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

Type of publication Peer-reviewed
Publikationsform Original article (peer-reviewed)
Author Ko D, Kang J, Kiba T, Park J, Kojima M, Do J, Kim K-Y, Kwon M, Endler A, Song W-Y, Martinoia E, Sakakibara H, Lee Y,
Project ABC transporters involved in signalling events
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Original article (peer-reviewed)

Journal Proc. Natl. Acad, Sci. USA
Title of proceedings Proc. Natl. Acad, Sci. USA


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.