Arabidopsis ABCG14 is essential for the root-to-shoot translocation of cytokinin.
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.
Pohang University of Science and Technology-Universität Zürich (POSTECH-UZH) Global Research Laboratory, Division of Integrative Biosciences and Biotechnology, Pohang University of Science and Technology, Pohang 790-784, Korea;
Donghwi
D
Ko
Pohang University of Science and Technology-Universität Zürich (POSTECH-UZH) Global Research Laboratory, Division of Integrative Biosciences and Biotechnology, Pohang University of Science and Technology, Pohang 790-784, Korea;
Joohyun
J
Kang
Plant Productivity Systems Research Group, RIKEN Center for Sustainable Resource Science, Suehiro 1-7-22, Tsurumi, Yokohama 230-0045, Japan;
Takatoshi
T
Kiba
Pohang University of Science and Technology-Universität Zürich (POSTECH-UZH) Global Research Laboratory, Division of Integrative Biosciences and Biotechnology, Pohang University of Science and Technology, Pohang 790-784, Korea;
Jiyoung
J
Park
Plant Productivity Systems Research Group, RIKEN Center for Sustainable Resource Science, Suehiro 1-7-22, Tsurumi, Yokohama 230-0045, Japan;
Mikiko
M
Kojima
Department of Biotechnology, College of Life Science and Biotechnology, Korea University, Seoul 136-713, Korea; and.
Jihye
J
Do
Pohang University of Science and Technology-Universität Zürich (POSTECH-UZH) Global Research Laboratory, Division of Integrative Biosciences and Biotechnology, Pohang University of Science and Technology, Pohang 790-784, Korea;
Kyung Yoon
KY
Kim
Department of Biotechnology, College of Life Science and Biotechnology, Korea University, Seoul 136-713, Korea; and.
Mi
M
Kwon
Institut für Pflanzenbiologie, Universität Zürich, 8008 Zürich, Switzerland.
Anne
A
Endler
Pohang University of Science and Technology-Universität Zürich (POSTECH-UZH) Global Research Laboratory, Division of Integrative Biosciences and Biotechnology, Pohang University of Science and Technology, Pohang 790-784, Korea;
Won-Yong
WY
Song
Pohang University of Science and Technology-Universität Zürich (POSTECH-UZH) Global Research Laboratory, Division of Integrative Biosciences and Biotechnology, Pohang University of Science and Technology, Pohang 790-784, Korea;Institut für Pflanzenbiologie, Universität Zürich, 8008 Zürich, Switzerland.
Enrico
E
Martinoia
Plant Productivity Systems Research Group, RIKEN Center for Sustainable Resource Science, Suehiro 1-7-22, Tsurumi, Yokohama 230-0045, Japan;
Hitoshi
H
Sakakibara
Pohang University of Science and Technology-Universität Zürich (POSTECH-UZH) Global Research Laboratory, Division of Integrative Biosciences and Biotechnology, Pohang University of Science and Technology, Pohang 790-784, Korea; ylee@postech.ac.kr.
Youngsook
Y
Lee
D000070996:ATP Binding Cassette Transporter, Subfamily G; D018528:ATP-Binding Cassette Transporters / Q000235:genetics / Q000378:metabolism*; D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D003583:Cytokinins / Q000096:biosynthesis / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D010937:Plant Growth Regulators / Q000378:metabolism; D018517:Plant Roots / Q000254:growth & development / Q000378:metabolism*; D018520:Plant Shoots / Q000254:growth & development / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology
C000589386:ABCG14 protein, Arabidopsis; D000070996:ATP Binding Cassette Transporter, Subfamily G; D018528:ATP-Binding Cassette Transporters; D029681:Arabidopsis Proteins; D003583:Cytokinins; D010937:Plant Growth Regulators
ABC transporter; long-distance signal; tZ-type cytokinin translocation