Journal Article

Endosperm-limited Brassicaceae Seed Germination: Abscisic Acid Inhibits Embryo-induced Endosperm Weakening of <i>Lepidium sativum</i> (cress) and Endosperm Rupture of Cress and <i>Arabidopsis thaliana</i>

Kerstin Müller, Stefanie Tintelnot and Gerhard Leubner-Metzger

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 47, issue 7, pages 864-877
Published in print July 2006 | ISSN: 0032-0781
Published online July 2006 | e-ISSN: 1471-9053 | DOI: https://dx.doi.org/10.1093/pcp/pcj059
Endosperm-limited Brassicaceae Seed Germination: Abscisic Acid Inhibits Embryo-induced Endosperm Weakening of Lepidium sativum (cress) and Endosperm Rupture of Cress and Arabidopsis thaliana

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The endosperm is a barrier for radicle protrusion of many angiosperm seeds. Rupture of the testa (seed coat) and rupture of the endosperm are two sequential events during the germination of Lepidium sativum L. and Arabidopsis thaliana (L.) Heyhn. Abscisic acid (ABA) specifically inhibits the endosperm rupture of these two closely related Brassicaceae species. Lepidium seeds are large enough to allow the direct measurement of endosperm weakening by the puncture force method. We found that the endosperm weakens prior to endosperm rupture and that ABA delays the onset and decreases the rate of this weakening process in a dose-dependent manner. An early embryo signal is required and sufficient to induce endosperm weakening, which afterwards appears to be an organ-autonomous process. Gibberellins can replace this embryo signal; de novo gibberellin biosynthesis occurs in the endosperm and weakening is regulated by the gibberellin/ABA ratio. Our results suggest that the control of radicle protrusion during the germination of Brassicaceae seeds is mediated, at least in part, by endosperm weakening. We propose that Lepidium is an emerging Brassicaceae model system for endosperm weakening and that the complementary advantages of Lepidium and Arabidopsis can be used in parallel experiments to investigate the molecular mechanisms of endosperm weakening.

Keywords: ABA; Arabidopsis thaliana; Embryo signal; Endosperm weakening; Gibberellin; Lepidium sativum

Journal Article.  7390 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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