Abscisic acid transporters cooperate to control seed germination.

Joohyun Kang,Keun Pyo Lee,Enrico Martinoia,Areum Kim,Sojeong Yim,Youngsook Lee,Hyunju Choi,Luis Lopez-Molina

doi:10.1038/ncomms9113

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.

Highlights

Seed germination is a key developmental process that has to be tightly controlled to avoid germination under unfavourable conditions
Our analysis of multiple lines of promoter–bglucuronidase-expressing plants (Fig. 2g and Supplementary Fig. 2a) confirmed the quantitative reverse transcription–PCR (qRT–PCR) results; the AtABCG31 promoter was active only in the endosperm layer, and bglucuronidase activity driven by the AtABCG30 and AtABCG40 promoters was observed in dissected embryos, but not in the endosperm. These results show that AtABCG31 and AtABCG25 expression is specific to the endosperm, where their protein products may act as Abscisic acid (ABA) efflux transporters
We evaluated the growth of atabcg[30] (g30), atabcg[40] (g40) and g30/g40 embryos in seed coat bedding assay (SCBA) using seed coats isolated from the highly dormant Cape Verde Island (Cvi) ecotype, which were previously shown to efficiently block wild-type embryonic growth in SCBAs32

Summary

Introduction

Seed germination is a key developmental process that has to be tightly controlled to avoid germination under unfavourable conditions. The germination of non-stratified, freshly collected atabcg[25] seeds was similar to that of wild-type seeds (Fig. 1b,e), even when grown on medium containing exogenous ABA (Supplementary Fig. 1f).

Results

Conclusion