auxin transport: action, regulation, and evolution. Plant Cell 27, 20–32 (2015).

  26. 26.

    et al. The gibberellin precursor GA12 acts as a long-distance growth signal in Arabidopsis. Nat. Plants 1, 15073 (2015).

  27. 27.

    , & Evidence for the translocation of gibberellin A3 and gibberellin-like substances in grafts between normal, dwarf1 and dwarf5 seedlings of Zea mays L. Plant Cell Physiol. 24, 379–388 (1983).

  28. 28.

    et al. ABA transport and transporters. Trends Plant Sci. 18, 325–333 (2013).

  29. 29.

    et al. AtIPT3 is a key determinant of nitrate-dependent cytokinin biosynthesis in Arabidopsis. Plant Cell Physiol. 45, 1053–1062 (2004).

  30. 30.

    et al. Cytokinin import rate as a signal for photosynthetic acclimation to canopy light gradients. Plant Physiol. 143, 1841–1852 (2007).

  31. 31.

    , , , & Effects of sulfur nutrition on expression of the soybean seed storage protein genes in transgenic Petunia. Plant Physiol. 99, 263–268 (1992).

  32. 32.

    et al. Long-distance, graft-transmissible action of Arabidopsis FLOWERING LOCUS T protein to promote flowering. Plant Cell Physiol. 49, 1645–1658 (2008).

  33. 33.

    et al. An efficient flat-surface collar-free grafting method for Arabidopsis thaliana seedlings. Plant Methods 9, 14 (2013).

  34. 34.

    et al. Highly sensitive and high-throughput analysis of plant hormones using MS-probe modification and liquid chromatographytandem mass spectrometry: an application for hormone profiling in Oryza sativa. Plant Cell Physiol. 50, 1201–1214 (2009).

  35. 35.

    , , & The Tzs protein from Agrobacterium tumefaciens C58 produces zeatin riboside 5′-phosphate from 4-hydroxy-3-methyl-2-(E)-butenyl diphosphate and AMP. FEBS Lett. 527, 315–318 (2002).

  36. 36.

    , , , & A new method for enzymatic preparation of isopentenyladenine-type and trans-zeatin-type cytokinins with radioisotope-labelling. J. Plant Res. 116, 259–263 (2003).

Download references

Acknowledgements

We thank N. Ifuku (RIKEN) for support with all of the experiments A.O. performed. We also thank T. Notaguchi (Nagoya University) for instruction on the grafting technique. This work was supported by the Grant-in-Aid for Young Scientists (B; no. JP16K18566), the Grant-in-Aid for Scientific Research on Innovative Areas (no. JP16H01477 and JP17H06473) and the NC-CARP project from the Ministry of Education, Culture, Sports, Science and Technology and JST CREST (no. JPMJCR13B1), Japan.

Author information

Affiliations

  1. RIKEN Center for Sustainable Resource Science, 1-7-22 Suehiro, Tsurumi, Yokohama 230-0045, Japan

    • Asami Osugi
    • , Mikiko Kojima
    • , Yumiko Takebayashi
    • , Nanae Ueda
    • , Takatoshi Kiba
    •  & Hitoshi Sakakibara
  2. Department of Biological Mechanisms and Functions, Graduate School of Bioagricultural Sciences, Nagoya University, Chikusa, Nagoya 464-8601, Japan

    • Asami Osugi
    •  & Hitoshi Sakakibara

Authors

  1. Search for Asami Osugi in:

  2. Search for Mikiko Kojima in:

  3. Search for Yumiko Takebayashi in:

  4. Search for Nanae Ueda in:

  5. Search for Takatoshi Kiba in:

  6. Search for Hitoshi Sakakibara in:

Contributions

A.O. conceived the study. A.O., T.K. and H.S. designed the experiments. A.O., M.K., Y.T., N.U. and T.K. performed the experiments. A.O., T.K. and H.S. discussed the results and wrote the manuscript.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Hitoshi Sakakibara.

Supplementary information

PDF files

  1. 1.

    Supplementary Information

    Supplementary Figures 1–7, Supplementary Tables 1–4.