Joohyun Kang1,2, Sojeong Yim2, Hyunju Choi2, Areum Kim2, Keun Pyo Lee3, Luis Lopez-Molina3,*, Enrico Martinoia1,2,* & Youngsook Lee2,4,*
1 Institut für Pflanzenbiologie, Universität Zürich, Zollikerstrasse 107, 8008 Zürich, Switzerland. 2 POSTECH-UZH Global Research Laboratory, Division of Molecular Life Sciences, Pohang University of Science and Technology, Pohang 790-784, Korea. 3 Départment de Biologie Végétale, Université de Genève, 1211 Geneva 4, Switzerland. 4 Division of Integrative Biology and Biotechnology, POSTECH, Pohang 790-784, Korea.
* These authors contributed equally to this work.
Correspondence to : Youngsook Lee
Abstract
Seed germination is a key developmental process that has to be tightly controlled to avoid germination under unfavourable conditions. Abscisic acid (ABA) is an essential repressor of seed germination. In Arabidopsis, it has been shown that the endosperm, a single cell layer surrounding the embryo, synthesizes and continuously releases ABA towards the embryo. The mechanism of ABA transport from the endosperm to the embryo was hitherto unknown. Here we show that four AtABCG transporters act in concert to deliver ABA from the endosperm to the embryo: AtABCG25 and AtABCG31 export ABA from the endosperm, whereas AtABCG30 and AtABCG40 import ABA into the embryo. Thus, this work establishes that radicle extension and subsequent embryonic growth are suppressed by the coordinated activity of multiple ABA transporters expressed in different tissues.