Arabidopsis ABCG14 is essential for the root-to-shoot translocation of cytokinin

Proc Natl Acad Sci U S A. 2014 May 13;111(19):7150-5. doi: 10.1073/pnas.1321519111. Epub 2014 Apr 28.


Cytokinins are phytohormones that induce cytokinesis and are essential for diverse developmental and physiological processes in plants. Cytokinins of the trans-zeatin type are mainly synthesized in root vasculature and transported to the shoot, where they regulate shoot growth. However, the mechanism of long-distance transport of cytokinin was hitherto unknown. Here, we report that the Arabidopsis ATP-binding cassette (ABC) transporter subfamily G14 (AtABCG14) is mainly expressed in roots and plays a major role in delivering cytokinins to the shoot. Loss of AtABCG14 expression resulted in severe shoot growth retardation, which was rescued by exogenous trans-zeatin application. Cytokinin content was decreased in the shoots of atabcg14 plants and increased in the roots, with consistent changes in the expression of cytokinin-responsive genes. Grafting of atabcg14 scions onto wild-type rootstocks restored shoot growth, whereas wild-type scions grafted onto atabcg14 rootstocks exhibited shoot growth retardation similar to that of atabcg14. Cytokinin concentrations in the xylem are reduced by ∼90% in the atabcg14 mutant. These results indicate that AtABCG14 is crucial for the translocation of cytokinin to the shoot. Our results provide molecular evidence for the long-distance transport of cytokinin and show that this transport is necessary for normal shoot development.

Keywords: ABC transporter; long-distance signal; tZ-type cytokinin translocation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • ATP Binding Cassette Transporter, Subfamily G
  • ATP-Binding Cassette Transporters / genetics
  • ATP-Binding Cassette Transporters / metabolism*
  • Arabidopsis / genetics
  • Arabidopsis / growth & development
  • Arabidopsis / metabolism*
  • Arabidopsis Proteins / genetics
  • Arabidopsis Proteins / metabolism*
  • Cytokinins / biosynthesis
  • Cytokinins / metabolism*
  • Gene Expression Regulation, Plant
  • Plant Growth Regulators / metabolism
  • Plant Roots / growth & development
  • Plant Roots / metabolism*
  • Plant Shoots / growth & development
  • Plant Shoots / metabolism*
  • Signal Transduction / physiology


  • ABCG14 protein, Arabidopsis
  • ATP Binding Cassette Transporter, Subfamily G
  • ATP-Binding Cassette Transporters
  • Arabidopsis Proteins
  • Cytokinins
  • Plant Growth Regulators